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Product (category theory)

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required for the definition of the limit. The discrete objects will serve as the index of the components and projections. If we regard this diagram as a functor, it is a functor from the index set
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How this functor maps objects is obvious. Mapping of morphisms is subtle, because the product of morphisms defined above does not fit. First, consider the binary product functor, which is a
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is one in which this morphism is actually an isomorphism. Thus in a distributive category, there is the canonical isomorphism
3655: 4069: 3747: 4440: 3134: 4595: 1666: 3611: 2862:{\displaystyle \prod _{i\in I}X_{i}:=\left\{\left(x_{i}\right)_{i\in I}:x_{i}\in X_{i}{\text{ for all }}i\in I\right\}} 2638: 2565: 2241: 5702: 4995: 4967: 4907: 4854: 3000:{\displaystyle \pi _{j}:\prod _{i\in I}X_{i}\to X_{j},\quad \pi _{j}\left(\left(x_{i}\right)_{i\in I}\right):=x_{j}.} 1620: 2179: 1752: 4434: 3275: 2129:
considered as a discrete category. The definition of the product then coincides with the definition of the limit,
1152: 594: 3079: 2207: 1237: 4986:. Encyclopedia of mathematics and its applications 50–51, 53 . Vol. 1. Cambridge University Press. p.  3227: 3215: 1967: 860: 811: 754: 3369: 2515: 537: 5048: 4956: 4544:
guarantees the existence of unique arrows filling out the following diagram (the induced arrows are dashed):
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the product is the Cartesian product with addition defined componentwise and distributive multiplication.
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can be treated as a category, using the order relation as the morphisms. In this case the products and
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Alternatively, the product may be defined through equations. So, for example, for the binary product:
5630: 5274: 5135: 5015: 4781: 2106: 5661: 5617: 5222: 5041: 4557: 3279: 3268: 1829: 35: 3404: 2185: 5217: 5199: 4769: 4763: 2715:, the product (in the category theoretic sense) is the Cartesian product. Given a family of sets 2098: 1789: 5424: 5190: 5170: 5093: 4987: 4980: 4747: 3218:, the product is the space whose underlying set is the Cartesian product and which carries the 2175: 2163: 2132: 39: 4790: – Most general completion of a commutative square given two morphisms with same codomain 1451: 939: 912: 5306: 5145: 4655: 4391: 3342: 3286: 2495: 1483: 687: 3426: 2396: 1045: 1016: 656: 5118: 5113: 4787: 2718: 2344: 1125: 1098: 965: 629: 225: 198: 148: 121: 976: 8: 5462: 5410: 5336: 5140: 4203: 3234: 587: 59: 4927: 4880: 4182: 3240: 2105:(a family of objects without any morphisms, other than their identity morphisms) as the 1212: 252: 175: 98: 5316: 5311: 5293: 5175: 5150: 4547: 4162: 4142: 3588: 3568: 3545: 3494: 3462: 3366:
An example in which the product does not exist: In the category of fields, the product
3354: 3350: 3264: 3010: 2618: 2598: 2489: 2471: 2376: 2321: 2112: 1947: 1732: 1382: 1362: 1289: 1075: 996: 609: 420: 410: 63: 4281:{\displaystyle X\times (Y\times Z)\simeq (X\times Y)\times Z\simeq X\times Y\times Z,} 5625: 5562: 5550: 5452: 5377: 5372: 5326: 5108: 5103: 4991: 4963: 4946: 4903: 4850: 4132:(although some authors use this phrase to mean "a category with all finite limits"). 3301: 3223: 2102: 71: 51: 47: 5586: 5472: 5447: 5382: 5367: 5362: 5301: 5130: 5098: 4753: 3885:{\displaystyle \left\langle f_{1}\circ \pi _{1},f_{2}\circ \pi _{2}\right\rangle .} 3219: 2712: 2272: 2236: 67: 42:
is a notion designed to capture the essence behind constructions in other areas of
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A category where every finite set of objects has a product is sometimes called a
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which generates examples of products in the category of finite sets. Written by
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Commutativity of the diagrams above is guaranteed by the equality: for all
1935:{\displaystyle \pi _{i}\circ \left\langle f_{1},f_{2}\right\rangle =f_{i}} 5540: 5520: 5392: 5262: 4159:
is a Cartesian category, product functors have been chosen as above, and
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given by the Cartesian product with multiplication defined componentwise.
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Instead of two objects, we can start with an arbitrary family of objects
43: 5021: 4772: – Set of arguments where two or more functions have the same value 5572: 5510: 5123: 3331: 2311:{\displaystyle \Delta :\mathbf {C} \to \mathbf {C} \times \mathbf {C} } 4892: 5566: 5257: 4743: 4503: 3649: 3480: 3346: 3327: 1206: 5635: 5267: 5165: 4926:. Les Publications CRM Montreal (publication PM023). Archived from 4378:; a Cartesian category with its finite products is an example of a 3401:
does not exist, since there is no field with homomorphisms to both
79: 5033: 4506:. To see this, note that the universal property of the coproduct 5605: 5595: 5244: 5155: 3606: 4374:
These properties are formally similar to those of a commutative
2178:, so is the product. Starting with the definition given for the 5600: 4375: 4433:
of a category with finite products and coproducts, there is a
5482: 4059:{\displaystyle \prod _{i\in I}X_{i}\to \prod _{i\in I}Y_{i}.} 3896:. Second, consider the general product functor. For families 684: 4828:"Banach spaces (and Lawvere metrics, and closed categories)" 4728:{\displaystyle X\times (Y+Z)\simeq (X\times Y)+(X\times Z).} 5025: 4872: 3585:
is a set such that all products for families indexed with
3491:, do not have a terminal object: given any infinite group 4893:
Adámek, Jiří; Horst Herrlich; George E. Strecker (1990).
3737:{\displaystyle f_{1}:X_{1}\to Y_{1},f_{2}:X_{2}\to Y_{2}} 690:, because of the universal property, so one may speak of 4849:(1st ed.). New York: Springer-Verlag. p. 37. 4792:
Pages displaying short descriptions of redirect targets
4119:{\displaystyle \left\{f_{i}\circ \pi _{i}\right\}_{i}.} 3806:{\displaystyle X_{1}\times X_{2}\to Y_{1}\times Y_{2}.} 78:
of objects is the "most general" object which admits a
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induced by the dashed arrows in the above diagram. A
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is another product, there exists a unique isomorphism
4664: 4598: 4560: 4512: 4495:{\displaystyle X\times Y+X\times Z\to X\times (Y+Z),} 4443: 4402: 4339: 4293: 4211: 4185: 4165: 4145: 4072: 3997: 3902: 3819: 3750: 3658: 3614: 3591: 3571: 3548: 3517: 3497: 3465: 3429: 3407: 3372: 3243: 3201:{\displaystyle f(y):=\left(f_{i}(y)\right)_{i\in I}.} 3137: 3082: 3033: 3013: 2875: 2748: 2721: 2641: 2621: 2601: 2568: 2518: 2498: 2474: 2434: 2399: 2379: 2347: 2324: 2280: 2244: 2210: 2188: 2135: 2115: 2024: 1970: 1950: 1872: 1832: 1792: 1755: 1735: 1669: 1623: 1576: 1530: 1486: 1454: 1405: 1385: 1365: 1312: 1292: 1240: 1215: 1155: 1128: 1101: 1078: 1048: 1019: 999: 979: 942: 915: 863: 814: 757: 700: 659: 632: 612: 540: 491: 443: 423: 369: 321: 278: 255: 228: 201: 178: 151: 124: 101: 4647:{\displaystyle X\times Y+X\times Z\to X\times (Y+Z)} 1711:{\displaystyle \langle f_{1},\ldots ,f_{n}\rangle .} 2204:as the discrete category with two objects, so that 4979: 4727: 4646: 4584: 4536: 4494: 4425: 4366: 4327:{\displaystyle X\times 1\simeq 1\times X\simeq X,} 4326: 4280: 4194: 4171: 4151: 4118: 4058: 3983: 3884: 3805: 3736: 3640: 3597: 3577: 3554: 3534: 3503: 3471: 3445: 3415: 3393: 3252: 3200: 3123: 3068: 3019: 2999: 2861: 2734: 2695: 2627: 2607: 2587: 2554: 2504: 2480: 2460: 2420: 2385: 2365: 2330: 2310: 2263: 2227: 2196: 2154: 2121: 2081: 2011: 1956: 1934: 1859: 1818: 1776: 1741: 1710: 1655: 1609: 1562: 1501: 1472: 1440: 1391: 1371: 1347: 1298: 1274: 1224: 1190: 1141: 1114: 1084: 1064: 1035: 1005: 985: 955: 928: 898: 849: 800: 743: 675: 645: 618: 578: 526: 478: 429: 401: 356: 307: 264: 241: 214: 187: 164: 137: 110: 4916: 3641:{\displaystyle \mathbf {C} ^{I}\to \mathbf {C} .} 2696:{\displaystyle (X,X)\to \left(X_{1},X_{2}\right)} 2166:and projections being the limit (limiting cone). 1480:such that the following diagrams commute for all 1200: 5694: 2588:{\displaystyle \mathbf {C} \times \mathbf {C} .} 2264:{\displaystyle \mathbf {C} \times \mathbf {C} .} 3487:, and some categories, such as the category of 1656:{\displaystyle X_{1}\times \cdots \times X_{n}} 4813:Introduction to Higher-Order Categorical Logic 2595:This universal morphism consists of an object 1777:{\displaystyle \langle \cdot ,\cdot \rangle .} 1355:satisfying the following universal property: 5049: 4825: 3605:exist, then one can treat each product as a 2143: 2136: 1851: 1839: 1768: 1756: 1749:is guaranteed by existence of the operation 1702: 1670: 1601: 1583: 1191:{\displaystyle \langle f_{1},f_{2}\rangle .} 1182: 1156: 694:product. This has the following meaning: if 4784: – Type of category in category theory 3124:{\displaystyle f:Y\to \prod _{i\in I}X_{i}} 2228:{\displaystyle \mathbf {C} ^{\mathbf {J} }} 2174:Just as the limit is a special case of the 1275:{\displaystyle \left(X_{i}\right)_{i\in I}} 5677: 5667: 5423: 5056: 5042: 4876:Category Theory – Lecture Notes for ESSLLI 4815:. Cambridge University Press. p. 304. 4367:{\displaystyle X\times Y\simeq Y\times X.} 3519: 3409: 3374: 2012:{\displaystyle g:Y\to X_{1}\times X_{2},} 899:{\displaystyle \pi _{2}'=\pi _{2}\circ h} 850:{\displaystyle \pi _{1}'=\pi _{1}\circ h} 801:{\displaystyle h:X'\to X_{1}\times X_{2}} 90: 4952:Categories for the Working Mathematician 4945: 4868: 4866: 4847:Categories for the working mathematician 3394:{\displaystyle \mathbb {Q} \times F_{p}} 2555:{\displaystyle \left(X_{1},X_{2}\right)} 1720: 1663:and the product of morphisms is denoted 579:{\displaystyle f:Y\to X_{1}\times X_{2}} 4977: 4778: – Construction in category theory 1964:is guaranteed by the equality: for all 606:Whether a product exists may depend on 5695: 4819: 4554:The universal property of the product 3892:This operation on morphisms is called 744:{\displaystyle X',\pi _{1}',\pi _{2}'} 5422: 5075: 5037: 4920:Category Theory for Computing Science 4917:Barr, Michael; Charles Wells (1999). 4863: 4502:where the plus sign here denotes the 3349:correspond to greatest lower bounds ( 2169: 1563:{\displaystyle \prod _{i\in I}X_{i}.} 16:Generalized object in category theory 4873:Michael Barr, Charles Wells (1999). 4844: 3511:there are infinitely many morphisms 1348:{\displaystyle \pi _{i}:X\to X_{i},} 993:alliterates with projection. Given 357:{\displaystyle \pi _{1}:X\to X_{1},} 5063: 4537:{\displaystyle X\times Y+X\times Z} 4426:{\displaystyle X,Y,{\text{ and }}Z} 4066:We choose the product of morphisms 2097:The product is a special case of a 402:{\displaystyle \pi _{2}:X\to X_{2}} 13: 4592:then guarantees a unique morphism 4546: 3535:{\displaystyle \mathbb {Z} \to G,} 3226:for which all the projections are 2499: 2281: 1610:{\displaystyle I=\{1,\ldots ,n\},} 1511: 593: 315:equipped with a pair of morphisms 308:{\displaystyle X_{1}\times X_{2},} 14: 5714: 5005: 4385: 3069:{\displaystyle f_{i}:Y\to X_{i},} 2461:{\displaystyle X_{1}\times X_{2}} 1441:{\displaystyle f_{i}:Y\to X_{i},} 598:Universal property of the product 527:{\displaystyle f_{2}:Y\to X_{2},} 479:{\displaystyle f_{1}:Y\to X_{1},} 5676: 5666: 5657: 5656: 5409: 5076: 4896:Abstract and Concrete Categories 3631: 3617: 2578: 2570: 2304: 2296: 2288: 2254: 2246: 2219: 2213: 2190: 1516:Universal product of the product 586:such that the following diagram 74:. Essentially, the product of a 4982:Handbook of categorical algebra 4811:Lambek J., Scott P. J. (1988). 2931: 2869:with the canonical projections 1448:there exists a unique morphism 683:If it does exist, it is unique 534:there exists a unique morphism 4838: 4826:Qiaochu Yuan (June 23, 2012). 4804: 4719: 4707: 4701: 4689: 4683: 4671: 4641: 4629: 4620: 4579: 4567: 4486: 4474: 4465: 4248: 4236: 4230: 4218: 4024: 3968: 3894:Cartesian product of morphisms 3774: 3721: 3682: 3627: 3523: 3315:, the product is given by the 3304:, the product is given by the 3297:of the category of relations.) 3289:, the product is given by the 3222:. The product topology is the 3216:category of topological spaces 3175: 3169: 3147: 3141: 3092: 3050: 2915: 2657: 2654: 2642: 2412: 2400: 2360: 2348: 2292: 2101:. This may be seen by using a 1980: 1464: 1422: 1329: 1201:Product of an arbitrary family 772: 550: 508: 460: 386: 338: 82:to each of the given objects. 1: 4957:Graduate Texts in Mathematics 4797: 4585:{\displaystyle X\times (Y+Z)} 4179:denotes a terminal object of 3361: 2092: 1860:{\displaystyle i\in \{1,2\},} 1399:-indexed family of morphisms 85: 4879:. p. 62. Archived from 4766: – Mathematical concept 3416:{\displaystyle \mathbb {Q} } 2703:which contains projections. 2197:{\displaystyle \mathbf {J} } 2180:universal property of limits 437:and every pair of morphisms 7: 5351:Constructions on categories 4737: 4380:symmetric monoidal category 3027:with a family of functions 2706: 1819:{\displaystyle f_{1},f_{2}} 1286:of the family is an object 10: 5719: 5458:Higher-dimensional algebra 4962:(2nd ed.). Springer. 4389: 3991:we should find a morphism 3744:we should find a morphism 3353:) and least upper bounds ( 3330:, the product carries the 2742:the product is defined as 18: 5652: 5585: 5549: 5497: 5490: 5441: 5431: 5418: 5407: 5350: 5292: 5243: 5198: 5189: 5086: 5082: 5071: 4978:Borceux, Francis (1994). 4902:. John Wiley & Sons. 4782:Cartesian closed category 2155:{\displaystyle \{f\}_{i}} 409:satisfying the following 5703:Limits (category theory) 3280:tensor product of graphs 3269:direct product of groups 1473:{\displaystyle f:Y\to X} 1306:equipped with morphisms 956:{\displaystyle \pi _{2}} 929:{\displaystyle \pi _{1}} 19:Not to be confused with 5268:Cokernels and quotients 5191:Universal constructions 4760:of the product functor. 2505:{\displaystyle \Delta } 2318:assigns to each object 1524:The product is denoted 1502:{\displaystyle i\in I:} 5425:Higher category theory 5171:Natural transformation 4729: 4648: 4586: 4551: 4538: 4496: 4427: 4368: 4328: 4282: 4196: 4173: 4153: 4120: 4060: 3985: 3886: 3807: 3738: 3642: 3599: 3579: 3556: 3536: 3505: 3473: 3447: 3446:{\displaystyle F_{p}.} 3417: 3395: 3254: 3202: 3125: 3070: 3021: 3001: 2863: 2736: 2697: 2629: 2609: 2589: 2556: 2506: 2482: 2462: 2422: 2421:{\displaystyle (f,f).} 2387: 2367: 2332: 2312: 2265: 2229: 2198: 2176:universal construction 2156: 2123: 2083: 2013: 1958: 1936: 1861: 1820: 1778: 1743: 1712: 1657: 1611: 1564: 1517: 1503: 1474: 1442: 1393: 1373: 1349: 1300: 1276: 1226: 1192: 1143: 1116: 1086: 1066: 1065:{\displaystyle f_{2},} 1037: 1036:{\displaystyle f_{1},} 1007: 987: 957: 930: 900: 851: 802: 745: 677: 676:{\displaystyle X_{2}.} 647: 620: 599: 580: 528: 480: 431: 403: 358: 309: 266: 243: 216: 189: 166: 139: 112: 91:Product of two objects 5012:Interactive Web page 4845:Lane, S. Mac (1988). 4730: 4656:distributive category 4649: 4587: 4550: 4539: 4497: 4428: 4392:Distributive category 4369: 4329: 4283: 4197: 4174: 4154: 4121: 4061: 3986: 3887: 3808: 3739: 3643: 3600: 3580: 3557: 3537: 3506: 3474: 3448: 3418: 3396: 3343:partially ordered set 3287:category of relations 3278:, the product is the 3267:, the product is the 3255: 3203: 3126: 3071: 3022: 3002: 2864: 2737: 2735:{\displaystyle X_{i}} 2698: 2630: 2610: 2590: 2557: 2507: 2483: 2463: 2423: 2388: 2373:and to each morphism 2368: 2366:{\displaystyle (X,X)} 2333: 2313: 2266: 2230: 2199: 2157: 2124: 2084: 2014: 1959: 1937: 1862: 1821: 1779: 1744: 1721:Equational definition 1713: 1658: 1612: 1565: 1515: 1504: 1475: 1443: 1394: 1374: 1350: 1301: 1277: 1227: 1193: 1144: 1142:{\displaystyle f_{2}} 1117: 1115:{\displaystyle f_{1}} 1087: 1067: 1038: 1008: 988: 966:canonical projections 958: 931: 901: 852: 803: 746: 688:canonical isomorphism 678: 648: 646:{\displaystyle X_{1}} 621: 597: 581: 529: 481: 432: 404: 359: 310: 267: 244: 242:{\displaystyle X_{2}} 217: 215:{\displaystyle X_{1}} 190: 167: 165:{\displaystyle X_{2}} 140: 138:{\displaystyle X_{1}} 113: 5294:Algebraic categories 4976:Definition 2.1.1 in 4788:Categorical pullback 4662: 4596: 4558: 4510: 4441: 4400: 4337: 4291: 4209: 4204:natural isomorphisms 4183: 4163: 4143: 4070: 3995: 3900: 3817: 3748: 3656: 3612: 3589: 3569: 3562:cannot be terminal. 3546: 3515: 3495: 3463: 3455:Another example: An 3427: 3405: 3370: 3313:semi-abelian monoids 3241: 3135: 3080: 3076:the universal arrow 3031: 3011: 2873: 2746: 2719: 2639: 2619: 2599: 2566: 2516: 2496: 2472: 2432: 2397: 2377: 2345: 2322: 2278: 2242: 2208: 2186: 2133: 2113: 2022: 1968: 1948: 1870: 1830: 1790: 1753: 1733: 1667: 1621: 1574: 1528: 1484: 1452: 1403: 1383: 1363: 1310: 1290: 1238: 1213: 1153: 1126: 1099: 1094:product of morphisms 1076: 1072:the unique morphism 1046: 1017: 997: 986:{\displaystyle \pi } 977: 971:projection morphisms 940: 913: 861: 812: 755: 698: 657: 630: 610: 538: 489: 441: 421: 367: 319: 276: 253: 226: 199: 176: 149: 122: 99: 5463:Homotopy hypothesis 5141:Commutative diagram 3483:) is the same as a 3322:In the category of 3311:In the category of 3302:algebraic varieties 3300:In the category of 3235:category of modules 2842: for all  1617:then it is denoted 876: 827: 740: 724: 5176:Universal property 4947:Mac Lane, Saunders 4832:Annoying Precision 4764:Limit and colimits 4725: 4644: 4582: 4552: 4534: 4492: 4423: 4364: 4324: 4278: 4195:{\displaystyle C.} 4192: 4169: 4149: 4130:Cartesian category 4116: 4056: 4042: 4013: 3981: 3882: 3803: 3734: 3638: 3595: 3575: 3552: 3532: 3501: 3469: 3443: 3413: 3391: 3276:category of graphs 3265:category of groups 3253:{\displaystyle R,} 3250: 3198: 3121: 3110: 3066: 3017: 2997: 2904: 2859: 2764: 2732: 2693: 2625: 2605: 2585: 2552: 2502: 2490:universal morphism 2478: 2458: 2418: 2383: 2363: 2328: 2308: 2261: 2225: 2194: 2170:Universal property 2152: 2119: 2079: 2009: 1954: 1932: 1857: 1816: 1774: 1739: 1708: 1653: 1607: 1560: 1546: 1518: 1499: 1470: 1438: 1389: 1369: 1345: 1296: 1272: 1225:{\displaystyle I.} 1222: 1188: 1139: 1112: 1082: 1062: 1033: 1003: 983: 953: 926: 896: 864: 847: 815: 798: 741: 728: 712: 673: 643: 616: 600: 576: 524: 476: 427: 411:universal property 399: 354: 305: 272:typically denoted 265:{\displaystyle X,} 262: 239: 212: 188:{\displaystyle C.} 185: 162: 135: 111:{\displaystyle C.} 108: 72:topological spaces 5690: 5689: 5648: 5647: 5644: 5643: 5626:monoidal category 5581: 5580: 5453:Enriched category 5405: 5404: 5401: 5400: 5378:Quotient category 5373:Opposite category 5288: 5287: 4418: 4172:{\displaystyle 1} 4152:{\displaystyle C} 4027: 3998: 3598:{\displaystyle I} 3578:{\displaystyle I} 3555:{\displaystyle G} 3504:{\displaystyle G} 3472:{\displaystyle I} 3224:coarsest topology 3095: 3020:{\displaystyle Y} 2889: 2843: 2749: 2628:{\displaystyle C} 2608:{\displaystyle X} 2492:from the functor 2481:{\displaystyle C} 2386:{\displaystyle f} 2331:{\displaystyle X} 2122:{\displaystyle I} 2103:discrete category 1957:{\displaystyle f} 1742:{\displaystyle f} 1531: 1392:{\displaystyle I} 1372:{\displaystyle Y} 1359:For every object 1299:{\displaystyle X} 1085:{\displaystyle f} 1006:{\displaystyle Y} 619:{\displaystyle C} 430:{\displaystyle Y} 417:For every object 48:Cartesian product 34:of two (or more) 5710: 5680: 5679: 5670: 5669: 5660: 5659: 5495: 5494: 5473:Simplex category 5448:Categorification 5439: 5438: 5420: 5419: 5413: 5383:Product category 5368:Kleisli category 5363:Functor category 5208:Terminal objects 5196: 5195: 5131:Adjoint functors 5084: 5083: 5073: 5072: 5058: 5051: 5044: 5035: 5034: 5001: 4985: 4973: 4941: 4939: 4938: 4932: 4925: 4913: 4901: 4885: 4884: 4870: 4861: 4860: 4842: 4836: 4835: 4823: 4817: 4816: 4808: 4793: 4754:Diagonal functor 4734: 4732: 4731: 4726: 4653: 4651: 4650: 4645: 4591: 4589: 4588: 4583: 4543: 4541: 4540: 4535: 4501: 4499: 4498: 4493: 4432: 4430: 4429: 4424: 4419: 4416: 4396:For any objects 4373: 4371: 4370: 4365: 4333: 4331: 4330: 4325: 4287: 4285: 4284: 4279: 4201: 4199: 4198: 4193: 4178: 4176: 4175: 4170: 4158: 4156: 4155: 4150: 4125: 4123: 4122: 4117: 4112: 4111: 4106: 4102: 4101: 4100: 4088: 4087: 4065: 4063: 4062: 4057: 4052: 4051: 4041: 4023: 4022: 4012: 3990: 3988: 3987: 3982: 3980: 3979: 3967: 3966: 3954: 3953: 3941: 3940: 3935: 3920: 3919: 3914: 3891: 3889: 3888: 3883: 3878: 3874: 3873: 3872: 3860: 3859: 3847: 3846: 3834: 3833: 3812: 3810: 3809: 3804: 3799: 3798: 3786: 3785: 3773: 3772: 3760: 3759: 3743: 3741: 3740: 3735: 3733: 3732: 3720: 3719: 3707: 3706: 3694: 3693: 3681: 3680: 3668: 3667: 3647: 3645: 3644: 3639: 3634: 3626: 3625: 3620: 3604: 3602: 3601: 3596: 3584: 3582: 3581: 3576: 3561: 3559: 3558: 3553: 3541: 3539: 3538: 3533: 3522: 3510: 3508: 3507: 3502: 3478: 3476: 3475: 3470: 3452: 3450: 3449: 3444: 3439: 3438: 3422: 3420: 3419: 3414: 3412: 3400: 3398: 3397: 3392: 3390: 3389: 3377: 3336: 3259: 3257: 3256: 3251: 3220:product topology 3210:Other examples: 3207: 3205: 3204: 3199: 3194: 3193: 3182: 3178: 3168: 3167: 3130: 3128: 3127: 3122: 3120: 3119: 3109: 3075: 3073: 3072: 3067: 3062: 3061: 3043: 3042: 3026: 3024: 3023: 3018: 3006: 3004: 3003: 2998: 2993: 2992: 2980: 2976: 2975: 2964: 2960: 2959: 2941: 2940: 2927: 2926: 2914: 2913: 2903: 2885: 2884: 2868: 2866: 2865: 2860: 2858: 2854: 2844: 2841: 2839: 2838: 2826: 2825: 2813: 2812: 2801: 2797: 2796: 2774: 2773: 2763: 2741: 2739: 2738: 2733: 2731: 2730: 2713:category of sets 2702: 2700: 2699: 2694: 2692: 2688: 2687: 2686: 2674: 2673: 2634: 2632: 2631: 2626: 2614: 2612: 2611: 2606: 2594: 2592: 2591: 2586: 2581: 2573: 2561: 2559: 2558: 2553: 2551: 2547: 2546: 2545: 2533: 2532: 2511: 2509: 2508: 2503: 2487: 2485: 2484: 2479: 2467: 2465: 2464: 2459: 2457: 2456: 2444: 2443: 2427: 2425: 2424: 2419: 2392: 2390: 2389: 2384: 2372: 2370: 2369: 2364: 2337: 2335: 2334: 2329: 2317: 2315: 2314: 2309: 2307: 2299: 2291: 2273:diagonal functor 2270: 2268: 2267: 2262: 2257: 2249: 2237:product category 2234: 2232: 2231: 2226: 2224: 2223: 2222: 2216: 2203: 2201: 2200: 2195: 2193: 2161: 2159: 2158: 2153: 2151: 2150: 2128: 2126: 2125: 2120: 2088: 2086: 2085: 2080: 2069: 2065: 2058: 2057: 2039: 2038: 2018: 2016: 2015: 2010: 2005: 2004: 1992: 1991: 1963: 1961: 1960: 1955: 1941: 1939: 1938: 1933: 1931: 1930: 1918: 1914: 1913: 1912: 1900: 1899: 1882: 1881: 1866: 1864: 1863: 1858: 1825: 1823: 1822: 1817: 1815: 1814: 1802: 1801: 1783: 1781: 1780: 1775: 1748: 1746: 1745: 1740: 1717: 1715: 1714: 1709: 1701: 1700: 1682: 1681: 1662: 1660: 1659: 1654: 1652: 1651: 1633: 1632: 1616: 1614: 1613: 1608: 1569: 1567: 1566: 1561: 1556: 1555: 1545: 1508: 1506: 1505: 1500: 1479: 1477: 1476: 1471: 1447: 1445: 1444: 1439: 1434: 1433: 1415: 1414: 1398: 1396: 1395: 1390: 1378: 1376: 1375: 1370: 1354: 1352: 1351: 1346: 1341: 1340: 1322: 1321: 1305: 1303: 1302: 1297: 1281: 1279: 1278: 1273: 1271: 1270: 1259: 1255: 1254: 1231: 1229: 1228: 1223: 1197: 1195: 1194: 1189: 1181: 1180: 1168: 1167: 1148: 1146: 1145: 1140: 1138: 1137: 1121: 1119: 1118: 1113: 1111: 1110: 1091: 1089: 1088: 1083: 1071: 1069: 1068: 1063: 1058: 1057: 1042: 1040: 1039: 1034: 1029: 1028: 1012: 1010: 1009: 1004: 992: 990: 989: 984: 962: 960: 959: 954: 952: 951: 935: 933: 932: 927: 925: 924: 905: 903: 902: 897: 889: 888: 872: 856: 854: 853: 848: 840: 839: 823: 807: 805: 804: 799: 797: 796: 784: 783: 771: 750: 748: 747: 742: 736: 720: 708: 682: 680: 679: 674: 669: 668: 652: 650: 649: 644: 642: 641: 625: 623: 622: 617: 585: 583: 582: 577: 575: 574: 562: 561: 533: 531: 530: 525: 520: 519: 501: 500: 485: 483: 482: 477: 472: 471: 453: 452: 436: 434: 433: 428: 408: 406: 405: 400: 398: 397: 379: 378: 363: 361: 360: 355: 350: 349: 331: 330: 314: 312: 311: 306: 301: 300: 288: 287: 271: 269: 268: 263: 248: 246: 245: 240: 238: 237: 221: 219: 218: 213: 211: 210: 194: 192: 191: 186: 171: 169: 168: 163: 161: 160: 144: 142: 141: 136: 134: 133: 117: 115: 114: 109: 21:Product category 5718: 5717: 5713: 5712: 5711: 5709: 5708: 5707: 5693: 5692: 5691: 5686: 5640: 5610: 5577: 5554: 5545: 5502: 5486: 5437: 5427: 5414: 5397: 5346: 5284: 5253:Initial objects 5239: 5185: 5078: 5067: 5065:Category theory 5062: 5008: 4998: 4970: 4936: 4934: 4930: 4923: 4910: 4899: 4889: 4888: 4871: 4864: 4857: 4843: 4839: 4824: 4820: 4809: 4805: 4800: 4791: 4740: 4663: 4660: 4659: 4597: 4594: 4593: 4559: 4556: 4555: 4511: 4508: 4507: 4442: 4439: 4438: 4417: and  4415: 4401: 4398: 4397: 4394: 4388: 4338: 4335: 4334: 4292: 4289: 4288: 4210: 4207: 4206: 4184: 4181: 4180: 4164: 4161: 4160: 4144: 4141: 4140: 4135:The product is 4107: 4096: 4092: 4083: 4079: 4078: 4074: 4073: 4071: 4068: 4067: 4047: 4043: 4031: 4018: 4014: 4002: 3996: 3993: 3992: 3975: 3971: 3962: 3958: 3949: 3945: 3936: 3925: 3924: 3915: 3904: 3903: 3901: 3898: 3897: 3868: 3864: 3855: 3851: 3842: 3838: 3829: 3825: 3824: 3820: 3818: 3815: 3814: 3794: 3790: 3781: 3777: 3768: 3764: 3755: 3751: 3749: 3746: 3745: 3728: 3724: 3715: 3711: 3702: 3698: 3689: 3685: 3676: 3672: 3663: 3659: 3657: 3654: 3653: 3630: 3621: 3616: 3615: 3613: 3610: 3609: 3590: 3587: 3586: 3570: 3567: 3566: 3547: 3544: 3543: 3518: 3516: 3513: 3512: 3496: 3493: 3492: 3489:infinite groups 3485:terminal object 3464: 3461: 3460: 3434: 3430: 3428: 3425: 3424: 3408: 3406: 3403: 3402: 3385: 3381: 3373: 3371: 3368: 3367: 3364: 3332: 3306:Segre embedding 3242: 3239: 3238: 3237:over some ring 3183: 3163: 3159: 3158: 3154: 3153: 3136: 3133: 3132: 3115: 3111: 3099: 3081: 3078: 3077: 3057: 3053: 3038: 3034: 3032: 3029: 3028: 3012: 3009: 3008: 2988: 2984: 2965: 2955: 2951: 2947: 2946: 2942: 2936: 2932: 2922: 2918: 2909: 2905: 2893: 2880: 2876: 2874: 2871: 2870: 2840: 2834: 2830: 2821: 2817: 2802: 2792: 2788: 2784: 2783: 2782: 2778: 2769: 2765: 2753: 2747: 2744: 2743: 2726: 2722: 2720: 2717: 2716: 2709: 2682: 2678: 2669: 2665: 2664: 2660: 2640: 2637: 2636: 2635:and a morphism 2620: 2617: 2616: 2600: 2597: 2596: 2577: 2569: 2567: 2564: 2563: 2541: 2537: 2528: 2524: 2523: 2519: 2517: 2514: 2513: 2497: 2494: 2493: 2473: 2470: 2469: 2452: 2448: 2439: 2435: 2433: 2430: 2429: 2398: 2395: 2394: 2378: 2375: 2374: 2346: 2343: 2342: 2323: 2320: 2319: 2303: 2295: 2287: 2279: 2276: 2275: 2253: 2245: 2243: 2240: 2239: 2218: 2217: 2212: 2211: 2209: 2206: 2205: 2189: 2187: 2184: 2183: 2172: 2146: 2142: 2134: 2131: 2130: 2114: 2111: 2110: 2095: 2053: 2049: 2034: 2030: 2029: 2025: 2023: 2020: 2019: 2000: 1996: 1987: 1983: 1969: 1966: 1965: 1949: 1946: 1945: 1926: 1922: 1908: 1904: 1895: 1891: 1890: 1886: 1877: 1873: 1871: 1868: 1867: 1831: 1828: 1827: 1810: 1806: 1797: 1793: 1791: 1788: 1787: 1754: 1751: 1750: 1734: 1731: 1730: 1723: 1696: 1692: 1677: 1673: 1668: 1665: 1664: 1647: 1643: 1628: 1624: 1622: 1619: 1618: 1575: 1572: 1571: 1551: 1547: 1535: 1529: 1526: 1525: 1485: 1482: 1481: 1453: 1450: 1449: 1429: 1425: 1410: 1406: 1404: 1401: 1400: 1384: 1381: 1380: 1364: 1361: 1360: 1336: 1332: 1317: 1313: 1311: 1308: 1307: 1291: 1288: 1287: 1260: 1250: 1246: 1242: 1241: 1239: 1236: 1235: 1234:Given a family 1214: 1211: 1210: 1203: 1176: 1172: 1163: 1159: 1154: 1151: 1150: 1149:and is denoted 1133: 1129: 1127: 1124: 1123: 1106: 1102: 1100: 1097: 1096: 1077: 1074: 1073: 1053: 1049: 1047: 1044: 1043: 1024: 1020: 1018: 1015: 1014: 998: 995: 994: 978: 975: 974: 963:are called the 947: 943: 941: 938: 937: 920: 916: 914: 911: 910: 884: 880: 868: 862: 859: 858: 835: 831: 819: 813: 810: 809: 792: 788: 779: 775: 764: 756: 753: 752: 732: 716: 701: 699: 696: 695: 664: 660: 658: 655: 654: 637: 633: 631: 628: 627: 611: 608: 607: 570: 566: 557: 553: 539: 536: 535: 515: 511: 496: 492: 490: 487: 486: 467: 463: 448: 444: 442: 439: 438: 422: 419: 418: 393: 389: 374: 370: 368: 365: 364: 345: 341: 326: 322: 320: 317: 316: 296: 292: 283: 279: 277: 274: 273: 254: 251: 250: 233: 229: 227: 224: 223: 206: 202: 200: 197: 196: 177: 174: 173: 156: 152: 150: 147: 146: 129: 125: 123: 120: 119: 100: 97: 96: 95:Fix a category 93: 88: 28:category theory 24: 17: 12: 11: 5: 5716: 5706: 5705: 5688: 5687: 5685: 5684: 5674: 5664: 5653: 5650: 5649: 5646: 5645: 5642: 5641: 5639: 5638: 5633: 5628: 5614: 5608: 5603: 5598: 5592: 5590: 5583: 5582: 5579: 5578: 5576: 5575: 5570: 5559: 5557: 5552: 5547: 5546: 5544: 5543: 5538: 5533: 5528: 5523: 5518: 5507: 5505: 5500: 5492: 5488: 5487: 5485: 5480: 5478:String diagram 5475: 5470: 5468:Model category 5465: 5460: 5455: 5450: 5445: 5443: 5436: 5435: 5432: 5429: 5428: 5416: 5415: 5408: 5406: 5403: 5402: 5399: 5398: 5396: 5395: 5390: 5388:Comma category 5385: 5380: 5375: 5370: 5365: 5360: 5354: 5352: 5348: 5347: 5345: 5344: 5334: 5324: 5322:Abelian groups 5319: 5314: 5309: 5304: 5298: 5296: 5290: 5289: 5286: 5285: 5283: 5282: 5277: 5272: 5271: 5270: 5260: 5255: 5249: 5247: 5241: 5240: 5238: 5237: 5232: 5227: 5226: 5225: 5215: 5210: 5204: 5202: 5193: 5187: 5186: 5184: 5183: 5178: 5173: 5168: 5163: 5158: 5153: 5148: 5143: 5138: 5133: 5128: 5127: 5126: 5121: 5116: 5111: 5106: 5101: 5090: 5088: 5080: 5079: 5069: 5068: 5061: 5060: 5053: 5046: 5038: 5032: 5031: 5019: 5007: 5006:External links 5004: 5003: 5002: 4996: 4974: 4968: 4943: 4914: 4908: 4887: 4886: 4883:on 2011-04-13. 4862: 4855: 4837: 4818: 4802: 4801: 4799: 4796: 4795: 4794: 4785: 4779: 4773: 4767: 4761: 4751: 4750:of the product 4739: 4736: 4724: 4721: 4718: 4715: 4712: 4709: 4706: 4703: 4700: 4697: 4694: 4691: 4688: 4685: 4682: 4679: 4676: 4673: 4670: 4667: 4643: 4640: 4637: 4634: 4631: 4628: 4625: 4622: 4619: 4616: 4613: 4610: 4607: 4604: 4601: 4581: 4578: 4575: 4572: 4569: 4566: 4563: 4533: 4530: 4527: 4524: 4521: 4518: 4515: 4491: 4488: 4485: 4482: 4479: 4476: 4473: 4470: 4467: 4464: 4461: 4458: 4455: 4452: 4449: 4446: 4422: 4414: 4411: 4408: 4405: 4390:Main article: 4387: 4386:Distributivity 4384: 4363: 4360: 4357: 4354: 4351: 4348: 4345: 4342: 4323: 4320: 4317: 4314: 4311: 4308: 4305: 4302: 4299: 4296: 4277: 4274: 4271: 4268: 4265: 4262: 4259: 4256: 4253: 4250: 4247: 4244: 4241: 4238: 4235: 4232: 4229: 4226: 4223: 4220: 4217: 4214: 4191: 4188: 4168: 4148: 4115: 4110: 4105: 4099: 4095: 4091: 4086: 4082: 4077: 4055: 4050: 4046: 4040: 4037: 4034: 4030: 4026: 4021: 4017: 4011: 4008: 4005: 4001: 3978: 3974: 3970: 3965: 3961: 3957: 3952: 3948: 3944: 3939: 3934: 3931: 3928: 3923: 3918: 3913: 3910: 3907: 3881: 3877: 3871: 3867: 3863: 3858: 3854: 3850: 3845: 3841: 3837: 3832: 3828: 3823: 3802: 3797: 3793: 3789: 3784: 3780: 3776: 3771: 3767: 3763: 3758: 3754: 3731: 3727: 3723: 3718: 3714: 3710: 3705: 3701: 3697: 3692: 3688: 3684: 3679: 3675: 3671: 3666: 3662: 3637: 3633: 3629: 3624: 3619: 3594: 3574: 3551: 3531: 3528: 3525: 3521: 3500: 3468: 3442: 3437: 3433: 3411: 3388: 3384: 3380: 3376: 3363: 3360: 3359: 3358: 3339: 3320: 3317:history monoid 3309: 3298: 3291:disjoint union 3283: 3272: 3261: 3249: 3246: 3231: 3197: 3192: 3189: 3186: 3181: 3177: 3174: 3171: 3166: 3162: 3157: 3152: 3149: 3146: 3143: 3140: 3131:is defined by 3118: 3114: 3108: 3105: 3102: 3098: 3094: 3091: 3088: 3085: 3065: 3060: 3056: 3052: 3049: 3046: 3041: 3037: 3016: 3007:Given any set 2996: 2991: 2987: 2983: 2979: 2974: 2971: 2968: 2963: 2958: 2954: 2950: 2945: 2939: 2935: 2930: 2925: 2921: 2917: 2912: 2908: 2902: 2899: 2896: 2892: 2888: 2883: 2879: 2857: 2853: 2850: 2847: 2837: 2833: 2829: 2824: 2820: 2816: 2811: 2808: 2805: 2800: 2795: 2791: 2787: 2781: 2777: 2772: 2768: 2762: 2759: 2756: 2752: 2729: 2725: 2708: 2705: 2691: 2685: 2681: 2677: 2672: 2668: 2663: 2659: 2656: 2653: 2650: 2647: 2644: 2624: 2604: 2584: 2580: 2576: 2572: 2550: 2544: 2540: 2536: 2531: 2527: 2522: 2512:to the object 2501: 2488:is given by a 2477: 2455: 2451: 2447: 2442: 2438: 2417: 2414: 2411: 2408: 2405: 2402: 2382: 2362: 2359: 2356: 2353: 2350: 2327: 2306: 2302: 2298: 2294: 2290: 2286: 2283: 2260: 2256: 2252: 2248: 2235:is simply the 2221: 2215: 2192: 2171: 2168: 2149: 2145: 2141: 2138: 2118: 2094: 2091: 2090: 2089: 2078: 2075: 2072: 2068: 2064: 2061: 2056: 2052: 2048: 2045: 2042: 2037: 2033: 2028: 2008: 2003: 1999: 1995: 1990: 1986: 1982: 1979: 1976: 1973: 1953: 1944:Uniqueness of 1942: 1929: 1925: 1921: 1917: 1911: 1907: 1903: 1898: 1894: 1889: 1885: 1880: 1876: 1856: 1853: 1850: 1847: 1844: 1841: 1838: 1835: 1813: 1809: 1805: 1800: 1796: 1784: 1773: 1770: 1767: 1764: 1761: 1758: 1738: 1722: 1719: 1707: 1704: 1699: 1695: 1691: 1688: 1685: 1680: 1676: 1672: 1650: 1646: 1642: 1639: 1636: 1631: 1627: 1606: 1603: 1600: 1597: 1594: 1591: 1588: 1585: 1582: 1579: 1559: 1554: 1550: 1544: 1541: 1538: 1534: 1522: 1521: 1520: 1519: 1498: 1495: 1492: 1489: 1469: 1466: 1463: 1460: 1457: 1437: 1432: 1428: 1424: 1421: 1418: 1413: 1409: 1388: 1368: 1344: 1339: 1335: 1331: 1328: 1325: 1320: 1316: 1295: 1282:of objects, a 1269: 1266: 1263: 1258: 1253: 1249: 1245: 1221: 1218: 1202: 1199: 1187: 1184: 1179: 1175: 1171: 1166: 1162: 1158: 1136: 1132: 1109: 1105: 1092:is called the 1081: 1061: 1056: 1052: 1032: 1027: 1023: 1002: 982: 950: 946: 923: 919: 909:The morphisms 895: 892: 887: 883: 879: 875: 871: 867: 846: 843: 838: 834: 830: 826: 822: 818: 795: 791: 787: 782: 778: 774: 770: 767: 763: 760: 739: 735: 731: 727: 723: 719: 715: 711: 707: 704: 672: 667: 663: 640: 636: 615: 604: 603: 602: 601: 573: 569: 565: 560: 556: 552: 549: 546: 543: 523: 518: 514: 510: 507: 504: 499: 495: 475: 470: 466: 462: 459: 456: 451: 447: 426: 396: 392: 388: 385: 382: 377: 373: 353: 348: 344: 340: 337: 334: 329: 325: 304: 299: 295: 291: 286: 282: 261: 258: 236: 232: 209: 205: 184: 181: 172:be objects of 159: 155: 132: 128: 107: 104: 92: 89: 87: 84: 56:direct product 15: 9: 6: 4: 3: 2: 5715: 5704: 5701: 5700: 5698: 5683: 5675: 5673: 5665: 5663: 5655: 5654: 5651: 5637: 5634: 5632: 5629: 5627: 5623: 5619: 5615: 5613: 5611: 5604: 5602: 5599: 5597: 5594: 5593: 5591: 5588: 5584: 5574: 5571: 5568: 5564: 5561: 5560: 5558: 5556: 5548: 5542: 5539: 5537: 5534: 5532: 5529: 5527: 5526:Tetracategory 5524: 5522: 5519: 5516: 5515:pseudofunctor 5512: 5509: 5508: 5506: 5504: 5496: 5493: 5489: 5484: 5481: 5479: 5476: 5474: 5471: 5469: 5466: 5464: 5461: 5459: 5456: 5454: 5451: 5449: 5446: 5444: 5440: 5434: 5433: 5430: 5426: 5421: 5417: 5412: 5394: 5391: 5389: 5386: 5384: 5381: 5379: 5376: 5374: 5371: 5369: 5366: 5364: 5361: 5359: 5358:Free category 5356: 5355: 5353: 5349: 5342: 5341:Vector spaces 5338: 5335: 5332: 5328: 5325: 5323: 5320: 5318: 5315: 5313: 5310: 5308: 5305: 5303: 5300: 5299: 5297: 5295: 5291: 5281: 5278: 5276: 5273: 5269: 5266: 5265: 5264: 5261: 5259: 5256: 5254: 5251: 5250: 5248: 5246: 5242: 5236: 5235:Inverse limit 5233: 5231: 5228: 5224: 5221: 5220: 5219: 5216: 5214: 5211: 5209: 5206: 5205: 5203: 5201: 5197: 5194: 5192: 5188: 5182: 5179: 5177: 5174: 5172: 5169: 5167: 5164: 5162: 5161:Kan extension 5159: 5157: 5154: 5152: 5149: 5147: 5144: 5142: 5139: 5137: 5134: 5132: 5129: 5125: 5122: 5120: 5117: 5115: 5112: 5110: 5107: 5105: 5102: 5100: 5097: 5096: 5095: 5092: 5091: 5089: 5085: 5081: 5074: 5070: 5066: 5059: 5054: 5052: 5047: 5045: 5040: 5039: 5036: 5030: 5028: 5023: 5020: 5017: 5016:Jocelyn Paine 5013: 5010: 5009: 4999: 4997:0-521-44178-1 4993: 4989: 4984: 4983: 4975: 4971: 4969:0-387-98403-8 4965: 4961: 4958: 4954: 4953: 4948: 4944: 4933:on 2016-03-04 4929: 4922: 4921: 4915: 4911: 4909:0-471-60922-6 4905: 4898: 4897: 4891: 4890: 4882: 4878: 4877: 4869: 4867: 4858: 4856:0-387-90035-7 4852: 4848: 4841: 4833: 4829: 4822: 4814: 4807: 4803: 4789: 4786: 4783: 4780: 4777: 4776:Inverse limit 4774: 4771: 4768: 4765: 4762: 4759: 4755: 4752: 4749: 4745: 4742: 4741: 4735: 4722: 4716: 4713: 4710: 4704: 4698: 4695: 4692: 4686: 4680: 4677: 4674: 4668: 4665: 4657: 4638: 4635: 4632: 4626: 4623: 4617: 4614: 4611: 4608: 4605: 4602: 4599: 4576: 4573: 4570: 4564: 4561: 4549: 4545: 4531: 4528: 4525: 4522: 4519: 4516: 4513: 4505: 4489: 4483: 4480: 4477: 4471: 4468: 4462: 4459: 4456: 4453: 4450: 4447: 4444: 4436: 4420: 4412: 4409: 4406: 4403: 4393: 4383: 4381: 4377: 4361: 4358: 4355: 4352: 4349: 4346: 4343: 4340: 4321: 4318: 4315: 4312: 4309: 4306: 4303: 4300: 4297: 4294: 4275: 4272: 4269: 4266: 4263: 4260: 4257: 4254: 4251: 4245: 4242: 4239: 4233: 4227: 4224: 4221: 4215: 4212: 4205: 4202:We then have 4189: 4186: 4166: 4146: 4138: 4133: 4131: 4126: 4113: 4108: 4103: 4097: 4093: 4089: 4084: 4080: 4075: 4053: 4048: 4044: 4038: 4035: 4032: 4028: 4019: 4015: 4009: 4006: 4003: 3999: 3976: 3972: 3963: 3959: 3955: 3950: 3946: 3942: 3937: 3932: 3929: 3926: 3921: 3916: 3911: 3908: 3905: 3895: 3879: 3875: 3869: 3865: 3861: 3856: 3852: 3848: 3843: 3839: 3835: 3830: 3826: 3821: 3800: 3795: 3791: 3787: 3782: 3778: 3769: 3765: 3761: 3756: 3752: 3729: 3725: 3716: 3712: 3708: 3703: 3699: 3695: 3690: 3686: 3677: 3673: 3669: 3664: 3660: 3651: 3635: 3622: 3608: 3592: 3572: 3563: 3549: 3529: 3526: 3498: 3490: 3486: 3482: 3466: 3458: 3457:empty product 3453: 3440: 3435: 3431: 3386: 3382: 3378: 3356: 3352: 3348: 3344: 3340: 3337: 3335: 3329: 3325: 3324:Banach spaces 3321: 3318: 3314: 3310: 3307: 3303: 3299: 3296: 3292: 3288: 3284: 3281: 3277: 3273: 3270: 3266: 3262: 3247: 3244: 3236: 3232: 3229: 3225: 3221: 3217: 3213: 3212: 3211: 3208: 3195: 3190: 3187: 3184: 3179: 3172: 3164: 3160: 3155: 3150: 3144: 3138: 3116: 3112: 3106: 3103: 3100: 3096: 3089: 3086: 3083: 3063: 3058: 3054: 3047: 3044: 3039: 3035: 3014: 2994: 2989: 2985: 2981: 2977: 2972: 2969: 2966: 2961: 2956: 2952: 2948: 2943: 2937: 2933: 2928: 2923: 2919: 2910: 2906: 2900: 2897: 2894: 2890: 2886: 2881: 2877: 2855: 2851: 2848: 2845: 2835: 2831: 2827: 2822: 2818: 2814: 2809: 2806: 2803: 2798: 2793: 2789: 2785: 2779: 2775: 2770: 2766: 2760: 2757: 2754: 2750: 2727: 2723: 2714: 2704: 2689: 2683: 2679: 2675: 2670: 2666: 2661: 2651: 2648: 2645: 2622: 2602: 2582: 2574: 2548: 2542: 2538: 2534: 2529: 2525: 2520: 2491: 2475: 2453: 2449: 2445: 2440: 2436: 2415: 2409: 2406: 2403: 2380: 2357: 2354: 2351: 2341: 2325: 2300: 2284: 2274: 2258: 2250: 2238: 2181: 2177: 2167: 2165: 2147: 2139: 2116: 2108: 2104: 2100: 2076: 2073: 2070: 2066: 2062: 2059: 2054: 2050: 2046: 2043: 2040: 2035: 2031: 2026: 2006: 2001: 1997: 1993: 1988: 1984: 1977: 1974: 1971: 1951: 1943: 1927: 1923: 1919: 1915: 1909: 1905: 1901: 1896: 1892: 1887: 1883: 1878: 1874: 1854: 1848: 1845: 1842: 1836: 1833: 1811: 1807: 1803: 1798: 1794: 1785: 1771: 1765: 1762: 1759: 1736: 1729:Existence of 1728: 1727: 1726: 1718: 1705: 1697: 1693: 1689: 1686: 1683: 1678: 1674: 1648: 1644: 1640: 1637: 1634: 1629: 1625: 1604: 1598: 1595: 1592: 1589: 1586: 1580: 1577: 1557: 1552: 1548: 1542: 1539: 1536: 1532: 1514: 1510: 1509: 1496: 1493: 1490: 1487: 1467: 1461: 1458: 1455: 1435: 1430: 1426: 1419: 1416: 1411: 1407: 1386: 1366: 1358: 1357: 1356: 1342: 1337: 1333: 1326: 1323: 1318: 1314: 1293: 1285: 1267: 1264: 1261: 1256: 1251: 1247: 1243: 1232: 1219: 1216: 1208: 1198: 1185: 1177: 1173: 1169: 1164: 1160: 1134: 1130: 1107: 1103: 1095: 1079: 1059: 1054: 1050: 1030: 1025: 1021: 1000: 980: 973:; the letter 972: 968: 967: 948: 944: 921: 917: 907: 893: 890: 885: 881: 877: 873: 869: 865: 844: 841: 836: 832: 828: 824: 820: 816: 793: 789: 785: 780: 776: 768: 765: 761: 758: 737: 733: 729: 725: 721: 717: 713: 709: 705: 702: 693: 689: 686: 670: 665: 661: 638: 634: 613: 596: 592: 591: 589: 571: 567: 563: 558: 554: 547: 544: 541: 521: 516: 512: 505: 502: 497: 493: 473: 468: 464: 457: 454: 449: 445: 424: 416: 415: 414: 412: 394: 390: 383: 380: 375: 371: 351: 346: 342: 335: 332: 327: 323: 302: 297: 293: 289: 284: 280: 259: 256: 249:is an object 234: 230: 207: 203: 195:A product of 182: 179: 157: 153: 130: 126: 105: 102: 83: 81: 77: 73: 69: 65: 61: 57: 53: 49: 45: 41: 37: 33: 29: 22: 5606: 5587:Categorified 5491:n-categories 5442:Key concepts 5280:Direct limit 5263:Coequalizers 5212: 5181:Yoneda lemma 5087:Key concepts 5077:Key concepts 5026: 4981: 4959: 4950: 4935:. Retrieved 4928:the original 4919: 4895: 4881:the original 4875: 4846: 4840: 4831: 4821: 4812: 4806: 4758:left adjoint 4756: – the 4746: – the 4553: 4395: 4134: 4129: 4127: 3893: 3564: 3454: 3365: 3333: 3209: 2710: 2428:The product 2340:ordered pair 2173: 2096: 1724: 1523: 1283: 1233: 1204: 1093: 970: 964: 908: 691: 605: 94: 46:such as the 31: 25: 5555:-categories 5531:Kan complex 5521:Tricategory 5503:-categories 5393:Subcategory 5151:Exponential 5119:Preadditive 5114:Pre-abelian 4137:associative 3295:subcategory 44:mathematics 5573:3-category 5563:2-category 5536:∞-groupoid 5511:Bicategory 5258:Coproducts 5218:Equalizers 5124:Bicategory 4942:Chapter 5. 4937:2016-03-21 4798:References 4139:. Suppose 3813:We choose 3459:(that is, 3362:Discussion 3347:coproducts 3328:short maps 3228:continuous 2093:As a limit 1379:and every 808:such that 86:Definition 66:, and the 5622:Symmetric 5567:2-functor 5307:Relations 5230:Pullbacks 4770:Equalizer 4744:Coproduct 4714:× 4696:× 4687:≃ 4669:× 4627:× 4621:→ 4615:× 4603:× 4565:× 4529:× 4517:× 4504:coproduct 4472:× 4466:→ 4460:× 4448:× 4437:morphism 4435:canonical 4356:× 4350:≃ 4344:× 4316:≃ 4310:× 4304:≃ 4298:× 4270:× 4264:× 4258:≃ 4252:× 4243:× 4234:≃ 4225:× 4216:× 4094:π 4090:∘ 4036:∈ 4029:∏ 4025:→ 4007:∈ 4000:∏ 3969:→ 3866:π 3862:∘ 3840:π 3836:∘ 3788:× 3775:→ 3762:× 3722:→ 3683:→ 3650:bifunctor 3628:→ 3524:→ 3481:empty set 3379:× 3188:∈ 3104:∈ 3097:∏ 3093:→ 3051:→ 2970:∈ 2934:π 2916:→ 2898:∈ 2891:∏ 2878:π 2849:∈ 2828:∈ 2807:∈ 2758:∈ 2751:∏ 2658:→ 2575:× 2500:Δ 2446:× 2393:the pair 2301:× 2293:→ 2282:Δ 2251:× 2060:∘ 2051:π 2041:∘ 2032:π 1994:× 1981:→ 1884:∘ 1875:π 1837:∈ 1769:⟩ 1766:⋅ 1760:⋅ 1757:⟨ 1703:⟩ 1687:… 1671:⟨ 1641:× 1638:⋯ 1635:× 1593:… 1540:∈ 1533:∏ 1491:∈ 1465:→ 1423:→ 1330:→ 1315:π 1265:∈ 1209:by a set 1183:⟩ 1157:⟨ 981:π 945:π 918:π 891:∘ 882:π 866:π 842:∘ 833:π 817:π 786:× 773:→ 730:π 714:π 564:× 551:→ 509:→ 461:→ 387:→ 372:π 339:→ 324:π 290:× 5697:Category 5682:Glossary 5662:Category 5636:n-monoid 5589:concepts 5245:Colimits 5213:Products 5166:Morphism 5109:Concrete 5104:Additive 5094:Category 4949:(1998). 4738:See also 3876:⟩ 3822:⟨ 2707:Examples 2162:being a 2067:⟩ 2027:⟨ 1916:⟩ 1888:⟨ 1826:and all 874:′ 825:′ 769:′ 738:′ 722:′ 706:′ 588:commutes 80:morphism 40:category 5672:Outline 5631:n-group 5596:2-group 5551:Strict 5541:∞-topos 5337:Modules 5275:Pushout 5223:Kernels 5156:Functor 5099:Abelian 5024:at the 5022:Product 3607:functor 3479:is the 3285:In the 3274:In the 3263:In the 3233:In the 3214:In the 2711:In the 2182:, take 2107:diagram 1284:product 1207:indexed 68:product 36:objects 32:product 5618:Traced 5601:2-ring 5331:Fields 5317:Groups 5312:Magmas 5200:Limits 4994:  4966:  4906:  4853:  4376:monoid 3652:. For 626:or on 76:family 60:groups 54:, the 30:, the 5612:-ring 5499:Weak 5483:Topos 5327:Rings 4931:(PDF) 4924:(PDF) 4900:(PDF) 3355:joins 3351:meets 3338:norm. 2099:limit 685:up to 64:rings 38:in a 5302:Sets 4992:ISBN 4964:ISBN 4904:ISBN 4851:ISBN 4748:dual 3423:and 3326:and 2338:the 2271:The 2164:cone 1122:and 1013:and 936:and 857:and 653:and 222:and 145:and 118:Let 52:sets 5146:End 5136:CCC 5029:Lab 3565:If 3542:so 2615:of 2562:in 2468:in 1570:If 969:or 692:the 70:of 62:or 58:of 50:of 26:In 5699:: 5624:) 5620:)( 4990:. 4988:39 4955:. 4865:^ 4830:. 4382:. 3357:). 3341:A 3151::= 2982::= 2776::= 906:. 590:: 413:: 5616:( 5609:n 5607:E 5569:) 5565:( 5553:n 5517:) 5513:( 5501:n 5343:) 5339:( 5333:) 5329:( 5057:e 5050:t 5043:v 5027:n 5018:. 5000:. 4972:. 4960:5 4940:. 4912:. 4859:. 4834:. 4723:. 4720:) 4717:Z 4711:X 4708:( 4705:+ 4702:) 4699:Y 4693:X 4690:( 4684:) 4681:Z 4678:+ 4675:Y 4672:( 4666:X 4642:) 4639:Z 4636:+ 4633:Y 4630:( 4624:X 4618:Z 4612:X 4609:+ 4606:Y 4600:X 4580:) 4577:Z 4574:+ 4571:Y 4568:( 4562:X 4532:Z 4526:X 4523:+ 4520:Y 4514:X 4490:, 4487:) 4484:Z 4481:+ 4478:Y 4475:( 4469:X 4463:Z 4457:X 4454:+ 4451:Y 4445:X 4421:Z 4413:, 4410:Y 4407:, 4404:X 4362:. 4359:X 4353:Y 4347:Y 4341:X 4322:, 4319:X 4313:X 4307:1 4301:1 4295:X 4276:, 4273:Z 4267:Y 4261:X 4255:Z 4249:) 4246:Y 4240:X 4237:( 4231:) 4228:Z 4222:Y 4219:( 4213:X 4190:. 4187:C 4167:1 4147:C 4114:. 4109:i 4104:} 4098:i 4085:i 4081:f 4076:{ 4054:. 4049:i 4045:Y 4039:I 4033:i 4020:i 4016:X 4010:I 4004:i 3977:i 3973:Y 3964:i 3960:X 3956:: 3951:i 3947:f 3943:, 3938:i 3933:} 3930:Y 3927:{ 3922:, 3917:i 3912:} 3909:X 3906:{ 3880:. 3870:2 3857:2 3853:f 3849:, 3844:1 3831:1 3827:f 3801:. 3796:2 3792:Y 3783:1 3779:Y 3770:2 3766:X 3757:1 3753:X 3730:2 3726:Y 3717:2 3713:X 3709:: 3704:2 3700:f 3696:, 3691:1 3687:Y 3678:1 3674:X 3670:: 3665:1 3661:f 3636:. 3632:C 3623:I 3618:C 3593:I 3573:I 3550:G 3530:, 3527:G 3520:Z 3499:G 3467:I 3441:. 3436:p 3432:F 3410:Q 3387:p 3383:F 3375:Q 3334:l 3319:. 3308:. 3282:. 3248:, 3245:R 3230:. 3196:. 3191:I 3185:i 3180:) 3176:) 3173:y 3170:( 3165:i 3161:f 3156:( 3148:) 3145:y 3142:( 3139:f 3117:i 3113:X 3107:I 3101:i 3090:Y 3087:: 3084:f 3064:, 3059:i 3055:X 3048:Y 3045:: 3040:i 3036:f 3015:Y 2995:. 2990:j 2986:x 2978:) 2973:I 2967:i 2962:) 2957:i 2953:x 2949:( 2944:( 2938:j 2929:, 2924:j 2920:X 2911:i 2907:X 2901:I 2895:i 2887:: 2882:j 2856:} 2852:I 2846:i 2836:i 2832:X 2823:i 2819:x 2815:: 2810:I 2804:i 2799:) 2794:i 2790:x 2786:( 2780:{ 2771:i 2767:X 2761:I 2755:i 2728:i 2724:X 2690:) 2684:2 2680:X 2676:, 2671:1 2667:X 2662:( 2655:) 2652:X 2649:, 2646:X 2643:( 2623:C 2603:X 2583:. 2579:C 2571:C 2549:) 2543:2 2539:X 2535:, 2530:1 2526:X 2521:( 2476:C 2454:2 2450:X 2441:1 2437:X 2416:. 2413:) 2410:f 2407:, 2404:f 2401:( 2381:f 2361:) 2358:X 2355:, 2352:X 2349:( 2326:X 2305:C 2297:C 2289:C 2285:: 2259:. 2255:C 2247:C 2220:J 2214:C 2191:J 2148:i 2144:} 2140:f 2137:{ 2117:I 2077:. 2074:g 2071:= 2063:g 2055:2 2047:, 2044:g 2036:1 2007:, 2002:2 1998:X 1989:1 1985:X 1978:Y 1975:: 1972:g 1952:f 1928:i 1924:f 1920:= 1910:2 1906:f 1902:, 1897:1 1893:f 1879:i 1855:, 1852:} 1849:2 1846:, 1843:1 1840:{ 1834:i 1812:2 1808:f 1804:, 1799:1 1795:f 1772:. 1763:, 1737:f 1706:. 1698:n 1694:f 1690:, 1684:, 1679:1 1675:f 1649:n 1645:X 1630:1 1626:X 1605:, 1602:} 1599:n 1596:, 1590:, 1587:1 1584:{ 1581:= 1578:I 1558:. 1553:i 1549:X 1543:I 1537:i 1497:: 1494:I 1488:i 1468:X 1462:Y 1459:: 1456:f 1436:, 1431:i 1427:X 1420:Y 1417:: 1412:i 1408:f 1387:I 1367:Y 1343:, 1338:i 1334:X 1327:X 1324:: 1319:i 1294:X 1268:I 1262:i 1257:) 1252:i 1248:X 1244:( 1220:. 1217:I 1186:. 1178:2 1174:f 1170:, 1165:1 1161:f 1135:2 1131:f 1108:1 1104:f 1080:f 1060:, 1055:2 1051:f 1031:, 1026:1 1022:f 1001:Y 949:2 922:1 894:h 886:2 878:= 870:2 845:h 837:1 829:= 821:1 794:2 790:X 781:1 777:X 766:X 762:: 759:h 734:2 726:, 718:1 710:, 703:X 671:. 666:2 662:X 639:1 635:X 614:C 572:2 568:X 559:1 555:X 548:Y 545:: 542:f 522:, 517:2 513:X 506:Y 503:: 498:2 494:f 474:, 469:1 465:X 458:Y 455:: 450:1 446:f 425:Y 395:2 391:X 384:X 381:: 376:2 352:, 347:1 343:X 336:X 333:: 328:1 303:, 298:2 294:X 285:1 281:X 260:, 257:X 235:2 231:X 208:1 204:X 183:. 180:C 158:2 154:X 131:1 127:X 106:. 103:C 23:.

Index

Product category
category theory
objects
category
mathematics
Cartesian product
sets
direct product
groups
rings
product
topological spaces
family
morphism
universal property
commutes
Universal property of the product
up to
canonical isomorphism
canonical projections
indexed
Universal product of the product
limit
discrete category
diagram
cone
universal construction
universal property of limits
product category
diagonal functor

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