3430:
879:
1206:
1042:, there is no hope to find an exact solution: "Nothing is more proper to give us an idea of the hardness of the three-body problem, and generally of all problems of Dynamics where there is no uniform integral and the Bohlin series diverge." He also noted that the search for an approximate solution is no more efficient: "the more we seek to obtain precise approximations, the more the result will diverge towards an increasing imprecision".
5368:. The basic theorem regarding Hex, first proven by John Nash, is that no game of Hex can end in a draw; the first player always has a winning strategy (although this theorem is nonconstructive, and explicit strategies have not been fully developed for board sizes of dimensions 10 x 10 or greater). This turns out to be equivalent to the Brouwer fixed-point theorem for dimension 2. By considering
2977:
5058:, which is also non-singular for the restriction to the boundary (which is just the identity). Thus the inverse image would be a 1-manifold with boundary. The boundary would have to contain at least two end points, both of which would have to lie on the boundary of the original ball—which is impossible in a retraction.
861:
The theorem is supposed to have originated from
Brouwer's observation of a cup of gourmet coffee. If one stirs to dissolve a lump of sugar, it appears there is always a point without motion. He drew the conclusion that at any moment, there is a point on the surface that is not moving. The fixed point
1084:
defines it as the branch which "treats the properties of an object that are invariant if it is deformed in any continuous way, without tearing". In 1886, Poincaré proved a result that is equivalent to
Brouwer's fixed-point theorem, although the connection with the subject of this article was not yet
865:
Brouwer is said to have added: "I can formulate this splendid result different, I take a horizontal sheet, and another identical one which I crumple, flatten and place on the other. Then a point of the crumpled sheet is in the same place as on the other sheet." Brouwer "flattens" his sheet as with a
944:
Brouwer is said to have expressed this as follows: "Instead of examining a surface, we will prove the theorem about a piece of string. Let us begin with the string in an unfolded state, then refold it. Let us flatten the refolded string. Again a point of the string has not changed its position with
841:
In three dimensions a consequence of the
Brouwer fixed-point theorem is that, no matter how much you stir a delicious cocktail in a glass (or think about milk shake), when the liquid has come to rest, some point in the liquid will end up in exactly the same place in the glass as before you took any
1167:. The ensuing discussions convinced Brouwer of the importance of a better understanding of Euclidean spaces, and were the origin of a fruitful exchange of letters with Hadamard. For the next four years, he concentrated on the proof of certain great theorems on this question. In 1912 he proved the
846:
defeats the convexity condition ("shaking" being defined as a dynamic series of non-convex inertial containment states in the vacant headspace under a lid). In that case, the theorem would not apply, and thus all points of the liquid disposition are potentially displaced from the original state.
830:
Take two sheets of graph paper of equal size with coordinate systems on them, lay one flat on the table and crumple up (without ripping or tearing) the other one and place it, in any fashion, on top of the first so that the crumpled paper does not reach outside the flat one. There will then be at
1171:
for the two-dimensional sphere, as well as the fact that every continuous map from the two-dimensional ball to itself has a fixed point. These two results in themselves were not really new. As
Hadamard observed, Poincaré had shown a theorem equivalent to the hairy ball theorem. The revolutionary
1069:. Poincaré went further; if the area is of the same kind as a disk, as is the case for the cup of coffee, there must necessarily be a fixed point. This fixed point is invariant under all functions which associate to each point of the original surface its position after a short time interval
6003:
variant, a combinatorial variant and a set-covering variant. Each variant can be proved separately using totally different arguments, but each variant can also be reduced to the other variants in its row. Additionally, each result in the top row can be deduced from the one below it in the same
3924:
842:
action, assuming that the final position of each point is a continuous function of its original position, that the liquid after stirring is contained within the space originally taken up by it, and that the glass (and stirred surface shape) maintain a convex volume. Ordering a cocktail
4172:
3236:
1121:
889:
is defined on a closed interval and takes values in the same interval. Saying that this function has a fixed point amounts to saying that its graph (dark green in the figure on the right) intersects that of the function defined on the same interval which maps
6641:"concerne les propriétés invariantes d'une figure lorsqu'on la déforme de manière continue quelconque, sans déchirure (par exemple, dans le cas de la déformation de la sphère, les propriétés corrélatives des objets tracés sur sa surface". From C. Houzel M. Paty
2836:
1180:
comments on the respective roles as follows: "Compared to
Brouwer's revolutionary methods, those of Hadamard were very traditional, but Hadamard's participation in the birth of Brouwer's ideas resembles that of a midwife more than that of a mere spectator."
5732:
866:
flat iron, without removing the folds and wrinkles. Unlike the coffee cup example, the crumpled paper example also demonstrates that more than one fixed point may exist. This distinguishes
Brouwer's result from other fixed-point theorems, such as
1854:
672:
which is a continuous function from the open interval (−1,1) to itself. Since x = 1 is not part of the interval, there is not a fixed point of f(x) = x. The space (−1,1) is convex and bounded, but not closed. On the other hand, the function
1184:
Brouwer's approach yielded its fruits, and in 1910 he also found a proof that was valid for any finite dimension, as well as other key theorems such as the invariance of dimension. In the context of this work, Brouwer also generalized the
234:, Brouwer's is particularly well known, due in part to its use across numerous fields of mathematics. In its original field, this result is one of the key theorems characterizing the topology of Euclidean spaces, along with the
1239:
functions, there are many that have emerged directly or indirectly from the result under discussion. A continuous map from a closed ball of
Euclidean space to its boundary cannot be the identity on the boundary. Similarly, the
862:
is not necessarily the point that seems to be motionless, since the centre of the turbulence moves a little bit. The result is not intuitive, since the original fixed point may become mobile when another fixed point appears.
5480:
3744:
2364:
1295:
there is a winning strategy for white. In economics, P. Bich explains that certain generalizations of the theorem show that its use is helpful for certain classical problems in game theory and generally for equilibria
2245:
6386:
The interest of this anecdote rests in its intuitive and didactic character, but its accuracy is dubious. As the history section shows, the origin of the theorem is not
Brouwer's work. More than 20 years earlier
4039:
4360:
838:
Take an ordinary map of a country, and suppose that that map is laid out on a table inside that country. There will always be a "You are Here" point on the map which represents that same point in the country.
1023:
1015:
3126:
1142:
It was
Brouwer, finally, who gave the theorem its first patent of nobility. His goals were different from those of Poincaré. This mathematician was inspired by the foundations of mathematics, especially
6150:
Il en a démontré l'un des plus beaux théorèmes, le théorème du point fixe, dont les applications et généralisations, de la théorie des jeux aux équations différentielles, se sont révélées fondamentales.
5280:
835:= 2 case of Brouwer's theorem applied to the continuous map that assigns to the coordinates of every point of the crumpled sheet the coordinates of the point of the flat sheet immediately beneath it.
1131:
At the dawn of the 20th century, the interest in analysis situs did not stay unnoticed. However, the necessity of a theorem equivalent to the one discussed in this article was not yet evident.
1176:, the underlying concept of the Poincaré group. In the following year, Hadamard generalised the theorem under discussion to an arbitrary finite dimension, but he employed different methods.
5914:
2972:{\displaystyle {\mathbf {w} }({\mathbf {x} })=(1-{\mathbf {x} }\cdot {\mathbf {f} }({\mathbf {x} }))\,{\mathbf {x} }-(1-{\mathbf {x} }\cdot {\mathbf {x} })\,{\mathbf {f} }({\mathbf {x} }).}
5081:
to the fixed point so the method is essentially computable. gave a conceptually similar path-following version of the homotopy proof which extends to a wide variety of related problems.
6285:
This version follows directly from the previous one because every convex compact subset of a
Euclidean space is homeomorphic to a closed ball of the same dimension as the subset; see
5868:
5200:
5122:
1139:
mathematician, applied topological methods to the study of differential equations. In 1904 he proved the three-dimensional case of our theorem, but his publication was not noticed.
667:
297:
requires the use of topological methods. This work at the end of the 19th century opened into several successive versions of the theorem. The case of differentiable mappings of the
2117:
5740:
The generalizations of the Brouwer fixed-point theorem to infinite dimensional spaces therefore all include a compactness assumption of some sort, and also often an assumption of
4443:
4256:
1389:
4771:
4562:
2368:
defines a homotopy from the identity function to it. The identity function has degree one at every point. In particular, the identity function has degree one at the origin, so
831:
least one point of the crumpled sheet that lies directly above its corresponding point (i.e. the point with the same coordinates) of the flat sheet. This is a consequence of the
788:-dimensional sphere (or any symmetric domain that does not contain the origin). The unit circle is closed and bounded, but it has a hole (and so it is not convex) . The function
5626:
4860:
1982:
4399:
4211:
5801:
2531:.) Sometimes the theorem is expressed by the statement that "there is always a place on the globe with no wind". An elementary proof of the hairy ball theorem can be found in
1418:
3514:
sending each point in the disk to its corresponding intersection point on the boundary. As a special case, whenever x itself is on the boundary, then the intersection point
138:
2014:
1753:
1045:
He studied a question analogous to that of the surface movement in a cup of coffee. What can we say, in general, about the trajectories on a surface animated by a constant
4679:
4619:
4031:
603:
581:
5956:
901:
Intuitively, any continuous line from the left edge of the square to the right edge must necessarily intersect the green diagonal. To prove this, consider the function
2464:
2425:
1681:
1509:
556:
5531:
5336:, taking into account multiplicity and orientation), and should remain constant (as it is very clear in the one-dimensional case). On the other hand, as the parameter
1450:
498:
4975:
774:
7220:
Later it would be shown that the formalism that was combatted by Brouwer can also serve to formalise intuitionism, with some modifications. For further details see
2061:
721:
89:
6326:
6113:
4934:
1606:
5021:
4883:
1272:, which describes the qualitative behaviour of certain differential equations near certain equilibria. Similarly, Brouwer's theorem is used for the proof of the
1220:
The theorem proved its worth in more than one way. During the 20th century numerous fixed-point theorems were developed, and even a branch of mathematics called
315:
The theorem has several formulations, depending on the context in which it is used and its degree of generalization. The simplest is sometimes given as follows:
5769:
4998:
4905:
4811:
4719:
4699:
4639:
4585:
4503:
4483:
4463:
2386:
2140:
2034:
1916:
1896:
1745:
1725:
1705:
1646:
1626:
1577:
1553:
1533:
1474:
221:
201:
178:
158:
55:
6646:
5392:
to itself has only isolated fixed points, then the number of fixed points counted with multiplicities (which may be negative) is equal to the Lefschetz number
5073:, on the boundary, (assuming it is not a fixed point) the one manifold with boundary mentioned above does exist and the only possibility is that it leads from
3643:. This shows that the retraction is impossible, because again the retraction would induce an injective group homomorphism from the latter to the former group.
692:
Convexity is not strictly necessary for Brouwer's fixed-point theorem. Because the properties involved (continuity, being a fixed point) are invariant under
5745:
1261:
3919:{\displaystyle 0<\int _{\partial B}\omega =\int _{\partial B}F^{*}(\omega )=\int _{B}dF^{*}(\omega )=\int _{B}F^{*}(d\omega )=\int _{B}F^{*}(0)=0,}
975:
6585:
6499:
L'identité algébrique d'une pratique portée par la discussion sur l'équation à l'aide de laquelle on détermine les inégalités séculaires des planètes
3686:
As in the proof of Brouwer's fixed-point theorem for continuous maps using homology, it is reduced to proving that there is no continuous retraction
6795:[The first proof of a fixed-point theorem for a continuous mapping of a sphere into itself, given by the Latvian mathematician P. G. Bohl].
5398:
2255:
1193:. This branch of mathematics, originally envisioned by Poincaré and developed by Brouwer, changed its name. In the 1930s, analysis situs became
8091:
2148:
6031:
4167:{\displaystyle \Delta ^{n}=\left\{P\in \mathbb {R} ^{n+1}\mid \sum _{i=0}^{n}{P_{i}}=1{\text{ and }}P_{i}\geq 0{\text{ for all }}i\right\}.}
6407:
6249:
6077:
6072:
3231:{\displaystyle {\mathbf {X} }({\mathbf {x} },t)=(-t\,{\mathbf {w} }({\mathbf {x} }),{\mathbf {x} }\cdot {\mathbf {w} }({\mathbf {x} })).}
6759:
4264:
6346:
5958:. Examples of chainable continua include compact connected linearly ordered spaces and in particular closed intervals of real numbers.
4793:
is continuous, this simplex can be made arbitrarily small by choosing an arbitrarily fine triangulation. Hence, there must be a point
5590:
instead of Euclidean space, is not true. The main problem here is that the unit balls of infinite-dimensional Hilbert spaces are not
5348:, which is a contradiction since the oriented area of the identity coincides with the volume of the ball, while the oriented area of
7263:
6793:"Первое доказательство теоремы о неподвижной точке при непрерывном отображении шара в себя, данное латышским математиком П.Г.Болем"
5737:
It is not difficult to check that this map is continuous, has its image in the unit sphere of ℓ, but does not have a fixed point.
5054:. One then defines a retraction as above which must now be differentiable. Such a retraction must have a non-singular value, by
1085:
apparent. A little later, he developed one of the fundamental tools for better understanding the analysis situs, now known as the
8132:
8035:
7137:
5208:
7171:
2800:
The continuous version of the hairy ball theorem can now be used to prove the Brouwer fixed point theorem. First suppose that
7938:
7850:
7823:
7772:
6736:
6481:
6456:
5976:(functions that assign to each point of the set a subset of the set). It also requires compactness and convexity of the set.
738:
The following example shows that Brouwer's fixed-point theorem does not work for domains with holes. Consider the function
250:. This gives it a place among the fundamental theorems of topology. The theorem is also used for proving deep results about
8142:
6564:
7191:
987:
proved the general case in 1910, and Brouwer found a different proof in the same year. Since these early proofs were all
7866:
6757:
Sur l'application des méthodes d'approximations successives à l'étude de certaines équations différentielles ordinaires
6048:
7957:
7713:
7682:
7614:
7583:
7490:
7041:
7020:
6703:
6672:
6298:
6273:
6137:
5069:
proof by observing that the retract is in fact defined everywhere except at the fixed points. For almost any point,
5043:
3711:
2710:
1303:
Brouwer's celebrity is not exclusively due to his topological work. The proofs of his great topological theorems are
1108:. Instead of the topological properties of the domain, this theorem uses the fact that the function in question is a
6604:
6321:
6108:
5873:
3938:
onto its boundary. The proof using Stokes' theorem is closely related to the proof using homology, because the form
294:
1089:
or sometimes the Poincaré group. This method can be used for a very compact proof of the theorem under discussion.
6643:
3932:
More generally, this shows that there is no smooth retraction from any non-empty smooth oriented compact manifold
1224:. Brouwer's theorem is probably the most important. It is also among the foundational theorems on the topology of
7926:
1512:
1256:
provided from 1926 a method for counting fixed points. In 1930, Brouwer's fixed-point theorem was generalized to
203:
to itself. A more general form than the latter is for continuous functions from a nonempty convex compact subset
6082:
5987:
that guarantees the existence of fixed points; this condition is trivially satisfied for any map in the case of
5042:
can be approximated by a smooth map retaining the property of not fixing a point; this can be done by using the
2473:
This requires some work to make fully general. The definition of degree must be extended to singular values of
696:, Brouwer's fixed-point theorem is equivalent to forms in which the domain is required to be a closed unit ball
7796:
6391:
had proved an equivalent result, and 5 years before Brouwer P. Bohl had proved the three-dimensional case.
1333:
1190:
325:
6527:
8137:
8127:
8057:
7259:
7032:"... Brouwer's fixed point theorem, perhaps the most important fixed point theorem." p xiii V. I. Istratescu
6695:
5980:
5821:
5127:
5092:
3976:
1277:
1253:
1031:
799:
6895:... cette dernière propriété, bien que sous des hypothèses plus grossières, ait été démontré par H. Poincaré
3386:),0). The advantage of this proof is that it uses only elementary techniques; more general results like the
619:
285:
The theorem was first studied in view of work on differential equations by the French mathematicians around
7985:
6199:
5962:
5727:{\displaystyle y_{0}={\sqrt {1-\|x\|_{2}^{2}}}\quad {\text{ and}}\quad y_{n}=x_{n-1}{\text{ for }}n\geq 1.}
2070:
1308:
1097:
999:
980:
400:
263:
31:
4404:
4216:
3607:> 2, however, proving the impossibility of the retraction is more difficult. One way is to make use of
1350:
8052:
6690:
5493:
is a ball (or more generally is contractible) then the Lefschetz number is one because the only non-zero
4724:
4515:
798:
A formal generalization of Brouwer's fixed-point theorem for "hole-free" domains can be derived from the
8111:
8079:
6172:
4816:
1921:
1081:
7949:
7788:
7642:
6979:
6815:
6062:
4368:
4180:
1152:
1101:
930:
723:. For the same reason it holds for every set that is homeomorphic to a closed ball (and therefore also
6428:
Bohl, P. (1904). "Über die Bewegung eines mechanischen Systems in der Nähe einer Gleichgewichtslage".
5774:
1849:{\displaystyle \operatorname {deg} _{p}(f)=\sum _{x\in f^{-1}(p)}\operatorname {sign} \,\det(df_{x}).}
1394:
1252:
has a pair of antipodal points that are mapped to the same point. In the finite-dimensional case, the
1076:
To understand differential equations better, a new branch of mathematics was born. Poincaré called it
1034:
returned into the focus of the mathematical community. Its solution required new methods. As noted by
8047:
7169:
Une extension discontinue du théorème du point fixe de Schauder, et quelques applications en économie
6685:
6088:
2499:
in an odd-dimensional Euclidean space, there is no nowhere-vanishing continuous tangent vector field
1311:. He became the originator and zealous defender of a way of formalising mathematics that is known as
8088:
7511:
6778:
6728:
6722:
5586:
The straightforward generalization to infinite dimensions, i.e. using the unit ball of an arbitrary
1867:, with sheets counted oppositely if they are oppositely oriented. This is thus a generalization of
94:
6515:
5372:-dimensional versions of Hex, one can prove in general that Brouwer's theorem is equivalent to the
1987:
1556:
5568:
5554:
4654:
4594:
4006:
586:
564:
7221:
6067:
6038:
5919:
2481:
simplifies the construction of the degree, and so has become a standard proof in the literature.
1269:
1241:
1073:. If the area is a circular band, or if it is not closed, then this is not necessarily the case.
247:
243:
6752:
1093:
1026:
The theorem applies to any disk-shaped area, where it guarantees the existence of a fixed point.
290:
6152:
5089:
A variation of the preceding proof does not employ the Sard's theorem, and goes as follows. If
3608:
2430:
2391:
1651:
1479:
517:
267:
6964:, then the open set is never homeomorphic to an open subset of a Euclidean space of dimension
6244:
5803:
has a fixed point, where a chainable continuum is a (usually but in this case not necessarily
5500:
1423:
462:
7864:(1976). "A constructive proof of the Brouwer fixed point theorem and computational results".
7779:(see p. 72–73 for Hirsch's proof utilizing non-existence of a differentiable retraction)
6208:
6203:
4942:
3530:
1337:
1273:
741:
432:(functions that have the same set as the domain and codomain) and for nonempty sets that are
255:
251:
7677:. Cahiers Scientifiques (in French). Vol. IX. Paris: Gauthier-Villars. pp. 44–47.
6756:
6343:
6288:
5983:
applies to (almost) arbitrary compact topological spaces, and gives a condition in terms of
1268:. One also meets the theorem and its variants outside topology. It can be used to prove the
8031:
7993:
7967:
7895:
7875:
7833:
7806:
7723:
7692:
7665:
7624:
7593:
7566:
7519:
6916:
6875:
6837:
6572:, on the website of l'Association roumaine des chercheurs francophones en sciences humaines
2039:
1684:
1312:
1307:, and Brouwer's dissatisfaction with this is partly what led him to articulate the idea of
1229:
1225:
1186:
1018:
For flows in an unbounded area, or in an area with a "hole", the theorem is not applicable.
1003:
699:
235:
67:
7250:
4910:
1582:
583:
to itself. As it shifts every point to the right, it cannot have a fixed point. The space
8:
8010:
7537:
7503:
5973:
5580:
5561:
5550:
5494:
3429:
3403:
3387:
2995:
2616:
1265:
1236:
1109:
1022:
1014:
962:
958:
843:
271:
231:
35:
23:
7879:
7055:
5003:
4936:
must be equal, all these inequalities must actually be equalities. But this means that:
4865:
1172:
aspect of Brouwer's approach was his systematic use of recently developed tools such as
8019:
8002:
7979:
7748:
7554:
7507:
7407:
7075:
6519:
6225:
6026:
6000:
5754:
4983:
4890:
4796:
4704:
4684:
4624:
4570:
4488:
4468:
4448:
3988:
3943:
3735:
3647:
3577:
3391:
2490:
2371:
2125:
2019:
1901:
1881:
1730:
1710:
1690:
1631:
1611:
1562:
1538:
1518:
1459:
1304:
1297:
1221:
1194:
1168:
1144:
1046:
1039:
988:
954:
938:
332:
239:
206:
186:
181:
163:
143:
40:
8105:
7656:
7637:
7485:
7465:
7448:
885:
In one dimension, the result is intuitive and easy to prove. The continuous function
878:
7953:
7934:
7846:
7819:
7792:
7768:
7709:
7678:
7638:"Finding zeroes of maps: Homotopy methods that are constructive with probability one"
7610:
7579:
7132:
7037:
7016:
6930:
6911:
6889:
6870:
6851:
6832:
6732:
6699:
6668:
6477:
6452:
6294:
6269:
6229:
6133:
6043:
5984:
5579:
The Brouwer fixed-point theorem forms the starting point of a number of more general
5055:
3573:
1086:
6718:
6556:
6540:
6511:
6388:
4775:
By construction, this is a Sperner coloring. Hence, by Sperner's lemma, there is an
2725:
into Euclidean space. The orthogonal projection on to the tangent space is given by
1156:
1035:
998:
ideals. Although the existence of a fixed point is not constructive in the sense of
286:
7883:
7740:
7651:
7546:
7499:
7460:
7399:
7203:
7168:
7154:
7113:
7084:
6925:
6907:
6884:
6866:
6846:
6828:
6583:
Poincaré, H. (1886). "Sur les courbes définies par les équations différentielles".
6217:
6167:
5999:
There are several fixed-point theorems which come in three equivalent variants: an
5365:
5352:
is necessarily 0, as its image is the boundary of the ball, a set of null measure.
1292:
1288:
1209:
1177:
1160:
1124:
984:
732:
304:
7818:. Mathematics and its Applications. Vol. 7. Dordrecht–Boston, MA: D. Reidel.
7117:
5965:
generalizes the Brouwer fixed-point theorem in a different direction: it stays in
4651:
We now use this fact to construct a Sperner coloring. For every triangulation of
279:
8095:
8027:
8003:"Analytic proofs of the 'hairy ball theorem' and the Brouwer fixed-point theorem"
7989:
7963:
7891:
7829:
7802:
7719:
7688:
7661:
7620:
7606:
7589:
7578:. Pure and Applied Mathematics. Vol. 120 (Second ed.). Academic Press.
7562:
7515:
7175:
6763:
6650:
6568:
6350:
6330:
6253:
6117:
5970:
5811:
5771:
is a product of finitely many chainable continua, then every continuous function
2478:
1276:. The theorem can also be found in existence proofs for the solutions of certain
728:
355:
224:
6184:(Volume 2), 2nd edition, A. Hermann & Fils, Paris 1910, pp. 437–477 (French)
5751:
There is also finite-dimensional generalization to a larger class of spaces: If
7861:
7633:
7535:
Boothby, William M. (1971). "On two classical theorems of algebraic topology".
6561:
6290:
General Equilibrium Analysis: Existence and Optimality Properties of Equilibria
5062:
5035:
3596:= 2 can also be proven by contradiction based on a theorem about non-vanishing
1868:
1340:. Several modern accounts of the proof can be found in the literature, notably
991:
274:
in market economies as developed in the 1950s by economics Nobel prize winners
5475:{\displaystyle \displaystyle \sum _{n}(-1)^{n}\operatorname {Tr} (f|H_{n}(B))}
3572:= 2 is less obvious, but can be proven by using basic arguments involving the
1164:
444:
to convex). The following examples show why the pre-conditions are important.
8121:
7760:
7246:
6949:
6177:
5808:
5591:
5587:
5344:
transforms continuously from the identity map of the ball, to the retraction
5285:
Differentiating under the sign of integral it is not difficult to check that
5066:
5051:
5031:
3719:
3331:) are both non-zero). This contradiction proves the fixed point theorem when
1453:
1105:
1054:
867:
693:
503:
with domain . The range of the function is . Thus, f is not an endomorphism.
441:
377:
275:
7705:
6792:
5571:, so this gives a precise description of the strength of Brouwer's theorem.
2359:{\displaystyle H(t,x)={\frac {x-tf(x)}{\sup _{y\in K}\left|y-tf(y)\right|}}}
826:
The theorem has several "real world" illustrations. Here are some examples.
8083:
7089:
7070:
6523:
5804:
3640:
3597:
1257:
1100:. Picard's approach is based on a result that would later be formalised by
1049:? Poincaré discovered that the answer can be found in what we now call the
995:
795:
have a fixed point for the unit disc, since it takes the origin to itself.
410:
7946:
From calculus to cohomology: de Rham cohomology and characteristic classes
7207:
7104:
Kakutani, S. (1941). "A generalization of Brouwer's Fixed Point Theorem".
7002:
on the site Earliest Known Uses of Some of the Words of Mathematics (2007)
6546:
T Gauthier-Villars, Vol 3 p 389 (1892) new edition Paris: Blanchard, 1987.
6365:
5077:
to a fixed point. It is an easy numerical task to follow such a path from
7975:
5373:
5047:
3731:
3715:
1284:
1213:
1205:
1189:
to arbitrary dimension and established the properties connected with the
1066:
1062:
351:
259:
58:
2240:{\displaystyle g(x)={\frac {x-f(x)}{\sup _{y\in K}\left|y-f(y)\right|}}}
1859:
The degree is, roughly speaking, the number of "sheets" of the preimage
8099:
8023:
7752:
7558:
7481:
7411:
6221:
5815:
5741:
5361:
4779:-dimensional simplex whose vertices are colored with the entire set of
1316:
1132:
1058:
970:
815:
776:, which is a continuous function from the unit circle to itself. Since
724:
374:
329:
140:. The simplest forms of Brouwer's theorem are for continuous functions
61:
7390:
David Gale (1979). "The Game of Hex and Brouwer Fixed-Point Theorem".
6344:
Théorèmes du Point Fixe et Applications aux Equations Différentielles
3723:
953:
The Brouwer fixed point theorem was one of the early achievements of
811:
262:. In economics, Brouwer's fixed-point theorem and its extension, the
7921:
7887:
7744:
7731:
Gale, D. (1979). "The Game of Hex and Brouwer Fixed-Point Theorem".
7550:
7403:
3991:. We now give an outline of the proof for the special case in which
3529:
Consequently, F is a special type of continuous function known as a
1319:. Brouwer disavowed his original proof of the fixed-point theorem.
1065:, then the trajectory either becomes stationary, or it approaches a
7576:
An introduction to differentiable manifolds and Riemannian geometry
6998:
6945:
6654:
Encyclopædia Universalis Albin Michel, Paris, 1999, p. 696–706
5595:
3674:
would have to be contractible and its de Rham cohomology in degree
3576:
of the respective spaces: the retraction would induce a surjective
3534:
3343:
odd, one can apply the fixed point theorem to the closed unit ball
2388:
also has degree one at the origin. As a consequence, the preimage
1173:
1148:
1050:
27:
7905:"An integral theorem and its applications to coincidence theorems"
6996:
first appeared 1931 under the pen of David van Dantzig: J. Miller
6498:
5379:
5034:, based on the impossibility of a differentiable retraction. The
4355:{\displaystyle \sum _{i=0}^{n}{P_{i}}=1=\sum _{i=0}^{n}{f(P)_{i}}}
3592:
while the first group is trivial, so this is impossible. The case
3548:
Intuitively it seems unlikely that there could be a retraction of
2806:
is even. If there were a fixed-point-free continuous self-mapping
1053:
properties in the area containing the trajectory. If this area is
394:
An even more general form is better known under a different name:
7360:
7141:
5598:
of square-summable real (or complex) sequences, consider the map
4000:
2578:
sufficiently small, a routine computation shows that the mapping
307:
and the general case for continuous mappings by Brouwer in 1911.
7486:"A Borsuk–Ulam equivalent that directly implies Sperner's lemma"
6518:'s mathematical competition in 1889 for his work on the related
5384:
The Lefschetz fixed-point theorem says that if a continuous map
3474:) are distinct. Because they are distinct, for every point x in
405:
Every continuous function from a nonempty convex compact subset
6912:"The cradle of modern topology, according to Brouwer's inedita"
6871:"The cradle of modern topology, according to Brouwer's inedita"
6833:"The cradle of modern topology, according to Brouwer's inedita"
6502:
CNRS Fédération de Recherche Mathématique du Nord-Pas-de-Calais
3423:
2477:, and then to continuous functions. The more modern advent of
1228:
and is often used to prove other important results such as the
1136:
5332:) (that is, the Lebesgue measure of the image of the ball via
3646:
The impossibility of a retraction can also be shown using the
810:
The continuous function in this theorem is not required to be
7904:
5124:
is a smooth retraction, one considers the smooth deformation
6405:
This citation comes originally from a television broadcast:
1120:
1006:
fixed points guaranteed by Brouwer's theorem are now known.
7702:
A history of algebraic and differential topology, 1900–1960
6724:
A History of Algebraic and Differential Topology, 1900–1960
6412:
4813:
which satisfies the labeling condition in all coordinates:
3670:- 1, and vanishes otherwise. If a retraction existed, then
7348:
7056:
Brouwer's Fixed Point Theorem and the Jordan Curve Theorem
6366:"Why is convexity a requirement for Brouwer fixed points?"
5485:
and in particular if the Lefschetz number is nonzero then
1332:
Brouwer's original 1911 proof relied on the notion of the
1216:
to prove the existence of an equilibrium strategy profile.
945:
respect to its original position on the unfolded string."
341:
This can be generalized to an arbitrary finite dimension:
5304:
is a constant function, which is a contradiction because
5275:{\displaystyle \varphi (t):=\int _{B}\det Dg^{t}(x)\,dx.}
2560:. It can be extended radially to a small spherical shell
2678:. This gives a contradiction, because, if the dimension
2554:
is a continuously differentiable unit tangent vector on
2466:
are precisely the fixed points of the original function
784:
has no fixed point. The analogous example works for the
7673:
Dieudonné, Jean (1982). "8. Les théorèmes de Brouwer".
6173:
Note sur quelques applications de l'indice de Kronecker
3494:(see illustration). By calling this intersection point
3440:
Suppose, for contradiction, that a continuous function
3397:
2713:, it can be uniformly approximated by a polynomial map
2484:
1030:
At the end of the 19th century, the old problem of the
7785:
Homology theory: An introduction to algebraic topology
7192:"L. J. E. Brouwer : Topologie et constructivisme"
6182:
Introduction à la théorie des fonctions d'une variable
7631:
7366:
6667:
Kluwer Academic Publishers (réédition de 2001) p 113
6148:
More exactly, according to Encyclopédie Universalis:
5922:
5876:
5824:
5777:
5757:
5629:
5503:
5402:
5401:
5211:
5130:
5095:
5006:
4986:
4945:
4913:
4893:
4868:
4819:
4799:
4727:
4707:
4687:
4657:
4627:
4597:
4573:
4518:
4491:
4471:
4451:
4407:
4371:
4267:
4219:
4183:
4042:
4009:
3747:
3722:
of sufficiently small support and integral one (i.e.
3129:
2839:
2433:
2394:
2374:
2258:
2151:
2128:
2073:
2042:
2022:
1990:
1924:
1904:
1884:
1756:
1733:
1713:
1693:
1654:
1634:
1614:
1585:
1565:
1541:
1521:
1482:
1462:
1426:
1420:
centered at the origin. Suppose for simplicity that
1397:
1353:
856:
744:
702:
622:
589:
567:
520:
465:
303:-dimensional closed ball was first proved in 1910 by
209:
189:
166:
146:
97:
70:
43:
7909:
Acta Universitatis Carolinae. Mathematica et Physica
6952:
to an open subset of a Euclidean space of dimension
6476:. Dordrecht-Boston, Mass.: D. Reidel Publishing Co.
3490:
and follow the ray until it intersects the boundary
2625:
and that the volume of its image is a polynomial in
680:
have a fixed point for the closed interval , namely
447:
6245:
Applications du lemme de Sperner pour les triangles
5746:
fixed-point theorems in infinite-dimensional spaces
5544:
3458:fixed point. This means that, for every point x in
3247:is a continuous vector field on the unit sphere of
1096:, a contemporary mathematician who generalized the
423:
7252:Topics in Linear and Nonlinear Functional Analysis
6663:Poincaré's theorem is stated in: V. I. Istratescu
5950:
5908:
5862:
5795:
5763:
5726:
5611:) from the closed unit ball of ℓ to the sequence (
5525:
5474:
5274:
5194:
5116:
5015:
4992:
4969:
4928:
4899:
4877:
4854:
4805:
4765:
4713:
4693:
4673:
4633:
4613:
4579:
4556:
4497:
4477:
4457:
4437:
4393:
4354:
4250:
4205:
4166:
4025:
3918:
3710:is smooth, since it can be approximated using the
3230:
2971:
2458:
2419:
2380:
2358:
2239:
2134:
2111:
2055:
2028:
2008:
1976:
1918:be two continuously differentiable functions, and
1910:
1890:
1848:
1739:
1719:
1699:
1675:
1640:
1620:
1600:
1571:
1547:
1535:is non-singular at every point of the preimage of
1527:
1503:
1468:
1444:
1412:
1383:
1235:Besides the fixed-point theorems for more or less
1151:. His initial interest lay in an attempt to solve
768:
715:
661:
597:
575:
550:
492:
215:
195:
172:
152:
132:
83:
49:
4648:coordinates which are not zero on this sub-face.
1264:, a result generalized further by S. Kakutani to
8119:
7922:A First Course in Sobolev Spaces: Second Edition
7605:. Graduate Texts in Mathematics. Vol. 139.
7453:Proceedings of the American Mathematical Society
5553:, Brouwer's theorem can be proved in the system
5237:
3681:
2307:
2191:
1821:
1300:), financial equilibria and incomplete markets.
7943:
7933:. American Mathematical Society. pp. 734.
7298:
6790:
6440:
6163:
6161:
6085:– equivalent to the Brouwer fixed-point theorem
5380:A proof using the Lefschetz fixed-point theorem
2631:. On the other hand, as a contraction mapping,
976:Journal für die reine und angewandte Mathematik
364:A slightly more general version is as follows:
254:and is covered in most introductory courses on
180:in the real numbers to itself or from a closed
7859:
7354:
7036:Kluwer Academic Publishers (new edition 2001)
7015:Kluwer Academic Publishers (new edition 2001)
6683:
6544:Les méthodes nouvelles de la mécanique céleste
6465:
6194:
6192:
6190:
5909:{\displaystyle U_{i}\cap U_{j}\neq \emptyset }
5084:
4365:Hence, by the pigeonhole principle, for every
3560:= 1, the impossibility is more basic, because
2122:If there is no fixed point of the boundary of
1291:used the theorem to prove that in the game of
436:(thus, in particular, bounded and closed) and
428:The theorem holds only for functions that are
5355:
4258:Hence the sum of their coordinates is equal:
6586:Journal de Mathématiques Pures et Appliquées
6158:
5857:
5825:
5658:
5651:
4432:
4414:
3957:) which is isomorphic to the homology group
3564:(i.e., the endpoints of the closed interval
2791:|| is a smooth unit tangent vector field on
1155:. In 1909, during a voyage to Paris, he met
8080:Brouwer's Fixed Point Theorem for Triangles
7840:
7782:
7424:
7153:For context and references see the article
6906:
6865:
6827:
6446:
6423:
6421:
6187:
6073:Infinite compositions of analytic functions
5567:Brouwer's theorem for a square implies the
3678:- 1 would have to vanish, a contradiction.
1092:Poincaré's method was analogous to that of
7981:Topology from the differentiable viewpoint
7813:
7446:
7389:
7249:(2019). "10. The Brouwer mapping degree".
6531:Site du Ministère Culture et Communication
6471:
6286:
3065:) is strictly positive. From the original
2988:has no fixed points, it follows that, for
1683:is defined as the sum of the signs of the
373:Every continuous function from a nonempty
7843:Fixed Points: Algorithms and Applications
7699:
7672:
7655:
7464:
7332:
7088:
6929:
6888:
6850:
6717:
6449:Fixed points: algorithms and applications
6248:Bulletin AMQ, V. XLVI N° 4, (2006) p 17.
6204:"Über Abbildungen von Mannigfaltigkeiten"
5316:(1) is zero. The geometric idea is that
5262:
4069:
3666:– (0) is one-dimensional in degree 0 and
3168:
2945:
2905:
1820:
1400:
1315:, which at the time made a stand against
591:
569:
7730:
7281:
7136:CMI Université Paul Cézanne (2008–2009)
7130:These examples are taken from: F. Boyer
7103:
7068:
6791:Myskis, A. D.; Rabinovic, I. M. (1955).
6582:
6534:
6418:
3982:
3588:, but the latter group is isomorphic to
3428:
3402:The proof uses the observation that the
1204:
1119:
1021:
1013:
780:holds for any point of the unit circle,
258:. It appears in unlikely fields such as
8068:. New York-Toronto-London: McGraw-Hill.
8063:
8045:
7573:
7534:
7479:
7435:
7321:
7310:
7133:Théorèmes de point fixe et applications
6401:
6399:
6397:
6322:Point fixe, et théorèmes du point fixe
6198:
5863:{\displaystyle \{U_{1},\ldots ,U_{m}\}}
5537:acts as the identity on this group, so
5312:-dimensional volume of the ball, while
5195:{\displaystyle g^{t}(x):=tr(x)+(1-t)x,}
5117:{\displaystyle r\colon B\to \partial B}
2773:is polynomial and nowhere vanishing on
1327:
873:
605:is convex and closed, but not bounded.
335:to itself has at least one fixed point.
8120:
8000:
7974:
7944:Madsen, Ib; Tornehave, Jørgen (1997).
7783:Hilton, Peter J.; Wylie, Sean (1960).
7759:
7600:
7343:
7287:
7245:
7233:
7227:
7189:
5602: : ℓ → ℓ which sends a sequence (
5560:, and conversely over the base system
4887:Because the sum of the coordinates of
3704:. In that case it can be assumed that
2532:
1341:
1127:helped Brouwer to formalize his ideas.
662:{\displaystyle f(x)={\frac {x+1}{2}},}
7902:
7378:
7179:Institut Henri Poincaré, Paris (2007)
7071:"Der Fixpunktsatz in Funktionsräumen"
6767:Journal de Mathématiques p 217 (1893)
6363:
6032:Knaster–Kuratowski–Mazurkiewicz lemma
5994:
4621:then by the same argument, the index
3478:, we can construct a unique ray from
2548:. By scaling, it can be assumed that
2511:. (The tangency condition means that
2112:{\displaystyle \deg _{p}f=\deg _{p}g}
1874:The degree satisfies the property of
851:
7632:Chow, Shui Nee; Mallet-Paret, John;
7512:10.4169/amer.math.monthly.120.04.346
7504:10.4169/amer.math.monthly.120.04.346
7059:University of Auckland, New Zealand.
6427:
6394:
6354:Université de Nice-Sophia Antipolis.
5748:for a discussion of these theorems.
5594:. For example, in the Hilbert space
5061:R. Bruce Kellogg, Tien-Yien Li, and
5025:
4438:{\displaystyle j\in \{0,\ldots ,n\}}
4251:{\displaystyle f(P)\in \Delta ^{n}.}
3398:A proof using homology or cohomology
3313:has norm strictly less than 1, then
3283:) is nowhere vanishing (because, if
3253:, satisfying the tangency condition
2684:of the Euclidean space is odd, (1 +
2642:must restrict to a homeomorphism of
2485:A proof using the hairy ball theorem
1384:{\displaystyle K={\overline {B(0)}}}
1244:says that a continuous map from the
561:which is a continuous function from
7367:Chow, Mallet-Paret & Yorke 1978
7258:. Graduate Studies in Mathematics.
7013:Fixed Point Theory. An Introduction
4766:{\displaystyle f(P)_{j}\leq P_{j}.}
4557:{\displaystyle P_{j}\geq f(P)_{j}.}
3650:of open subsets of Euclidean space
3071:-dimensional space Euclidean space
1863:lying over a small open set around
1452:is continuously differentiable. A
1009:
957:, and is the basis of more general
13:
7867:SIAM Journal on Numerical Analysis
7860:Kellogg, R. Bruce; Li, Tien-Yien;
7034:Fixed Point Theory an Introduction
6665:Fixed Point Theory an Introduction
6632:on ]0, 1[ has no fixed point.
5903:
5574:
5108:
4855:{\displaystyle f(P)_{j}\leq P_{j}}
4659:
4599:
4379:
4236:
4191:
4044:
4011:
3778:
3759:
3568:) is not even connected. The case
1977:{\displaystyle H_{t}(x)=tf+(1-t)g}
1260:. This generalization is known as
877:
857:Explanations attributed to Brouwer
14:
8154:
8073:
7733:The American Mathematical Monthly
7657:10.1090/S0025-5718-1978-0492046-9
7491:The American Mathematical Monthly
7466:10.1090/S0002-9939-1956-0078693-4
7392:The American Mathematical Monthly
6960:is a positive integer other than
5388:from a finite simplicial complex
5360:A quite different proof given by
5044:Weierstrass approximation theorem
4505:th coordinate of its image under
4394:{\displaystyle P\in \Delta ^{n},}
4206:{\displaystyle P\in \Delta ^{n},}
3712:Weierstrass approximation theorem
2711:Weierstrass approximation theorem
1559:, every point of the preimage of
1322:
1283:Other areas are also touched. In
994:, they ran contrary to Brouwer's
941:in ; this zero is a fixed point.
350:Every continuous function from a
8041:from the original on 2022-10-09.
6266:Calcul différentiel et géométrie
6130:Calcul différentiel et géométrie
5796:{\displaystyle f:X\rightarrow X}
5545:A proof in a weak logical system
5030:There is also a quick proof, by
4485:is greater than or equal to the
3995:is a function from the standard
3214:
3204:
3194:
3181:
3171:
3142:
3132:
2958:
2948:
2937:
2927:
2908:
2894:
2884:
2874:
2852:
2842:
1413:{\displaystyle \mathbb {R} ^{n}}
821:
424:Importance of the pre-conditions
7927:Graduate Studies in Mathematics
7473:
7440:
7429:
7418:
7383:
7372:
7337:
7326:
7315:
7304:
7292:
7269:from the original on 2022-10-09
7239:
7214:
7182:
7160:
7147:
7124:
7097:
7062:
7047:
7026:
7005:
6986:
6977:J. J. O'Connor E. F. Robertson
6971:
6938:
6900:
6859:
6821:
6813:J. J. O'Connor E. F. Robertson
6807:
6784:
6776:J. J. O'Connor E. F. Robertson
6770:
6745:
6727:. Boston: Birkhäuser. pp.
6711:
6677:
6657:
6635:
6610:
6597:
6575:
6549:
6505:
6490:
6380:
6357:
6335:
5680:
5674:
4641:can be selected from among the
3658:≥ 2, the de Rham cohomology of
3433:Illustration of the retraction
2493:states that on the unit sphere
2427:is not empty. The elements of
1391:denote the closed unit ball in
1115:
870:'s, that guarantee uniqueness.
8133:Theory of continuous functions
8046:Sobolev, Vladimir I. (2001) ,
7814:Istrăţescu, Vasile I. (1981).
6684:Voitsekhovskii, M.I. (2001) ,
6581:This question was studied in:
6313:
6279:
6258:
6236:
6142:
6122:
6100:
6049:Lusternik–Schnirelmann theorem
5938:
5924:
5787:
5520:
5514:
5468:
5465:
5459:
5445:
5438:
5423:
5413:
5259:
5253:
5221:
5215:
5183:
5171:
5165:
5159:
5147:
5141:
5105:
5038:starts by noting that the map
4955:
4949:
4923:
4917:
4830:
4823:
4738:
4731:
4542:
4535:
4342:
4335:
4229:
4223:
3904:
3898:
3872:
3863:
3837:
3831:
3802:
3796:
3580:from the fundamental group of
3222:
3219:
3209:
3186:
3176:
3159:
3153:
3137:
2963:
2953:
2942:
2916:
2902:
2899:
2889:
2863:
2857:
2847:
2453:
2447:
2414:
2408:
2345:
2339:
2301:
2295:
2274:
2262:
2226:
2220:
2185:
2179:
2161:
2155:
1968:
1956:
1941:
1935:
1840:
1824:
1812:
1806:
1776:
1770:
1670:
1664:
1595:
1589:
1498:
1492:
1436:
1372:
1366:
1334:degree of a continuous mapping
1278:partial differential equations
1262:Schauder's fixed-point theorem
1191:degree of a continuous mapping
754:
748:
632:
626:
530:
524:
506:
475:
469:
358:into itself has a fixed point.
293:. Proving results such as the
133:{\displaystyle f(x_{0})=x_{0}}
114:
101:
1:
7841:Karamardian, S., ed. (1977).
7528:
7260:American Mathematical Society
7196:Revue d'Histoire des Sciences
7188:For a long explanation, see:
7118:10.1215/S0012-7094-41-00838-4
6447:Karamardian, Stephan (1977).
5981:Lefschetz fixed-point theorem
5818:has a finite open refinement
5065:turned Hirsch's proof into a
3987:The BFPT can be proved using
3682:A proof using Stokes' theorem
2824:-dimensional Euclidean space
2009:{\displaystyle 0\leq t\leq 1}
1254:Lefschetz fixed-point theorem
1032:stability of the solar system
1000:constructivism in mathematics
800:Lefschetz fixed-point theorem
608:
266:, play a central role in the
20:Brouwer's fixed-point theorem
7986:University Press of Virginia
7574:Boothby, William M. (1986).
7355:Kellogg, Li & Yorke 1976
6980:Luitzen Egbertus Jan Brouwer
6931:10.1016/0315-0860(75)90111-1
6890:10.1016/0315-0860(75)90111-1
6852:10.1016/0315-0860(75)90111-1
6816:Luitzen Egbertus Jan Brouwer
6528:Célébrations nationales 2004
6451:. New York: Academic Press.
6287:Florenzano, Monique (2003).
6128:See page 15 of: D. Leborgne
5963:Kakutani fixed point theorem
5489:must have a fixed point. If
4674:{\displaystyle \Delta ^{n},}
4614:{\displaystyle \Delta ^{n},}
4026:{\displaystyle \Delta ^{n},}
3356:dimensions and the mapping
3077:, construct a new auxiliary
2538:In fact, suppose first that
1376:
1200:
687:
598:{\displaystyle \mathbb {R} }
576:{\displaystyle \mathbb {R} }
401:Schauder fixed point theorem
310:
264:Kakutani fixed-point theorem
64:to itself, there is a point
7:
8143:Theorems in convex geometry
8112:Brouwer Fixed Point Theorem
8053:Encyclopedia of Mathematics
7299:Madsen & Tornehave 1997
6691:Encyclopedia of Mathematics
6644:Poincaré, Henri (1854–1912)
6472:Istrăţescu, Vasile (1981).
6056:
6022:Brouwer fixed-point theorem
5951:{\displaystyle |i-j|\leq 1}
5340:passes from 0 to 1 the map
5085:A proof using oriented area
3271:) = 0. Moreover,
2546:continuously differentiable
1102:another fixed-point theorem
10:
8159:
8064:Spanier, Edwin H. (1966).
7950:Cambridge University Press
7789:Cambridge University Press
7643:Mathematics of Computation
6797:Успехи математических наук
6605:Poincaré–Bendixson theorem
6329:December 26, 2008, at the
6116:December 26, 2008, at the
6094:
6063:Banach fixed-point theorem
5356:A proof using the game Hex
5324:) is the oriented area of
4681:the color of every vertex
2525:= 0 for every unit vector
2016:. Suppose that the point
979:). It was later proved by
948:
931:intermediate value theorem
295:Poincaré–Bendixson theorem
7903:Kulpa, Władysław (1989).
7106:Duke Mathematical Journal
7053:E.g.: S. Greenwood J. Cao
6559:taken from: P. A. Miquel
6089:Topological combinatorics
4591:-dimensional sub-face of
3718:with non-negative smooth
2459:{\displaystyle g^{-1}(0)}
2420:{\displaystyle g^{-1}(0)}
1676:{\displaystyle p\in B(0)}
1555:. In particular, by the
1504:{\displaystyle p\in B(0)}
1336:, stemming from ideas in
551:{\displaystyle f(x)=x+1,}
417:itself has a fixed point.
388:itself has a fixed point.
34:. It states that for any
32:L. E. J. (Bertus) Brouwer
8001:Milnor, John W. (1978).
7919:Leoni, Giovanni (2017).
7700:Dieudonné, Jean (1989).
7601:Bredon, Glen E. (1993).
6562:La catégorie de désordre
6264:Page 15 of: D. Leborgne
6083:Poincaré–Miranda theorem
5526:{\displaystyle H_{0}(B)}
5364:is based on the game of
5202:and the smooth function
3944:de Rham cohomology group
3929:giving a contradiction.
3734:on the boundary then by
3502:), we define a function
3307:) is non-zero; while if
2812:of the closed unit ball
2690:) is not a polynomial.
1557:inverse function theorem
1445:{\displaystyle f:K\to K}
1098:Cauchy–Lipschitz theorem
1082:Encyclopædia Universalis
969:= 3 first was proved by
805:
493:{\displaystyle f(x)=x+1}
384:of a Euclidean space to
7449:"A fixed point theorem"
7425:Hilton & Wylie 1960
7222:constructive set theory
6944:If an open subset of a
6293:. Springer. p. 7.
6109:Théorèmes du point fixe
6068:Fixed-point computation
4970:{\displaystyle f(P)=P.}
4401:there must be an index
3028:, the scalar product
3016:) is non-zero; and for
2797:, a contradiction.
2703:unit tangent vector on
1270:Hartman-Grobman theorem
1248:-dimensional sphere to
1153:Hilbert's fifth problem
961:which are important in
769:{\displaystyle f(x)=-x}
244:invariance of dimension
160:from a closed interval
8106:Reconstructing Brouwer
7767:. New York: Springer.
7190:Dubucs, J. P. (1988).
7174:June 11, 2011, at the
7090:10.4064/sm-2-1-171-180
6603:This follows from the
6106:E.g. F & V Bayart
5969:, but considers upper
5952:
5910:
5864:
5797:
5765:
5728:
5527:
5476:
5276:
5196:
5118:
5017:
4994:
4971:
4930:
4901:
4879:
4856:
4807:
4767:
4715:
4695:
4675:
4635:
4615:
4581:
4558:
4499:
4479:
4459:
4439:
4395:
4356:
4330:
4288:
4252:
4207:
4168:
4108:
4027:
3920:
3541:) is a fixed point of
3437:
3232:
2973:
2460:
2421:
2382:
2360:
2241:
2136:
2113:
2057:
2036:is a regular value of
2030:
2010:
1978:
1912:
1892:
1871:to higher dimensions.
1850:
1741:
1721:
1707:over the preimages of
1701:
1677:
1642:
1622:
1602:
1573:
1549:
1529:
1505:
1470:
1446:
1414:
1385:
1217:
1128:
1027:
1019:
973:in 1904 (published in
882:
770:
717:
663:
613:Consider the function
599:
577:
552:
511:Consider the function
494:
456:Consider the function
252:differential equations
217:
197:
174:
154:
134:
85:
51:
7765:Differential Topology
7603:Topology and geometry
7208:10.3406/rhs.1988.4094
7069:Schauder, J. (1930).
6496:See F. Brechenmacher
6252:June 8, 2011, at the
6209:Mathematische Annalen
5953:
5911:
5865:
5798:
5766:
5729:
5528:
5477:
5277:
5197:
5119:
5018:
4995:
4972:
4931:
4902:
4880:
4857:
4808:
4768:
4716:
4696:
4676:
4636:
4616:
4582:
4559:
4500:
4480:
4460:
4440:
4396:
4357:
4310:
4268:
4253:
4208:
4169:
4088:
4028:
3983:A combinatorial proof
3921:
3533:: every point of the
3432:
3233:
2974:
2461:
2422:
2383:
2361:
2250:is well-defined, and
2242:
2142:, then the function
2137:
2114:
2058:
2056:{\displaystyle H_{t}}
2031:
2011:
1979:
1913:
1893:
1851:
1742:
1722:
1702:
1678:
1643:
1623:
1603:
1574:
1550:
1530:
1506:
1471:
1447:
1415:
1386:
1338:differential topology
1274:Central Limit Theorem
1226:topological manifolds
1208:
1123:
1025:
1017:
925:and ≤ 0 on
881:
771:
718:
716:{\displaystyle D^{n}}
664:
600:
578:
553:
495:
256:differential geometry
218:
198:
175:
155:
135:
86:
84:{\displaystyle x_{0}}
52:
8138:Theorems in topology
8128:Fixed-point theorems
8102:with attached proof.
7708:. pp. 166–203.
6917:Historia Mathematica
6876:Historia Mathematica
6838:Historia Mathematica
6430:J. Reine Angew. Math
6368:. Math StackExchange
6341:C. Minazzo K. Rider
5974:set-valued functions
5920:
5874:
5822:
5775:
5755:
5627:
5581:fixed-point theorems
5501:
5399:
5209:
5128:
5093:
5004:
5000:is a fixed point of
4984:
4943:
4929:{\displaystyle f(P)}
4911:
4891:
4866:
4817:
4797:
4725:
4705:
4685:
4655:
4625:
4595:
4571:
4516:
4489:
4469:
4449:
4405:
4369:
4265:
4217:
4181:
4040:
4007:
3745:
3625:) is trivial, while
3127:
3086:)-dimensional space
2837:
2431:
2392:
2372:
2256:
2149:
2126:
2071:
2040:
2020:
1988:
1922:
1902:
1882:
1754:
1731:
1711:
1691:
1685:Jacobian determinant
1652:
1632:
1612:
1601:{\displaystyle B(0)}
1583:
1563:
1539:
1519:
1480:
1460:
1424:
1395:
1351:
1328:A proof using degree
1266:set-valued functions
1230:Jordan curve theorem
1212:used the theorem in
1187:Jordan curve theorem
1038:, who worked on the
959:fixed point theorems
921:. It is ≥ 0 on
874:One-dimensional case
742:
700:
620:
587:
565:
518:
463:
291:Charles Émile Picard
236:Jordan curve theorem
232:fixed-point theorems
207:
187:
164:
144:
95:
68:
41:
8011:Amer. Math. Monthly
7984:. Charlottesville:
7880:1976SJNA...13..473K
7538:Amer. Math. Monthly
7480:Nyman, Kathryn L.;
7447:Eldon Dyer (1956).
6999:Topological algebra
6415:, 21 septembre 1999
6319:V. & F. Bayart
6039:Borsuk–Ulam theorem
5671:
5551:reverse mathematics
5541:has a fixed point.
5495:simplicial homology
4150: for all
3698:onto its boundary ∂
3390:require tools from
3388:Borsuk-Ulam theorem
3102:, with coordinates
2617:contraction mapping
1876:homotopy invariance
1648:at a regular value
1242:Borsuk–Ulam theorem
963:functional analysis
844:shaken, not stirred
326:continuous function
272:general equilibrium
248:Borsuk–Ulam theorem
57:mapping a nonempty
36:continuous function
24:fixed-point theorem
16:Theorem in topology
8094:2007-03-19 at the
8066:Algebraic topology
7845:. Academic Press.
7816:Fixed Point Theory
7675:Éléments d'analyse
7482:Su, Francis Edward
7076:Studia Mathematica
6994:algebraic topology
6762:2011-07-16 at the
6649:2010-10-08 at the
6616:Multiplication by
6567:2016-03-03 at the
6520:three-body problem
6474:Fixed point theory
6349:2018-04-04 at the
6222:10.1007/BF01456931
6010:Algebraic topology
6001:algebraic topology
5995:Equivalent results
5948:
5906:
5860:
5793:
5761:
5724:
5657:
5569:weak Kőnig's lemma
5523:
5472:
5471:
5412:
5272:
5192:
5114:
5016:{\displaystyle f.}
5013:
4990:
4967:
4926:
4897:
4878:{\displaystyle j.}
4875:
4852:
4803:
4786:available colors.
4763:
4711:
4691:
4671:
4631:
4611:
4577:
4554:
4495:
4475:
4455:
4435:
4391:
4352:
4248:
4203:
4164:
4023:
3916:
3648:de Rham cohomology
3578:group homomorphism
3574:fundamental groups
3556:, and in the case
3438:
3392:algebraic topology
3228:
2969:
2779:; by construction
2491:hairy ball theorem
2456:
2417:
2378:
2356:
2321:
2237:
2205:
2132:
2109:
2053:
2026:
2006:
1974:
1908:
1888:
1846:
1816:
1737:
1717:
1697:
1673:
1638:
1628:). The degree of
1618:
1598:
1569:
1545:
1525:
1501:
1466:
1442:
1410:
1381:
1222:fixed-point theory
1218:
1195:algebraic topology
1169:hairy ball theorem
1145:mathematical logic
1129:
1040:three-body problem
1028:
1020:
955:algebraic topology
883:
852:Intuitive approach
766:
713:
659:
595:
573:
548:
490:
452:as an endomorphism
370:Convex compact set
347:In Euclidean space
268:proof of existence
240:hairy ball theorem
230:Among hundreds of
213:
193:
170:
150:
130:
81:
47:
8048:"Brouwer theorem"
7939:978-1-4704-2921-8
7852:978-0-12-398050-2
7825:978-90-277-1224-0
7774:978-0-387-90148-0
7761:Hirsch, Morris W.
7144:(August 1, 2010).
7011:V. I. Istratescu
6908:Freudenthal, Hans
6867:Freudenthal, Hans
6829:Freudenthal, Hans
6751:See for example:
6738:978-0-8176-3388-2
6686:"Brouwer theorem"
6483:978-90-277-1224-0
6458:978-0-12-398050-2
6325:on Bibmath.net.
6200:Brouwer, L. E. J.
6054:
6053:
5985:singular homology
5764:{\displaystyle X}
5713:
5678:
5672:
5403:
5376:theorem for Hex.
5026:A proof by Hirsch
4993:{\displaystyle P}
4900:{\displaystyle P}
4806:{\displaystyle P}
4714:{\displaystyle j}
4694:{\displaystyle P}
4634:{\displaystyle j}
4580:{\displaystyle P}
4498:{\displaystyle j}
4478:{\displaystyle P}
4465:th coordinate of
4458:{\displaystyle j}
4151:
4130:
4033:to itself, where
3977:de Rham's theorem
3289:has norm 1, then
2381:{\displaystyle g}
2354:
2306:
2235:
2190:
2135:{\displaystyle K}
2029:{\displaystyle p}
1911:{\displaystyle g}
1891:{\displaystyle f}
1782:
1740:{\displaystyle f}
1720:{\displaystyle p}
1700:{\displaystyle f}
1641:{\displaystyle f}
1621:{\displaystyle K}
1608:(the interior of
1572:{\displaystyle f}
1548:{\displaystyle p}
1528:{\displaystyle f}
1469:{\displaystyle f}
1379:
1087:fundamental group
654:
216:{\displaystyle K}
196:{\displaystyle D}
173:{\displaystyle I}
153:{\displaystyle f}
50:{\displaystyle f}
8150:
8069:
8060:
8042:
8040:
8007:
7997:
7971:
7916:
7899:
7856:
7837:
7810:
7778:
7756:
7727:
7696:
7669:
7659:
7650:(143): 887–899.
7628:
7597:
7570:
7523:
7522:
7477:
7471:
7470:
7468:
7444:
7438:
7433:
7427:
7422:
7416:
7415:
7387:
7381:
7376:
7370:
7364:
7358:
7352:
7346:
7341:
7335:
7330:
7324:
7319:
7313:
7308:
7302:
7301:, pp. 39–48
7296:
7290:
7285:
7279:
7278:
7276:
7274:
7268:
7257:
7243:
7237:
7231:
7225:
7218:
7212:
7211:
7186:
7180:
7164:
7158:
7155:Hex (board game)
7151:
7145:
7128:
7122:
7121:
7101:
7095:
7094:
7092:
7066:
7060:
7051:
7045:
7030:
7024:
7009:
7003:
6990:
6984:
6975:
6969:
6942:
6936:
6935:
6933:
6904:
6898:
6897:
6892:
6863:
6857:
6856:
6854:
6825:
6819:
6811:
6805:
6804:
6788:
6782:
6774:
6768:
6749:
6743:
6742:
6715:
6709:
6708:
6681:
6675:
6661:
6655:
6639:
6633:
6631:
6629:
6628:
6625:
6622:
6614:
6608:
6601:
6595:
6594:
6579:
6573:
6553:
6547:
6538:
6532:
6509:
6503:
6494:
6488:
6487:
6469:
6463:
6462:
6444:
6438:
6437:
6425:
6416:
6403:
6392:
6384:
6378:
6377:
6375:
6373:
6361:
6355:
6339:
6333:
6317:
6311:
6310:
6308:
6307:
6283:
6277:
6262:
6256:
6240:
6234:
6233:
6196:
6185:
6168:Jacques Hadamard
6165:
6156:
6146:
6140:
6126:
6120:
6112:on Bibm@th.net
6104:
6078:Nash equilibrium
6007:
6006:
5957:
5955:
5954:
5949:
5941:
5927:
5915:
5913:
5912:
5907:
5899:
5898:
5886:
5885:
5869:
5867:
5866:
5861:
5856:
5855:
5837:
5836:
5802:
5800:
5799:
5794:
5770:
5768:
5767:
5762:
5733:
5731:
5730:
5725:
5714:
5711:
5709:
5708:
5690:
5689:
5679:
5676:
5673:
5670:
5665:
5644:
5639:
5638:
5532:
5530:
5529:
5524:
5513:
5512:
5481:
5479:
5478:
5473:
5458:
5457:
5448:
5431:
5430:
5411:
5290:
5281:
5279:
5278:
5273:
5252:
5251:
5236:
5235:
5201:
5199:
5198:
5193:
5140:
5139:
5123:
5121:
5120:
5115:
5022:
5020:
5019:
5014:
4999:
4997:
4996:
4991:
4976:
4974:
4973:
4968:
4935:
4933:
4932:
4927:
4906:
4904:
4903:
4898:
4884:
4882:
4881:
4876:
4861:
4859:
4858:
4853:
4851:
4850:
4838:
4837:
4812:
4810:
4809:
4804:
4785:
4772:
4770:
4769:
4764:
4759:
4758:
4746:
4745:
4720:
4718:
4717:
4712:
4700:
4698:
4697:
4692:
4680:
4678:
4677:
4672:
4667:
4666:
4647:
4640:
4638:
4637:
4632:
4620:
4618:
4617:
4612:
4607:
4606:
4586:
4584:
4583:
4578:
4563:
4561:
4560:
4555:
4550:
4549:
4528:
4527:
4504:
4502:
4501:
4496:
4484:
4482:
4481:
4476:
4464:
4462:
4461:
4456:
4444:
4442:
4441:
4436:
4400:
4398:
4397:
4392:
4387:
4386:
4361:
4359:
4358:
4353:
4351:
4350:
4349:
4329:
4324:
4300:
4299:
4298:
4287:
4282:
4257:
4255:
4254:
4249:
4244:
4243:
4212:
4210:
4209:
4204:
4199:
4198:
4177:For every point
4173:
4171:
4170:
4165:
4160:
4156:
4152:
4149:
4141:
4140:
4131:
4128:
4120:
4119:
4118:
4107:
4102:
4084:
4083:
4072:
4052:
4051:
4032:
4030:
4029:
4024:
4019:
4018:
3974:
3968:
3956:
3950:
3941:
3937:
3925:
3923:
3922:
3917:
3897:
3896:
3887:
3886:
3862:
3861:
3852:
3851:
3830:
3829:
3817:
3816:
3795:
3794:
3785:
3784:
3766:
3765:
3729:
3709:
3703:
3697:
3691:
3611:: the homology
3453:
3385:
3379:
3373:
3367:
3361:
3355:
3348:
3342:
3336:
3330:
3324:
3318:
3312:
3306:
3300:
3294:
3282:
3276:
3270:
3264:
3258:
3252:
3246:
3241:By construction
3237:
3235:
3234:
3229:
3218:
3217:
3208:
3207:
3198:
3197:
3185:
3184:
3175:
3174:
3146:
3145:
3136:
3135:
3119:
3113:
3107:
3097:
3091:
3085:
3076:
3070:
3064:
3058:
3052:
3046:
3040:
3034:
3027:
3021:
3015:
3009:
3003:
2993:
2987:
2978:
2976:
2975:
2970:
2962:
2961:
2952:
2951:
2941:
2940:
2931:
2930:
2912:
2911:
2898:
2897:
2888:
2887:
2878:
2877:
2856:
2855:
2846:
2845:
2829:
2823:
2817:
2811:
2805:
2796:
2790:
2784:
2778:
2772:
2766:
2760:
2754:
2748:
2742:
2736:
2730:
2724:
2718:
2708:
2698:
2689:
2683:
2677:
2671:
2665:
2659:
2653:
2647:
2641:
2630:
2624:
2614:
2600:
2594:
2588:
2577:
2571:
2565:
2559:
2553:
2543:
2530:
2524:
2510:
2504:
2498:
2465:
2463:
2462:
2457:
2446:
2445:
2426:
2424:
2423:
2418:
2407:
2406:
2387:
2385:
2384:
2379:
2365:
2363:
2362:
2357:
2355:
2353:
2352:
2348:
2320:
2304:
2281:
2246:
2244:
2243:
2238:
2236:
2234:
2233:
2229:
2204:
2188:
2168:
2141:
2139:
2138:
2133:
2118:
2116:
2115:
2110:
2102:
2101:
2083:
2082:
2062:
2060:
2059:
2054:
2052:
2051:
2035:
2033:
2032:
2027:
2015:
2013:
2012:
2007:
1983:
1981:
1980:
1975:
1934:
1933:
1917:
1915:
1914:
1909:
1897:
1895:
1894:
1889:
1855:
1853:
1852:
1847:
1839:
1838:
1815:
1805:
1804:
1766:
1765:
1746:
1744:
1743:
1738:
1726:
1724:
1723:
1718:
1706:
1704:
1703:
1698:
1682:
1680:
1679:
1674:
1647:
1645:
1644:
1639:
1627:
1625:
1624:
1619:
1607:
1605:
1604:
1599:
1578:
1576:
1575:
1570:
1554:
1552:
1551:
1546:
1534:
1532:
1531:
1526:
1510:
1508:
1507:
1502:
1475:
1473:
1472:
1467:
1451:
1449:
1448:
1443:
1419:
1417:
1416:
1411:
1409:
1408:
1403:
1390:
1388:
1387:
1382:
1380:
1375:
1361:
1305:not constructive
1178:Hans Freudenthal
1161:Jacques Hadamard
1125:Jacques Hadamard
1010:Before discovery
989:non-constructive
985:Jacques Hadamard
981:L. E. J. Brouwer
775:
773:
772:
767:
722:
720:
719:
714:
712:
711:
668:
666:
665:
660:
655:
650:
639:
604:
602:
601:
596:
594:
582:
580:
579:
574:
572:
557:
555:
554:
549:
499:
497:
496:
491:
305:Jacques Hadamard
302:
222:
220:
219:
214:
202:
200:
199:
194:
179:
177:
176:
171:
159:
157:
156:
151:
139:
137:
136:
131:
129:
128:
113:
112:
90:
88:
87:
82:
80:
79:
56:
54:
53:
48:
8158:
8157:
8153:
8152:
8151:
8149:
8148:
8147:
8118:
8117:
8114:at Math Images.
8096:Wayback Machine
8089:Brouwer theorem
8076:
8038:
8005:
7976:Milnor, John W.
7960:
7888:10.1137/0713041
7862:Yorke, James A.
7853:
7826:
7799:
7775:
7745:10.2307/2320146
7739:(10): 818–827.
7716:
7685:
7634:Yorke, James A.
7617:
7607:Springer-Verlag
7586:
7551:10.2307/2317520
7531:
7526:
7478:
7474:
7445:
7441:
7434:
7430:
7423:
7419:
7404:10.2307/2320146
7398:(10): 818–827.
7388:
7384:
7377:
7373:
7365:
7361:
7353:
7349:
7342:
7338:
7331:
7327:
7320:
7316:
7309:
7305:
7297:
7293:
7286:
7282:
7272:
7270:
7266:
7255:
7244:
7240:
7236:, pp. 1–19
7232:
7228:
7219:
7215:
7187:
7183:
7176:Wayback Machine
7165:
7161:
7152:
7148:
7129:
7125:
7102:
7098:
7067:
7063:
7052:
7048:
7031:
7027:
7010:
7006:
6991:
6987:
6976:
6972:
6943:
6939:
6924:(4): 495–502 .
6905:
6901:
6883:(4): 495–502 .
6864:
6860:
6845:(4): 495–502 .
6826:
6822:
6812:
6808:
6789:
6785:
6775:
6771:
6764:Wayback Machine
6750:
6746:
6739:
6719:Dieudonné, Jean
6716:
6712:
6706:
6682:
6678:
6662:
6658:
6651:Wayback Machine
6640:
6636:
6626:
6623:
6620:
6619:
6617:
6615:
6611:
6602:
6598:
6580:
6576:
6569:Wayback Machine
6555:Quotation from
6554:
6550:
6539:
6535:
6510:
6506:
6495:
6491:
6484:
6470:
6466:
6459:
6445:
6441:
6436:(3/4): 179–276.
6426:
6419:
6404:
6395:
6385:
6381:
6371:
6369:
6362:
6358:
6351:Wayback Machine
6340:
6336:
6331:Wayback Machine
6318:
6314:
6305:
6303:
6301:
6284:
6280:
6263:
6259:
6254:Wayback Machine
6241:
6237:
6197:
6188:
6166:
6159:
6147:
6143:
6127:
6123:
6118:Wayback Machine
6105:
6101:
6097:
6059:
6027:Sperner's lemma
5997:
5971:hemi-continuous
5937:
5923:
5921:
5918:
5917:
5916:if and only if
5894:
5890:
5881:
5877:
5875:
5872:
5871:
5851:
5847:
5832:
5828:
5823:
5820:
5819:
5814:of which every
5812:Hausdorff space
5776:
5773:
5772:
5756:
5753:
5752:
5712: for
5710:
5698:
5694:
5685:
5681:
5675:
5666:
5661:
5643:
5634:
5630:
5628:
5625:
5624:
5619:
5610:
5577:
5575:Generalizations
5565:
5558:
5547:
5508:
5504:
5502:
5499:
5498:
5453:
5449:
5444:
5426:
5422:
5407:
5400:
5397:
5396:
5382:
5358:
5288:
5247:
5243:
5231:
5227:
5210:
5207:
5206:
5135:
5131:
5129:
5126:
5125:
5094:
5091:
5090:
5087:
5028:
5005:
5002:
5001:
4985:
4982:
4981:
4944:
4941:
4940:
4912:
4909:
4908:
4892:
4889:
4888:
4867:
4864:
4863:
4846:
4842:
4833:
4829:
4818:
4815:
4814:
4798:
4795:
4794:
4780:
4754:
4750:
4741:
4737:
4726:
4723:
4722:
4706:
4703:
4702:
4686:
4683:
4682:
4662:
4658:
4656:
4653:
4652:
4642:
4626:
4623:
4622:
4602:
4598:
4596:
4593:
4592:
4572:
4569:
4568:
4545:
4541:
4523:
4519:
4517:
4514:
4513:
4490:
4487:
4486:
4470:
4467:
4466:
4450:
4447:
4446:
4406:
4403:
4402:
4382:
4378:
4370:
4367:
4366:
4345:
4341:
4331:
4325:
4314:
4294:
4290:
4289:
4283:
4272:
4266:
4263:
4262:
4239:
4235:
4218:
4215:
4214:
4194:
4190:
4182:
4179:
4178:
4148:
4136:
4132:
4129: and
4127:
4114:
4110:
4109:
4103:
4092:
4073:
4068:
4067:
4060:
4056:
4047:
4043:
4041:
4038:
4037:
4014:
4010:
4008:
4005:
4004:
3989:Sperner's lemma
3985:
3970:
3967:
3958:
3952:
3946:
3939:
3933:
3892:
3888:
3882:
3878:
3857:
3853:
3847:
3843:
3825:
3821:
3812:
3808:
3790:
3786:
3777:
3773:
3758:
3754:
3746:
3743:
3742:
3736:Stokes' theorem
3727:
3705:
3699:
3693:
3687:
3684:
3634:
3620:
3609:homology groups
3441:
3400:
3381:
3375:
3369:
3363:
3357:
3350:
3344:
3338:
3332:
3326:
3320:
3314:
3308:
3302:
3296:
3290:
3288:
3278:
3272:
3266:
3260:
3254:
3248:
3242:
3213:
3212:
3203:
3202:
3193:
3192:
3180:
3179:
3170:
3169:
3141:
3140:
3131:
3130:
3128:
3125:
3124:
3115:
3109:
3103:
3093:
3087:
3080:
3078:
3072:
3066:
3060:
3054:
3048:
3042:
3036:
3030:
3029:
3023:
3017:
3011:
3005:
2999:
2989:
2983:
2957:
2956:
2947:
2946:
2936:
2935:
2926:
2925:
2907:
2906:
2893:
2892:
2883:
2882:
2873:
2872:
2851:
2850:
2841:
2840:
2838:
2835:
2834:
2825:
2819:
2813:
2807:
2801:
2792:
2786:
2780:
2774:
2768:
2762:
2756:
2750:
2744:
2738:
2732:
2726:
2720:
2714:
2704:
2694:
2685:
2679:
2673:
2667:
2661:
2655:
2649:
2643:
2640:
2632:
2626:
2620:
2602:
2596:
2590:
2587:
2579:
2573:
2567:
2561:
2555:
2549:
2539:
2526:
2512:
2506:
2500:
2494:
2487:
2479:homology theory
2438:
2434:
2432:
2429:
2428:
2399:
2395:
2393:
2390:
2389:
2373:
2370:
2369:
2326:
2322:
2310:
2305:
2282:
2280:
2257:
2254:
2253:
2210:
2206:
2194:
2189:
2169:
2167:
2150:
2147:
2146:
2127:
2124:
2123:
2097:
2093:
2078:
2074:
2072:
2069:
2068:
2047:
2043:
2041:
2038:
2037:
2021:
2018:
2017:
1989:
1986:
1985:
1929:
1925:
1923:
1920:
1919:
1903:
1900:
1899:
1883:
1880:
1879:
1834:
1830:
1797:
1793:
1786:
1761:
1757:
1755:
1752:
1751:
1732:
1729:
1728:
1712:
1709:
1708:
1692:
1689:
1688:
1653:
1650:
1649:
1633:
1630:
1629:
1613:
1610:
1609:
1584:
1581:
1580:
1564:
1561:
1560:
1540:
1537:
1536:
1520:
1517:
1516:
1481:
1478:
1477:
1461:
1458:
1457:
1425:
1422:
1421:
1404:
1399:
1398:
1396:
1393:
1392:
1362:
1360:
1352:
1349:
1348:
1330:
1325:
1298:Hotelling's law
1203:
1118:
1012:
992:indirect proofs
951:
898:(light green).
876:
859:
854:
824:
808:
743:
740:
739:
707:
703:
701:
698:
697:
690:
640:
638:
621:
618:
617:
611:
590:
588:
585:
584:
568:
566:
563:
562:
519:
516:
515:
509:
464:
461:
460:
454:
426:
356:Euclidean space
313:
298:
225:Euclidean space
208:
205:
204:
188:
185:
184:
165:
162:
161:
145:
142:
141:
124:
120:
108:
104:
96:
93:
92:
75:
71:
69:
66:
65:
42:
39:
38:
17:
12:
11:
5:
8156:
8146:
8145:
8140:
8135:
8130:
8116:
8115:
8109:
8103:
8086:
8075:
8074:External links
8072:
8071:
8070:
8061:
8043:
8018:(7): 521–524.
7998:
7972:
7958:
7941:
7917:
7900:
7874:(4): 473–483.
7857:
7851:
7838:
7824:
7811:
7797:
7780:
7773:
7757:
7728:
7714:
7697:
7683:
7670:
7629:
7615:
7598:
7584:
7571:
7545:(3): 237–249.
7530:
7527:
7525:
7524:
7498:(4): 346–354,
7472:
7459:(4): 662–672.
7439:
7428:
7417:
7382:
7371:
7359:
7347:
7336:
7333:Dieudonné 1982
7325:
7314:
7303:
7291:
7280:
7247:Teschl, Gerald
7238:
7226:
7213:
7202:(2): 133–155.
7181:
7159:
7146:
7123:
7112:(3): 457–459.
7096:
7061:
7046:
7025:
7004:
6985:
6970:
6937:
6899:
6858:
6820:
6806:
6799:(in Russian).
6783:
6769:
6744:
6737:
6710:
6704:
6676:
6656:
6634:
6609:
6596:
6574:
6557:Henri Poincaré
6548:
6541:Henri Poincaré
6533:
6516:King of Sweden
6512:Henri Poincaré
6504:
6489:
6482:
6464:
6457:
6439:
6417:
6393:
6389:Henri Poincaré
6379:
6356:
6334:
6312:
6299:
6278:
6257:
6235:
6186:
6157:
6153:Luizen Brouwer
6141:
6121:
6098:
6096:
6093:
6092:
6091:
6086:
6080:
6075:
6070:
6065:
6058:
6055:
6052:
6051:
6046:
6044:Tucker's lemma
6041:
6035:
6034:
6029:
6024:
6018:
6017:
6014:
6011:
5996:
5993:
5947:
5944:
5940:
5936:
5933:
5930:
5926:
5905:
5902:
5897:
5893:
5889:
5884:
5880:
5859:
5854:
5850:
5846:
5843:
5840:
5835:
5831:
5827:
5792:
5789:
5786:
5783:
5780:
5760:
5735:
5734:
5723:
5720:
5717:
5707:
5704:
5701:
5697:
5693:
5688:
5684:
5669:
5664:
5660:
5656:
5653:
5650:
5647:
5642:
5637:
5633:
5615:
5606:
5576:
5573:
5563:
5556:
5546:
5543:
5522:
5519:
5516:
5511:
5507:
5483:
5482:
5470:
5467:
5464:
5461:
5456:
5452:
5447:
5443:
5440:
5437:
5434:
5429:
5425:
5421:
5418:
5415:
5410:
5406:
5381:
5378:
5357:
5354:
5296:) = 0 for all
5283:
5282:
5271:
5268:
5265:
5261:
5258:
5255:
5250:
5246:
5242:
5239:
5234:
5230:
5226:
5223:
5220:
5217:
5214:
5191:
5188:
5185:
5182:
5179:
5176:
5173:
5170:
5167:
5164:
5161:
5158:
5155:
5152:
5149:
5146:
5143:
5138:
5134:
5113:
5110:
5107:
5104:
5101:
5098:
5086:
5083:
5063:James A. Yorke
5056:Sard's theorem
5052:bump functions
5036:indirect proof
5027:
5024:
5012:
5009:
4989:
4978:
4977:
4966:
4963:
4960:
4957:
4954:
4951:
4948:
4925:
4922:
4919:
4916:
4896:
4874:
4871:
4849:
4845:
4841:
4836:
4832:
4828:
4825:
4822:
4802:
4762:
4757:
4753:
4749:
4744:
4740:
4736:
4733:
4730:
4710:
4690:
4670:
4665:
4661:
4630:
4610:
4605:
4601:
4576:
4565:
4564:
4553:
4548:
4544:
4540:
4537:
4534:
4531:
4526:
4522:
4494:
4474:
4454:
4445:such that the
4434:
4431:
4428:
4425:
4422:
4419:
4416:
4413:
4410:
4390:
4385:
4381:
4377:
4374:
4363:
4362:
4348:
4344:
4340:
4337:
4334:
4328:
4323:
4320:
4317:
4313:
4309:
4306:
4303:
4297:
4293:
4286:
4281:
4278:
4275:
4271:
4247:
4242:
4238:
4234:
4231:
4228:
4225:
4222:
4202:
4197:
4193:
4189:
4186:
4175:
4174:
4163:
4159:
4155:
4147:
4144:
4139:
4135:
4126:
4123:
4117:
4113:
4106:
4101:
4098:
4095:
4091:
4087:
4082:
4079:
4076:
4071:
4066:
4063:
4059:
4055:
4050:
4046:
4022:
4017:
4013:
3984:
3981:
3962:
3942:generates the
3927:
3926:
3915:
3912:
3909:
3906:
3903:
3900:
3895:
3891:
3885:
3881:
3877:
3874:
3871:
3868:
3865:
3860:
3856:
3850:
3846:
3842:
3839:
3836:
3833:
3828:
3824:
3820:
3815:
3811:
3807:
3804:
3801:
3798:
3793:
3789:
3783:
3780:
3776:
3772:
3769:
3764:
3761:
3757:
3753:
3750:
3720:bump functions
3692:from the ball
3683:
3680:
3639:) is infinite
3629:
3615:
3537:(in this case
3399:
3396:
3284:
3239:
3238:
3227:
3224:
3221:
3216:
3211:
3206:
3201:
3196:
3191:
3188:
3183:
3178:
3173:
3167:
3164:
3161:
3158:
3155:
3152:
3149:
3144:
3139:
3134:
2980:
2979:
2968:
2965:
2960:
2955:
2950:
2944:
2939:
2934:
2929:
2924:
2921:
2918:
2915:
2910:
2904:
2901:
2896:
2891:
2886:
2881:
2876:
2871:
2868:
2865:
2862:
2859:
2854:
2849:
2844:
2636:
2583:
2486:
2483:
2455:
2452:
2449:
2444:
2441:
2437:
2416:
2413:
2410:
2405:
2402:
2398:
2377:
2351:
2347:
2344:
2341:
2338:
2335:
2332:
2329:
2325:
2319:
2316:
2313:
2309:
2303:
2300:
2297:
2294:
2291:
2288:
2285:
2279:
2276:
2273:
2270:
2267:
2264:
2261:
2248:
2247:
2232:
2228:
2225:
2222:
2219:
2216:
2213:
2209:
2203:
2200:
2197:
2193:
2187:
2184:
2181:
2178:
2175:
2172:
2166:
2163:
2160:
2157:
2154:
2131:
2108:
2105:
2100:
2096:
2092:
2089:
2086:
2081:
2077:
2050:
2046:
2025:
2005:
2002:
1999:
1996:
1993:
1973:
1970:
1967:
1964:
1961:
1958:
1955:
1952:
1949:
1946:
1943:
1940:
1937:
1932:
1928:
1907:
1887:
1869:winding number
1857:
1856:
1845:
1842:
1837:
1833:
1829:
1826:
1823:
1819:
1814:
1811:
1808:
1803:
1800:
1796:
1792:
1789:
1785:
1781:
1778:
1775:
1772:
1769:
1764:
1760:
1736:
1716:
1696:
1672:
1669:
1666:
1663:
1660:
1657:
1637:
1617:
1597:
1594:
1591:
1588:
1568:
1544:
1524:
1511:such that the
1500:
1497:
1494:
1491:
1488:
1485:
1465:
1441:
1438:
1435:
1432:
1429:
1407:
1402:
1378:
1374:
1371:
1368:
1365:
1359:
1356:
1329:
1326:
1324:
1323:Proof outlines
1321:
1309:constructivity
1202:
1199:
1157:Henri Poincaré
1117:
1114:
1104:, named after
1078:analysis situs
1036:Henri Poincaré
1011:
1008:
950:
947:
917:) −
875:
872:
858:
855:
853:
850:
849:
848:
839:
836:
823:
820:
807:
804:
794:
765:
762:
759:
756:
753:
750:
747:
710:
706:
694:homeomorphisms
689:
686:
679:
670:
669:
658:
653:
649:
646:
643:
637:
634:
631:
628:
625:
610:
607:
593:
571:
559:
558:
547:
544:
541:
538:
535:
532:
529:
526:
523:
508:
505:
501:
500:
489:
486:
483:
480:
477:
474:
471:
468:
453:
446:
425:
422:
421:
420:
419:
418:
403:
392:
391:
390:
389:
371:
362:
361:
360:
359:
348:
339:
338:
337:
336:
322:
312:
309:
287:Henri Poincaré
212:
192:
169:
149:
127:
123:
119:
116:
111:
107:
103:
100:
78:
74:
46:
30:, named after
15:
9:
6:
4:
3:
2:
8155:
8144:
8141:
8139:
8136:
8134:
8131:
8129:
8126:
8125:
8123:
8113:
8110:
8107:
8104:
8101:
8097:
8093:
8090:
8087:
8085:
8081:
8078:
8077:
8067:
8062:
8059:
8055:
8054:
8049:
8044:
8037:
8033:
8029:
8025:
8021:
8017:
8013:
8012:
8004:
7999:
7995:
7991:
7987:
7983:
7982:
7977:
7973:
7969:
7965:
7961:
7959:0-521-58059-5
7955:
7951:
7947:
7942:
7940:
7936:
7932:
7928:
7924:
7923:
7918:
7914:
7910:
7906:
7901:
7897:
7893:
7889:
7885:
7881:
7877:
7873:
7869:
7868:
7863:
7858:
7854:
7848:
7844:
7839:
7835:
7831:
7827:
7821:
7817:
7812:
7808:
7804:
7800:
7794:
7790:
7786:
7781:
7776:
7770:
7766:
7762:
7758:
7754:
7750:
7746:
7742:
7738:
7734:
7729:
7725:
7721:
7717:
7715:0-8176-3388-X
7711:
7707:
7703:
7698:
7694:
7690:
7686:
7684:2-04-011499-8
7680:
7676:
7671:
7667:
7663:
7658:
7653:
7649:
7645:
7644:
7639:
7635:
7630:
7626:
7622:
7618:
7616:0-387-97926-3
7612:
7608:
7604:
7599:
7595:
7591:
7587:
7585:0-12-116052-1
7581:
7577:
7572:
7568:
7564:
7560:
7556:
7552:
7548:
7544:
7540:
7539:
7533:
7532:
7521:
7517:
7513:
7509:
7505:
7501:
7497:
7493:
7492:
7487:
7483:
7476:
7467:
7462:
7458:
7454:
7450:
7443:
7437:
7432:
7426:
7421:
7413:
7409:
7405:
7401:
7397:
7393:
7386:
7380:
7375:
7368:
7363:
7356:
7351:
7345:
7340:
7334:
7329:
7323:
7318:
7312:
7307:
7300:
7295:
7289:
7284:
7265:
7261:
7254:
7253:
7248:
7242:
7235:
7230:
7223:
7217:
7209:
7205:
7201:
7197:
7193:
7185:
7178:
7177:
7173:
7170:
7163:
7156:
7150:
7143:
7139:
7138:Archived copy
7135:
7134:
7127:
7119:
7115:
7111:
7107:
7100:
7091:
7086:
7082:
7078:
7077:
7072:
7065:
7058:
7057:
7050:
7043:
7042:1-4020-0301-3
7039:
7035:
7029:
7022:
7021:1-4020-0301-3
7018:
7014:
7008:
7001:
7000:
6995:
6989:
6982:
6981:
6974:
6967:
6963:
6959:
6955:
6951:
6947:
6941:
6932:
6927:
6923:
6919:
6918:
6913:
6909:
6903:
6896:
6891:
6886:
6882:
6878:
6877:
6872:
6868:
6862:
6853:
6848:
6844:
6840:
6839:
6834:
6830:
6824:
6818:
6817:
6810:
6803:(3): 188–192.
6802:
6798:
6794:
6787:
6781:
6780:
6773:
6766:
6765:
6761:
6758:
6754:
6748:
6740:
6734:
6730:
6726:
6725:
6720:
6714:
6707:
6705:1-4020-0609-8
6701:
6697:
6693:
6692:
6687:
6680:
6674:
6673:1-4020-0301-3
6670:
6666:
6660:
6653:
6652:
6648:
6645:
6638:
6613:
6606:
6600:
6593:(4): 167–244.
6592:
6588:
6587:
6578:
6571:
6570:
6566:
6563:
6558:
6552:
6545:
6542:
6537:
6530:
6529:
6525:
6521:
6517:
6513:
6508:
6501:
6500:
6493:
6485:
6479:
6475:
6468:
6460:
6454:
6450:
6443:
6435:
6431:
6424:
6422:
6414:
6410:
6409:
6402:
6400:
6398:
6390:
6383:
6367:
6360:
6353:
6352:
6348:
6345:
6338:
6332:
6328:
6324:
6323:
6316:
6302:
6300:9781402075124
6296:
6292:
6291:
6282:
6275:
6274:2-13-037495-6
6271:
6267:
6261:
6255:
6251:
6247:
6246:
6239:
6231:
6227:
6223:
6219:
6215:
6212:(in German).
6211:
6210:
6205:
6201:
6195:
6193:
6191:
6183:
6179:
6178:Jules Tannery
6175:
6174:
6169:
6164:
6162:
6155:by G. Sabbagh
6154:
6151:
6145:
6139:
6138:2-13-037495-6
6135:
6131:
6125:
6119:
6115:
6111:
6110:
6103:
6099:
6090:
6087:
6084:
6081:
6079:
6076:
6074:
6071:
6069:
6066:
6064:
6061:
6060:
6050:
6047:
6045:
6042:
6040:
6037:
6036:
6033:
6030:
6028:
6025:
6023:
6020:
6019:
6016:Set covering
6015:
6013:Combinatorics
6012:
6009:
6008:
6005:
6002:
5992:
5990:
5986:
5982:
5977:
5975:
5972:
5968:
5964:
5959:
5945:
5942:
5934:
5931:
5928:
5900:
5895:
5891:
5887:
5882:
5878:
5852:
5848:
5844:
5841:
5838:
5833:
5829:
5817:
5813:
5810:
5806:
5790:
5784:
5781:
5778:
5758:
5749:
5747:
5743:
5738:
5721:
5718:
5715:
5705:
5702:
5699:
5695:
5691:
5686:
5682:
5667:
5662:
5654:
5648:
5645:
5640:
5635:
5631:
5623:
5622:
5621:
5620:) defined by
5618:
5614:
5609:
5605:
5601:
5597:
5593:
5589:
5588:Hilbert space
5584:
5582:
5572:
5570:
5566:
5559:
5552:
5542:
5540:
5536:
5517:
5509:
5505:
5496:
5492:
5488:
5462:
5454:
5450:
5441:
5435:
5432:
5427:
5419:
5416:
5408:
5404:
5395:
5394:
5393:
5391:
5387:
5377:
5375:
5371:
5367:
5363:
5353:
5351:
5347:
5343:
5339:
5335:
5331:
5327:
5323:
5319:
5315:
5311:
5307:
5303:
5299:
5295:
5291:
5269:
5266:
5263:
5256:
5248:
5244:
5240:
5232:
5228:
5224:
5218:
5212:
5205:
5204:
5203:
5189:
5186:
5180:
5177:
5174:
5168:
5162:
5156:
5153:
5150:
5144:
5136:
5132:
5111:
5102:
5099:
5096:
5082:
5080:
5076:
5072:
5068:
5064:
5059:
5057:
5053:
5049:
5045:
5041:
5037:
5033:
5032:Morris Hirsch
5023:
5010:
5007:
4987:
4964:
4961:
4958:
4952:
4946:
4939:
4938:
4937:
4920:
4914:
4894:
4885:
4872:
4869:
4847:
4843:
4839:
4834:
4826:
4820:
4800:
4792:
4787:
4783:
4778:
4773:
4760:
4755:
4751:
4747:
4742:
4734:
4728:
4708:
4688:
4668:
4663:
4649:
4645:
4628:
4608:
4603:
4590:
4574:
4567:Moreover, if
4551:
4546:
4538:
4532:
4529:
4524:
4520:
4512:
4511:
4510:
4508:
4492:
4472:
4452:
4429:
4426:
4423:
4420:
4417:
4411:
4408:
4388:
4383:
4375:
4372:
4346:
4338:
4332:
4326:
4321:
4318:
4315:
4311:
4307:
4304:
4301:
4295:
4291:
4284:
4279:
4276:
4273:
4269:
4261:
4260:
4259:
4245:
4240:
4232:
4226:
4220:
4200:
4195:
4187:
4184:
4161:
4157:
4153:
4145:
4142:
4137:
4133:
4124:
4121:
4115:
4111:
4104:
4099:
4096:
4093:
4089:
4085:
4080:
4077:
4074:
4064:
4061:
4057:
4053:
4048:
4036:
4035:
4034:
4020:
4015:
4002:
3998:
3994:
3990:
3980:
3978:
3973:
3965:
3961:
3955:
3949:
3945:
3936:
3930:
3913:
3910:
3907:
3901:
3893:
3889:
3883:
3879:
3875:
3869:
3866:
3858:
3854:
3848:
3844:
3840:
3834:
3826:
3822:
3818:
3813:
3809:
3805:
3799:
3791:
3787:
3781:
3774:
3770:
3767:
3762:
3755:
3751:
3748:
3741:
3740:
3739:
3737:
3733:
3725:
3721:
3717:
3713:
3708:
3702:
3696:
3690:
3679:
3677:
3673:
3669:
3665:
3661:
3657:
3653:
3649:
3644:
3642:
3638:
3632:
3628:
3624:
3618:
3614:
3610:
3606:
3601:
3599:
3598:vector fields
3595:
3591:
3587:
3583:
3579:
3575:
3571:
3567:
3563:
3559:
3555:
3551:
3546:
3544:
3540:
3536:
3532:
3527:
3525:
3521:
3517:
3513:
3510: →
3509:
3506: :
3505:
3501:
3497:
3493:
3489:
3485:
3481:
3477:
3473:
3469:
3465:
3462:, the points
3461:
3457:
3452:
3448:
3444:
3436:
3431:
3427:
3425:
3421:
3417:
3413:
3409:
3405:
3395:
3393:
3389:
3384:
3378:
3372:
3366:
3360:
3353:
3347:
3341:
3337:is even. For
3335:
3329:
3323:
3317:
3311:
3305:
3299:
3293:
3287:
3281:
3275:
3269:
3263:
3257:
3251:
3245:
3225:
3199:
3189:
3165:
3162:
3156:
3150:
3147:
3123:
3122:
3121:
3118:
3112:
3106:
3101:
3096:
3090:
3083:
3075:
3069:
3063:
3057:
3051:
3045:
3039:
3033:
3026:
3020:
3014:
3008:
3004:, the vector
3002:
2997:
2992:
2986:
2966:
2932:
2922:
2919:
2913:
2879:
2869:
2866:
2860:
2833:
2832:
2831:
2828:
2822:
2816:
2810:
2804:
2798:
2795:
2789:
2783:
2777:
2771:
2765:
2759:
2753:
2747:
2741:
2735:
2729:
2723:
2717:
2712:
2707:
2702:
2697:
2691:
2688:
2682:
2676:
2670:
2664:
2658:
2652:
2646:
2639:
2635:
2629:
2623:
2618:
2612:
2608:
2605:
2599:
2593:
2586:
2582:
2576:
2570:
2564:
2558:
2552:
2547:
2542:
2536:
2534:
2533:Milnor (1978)
2529:
2523:
2519:
2515:
2509:
2503:
2497:
2492:
2482:
2480:
2476:
2471:
2469:
2450:
2442:
2439:
2435:
2411:
2403:
2400:
2396:
2375:
2366:
2349:
2342:
2336:
2333:
2330:
2327:
2323:
2317:
2314:
2311:
2298:
2292:
2289:
2286:
2283:
2277:
2271:
2268:
2265:
2259:
2251:
2230:
2223:
2217:
2214:
2211:
2207:
2201:
2198:
2195:
2182:
2176:
2173:
2170:
2164:
2158:
2152:
2145:
2144:
2143:
2129:
2120:
2106:
2103:
2098:
2094:
2090:
2087:
2084:
2079:
2075:
2066:
2048:
2044:
2023:
2003:
2000:
1997:
1994:
1991:
1971:
1965:
1962:
1959:
1953:
1950:
1947:
1944:
1938:
1930:
1926:
1905:
1885:
1877:
1872:
1870:
1866:
1862:
1843:
1835:
1831:
1827:
1817:
1809:
1801:
1798:
1794:
1790:
1787:
1783:
1779:
1773:
1767:
1762:
1758:
1750:
1749:
1748:
1734:
1714:
1694:
1686:
1667:
1661:
1658:
1655:
1635:
1615:
1592:
1586:
1566:
1558:
1542:
1522:
1514:
1495:
1489:
1486:
1483:
1463:
1455:
1454:regular value
1439:
1433:
1430:
1427:
1405:
1369:
1363:
1357:
1354:
1345:
1343:
1342:Milnor (1965)
1339:
1335:
1320:
1318:
1314:
1310:
1306:
1301:
1299:
1294:
1290:
1286:
1281:
1279:
1275:
1271:
1267:
1263:
1259:
1258:Banach spaces
1255:
1251:
1247:
1243:
1238:
1233:
1231:
1227:
1223:
1215:
1211:
1207:
1198:
1196:
1192:
1188:
1182:
1179:
1175:
1170:
1166:
1162:
1158:
1154:
1150:
1146:
1140:
1138:
1134:
1126:
1122:
1113:
1111:
1107:
1103:
1099:
1095:
1090:
1088:
1083:
1080:. The French
1079:
1074:
1072:
1068:
1064:
1060:
1056:
1052:
1048:
1043:
1041:
1037:
1033:
1024:
1016:
1007:
1005:
1002:, methods to
1001:
997:
993:
990:
986:
982:
978:
977:
972:
968:
964:
960:
956:
946:
942:
940:
936:
932:
928:
924:
920:
916:
912:
908:
904:
899:
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880:
871:
869:
868:Stefan Banach
863:
845:
840:
837:
834:
829:
828:
827:
822:Illustrations
819:
817:
813:
803:
801:
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787:
783:
779:
763:
760:
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733:without holes
730:
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481:
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466:
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458:
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448:The function
445:
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430:endomorphisms
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301:
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288:
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281:
280:Gérard Debreu
277:
276:Kenneth Arrow
273:
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8108:at MathPages
8084:cut-the-knot
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7912:
7908:
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7787:. New York:
7784:
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7641:
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7575:
7542:
7536:
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7436:Spanier 1966
7431:
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7362:
7350:
7339:
7328:
7322:Boothby 1986
7317:
7311:Boothby 1971
7306:
7294:
7283:
7271:. Retrieved
7251:
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6950:homeomorphic
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6753:Émile Picard
6747:
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6526:
6524:Jacques Tits
6507:
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6382:
6370:. Retrieved
6359:
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6304:. Retrieved
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6242:D. Violette
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1313:intuitionism
1302:
1282:
1249:
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1219:
1183:
1141:
1130:
1116:First proofs
1094:Émile Picard
1091:
1077:
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1070:
1057:, i.e. both
1044:
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996:intuitionist
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414:
411:Banach space
406:
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321:In the plane
314:
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284:
229:
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7915:(2): 83–90.
7344:Hirsch 1988
7288:Milnor 1978
7234:Milnor 1965
7083:: 171–180.
6364:Belk, Jim.
6268:Puf (1982)
6132:Puf (1982)
5374:determinacy
5308:(0) is the
3732:volume form
3584:to that of
1476:is a point
1285:game theory
1237:contracting
1214:game theory
1165:Émile Borel
1110:contraction
1067:limit cycle
1051:topological
1004:approximate
965:. The case
905:which maps
727:, bounded,
507:Boundedness
352:closed ball
260:game theory
227:to itself.
8122:Categories
8100:PlanetMath
7798:0521094224
7706:Birkhäuser
7529:References
7379:Kulpa 1989
7273:1 February
6779:Piers Bohl
6306:2016-03-08
6216:: 97–115.
5816:open cover
5497:group is:
5362:David Gale
5067:computable
5048:convolving
4721:such that
4587:lies on a
3724:mollifying
3716:convolving
3531:retraction
3522:) must be
2701:continuous
2699:is only a
2666:onto (1 +
2648:onto (1 +
1317:set theory
1133:Piers Bohl
971:Piers Bohl
929:. By the
816:surjective
609:Closedness
91:such that
62:convex set
8058:EMS Press
6992:The term
6956:, and if
6696:EMS Press
6408:Archimède
6230:177796823
5943:≤
5932:−
5904:∅
5901:≠
5888:∩
5842:…
5788:→
5742:convexity
5719:≥
5703:−
5677: and
5659:‖
5652:‖
5649:−
5436:
5417:−
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5229:∫
5213:φ
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5106:→
5100::
4980:That is,
4840:≤
4748:≤
4660:Δ
4600:Δ
4530:≥
4424:…
4412:∈
4380:Δ
4376:∈
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4233:∈
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4188:∈
4143:≥
4090:∑
4086:∣
4065:∈
4045:Δ
4012:Δ
3894:∗
3880:∫
3870:ω
3859:∗
3845:∫
3835:ω
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3800:ω
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3775:∫
3768:ω
3760:∂
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3163:−
2933:⋅
2923:−
2914:−
2880:⋅
2870:−
2709:, by the
2440:−
2401:−
2331:−
2315:∈
2287:−
2215:−
2199:∈
2174:−
2104:
2085:
2001:≤
1995:≤
1963:−
1799:−
1791:∈
1784:∑
1768:
1659:∈
1487:∈
1437:→
1377:¯
1289:John Nash
1210:John Nash
1201:Reception
983:in 1909.
812:bijective
761:−
735:, etc.).
729:connected
688:Convexity
684:(1) = 1.
311:Statement
8092:Archived
8036:Archived
7978:(1965).
7763:(1988).
7636:(1978).
7484:(2013),
7264:Archived
7172:Archived
7166:P. Bich
6946:manifold
6910:(1975).
6869:(1975).
6831:(1975).
6760:Archived
6721:(1989).
6647:Archived
6565:Archived
6514:won the
6347:Archived
6327:Archived
6250:Archived
6202:(1911).
6114:Archived
6057:See also
6004:column.
4862:for all
4789:Because
3535:codomain
3445: :
3404:boundary
3047:) = 1 –
2996:interior
2067:. Then
2063:for all
1579:lies in
1513:Jacobian
1174:homotopy
1149:topology
246:and the
28:topology
8098:, from
8032:0505523
8024:2320860
7994:0226651
7968:1454127
7896:0416010
7876:Bibcode
7834:0620639
7807:0115161
7753:2320146
7724:0995842
7693:0658305
7666:0492046
7625:1224675
7594:0861409
7567:0283792
7559:2317520
7520:3035127
7412:2320146
7142:WebCite
6630:
6618:
5809:compact
5592:compact
4001:simplex
3418:, the (
3406:of the
3120:). Set
2994:in the
2818:of the
2767:. Thus
2572:. For
1137:Latvian
1063:bounded
1055:compact
949:History
434:compact
380:subset
378:compact
328:from a
59:compact
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3714:or by
3654:. For
3641:cyclic
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3410:-disk
2982:Since
2830:, set
1878:: let
1727:under
1163:, and
1106:Banach
1059:closed
937:has a
725:closed
438:convex
375:convex
330:closed
324:Every
242:, the
238:, the
8039:(PDF)
8020:JSTOR
8006:(PDF)
7749:JSTOR
7555:JSTOR
7508:JSTOR
7408:JSTOR
7267:(PDF)
7256:(PDF)
6729:17–24
6226:S2CID
6095:Notes
5300:, so
4213:also
3975:) by
3730:is a
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3374:) = (
2660:and
2615:is a
806:Notes
409:of a
354:of a
22:is a
7954:ISBN
7935:ISBN
7847:ISBN
7820:ISBN
7793:ISBN
7769:ISBN
7710:ISBN
7679:ISBN
7611:ISBN
7580:ISBN
7275:2022
7038:ISBN
7017:ISBN
6733:ISBN
6700:ISBN
6669:ISBN
6478:ISBN
6453:ISBN
6413:Arte
6374:2015
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5979:The
5961:The
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1984:for
1898:and
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1061:and
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939:zero
793:does
778:-x≠x
678:does
440:(or
333:disk
289:and
278:and
182:disk
8082:at
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7884:doi
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