Knowledge

Adjoint functors

Source πŸ“

3531: 2853: 16497: 11830: 5171: 11336: 11319: 16744: 16764: 16754: 4284: 15139: 11825:{\displaystyle {\begin{aligned}f=\Phi _{Y,X}^{-1}(g)&=\varepsilon _{X}\circ F(g)&\in &\,\,\mathrm {hom} _{C}(F(Y),X)\\g=\Phi _{Y,X}(f)&=G(f)\circ \eta _{Y}&\in &\,\,\mathrm {hom} _{D}(Y,G(X))\\\Phi _{GX,X}^{-1}(1_{GX})&=\varepsilon _{X}&\in &\,\,\mathrm {hom} _{C}(FG(X),X)\\\Phi _{Y,FY}(1_{FY})&=\eta _{Y}&\in &\,\,\mathrm {hom} _{D}(Y,GF(Y))\\\end{aligned}}} 7367:, by formally adding an additive inverse for each bundle (or equivalence class). Alternatively one can observe that the functor that for each group takes the underlying monoid (ignoring inverses) has a left adjoint. This is a once-for-all construction, in line with the third section discussion above. That is, one can imitate the construction of 13303: 13085: 6465:. Any limit functor is right adjoint to a corresponding diagonal functor (provided the category has the type of limits in question), and the counit of the adjunction provides the defining maps from the limit object (i.e. from the diagonal functor on the limit, in the functor category). Below are some specific examples. 14740: 2314:
The equivalency of these definitions is quite useful. Adjoint functors arise everywhere, in all areas of mathematics. Since the structure in any of these definitions gives rise to the structures in the others, switching between them makes implicit use of many details that would otherwise have to be
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Common mathematical constructions are very often adjoint functors. Consequently, general theorems about left/right adjoint functors encode the details of many useful and otherwise non-trivial results. Such general theorems include the equivalence of the various definitions of adjoint functors, the
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A similar argument allows one to construct a hom-set adjunction from the terminal morphisms to a left adjoint functor. (The construction that starts with a right adjoint is slightly more common, since the right adjoint in many adjoint pairs is a trivially defined inclusion or forgetful functor.)
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This definition is a logical compromise in that it is more difficult to satisfy than the universal morphism definitions, and has fewer immediate implications than the counit–unit definition. It is useful because of its obvious symmetry, and as a stepping-stone between the other definitions.
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These definitions via universal morphisms are often useful for establishing that a given functor is left or right adjoint, because they are minimalistic in their requirements. They are also intuitively meaningful in that finding a universal morphism is like solving an optimization problem.
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is fully determined by its action on generators, another restatement of the universal property of free groups. One can verify directly that this correspondence is a natural transformation, which means it is a hom-set adjunction for the pair
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A suitable variation of this example also shows that the kernel functors for vector spaces and for modules are right adjoints. Analogously, one can show that the cokernel functors for abelian groups, vector spaces and modules are left
415: 13531: 8569:, quantifiers are identified with adjoints to the pullback functor. Such a realization can be seen in analogy to the discussion of propositional logic using set theory but the general definition make for a richer range of logics. 2299:
The definitions via universal morphisms are easy to state, and require minimal verifications when constructing an adjoint functor or proving two functors are adjoint. They are also the most analogous to our intuition involving
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However, universal constructions are more general than adjoint functors: a universal construction is like an optimization problem; it gives rise to an adjoint pair if and only if this problem has a solution for every object of
14621: 4656: 4589: 608: 535: 10093: 4125: 10305: 15134:{\displaystyle {\begin{aligned}&1_{\mathcal {E}}{\xrightarrow {\eta '}}G'F'{\xrightarrow {G'\eta F'}}G'GFF'\\&FF'G'G{\xrightarrow {F\varepsilon 'G}}FG{\xrightarrow {\varepsilon }}1_{\mathcal {C}}.\end{aligned}}} 13724: 10189: 8401: 6755:, which expresses the universal property of kernels. The counit of this adjunction is the defining embedding of a homomorphism's kernel into the homomorphism's domain, and the unit is the morphism identifying a group 4007: 9458: 11843: 4909: 2985: 784: 718: 8687: 3663: 14239: 14138: 8211: 221: 181: 1827: 13863: 1056:, and indeed every equivalence is an adjunction. In many situations, an adjunction can be "upgraded" to an equivalence, by a suitable natural modification of the involved categories and functors. 10970: 14945: 14626: 13868: 13804: 13611: 13136: 12918: 12744: 11848: 11341: 4914: 4799: 4424: 1346: 15702: 12739: 9579: 10879: 4419: 3530: 6208: 5938: 4794: 13405: 5887: 4746: 2398:). If the arrows for the left adjoint functor F were drawn they would be pointing to the left; if the arrows for the right adjoint functor G were drawn they would be pointing to the right. 14869: 1678: 1621: 10925: 6592:
etc. follow the same pattern; it can also be extended in a straightforward manner to more than just two factors. More generally, any type of limit is right adjoint to a diagonal functor.
15757: 10998: 2670: 69:. Pairs of adjoint functors are ubiquitous in mathematics and often arise from constructions of "optimal solutions" to certain problems (i.e., constructions of objects having a certain 5782: 5671: 5220: 2840: 8072: 10819: 14921: 13298:{\displaystyle {\begin{aligned}\Phi \Psi g&=G(\varepsilon _{X})\circ GF(g)\circ \eta _{Y}\\&=G(\varepsilon _{X})\circ \eta _{GX}\circ g\\&=1_{GX}\circ g=g\end{aligned}}} 13080:{\displaystyle {\begin{aligned}\Psi \Phi f&=\varepsilon _{X}\circ FG(f)\circ F(\eta _{Y})\\&=f\circ \varepsilon _{FY}\circ F(\eta _{Y})\\&=f\circ 1_{FY}=f\end{aligned}}} 3355: 5721: 3525: 9106: 9057: 8222:
in predicate logics is in forming propositions and also in expressing sophisticated predicates by closing formulas with possibly more variables. For example, consider a predicate
6973:-bilinear product with (r,0)(0,1) = (0,1)(r,0) = (r,0), (r,0)(s,0) = (rs,0), (0,1)(0,1) = (0,1). This constructs a left adjoint to the functor taking a ring to the underlying rng. 6397: 5589: 5524: 15803: 9730: 9271: 6141: 1094: 5076: 2310:
The definition via counit–unit adjunction is convenient for proofs about functors that are known to be adjoint, because they provide formulas that can be directly manipulated.
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be the category of pointed commutative rings with unity (pairs (A,a) where A is a ring, a ∈ A and morphisms preserve the distinguished elements). The forgetful functor G:
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The twin fact in probability can be understood as an adjunction: that expectation commutes with affine transform, and that the expectation is in some sense the best
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may exhibit, intuitively corresponding to a weak form of equivalence between two related categories. Two functors that stand in this relationship are known as
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There are hence numerous functors and natural transformations associated with every adjunction, and only a small portion is sufficient to determine the rest.
6535:. The universal property of the product group shows that Ξ  is right-adjoint to Ξ”. The counit of this adjunction is the defining pair of projection maps from 14735:{\displaystyle {\begin{aligned}\eta '&=(\tau \ast \sigma )\circ \eta \\\varepsilon '&=\varepsilon \circ (\sigma ^{-1}\ast \tau ^{-1}).\end{aligned}}} 13418: 5379:. That is, however, something particular to the case of tensor product. In category theory the 'naturality' of the bijection is subsumed in the concept of a 2339:
that are under consideration. Therefore it can be helpful to choose letters in alphabetical order according to whether they live in the "lefthand" category
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that is known as soberification. Notably, the article also contains a detailed description of another adjunction that prepares the way for the famous
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and 1 is an identity element. This construction gives a functor that is a left adjoint to the functor taking a monoid to the underlying semigroup.
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Every monad arises from some adjunctionβ€”in fact, typically from many adjunctionsβ€”in the above fashion. Two constructions, called the category of
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Note: The use of the prefix "co" in counit here is not consistent with the terminology of limits and colimits, because a colimit satisfies an
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is also formulaic in this construction, since it is always the category of elements of the functor to which one is constructing an adjoint.
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to rings. This functor is left adjoint to the functor that associates to a given ring its underlying multiplicative monoid. Similarly, the
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way is to adjoin an element '1' to the rng, adjoin all (and only) the elements that are necessary for satisfying the ring axioms (e.g.
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is given by the direct image. Here is a characterization of this result, which matches more the logical interpretation: The image of
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In particular, the equations above allow one to define Ξ¦, Ξ΅, and Ξ· in terms of any one of the three. However, the adjoint functors
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One can also verify directly that Ξ΅ and Ξ· are natural. Then, a direct verification that they form a counit–unit adjunction  
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then it is the left adjoint in an adjoint equivalence of categories, i.e. an adjunction whose unit and counit are isomorphisms.
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These equations are useful in reducing proofs about adjoint functors to algebraic manipulations. They are sometimes called the
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can be viewed as a category (where the elements of the poset become the category's objects and we have a single morphism from
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in the ring), and impose no relations in the newly formed ring that are not forced by axioms. Moreover, this construction is
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alone are in general not sufficient to determine the adjunction. The equivalence of these situations is demonstrated below.
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Since many common constructions in mathematics are limits or colimits, this provides a wealth of information. For example:
14256: 12864:{\displaystyle {\begin{aligned}\Phi _{Y,X}(f)=G(f)\circ \eta _{Y}\\\Psi _{Y,X}(g)=\varepsilon _{X}\circ F(g)\end{aligned}}} 10930: 13737: 13544: 4500:{\displaystyle {\begin{aligned}\varepsilon &:FG\to 1_{\mathcal {C}}\\\eta &:1_{\mathcal {D}}\to GF\end{aligned}}} 1296: 15667: 14294: 9505: 8020:
is a unary predicate expressing some property, then a sufficiently strong set theory may prove the existence of the set
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uniqueness of a right adjoint for a given left adjoint, the fact that left/right adjoint functors respectively preserve
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This is rather vague, though suggestive, and can be made precise in the language of category theory: a construction is
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it corresponds to (so this map is "dropping parentheses"). The composition of these maps is indeed the identity on
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The commuting diagram of that factorization implies the commuting diagram of natural transformations, so Ξ· : 1
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The most important property of adjoints is their continuity: every functor that has a left adjoint (and therefore
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The partial order case collapses the adjunction definitions quite noticeably, but can provide several themes:
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are two extremal solutions to the problem of constructing an adjunction that gives rise to a given monad.
9062: 9042: 1196:{\displaystyle \varphi _{XY}:\mathrm {hom} _{\mathcal {C}}(FY,X)\cong \mathrm {hom} _{\mathcal {D}}(Y,GX)} 16767: 16707: 15840: 6366: 5363:. It can be seen to be natural on the basis, firstly, that these are two alternative descriptions of the 16416: 15387:{\displaystyle \Phi _{Y,X}:\mathrm {hom} _{\mathcal {C}}(FY,X)\cong \mathrm {hom} _{\mathcal {D}}(Y,GX)} 5549: 5484: 1921:. Universal properties come in two types: initial properties and terminal properties. Since these are 16866: 16757: 16543: 16407: 16315: 15768: 14880: 9690: 9231: 7314: 6450: 6116: 6438:
have generally the same description as in the detailed description of the free group situation above.
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it corresponds to ("dropping parentheses"). The composition of these maps is indeed the identity on
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The definition via hom-sets makes symmetry the most apparent, and is the reason for using the word
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yet; it is an important and not altogether trivial algebraic fact that such a left adjoint functor
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The idea of using an initial property is to set up the problem in terms of some auxiliary category
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that associates to every topological space its underlying set (forgetting the topology, that is).
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adjunctions may not be dualities or isomorphisms, but are candidates for upgrading to that status
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As is the case for Galois groups, the real interest lies often in refining a correspondence to a
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is a ring map (which preserves the identity). (Note that this is precisely the definition of the
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The right adjoint to the inverse image functor is given (without doing the computation here) by
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multiplication, but in situations where this is not possible, we often attempt to construct an
7844: 7394: 6306:{\displaystyle GX{\xrightarrow {\;\eta _{GX}\;}}GFGX{\xrightarrow {\;G(\varepsilon _{X})\,}}GX} 6035:{\displaystyle FY{\xrightarrow {\;F(\eta _{Y})\;}}FGFY{\xrightarrow {\;\varepsilon _{FY}\,}}FY} 4751: 4411: 3668: 2990: 2382:, and whenever possible such things will be referred to in order from left to right (a functor 1922: 1351: 930: 421: 15934: 14451: 10470: 10450: 9380:{\displaystyle {\operatorname {Hom} }(\exists _{f}S,T)\cong {\operatorname {Hom} }(S,f^{*}T),} 8597: 3561: 3094: 2883: 2409: 1209: 16881: 16392: 16231: 12664: 11047: 10511:
to the problem of finding a real-valued approximation to a distribution on the real numbers.
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In a sense, then, adjoints are "generalized" inverses. Note however that a right inverse of
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hence ΦΨ is the identity transformation. Thus Φ is a natural isomorphism with inverse Φ = Ψ.
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which assigns to a category its set of connected components is left-adjoint to the functor
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they correspond to, which exists by the universal property of free groups. Then each  
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in the category theoretical sense); every functor that has a right adjoint (and therefore
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The existence of the unit, a universal morphism, can prove the existence of an adjunction.
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and uncurrying; in many special cases, they are also continuous and form a homeomorphism.
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in 1958. Like many of the concepts in category theory, it was suggested by the needs of
4277: 3906: 2846: 2014: 464:. Naturality here means that there are natural isomorphisms between the pair of functors 15942: 16402: 16397: 16379: 16261: 16236: 15913: 15865: 15450: 15213: 14502: 14351: 13526:{\displaystyle \varepsilon _{X}=\Phi _{GX,X}^{-1}(1_{GX})\in \mathrm {hom} _{C}(FGX,X)} 12022: 11994: 10583: 10430: 10410: 10364: 10344: 9941: 9844: 9797: 9211: 9191: 9171: 9151: 9131: 9111: 9014: 8961: 8941: 8720: 8700: 8577: 8450: 8430: 8410: 8292: 8272: 8252: 8219: 8123: 8103: 7673: 7664:
describes an adjunction between the category of topological spaces and the category of
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Since there is also a natural way to define an identity adjunction between a category
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and to inverse order-preserving bijections between the corresponding closed elements.
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as "affine functions evaluated at a distribution". That is, for any affine function
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The vertical arrows in this diagram are those induced by composition. Formally, Hom(
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at its foundation, and there are many components that live in one of two categories
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solutionβ€”means something rigorous and recognisable, rather like the attainment of a
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over the inclusion of unitary rings into rng.) The existence of a morphism between
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which defines families of initial and terminal morphisms, in the following steps:
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This gives the intuition behind the fact that adjoint functors occur in pairs: if
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can have more adjoined elements and/or more relations not imposed by axioms than
603:{\displaystyle {\mathcal {D}}(-,GX):{\mathcal {D}}\to \mathrm {Set^{\text{op}}} } 530:{\displaystyle {\mathcal {C}}(F-,X):{\mathcal {D}}\to \mathrm {Set^{\text{op}}} } 46: 10088:{\displaystyle \exists _{f}S=\{y\in Y\mid \exists (x\in f^{-1}).\,x\in S\;\}=f.} 7924:
form an adjoint pair. The unit and counit are natural isomorphisms in this case.
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into the direct sum, and the counit is the additive map from the direct sum of (
4120:{\displaystyle \Phi _{Y,X}:\mathrm {hom} _{C}(FY,X)\to \mathrm {hom} _{D}(Y,GX)} 16886: 16621: 16616: 16600: 16563: 16553: 16473: 16004: 15156: 14286: 10447:. Note how the predicate determining the set is the same as above, except that 7856: 7651: 7578: 7431: 7322: 7217: 7056: 6992: 5332: 5187: 2062: 1933: 15428:), then any pair of adjoint functors between them are automatically additive. 10300:{\displaystyle \forall _{f}S=\{y\in Y\mid \forall (x\in f^{-1}).\,x\in S\;\}.} 7291:
has a left adjoint – it assigns to every ring R the pair (R,x) where R is the
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closure operators may indicate the presence of adjunctions, as corresponding
7714: 7705:). A pair of adjoint functors between two partially ordered sets is called a 7661: 7521: 7360: 7348: 6952: 5298: 1879: 1727: 6434:, which assigns to an algebraic object its underlying set. These algebraic 5170: 1882:(which is like a ring that might not have a multiplicative identity) into a 16365: 16266: 15762:
is just the unit Ξ· of the adjunction and the multiplication transformation
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The naturality of Ξ¦ implies the naturality of Ξ΅ and Ξ·, and the two formulas
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Galois connection). See that article for a number of examples: the case of
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An analogous statement characterizes those functors with a right adjoint.
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Baez, John C. (1996). "Higher-Dimensional Algebra II: 2-Hilbert Spaces".
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instead of the category of rings, to get the monoid and group rings over
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This example was discussed in the motivation section above. Given a rng
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is naturally isomorphic to the space of homotopy classes of maps from
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from fields has a left adjointβ€”it assigns to every integral domain its
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to rings, left adjoint to the functor that assigns to a given ring its
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Relationship between two functors abstracting many common constructions
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the power set of the set of all mathematical structures. For a theory
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order isomorphism). A treatment of Galois theory along these lines by
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which assigns to a set the discrete category on that set. Moreover,
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Adjunctions can be composed in a natural fashion. Specifically, if γ€ˆ
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The transformations Ξ¦ and Ξ¨ are natural because Ξ· and Ξ΅ are natural.
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of integral domains with injective morphisms. The forgetful functor
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in the sense that it works in essentially the same way for any rng.
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where it looks like the insertion of the identity 1 into a monoid.
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has an identity and considering it simply as a rng, so essentially
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was influential in the recognition of the general structure here.
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is the free group generated freely by the words of the free group
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in one of the two simple ways that make the compositions defined.
16809: 16691: 16681: 16330: 16241: 16105: 15829: 14297:
and a certain smallness condition is satisfied: for every object
11092: 4384: 3877: 3863: 1918: 1077: 54: 16778: 15528:, Ξ΅, η〉 extends an equivalence of certain subcategories. Define 15461:. Conversely, if there exists a universal morphism to a functor 12051: 8796:. If this functor has a left- or right adjoint, they are called 7717:
of course is a leading one. Any Galois connection gives rise to
2980:{\displaystyle \epsilon _{X}\circ F(G(f))=f\circ \epsilon _{X'}} 16686: 15155:
and itself, one can then form a category whose objects are all
13098:
is a functor, that Ξ· is natural, and the counit–unit equation 1
12882:
is a functor, that Ξ΅ is natural, and the counit–unit equation 1
7946:
which assigns to each category its set of objects, and finally
7205: 6988: 2347:, and also to write them down in this order whenever possible. 2295:
There are various equivalent definitions for adjoint functors:
2256:
is, in a certain rigorous sense, equivalent to the notion that
2162:
denote the above process of adjoining an identity to a rng, so
1643:
a right adjoint because it is applied to the right argument of
15212:
every right adjoint functor between two abelian categories is
13311: 7954:
which assigns to each set the indiscrete category on that set.
5673:  be the group homomorphism that sends the generators of 2378:, Ξ· will consistently denote things that live in the category 2362:, Ξ΅ will consistently denote things that live in the category 16568: 15219:
every left adjoint functor between two abelian categories is
14934:
with unit and counit given respectively by the compositions:
14765:
denotes vertical composition of natural transformations, and
9767:. We conclude that left adjoint to the inverse image functor 7769:
to be the set of all logical theories (axiomatizations), and
6355:  is the "inclusion of generators" set map from the set 5129:
denotes the identity natural transformation from the functor
2154:
can be expressed simultaneously by saying that it defines an
2146:
The two facts that this method of turning rngs into rings is
1586:
a left adjoint because it is applied to the left argument of
1503:
may have itself a right adjoint that is quite different from
11329:
The transformations Ξ΅, Ξ·, and Ξ¦ are related by the equations
8494:-related, and which itself is characterized by the property 7347:, the point of departure is to observe that the category of 6422: 16003:
AdΓ‘mek, JiΕ™Γ­; Herrlich, Horst; Strecker, George E. (1990).
9912:
is non-empty. This works because it neglects exactly those
9302:, let us figure out the left adjoint, which is defined via 6961:, a multiplicative identity element can be added by taking 3091:
Similarly, we may define right-adjoint functors. A functor
14480:
is a functor between locally presentable categories, then
14234:{\displaystyle 1_{GX}=G(\varepsilon _{X})\circ \eta _{GX}} 14171:
in the first formula gives the second counit–unit equation
14133:{\displaystyle 1_{FY}=\varepsilon _{FY}\circ F(\eta _{Y})} 14068:
in the second formula gives the first counit–unit equation
11836:
The transformations Ξ΅, Ξ· satisfy the counit–unit equations
9168:
is characterized as the largest set which knows all about
8206:{\displaystyle \phi _{T}(y)=\phi _{Y}(y)\land \varphi (y)} 216:{\displaystyle G:{\mathcal {C}}\rightarrow {\mathcal {D}}} 176:{\displaystyle F:{\mathcal {D}}\rightarrow {\mathcal {C}}} 15397:
are, in fact, isomorphisms of abelian groups. Dually, if
7976:
has a right adjoint –. This pair is often referred to as
1822:{\displaystyle \langle Ty,x\rangle =\langle y,Ux\rangle } 15945:, which also attribute the concept to the article cited. 7650:. Here a more subtle point is that the left adjoint for 4366: 3658:{\displaystyle G(F(g))\circ \eta _{Y}=\eta _{Y'}\circ g} 2394:
can be thought of as "living" where its outputs are, in
1932:, so that the problem at hand corresponds to finding an 15604:
and yield inverse equivalences of these subcategories.
15276:
is also an additive functor and the hom-set bijections
7789:) be the set of all structures that satisfy the axioms 16002: 14580:, Ξ΅, η〉 is an adjunction (with counit–unit (Ξ΅,Ξ·)) and 6724:
be the functor which assigns to each homomorphism its
4704:, and may indicate this relationship by writing   1925:
notions, it is only necessary to discuss one of them.
1866:
In a sense, an adjoint functor is a way of giving the
15771: 15724: 15670: 15285: 14943: 14883: 14834: 14771: 14751: 14624: 14454: 14179: 14078: 13866: 13809:
The bijectivity and naturality of Ξ¦ imply that each (
13740: 13622: 13547: 13421: 13369: 13134: 12916: 12742: 12667: 11846: 11339: 11050: 11028: 11006: 10978: 10965:{\displaystyle \mathbb {E} :\mu \mapsto \mathbb {E} } 10933: 10894: 10827: 10790: 10746: 10715: 10693: 10662: 10606: 10586: 10542: 10520: 10473: 10453: 10433: 10413: 10387: 10367: 10347: 10317: 10202: 10105: 9975: 9944: 9918: 9867: 9847: 9820: 9800: 9773: 9738: 9693: 9658: 9613: 9587: 9508: 9473: 9399: 9310: 9282: 9234: 9214: 9194: 9174: 9154: 9134: 9114: 9065: 9045: 9017: 8984: 8964: 8944: 8918: 8887: 8856: 8829: 8802: 8769: 8743: 8723: 8703: 8634: 8600: 8580: 8547: 8527: 8500: 8473: 8453: 8433: 8413: 8317: 8295: 8275: 8255: 8228: 8146: 8126: 8106: 8080: 8026: 7999: 7003: 6369: 6331: 6224: 6171: 6119: 6059: 5953: 5901: 5851: 5745: 5687: 5634: 5552: 5487: 5311: 5196: 5139: 5108: 5084: 5055: 4912: 4797: 4754: 4710: 4598: 4531: 4422: 4234:. Explicitly, the naturality of Ξ¦ means that for all 4022: 3917: 3835: 3815: 3795: 3775: 3752: 3728: 3708: 3671: 3596: 3564: 3544: 3485: 3444: 3403: 3383: 3363: 3306: 3286: 3257: 3237: 3217: 3197: 3177: 3153: 3133: 3097: 3074: 3050: 3030: 2993: 2918: 2886: 2866: 2800: 2759: 2718: 2698: 2678: 2621: 2601: 2572: 2552: 2532: 2512: 2492: 2468: 2448: 2412: 2401: 1861: 1779: 1759: 1739: 1700: 1649: 1629: 1592: 1572: 1552: 1532: 1509: 1489: 1469: 1445: 1425: 1401: 1381: 1354: 1299: 1279: 1258: 1238: 1212: 1097: 1038: 1014: 986: 962: 933: 912: 886: 865: 839: 812: 792: 726: 660: 636: 616: 543: 470: 450: 430: 327: 296: 276: 252: 232: 189: 149: 118: 94: 15441:
As stated earlier, an adjunction between categories
11262:
such that the diagrams below commute, and for every
8541:
of two sets directly corresponds to the conjunction
8074:
of terms that fulfill the property. A proper subset
6848:
is the functor which assigns to every abelian group
3856: 2224: 1088:
makes a distinction between the two. Given a family
13799:{\displaystyle 1_{FY}\in \mathrm {hom} _{C}(FY,FY)} 13606:{\displaystyle 1_{GX}\in \mathrm {hom} _{D}(GX,GX)} 12276:
on morphisms preserves compositions and identities.
5731:, because any group homomorphism from a free group 5237:property whereas the counit morphisms will satisfy 1341:{\displaystyle \mathrm {hom} _{\mathcal {C}}(FY,X)} 15797: 15751: 15697:{\displaystyle T:{\mathcal {D}}\to {\mathcal {D}}} 15696: 15386: 15133: 14915: 14863: 14777: 14757: 14734: 14472: 14233: 14132: 13995: 13798: 13718: 13605: 13525: 13399: 13297: 13079: 12863: 12673: 11971: 11824: 11056: 11036: 11014: 10992: 10964: 10919: 10873: 10813: 10776: 10732: 10701: 10679: 10645: 10592: 10572: 10528: 10479: 10459: 10439: 10419: 10399: 10373: 10353: 10333: 10299: 10183: 10087: 9959: 9930: 9904: 9853: 9833: 9806: 9786: 9759: 9724: 9679: 9644: 9599: 9574:{\displaystyle S\subseteq f^{-1}]\subseteq f^{-1}} 9573: 9494: 9452: 9379: 9294: 9265: 9220: 9200: 9180: 9160: 9140: 9120: 9100: 9051: 9023: 9003: 8970: 8950: 8930: 8904: 8873: 8842: 8815: 8788: 8755: 8729: 8709: 8681: 8618: 8586: 8553: 8533: 8513: 8486: 8459: 8439: 8419: 8395: 8301: 8281: 8261: 8241: 8205: 8132: 8112: 8092: 8066: 8012: 7672:of sober spaces and spatial locales, exploited in 7625:from the category of sheaves of abelian groups on 7009: 6391: 6347: 6305: 6202: 6135: 6081: 6034: 5932: 5881: 5776: 5715: 5665: 5583: 5518: 5323: 5214: 5155: 5121: 5094: 5070: 5037: 4876: 4766: 4740: 4650: 4583: 4499: 4119: 4001: 3841: 3821: 3801: 3781: 3758: 3734: 3714: 3694: 3657: 3582: 3550: 3519: 3471: 3430: 3389: 3369: 3349: 3292: 3272: 3243: 3223: 3203: 3183: 3159: 3139: 3115: 3080: 3056: 3036: 3016: 2979: 2904: 2872: 2845:The latter equation is expressed by the following 2834: 2786: 2745: 2704: 2684: 2664: 2607: 2587: 2558: 2538: 2518: 2498: 2474: 2454: 2430: 2209:Note however that we haven't actually constructed 2178:denote the process of β€œforgettingβ€³ whether a ring 1838:The slogan is "Adjoint functors arise everywhere". 1821: 1765: 1745: 1715: 1672: 1635: 1615: 1578: 1558: 1538: 1515: 1495: 1475: 1451: 1431: 1407: 1387: 1363: 1340: 1285: 1264: 1244: 1218: 1195: 1048: 1024: 996: 972: 945: 918: 892: 871: 845: 822: 798: 778: 712: 646: 622: 602: 529: 456: 436: 409: 306: 282: 262: 238: 215: 175: 128: 104: 16006:Abstract and Concrete Categories. The joy of cats 15895:Transactions of the American Mathematical Society 12630:counit–unit adjunction induces hom-set adjunction 10874:{\displaystyle (\mu ,f):\mu \to \mu \circ f^{-1}} 8521:. Set theoretic operations like the intersection 6773: 16899: 8213:expressing a strictly more restrictive property. 7629:to the category of sheaves of abelian groups on 6793:are all examples of the categorical notion of a 6461:are all examples of the categorical notion of a 6045:should be the identity. The intermediate group 88:By definition, an adjunction between categories 16048:. Vol. 5 (2nd ed.). Springer-Verlag. 14926:More precisely, there is an adjunction between 13360:-), one can construct a counit–unit adjunction 10381:'s with the property that the inverse image of 6441: 6203:{\displaystyle 1_{G}=G\varepsilon \circ \eta G} 5933:{\displaystyle 1_{F}=\varepsilon F\circ F\eta } 5257:The idea of adjoint functors was introduced by 5186:because of the appearance of the corresponding 3211:. Spelled out, this means that for each object 2526:. Spelled out, this means that for each object 15209:of objects yields the coproduct of the images; 13400:{\displaystyle (\varepsilon ,\eta ):F\dashv G} 10927:, and the expectation defines another functor 6987:, we can add an identity element and obtain a 6317:should be the identity. The intermediate set 5882:{\displaystyle (\varepsilon ,\eta ):F\dashv G} 4741:{\displaystyle (\varepsilon ,\eta ):F\dashv G} 1870:solution to some problem via a method that is 1832: 16794: 16135: 16100:. Manipulation and visualization of objects, 15496: 15424:(i.e. preadditive categories with all finite 12658:, and a counit–unit adjunction (Ξ΅, Ξ·) : 12052:Universal morphisms induce hom-set adjunction 10709:with finite expectation. Define morphisms on 7607:(of sets, or abelian groups, or rings...) on 5473:is just the underlying set of the free group 5078:denotes the identify functor on the category 3769:It is true, as the terminology implies, that 1983:a ring having a multiplicative identity. The 1673:{\displaystyle \mathrm {hom} _{\mathcal {D}}} 1616:{\displaystyle \mathrm {hom} _{\mathcal {C}}} 1566:has a right adjoint" are equivalent. We call 15202:of objects yields the product of the images; 12281:Construct a natural isomorphism Ξ¦ : hom 10920:{\displaystyle \delta :x\mapsto \delta _{x}} 10394: 10388: 10291: 10268: 10262: 10219: 10178: 10106: 10064: 10041: 10035: 9992: 9890: 9884: 9011:and returns the thereby specified subset of 8390: 8318: 8061: 8033: 7654:will differ from that for sheaves (of sets). 7611:to the corresponding category of sheaves on 7539:be the inclusion functor to the category of 6935:of groups and by the disjoint union of sets. 6563:which define the limit, and the unit is the 5591:  via a unique group homomorphism from 5163:denotes the identity morphism of the object 1816: 1801: 1795: 1780: 15752:{\displaystyle \eta :1_{\mathcal {D}}\to T} 15625:) need not be a right (or left) adjoint of 13312:Hom-set adjunction induces all of the above 11325:From this assertion, one can recover that: 8594:in a category with pullbacks. Any morphism 4777:In equation form, the above conditions on ( 2315:repeated separately in every subject area. 1059: 16801: 16787: 16763: 16753: 16509: 16142: 16128: 15436: 12619:, and then Ξ¦ is natural in both arguments. 12268:Uniqueness of that factorization and that 12184:) is an initial morphism, then factorize Ξ· 10993:{\displaystyle \mathbb {E} \dashv \delta } 10290: 10063: 7408:A functor with a left and a right adjoint. 6480:be the functor that assigns to each pair ( 6273: 6251: 6237: 6008: 5986: 5966: 5814:correspond precisely to maps from the set 4634: 4615: 4608: 4567: 4548: 4541: 2665:{\displaystyle \epsilon _{X}:F(G(X))\to X} 2119:. Therefore, the assertion that an object 30:For the construction in field theory, see 16086:– seven short lectures on adjunctions by 15907: 15869: 15794: 12143:on objects and the family of morphisms Ξ·. 11772: 11771: 11659: 11658: 11541: 11540: 11423: 11422: 11030: 11008: 10980: 10949: 10935: 10804: 10723: 10695: 10687:, the set of probability distribution on 10670: 10522: 10280: 10130: 10053: 8342: 7837:is right adjoint to the "syntax functor" 7563:. The unit of this adjoint pair yields a 7355:has a commutative monoid structure under 7087:is left adjoint to the forgetful functor 6423:Free constructions and forgetful functors 6293: 6105:to the corresponding word of length one ( 6022: 5777:{\displaystyle \varepsilon _{X}:FGX\to X} 5666:{\displaystyle \varepsilon _{X}:FGX\to X} 5215:{\displaystyle 1=\varepsilon \circ \eta } 4641: 4574: 2835:{\displaystyle \epsilon _{X}\circ F(g)=f} 2350:In this article for example, the letters 1874:. For example, an elementary problem in 16041:Categories for the Working Mathematician 16034: 14864:{\displaystyle F\circ F':E\rightarrow C} 14293:has a left adjoint if and only if it is 13089:hence ΨΦ is the identity transformation. 8693:on the category that is the preorder of 8067:{\displaystyle Y=\{y\mid \phi _{Y}(y)\}} 6430:are all examples of a left adjoint to a 5806:Group homomorphisms from the free group 5601:universal property of the free group on 5169: 2856:Here the counit is a universal morphism. 1959:Back to our example: take the given rng 1846:Categories for the Working Mathematician 1082:Categories for the Working Mathematician 1004:is somewhat akin to a "weak form" of an 34:. For the construction in topology, see 13340:, and a hom-set adjunction Ξ¦ : hom 10814:{\displaystyle \mu \in M(\mathbb {R} )} 7793:; for a set of mathematical structures 6604:of homomorphisms of abelian groups. If 2098:is at least as efficient a solution as 420:such that this family of bijections is 77:in algebra, or the construction of the 14: 16900: 15198:applying a right adjoint functor to a 14545:. The same is true for left adjoints. 11067: 10099:Put this in analogy to our motivation 8737:(technically: monomorphism classes of 7942:is left-adjoint to the object functor 7904:, then we have an inverse equivalence 7371:; but there is the other option of an 7128:-module, then the tensor product with 6151:sending each generator to the word of 6143:  is the group homomorphism from 6089:  is the group homomorphism from 5620:is the free group generated freely by 5400:is a common and illuminating example. 4013:This specifies a family of bijections 3558:can be uniquely turned into a functor 3350:{\displaystyle \eta _{Y}:Y\to G(F(Y))} 1944:β€”the sense that the process finds the 16782: 16508: 16161: 16123: 15205:applying a left adjoint functor to a 15162: 15159:and whose morphisms are adjunctions. 14444:An important special case is that of 12272:is a functor implies that the map of 11312:such that the diagrams below commute: 8938:to quantify a relation expressed via 7575:Direct and inverse images of sheaves. 7571:into its Stoneβ€“ΔŒech compactification. 5716:{\displaystyle (GX,\varepsilon _{X})} 5419:be the functor assigning to each set 4367:Definition via counit–unit adjunction 3520:{\displaystyle G(f)\circ \eta _{Y}=g} 2860:In this situation, one can show that 2323:The theory of adjoints has the terms 2290: 318:between the respective morphism sets 136:is a pair of functors (assumed to be 15863: 15649:, Ξ΅, η〉 gives rise to an associated 14817:β€², Ξ΅β€², η′〉 is an adjunction between 14257:Formal criteria for adjoint functors 10361:is characterized as the full set of 9101:{\displaystyle f^{*}T=X\times _{Y}T} 9052:{\displaystyle \operatorname {Set} } 8958:over, the functor/quantifier closes 7984: 7859:is adjoint to the multiplication by 6919:Analogous examples are given by the 6759:with the kernel of the homomorphism 6739:be the functor which maps the group 5245:here is borrowed from the theory of 4518:of the adjunction (terminology from 4208:as functors. In fact, they are both 16149: 15884: 14487:has a right adjoint if and only if 14305:there exists a family of morphisms 12395:is a functor, then for any objects 11177:A natural transformation Ξ· : 1 8850:, respectively. They both map from 7805:) be the minimal axiomatization of 7212:construction yields a functor from 6939: 6902:) of the direct sum to the element 6392:{\displaystyle G(\varepsilon _{X})} 5723:  is a terminal morphism from 4230:). For details, see the article on 24: 15737: 15689: 15679: 15360: 15354: 15351: 15348: 15319: 15313: 15310: 15307: 15287: 15144:This new adjunction is called the 15118: 14955: 14615:β€², Ξ΅β€², η′〉 is an adjunction where 14497:has a left adjoint if and only if 13929: 13872: 13765: 13762: 13759: 13685: 13682: 13679: 13637: 13572: 13569: 13566: 13492: 13489: 13486: 13436: 13142: 13139: 12924: 12921: 12805: 12748: 11781: 11778: 11775: 11710: 11668: 11665: 11662: 11589: 11550: 11547: 11544: 11477: 11432: 11429: 11426: 11351: 11317: 10474: 10454: 10319: 10234: 10204: 10121: 10007: 9977: 9822: 9401: 9320: 8831: 8804: 8333: 7879: 7204:construction gives a functor from 5584:{\displaystyle \eta _{Y}:Y\to GFY} 5519:{\displaystyle \eta _{Y}:Y\to GFY} 5241:properties, and dually. The term 5087: 5062: 4661:are the identity transformations 1 4478: 4452: 4282: 4089: 4086: 4083: 4050: 4047: 4044: 4024: 3971: 3968: 3965: 3932: 3929: 3926: 3918: 3529: 2851: 2402:Definition via universal morphisms 1940:. This has an advantage that the 1862:Solutions to optimization problems 1664: 1658: 1655: 1652: 1607: 1601: 1598: 1595: 1314: 1308: 1305: 1302: 1169: 1163: 1160: 1157: 1128: 1122: 1119: 1116: 1041: 1017: 989: 965: 815: 772: 769: 766: 757: 729: 706: 703: 700: 691: 663: 639: 590: 586: 583: 574: 546: 517: 513: 510: 501: 473: 383: 377: 374: 371: 342: 336: 333: 330: 299: 255: 208: 198: 168: 158: 121: 97: 25: 16919: 16808: 16096:is a category theory package for 16071: 15798:{\displaystyle \mu :T^{2}\to T\,} 14916:{\displaystyle G'\circ G:C\to E.} 14801:, Ξ΅, η〉 is an adjunction between 14501:preserves small limits and is an 11194:An equivalent formulation, where 11022:is the left adjoint, even though 9725:{\displaystyle S\subseteq f^{-1}} 9266:{\displaystyle f^{-1}\subseteq X} 7567:map from every topological space 7301:. Consider the inclusion functor 7198:From monoids and groups to rings. 6136:{\displaystyle \varepsilon _{FY}} 5784:  via a unique set map from 3857:Definition via Hom-set adjunction 2225:Symmetry of optimization problems 956:An adjunction between categories 73:), such as the construction of a 16762: 16752: 16743: 16742: 16495: 16162: 15431: 15401:is additive with a left adjoint 14785:denotes horizontal composition. 13806:  is the identity morphism. 13613:  is the identity morphism. 12334:) is an initial morphism, then Ξ¦ 12084:and a natural transformation Ξ·. 8249:with two open variables of sort 8140:is characterized by a predicate 8100:and the associated injection of 7709:(or, if it is contravariant, an 6210:  says that for each group 5071:{\displaystyle 1_{\mathcal {C}}} 2753:there exists a unique morphism 2241:is the most efficient solution? 654:, and also the pair of functors 15489:(equivalently, every object of 14607:are natural isomorphisms then γ€ˆ 14029:(which completely determine Ξ¦). 12391:Ξ· is a natural transformation, 10733:{\displaystyle M(\mathbb {R} )} 10680:{\displaystyle M(\mathbb {R} )} 10646:{\displaystyle (r,f):r\to f(r)} 9938:which are in the complement of 8912:. Very roughly, given a domain 8905:{\displaystyle {\text{Sub}}(Y)} 8874:{\displaystyle {\text{Sub}}(X)} 7847:is (in general) the attempt to 7391:representation theory of groups 7321:. It has a left adjoint called 6163:The second counit–unit equation 3438:there exists a unique morphism 1726:The terminology comes from the 1206:of hom-set bijections, we call 15966: 15948: 15924: 15878: 15857: 15788: 15743: 15684: 15553:is an isomorphism, and define 15381: 15366: 15340: 15325: 15148:of the two given adjunctions. 14904: 14855: 14788: 14722: 14690: 14656: 14644: 14464: 14446:locally presentable categories 14212: 14199: 14127: 14114: 13986: 13980: 13958: 13952: 13908: 13902: 13893: 13887: 13841:) is an initial morphism from 13819:) is a terminal morphism from 13793: 13775: 13713: 13695: 13671: 13655: 13600: 13582: 13520: 13502: 13478: 13462: 13382: 13370: 13231: 13218: 13189: 13183: 13171: 13158: 13035: 13022: 12984: 12971: 12962: 12956: 12854: 12848: 12826: 12820: 12784: 12778: 12769: 12763: 12095:, choose an initial morphism ( 12056:Given a right adjoint functor 11946: 11933: 11903: 11890: 11815: 11812: 11806: 11791: 11744: 11728: 11702: 11693: 11687: 11678: 11631: 11615: 11581: 11578: 11572: 11560: 11517: 11511: 11498: 11492: 11463: 11454: 11448: 11442: 11412: 11406: 11380: 11374: 10959: 10953: 10945: 10904: 10849: 10840: 10828: 10808: 10800: 10756: 10750: 10727: 10719: 10674: 10666: 10640: 10634: 10628: 10619: 10607: 10552: 10546: 10502: 10274: 10271: 10259: 10237: 10175: 10169: 10153: 10141: 10079: 10073: 10047: 10044: 10032: 10010: 9954: 9948: 9893: 9881: 9748: 9742: 9719: 9713: 9668: 9662: 9639: 9633: 9568: 9562: 9543: 9540: 9534: 9528: 9483: 9477: 9447: 9441: 9419: 9371: 9349: 9338: 9316: 9254: 9248: 8899: 8893: 8868: 8862: 8747: 8676: 8670: 8662: 8659: 8653: 8610: 8387: 8381: 8365: 8353: 8289:. Using a quantifier to close 8200: 8194: 8185: 8179: 8163: 8157: 8058: 8052: 6774:Colimits and diagonal functors 6386: 6373: 6321:is just the underlying set of 6290: 6277: 6076: 6063: 5983: 5970: 5940:  says that for each set 5893:The first counit–unit equation 5864: 5852: 5768: 5710: 5688: 5657: 5569: 5504: 5447:, which assigns to each group 5391: 5347:,–) (this is now known as the 5174:String diagram for adjunction. 5095:{\displaystyle {\mathcal {C}}} 5012: 4999: 4969: 4956: 4723: 4711: 4684:In this situation we say that 4522:), such that the compositions 4484: 4443: 4114: 4099: 4078: 4075: 4060: 3996: 3981: 3960: 3957: 3942: 3681: 3615: 3612: 3606: 3600: 3574: 3495: 3489: 3463: 3460: 3454: 3425: 3419: 3413: 3344: 3341: 3335: 3329: 3323: 3267: 3261: 3107: 3008: 2950: 2947: 2941: 2935: 2896: 2823: 2817: 2781: 2775: 2769: 2737: 2734: 2728: 2656: 2653: 2650: 2644: 2638: 2582: 2576: 2422: 2318: 1335: 1320: 1190: 1175: 1149: 1134: 1049:{\displaystyle {\mathcal {D}}} 1025:{\displaystyle {\mathcal {C}}} 997:{\displaystyle {\mathcal {D}}} 973:{\displaystyle {\mathcal {C}}} 823:{\displaystyle {\mathcal {D}}} 762: 749: 734: 696: 683: 668: 647:{\displaystyle {\mathcal {C}}} 579: 566: 551: 506: 493: 478: 404: 389: 363: 348: 307:{\displaystyle {\mathcal {D}}} 263:{\displaystyle {\mathcal {C}}} 203: 163: 129:{\displaystyle {\mathcal {D}}} 105:{\displaystyle {\mathcal {C}}} 13: 1: 16046:Graduate Texts in Mathematics 15996: 15977:Sheaves in Geometry and Logic 15227: 14508: 14245: 11000:. (Somewhat disconcertingly, 10334:{\displaystyle \forall _{f}S} 9004:{\displaystyle X\times _{Y}T} 8789:{\displaystyle X\times _{Y}T} 7325:which assigns to every group 7227:and consider the category of 6983:Similarly, given a semigroup 6590:product of topological spaces 5427:generated by the elements of 4176:In order to interpret Ξ¦ as a 2880:can be turned into a functor 1523:; see below for an example.) 15619:is naturally isomorphic to 1 15568:consisting of those objects 15539:consisting of those objects 14250: 11037:{\displaystyle \mathbb {E} } 11015:{\displaystyle \mathbb {E} } 10702:{\displaystyle \mathbb {R} } 10529:{\displaystyle \mathbb {R} } 9905:{\displaystyle f^{-1}\cap S} 9834:{\displaystyle \exists _{f}} 9760:{\displaystyle f\subseteq T} 9495:{\displaystyle f\subseteq T} 9295:{\displaystyle S\subseteq X} 9108:of an injection of a subset 8843:{\displaystyle \forall _{f}} 8816:{\displaystyle \exists _{f}} 7621:. It also induces a functor 7514:Stoneβ€“ΔŒech compactification. 7454:Suspensions and loop spaces. 7220:. One can also start with a 6588:, the product of rings, the 6519:that assigns to every group 6442:Diagonal functors and limits 6082:{\displaystyle F(\eta _{Y})} 2672:such that for every object 2343:or the "righthand" category 7: 16437:Constructions on categories 15535:as the full subcategory of 15457:and one for each object in 14560:is naturally isomorphic to 14355:, such that every morphism 12704:-) in the following steps: 10656:Define a category based on 10514:Define a category based on 9645:{\displaystyle x\in f^{-1}} 7561:Stoneβ€“ΔŒech compactification 7401: 6977:Adjoining an identity to a 6951:Adjoining an identity to a 6399:  is the set map from 5534:, because any set map from 5386: 3472:{\displaystyle f:F(Y)\to X} 3431:{\displaystyle g:Y\to G(X)} 3357:such that for every object 2912:in a unique way such that 2787:{\displaystyle g:Y\to G(X)} 2746:{\displaystyle f:F(Y)\to X} 1833:Introduction and Motivation 79:Stoneβ€“ΔŒech compactification 53:is a relationship that two 10: 16924: 16544:Higher-dimensional algebra 15935:Adjointness in foundations 15497:Equivalences of categories 15449:gives rise to a family of 14273:admits a left adjoint. If 14254: 10427:is fully contained within 8931:{\displaystyle S\subset X} 8093:{\displaystyle T\subset Y} 7833:: the "semantics functor" 7757:a very general comment of 7315:category of abelian groups 7186:) for every abelian group 6944: 6832:) of abelian groups their 6531:) in the product category 6348:{\displaystyle \eta _{GX}} 5739:will factor through   5546:will factor through   5451:its underlying set. Then 5324:{\displaystyle -\otimes A} 5252: 3251:, there exists an object 2406:By definition, a functor 1716:{\displaystyle F\dashv G.} 1395:(p. 81). The functor 29: 16817: 16738: 16671: 16635: 16583: 16576: 16527: 16517: 16504: 16493: 16436: 16378: 16329: 16284: 16275: 16172: 16168: 16157: 16012:. John Wiley & Sons. 15636: 15515:equivalence of categories 15453:, one for each object in 10777:{\displaystyle f(x)=ax+b} 10573:{\displaystyle f(x)=ax+b} 9680:{\displaystyle f(x)\in T} 8514:{\displaystyle \phi _{S}} 8487:{\displaystyle \psi _{f}} 8242:{\displaystyle \psi _{f}} 8013:{\displaystyle \phi _{Y}} 7962:cartesian closed category 7902:equivalence of categories 7752:Kuratowski closure axioms 7680: 7295:with coefficients from R. 6682:) of morphisms such that 5822:: each homomorphism from 5599:. This is precisely the 4887:which mean that for each 4767:{\displaystyle F\dashv G} 3695:{\displaystyle g:Y\to Y'} 3017:{\displaystyle f:X'\to X} 2143:solution to our problem. 1526:In general, the phrases " 1364:{\displaystyle \varphi f} 946:{\displaystyle F\dashv G} 32:Adjunction (field theory) 15975:; Moerdijk, Ieke (1992) 15850: 15841:Eilenberg–Moore algebras 15715:. The unit of the monad 15657:, Ξ·, μ〉 in the category 15582:is an isomorphism. Then 14568:is also left adjoint to 14491:preserves small colimits 14473:{\displaystyle F:C\to D} 10972:, and they are adjoint: 10480:{\displaystyle \forall } 10460:{\displaystyle \exists } 9581:. Conversely, If for an 8619:{\displaystyle f:X\to Y} 7928:A series of adjunctions. 7363:out of this monoid, the 7190:, is a right adjoint to 7051:can be seen as a (left) 7035:are rings, and ρ : 5222:and then fill in either 4748: , or simply   4510:respectively called the 3583:{\displaystyle F:D\to C} 3116:{\displaystyle G:C\to D} 2905:{\displaystyle G:C\to D} 2566:there exists an object 2431:{\displaystyle F:D\to C} 2252:to the problem posed by 2158:. More explicitly: Let 1546:is a left adjoint" and " 1219:{\displaystyle \varphi } 1060:Terminology and notation 16354:Cokernels and quotients 16277:Universal constructions 16110:natural transformations 15885:Kan, Daniel M. (1958). 15437:Universal constructions 14572:β€². More generally, if γ€ˆ 14525:has two right adjoints 14283:adjoint functor theorem 12674:{\displaystyle \dashv } 12344:is a bijection, where Ξ¦ 12139:)). We have the map of 11057:{\displaystyle \delta } 7916:, and the two functors 7809:. We can then say that 7506:, an important fact in 7010:{\displaystyle \sqcup } 6818:assigns to every pair ( 6650:, then a morphism from 6097:sending each generator 5843:counit–unit adjunction. 4412:natural transformations 4375:between two categories 3868:between two categories 2250:most efficient solution 2229:It is also possible to 1076:are both used, and are 16852:Essentially surjective 16511:Higher category theory 16257:Natural transformation 15943:in these lecture notes 15816:. Dually, the triple γ€ˆ 15799: 15753: 15698: 15629:. Adjoints generalize 15388: 15242:preadditive categories 15135: 14917: 14865: 14779: 14759: 14758:{\displaystyle \circ } 14736: 14474: 14235: 14134: 13997: 13800: 13720: 13607: 13527: 13401: 13299: 13081: 12878:Using, in order, that 12865: 12675: 12263:natural transformation 12238:). This is the map of 11973: 11826: 11322: 11206:denotes any object of 11198:denotes any object of 11159:natural transformation 11058: 11038: 11016: 10994: 10966: 10921: 10875: 10815: 10778: 10734: 10703: 10681: 10647: 10594: 10574: 10530: 10481: 10461: 10441: 10421: 10401: 10375: 10355: 10335: 10301: 10185: 10089: 9961: 9932: 9931:{\displaystyle y\in Y} 9906: 9855: 9835: 9808: 9788: 9761: 9726: 9681: 9646: 9601: 9600:{\displaystyle x\in S} 9575: 9496: 9454: 9391:which here just means 9381: 9296: 9267: 9222: 9202: 9182: 9162: 9142: 9122: 9102: 9053: 9025: 9005: 8972: 8952: 8932: 8906: 8875: 8844: 8817: 8790: 8757: 8756:{\displaystyle T\to Y} 8731: 8711: 8683: 8620: 8588: 8574:So consider an object 8555: 8554:{\displaystyle \land } 8535: 8515: 8488: 8461: 8447:for which there is an 8441: 8421: 8397: 8309:, we can form the set 8303: 8283: 8263: 8243: 8207: 8134: 8114: 8094: 8068: 8014: 7438:, and a right adjoint 7395:induced representation 7341:The Grothendieck group 7245:Consider the category 7011: 6600:Consider the category 6393: 6349: 6307: 6204: 6137: 6083: 6036: 5934: 5889:  is as follows: 5883: 5800:) is an adjoint pair. 5778: 5717: 5667: 5585: 5538:to the underlying set 5520: 5325: 5216: 5175: 5157: 5156:{\displaystyle 1_{FY}} 5123: 5096: 5072: 5039: 4878: 4768: 4742: 4652: 4585: 4501: 4373:counit–unit adjunction 4288: 4276:the following diagram 4121: 4003: 3843: 3823: 3803: 3783: 3760: 3736: 3716: 3696: 3659: 3584: 3552: 3535: 3521: 3473: 3432: 3391: 3371: 3351: 3294: 3274: 3245: 3225: 3205: 3185: 3161: 3141: 3117: 3082: 3058: 3038: 3018: 2981: 2906: 2874: 2857: 2836: 2788: 2747: 2706: 2686: 2666: 2609: 2589: 2560: 2540: 2520: 2500: 2476: 2456: 2432: 2262:most difficult problem 2135:, means that the ring 1971:are rng homomorphisms 1963:, and make a category 1851: 1823: 1767: 1747: 1717: 1674: 1637: 1617: 1580: 1560: 1540: 1517: 1497: 1477: 1453: 1433: 1409: 1389: 1365: 1342: 1287: 1266: 1246: 1220: 1197: 1050: 1026: 998: 974: 947: 920: 894: 873: 847: 824: 800: 780: 714: 648: 624: 604: 531: 458: 438: 411: 308: 284: 264: 240: 217: 177: 130: 106: 15956:"Indiscrete category" 15800: 15754: 15699: 15590:can be restricted to 15473:from every object of 15389: 15260:with a right adjoint 15136: 14918: 14866: 14780: 14778:{\displaystyle \ast } 14760: 14737: 14475: 14236: 14135: 13998: 13801: 13721: 13608: 13528: 13402: 13300: 13082: 12866: 12676: 11974: 11827: 11321: 11059: 11039: 11017: 10995: 10967: 10922: 10876: 10816: 10779: 10735: 10704: 10682: 10648: 10595: 10575: 10531: 10482: 10462: 10442: 10422: 10402: 10400:{\displaystyle \{y\}} 10376: 10356: 10336: 10302: 10186: 10090: 9962: 9933: 9907: 9856: 9836: 9809: 9789: 9787:{\displaystyle f^{*}} 9762: 9727: 9682: 9647: 9602: 9576: 9497: 9455: 9382: 9297: 9268: 9223: 9203: 9188:and the injection of 9183: 9163: 9143: 9123: 9103: 9054: 9026: 9006: 8973: 8953: 8933: 8907: 8876: 8845: 8818: 8791: 8758: 8732: 8712: 8697:. It maps subobjects 8684: 8621: 8589: 8556: 8536: 8534:{\displaystyle \cap } 8516: 8489: 8462: 8442: 8422: 8398: 8304: 8284: 8264: 8244: 8208: 8135: 8115: 8095: 8069: 8015: 7687:partially ordered set 7636:inverse image functor 7603:from the category of 7387:Frobenius reciprocity 7012: 6894:(sending an element ( 6575:(mapping x to (x,x)). 6394: 6350: 6308: 6205: 6138: 6084: 6037: 5935: 5884: 5779: 5718: 5668: 5586: 5521: 5349:tensor-hom adjunction 5326: 5217: 5173: 5158: 5124: 5122:{\displaystyle 1_{F}} 5097: 5073: 5040: 4879: 4787:counit–unit equations 4769: 4743: 4653: 4586: 4502: 4286: 4180:, one must recognize 4122: 4004: 3844: 3824: 3804: 3784: 3761: 3737: 3717: 3697: 3660: 3585: 3553: 3533: 3522: 3474: 3433: 3392: 3372: 3352: 3295: 3275: 3246: 3226: 3206: 3186: 3162: 3142: 3125:right adjoint functor 3118: 3083: 3059: 3039: 3019: 2982: 2907: 2875: 2855: 2837: 2789: 2748: 2707: 2687: 2667: 2610: 2590: 2561: 2541: 2521: 2501: 2477: 2457: 2433: 2015:commutative triangles 1836: 1824: 1768: 1748: 1718: 1675: 1638: 1618: 1581: 1561: 1541: 1518: 1498: 1478: 1454: 1434: 1410: 1390: 1366: 1343: 1288: 1267: 1247: 1221: 1198: 1051: 1027: 999: 975: 948: 921: 902:right adjoint functor 895: 874: 848: 825: 801: 781: 715: 649: 625: 605: 532: 459: 439: 412: 309: 285: 265: 241: 226:and, for all objects 218: 178: 131: 107: 16380:Algebraic categories 16114:universal properties 15769: 15722: 15668: 15481:has a left adjoint. 15283: 15187:(i.e. commutes with 15175:(i.e. commutes with 15171:a right adjoint) is 14941: 14881: 14832: 14769: 14749: 14622: 14543:naturally isomorphic 14452: 14177: 14076: 13864: 13738: 13620: 13545: 13419: 13367: 13132: 12914: 12740: 12665: 12072:Construct a functor 11844: 11337: 11278:, there is a unique 11232:, there is a unique 11048: 11026: 11004: 10976: 10931: 10892: 10825: 10821:, define a morphism 10788: 10744: 10713: 10691: 10660: 10604: 10600:, define a morphism 10584: 10580:and any real number 10540: 10518: 10471: 10451: 10431: 10411: 10385: 10365: 10345: 10315: 10200: 10103: 9973: 9942: 9916: 9865: 9845: 9818: 9798: 9771: 9736: 9691: 9656: 9611: 9585: 9506: 9471: 9397: 9308: 9280: 9232: 9212: 9192: 9172: 9152: 9132: 9112: 9063: 9043: 9015: 8982: 8962: 8942: 8916: 8885: 8854: 8827: 8800: 8767: 8741: 8721: 8701: 8632: 8598: 8578: 8545: 8525: 8498: 8471: 8451: 8431: 8411: 8315: 8293: 8273: 8253: 8226: 8144: 8124: 8104: 8078: 8024: 7997: 7829:) logically implies 7763:syntax and semantics 7618:direct image functor 7414:be the functor from 7202:integral monoid ring 7001: 6751:is right adjoint to 6743:to the homomorphism 6494:) the product group 6367: 6329: 6222: 6169: 6117: 6109:) as a generator of 6057: 5951: 5899: 5849: 5792:. This means that ( 5743: 5685: 5632: 5550: 5485: 5396:The construction of 5343:was the functor hom( 5309: 5194: 5137: 5106: 5082: 5053: 4910: 4795: 4752: 4708: 4699:is right adjoint to 4596: 4529: 4420: 4164:is right adjoint to 4020: 3915: 3833: 3829:is right adjoint to 3813: 3793: 3773: 3750: 3726: 3706: 3669: 3594: 3562: 3542: 3483: 3442: 3401: 3381: 3361: 3304: 3284: 3273:{\displaystyle F(Y)} 3255: 3235: 3215: 3195: 3175: 3151: 3131: 3095: 3072: 3048: 3028: 2991: 2916: 2884: 2864: 2798: 2757: 2716: 2696: 2676: 2619: 2599: 2588:{\displaystyle G(X)} 2570: 2550: 2530: 2510: 2490: 2466: 2446: 2440:left adjoint functor 2410: 2283:is right adjoint to 2200:left adjoint functor 1777: 1757: 1737: 1698: 1647: 1627: 1590: 1570: 1550: 1530: 1507: 1487: 1467: 1443: 1423: 1399: 1379: 1352: 1297: 1277: 1256: 1236: 1210: 1095: 1036: 1012: 984: 960: 931: 910: 884: 863: 855:left adjoint functor 837: 810: 790: 724: 658: 634: 614: 541: 468: 448: 428: 325: 294: 274: 250: 230: 187: 147: 116: 92: 16549:Homotopy hypothesis 16227:Commutative diagram 15979:, Springer-Verlag. 15931:Lawvere, F. William 15451:universal morphisms 15422:additive categories 15183:a left adjoint) is 15109: 15091: 15019: 14975: 14874:is left adjoint to 14552:is left adjoint to 13951: 13461: 13094:Dually, using that 11614: 11373: 11132:natural isomorphism 11079:between categories 11068:Adjunctions in full 11044:is "forgetful" and 10888:defines a functor: 10886:Dirac delta measure 9841:is the full set of 7950:is left-adjoint to 7873:logical conjunction 7869:propositional logic 7643:is left adjoint to 7547:has a left adjoint 7520:be the category of 7426:has a left adjoint 7329:the quotient group 7243:Field of fractions. 7210:integral group ring 6864:is left adjoint to 6646:are two objects of 6508:, and let Ξ” : 6363:. The arrow   6325:. The arrow   6294: 6252: 6113:. The arrow   6023: 5987: 5804:Hom-set adjunction. 5677:to the elements of 5610:Terminal morphisms. 5455:is left adjoint to 5381:natural isomorphism 5297:in the category of 5263:homological algebra 5182:, or sometimes the 5180:triangle identities 4689:is left adjoint to 4642: 4616: 4575: 4549: 4178:natural isomorphism 4154:is left adjoint to 4149:In this situation, 3907:natural isomorphism 3789:is left adjoint to 3397:and every morphism 3127:if for each object 2847:commutative diagram 2712:and every morphism 2442:if for each object 2275:is left adjoint to 1843:Saunders Mac Lane, 1687:is left adjoint to 1232:adjunction between 75:free group on a set 16262:Universal property 16036:Mac Lane, Saunders 15973:Mac Lane, Saunders 15887:"Adjoint Functors" 15795: 15749: 15694: 15641:Every adjunction γ€ˆ 15520:Every adjunction γ€ˆ 15513:is one half of an 15412:Moreover, if both 15409:is also additive. 15384: 15163:Limit preservation 15131: 15129: 14913: 14861: 14775: 14755: 14732: 14730: 14503:accessible functor 14470: 14413:and some morphism 14378:can be written as 14338:where the indices 14261:Not every functor 14231: 14130: 13993: 13991: 13928: 13796: 13716: 13603: 13523: 13435: 13397: 13295: 13293: 13077: 13075: 12861: 12859: 12671: 11969: 11967: 11822: 11820: 11588: 11350: 11323: 11054: 11034: 11012: 10990: 10962: 10917: 10871: 10811: 10774: 10730: 10699: 10677: 10643: 10590: 10570: 10526: 10477: 10457: 10437: 10417: 10397: 10371: 10351: 10331: 10297: 10181: 10085: 9957: 9928: 9902: 9851: 9831: 9804: 9784: 9757: 9722: 9677: 9642: 9597: 9571: 9492: 9450: 9377: 9292: 9263: 9218: 9198: 9178: 9158: 9138: 9118: 9098: 9049: 9021: 9001: 8968: 8948: 8928: 8902: 8871: 8840: 8813: 8786: 8763:) to the pullback 8753: 8727: 8707: 8679: 8626:induces a functor 8616: 8584: 8561:of predicates. In 8551: 8531: 8511: 8484: 8457: 8437: 8417: 8393: 8299: 8279: 8259: 8239: 8203: 8130: 8110: 8090: 8064: 8010: 7958:Exponential object 7765:are adjoint: take 7674:pointless topology 7596:induces a functor 7594:topological spaces 7541:topological spaces 7458:topological spaces 7416:topological spaces 7365:Grothendieck group 7359:. One may make an 7319:category of groups 7265:field of fractions 7007: 6567:of a group X into 6565:diagonal inclusion 6411:to the element of 6389: 6345: 6303: 6200: 6133: 6079: 6032: 5930: 5879: 5774: 5713: 5663: 5624:, the elements of 5581: 5516: 5463:Initial morphisms. 5351:). The use of the 5321: 5212: 5176: 5153: 5119: 5092: 5068: 5035: 5033: 4874: 4872: 4764: 4738: 4648: 4581: 4497: 4495: 4289: 4255:and all morphisms 4117: 3999: 3839: 3819: 3799: 3779: 3756: 3732: 3712: 3692: 3655: 3580: 3548: 3536: 3517: 3469: 3428: 3387: 3367: 3347: 3290: 3270: 3241: 3221: 3201: 3181: 3169:universal morphism 3167:, there exists a 3157: 3137: 3113: 3078: 3054: 3034: 3014: 2987:for all morphisms 2977: 2902: 2870: 2858: 2832: 2784: 2743: 2702: 2682: 2662: 2605: 2585: 2556: 2536: 2516: 2496: 2484:universal morphism 2472: 2452: 2428: 2291:Formal definitions 1911:universal property 1909:if it satisfies a 1819: 1763: 1743: 1713: 1670: 1633: 1613: 1576: 1556: 1536: 1513: 1493: 1473: 1449: 1429: 1405: 1385: 1361: 1338: 1283: 1262: 1242: 1216: 1193: 1046: 1022: 994: 970: 943: 916: 890: 869: 843: 820: 796: 776: 710: 644: 620: 600: 527: 454: 434: 407: 304: 280: 260: 236: 213: 183:  and   173: 126: 102: 71:universal property 65:and the other the 16895: 16894: 16867:Full and faithful 16776: 16775: 16734: 16733: 16730: 16729: 16712:monoidal category 16667: 16666: 16539:Enriched category 16491: 16490: 16487: 16486: 16464:Quotient category 16459:Opposite category 16374: 16373: 15110: 15092: 15020: 14976: 14825:then the functor 14279:complete category 14143:and substituting 13117: 12896: 12615: 12591: 12576: 12564: 12553: 12532: 12517: 12506: 12495: 12489: 12381: 12257: 12195: 11995:terminal morphism 11210:, is as follows: 10593:{\displaystyle r} 10440:{\displaystyle S} 10420:{\displaystyle f} 10374:{\displaystyle y} 10354:{\displaystyle Y} 9960:{\displaystyle f} 9854:{\displaystyle y} 9807:{\displaystyle S} 9221:{\displaystyle Y} 9201:{\displaystyle T} 9181:{\displaystyle f} 9161:{\displaystyle f} 9141:{\displaystyle Y} 9121:{\displaystyle T} 9024:{\displaystyle Y} 8971:{\displaystyle X} 8951:{\displaystyle f} 8891: 8860: 8730:{\displaystyle Y} 8710:{\displaystyle T} 8668: 8651: 8587:{\displaystyle Y} 8563:categorical logic 8460:{\displaystyle x} 8440:{\displaystyle Y} 8420:{\displaystyle y} 8302:{\displaystyle X} 8282:{\displaystyle Y} 8262:{\displaystyle X} 8133:{\displaystyle Y} 8113:{\displaystyle T} 7985:Categorical logic 7821:) if and only if 7719:closure operators 7707:Galois connection 7504:homotopy category 7471:of maps from the 7377:universal algebra 7373:existence theorem 7353:topological space 7132:yields a functor 7063:yields a functor 7055:-module, and the 7045:ring homomorphism 6783:fibred coproducts 6582:cartesian product 6432:forgetful functor 6295: 6253: 6024: 5988: 5445:forgetful functor 5365:bilinear mappings 5357:abuse of notation 5184:zig-zag equations 4643: 4617: 4576: 4550: 4520:universal algebra 4336: 4332: 3842:{\displaystyle F} 3822:{\displaystyle G} 3802:{\displaystyle G} 3782:{\displaystyle F} 3759:{\displaystyle F} 3742:is then called a 3735:{\displaystyle G} 3715:{\displaystyle D} 3551:{\displaystyle F} 3390:{\displaystyle C} 3370:{\displaystyle X} 3293:{\displaystyle C} 3244:{\displaystyle D} 3224:{\displaystyle Y} 3204:{\displaystyle G} 3184:{\displaystyle Y} 3160:{\displaystyle D} 3140:{\displaystyle Y} 3081:{\displaystyle G} 3064:is then called a 3057:{\displaystyle F} 3037:{\displaystyle C} 2873:{\displaystyle G} 2705:{\displaystyle D} 2685:{\displaystyle Y} 2608:{\displaystyle D} 2559:{\displaystyle C} 2539:{\displaystyle X} 2519:{\displaystyle X} 2499:{\displaystyle F} 2475:{\displaystyle C} 2455:{\displaystyle X} 2233:with the functor 2221:actually exists. 1878:is how to turn a 1766:{\displaystyle U} 1746:{\displaystyle T} 1732:adjoint operators 1636:{\displaystyle G} 1579:{\displaystyle F} 1559:{\displaystyle F} 1539:{\displaystyle F} 1516:{\displaystyle F} 1496:{\displaystyle G} 1476:{\displaystyle F} 1452:{\displaystyle G} 1432:{\displaystyle G} 1408:{\displaystyle F} 1388:{\displaystyle f} 1286:{\displaystyle f} 1265:{\displaystyle G} 1245:{\displaystyle F} 919:{\displaystyle F} 906:right adjoint to 893:{\displaystyle G} 872:{\displaystyle G} 846:{\displaystyle F} 799:{\displaystyle Y} 623:{\displaystyle X} 596: 523: 457:{\displaystyle Y} 437:{\displaystyle X} 283:{\displaystyle Y} 239:{\displaystyle X} 83:topological space 16:(Redirected from 16915: 16908:Adjoint functors 16803: 16796: 16789: 16780: 16779: 16766: 16765: 16756: 16755: 16746: 16745: 16581: 16580: 16559:Simplex category 16534:Categorification 16525: 16524: 16506: 16505: 16499: 16469:Product category 16454:Kleisli category 16449:Functor category 16294:Terminal objects 16282: 16281: 16217:Adjoint functors 16170: 16169: 16159: 16158: 16144: 16137: 16130: 16121: 16120: 16080: 16067: 16031: 16011: 15990: 15970: 15964: 15963: 15952: 15946: 15928: 15922: 15921: 15911: 15891: 15882: 15876: 15875: 15873: 15861: 15845:Kleisli category 15808:is given by ΞΌ = 15804: 15802: 15801: 15796: 15787: 15786: 15758: 15756: 15755: 15750: 15742: 15741: 15740: 15703: 15701: 15700: 15695: 15693: 15692: 15683: 15682: 15611:(i.e. a functor 15562:full subcategory 15393: 15391: 15390: 15385: 15365: 15364: 15363: 15357: 15324: 15323: 15322: 15316: 15301: 15300: 15258:additive functor 15157:small categories 15140: 15138: 15137: 15132: 15130: 15123: 15122: 15121: 15111: 15101: 15093: 15087: 15072: 15067: 15059: 15047: 15043: 15029: 15021: 15018: 15007: 14995: 14993: 14985: 14977: 14974: 14962: 14960: 14959: 14958: 14947: 14922: 14920: 14919: 14914: 14891: 14870: 14868: 14867: 14862: 14848: 14784: 14782: 14781: 14776: 14764: 14762: 14761: 14756: 14741: 14739: 14738: 14733: 14731: 14721: 14720: 14705: 14704: 14676: 14636: 14479: 14477: 14476: 14471: 14412: 14348: 14240: 14238: 14237: 14232: 14230: 14229: 14211: 14210: 14192: 14191: 14139: 14137: 14136: 14131: 14126: 14125: 14107: 14106: 14091: 14090: 14002: 14000: 13999: 13994: 13992: 13973: 13972: 13950: 13942: 13923: 13922: 13886: 13885: 13805: 13803: 13802: 13797: 13774: 13773: 13768: 13753: 13752: 13726:  for each 13725: 13723: 13722: 13717: 13694: 13693: 13688: 13670: 13669: 13654: 13653: 13632: 13631: 13612: 13610: 13609: 13604: 13581: 13580: 13575: 13560: 13559: 13533:  for each 13532: 13530: 13529: 13524: 13501: 13500: 13495: 13477: 13476: 13460: 13452: 13431: 13430: 13406: 13404: 13403: 13398: 13304: 13302: 13301: 13296: 13294: 13278: 13277: 13259: 13249: 13248: 13230: 13229: 13208: 13204: 13203: 13170: 13169: 13115: 13086: 13084: 13083: 13078: 13076: 13066: 13065: 13041: 13034: 13033: 13015: 13014: 12990: 12983: 12982: 12946: 12945: 12894: 12870: 12868: 12867: 12862: 12860: 12841: 12840: 12819: 12818: 12799: 12798: 12762: 12761: 12680: 12678: 12677: 12672: 12613: 12589: 12574: 12562: 12551: 12530: 12515: 12504: 12493: 12487: 12379: 12304:For each object 12255: 12193: 12087:For each object 12023:initial morphism 11978: 11976: 11975: 11970: 11968: 11964: 11963: 11945: 11944: 11922: 11921: 11902: 11901: 11883: 11882: 11863: 11862: 11831: 11829: 11828: 11823: 11821: 11790: 11789: 11784: 11763: 11762: 11743: 11742: 11727: 11726: 11677: 11676: 11671: 11650: 11649: 11630: 11629: 11613: 11605: 11559: 11558: 11553: 11532: 11531: 11491: 11490: 11441: 11440: 11435: 11399: 11398: 11372: 11364: 11063: 11061: 11060: 11055: 11043: 11041: 11040: 11035: 11033: 11021: 11019: 11018: 11013: 11011: 10999: 10997: 10996: 10991: 10983: 10971: 10969: 10968: 10963: 10952: 10938: 10926: 10924: 10923: 10918: 10916: 10915: 10880: 10878: 10877: 10872: 10870: 10869: 10820: 10818: 10817: 10812: 10807: 10783: 10781: 10780: 10775: 10739: 10737: 10736: 10731: 10726: 10708: 10706: 10705: 10700: 10698: 10686: 10684: 10683: 10678: 10673: 10652: 10650: 10649: 10644: 10599: 10597: 10596: 10591: 10579: 10577: 10576: 10571: 10535: 10533: 10532: 10527: 10525: 10486: 10484: 10483: 10478: 10466: 10464: 10463: 10458: 10446: 10444: 10443: 10438: 10426: 10424: 10423: 10418: 10407:with respect to 10406: 10404: 10403: 10398: 10380: 10378: 10377: 10372: 10360: 10358: 10357: 10352: 10340: 10338: 10337: 10332: 10327: 10326: 10306: 10304: 10303: 10298: 10258: 10257: 10212: 10211: 10190: 10188: 10187: 10182: 10168: 10167: 10140: 10139: 10094: 10092: 10091: 10086: 10031: 10030: 9985: 9984: 9966: 9964: 9963: 9958: 9937: 9935: 9934: 9929: 9911: 9909: 9908: 9903: 9880: 9879: 9860: 9858: 9857: 9852: 9840: 9838: 9837: 9832: 9830: 9829: 9813: 9811: 9810: 9805: 9793: 9791: 9790: 9785: 9783: 9782: 9766: 9764: 9763: 9758: 9731: 9729: 9728: 9723: 9712: 9711: 9686: 9684: 9683: 9678: 9651: 9649: 9648: 9643: 9632: 9631: 9606: 9604: 9603: 9598: 9580: 9578: 9577: 9572: 9561: 9560: 9527: 9526: 9501: 9499: 9498: 9493: 9459: 9457: 9456: 9451: 9440: 9439: 9409: 9408: 9386: 9384: 9383: 9378: 9367: 9366: 9348: 9328: 9327: 9315: 9301: 9299: 9298: 9293: 9272: 9270: 9269: 9264: 9247: 9246: 9227: 9225: 9224: 9219: 9207: 9205: 9204: 9199: 9187: 9185: 9184: 9179: 9167: 9165: 9164: 9159: 9147: 9145: 9144: 9139: 9127: 9125: 9124: 9119: 9107: 9105: 9104: 9099: 9094: 9093: 9075: 9074: 9058: 9056: 9055: 9050: 9030: 9028: 9027: 9022: 9010: 9008: 9007: 9002: 8997: 8996: 8977: 8975: 8974: 8969: 8957: 8955: 8954: 8949: 8937: 8935: 8934: 8929: 8911: 8909: 8908: 8903: 8892: 8889: 8880: 8878: 8877: 8872: 8861: 8858: 8849: 8847: 8846: 8841: 8839: 8838: 8822: 8820: 8819: 8814: 8812: 8811: 8795: 8793: 8792: 8787: 8782: 8781: 8762: 8760: 8759: 8754: 8736: 8734: 8733: 8728: 8716: 8714: 8713: 8708: 8688: 8686: 8685: 8680: 8669: 8666: 8652: 8649: 8644: 8643: 8625: 8623: 8622: 8617: 8593: 8591: 8590: 8585: 8565:, a subfield of 8560: 8558: 8557: 8552: 8540: 8538: 8537: 8532: 8520: 8518: 8517: 8512: 8510: 8509: 8493: 8491: 8490: 8485: 8483: 8482: 8466: 8464: 8463: 8458: 8446: 8444: 8443: 8438: 8426: 8424: 8423: 8418: 8407:of all elements 8402: 8400: 8399: 8394: 8380: 8379: 8352: 8351: 8308: 8306: 8305: 8300: 8288: 8286: 8285: 8280: 8268: 8266: 8265: 8260: 8248: 8246: 8245: 8240: 8238: 8237: 8212: 8210: 8209: 8204: 8178: 8177: 8156: 8155: 8139: 8137: 8136: 8131: 8119: 8117: 8116: 8111: 8099: 8097: 8096: 8091: 8073: 8071: 8070: 8065: 8051: 8050: 8019: 8017: 8016: 8011: 8009: 8008: 7964:the endofunctor 7652:coherent sheaves 7525:Hausdorff spaces 7469:homotopy classes 7467:, the space of 7444:trivial topology 7369:negative numbers 7271:Polynomial rings 7025:Ring extensions. 7016: 7014: 7013: 7008: 6940:Further examples 6517:diagonal functor 6398: 6396: 6395: 6390: 6385: 6384: 6354: 6352: 6351: 6346: 6344: 6343: 6312: 6310: 6309: 6304: 6296: 6289: 6288: 6268: 6254: 6250: 6249: 6232: 6214:the composition 6209: 6207: 6206: 6201: 6181: 6180: 6142: 6140: 6139: 6134: 6132: 6131: 6088: 6086: 6085: 6080: 6075: 6074: 6041: 6039: 6038: 6033: 6025: 6021: 6020: 6003: 5989: 5982: 5981: 5961: 5944:the composition 5939: 5937: 5936: 5931: 5911: 5910: 5888: 5886: 5885: 5880: 5783: 5781: 5780: 5775: 5755: 5754: 5722: 5720: 5719: 5714: 5709: 5708: 5672: 5670: 5669: 5664: 5644: 5643: 5590: 5588: 5587: 5582: 5562: 5561: 5525: 5523: 5522: 5517: 5497: 5496: 5330: 5328: 5327: 5322: 5305:was the functor 5221: 5219: 5218: 5213: 5162: 5160: 5159: 5154: 5152: 5151: 5128: 5126: 5125: 5120: 5118: 5117: 5101: 5099: 5098: 5093: 5091: 5090: 5077: 5075: 5074: 5069: 5067: 5066: 5065: 5044: 5042: 5041: 5036: 5034: 5030: 5029: 5011: 5010: 4988: 4987: 4968: 4967: 4949: 4948: 4929: 4928: 4883: 4881: 4880: 4875: 4873: 4847: 4846: 4811: 4810: 4773: 4771: 4770: 4765: 4747: 4745: 4744: 4739: 4657: 4655: 4654: 4649: 4644: 4629: 4618: 4603: 4590: 4588: 4587: 4582: 4577: 4562: 4551: 4536: 4506: 4504: 4503: 4498: 4496: 4483: 4482: 4481: 4457: 4456: 4455: 4383:consists of two 4334: 4330: 4271: 4250: 4228:category of sets 4221: 4207: 4193: 4130:for all objects 4126: 4124: 4123: 4118: 4098: 4097: 4092: 4059: 4058: 4053: 4038: 4037: 4008: 4006: 4005: 4000: 3980: 3979: 3974: 3941: 3940: 3935: 3904: 3876:consists of two 3848: 3846: 3845: 3840: 3828: 3826: 3825: 3820: 3808: 3806: 3805: 3800: 3788: 3786: 3785: 3780: 3765: 3763: 3762: 3757: 3741: 3739: 3738: 3733: 3721: 3719: 3718: 3713: 3701: 3699: 3698: 3693: 3691: 3664: 3662: 3661: 3656: 3648: 3647: 3646: 3630: 3629: 3589: 3587: 3586: 3581: 3557: 3555: 3554: 3549: 3526: 3524: 3523: 3518: 3510: 3509: 3478: 3476: 3475: 3470: 3437: 3435: 3434: 3429: 3396: 3394: 3393: 3388: 3376: 3374: 3373: 3368: 3356: 3354: 3353: 3348: 3316: 3315: 3299: 3297: 3296: 3291: 3279: 3277: 3276: 3271: 3250: 3248: 3247: 3242: 3230: 3228: 3227: 3222: 3210: 3208: 3207: 3202: 3190: 3188: 3187: 3182: 3166: 3164: 3163: 3158: 3146: 3144: 3143: 3138: 3122: 3120: 3119: 3114: 3087: 3085: 3084: 3079: 3063: 3061: 3060: 3055: 3043: 3041: 3040: 3035: 3023: 3021: 3020: 3015: 3007: 2986: 2984: 2983: 2978: 2976: 2975: 2974: 2928: 2927: 2911: 2909: 2908: 2903: 2879: 2877: 2876: 2871: 2841: 2839: 2838: 2833: 2810: 2809: 2793: 2791: 2790: 2785: 2752: 2750: 2749: 2744: 2711: 2709: 2708: 2703: 2691: 2689: 2688: 2683: 2671: 2669: 2668: 2663: 2631: 2630: 2614: 2612: 2611: 2606: 2594: 2592: 2591: 2586: 2565: 2563: 2562: 2557: 2545: 2543: 2542: 2537: 2525: 2523: 2522: 2517: 2505: 2503: 2502: 2497: 2481: 2479: 2478: 2473: 2461: 2459: 2458: 2453: 2437: 2435: 2434: 2429: 2244:The notion that 2105:to our problem: 1952:. The category 1917:if it defines a 1849: 1828: 1826: 1825: 1820: 1772: 1770: 1769: 1764: 1752: 1750: 1749: 1744: 1722: 1720: 1719: 1714: 1691:, we also write 1679: 1677: 1676: 1671: 1669: 1668: 1667: 1661: 1642: 1640: 1639: 1634: 1622: 1620: 1619: 1614: 1612: 1611: 1610: 1604: 1585: 1583: 1582: 1577: 1565: 1563: 1562: 1557: 1545: 1543: 1542: 1537: 1522: 1520: 1519: 1514: 1502: 1500: 1499: 1494: 1482: 1480: 1479: 1474: 1458: 1456: 1455: 1450: 1438: 1436: 1435: 1430: 1414: 1412: 1411: 1406: 1394: 1392: 1391: 1386: 1370: 1368: 1367: 1362: 1347: 1345: 1344: 1339: 1319: 1318: 1317: 1311: 1292: 1290: 1289: 1284: 1271: 1269: 1268: 1263: 1251: 1249: 1248: 1243: 1225: 1223: 1222: 1217: 1202: 1200: 1199: 1194: 1174: 1173: 1172: 1166: 1133: 1132: 1131: 1125: 1110: 1109: 1055: 1053: 1052: 1047: 1045: 1044: 1031: 1029: 1028: 1023: 1021: 1020: 1003: 1001: 1000: 995: 993: 992: 979: 977: 976: 971: 969: 968: 952: 950: 949: 944: 925: 923: 922: 917: 899: 897: 896: 891: 878: 876: 875: 870: 859:left adjoint to 852: 850: 849: 844: 829: 827: 826: 821: 819: 818: 805: 803: 802: 797: 785: 783: 782: 777: 775: 761: 760: 733: 732: 719: 717: 716: 711: 709: 695: 694: 667: 666: 653: 651: 650: 645: 643: 642: 629: 627: 626: 621: 609: 607: 606: 601: 599: 598: 597: 594: 578: 577: 550: 549: 536: 534: 533: 528: 526: 525: 524: 521: 505: 504: 477: 476: 463: 461: 460: 455: 443: 441: 440: 435: 416: 414: 413: 408: 388: 387: 386: 380: 347: 346: 345: 339: 313: 311: 310: 305: 303: 302: 289: 287: 286: 281: 269: 267: 266: 261: 259: 258: 245: 243: 242: 237: 222: 220: 219: 214: 212: 211: 202: 201: 182: 180: 179: 174: 172: 171: 162: 161: 135: 133: 132: 127: 125: 124: 111: 109: 108: 103: 101: 100: 61:, one being the 59:adjoint functors 36:Adjunction space 21: 16923: 16922: 16918: 16917: 16916: 16914: 16913: 16912: 16898: 16897: 16896: 16891: 16813: 16807: 16777: 16772: 16726: 16696: 16663: 16640: 16631: 16588: 16572: 16523: 16513: 16500: 16483: 16432: 16370: 16339:Initial objects 16325: 16271: 16164: 16153: 16151:Category theory 16148: 16090:of The Catsters 16078: 16074: 16056: 16020: 16009: 15999: 15994: 15993: 15971: 15967: 15954: 15953: 15949: 15929: 15925: 15909:10.2307/1993102 15889: 15883: 15879: 15862: 15858: 15853: 15782: 15778: 15770: 15767: 15766: 15736: 15735: 15731: 15723: 15720: 15719: 15688: 15687: 15678: 15677: 15669: 15666: 15665: 15639: 15624: 15603: 15596: 15581: 15559: 15552: 15534: 15499: 15439: 15434: 15359: 15358: 15347: 15346: 15318: 15317: 15306: 15305: 15290: 15286: 15284: 15281: 15280: 15230: 15165: 15128: 15127: 15117: 15116: 15112: 15100: 15080: 15071: 15060: 15052: 15045: 15044: 15036: 15022: 15011: 15000: 14994: 14986: 14978: 14967: 14961: 14954: 14953: 14949: 14944: 14942: 14939: 14938: 14884: 14882: 14879: 14878: 14841: 14833: 14830: 14829: 14791: 14770: 14767: 14766: 14750: 14747: 14746: 14729: 14728: 14713: 14709: 14697: 14693: 14677: 14669: 14666: 14665: 14637: 14629: 14625: 14623: 14620: 14619: 14548:Conversely, if 14513:If the functor 14511: 14453: 14450: 14449: 14428: 14410: 14401: 14346: 14333: 14316: 14259: 14253: 14248: 14222: 14218: 14206: 14202: 14184: 14180: 14178: 14175: 14174: 14166: 14160: 14154: 14121: 14117: 14099: 14095: 14083: 14079: 14077: 14074: 14073: 14063: 14057: 14047: 13990: 13989: 13968: 13964: 13943: 13932: 13925: 13924: 13918: 13914: 13875: 13871: 13867: 13865: 13862: 13861: 13840: 13818: 13769: 13758: 13757: 13745: 13741: 13739: 13736: 13735: 13689: 13678: 13677: 13662: 13658: 13640: 13636: 13627: 13623: 13621: 13618: 13617: 13576: 13565: 13564: 13552: 13548: 13546: 13543: 13542: 13496: 13485: 13484: 13469: 13465: 13453: 13439: 13426: 13422: 13420: 13417: 13416: 13368: 13365: 13364: 13355: 13345: 13316:Given functors 13314: 13292: 13291: 13270: 13266: 13257: 13256: 13241: 13237: 13225: 13221: 13206: 13205: 13199: 13195: 13165: 13161: 13148: 13135: 13133: 13130: 13129: 13123: 13113: 13103: 13074: 13073: 13058: 13054: 13039: 13038: 13029: 13025: 13007: 13003: 12988: 12987: 12978: 12974: 12941: 12937: 12930: 12917: 12915: 12912: 12911: 12905: 12893: 12887: 12858: 12857: 12836: 12832: 12808: 12804: 12801: 12800: 12794: 12790: 12751: 12747: 12743: 12741: 12738: 12737: 12699: 12689: 12666: 12663: 12662: 12634:Given functors 12632: 12607: 12606: 12599: 12573: 12572: 12541: 12540: 12482: 12481: 12474: 12466: 12459: 12448: 12441: 12426: 12419: 12408: 12401: 12387: 12353: 12343: 12333: 12296: 12286: 12250: 12237: 12226: 12207: 12206: 12192: 12191: 12183: 12182: 12174: 12163: 12156: 12122: 12108: 12054: 12020: 11992: 11966: 11965: 11956: 11952: 11940: 11936: 11923: 11914: 11910: 11907: 11906: 11897: 11893: 11875: 11871: 11864: 11855: 11851: 11847: 11845: 11842: 11841: 11819: 11818: 11785: 11774: 11773: 11769: 11764: 11758: 11754: 11747: 11735: 11731: 11713: 11709: 11706: 11705: 11672: 11661: 11660: 11656: 11651: 11645: 11641: 11634: 11622: 11618: 11606: 11592: 11585: 11584: 11554: 11543: 11542: 11538: 11533: 11527: 11523: 11501: 11480: 11476: 11467: 11466: 11436: 11425: 11424: 11420: 11415: 11394: 11390: 11383: 11365: 11354: 11340: 11338: 11335: 11334: 11291: 11245: 11182: 11170: 11149: 11139: 11070: 11049: 11046: 11045: 11029: 11027: 11024: 11023: 11007: 11005: 11002: 11001: 10979: 10977: 10974: 10973: 10948: 10934: 10932: 10929: 10928: 10911: 10907: 10893: 10890: 10889: 10862: 10858: 10826: 10823: 10822: 10803: 10789: 10786: 10785: 10745: 10742: 10741: 10722: 10714: 10711: 10710: 10694: 10692: 10689: 10688: 10669: 10661: 10658: 10657: 10605: 10602: 10601: 10585: 10582: 10581: 10541: 10538: 10537: 10521: 10519: 10516: 10515: 10505: 10472: 10469: 10468: 10467:is replaced by 10452: 10449: 10448: 10432: 10429: 10428: 10412: 10409: 10408: 10386: 10383: 10382: 10366: 10363: 10362: 10346: 10343: 10342: 10322: 10318: 10316: 10313: 10312: 10250: 10246: 10207: 10203: 10201: 10198: 10197: 10163: 10159: 10135: 10131: 10104: 10101: 10100: 10023: 10019: 9980: 9976: 9974: 9971: 9970: 9943: 9940: 9939: 9917: 9914: 9913: 9872: 9868: 9866: 9863: 9862: 9846: 9843: 9842: 9825: 9821: 9819: 9816: 9815: 9799: 9796: 9795: 9778: 9774: 9772: 9769: 9768: 9737: 9734: 9733: 9704: 9700: 9692: 9689: 9688: 9657: 9654: 9653: 9652:, then clearly 9624: 9620: 9612: 9609: 9608: 9586: 9583: 9582: 9553: 9549: 9519: 9515: 9507: 9504: 9503: 9472: 9469: 9468: 9432: 9428: 9404: 9400: 9398: 9395: 9394: 9362: 9358: 9344: 9323: 9319: 9311: 9309: 9306: 9305: 9281: 9278: 9277: 9239: 9235: 9233: 9230: 9229: 9213: 9210: 9209: 9193: 9190: 9189: 9173: 9170: 9169: 9153: 9150: 9149: 9133: 9130: 9129: 9113: 9110: 9109: 9089: 9085: 9070: 9066: 9064: 9061: 9060: 9044: 9041: 9040: 9016: 9013: 9012: 8992: 8988: 8983: 8980: 8979: 8963: 8960: 8959: 8943: 8940: 8939: 8917: 8914: 8913: 8888: 8886: 8883: 8882: 8857: 8855: 8852: 8851: 8834: 8830: 8828: 8825: 8824: 8807: 8803: 8801: 8798: 8797: 8777: 8773: 8768: 8765: 8764: 8742: 8739: 8738: 8722: 8719: 8718: 8702: 8699: 8698: 8665: 8648: 8639: 8635: 8633: 8630: 8629: 8599: 8596: 8595: 8579: 8576: 8575: 8546: 8543: 8542: 8526: 8523: 8522: 8505: 8501: 8499: 8496: 8495: 8478: 8474: 8472: 8469: 8468: 8467:to which it is 8452: 8449: 8448: 8432: 8429: 8428: 8412: 8409: 8408: 8375: 8371: 8347: 8343: 8316: 8313: 8312: 8294: 8291: 8290: 8274: 8271: 8270: 8254: 8251: 8250: 8233: 8229: 8227: 8224: 8223: 8173: 8169: 8151: 8147: 8145: 8142: 8141: 8125: 8122: 8121: 8105: 8102: 8101: 8079: 8076: 8075: 8046: 8042: 8025: 8022: 8021: 8004: 8000: 7998: 7995: 7994: 7991:Quantification. 7987: 7933: 7882: 7880:Category theory 7813:is a subset of 7759:William Lawvere 7697:if and only if 7683: 7660:The article on 7658:Soberification. 7649: 7602: 7508:homotopy theory 7430:, creating the 7404: 7293:polynomial ring 7286: 7279: 7262: 7251: 7177: 7112:Tensor products 7002: 6999: 6998: 6969:and defining a 6947: 6942: 6881: 6874: 6831: 6824: 6776: 6711: 6703: 6696: 6690: 6681: 6672: 6663: 6656: 6645: 6638: 6631: 6624: 6617: 6610: 6562: 6555: 6548: 6541: 6507: 6500: 6492: 6486: 6451:fibred products 6444: 6425: 6380: 6376: 6368: 6365: 6364: 6336: 6332: 6330: 6327: 6326: 6284: 6280: 6267: 6242: 6238: 6231: 6223: 6220: 6219: 6176: 6172: 6170: 6167: 6166: 6124: 6120: 6118: 6115: 6114: 6070: 6066: 6058: 6055: 6054: 6013: 6009: 6002: 5977: 5973: 5960: 5952: 5949: 5948: 5906: 5902: 5900: 5897: 5896: 5850: 5847: 5846: 5750: 5746: 5744: 5741: 5740: 5704: 5700: 5686: 5683: 5682: 5639: 5635: 5633: 5630: 5629: 5612:For each group 5557: 5553: 5551: 5548: 5547: 5492: 5488: 5486: 5483: 5482: 5394: 5389: 5331:(i.e. take the 5310: 5307: 5306: 5255: 5195: 5192: 5191: 5188:string diagrams 5144: 5140: 5138: 5135: 5134: 5133:to itself, and 5113: 5109: 5107: 5104: 5103: 5086: 5085: 5083: 5080: 5079: 5061: 5060: 5056: 5054: 5051: 5050: 5032: 5031: 5022: 5018: 5006: 5002: 4989: 4980: 4976: 4973: 4972: 4963: 4959: 4941: 4937: 4930: 4921: 4917: 4913: 4911: 4908: 4907: 4871: 4870: 4848: 4842: 4838: 4835: 4834: 4812: 4806: 4802: 4798: 4796: 4793: 4792: 4753: 4750: 4749: 4709: 4706: 4705: 4672: 4666: 4628: 4602: 4597: 4594: 4593: 4561: 4535: 4530: 4527: 4526: 4494: 4493: 4477: 4476: 4472: 4465: 4459: 4458: 4451: 4450: 4446: 4430: 4423: 4421: 4418: 4417: 4369: 4346: 4314: 4302: 4287:Naturality of Ξ¦ 4256: 4238: 4213: 4201: 4195: 4187: 4181: 4093: 4082: 4081: 4054: 4043: 4042: 4027: 4023: 4021: 4018: 4017: 3975: 3964: 3963: 3936: 3925: 3924: 3916: 3913: 3912: 3892: 3859: 3834: 3831: 3830: 3814: 3811: 3810: 3809:if and only if 3794: 3791: 3790: 3774: 3771: 3770: 3751: 3748: 3747: 3727: 3724: 3723: 3707: 3704: 3703: 3684: 3670: 3667: 3666: 3639: 3638: 3634: 3625: 3621: 3595: 3592: 3591: 3563: 3560: 3559: 3543: 3540: 3539: 3505: 3501: 3484: 3481: 3480: 3443: 3440: 3439: 3402: 3399: 3398: 3382: 3379: 3378: 3362: 3359: 3358: 3311: 3307: 3305: 3302: 3301: 3300:and a morphism 3285: 3282: 3281: 3256: 3253: 3252: 3236: 3233: 3232: 3216: 3213: 3212: 3196: 3193: 3192: 3176: 3173: 3172: 3152: 3149: 3148: 3132: 3129: 3128: 3096: 3093: 3092: 3073: 3070: 3069: 3049: 3046: 3045: 3029: 3026: 3025: 3000: 2992: 2989: 2988: 2967: 2966: 2962: 2923: 2919: 2917: 2914: 2913: 2885: 2882: 2881: 2865: 2862: 2861: 2805: 2801: 2799: 2796: 2795: 2758: 2755: 2754: 2717: 2714: 2713: 2697: 2694: 2693: 2677: 2674: 2673: 2626: 2622: 2620: 2617: 2616: 2615:and a morphism 2600: 2597: 2596: 2571: 2568: 2567: 2551: 2548: 2547: 2531: 2528: 2527: 2511: 2508: 2507: 2491: 2488: 2487: 2482:there exists a 2467: 2464: 2463: 2447: 2444: 2443: 2411: 2408: 2407: 2404: 2321: 2293: 2227: 2156:adjoint functor 2118: 2111: 2104: 2097: 2090: 2079: 2060: 2056: 2052: 2045: 2038: 2027: 2012: 2001: 1864: 1856:colimits/limits 1850: 1842: 1835: 1778: 1775: 1774: 1758: 1755: 1754: 1738: 1735: 1734: 1699: 1696: 1695: 1663: 1662: 1651: 1650: 1648: 1645: 1644: 1628: 1625: 1624: 1606: 1605: 1594: 1593: 1591: 1588: 1587: 1571: 1568: 1567: 1551: 1548: 1547: 1531: 1528: 1527: 1508: 1505: 1504: 1488: 1485: 1484: 1468: 1465: 1464: 1444: 1441: 1440: 1424: 1421: 1420: 1400: 1397: 1396: 1380: 1377: 1376: 1353: 1350: 1349: 1313: 1312: 1301: 1300: 1298: 1295: 1294: 1293:is an arrow in 1278: 1275: 1274: 1257: 1254: 1253: 1237: 1234: 1233: 1211: 1208: 1207: 1168: 1167: 1156: 1155: 1127: 1126: 1115: 1114: 1102: 1098: 1096: 1093: 1092: 1062: 1040: 1039: 1037: 1034: 1033: 1016: 1015: 1013: 1010: 1009: 988: 987: 985: 982: 981: 964: 963: 961: 958: 957: 932: 929: 928: 911: 908: 907: 885: 882: 881: 864: 861: 860: 838: 835: 834: 814: 813: 811: 808: 807: 791: 788: 787: 765: 756: 755: 728: 727: 725: 722: 721: 699: 690: 689: 662: 661: 659: 656: 655: 638: 637: 635: 632: 631: 615: 612: 611: 593: 589: 582: 573: 572: 545: 544: 542: 539: 538: 520: 516: 509: 500: 499: 472: 471: 469: 466: 465: 449: 446: 445: 429: 426: 425: 382: 381: 370: 369: 341: 340: 329: 328: 326: 323: 322: 298: 297: 295: 292: 291: 275: 272: 271: 254: 253: 251: 248: 247: 231: 228: 227: 207: 206: 197: 196: 188: 185: 184: 167: 166: 157: 156: 148: 145: 144: 120: 119: 117: 114: 113: 96: 95: 93: 90: 89: 47:category theory 45:, specifically 39: 28: 23: 22: 18:Adjoint functor 15: 12: 11: 5: 16921: 16911: 16910: 16893: 16892: 16890: 16889: 16884: 16879: 16874: 16869: 16864: 16859: 16854: 16849: 16844: 16839: 16834: 16829: 16824: 16818: 16815: 16814: 16806: 16805: 16798: 16791: 16783: 16774: 16773: 16771: 16770: 16760: 16750: 16739: 16736: 16735: 16732: 16731: 16728: 16727: 16725: 16724: 16719: 16714: 16700: 16694: 16689: 16684: 16678: 16676: 16669: 16668: 16665: 16664: 16662: 16661: 16656: 16645: 16643: 16638: 16633: 16632: 16630: 16629: 16624: 16619: 16614: 16609: 16604: 16593: 16591: 16586: 16578: 16574: 16573: 16571: 16566: 16564:String diagram 16561: 16556: 16554:Model category 16551: 16546: 16541: 16536: 16531: 16529: 16522: 16521: 16518: 16515: 16514: 16502: 16501: 16494: 16492: 16489: 16488: 16485: 16484: 16482: 16481: 16476: 16474:Comma category 16471: 16466: 16461: 16456: 16451: 16446: 16440: 16438: 16434: 16433: 16431: 16430: 16420: 16410: 16408:Abelian groups 16405: 16400: 16395: 16390: 16384: 16382: 16376: 16375: 16372: 16371: 16369: 16368: 16363: 16358: 16357: 16356: 16346: 16341: 16335: 16333: 16327: 16326: 16324: 16323: 16318: 16313: 16312: 16311: 16301: 16296: 16290: 16288: 16279: 16273: 16272: 16270: 16269: 16264: 16259: 16254: 16249: 16244: 16239: 16234: 16229: 16224: 16219: 16214: 16213: 16212: 16207: 16202: 16197: 16192: 16187: 16176: 16174: 16166: 16165: 16155: 16154: 16147: 16146: 16139: 16132: 16124: 16118: 16117: 16104:, categories, 16091: 16073: 16072:External links 16070: 16069: 16068: 16054: 16032: 16018: 15998: 15995: 15992: 15991: 15965: 15947: 15923: 15902:(2): 294–329. 15877: 15855: 15854: 15852: 15849: 15806: 15805: 15793: 15790: 15785: 15781: 15777: 15774: 15760: 15759: 15748: 15745: 15739: 15734: 15730: 15727: 15705: 15704: 15691: 15686: 15681: 15676: 15673: 15661:. The functor 15638: 15635: 15620: 15601: 15594: 15577: 15557: 15548: 15532: 15498: 15495: 15438: 15435: 15433: 15430: 15395: 15394: 15383: 15380: 15377: 15374: 15371: 15368: 15362: 15356: 15353: 15350: 15345: 15342: 15339: 15336: 15333: 15330: 15327: 15321: 15315: 15312: 15309: 15304: 15299: 15296: 15293: 15289: 15229: 15226: 15225: 15224: 15217: 15210: 15203: 15164: 15161: 15142: 15141: 15126: 15120: 15115: 15108: 15104: 15099: 15096: 15090: 15086: 15083: 15079: 15075: 15070: 15066: 15063: 15058: 15055: 15051: 15048: 15046: 15042: 15039: 15035: 15032: 15028: 15025: 15017: 15014: 15010: 15006: 15003: 14998: 14992: 14989: 14984: 14981: 14973: 14970: 14965: 14957: 14952: 14948: 14946: 14924: 14923: 14912: 14909: 14906: 14903: 14900: 14897: 14894: 14890: 14887: 14872: 14871: 14860: 14857: 14854: 14851: 14847: 14844: 14840: 14837: 14790: 14787: 14774: 14754: 14743: 14742: 14727: 14724: 14719: 14716: 14712: 14708: 14703: 14700: 14696: 14692: 14689: 14686: 14683: 14680: 14678: 14675: 14672: 14668: 14667: 14664: 14661: 14658: 14655: 14652: 14649: 14646: 14643: 14640: 14638: 14635: 14632: 14628: 14627: 14605: 14604: 14593: 14510: 14507: 14506: 14505: 14492: 14469: 14466: 14463: 14460: 14457: 14439: 14438: 14424: 14403: 14402: 14397: 14376: 14375: 14336: 14335: 14329: 14312: 14287:Peter J. Freyd 14252: 14249: 14247: 14244: 14243: 14242: 14228: 14225: 14221: 14217: 14214: 14209: 14205: 14201: 14198: 14195: 14190: 14187: 14183: 14172: 14162: 14156: 14152: 14141: 14129: 14124: 14120: 14116: 14113: 14110: 14105: 14102: 14098: 14094: 14089: 14086: 14082: 14070: 14069: 14059: 14049: 14043: 14031: 14030: 14003: 13988: 13985: 13982: 13979: 13976: 13971: 13967: 13963: 13960: 13957: 13954: 13949: 13946: 13941: 13938: 13935: 13931: 13927: 13926: 13921: 13917: 13913: 13910: 13907: 13904: 13901: 13898: 13895: 13892: 13889: 13884: 13881: 13878: 13874: 13870: 13869: 13858: 13857: 13854: 13836: 13814: 13807: 13795: 13792: 13789: 13786: 13783: 13780: 13777: 13772: 13767: 13764: 13761: 13756: 13751: 13748: 13744: 13734:, where   13715: 13712: 13709: 13706: 13703: 13700: 13697: 13692: 13687: 13684: 13681: 13676: 13673: 13668: 13665: 13661: 13657: 13652: 13649: 13646: 13643: 13639: 13635: 13630: 13626: 13614: 13602: 13599: 13596: 13593: 13590: 13587: 13584: 13579: 13574: 13571: 13568: 13563: 13558: 13555: 13551: 13541:, where   13522: 13519: 13516: 13513: 13510: 13507: 13504: 13499: 13494: 13491: 13488: 13483: 13480: 13475: 13472: 13468: 13464: 13459: 13456: 13451: 13448: 13445: 13442: 13438: 13434: 13429: 13425: 13409: 13408: 13396: 13393: 13390: 13387: 13384: 13381: 13378: 13375: 13372: 13351: 13341: 13313: 13310: 13309: 13308: 13305: 13290: 13287: 13284: 13281: 13276: 13273: 13269: 13265: 13262: 13260: 13258: 13255: 13252: 13247: 13244: 13240: 13236: 13233: 13228: 13224: 13220: 13217: 13214: 13211: 13209: 13207: 13202: 13198: 13194: 13191: 13188: 13185: 13182: 13179: 13176: 13173: 13168: 13164: 13160: 13157: 13154: 13151: 13149: 13147: 13144: 13141: 13138: 13137: 13126: 13125: 13119: 13109: 13099: 13091: 13090: 13087: 13072: 13069: 13064: 13061: 13057: 13053: 13050: 13047: 13044: 13042: 13040: 13037: 13032: 13028: 13024: 13021: 13018: 13013: 13010: 13006: 13002: 12999: 12996: 12993: 12991: 12989: 12986: 12981: 12977: 12973: 12970: 12967: 12964: 12961: 12958: 12955: 12952: 12949: 12944: 12940: 12936: 12933: 12931: 12929: 12926: 12923: 12920: 12919: 12908: 12907: 12901: 12889: 12883: 12875: 12874: 12871: 12856: 12853: 12850: 12847: 12844: 12839: 12835: 12831: 12828: 12825: 12822: 12817: 12814: 12811: 12807: 12803: 12802: 12797: 12793: 12789: 12786: 12783: 12780: 12777: 12774: 12771: 12768: 12765: 12760: 12757: 12754: 12750: 12746: 12745: 12734: 12733: 12695: 12685: 12670: 12631: 12628: 12623: 12622: 12621: 12620: 12604: 12597: 12593: 12570: 12566: 12538: 12534: 12479: 12472: 12468: 12464: 12457: 12446: 12439: 12424: 12417: 12413:, any objects 12406: 12399: 12389: 12383: 12345: 12335: 12329: 12312:, each object 12292: 12282: 12279: 12278: 12277: 12266: 12246: 12243: 12235: 12224: 12204: 12200: 12189: 12185: 12180: 12176: 12172: 12161: 12154: 12144: 12118: 12104: 12053: 12050: 12038: 12037: 12016: 12009: 11988: 11980: 11979: 11962: 11959: 11955: 11951: 11948: 11943: 11939: 11935: 11932: 11929: 11926: 11924: 11920: 11917: 11913: 11909: 11908: 11905: 11900: 11896: 11892: 11889: 11886: 11881: 11878: 11874: 11870: 11867: 11865: 11861: 11858: 11854: 11850: 11849: 11838: 11837: 11833: 11832: 11817: 11814: 11811: 11808: 11805: 11802: 11799: 11796: 11793: 11788: 11783: 11780: 11777: 11770: 11768: 11765: 11761: 11757: 11753: 11750: 11748: 11746: 11741: 11738: 11734: 11730: 11725: 11722: 11719: 11716: 11712: 11708: 11707: 11704: 11701: 11698: 11695: 11692: 11689: 11686: 11683: 11680: 11675: 11670: 11667: 11664: 11657: 11655: 11652: 11648: 11644: 11640: 11637: 11635: 11633: 11628: 11625: 11621: 11617: 11612: 11609: 11604: 11601: 11598: 11595: 11591: 11587: 11586: 11583: 11580: 11577: 11574: 11571: 11568: 11565: 11562: 11557: 11552: 11549: 11546: 11539: 11537: 11534: 11530: 11526: 11522: 11519: 11516: 11513: 11510: 11507: 11504: 11502: 11500: 11497: 11494: 11489: 11486: 11483: 11479: 11475: 11472: 11469: 11468: 11465: 11462: 11459: 11456: 11453: 11450: 11447: 11444: 11439: 11434: 11431: 11428: 11421: 11419: 11416: 11414: 11411: 11408: 11405: 11402: 11397: 11393: 11389: 11386: 11384: 11382: 11379: 11376: 11371: 11368: 11363: 11360: 11357: 11353: 11349: 11346: 11343: 11342: 11331: 11330: 11316: 11315: 11314: 11313: 11283: 11237: 11192: 11191: 11178: 11175: 11166: 11155: 11145: 11135: 11128: 11110: 11069: 11066: 11053: 11032: 11010: 10989: 10986: 10982: 10961: 10958: 10955: 10951: 10947: 10944: 10941: 10937: 10914: 10910: 10906: 10903: 10900: 10897: 10868: 10865: 10861: 10857: 10854: 10851: 10848: 10845: 10842: 10839: 10836: 10833: 10830: 10810: 10806: 10802: 10799: 10796: 10793: 10773: 10770: 10767: 10764: 10761: 10758: 10755: 10752: 10749: 10729: 10725: 10721: 10718: 10697: 10676: 10672: 10668: 10665: 10642: 10639: 10636: 10633: 10630: 10627: 10624: 10621: 10618: 10615: 10612: 10609: 10589: 10569: 10566: 10563: 10560: 10557: 10554: 10551: 10548: 10545: 10524: 10504: 10501: 10500: 10499: 10489: 10488: 10476: 10456: 10436: 10416: 10396: 10393: 10390: 10370: 10350: 10330: 10325: 10321: 10309: 10308: 10307: 10296: 10293: 10289: 10286: 10283: 10279: 10276: 10273: 10270: 10267: 10264: 10261: 10256: 10253: 10249: 10245: 10242: 10239: 10236: 10233: 10230: 10227: 10224: 10221: 10218: 10215: 10210: 10206: 10192: 10180: 10177: 10174: 10171: 10166: 10162: 10158: 10155: 10152: 10149: 10146: 10143: 10138: 10134: 10129: 10126: 10123: 10120: 10117: 10114: 10111: 10108: 10097: 10096: 10095: 10084: 10081: 10078: 10075: 10072: 10069: 10066: 10062: 10059: 10056: 10052: 10049: 10046: 10043: 10040: 10037: 10034: 10029: 10026: 10022: 10018: 10015: 10012: 10009: 10006: 10003: 10000: 9997: 9994: 9991: 9988: 9983: 9979: 9956: 9953: 9950: 9947: 9927: 9924: 9921: 9901: 9898: 9895: 9892: 9889: 9886: 9883: 9878: 9875: 9871: 9861:'s, such that 9850: 9828: 9824: 9803: 9781: 9777: 9756: 9753: 9750: 9747: 9744: 9741: 9721: 9718: 9715: 9710: 9707: 9703: 9699: 9696: 9676: 9673: 9670: 9667: 9664: 9661: 9641: 9638: 9635: 9630: 9627: 9623: 9619: 9616: 9596: 9593: 9590: 9570: 9567: 9564: 9559: 9556: 9552: 9548: 9545: 9542: 9539: 9536: 9533: 9530: 9525: 9522: 9518: 9514: 9511: 9491: 9488: 9485: 9482: 9479: 9476: 9464: 9463: 9462: 9461: 9449: 9446: 9443: 9438: 9435: 9431: 9427: 9424: 9421: 9418: 9415: 9412: 9407: 9403: 9389: 9388: 9387: 9376: 9373: 9370: 9365: 9361: 9357: 9354: 9351: 9347: 9343: 9340: 9337: 9334: 9331: 9326: 9322: 9318: 9314: 9291: 9288: 9285: 9274: 9262: 9259: 9256: 9253: 9250: 9245: 9242: 9238: 9217: 9197: 9177: 9157: 9137: 9117: 9097: 9092: 9088: 9084: 9081: 9078: 9073: 9069: 9048: 9033: 9032: 9020: 9000: 8995: 8991: 8987: 8967: 8947: 8927: 8924: 8921: 8901: 8898: 8895: 8870: 8867: 8864: 8837: 8833: 8810: 8806: 8785: 8780: 8776: 8772: 8752: 8749: 8746: 8726: 8706: 8691: 8690: 8689: 8678: 8675: 8672: 8664: 8661: 8658: 8655: 8647: 8642: 8638: 8615: 8612: 8609: 8606: 8603: 8583: 8571: 8570: 8550: 8530: 8508: 8504: 8481: 8477: 8456: 8436: 8416: 8405: 8404: 8403: 8392: 8389: 8386: 8383: 8378: 8374: 8370: 8367: 8364: 8361: 8358: 8355: 8350: 8346: 8341: 8338: 8335: 8332: 8329: 8326: 8323: 8320: 8298: 8278: 8258: 8236: 8232: 8215: 8214: 8202: 8199: 8196: 8193: 8190: 8187: 8184: 8181: 8176: 8172: 8168: 8165: 8162: 8159: 8154: 8150: 8129: 8109: 8089: 8086: 8083: 8063: 8060: 8057: 8054: 8049: 8045: 8041: 8038: 8035: 8032: 8029: 8007: 8003: 7986: 7983: 7982: 7981: 7955: 7931: 7925: 7881: 7878: 7877: 7876: 7871:is adjoint to 7857:ideal quotient 7842: 7755: 7744: 7682: 7679: 7678: 7677: 7655: 7647: 7600: 7579:continuous map 7572: 7511: 7451: 7432:discrete space 7403: 7400: 7399: 7398: 7384: 7349:vector bundles 7338: 7323:abelianization 7299:Abelianization 7296: 7284: 7277: 7268: 7260: 7249: 7240: 7218:group of units 7195: 7173: 7148:. The functor 7120:is a ring and 7108: 7057:tensor product 7022: 7006: 6993:disjoint union 6991:by taking the 6974: 6946: 6943: 6941: 6938: 6937: 6936: 6916: 6915: 6879: 6872: 6829: 6822: 6775: 6772: 6771: 6770: 6765: 6764: 6707: 6701: 6694: 6686: 6677: 6668: 6661: 6654: 6643: 6636: 6629: 6622: 6615: 6608: 6594: 6593: 6577: 6576: 6560: 6553: 6546: 6539: 6505: 6498: 6490: 6484: 6443: 6440: 6424: 6421: 6388: 6383: 6379: 6375: 6372: 6342: 6339: 6335: 6315: 6314: 6302: 6299: 6292: 6287: 6283: 6279: 6276: 6271: 6266: 6263: 6260: 6257: 6248: 6245: 6241: 6235: 6230: 6227: 6199: 6196: 6193: 6190: 6187: 6184: 6179: 6175: 6130: 6127: 6123: 6078: 6073: 6069: 6065: 6062: 6043: 6042: 6031: 6028: 6019: 6016: 6012: 6006: 6001: 5998: 5995: 5992: 5985: 5980: 5976: 5972: 5969: 5964: 5959: 5956: 5929: 5926: 5923: 5920: 5917: 5914: 5909: 5905: 5878: 5875: 5872: 5869: 5866: 5863: 5860: 5857: 5854: 5773: 5770: 5767: 5764: 5761: 5758: 5753: 5749: 5712: 5707: 5703: 5699: 5696: 5693: 5690: 5662: 5659: 5656: 5653: 5650: 5647: 5642: 5638: 5580: 5577: 5574: 5571: 5568: 5565: 5560: 5556: 5542:of some group 5515: 5512: 5509: 5506: 5503: 5500: 5495: 5491: 5393: 5390: 5388: 5385: 5333:tensor product 5320: 5317: 5314: 5299:abelian groups 5295: 5294: 5254: 5251: 5211: 5208: 5205: 5202: 5199: 5150: 5147: 5143: 5116: 5112: 5089: 5064: 5059: 5047: 5046: 5028: 5025: 5021: 5017: 5014: 5009: 5005: 5001: 4998: 4995: 4992: 4990: 4986: 4983: 4979: 4975: 4974: 4971: 4966: 4962: 4958: 4955: 4952: 4947: 4944: 4940: 4936: 4933: 4931: 4927: 4924: 4920: 4916: 4915: 4885: 4884: 4869: 4866: 4863: 4860: 4857: 4854: 4851: 4849: 4845: 4841: 4837: 4836: 4833: 4830: 4827: 4824: 4821: 4818: 4815: 4813: 4809: 4805: 4801: 4800: 4763: 4760: 4757: 4737: 4734: 4731: 4728: 4725: 4722: 4719: 4716: 4713: 4681:respectively. 4668: 4662: 4659: 4658: 4647: 4640: 4637: 4632: 4627: 4624: 4621: 4614: 4611: 4606: 4601: 4591: 4580: 4573: 4570: 4565: 4560: 4557: 4554: 4547: 4544: 4539: 4534: 4508: 4507: 4492: 4489: 4486: 4480: 4475: 4471: 4468: 4466: 4464: 4461: 4460: 4454: 4449: 4445: 4442: 4439: 4436: 4433: 4431: 4429: 4426: 4425: 4368: 4365: 4363:) is similar. 4344: 4323:) is given by 4312: 4300: 4197: 4183: 4128: 4127: 4116: 4113: 4110: 4107: 4104: 4101: 4096: 4091: 4088: 4085: 4080: 4077: 4074: 4071: 4068: 4065: 4062: 4057: 4052: 4049: 4046: 4041: 4036: 4033: 4030: 4026: 4011: 4010: 3998: 3995: 3992: 3989: 3986: 3983: 3978: 3973: 3970: 3967: 3962: 3959: 3956: 3953: 3950: 3947: 3944: 3939: 3934: 3931: 3928: 3923: 3920: 3858: 3855: 3838: 3818: 3798: 3778: 3755: 3731: 3711: 3702:a morphism in 3690: 3687: 3683: 3680: 3677: 3674: 3654: 3651: 3645: 3642: 3637: 3633: 3628: 3624: 3620: 3617: 3614: 3611: 3608: 3605: 3602: 3599: 3579: 3576: 3573: 3570: 3567: 3547: 3516: 3513: 3508: 3504: 3500: 3497: 3494: 3491: 3488: 3468: 3465: 3462: 3459: 3456: 3453: 3450: 3447: 3427: 3424: 3421: 3418: 3415: 3412: 3409: 3406: 3386: 3366: 3346: 3343: 3340: 3337: 3334: 3331: 3328: 3325: 3322: 3319: 3314: 3310: 3289: 3269: 3266: 3263: 3260: 3240: 3220: 3200: 3180: 3156: 3136: 3112: 3109: 3106: 3103: 3100: 3077: 3053: 3033: 3013: 3010: 3006: 3003: 2999: 2996: 2973: 2970: 2965: 2961: 2958: 2955: 2952: 2949: 2946: 2943: 2940: 2937: 2934: 2931: 2926: 2922: 2901: 2898: 2895: 2892: 2889: 2869: 2831: 2828: 2825: 2822: 2819: 2816: 2813: 2808: 2804: 2783: 2780: 2777: 2774: 2771: 2768: 2765: 2762: 2742: 2739: 2736: 2733: 2730: 2727: 2724: 2721: 2701: 2681: 2661: 2658: 2655: 2652: 2649: 2646: 2643: 2640: 2637: 2634: 2629: 2625: 2604: 2584: 2581: 2578: 2575: 2555: 2535: 2515: 2495: 2471: 2451: 2427: 2424: 2421: 2418: 2415: 2403: 2400: 2366:, the letters 2320: 2317: 2312: 2311: 2308: 2301: 2300:optimizations. 2292: 2289: 2226: 2223: 2148:most efficient 2141:most efficient 2127:is initial in 2116: 2109: 2102: 2095: 2088: 2077: 2063:comma category 2058: 2054: 2050: 2043: 2036: 2025: 2010: 1999: 1946:most efficient 1934:initial object 1907:most efficient 1888:most efficient 1868:most efficient 1863: 1860: 1840: 1834: 1831: 1818: 1815: 1812: 1809: 1806: 1803: 1800: 1797: 1794: 1791: 1788: 1785: 1782: 1762: 1742: 1724: 1723: 1712: 1709: 1706: 1703: 1666: 1660: 1657: 1654: 1632: 1609: 1603: 1600: 1597: 1575: 1555: 1535: 1512: 1492: 1472: 1448: 1428: 1404: 1384: 1360: 1357: 1337: 1334: 1331: 1328: 1325: 1322: 1316: 1310: 1307: 1304: 1282: 1261: 1241: 1215: 1204: 1203: 1192: 1189: 1186: 1183: 1180: 1177: 1171: 1165: 1162: 1159: 1154: 1151: 1148: 1145: 1142: 1139: 1136: 1130: 1124: 1121: 1118: 1113: 1108: 1105: 1101: 1061: 1058: 1043: 1019: 991: 967: 942: 939: 936: 915: 889: 868: 842: 817: 795: 774: 771: 768: 764: 759: 754: 751: 748: 745: 742: 739: 736: 731: 708: 705: 702: 698: 693: 688: 685: 682: 679: 676: 673: 670: 665: 641: 619: 592: 588: 585: 581: 576: 571: 568: 565: 562: 559: 556: 553: 548: 519: 515: 512: 508: 503: 498: 495: 492: 489: 486: 483: 480: 475: 453: 433: 418: 417: 406: 403: 400: 397: 394: 391: 385: 379: 376: 373: 368: 365: 362: 359: 356: 353: 350: 344: 338: 335: 332: 301: 279: 257: 235: 224: 223: 210: 205: 200: 195: 192: 170: 165: 160: 155: 152: 123: 99: 26: 9: 6: 4: 3: 2: 16920: 16909: 16906: 16905: 16903: 16888: 16885: 16883: 16882:Representable 16880: 16878: 16875: 16873: 16870: 16868: 16865: 16863: 16860: 16858: 16855: 16853: 16850: 16848: 16845: 16843: 16840: 16838: 16835: 16833: 16830: 16828: 16825: 16823: 16820: 16819: 16816: 16811: 16804: 16799: 16797: 16792: 16790: 16785: 16784: 16781: 16769: 16761: 16759: 16751: 16749: 16741: 16740: 16737: 16723: 16720: 16718: 16715: 16713: 16709: 16705: 16701: 16699: 16697: 16690: 16688: 16685: 16683: 16680: 16679: 16677: 16674: 16670: 16660: 16657: 16654: 16650: 16647: 16646: 16644: 16642: 16634: 16628: 16625: 16623: 16620: 16618: 16615: 16613: 16612:Tetracategory 16610: 16608: 16605: 16602: 16601:pseudofunctor 16598: 16595: 16594: 16592: 16590: 16582: 16579: 16575: 16570: 16567: 16565: 16562: 16560: 16557: 16555: 16552: 16550: 16547: 16545: 16542: 16540: 16537: 16535: 16532: 16530: 16526: 16520: 16519: 16516: 16512: 16507: 16503: 16498: 16480: 16477: 16475: 16472: 16470: 16467: 16465: 16462: 16460: 16457: 16455: 16452: 16450: 16447: 16445: 16444:Free category 16442: 16441: 16439: 16435: 16428: 16427:Vector spaces 16424: 16421: 16418: 16414: 16411: 16409: 16406: 16404: 16401: 16399: 16396: 16394: 16391: 16389: 16386: 16385: 16383: 16381: 16377: 16367: 16364: 16362: 16359: 16355: 16352: 16351: 16350: 16347: 16345: 16342: 16340: 16337: 16336: 16334: 16332: 16328: 16322: 16321:Inverse limit 16319: 16317: 16314: 16310: 16307: 16306: 16305: 16302: 16300: 16297: 16295: 16292: 16291: 16289: 16287: 16283: 16280: 16278: 16274: 16268: 16265: 16263: 16260: 16258: 16255: 16253: 16250: 16248: 16247:Kan extension 16245: 16243: 16240: 16238: 16235: 16233: 16230: 16228: 16225: 16223: 16220: 16218: 16215: 16211: 16208: 16206: 16203: 16201: 16198: 16196: 16193: 16191: 16188: 16186: 16183: 16182: 16181: 16178: 16177: 16175: 16171: 16167: 16160: 16156: 16152: 16145: 16140: 16138: 16133: 16131: 16126: 16125: 16122: 16115: 16111: 16107: 16103: 16099: 16095: 16092: 16089: 16088:Eugenia Cheng 16085: 16081: 16076: 16075: 16065: 16061: 16057: 16055:0-387-98403-8 16051: 16047: 16043: 16042: 16037: 16033: 16029: 16025: 16021: 16019:0-471-60922-6 16015: 16008: 16007: 16001: 16000: 15989: 15986: 15985:0-387-97710-4 15982: 15978: 15974: 15969: 15961: 15957: 15951: 15944: 15940: 15936: 15932: 15927: 15919: 15915: 15910: 15905: 15901: 15897: 15896: 15888: 15881: 15872: 15871:q-alg/9609018 15867: 15860: 15856: 15848: 15846: 15842: 15837: 15835: 15831: 15827: 15823: 15819: 15815: 15811: 15791: 15783: 15779: 15775: 15772: 15765: 15764: 15763: 15746: 15732: 15728: 15725: 15718: 15717: 15716: 15714: 15710: 15674: 15671: 15664: 15663: 15662: 15660: 15656: 15652: 15648: 15644: 15634: 15632: 15628: 15623: 15618: 15614: 15610: 15605: 15600: 15593: 15589: 15585: 15580: 15575: 15571: 15567: 15563: 15556: 15551: 15546: 15542: 15538: 15531: 15527: 15523: 15518: 15516: 15512: 15508: 15504: 15501:If a functor 15494: 15492: 15488: 15482: 15480: 15476: 15472: 15468: 15464: 15460: 15456: 15452: 15448: 15444: 15432:Relationships 15429: 15427: 15423: 15419: 15415: 15410: 15408: 15404: 15400: 15378: 15375: 15372: 15369: 15343: 15337: 15334: 15331: 15328: 15302: 15297: 15294: 15291: 15279: 15278: 15277: 15275: 15271: 15267: 15263: 15259: 15255: 15251: 15247: 15243: 15239: 15235: 15222: 15218: 15215: 15211: 15208: 15204: 15201: 15197: 15196: 15195: 15192: 15190: 15186: 15182: 15178: 15174: 15170: 15160: 15158: 15154: 15149: 15147: 15124: 15113: 15106: 15102: 15097: 15094: 15088: 15084: 15081: 15077: 15073: 15068: 15064: 15061: 15056: 15053: 15049: 15040: 15037: 15033: 15030: 15026: 15023: 15015: 15012: 15008: 15004: 15001: 14996: 14990: 14987: 14982: 14979: 14971: 14968: 14963: 14950: 14937: 14936: 14935: 14933: 14929: 14910: 14907: 14901: 14898: 14895: 14892: 14888: 14885: 14877: 14876: 14875: 14858: 14852: 14849: 14845: 14842: 14838: 14835: 14828: 14827: 14826: 14824: 14820: 14816: 14812: 14808: 14804: 14800: 14796: 14786: 14772: 14752: 14725: 14717: 14714: 14710: 14706: 14701: 14698: 14694: 14687: 14684: 14681: 14679: 14673: 14670: 14662: 14659: 14653: 14650: 14647: 14641: 14639: 14633: 14630: 14618: 14617: 14616: 14614: 14610: 14602: 14598: 14594: 14591: 14587: 14583: 14582: 14581: 14579: 14575: 14571: 14567: 14563: 14559: 14555: 14551: 14546: 14544: 14540: 14536: 14532: 14528: 14524: 14520: 14516: 14504: 14500: 14496: 14493: 14490: 14486: 14483: 14482: 14481: 14467: 14461: 14458: 14455: 14447: 14442: 14436: 14432: 14427: 14423: 14419: 14416: 14415: 14414: 14408: 14400: 14396: 14392: 14388: 14384: 14381: 14380: 14379: 14373: 14369: 14365: 14361: 14358: 14357: 14356: 14354: 14353: 14345: 14341: 14332: 14328: 14324: 14320: 14315: 14311: 14308: 14307: 14306: 14304: 14300: 14296: 14292: 14288: 14284: 14280: 14276: 14272: 14268: 14264: 14258: 14226: 14223: 14219: 14215: 14207: 14203: 14196: 14193: 14188: 14185: 14181: 14173: 14170: 14165: 14159: 14150: 14146: 14142: 14122: 14118: 14111: 14108: 14103: 14100: 14096: 14092: 14087: 14084: 14080: 14072: 14071: 14067: 14062: 14056: 14052: 14046: 14041: 14037: 14034:Substituting 14033: 14032: 14028: 14024: 14020: 14016: 14012: 14008: 14004: 13983: 13977: 13974: 13969: 13965: 13961: 13955: 13947: 13944: 13939: 13936: 13933: 13919: 13915: 13911: 13905: 13899: 13896: 13890: 13882: 13879: 13876: 13860: 13859: 13855: 13852: 13848: 13844: 13839: 13834: 13830: 13826: 13822: 13817: 13812: 13808: 13790: 13787: 13784: 13781: 13778: 13770: 13754: 13749: 13746: 13742: 13733: 13729: 13710: 13707: 13704: 13701: 13698: 13690: 13674: 13666: 13663: 13659: 13650: 13647: 13644: 13641: 13633: 13628: 13624: 13615: 13597: 13594: 13591: 13588: 13585: 13577: 13561: 13556: 13553: 13549: 13540: 13536: 13517: 13514: 13511: 13508: 13505: 13497: 13481: 13473: 13470: 13466: 13457: 13454: 13449: 13446: 13443: 13440: 13432: 13427: 13423: 13414: 13413: 13412: 13394: 13391: 13388: 13385: 13379: 13376: 13373: 13363: 13362: 13361: 13359: 13354: 13349: 13344: 13339: 13335: 13331: 13327: 13323: 13319: 13306: 13288: 13285: 13282: 13279: 13274: 13271: 13267: 13263: 13261: 13253: 13250: 13245: 13242: 13238: 13234: 13226: 13222: 13215: 13212: 13210: 13200: 13196: 13192: 13186: 13180: 13177: 13174: 13166: 13162: 13155: 13152: 13150: 13145: 13128: 13127: 13122: 13112: 13107: 13102: 13097: 13093: 13092: 13088: 13070: 13067: 13062: 13059: 13055: 13051: 13048: 13045: 13043: 13030: 13026: 13019: 13016: 13011: 13008: 13004: 13000: 12997: 12994: 12992: 12979: 12975: 12968: 12965: 12959: 12953: 12950: 12947: 12942: 12938: 12934: 12932: 12927: 12910: 12909: 12904: 12899: 12892: 12886: 12881: 12877: 12876: 12872: 12851: 12845: 12842: 12837: 12833: 12829: 12823: 12815: 12812: 12809: 12795: 12791: 12787: 12781: 12775: 12772: 12766: 12758: 12755: 12752: 12736: 12735: 12731: 12727: 12723: 12719: 12715: 12711: 12707: 12706: 12705: 12703: 12698: 12693: 12688: 12683: 12668: 12661: 12657: 12653: 12649: 12645: 12641: 12637: 12627: 12618: 12611: 12603: 12596: 12587: 12583: 12579: 12569: 12560: 12556: 12549: 12545: 12537: 12528: 12524: 12520: 12513: 12509: 12502: 12498: 12492: 12486: 12478: 12471: 12463: 12456: 12452: 12445: 12438: 12434: 12430: 12423: 12416: 12412: 12405: 12398: 12394: 12390: 12386: 12377: 12373: 12369: 12365: 12361: 12357: 12352: 12348: 12342: 12338: 12332: 12327: 12323: 12319: 12315: 12311: 12307: 12303: 12302: 12300: 12295: 12290: 12285: 12280: 12275: 12271: 12267: 12264: 12260: 12254: 12249: 12244: 12242:on morphisms. 12241: 12234: 12230: 12223: 12219: 12215: 12211: 12203: 12198: 12188: 12179: 12171: 12167: 12160: 12153: 12149: 12145: 12142: 12138: 12134: 12130: 12126: 12121: 12116: 12112: 12107: 12102: 12098: 12094: 12090: 12086: 12085: 12083: 12079: 12075: 12071: 12070: 12069: 12067: 12063: 12059: 12049: 12047: 12043: 12036: 12032: 12028: 12024: 12019: 12014: 12010: 12008: 12004: 12000: 11996: 11991: 11986: 11982: 11981: 11960: 11957: 11953: 11949: 11941: 11937: 11930: 11927: 11925: 11918: 11915: 11911: 11898: 11894: 11887: 11884: 11879: 11876: 11872: 11868: 11866: 11859: 11856: 11852: 11840: 11839: 11835: 11834: 11809: 11803: 11800: 11797: 11794: 11786: 11766: 11759: 11755: 11751: 11749: 11739: 11736: 11732: 11723: 11720: 11717: 11714: 11699: 11696: 11690: 11684: 11681: 11673: 11653: 11646: 11642: 11638: 11636: 11626: 11623: 11619: 11610: 11607: 11602: 11599: 11596: 11593: 11575: 11569: 11566: 11563: 11555: 11535: 11528: 11524: 11520: 11514: 11508: 11505: 11503: 11495: 11487: 11484: 11481: 11473: 11470: 11460: 11457: 11451: 11445: 11437: 11417: 11409: 11403: 11400: 11395: 11391: 11387: 11385: 11377: 11369: 11366: 11361: 11358: 11355: 11347: 11344: 11333: 11332: 11328: 11327: 11326: 11320: 11311: 11307: 11303: 11299: 11295: 11290: 11286: 11281: 11277: 11273: 11269: 11265: 11261: 11257: 11253: 11249: 11244: 11240: 11235: 11231: 11227: 11223: 11219: 11215: 11214: 11213: 11212: 11211: 11209: 11205: 11201: 11197: 11190: 11186: 11181: 11176: 11174: 11169: 11164: 11160: 11156: 11153: 11148: 11143: 11138: 11133: 11129: 11127: 11126:right adjoint 11123: 11119: 11115: 11111: 11109: 11105: 11101: 11097: 11094: 11090: 11089: 11088: 11086: 11082: 11078: 11073: 11065: 11051: 10987: 10984: 10956: 10942: 10939: 10912: 10908: 10901: 10898: 10895: 10887: 10882: 10866: 10863: 10859: 10855: 10852: 10846: 10843: 10837: 10834: 10831: 10797: 10794: 10791: 10771: 10768: 10765: 10762: 10759: 10753: 10747: 10716: 10663: 10654: 10637: 10631: 10625: 10622: 10616: 10613: 10610: 10587: 10567: 10564: 10561: 10558: 10555: 10549: 10543: 10512: 10510: 10498: 10496: 10491: 10490: 10434: 10414: 10391: 10368: 10348: 10328: 10323: 10310: 10294: 10287: 10284: 10281: 10277: 10265: 10254: 10251: 10247: 10243: 10240: 10231: 10228: 10225: 10222: 10216: 10213: 10208: 10196: 10195: 10193: 10172: 10164: 10160: 10156: 10150: 10147: 10144: 10136: 10132: 10127: 10124: 10118: 10115: 10112: 10109: 10098: 10082: 10076: 10070: 10067: 10060: 10057: 10054: 10050: 10038: 10027: 10024: 10020: 10016: 10013: 10004: 10001: 9998: 9995: 9989: 9986: 9981: 9969: 9968: 9951: 9945: 9925: 9922: 9919: 9899: 9896: 9887: 9876: 9873: 9869: 9848: 9826: 9801: 9779: 9775: 9754: 9751: 9745: 9739: 9716: 9708: 9705: 9701: 9697: 9694: 9674: 9671: 9665: 9659: 9636: 9628: 9625: 9621: 9617: 9614: 9607:we also have 9594: 9591: 9588: 9565: 9557: 9554: 9550: 9546: 9537: 9531: 9523: 9520: 9516: 9512: 9509: 9489: 9486: 9480: 9474: 9466: 9465: 9444: 9436: 9433: 9429: 9425: 9422: 9416: 9413: 9410: 9405: 9393: 9392: 9390: 9374: 9368: 9363: 9359: 9355: 9352: 9345: 9341: 9335: 9332: 9329: 9324: 9312: 9304: 9303: 9289: 9286: 9283: 9275: 9260: 9257: 9251: 9243: 9240: 9236: 9215: 9195: 9175: 9155: 9135: 9115: 9095: 9090: 9086: 9082: 9079: 9076: 9071: 9067: 9046: 9038: 9035: 9034: 9018: 8998: 8993: 8989: 8985: 8965: 8945: 8925: 8922: 8919: 8896: 8865: 8835: 8808: 8783: 8778: 8774: 8770: 8750: 8744: 8724: 8704: 8696: 8692: 8673: 8656: 8645: 8640: 8636: 8628: 8627: 8613: 8607: 8604: 8601: 8581: 8573: 8572: 8568: 8564: 8548: 8528: 8506: 8502: 8479: 8475: 8454: 8434: 8414: 8406: 8384: 8376: 8372: 8368: 8362: 8359: 8356: 8348: 8344: 8339: 8336: 8330: 8327: 8324: 8321: 8311: 8310: 8296: 8276: 8256: 8234: 8230: 8221: 8217: 8216: 8197: 8191: 8188: 8182: 8174: 8170: 8166: 8160: 8152: 8148: 8127: 8107: 8087: 8084: 8081: 8055: 8047: 8043: 8039: 8036: 8030: 8027: 8005: 8001: 7992: 7989: 7988: 7979: 7975: 7971: 7967: 7963: 7959: 7956: 7953: 7949: 7945: 7941: 7937: 7930:The functor Ο€ 7929: 7926: 7923: 7919: 7915: 7911: 7907: 7903: 7899: 7895: 7891: 7887: 7886:Equivalences. 7884: 7883: 7874: 7870: 7866: 7862: 7858: 7855:instead: the 7854: 7850: 7846: 7843: 7840: 7836: 7832: 7828: 7824: 7820: 7816: 7812: 7808: 7804: 7800: 7796: 7792: 7788: 7784: 7780: 7776: 7772: 7768: 7764: 7760: 7756: 7753: 7749: 7745: 7742: 7741: 7740: 7737: 7735: 7731: 7727: 7722: 7720: 7716: 7715:Galois theory 7712: 7708: 7704: 7700: 7696: 7692: 7688: 7675: 7671: 7667: 7663: 7662:Stone duality 7659: 7656: 7653: 7646: 7642: 7638: 7637: 7632: 7628: 7624: 7620: 7619: 7614: 7610: 7606: 7599: 7595: 7591: 7587: 7583: 7580: 7576: 7573: 7570: 7566: 7562: 7558: 7554: 7550: 7546: 7542: 7538: 7534: 7530: 7526: 7523: 7519: 7515: 7512: 7509: 7505: 7501: 7497: 7493: 7489: 7485: 7481: 7477: 7474: 7470: 7466: 7462: 7459: 7455: 7452: 7449: 7445: 7442:creating the 7441: 7437: 7433: 7429: 7425: 7421: 7417: 7413: 7409: 7406: 7405: 7396: 7392: 7388: 7385: 7382: 7378: 7374: 7370: 7366: 7362: 7361:abelian group 7358: 7354: 7350: 7346: 7342: 7339: 7336: 7332: 7328: 7324: 7320: 7316: 7312: 7308: 7304: 7300: 7297: 7294: 7290: 7283: 7276: 7272: 7269: 7266: 7259: 7255: 7248: 7244: 7241: 7238: 7234: 7230: 7226: 7223: 7219: 7215: 7211: 7207: 7203: 7199: 7196: 7193: 7189: 7185: 7181: 7176: 7171: 7167: 7164:, defined by 7163: 7159: 7155: 7151: 7147: 7143: 7139: 7135: 7131: 7127: 7123: 7119: 7115: 7113: 7109: 7106: 7102: 7098: 7094: 7090: 7086: 7082: 7078: 7074: 7070: 7066: 7062: 7058: 7054: 7050: 7046: 7042: 7038: 7034: 7030: 7026: 7023: 7020: 7004: 6997: 6994: 6990: 6986: 6982: 6980: 6975: 6972: 6968: 6964: 6960: 6956: 6954: 6949: 6948: 6934: 6930: 6926: 6925:vector spaces 6922: 6918: 6917: 6913: 6909: 6905: 6901: 6897: 6893: 6890:) to back to 6889: 6885: 6878: 6871: 6867: 6863: 6859: 6855: 6851: 6847: 6843: 6839: 6835: 6828: 6821: 6817: 6814: 6811: 6807: 6803: 6800: 6799: 6798: 6796: 6792: 6788: 6784: 6780: 6767: 6766: 6762: 6758: 6754: 6750: 6746: 6742: 6738: 6735: 6731: 6727: 6723: 6719: 6715: 6710: 6706: 6700: 6693: 6689: 6685: 6680: 6676: 6671: 6667: 6660: 6653: 6649: 6642: 6635: 6628: 6621: 6614: 6607: 6603: 6599: 6596: 6595: 6591: 6587: 6583: 6579: 6578: 6574: 6570: 6566: 6559: 6552: 6545: 6538: 6534: 6530: 6526: 6522: 6518: 6514: 6511: 6504: 6497: 6493: 6483: 6479: 6475: 6472:Let Ξ  : 6471: 6468: 6467: 6466: 6464: 6460: 6456: 6452: 6448: 6439: 6437: 6436:free functors 6433: 6429: 6420: 6418: 6414: 6410: 6406: 6402: 6381: 6377: 6370: 6362: 6358: 6340: 6337: 6333: 6324: 6320: 6300: 6297: 6285: 6281: 6274: 6269: 6264: 6261: 6258: 6255: 6246: 6243: 6239: 6233: 6228: 6225: 6217: 6216: 6215: 6213: 6197: 6194: 6191: 6188: 6185: 6182: 6177: 6173: 6164: 6160: 6158: 6154: 6150: 6146: 6128: 6125: 6121: 6112: 6108: 6104: 6100: 6096: 6092: 6071: 6067: 6060: 6052: 6048: 6029: 6026: 6017: 6014: 6010: 6004: 5999: 5996: 5993: 5990: 5978: 5974: 5967: 5962: 5957: 5954: 5947: 5946: 5945: 5943: 5927: 5924: 5921: 5918: 5915: 5912: 5907: 5903: 5894: 5890: 5876: 5873: 5870: 5867: 5861: 5858: 5855: 5844: 5840: 5838: 5834: 5829: 5825: 5821: 5817: 5813: 5809: 5805: 5801: 5799: 5795: 5791: 5787: 5771: 5765: 5762: 5759: 5756: 5751: 5747: 5738: 5734: 5730: 5726: 5705: 5701: 5697: 5694: 5691: 5680: 5676: 5660: 5654: 5651: 5648: 5645: 5640: 5636: 5627: 5623: 5619: 5615: 5611: 5607: 5605: 5604: 5598: 5594: 5578: 5575: 5572: 5566: 5563: 5558: 5554: 5545: 5541: 5537: 5533: 5529: 5513: 5510: 5507: 5501: 5498: 5493: 5489: 5481:. Let   5480: 5477:generated by 5476: 5472: 5468: 5465:For each set 5464: 5460: 5458: 5454: 5450: 5446: 5442: 5438: 5434: 5430: 5426: 5422: 5418: 5417: 5412: 5411: 5406: 5401: 5399: 5384: 5382: 5378: 5374: 5370: 5366: 5362: 5358: 5354: 5350: 5346: 5342: 5338: 5334: 5318: 5315: 5312: 5304: 5300: 5292: 5288: 5284: 5280: 5276: 5272: 5268: 5267: 5266: 5264: 5260: 5250: 5248: 5244: 5240: 5236: 5231: 5229: 5225: 5209: 5206: 5203: 5200: 5197: 5189: 5185: 5181: 5172: 5168: 5166: 5148: 5145: 5141: 5132: 5114: 5110: 5057: 5026: 5023: 5019: 5015: 5007: 5003: 4996: 4993: 4991: 4984: 4981: 4977: 4964: 4960: 4953: 4950: 4945: 4942: 4938: 4934: 4932: 4925: 4922: 4918: 4906: 4905: 4904: 4902: 4898: 4894: 4890: 4867: 4864: 4861: 4858: 4855: 4852: 4850: 4843: 4839: 4831: 4828: 4825: 4822: 4819: 4816: 4814: 4807: 4803: 4791: 4790: 4789: 4788: 4784: 4780: 4775: 4761: 4758: 4755: 4735: 4732: 4729: 4726: 4720: 4717: 4714: 4703: 4702: 4698: 4693: 4692: 4688: 4682: 4680: 4676: 4671: 4665: 4645: 4638: 4635: 4630: 4625: 4622: 4619: 4612: 4609: 4604: 4599: 4592: 4578: 4571: 4568: 4563: 4558: 4555: 4552: 4545: 4542: 4537: 4532: 4525: 4524: 4523: 4521: 4517: 4513: 4490: 4487: 4473: 4469: 4467: 4462: 4447: 4440: 4437: 4434: 4432: 4427: 4416: 4415: 4414: 4413: 4409: 4405: 4401: 4397: 4393: 4389: 4386: 4382: 4378: 4374: 4364: 4362: 4358: 4354: 4350: 4342: 4338: 4326: 4322: 4318: 4310: 4306: 4298: 4294: 4285: 4281: 4279: 4275: 4270: 4266: 4263: 4259: 4254: 4249: 4245: 4241: 4237: 4233: 4229: 4225: 4220: 4216: 4211: 4205: 4200: 4191: 4186: 4179: 4174: 4170: 4168: 4167: 4163: 4158: 4157: 4153: 4147: 4145: 4141: 4137: 4133: 4111: 4108: 4105: 4102: 4094: 4072: 4069: 4066: 4063: 4055: 4039: 4034: 4031: 4028: 4016: 4015: 4014: 3993: 3990: 3987: 3984: 3976: 3954: 3951: 3948: 3945: 3937: 3921: 3911: 3910: 3909: 3908: 3903: 3899: 3895: 3890: 3886: 3882: 3879: 3875: 3871: 3867: 3865: 3854: 3850: 3836: 3816: 3796: 3776: 3767: 3753: 3745: 3744:right adjoint 3729: 3709: 3688: 3685: 3678: 3675: 3672: 3652: 3649: 3643: 3640: 3635: 3631: 3626: 3622: 3618: 3609: 3603: 3597: 3577: 3571: 3568: 3565: 3545: 3532: 3528: 3514: 3511: 3506: 3502: 3498: 3492: 3486: 3466: 3457: 3451: 3448: 3445: 3422: 3416: 3410: 3407: 3404: 3384: 3364: 3338: 3332: 3326: 3320: 3317: 3312: 3308: 3287: 3264: 3258: 3238: 3218: 3198: 3178: 3170: 3154: 3134: 3126: 3110: 3104: 3101: 3098: 3089: 3075: 3067: 3051: 3031: 3011: 3004: 3001: 2997: 2994: 2971: 2968: 2963: 2959: 2956: 2953: 2944: 2938: 2932: 2929: 2924: 2920: 2899: 2893: 2890: 2887: 2867: 2854: 2850: 2848: 2843: 2829: 2826: 2820: 2814: 2811: 2806: 2802: 2778: 2772: 2766: 2763: 2760: 2740: 2731: 2725: 2722: 2719: 2699: 2679: 2659: 2647: 2641: 2635: 2632: 2627: 2623: 2602: 2579: 2573: 2553: 2533: 2513: 2493: 2485: 2469: 2449: 2441: 2425: 2419: 2416: 2413: 2399: 2397: 2393: 2389: 2385: 2381: 2377: 2373: 2369: 2365: 2361: 2357: 2353: 2348: 2346: 2342: 2338: 2334: 2330: 2326: 2316: 2309: 2306: 2302: 2298: 2297: 2296: 2288: 2286: 2282: 2278: 2274: 2269: 2267: 2263: 2259: 2255: 2251: 2247: 2242: 2240: 2236: 2232: 2222: 2220: 2216: 2212: 2207: 2205: 2201: 2197: 2193: 2189: 2185: 2181: 2177: 2173: 2169: 2165: 2161: 2157: 2153: 2149: 2144: 2142: 2138: 2134: 2130: 2126: 2122: 2115: 2108: 2101: 2094: 2091:implies that 2087: 2083: 2076: 2072: 2068: 2064: 2049: 2042: 2035: 2031: 2024: 2020: 2017:of the form ( 2016: 2009: 2005: 1998: 1994: 1990: 1986: 1982: 1978: 1974: 1970: 1966: 1962: 1957: 1955: 1951: 1947: 1943: 1939: 1935: 1931: 1926: 1924: 1920: 1916: 1912: 1908: 1903: 1901: 1897: 1893: 1889: 1885: 1881: 1877: 1873: 1869: 1859: 1857: 1848: 1847: 1839: 1830: 1813: 1810: 1807: 1804: 1798: 1792: 1789: 1786: 1783: 1760: 1740: 1733: 1729: 1728:Hilbert space 1710: 1707: 1704: 1701: 1694: 1693: 1692: 1690: 1686: 1681: 1630: 1573: 1553: 1533: 1524: 1510: 1490: 1483:. (Note that 1470: 1462: 1461:right adjoint 1446: 1426: 1418: 1402: 1382: 1374: 1371:is the right 1358: 1355: 1332: 1329: 1326: 1323: 1280: 1272: 1259: 1239: 1229: 1213: 1187: 1184: 1181: 1178: 1152: 1146: 1143: 1140: 1137: 1111: 1106: 1103: 1099: 1091: 1090: 1089: 1087: 1083: 1079: 1075: 1074: 1069: 1068: 1057: 1007: 954: 940: 937: 934: 926: 913: 903: 887: 879: 866: 856: 840: 831: 793: 752: 746: 743: 740: 737: 686: 680: 677: 674: 671: 617: 569: 563: 560: 557: 554: 496: 490: 487: 484: 481: 451: 431: 423: 401: 398: 395: 392: 366: 360: 357: 354: 351: 321: 320: 319: 317: 277: 233: 193: 190: 153: 150: 143: 142: 141: 139: 86: 85:in topology. 84: 80: 76: 72: 68: 67:right adjoint 64: 60: 56: 52: 48: 44: 37: 33: 19: 16832:Conservative 16826: 16692: 16673:Categorified 16577:n-categories 16528:Key concepts 16366:Direct limit 16349:Coequalizers 16267:Yoneda lemma 16216: 16173:Key concepts 16163:Key concepts 16082:playlist on 16039: 16005: 15987: 15976: 15968: 15959: 15950: 15938: 15926: 15899: 15893: 15880: 15859: 15838: 15833: 15828:〉 defines a 15825: 15821: 15817: 15813: 15809: 15807: 15761: 15712: 15708: 15707:is given by 15706: 15658: 15654: 15646: 15642: 15640: 15630: 15626: 15621: 15616: 15612: 15608: 15606: 15598: 15591: 15587: 15583: 15578: 15573: 15569: 15565: 15554: 15549: 15544: 15540: 15536: 15529: 15525: 15521: 15519: 15510: 15506: 15502: 15500: 15490: 15486: 15483: 15478: 15474: 15470: 15466: 15462: 15458: 15454: 15446: 15442: 15440: 15417: 15413: 15411: 15406: 15402: 15398: 15396: 15273: 15269: 15265: 15261: 15253: 15249: 15245: 15237: 15233: 15231: 15193: 15185:cocontinuous 15184: 15180: 15172: 15168: 15166: 15152: 15150: 15145: 15143: 14931: 14927: 14925: 14873: 14822: 14818: 14814: 14810: 14806: 14802: 14798: 14794: 14792: 14744: 14612: 14608: 14606: 14600: 14596: 14589: 14585: 14577: 14573: 14569: 14565: 14561: 14557: 14553: 14549: 14547: 14538: 14534: 14530: 14526: 14522: 14518: 14514: 14512: 14498: 14494: 14488: 14484: 14443: 14440: 14434: 14430: 14425: 14421: 14417: 14406: 14404: 14398: 14394: 14390: 14386: 14382: 14377: 14371: 14367: 14363: 14359: 14352:proper class 14350: 14343: 14342:come from a 14339: 14337: 14330: 14326: 14322: 14318: 14313: 14309: 14302: 14298: 14290: 14282: 14274: 14270: 14266: 14262: 14260: 14168: 14163: 14157: 14148: 14144: 14065: 14060: 14054: 14050: 14044: 14039: 14035: 14026: 14022: 14018: 14014: 14010: 14006: 13850: 13846: 13842: 13837: 13832: 13831:, and each ( 13828: 13824: 13820: 13815: 13810: 13731: 13727: 13538: 13534: 13410: 13357: 13352: 13347: 13342: 13337: 13333: 13329: 13325: 13321: 13317: 13315: 13120: 13110: 13105: 13100: 13095: 12906:), we obtain 12902: 12897: 12890: 12884: 12879: 12729: 12725: 12721: 12717: 12713: 12709: 12701: 12696: 12691: 12686: 12681: 12659: 12655: 12651: 12647: 12643: 12639: 12635: 12633: 12624: 12616: 12609: 12601: 12594: 12585: 12581: 12577: 12567: 12558: 12554: 12547: 12543: 12535: 12526: 12522: 12518: 12511: 12507: 12500: 12496: 12490: 12484: 12476: 12469: 12461: 12454: 12450: 12443: 12436: 12432: 12428: 12421: 12414: 12410: 12403: 12396: 12392: 12384: 12375: 12371: 12367: 12363: 12359: 12355: 12350: 12346: 12340: 12336: 12330: 12325: 12321: 12317: 12313: 12309: 12305: 12298: 12293: 12288: 12283: 12273: 12269: 12258: 12252: 12247: 12239: 12232: 12228: 12221: 12217: 12213: 12209: 12201: 12196: 12186: 12177: 12169: 12165: 12158: 12151: 12147: 12140: 12136: 12132: 12128: 12124: 12119: 12114: 12110: 12105: 12100: 12096: 12092: 12088: 12081: 12077: 12073: 12065: 12061: 12057: 12055: 12045: 12041: 12039: 12034: 12030: 12026: 12017: 12012: 12006: 12002: 11998: 11989: 11984: 11324: 11309: 11305: 11301: 11297: 11293: 11288: 11284: 11279: 11275: 11271: 11267: 11263: 11259: 11255: 11251: 11247: 11242: 11238: 11233: 11229: 11225: 11221: 11217: 11207: 11203: 11199: 11195: 11193: 11188: 11184: 11179: 11172: 11167: 11162: 11151: 11146: 11141: 11136: 11134:Ξ¦ : hom 11125: 11121: 11117: 11113: 11108:left adjoint 11107: 11103: 11099: 11095: 11087:consists of 11084: 11080: 11076: 11074: 11071: 11064:is "free".) 10883: 10655: 10513: 10508: 10506: 10492: 9036: 8567:topos theory 8218:The role of 7990: 7973: 7969: 7965: 7957: 7951: 7947: 7943: 7939: 7935: 7927: 7921: 7917: 7913: 7909: 7905: 7897: 7893: 7889: 7885: 7852: 7848: 7838: 7834: 7830: 7826: 7822: 7818: 7814: 7810: 7806: 7802: 7798: 7794: 7790: 7786: 7782: 7778: 7774: 7770: 7766: 7762: 7738: 7729: 7723: 7710: 7702: 7698: 7694: 7690: 7684: 7666:sober spaces 7657: 7644: 7640: 7634: 7630: 7626: 7622: 7616: 7612: 7608: 7597: 7589: 7585: 7581: 7574: 7568: 7556: 7552: 7548: 7544: 7536: 7532: 7528: 7517: 7513: 7499: 7495: 7487: 7483: 7479: 7475: 7464: 7460: 7453: 7447: 7439: 7435: 7427: 7423: 7411: 7407: 7386: 7381:model theory 7340: 7334: 7330: 7326: 7310: 7306: 7302: 7298: 7288: 7281: 7274: 7270: 7257: 7253: 7246: 7242: 7236: 7228: 7224: 7197: 7191: 7187: 7183: 7179: 7174: 7169: 7165: 7161: 7157: 7153: 7149: 7145: 7141: 7137: 7133: 7129: 7125: 7121: 7117: 7110: 7104: 7100: 7096: 7092: 7088: 7084: 7080: 7076: 7072: 7068: 7064: 7060: 7052: 7048: 7040: 7036: 7032: 7028: 7024: 7018: 6995: 6984: 6976: 6970: 6966: 6962: 6958: 6950: 6933:free product 6911: 6907: 6903: 6899: 6895: 6891: 6887: 6883: 6876: 6869: 6865: 6861: 6857: 6853: 6849: 6845: 6841: 6837: 6826: 6819: 6815: 6812: 6809: 6805: 6801: 6787:coequalizers 6777: 6760: 6756: 6752: 6748: 6744: 6740: 6736: 6733: 6729: 6721: 6717: 6713: 6708: 6704: 6698: 6691: 6687: 6683: 6678: 6674: 6669: 6665: 6658: 6651: 6647: 6640: 6633: 6626: 6619: 6612: 6605: 6601: 6597: 6572: 6568: 6564: 6557: 6550: 6543: 6536: 6532: 6528: 6524: 6520: 6512: 6509: 6502: 6495: 6488: 6481: 6477: 6473: 6469: 6445: 6428:Free objects 6426: 6416: 6412: 6408: 6404: 6400: 6360: 6356: 6322: 6318: 6316: 6211: 6162: 6161: 6156: 6152: 6148: 6144: 6110: 6106: 6102: 6098: 6094: 6090: 6050: 6046: 6044: 5941: 5892: 5891: 5842: 5841: 5836: 5832: 5827: 5823: 5819: 5815: 5811: 5807: 5803: 5802: 5797: 5793: 5789: 5785: 5736: 5732: 5728: 5724: 5678: 5674: 5628:. Let   5625: 5621: 5617: 5616:, the group 5613: 5609: 5608: 5602: 5596: 5592: 5543: 5539: 5535: 5531: 5527: 5478: 5474: 5470: 5466: 5462: 5461: 5456: 5452: 5448: 5440: 5436: 5432: 5428: 5420: 5414: 5408: 5404: 5402: 5395: 5376: 5372: 5368: 5360: 5352: 5344: 5340: 5336: 5302: 5296: 5290: 5286: 5282: 5278: 5274: 5270: 5256: 5242: 5238: 5234: 5232: 5227: 5223: 5183: 5179: 5177: 5164: 5130: 5048: 4900: 4896: 4892: 4888: 4886: 4786: 4782: 4778: 4776: 4700: 4696: 4695: 4690: 4686: 4685: 4683: 4678: 4674: 4669: 4663: 4660: 4515: 4511: 4509: 4407: 4403: 4399: 4395: 4391: 4387: 4380: 4376: 4372: 4370: 4360: 4356: 4352: 4348: 4340: 4328: 4324: 4320: 4316: 4308: 4304: 4299:) : Hom 4296: 4292: 4290: 4273: 4268: 4265: 4261: 4257: 4252: 4247: 4243: 4239: 4232:hom functors 4223: 4218: 4214: 4203: 4198: 4189: 4184: 4177: 4175: 4171: 4165: 4161: 4160: 4155: 4151: 4150: 4148: 4143: 4139: 4135: 4131: 4129: 4012: 3901: 3897: 3893: 3888: 3884: 3880: 3873: 3869: 3862: 3860: 3851: 3768: 3743: 3538:Again, this 3537: 3124: 3090: 3066:left adjoint 3065: 2859: 2844: 2439: 2405: 2395: 2391: 2387: 2383: 2379: 2375: 2371: 2367: 2363: 2359: 2355: 2351: 2349: 2344: 2340: 2336: 2332: 2328: 2324: 2322: 2313: 2304: 2294: 2284: 2280: 2276: 2272: 2270: 2265: 2261: 2257: 2253: 2249: 2245: 2243: 2238: 2234: 2230: 2228: 2218: 2214: 2210: 2208: 2203: 2199: 2195: 2191: 2187: 2183: 2179: 2175: 2171: 2167: 2163: 2159: 2155: 2151: 2147: 2145: 2140: 2136: 2132: 2128: 2124: 2120: 2113: 2106: 2099: 2092: 2085: 2081: 2074: 2070: 2066: 2047: 2040: 2033: 2029: 2022: 2018: 2007: 2003: 1996: 1992: 1988: 1984: 1980: 1976: 1972: 1968: 1964: 1960: 1958: 1953: 1945: 1942:optimization 1941: 1937: 1929: 1927: 1914: 1906: 1904: 1899: 1895: 1894:+1 for each 1891: 1887: 1871: 1867: 1865: 1852: 1844: 1837: 1725: 1688: 1684: 1682: 1525: 1460: 1417:left adjoint 1416: 1372: 1231: 1227: 1205: 1081: 1071: 1065: 1063: 955: 905: 901: 900:is called a 858: 854: 853:is called a 833:The functor 832: 786:for a fixed 610:for a fixed 419: 225: 87: 66: 63:left adjoint 62: 58: 50: 40: 16641:-categories 16617:Kan complex 16607:Tricategory 16589:-categories 16479:Subcategory 16237:Exponential 16205:Preadditive 16200:Pre-abelian 16098:Mathematica 16079:Adjunctions 15988:See page 58 15576:for which Ξ· 15547:for which Ξ΅ 15221:right exact 15146:composition 14789:Composition 13124:, we obtain 12467:, we have Ξ¦ 12117:, so that Ξ· 12011:Each pair ( 11983:Each pair ( 11282:-morphism Ξ¦ 11236:-morphism Ξ¦ 11187:called the 11171:called the 11124:called the 11106:called the 10503:Probability 10311:The subset 8220:quantifiers 7972:given by –× 7865:implication 7861:ring ideals 7124:is a right 6802:Coproducts. 6664:is a pair ( 6359:to the set 5818:to the set 5810:to a group 5398:free groups 5392:Free groups 5355:sign is an 2319:Conventions 1876:ring theory 1006:equivalence 927:. We write 43:mathematics 16659:3-category 16649:2-category 16622:∞-groupoid 16597:Bicategory 16344:Coproducts 16304:Equalizers 16210:Bicategory 16064:0906.18001 16028:0695.18001 15997:References 15939:Dialectica 15633:inverses. 15615:such that 15426:biproducts 15228:Additivity 15214:left exact 15173:continuous 14509:Uniqueness 14295:continuous 14255:See also: 14246:Properties 13616:Let   13415:Let   13350:-,-) β†’ hom 12694:-,-) β†’ hom 12503:)) = G(x) 12291:-,-) β†’ hom 11266:-morphism 11220:-morphism 11216:For every 11144:–,–) β†’ hom 11112:A functor 11077:adjunction 10884:Then, the 8695:subobjects 7863:, and the 7565:continuous 7492:loop space 7473:suspension 7357:direct sum 6921:direct sum 6852:the pair ( 6834:direct sum 6779:Coproducts 6747:β†’ 0. Then 6523:the pair ( 6455:equalizers 5469:, the set 5431:, and let 5425:free group 5259:Daniel Kan 5049:Note that 4785:) are the 4210:bifunctors 3866:adjunction 3590:such that 2260:poses the 1228:adjunction 1064:The terms 51:adjunction 16862:Forgetful 16708:Symmetric 16653:2-functor 16393:Relations 16316:Pullbacks 16102:morphisms 15789:→ 15773:μ 15744:→ 15726:η 15685:→ 15631:two-sided 15344:≅ 15288:Φ 15207:coproduct 15107:ε 15082:ε 15009:η 14969:η 14905:→ 14893:∘ 14856:→ 14839:∘ 14773:∗ 14753:∘ 14715:− 14711:τ 14707:∗ 14699:− 14695:σ 14688:∘ 14685:ε 14671:ε 14663:η 14660:∘ 14654:σ 14651:∗ 14648:τ 14631:η 14595:Ο„ : 14584:Οƒ : 14465:→ 14405:for some 14251:Existence 14220:η 14216:∘ 14204:ε 14119:η 14109:∘ 14097:ε 14005:for each 13975:∘ 13966:ε 13945:− 13930:Φ 13916:η 13912:∘ 13873:Φ 13755:∈ 13675:∈ 13638:Φ 13625:η 13562:∈ 13482:∈ 13455:− 13437:Φ 13424:ε 13392:⊣ 13380:η 13374:ε 13280:∘ 13251:∘ 13239:η 13235:∘ 13223:ε 13197:η 13193:∘ 13175:∘ 13163:ε 13143:Ψ 13140:Φ 13052:∘ 13027:η 13017:∘ 13005:ε 13001:∘ 12976:η 12966:∘ 12948:∘ 12939:ε 12925:Φ 12922:Ψ 12843:∘ 12834:ε 12806:Ψ 12792:η 12788:∘ 12749:Φ 12720:and each 12708:For each 12669:⊣ 12216:) : 12146:For each 11954:η 11950:∘ 11938:ε 11895:η 11885:∘ 11873:ε 11767:∈ 11756:η 11711:Φ 11654:∈ 11643:ε 11608:− 11590:Φ 11536:∈ 11525:η 11521:∘ 11478:Φ 11418:∈ 11401:∘ 11392:ε 11367:− 11352:Φ 11161:Ξ΅ : 11052:δ 10988:δ 10985:⊣ 10957:μ 10946:↦ 10943:μ 10909:δ 10905:↦ 10896:δ 10864:− 10856:∘ 10853:μ 10850:→ 10847:μ 10832:μ 10795:∈ 10792:μ 10629:→ 10493:See also 10475:∀ 10455:∃ 10320:∀ 10285:∈ 10252:− 10244:∈ 10235:∀ 10232:∣ 10226:∈ 10205:∀ 10161:ϕ 10157:∧ 10133:ψ 10122:∃ 10119:∣ 10113:∈ 10058:∈ 10025:− 10017:∈ 10008:∃ 10005:∣ 9999:∈ 9978:∃ 9923:∈ 9897:∩ 9874:− 9823:∃ 9780:∗ 9752:⊆ 9706:− 9698:⊆ 9672:∈ 9626:− 9618:∈ 9592:∈ 9555:− 9547:⊆ 9521:− 9513:⊆ 9502:. We see 9487:⊆ 9467:Consider 9434:− 9426:⊆ 9420:↔ 9414:⊆ 9402:∃ 9364:∗ 9342:≅ 9321:∃ 9287:⊆ 9258:⊆ 9241:− 9087:× 9072:∗ 8990:× 8923:⊂ 8832:∀ 8805:∃ 8775:× 8748:→ 8663:⟶ 8641:∗ 8611:→ 8549:∧ 8529:∩ 8503:ϕ 8476:ψ 8373:ϕ 8369:∧ 8345:ψ 8334:∃ 8331:∣ 8325:∈ 8231:ψ 8192:φ 8189:∧ 8171:ϕ 8149:ϕ 8085:⊂ 8044:ϕ 8040:∣ 8002:ϕ 7750:(cf. the 7734:Kaplansky 7434:on a set 7313:from the 7005:⊔ 6979:semigroup 6931:, by the 6836:, and if 6808: : 6791:cokernels 6769:adjoints. 6378:ε 6334:η 6282:ε 6240:η 6195:η 6192:∘ 6189:ε 6122:ε 6068:η 6011:ε 5975:η 5928:η 5922:∘ 5916:ε 5874:⊣ 5862:η 5856:ε 5769:→ 5748:ε 5702:ε 5658:→ 5637:ε 5570:→ 5555:η 5505:→ 5490:η 5316:⊗ 5313:− 5210:η 5207:∘ 5204:ε 5020:η 5016:∘ 5004:ε 4961:η 4951:∘ 4939:ε 4895:and each 4865:η 4862:∘ 4859:ε 4832:η 4826:∘ 4820:ε 4759:⊣ 4733:⊣ 4721:η 4715:ε 4639:ε 4610:η 4569:ε 4546:η 4485:→ 4463:η 4444:→ 4428:ε 4339:for each 4236:morphisms 4079:→ 4025:Φ 3994:− 3985:− 3961:→ 3955:− 3949:− 3919:Φ 3682:→ 3650:∘ 3636:η 3623:η 3619:∘ 3575:→ 3503:η 3499:∘ 3464:→ 3414:→ 3324:→ 3309:η 3108:→ 3009:→ 2964:ϵ 2960:∘ 2930:∘ 2921:ϵ 2897:→ 2812:∘ 2803:ϵ 2770:→ 2738:→ 2657:→ 2624:ϵ 2423:→ 2152:formulaic 2053:) where S 1985:morphisms 1915:formulaic 1913:, and is 1900:formulaic 1872:formulaic 1817:⟩ 1802:⟨ 1796:⟩ 1781:⟨ 1705:⊣ 1356:φ 1214:φ 1153:≅ 1100:φ 938:⊣ 763:→ 747:− 697:→ 681:− 580:→ 555:− 507:→ 485:− 367:≅ 316:bijection 204:→ 164:→ 138:covariant 16902:Category 16877:Monoidal 16847:Enriched 16842:Diagonal 16822:Additive 16768:Glossary 16748:Category 16722:n-monoid 16675:concepts 16331:Colimits 16299:Products 16252:Morphism 16195:Concrete 16190:Additive 16180:Category 16106:functors 16094:WildCats 16038:(1998). 15843:and the 15505: : 15465: : 15264: : 15248: : 15189:colimits 15103:→ 15085:′ 15074:→ 15065:′ 15057:′ 15041:′ 15027:′ 15016:′ 15005:′ 14997:→ 14991:′ 14983:′ 14972:′ 14964:→ 14889:′ 14846:′ 14674:′ 14634:′ 14533:β€², then 14517: : 14433:∈ 14420: : 14362: : 14349:, not a 14317: : 14265: : 13332: : 13320: : 12732:, define 12724: : 12712: : 12650: : 12638: : 12453: : 12435: : 12358: : 12208:and get 12150: : 12123: : 12076: : 12060: : 12021:) is an 11300: : 11270: : 11254: : 11224: : 11116: : 11098: : 10784:and any 10509:solution 10495:powerset 9732:implies 8881:back to 7978:currying 7908: : 7892: : 7845:division 7761:is that 7730:antitone 7711:antitone 7592:between 7584: : 7551: : 7531: : 7402:Topology 7345:K-theory 7305: : 7233:algebras 7152: : 7136: : 7091: : 7067: : 7027:Suppose 6860:), then 6840: : 6732: : 6728:and let 6716: : 6632: : 6611: : 6598:Kernels. 6470:Products 6447:Products 6270:→ 6234:→ 6005:→ 5963:→ 5435: : 5407: : 5387:Examples 5301:, where 5281:) = hom( 5239:terminal 4774: . 4631:→ 4605:→ 4564:→ 4538:→ 4514:and the 4410:and two 4402: : 4390: : 4385:functors 4278:commutes 4260: : 4242: : 3896: : 3883: : 3878:functors 3689:′ 3644:′ 3005:′ 2972:′ 2386: : 2268:solves. 1991:between 1950:supremum 1841:β€”  1730:idea of 1086:Mac Lane 1078:cognates 1008:between 880:, while 55:functors 16872:Logical 16837:Derived 16827:Adjoint 16810:Functor 16758:Outline 16717:n-group 16682:2-group 16637:Strict 16627:∞-topos 16423:Modules 16361:Pushout 16309:Kernels 16242:Functor 16185:Abelian 16084:YouTube 15918:1993102 15830:comonad 15560:as the 15477:, then 15405:, then 15272:, then 15200:product 14564:β€² then 13407: , 12109:) from 11993:) is a 11093:functor 9037:Example 7960:. In a 7853:adjoint 7726:duality 7670:duality 7605:sheaves 7543:. Then 7522:compact 7490:to the 7389:in the 7206:monoids 7172:) = hom 7083:. Then 7047:. Then 6945:Algebra 6929:modules 6795:colimit 6515:be the 6459:kernels 5443:be the 5361:natural 5339:), and 5253:History 5235:initial 4355:). Hom( 4311:) β†’ Hom 3864:hom-set 2305:adjoint 2279:, then 2248:is the 2198:is the 2194:. Then 2174:. Let 2139:* is a 1979:, with 1969:objects 1919:functor 1886:. The 1373:adjunct 1073:adjunct 1067:adjoint 422:natural 16887:Smooth 16704:Traced 16687:2-ring 16417:Fields 16403:Groups 16398:Magmas 16286:Limits 16062:  16052:  16026:  16016:  15983:  15916:  15637:Monads 15256:is an 15177:limits 14556:, and 14541:β€² are 14167:) for 14064:) for 12449:, any 12431:, any 12320:, as ( 12199:with Ξ· 12164:, as ( 11173:counit 9814:under 9148:along 7900:is an 7849:invert 7797:, let 7781:, let 7748:monads 7728:(i.e. 7685:Every 7681:Posets 7633:, the 7615:, the 7577:Every 7559:, the 7456:Given 7393:: see 7273:. Let 7214:groups 6989:monoid 6789:, and 6726:kernel 6712:. Let 6457:, and 6313:  6218:  6165:  5895:  5353:equals 5247:monads 4512:counit 4343:in Hom 3905:and a 1967:whose 1623:, and 1439:, and 1230:or an 16857:Exact 16812:types 16698:-ring 16585:Weak 16569:Topos 16413:Rings 16010:(PDF) 15914:JSTOR 15890:(PDF) 15866:arXiv 15851:Notes 15820:, Ξ΅, 15651:monad 14809:and γ€ˆ 14745:Here 14448:. If 14277:is a 14158:GX, X 14151:and Ξ΅ 14042:and Ξ· 12261:is a 12025:from 11997:from 9967:. So 9687:. So 9208:into 9128:into 9039:: In 8120:into 7557:KHaus 7533:KHaus 7518:KHaus 7379:, or 7351:on a 7343:. In 7254:Field 7222:field 7059:with 7043:is a 6510:Grp β†’ 6463:limit 6093:into 5367:from 5335:with 4667:and 1 4226:(the 4212:from 4192:–, –) 3479:with 3171:from 3123:is a 2794:with 2486:from 2438:is a 2329:right 2264:that 2231:start 1773:with 1273:. If 81:of a 16388:Sets 16050:ISBN 16014:ISBN 15981:ISBN 15960:nLab 15597:and 15586:and 15445:and 15420:are 15416:and 15244:and 15240:are 15236:and 14932:G' G 14930:and 14928:F F' 14821:and 14805:and 14537:and 14529:and 14393:) ∘ 14147:for 14038:for 14017:and 12370:) = 12366:) β†’ 12328:), Ξ· 12301:-). 12227:) β†’ 12175:), Ξ· 12103:), Ξ· 12044:and 11296:) = 11250:) = 11202:and 11189:unit 11083:and 9276:For 8823:and 8269:and 7920:and 7527:and 7516:Let 7463:and 7420:sets 7410:Let 7289:Ring 7282:Ring 7275:Ring 7200:The 7031:and 6927:and 6875:and 6763:β†’ 0. 6734:Ab β†’ 6625:and 6586:sets 6580:The 6556:and 6401:GFGX 6361:GFGX 6319:GFGX 6145:FGFY 6111:FGFY 6095:FGFY 6047:FGFY 5423:the 5403:Let 5269:hom( 5243:unit 4694:and 4677:and 4516:unit 4398:and 4379:and 4202:(–, 4194:and 4159:and 4138:and 3891:and 3872:and 3665:for 2335:and 2327:and 2325:left 2150:and 2080:and 2013:are 2002:and 1923:dual 1884:ring 1252:and 1070:and 1032:and 980:and 720:and 537:and 444:and 314:, a 270:and 112:and 16232:End 16222:CCC 16060:Zbl 16024:Zbl 15937:", 15933:, " 15904:doi 15832:in 15572:of 15564:of 15543:of 15493:). 15232:If 15191:). 14813:β€², 14611:β€², 14409:in 14344:set 14301:of 14285:of 14155:= Ξ¦ 14048:= Ξ¦ 13849:in 13845:to 13835:, Ξ· 13827:in 13823:to 13813:, Ξ΅ 13730:in 13537:in 13356:(-, 12888:= Ξ΅ 12700:(-, 12529:)) 12427:in 12409:in 12316:in 12308:in 12297:(-, 12113:to 12091:in 12033:in 12029:to 12015:, Ξ· 12005:in 12001:to 11987:, Ξ΅ 11308:in 11165:β†’ 1 11150:(–, 11075:An 10341:of 9346:Hom 9313:Hom 9047:Set 8978:in 8890:Sub 8859:Sub 8717:of 8667:Sub 8650:Sub 8427:of 7993:If 7888:If 7867:in 7777:in 7693:to 7553:Top 7537:Top 7498:of 7482:to 7478:of 7446:on 7418:to 7317:to 7311:Grp 7258:Dom 7247:Dom 7162:Mod 7142:Mod 7116:If 7105:Mod 7097:Mod 7081:Mod 7073:Mod 6953:rng 6923:of 6910:of 6804:If 6657:to 6584:of 6549:to 6533:Grp 6513:Grp 6478:Grp 6474:Grp 6409:FGX 6403:to 6323:FGX 6147:to 6101:of 5839:). 5826:to 5788:to 5735:to 5727:to 5675:FGX 5618:FGX 5595:to 5530:to 5471:GFY 5441:Set 5437:Grp 5416:Grp 5410:Set 5375:to 5277:), 5226:or 4899:in 4891:in 4673:on 4317:FYβ€² 4272:in 4251:in 4224:Set 4222:to 4196:hom 4182:hom 4142:in 4134:in 3746:to 3377:in 3280:in 3231:in 3191:to 3147:in 3068:to 3024:in 2692:in 2595:in 2546:in 2506:to 2462:in 2202:of 2065:of 2057:β†’ S 1987:in 1936:of 1880:rng 1683:If 1463:to 1459:is 1419:to 1415:is 1375:of 1226:an 904:or 857:or 806:in 630:in 424:in 290:in 246:in 41:In 16904:: 16710:) 16706:)( 16112:, 16108:, 16058:. 16044:. 16022:. 15958:. 15912:. 15900:87 15898:. 15892:. 15836:. 15818:FG 15713:GF 15711:= 15645:, 15617:FG 15524:, 15509:β†’ 15469:β†’ 15268:β†’ 15252:β†’ 15181:is 15169:is 14797:, 14599:β†’ 14588:β†’ 14576:, 14521:β†’ 14429:β†’ 14385:= 14366:β†’ 14321:β†’ 14289:: 14269:β†’ 14164:GX 14161:(1 14145:GX 14061:FY 14058:(1 14055:FY 14053:, 14036:FY 14027:GX 14025:β†’ 14021:: 14013:β†’ 14011:FY 14009:: 13833:FY 13811:GX 13336:β†’ 13328:, 13324:β†’ 13121:GX 13114:) 13108:(Ξ΅ 13104:= 13101:GX 12900:(Ξ· 12891:FY 12885:FY 12730:GX 12728:β†’ 12716:β†’ 12714:FY 12654:β†’ 12646:, 12642:β†’ 12612:) 12600:, 12588:) 12580:= 12561:) 12550:) 12542:= 12514:) 12475:, 12460:β†’ 12442:β†’ 12420:, 12402:, 12378:) 12349:, 12339:, 12251:β†’ 12157:β†’ 12127:β†’ 12080:β†’ 12064:β†’ 12013:FY 11985:GX 11304:β†’ 11302:FY 11287:, 11276:GX 11274:β†’ 11260:GX 11258:β†’ 11241:, 11228:β†’ 11226:FY 11185:GF 11183:β†’ 11163:FG 11157:A 11154:–) 11130:A 11120:β†’ 11102:β†’ 11091:A 10881:. 10653:. 7968:β†’ 7912:β†’ 7896:β†’ 7701:≀ 7639:. 7588:β†’ 7555:β†’ 7535:β†’ 7476:SX 7337:/. 7309:β†’ 7307:Ab 7287:β†’ 7256:β†’ 7156:β†’ 7154:Ab 7146:Ab 7144:β†’ 7099:β†’ 7075:β†’ 7039:β†’ 6914:). 6856:, 6846:Ab 6844:β†’ 6842:Ab 6825:, 6816:Ab 6810:Ab 6785:, 6781:, 6722:Ab 6720:β†’ 6697:= 6673:, 6639:β†’ 6618:β†’ 6527:, 6487:, 6476:β†’ 6453:, 6449:, 6419:. 6417:GX 6405:GX 6357:GX 6159:. 6157:FY 6153:FY 6149:FY 6103:FY 6091:FY 6051:FY 5824:FY 5820:GX 5808:FY 5790:GX 5733:FZ 5622:GX 5606:. 5593:FY 5540:GW 5475:FY 5459:: 5439:β†’ 5413:β†’ 5383:. 5371:Γ— 5293:)) 5285:, 5167:. 5165:FY 5102:, 4903:, 4406:β†’ 4394:β†’ 4371:A 4361:Gf 4359:, 4351:, 4349:FY 4337:Fg 4333:h 4329:f 4327:β†’ 4321:Xβ€² 4319:, 4307:, 4305:FY 4295:, 4293:Fg 4280:: 4267:β†’ 4248:Xβ€² 4246:β†’ 4217:Γ— 4206:–) 4169:. 4146:. 3900:β†’ 3887:β†’ 3861:A 3849:. 3766:. 3722:; 3527:. 3088:. 3044:; 2849:: 2842:. 2390:β†’ 2374:, 2370:, 2358:, 2354:, 2287:. 2219:R* 2217:β†’ 2211:R* 2206:. 2190:)= 2172:R* 2170:)= 2125:R* 2123:β†’ 2084:β†’ 2073:β†’ 2046:β†’ 2039:, 2032:β†’ 2028:, 2021:β†’ 2006:β†’ 1995:β†’ 1975:β†’ 1753:, 1680:. 1348:, 1084:, 953:. 830:. 595:op 522:op 140:) 49:, 16802:e 16795:t 16788:v 16702:( 16695:n 16693:E 16655:) 16651:( 16639:n 16603:) 16599:( 16587:n 16429:) 16425:( 16419:) 16415:( 16143:e 16136:t 16129:v 16116:. 16066:. 16030:. 15962:. 15920:. 15906:: 15874:. 15868:: 15834:C 15826:G 15824:Ξ· 15822:F 15814:F 15812:Ξ΅ 15810:G 15792:T 15784:2 15780:T 15776:: 15747:T 15738:D 15733:1 15729:: 15709:T 15690:D 15680:D 15675:: 15672:T 15659:D 15655:T 15653:γ€ˆ 15647:G 15643:F 15627:F 15622:D 15613:G 15609:F 15602:1 15599:C 15595:1 15592:D 15588:G 15584:F 15579:Y 15574:D 15570:Y 15566:D 15558:1 15555:D 15550:X 15545:C 15541:X 15537:C 15533:1 15530:C 15526:G 15522:F 15511:C 15507:D 15503:F 15491:C 15487:D 15479:G 15475:D 15471:D 15467:C 15463:G 15459:D 15455:C 15447:D 15443:C 15418:D 15414:C 15407:F 15403:F 15399:G 15382:) 15379:X 15376:G 15373:, 15370:Y 15367:( 15361:D 15355:m 15352:o 15349:h 15341:) 15338:X 15335:, 15332:Y 15329:F 15326:( 15320:C 15314:m 15311:o 15308:h 15303:: 15298:X 15295:, 15292:Y 15274:G 15270:D 15266:C 15262:G 15254:C 15250:D 15246:F 15238:D 15234:C 15223:. 15216:; 15153:C 15125:. 15119:C 15114:1 15098:G 15095:F 15089:G 15078:F 15069:G 15062:G 15054:F 15050:F 15038:F 15034:F 15031:G 15024:G 15013:F 15002:G 14988:F 14980:G 14956:E 14951:1 14911:. 14908:E 14902:C 14899:: 14896:G 14886:G 14859:C 14853:E 14850:: 14843:F 14836:F 14823:E 14819:D 14815:G 14811:F 14807:D 14803:C 14799:G 14795:F 14726:. 14723:) 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13903:( 13900:G 13897:= 13894:) 13891:f 13888:( 13883:X 13880:, 13877:Y 13853:. 13851:D 13847:G 13843:Y 13838:Y 13829:C 13825:X 13821:F 13816:X 13794:) 13791:Y 13788:F 13785:, 13782:Y 13779:F 13776:( 13771:C 13766:m 13763:o 13760:h 13750:Y 13747:F 13743:1 13732:D 13728:Y 13714:) 13711:Y 13708:F 13705:G 13702:, 13699:Y 13696:( 13691:D 13686:m 13683:o 13680:h 13672:) 13667:Y 13664:F 13660:1 13656:( 13651:Y 13648:F 13645:, 13642:Y 13634:= 13629:Y 13601:) 13598:X 13595:G 13592:, 13589:X 13586:G 13583:( 13578:D 13573:m 13570:o 13567:h 13557:X 13554:G 13550:1 13539:C 13535:X 13521:) 13518:X 13515:, 13512:X 13509:G 13506:F 13503:( 13498:C 13493:m 13490:o 13487:h 13479:) 13474:X 13471:G 13467:1 13463:( 13458:1 13450:X 13447:, 13444:X 13441:G 13433:= 13428:X 13395:G 13389:F 13386:: 13383:) 13377:, 13371:( 13358:G 13353:D 13348:F 13346:( 13343:C 13338:D 13334:C 13330:G 13326:C 13322:D 13318:F 13289:g 13286:= 13283:g 13275:X 13272:G 13268:1 13264:= 13254:g 13246:X 13243:G 13232:) 13227:X 13219:( 13216:G 13213:= 13201:Y 13190:) 13187:g 13184:( 13181:F 13178:G 13172:) 13167:X 13159:( 13156:G 13153:= 13146:g 13118:Ξ· 13116:o 13111:X 13106:G 13096:G 13071:f 13068:= 13063:Y 13060:F 13056:1 13049:f 13046:= 13036:) 13031:Y 13023:( 13020:F 13012:Y 13009:F 12998:f 12995:= 12985:) 12980:Y 12972:( 12969:F 12963:) 12960:f 12957:( 12954:G 12951:F 12943:X 12935:= 12928:f 12903:Y 12898:F 12895:o 12880:F 12855:) 12852:g 12849:( 12846:F 12838:X 12830:= 12827:) 12824:g 12821:( 12816:X 12813:, 12810:Y 12796:Y 12785:) 12782:f 12779:( 12776:G 12773:= 12770:) 12767:f 12764:( 12759:X 12756:, 12753:Y 12726:Y 12722:g 12718:X 12710:f 12702:G 12697:D 12692:F 12690:( 12687:C 12682:G 12660:F 12656:D 12652:C 12648:G 12644:C 12640:D 12636:F 12617:y 12614:o 12610:f 12608:( 12605:0 12602:X 12598:0 12595:Y 12592:Ξ¦ 12590:o 12586:x 12584:( 12582:G 12578:y 12575:o 12571:0 12568:Y 12565:Ξ· 12563:o 12559:f 12557:( 12555:G 12552:o 12548:x 12546:( 12544:G 12539:1 12536:Y 12533:Ξ· 12531:o 12527:y 12525:( 12523:F 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10288:S 10282:x 10278:. 10275:) 10272:] 10269:} 10266:y 10263:{ 10260:[ 10255:1 10248:f 10241:x 10238:( 10229:Y 10223:y 10220:{ 10217:= 10214:S 10209:f 10191:. 10179:} 10176:) 10173:x 10170:( 10165:S 10154:) 10151:y 10148:, 10145:x 10142:( 10137:f 10128:. 10125:x 10116:Y 10110:y 10107:{ 10083:. 10080:] 10077:S 10074:[ 10071:f 10068:= 10065:} 10061:S 10055:x 10051:. 10048:) 10045:] 10042:} 10039:y 10036:{ 10033:[ 10028:1 10021:f 10014:x 10011:( 10002:Y 9996:y 9993:{ 9990:= 9987:S 9982:f 9955:] 9952:S 9949:[ 9946:f 9926:Y 9920:y 9900:S 9894:] 9891:} 9888:y 9885:{ 9882:[ 9877:1 9870:f 9849:y 9827:f 9802:S 9776:f 9755:T 9749:] 9746:S 9743:[ 9740:f 9720:] 9717:T 9714:[ 9709:1 9702:f 9695:S 9675:T 9669:) 9666:x 9663:( 9660:f 9640:] 9637:T 9634:[ 9629:1 9622:f 9615:x 9595:S 9589:x 9569:] 9566:T 9563:[ 9558:1 9551:f 9544:] 9541:] 9538:S 9535:[ 9532:f 9529:[ 9524:1 9517:f 9510:S 9490:T 9484:] 9481:S 9478:[ 9475:f 9460:. 9448:] 9445:T 9442:[ 9437:1 9430:f 9423:S 9417:T 9411:S 9406:f 9375:, 9372:) 9369:T 9360:f 9356:, 9353:S 9350:( 9339:) 9336:T 9333:, 9330:S 9325:f 9317:( 9290:X 9284:S 9273:. 9261:X 9255:] 9252:T 9249:[ 9244:1 9237:f 9216:Y 9196:T 9176:f 9156:f 9136:Y 9116:T 9096:T 9091:Y 9083:X 9080:= 9077:T 9068:f 9031:. 9019:Y 8999:T 8994:Y 8986:X 8966:X 8946:f 8926:X 8920:S 8900:) 8897:Y 8894:( 8869:) 8866:X 8863:( 8836:f 8809:f 8784:T 8779:Y 8771:X 8751:Y 8745:T 8725:Y 8705:T 8677:) 8674:X 8671:( 8660:) 8657:Y 8654:( 8646:: 8637:f 8614:Y 8608:X 8605:: 8602:f 8582:Y 8507:S 8480:f 8455:x 8435:Y 8415:y 8391:} 8388:) 8385:x 8382:( 8377:S 8366:) 8363:y 8360:, 8357:x 8354:( 8349:f 8340:. 8337:x 8328:Y 8322:y 8319:{ 8297:X 8277:Y 8257:X 8235:f 8201:) 8198:y 8195:( 8186:) 8183:y 8180:( 8175:Y 8167:= 8164:) 8161:y 8158:( 8153:T 8128:Y 8108:T 8088:Y 8082:T 8062:} 8059:) 8056:y 8053:( 8048:Y 8037:y 8034:{ 8031:= 8028:Y 8006:Y 7974:A 7970:C 7966:C 7952:A 7948:U 7944:U 7940:D 7936:D 7932:0 7922:G 7918:F 7914:D 7910:C 7906:G 7898:C 7894:D 7890:F 7875:. 7841:. 7839:F 7835:G 7831:T 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3515:g 3512:= 3507:Y 3496:) 3493:f 3490:( 3487:G 3467:X 3461:) 3458:Y 3455:( 3452:F 3449:: 3446:f 3426:) 3423:X 3420:( 3417:G 3411:Y 3408:: 3405:g 3385:C 3365:X 3345:) 3342:) 3339:Y 3336:( 3333:F 3330:( 3327:G 3321:Y 3318:: 3313:Y 3288:C 3268:) 3265:Y 3262:( 3259:F 3239:D 3219:Y 3199:G 3179:Y 3155:D 3135:Y 3111:D 3105:C 3102:: 3099:G 3076:G 3052:F 3032:C 3012:X 3002:X 2998:: 2995:f 2969:X 2957:f 2954:= 2951:) 2948:) 2945:f 2942:( 2939:G 2936:( 2933:F 2925:X 2900:D 2894:C 2891:: 2888:G 2868:G 2830:f 2827:= 2824:) 2821:g 2818:( 2815:F 2807:X 2782:) 2779:X 2776:( 2773:G 2767:Y 2764:: 2761:g 2741:X 2735:) 2732:Y 2729:( 2726:F 2723:: 2720:f 2700:D 2680:Y 2660:X 2654:) 2651:) 2648:X 2645:( 2642:G 2639:( 2636:F 2633:: 2628:X 2603:D 2583:) 2580:X 2577:( 2574:G 2554:C 2534:X 2514:X 2494:F 2470:C 2450:X 2426:C 2420:D 2417:: 2414:F 2396:C 2392:C 2388:D 2384:F 2380:D 2376:g 2372:G 2368:Y 2364:C 2360:f 2356:F 2352:X 2345:D 2341:C 2337:D 2333:C 2307:. 2285:F 2281:G 2277:G 2273:F 2266:F 2258:G 2254:G 2246:F 2239:F 2235:F 2215:R 2204:G 2196:F 2192:S 2188:S 2186:( 2184:G 2180:S 2176:G 2168:R 2166:( 2164:F 2160:F 2137:R 2133:E 2129:E 2121:R 2117:1 2114:S 2110:2 2107:S 2103:2 2100:S 2096:1 2093:S 2089:2 2086:S 2082:R 2078:1 2075:S 2071:R 2067:R 2059:2 2055:1 2051:2 2048:S 2044:1 2041:S 2037:2 2034:S 2030:R 2026:1 2023:S 2019:R 2011:2 2008:S 2004:R 2000:1 1997:S 1993:R 1989:E 1981:S 1977:S 1973:R 1965:E 1961:R 1954:E 1938:E 1930:E 1896:r 1892:r 1814:x 1811:U 1808:, 1805:y 1799:= 1793:x 1790:, 1787:y 1784:T 1761:U 1741:T 1711:. 1708:G 1702:F 1689:G 1685:F 1665:D 1659:m 1656:o 1653:h 1631:G 1608:C 1602:m 1599:o 1596:h 1574:F 1554:F 1534:F 1511:F 1491:G 1471:F 1447:G 1427:G 1403:F 1383:f 1359:f 1336:) 1333:X 1330:, 1327:Y 1324:F 1321:( 1315:C 1309:m 1306:o 1303:h 1281:f 1260:G 1240:F 1191:) 1188:X 1185:G 1182:, 1179:Y 1176:( 1170:D 1164:m 1161:o 1158:h 1150:) 1147:X 1144:, 1141:Y 1138:F 1135:( 1129:C 1123:m 1120:o 1117:h 1112:: 1107:Y 1104:X 1042:D 1018:C 990:D 966:C 941:G 935:F 914:F 888:G 867:G 841:F 816:D 794:Y 773:t 770:e 767:S 758:C 753:: 750:) 744:G 741:, 738:Y 735:( 730:D 707:t 704:e 701:S 692:C 687:: 684:) 678:, 675:Y 672:F 669:( 664:C 640:C 618:X 591:t 587:e 584:S 575:D 570:: 567:) 564:X 561:G 558:, 552:( 547:D 518:t 514:e 511:S 502:D 497:: 494:) 491:X 488:, 482:F 479:( 474:C 452:Y 432:X 405:) 402:X 399:G 396:, 393:Y 390:( 384:D 378:m 375:o 372:h 364:) 361:X 358:, 355:Y 352:F 349:( 343:C 337:m 334:o 331:h 300:D 278:Y 256:C 234:X 209:D 199:C 194:: 191:G 169:C 159:D 154:: 151:F 122:D 98:C 38:. 20:)

Index

Adjoint functor
Adjunction (field theory)
Adjunction space
mathematics
category theory
functors
universal property
free group on a set
Stoneβ€“ΔŒech compactification
topological space
covariant
bijection
natural
equivalence
adjoint
adjunct
cognates
Mac Lane
Hilbert space
adjoint operators
Categories for the Working Mathematician
colimits/limits
ring theory
rng
ring
universal property
functor
dual
initial object
supremum

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