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Epimorphism

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38: 2496:. Early category theorists believed that epimorphisms were the correct analogue of surjections in an arbitrary category, similar to how monomorphisms are very nearly an exact analogue of injections. Unfortunately this is incorrect; strong or regular epimorphisms behave much more closely to surjections than ordinary epimorphisms. 2511:
It is a common mistake to believe that epimorphisms are either identical to surjections or that they are a better concept. Unfortunately this is rarely the case; epimorphisms can be very mysterious and have unexpected behavior. It is very difficult, for example, to classify all the epimorphisms of
1420: 274:. Every epimorphism in this algebraic sense is an epimorphism in the sense of category theory, but the converse is not true in all categories. In this article, the term "epimorphism" will be used in the sense of category theory given above. For more on this, see 1511: 1581:
that sends each element to itself. Such a factorization of an arbitrary morphism into an epimorphism followed by a monomorphism can be carried out in all abelian categories and also in all the concrete categories mentioned above in
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is an epimorphism. In many concrete categories of interest the converse is also true. For example, in the following categories, the epimorphisms are exactly those morphisms that are surjective on the underlying sets:
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is considered as a category with a single object (composition of morphisms given by multiplication), then the epimorphisms are precisely the right-cancellable elements.
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In many categories it is possible to write every morphism as the composition of an epimorphism followed by a monomorphism. For instance, given a group homomorphism
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As some of the above examples show, the property of being an epimorphism is not determined by the morphism alone, but also by the category of context. If
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The above differs from the case of monomorphisms where it is more frequently true that monomorphisms are precisely those whose underlying functions are
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is considered as a category (objects are the vertices, morphisms are the paths, composition of morphisms is the concatenation of paths), then
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the concept corresponds exactly to the surjective functions), but they may not exactly coincide in all contexts; for example, the inclusion
1415:{\displaystyle {\begin{matrix}\operatorname {Hom} (Y,Z)&\rightarrow &\operatorname {Hom} (X,Z)\\g&\mapsto &gf\end{matrix}}} 2632: 1530:
is an epimorphism, a consequence of the uniqueness requirement in the definition of coequalizers. It follows in particular that every
2672: 2653: 2592: 105: 2018: 2363:; as noted above, it is a bimorphism, but it is not bijective and therefore not an isomorphism. Similarly, in the category of 2347:
since the inverse map is not continuous at 1, so it is an instance of a bimorphism that is not an isomorphism in the category
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However, there are also many concrete categories of interest where epimorphisms fail to be surjective. A few examples are:
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rings. In general, epimorphisms are their own unique concept, related to surjections but fundamentally different.
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and group homomorphisms. Also due to Schreier; the proof given in (Linderholm 1970) establishes this case as well.
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is an epimorphism. The converse, namely that every epimorphism be a coequalizer, is not true in all categories.
786: 2199: 2120: 501: 2315:. Every isomorphism is a bimorphism but the converse is not true in general. For example, the map from the 1434: 1026: 291: 242: 235: 227: 1883: 1267:. However the converse need not hold; the smaller category can (and often will) have more epimorphisms. 1018:, similar to the previous example. A similar argument shows that the natural ring homomorphism from any 553: 382: 68: 2459: 2324: 570: 2056: 1954: 2493: 1986: 1824: 669: 581: 546: 481: 189: 2251: 2155: 1739: 1632: 2789: 2682: 2316: 2293: 1922: 1154: 1088: 665: 574: 485: 476: 329: 2724: 2340: 726: 2709: 2668: 2649: 2628: 2609: 2588: 2497: 1007: 991: 386: 309: 287: 256: 2736: 2485: 1517: 1019: 681: 304: 252: 193: 1181:
is an epimorphism; indeed only a right-sided inverse is needed: if there exists a morphism
2508:, which are epimorphisms in the modern sense. However, this distinction never caught on. 2379: 2231: 2179: 1849: 1800: 1712: 1688: 694: 605: 368: 45: 2504:, which were maps in a concrete category whose underlying set maps were surjective, and 1874: 1215:
is easily seen to be an epimorphism. A map with such a right-sided inverse is called a
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with one amalgamated subgroup); an elementary proof can be found in (Linderholm 1970).
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This article is about the mathematical function. For the biological phenomenon, see
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The composition of two epimorphisms is again an epimorphism. If the composition
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of rings is a homological epimorphism if it is an epimorphism and it induces a
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between two categories turns epimorphisms into monomorphisms, and vice versa.
584:. This generalizes the two previous examples; to prove that every epimorphism 295: 268: 2755: 1426: 1139: 1123: 472:}. These maps are monotone if {0,1} is given the standard ordering 0 < 1. 1270:
As for most concepts in category theory, epimorphisms are preserved under
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and relation-preserving functions. Here we can use the same proof as for
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A morphism that is both a monomorphism and an epimorphism is called a
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as in the previous example. This follows from the observation that
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is uniquely determined by its value on the element represented by
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Handbook of Categorical Algebra. Volume 1: Basic Category Theory
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The definition of epimorphism may be reformulated to state that
1122:, the epimorphisms are precisely the continuous functions with 178:{\displaystyle g_{1}\circ f=g_{2}\circ f\implies g_{1}=g_{2}.} 2605:
An Invitation to General Algebra and Universal Constructions
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As for examples of epimorphisms in non-concrete categories:
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is a non-surjective epimorphism; to see this, note that any
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is a non-surjective epimorphism. To see this, suppose that
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AdΓ‘mek, JiΕ™Γ­; Herrlich, Horst; Strecker, George E. (1990).
2046:{\displaystyle \beta \circ \varepsilon =\mu \circ \alpha } 375:, equipping {0,1} with the full relation {0,1}×{0,1}. 1259:
that is an epimorphism when considered as a morphism in
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is surjective, we compose it with both the canonical
202: 108: 1790:{\displaystyle \varepsilon =\mu \circ \varepsilon '} 2701: 2560: 2260: 2240: 2220: 2188: 2164: 2141: 2109: 2077: 2045: 2007: 1975: 1943: 1904: 1858: 1838: 1809: 1789: 1748: 1721: 1697: 1677: 1641: 1561:as the composition of the surjective homomorphism 1505: 1414: 1325:is an epimorphism if and only if the induced maps 911:In the category of algebras over commutative ring 218: 177: 2110:{\displaystyle \delta \circ \varepsilon =\alpha } 963:), and the inverse of the element represented by 2700:Lawvere, F. William; Rosebrugh, Robert (2015). 1678:{\displaystyle \varepsilon =\mu \circ \varphi } 312:and functions. To prove that every epimorphism 2648:. Dover Publications, Inc Mineola, New York. 935:and the morphism is induced by the inclusion 496:(he actually proved more, showing that every 8: 1433:. This in turn is equivalent to the induced 219:{\displaystyle \mathbb {Z} \to \mathbb {Q} } 431:β†’ {0,1} be the characteristic function of { 328:is surjective, we compose it with both the 2500:attempted to create a distinction between 188:Epimorphisms are categorical analogues of 148: 144: 2663:Tsalenko, M.S.; Shulgeifer, E.G. (1974). 2378:Epimorphisms are used to define abstract 2253: 2233: 2201: 2181: 2157: 2122: 2090: 2058: 2020: 1988: 1956: 1924: 1885: 1851: 1826: 1802: 1765: 1741: 1714: 1690: 1658: 1634: 1586:(though not in all concrete categories). 1573:, followed by the injective homomorphism 1446: 1444: 1335: 1333: 1236:of two morphisms is an epimorphism, then 1052:is an epimorphism if and only if for all 212: 211: 204: 203: 201: 166: 153: 132: 113: 107: 2382:in general categories: two epimorphisms 2375:is a bimorphism but not an isomorphism. 2343:) is continuous and bijective but not a 2221:{\displaystyle \varepsilon \circ \mu =1} 2142:{\displaystyle \mu \circ \delta =\beta } 1126:images. For example, the inclusion map 1014:is determined entirely by its action on 676:is surjective, we proceed exactly as in 457:β†’ {0,1} the characteristic function of { 2548: 2538: 488:. The result that every epimorphism in 1229:and an epimorphism is an isomorphism. 1118:In the category of Hausdorff spaces, 672:. To prove that every epimorphism in 7: 2248:is called a right-sided inverse for 971:is just the element represented by βˆ’ 2725:"A Group Epimorphism is Surjective" 2351:. Another example is the embedding 1905:{\displaystyle \varepsilon :A\to B} 1626:of some pair of parallel morphisms. 71:in the sense that, for all objects 1290:is an epimorphism in the category 1134:, is a non-surjective epimorphism. 401:, β‰€) is not surjective, pick 25: 2795:Algebraic properties of elements 2581:Abstract and Concrete Categories 1846:is an epimorphism, the morphism 1594:Among other useful concepts are 275: 2422:if there exists an isomorphism 729:there is a continuous function 2741:10.1080/00029890.1970.11992448 2708:. Cambridge university press. 2665:Foundations of category theory 2627:. Cambridge University Press. 2561:Tsalenko & Shulgeifer 1974 2522:List of category theory topics 2078:{\displaystyle \delta :B\to C} 2069: 1999: 1976:{\displaystyle \alpha :A\to C} 1967: 1935: 1896: 1496: 1484: 1473: 1468: 1456: 1397: 1385: 1373: 1362: 1357: 1345: 208: 145: 1: 2729:American Mathematical Monthly 2008:{\displaystyle \beta :B\to D} 1839:{\displaystyle \varepsilon '} 1618:An epimorphism is said to be 1583: 1034:category of commutative rings 975:. Thus any homomorphism from 697:and continuous functions. If 2276:in ring theory. A morphism 2272:There is also the notion of 2261:{\displaystyle \varepsilon } 2165:{\displaystyle \varepsilon } 1749:{\displaystyle \varepsilon } 1642:{\displaystyle \varepsilon } 1516:being a monomorphism in the 190:onto or surjective functions 2688:Encyclopedia of Mathematics 2176:if there exists a morphism 1944:{\displaystyle \mu :C\to D} 1168:morphism is an epimorphism. 818:are two distinct maps from 361:β†’ {0,1} that is constant 1. 226:is a ring epimorphism. The 2811: 2645:Category Theory in Context 2053:, there exists a morphism 1760:if in each representation 1653:if in each representation 1549:, we can define the group 1272:equivalences of categories 1263:is also an epimorphism in 234:(i.e. an epimorphism in a 29: 2723:Linderholm, Carl (1970). 2623:Borceux, Francis (1994). 2587:. John Wiley & Sons. 2484:were first introduced by 2290:full and faithful functor 1255:, then every morphism in 890:, so the restrictions of 241:is a monomorphism in the 2602:Bergman, George (2015). 1240:must be an epimorphism. 530:and group homomorphisms. 492:is surjective is due to 2274:homological epimorphism 1302:) is an epimorphism in 1274:: given an equivalence 1225:, a map that is both a 951:(note that the unit in 709:is not surjective, let 557:-linear transformations 330:characteristic function 230:of an epimorphism is a 27:Surjective homomorphism 2262: 2242: 2222: 2190: 2166: 2143: 2111: 2079: 2047: 2009: 1977: 1945: 1906: 1878: 1860: 1840: 1811: 1791: 1750: 1723: 1699: 1679: 1643: 1507: 1435:natural transformation 1416: 1040:homomorphism of rings 947:generates the algebra 766:and the zero function 383:partially ordered sets 220: 179: 41: 2642:Riehl, Emily (2016). 2263: 2243: 2223: 2191: 2167: 2144: 2112: 2080: 2048: 2010: 1978: 1946: 1907: 1877: 1861: 1841: 1812: 1792: 1751: 1724: 1700: 1680: 1644: 1604:immediate epimorphism 1569:that is defined like 1508: 1417: 342:β†’ {0,1} of the image 221: 180: 40: 2704:Sets for Mathematics 2474:The companion terms 2460:equivalence relation 2252: 2241:{\displaystyle \mu } 2232: 2200: 2189:{\displaystyle \mu } 2180: 2156: 2121: 2089: 2057: 2019: 1987: 1955: 1923: 1884: 1866:is automatically an 1859:{\displaystyle \mu } 1850: 1825: 1810:{\displaystyle \mu } 1801: 1764: 1740: 1729:is automatically an 1722:{\displaystyle \mu } 1713: 1698:{\displaystyle \mu } 1689: 1657: 1633: 1600:extremal epimorphism 1443: 1429:for every choice of 1332: 1079:or is prime, and if 998:, the inclusion map 670:continuous functions 582:module homomorphisms 286:Every morphism in a 200: 106: 2494:surjective function 2492:as shorthand for a 2323:S (thought of as a 1596:regular epimorphism 787:category of monoids 713: ∈  682:indiscrete topology 680:, giving {0,1} the 486:group homomorphisms 18:Regular epimorphism 2768:Strong epimorphism 2317:half-open interval 2294:derived categories 2258: 2238: 2218: 2186: 2162: 2139: 2107: 2075: 2043: 2005: 1973: 1951:and any morphisms 1941: 1902: 1879: 1856: 1836: 1807: 1787: 1746: 1719: 1695: 1675: 1639: 1608:strong epimorphism 1503: 1501: 1412: 1410: 1087:, the induced map 1038:finitely generated 1029:is an epimorphism. 1025:to any one of its 666:topological spaces 387:monotone functions 276:Β§ Terminology 216: 175: 75:and all morphisms 69:right-cancellative 42: 2715:978-0-521-80444-8 2615:978-3-319-11478-1 2498:Saunders Mac Lane 1612:split epimorphism 1557:) and then write 1008:ring homomorphism 992:category of rings 826:. Then for some 290:whose underlying 288:concrete category 257:universal algebra 16:(Redirected from 2802: 2744: 2719: 2707: 2696: 2678: 2659: 2638: 2619: 2598: 2586: 2564: 2558: 2552: 2546: 2488:. Bourbaki uses 2380:quotient objects 2359:in the category 2267: 2265: 2264: 2259: 2247: 2245: 2244: 2239: 2227: 2225: 2224: 2219: 2195: 2193: 2192: 2187: 2171: 2169: 2168: 2163: 2148: 2146: 2145: 2140: 2116: 2114: 2113: 2108: 2084: 2082: 2081: 2076: 2052: 2050: 2049: 2044: 2014: 2012: 2011: 2006: 1982: 1980: 1979: 1974: 1950: 1948: 1947: 1942: 1911: 1909: 1908: 1903: 1865: 1863: 1862: 1857: 1845: 1843: 1842: 1837: 1835: 1816: 1814: 1813: 1808: 1796: 1794: 1793: 1788: 1786: 1755: 1753: 1752: 1747: 1728: 1726: 1725: 1720: 1704: 1702: 1701: 1696: 1684: 1682: 1681: 1676: 1648: 1646: 1645: 1640: 1590:Related concepts 1518:functor category 1512: 1510: 1509: 1504: 1502: 1421: 1419: 1418: 1413: 1411: 1020:commutative ring 695:Hausdorff spaces 369:binary relations 253:abstract algebra 251:Many authors in 225: 223: 222: 217: 215: 207: 194:category of sets 184: 182: 181: 176: 171: 170: 158: 157: 137: 136: 118: 117: 98: 21: 2810: 2809: 2805: 2804: 2803: 2801: 2800: 2799: 2780: 2779: 2752: 2747: 2722: 2716: 2699: 2681: 2675: 2662: 2656: 2641: 2635: 2622: 2616: 2601: 2595: 2584: 2577: 2573: 2568: 2567: 2559: 2555: 2547: 2540: 2535: 2518: 2472: 2457: 2450: 2439: 2432: 2418:are said to be 2417: 2406: 2399: 2388: 2341:Euler's formula 2250: 2249: 2230: 2229: 2198: 2197: 2178: 2177: 2154: 2153: 2152:An epimorphism 2119: 2118: 2087: 2086: 2055: 2054: 2017: 2016: 1985: 1984: 1953: 1952: 1921: 1920: 1882: 1881: 1880:An epimorphism 1848: 1847: 1828: 1823: 1822: 1799: 1798: 1779: 1762: 1761: 1738: 1737: 1736:An epimorphism 1711: 1710: 1709:, the morphism 1687: 1686: 1655: 1654: 1631: 1630: 1629:An epimorphism 1592: 1584:Β§ Examples 1500: 1499: 1476: 1471: 1441: 1440: 1409: 1408: 1400: 1395: 1389: 1388: 1365: 1360: 1330: 1329: 1294:if and only if 1202: 1175: 903: 896: 873: 862: 851: 840: 822:to some monoid 817: 810: 772: 765: 746: 735: 727:Urysohn's Lemma 639: 613: 467: 452: 441: 426: 407: 356: 337: 284: 198: 197: 162: 149: 128: 109: 104: 103: 89: 82: 76: 46:category theory 35: 28: 23: 22: 15: 12: 11: 5: 2808: 2806: 2798: 2797: 2792: 2782: 2781: 2778: 2777: 2765: 2751: 2750:External links 2748: 2746: 2745: 2735:(2): 176–177. 2720: 2714: 2697: 2679: 2673: 2660: 2654: 2639: 2634:978-0521061193 2633: 2620: 2614: 2599: 2593: 2574: 2572: 2569: 2566: 2565: 2553: 2537: 2536: 2534: 2531: 2530: 2529: 2524: 2517: 2514: 2506:epic morphisms 2471: 2468: 2455: 2448: 2437: 2430: 2415: 2404: 2397: 2386: 2270: 2269: 2257: 2237: 2228:(in this case 2217: 2214: 2211: 2208: 2205: 2185: 2172:is said to be 2161: 2150: 2138: 2135: 2132: 2129: 2126: 2106: 2103: 2100: 2097: 2094: 2074: 2071: 2068: 2065: 2062: 2042: 2039: 2036: 2033: 2030: 2027: 2024: 2004: 2001: 1998: 1995: 1992: 1972: 1969: 1966: 1963: 1960: 1940: 1937: 1934: 1931: 1928: 1912:is said to be 1901: 1898: 1895: 1892: 1889: 1871: 1855: 1834: 1831: 1806: 1785: 1782: 1778: 1775: 1772: 1769: 1756:is said to be 1745: 1734: 1718: 1694: 1674: 1671: 1668: 1665: 1662: 1649:is said to be 1638: 1627: 1591: 1588: 1514: 1513: 1498: 1495: 1492: 1489: 1486: 1483: 1480: 1477: 1475: 1472: 1470: 1467: 1464: 1461: 1458: 1455: 1452: 1449: 1448: 1423: 1422: 1407: 1404: 1401: 1399: 1396: 1394: 1391: 1390: 1387: 1384: 1381: 1378: 1375: 1372: 1369: 1366: 1364: 1361: 1359: 1356: 1353: 1350: 1347: 1344: 1341: 1338: 1337: 1227:monic morphism 1198: 1174: 1171: 1170: 1169: 1162:directed graph 1158: 1136: 1135: 1116: 1030: 988: 931:of the monoid 909: 901: 894: 871: 860: 849: 838: 815: 808: 779: 778: 770: 763: 744: 733: 725:is closed, by 685: 657: 637: 611: 560: 531: 528:abelian groups 519: 509: 473: 465: 450: 439: 424: 405: 376: 362: 354: 350:) and the map 335: 283: 280: 214: 210: 206: 186: 185: 174: 169: 165: 161: 156: 152: 147: 143: 140: 135: 131: 127: 124: 121: 116: 112: 87: 80: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 2807: 2796: 2793: 2791: 2788: 2787: 2785: 2776: 2774: 2769: 2766: 2764: 2762: 2757: 2754: 2753: 2749: 2742: 2738: 2734: 2730: 2726: 2721: 2717: 2711: 2706: 2705: 2698: 2694: 2690: 2689: 2684: 2683:"Epimorphism" 2680: 2676: 2674:5-02-014427-4 2670: 2666: 2661: 2657: 2655:9780486809038 2651: 2647: 2646: 2640: 2636: 2630: 2626: 2621: 2617: 2611: 2607: 2606: 2600: 2596: 2594:0-471-60922-6 2590: 2583: 2582: 2576: 2575: 2570: 2562: 2557: 2554: 2550: 2545: 2543: 2539: 2532: 2528: 2525: 2523: 2520: 2519: 2515: 2513: 2509: 2507: 2503: 2499: 2495: 2491: 2487: 2483: 2482: 2477: 2469: 2467: 2465: 2461: 2458:. This is an 2454: 2447: 2443: 2436: 2429: 2425: 2421: 2414: 2410: 2403: 2396: 2392: 2385: 2381: 2376: 2374: 2370: 2366: 2362: 2358: 2354: 2350: 2346: 2345:homeomorphism 2342: 2338: 2334: 2331:) that sends 2330: 2329:complex plane 2326: 2322: 2319:[0,1) to the 2318: 2314: 2309: 2307: 2303: 2299: 2295: 2291: 2287: 2283: 2279: 2275: 2255: 2235: 2215: 2212: 2209: 2206: 2203: 2183: 2175: 2159: 2151: 2136: 2133: 2130: 2127: 2124: 2104: 2101: 2098: 2095: 2092: 2072: 2066: 2063: 2060: 2040: 2037: 2034: 2031: 2028: 2025: 2022: 2002: 1996: 1993: 1990: 1970: 1964: 1961: 1958: 1938: 1932: 1929: 1926: 1919: 1915: 1899: 1893: 1890: 1887: 1876: 1872: 1869: 1853: 1832: 1829: 1820: 1804: 1783: 1780: 1776: 1773: 1770: 1767: 1759: 1743: 1735: 1732: 1716: 1708: 1692: 1672: 1669: 1666: 1663: 1660: 1652: 1636: 1628: 1625: 1621: 1617: 1616: 1615: 1613: 1609: 1605: 1601: 1597: 1589: 1587: 1585: 1580: 1576: 1572: 1568: 1564: 1560: 1556: 1552: 1548: 1544: 1540: 1535: 1533: 1529: 1524: 1522: 1519: 1493: 1490: 1487: 1481: 1478: 1465: 1462: 1459: 1453: 1450: 1439: 1438: 1437: 1436: 1432: 1428: 1405: 1402: 1392: 1382: 1379: 1376: 1370: 1367: 1354: 1351: 1348: 1342: 1339: 1328: 1327: 1326: 1324: 1320: 1316: 1311: 1309: 1305: 1301: 1297: 1293: 1289: 1286:, a morphism 1285: 1281: 1277: 1273: 1268: 1266: 1262: 1258: 1254: 1250: 1246: 1241: 1239: 1235: 1230: 1228: 1224: 1220: 1219: 1214: 1210: 1206: 1201: 1196: 1192: 1188: 1184: 1180: 1172: 1167: 1163: 1159: 1156: 1152: 1148: 1147: 1146: 1143: 1141: 1133: 1129: 1125: 1121: 1117: 1114: 1110: 1106: 1102: 1098: 1094: 1090: 1086: 1082: 1078: 1074: 1070: 1067:generated by 1066: 1062: 1058: 1055: 1051: 1047: 1043: 1039: 1035: 1031: 1028: 1027:localizations 1024: 1021: 1017: 1013: 1009: 1005: 1001: 997: 993: 989: 986: 982: 978: 974: 970: 966: 962: 958: 954: 950: 946: 942: 938: 934: 930: 926: 922: 918: 914: 910: 907: 900: 893: 889: 885: 881: 877: 870: 866: 859: 855: 848: 844: 837: 833: 829: 825: 821: 814: 807: 803: 799: 796: 795:inclusion map 792: 788: 784: 783: 782: 776: 769: 762: 758: 755:. We compose 754: 750: 743: 740:β†’ such that 739: 732: 728: 724: 720: 717: βˆ’  716: 712: 708: 704: 700: 696: 693: 689: 686: 683: 679: 675: 671: 667: 663: 662: 658: 655: 651: 647: 643: 636: 633: 629: 625: 621: 617: 610: 607: 603: 599: 595: 591: 587: 583: 579: 576: 572: 571:right modules 568: 564: 561: 558: 556: 551: 548: 544: 543:vector spaces 540: 539: 537: 532: 529: 525: 524: 520: 517: 516:finite groups 513: 510: 507: 503: 499: 495: 494:Otto Schreier 491: 487: 483: 479: 478: 474: 471: 464: 460: 456: 449: 445: 438: 434: 430: 423: 419: 415: 411: 404: 400: 397:, β‰€) β†’ ( 396: 392: 388: 384: 380: 377: 374: 370: 366: 363: 360: 353: 349: 345: 341: 334: 331: 327: 323: 319: 315: 311: 307: 306: 302: 301: 300: 297: 293: 289: 281: 279: 277: 273: 270: 266: 263:simply as an 262: 258: 254: 249: 247: 244: 243:dual category 240: 237: 233: 229: 195: 191: 172: 167: 163: 159: 154: 150: 141: 138: 133: 129: 125: 122: 119: 114: 110: 102: 101: 100: 97: 93: 86: 79: 74: 70: 66: 62: 58: 55: 51: 47: 39: 33: 19: 2772: 2760: 2732: 2728: 2703: 2686: 2664: 2644: 2624: 2608:. Springer. 2604: 2580: 2556: 2549:Borceux 1994 2527:Monomorphism 2510: 2505: 2502:epimorphisms 2501: 2489: 2481:monomorphism 2479: 2475: 2473: 2463: 2452: 2445: 2441: 2434: 2427: 2423: 2419: 2412: 2408: 2401: 2394: 2390: 2383: 2377: 2372: 2368: 2360: 2356: 2352: 2348: 2336: 2332: 2310: 2305: 2301: 2297: 2285: 2281: 2277: 2273: 2271: 2173: 1918:monomorphism 1913: 1819:monomorphism 1757: 1707:monomorphism 1650: 1619: 1611: 1607: 1603: 1599: 1595: 1593: 1578: 1574: 1570: 1566: 1562: 1558: 1554: 1550: 1546: 1542: 1538: 1536: 1525: 1520: 1515: 1430: 1424: 1322: 1318: 1314: 1312: 1303: 1299: 1295: 1291: 1287: 1283: 1279: 1275: 1269: 1264: 1260: 1256: 1252: 1244: 1242: 1237: 1233: 1231: 1216: 1212: 1208: 1204: 1199: 1194: 1190: 1186: 1182: 1176: 1165: 1144: 1137: 1131: 1127: 1119: 1104: 1100: 1096: 1092: 1084: 1080: 1076: 1075:) is either 1072: 1068: 1064: 1063:, the ideal 1060: 1056: 1054:prime ideals 1049: 1045: 1041: 1022: 1015: 1011: 1003: 999: 995: 984: 980: 976: 972: 968: 964: 960: 956: 955:is given by 952: 948: 944: 940: 936: 932: 924: 920: 916: 912: 908:are unequal. 905: 898: 891: 887: 883: 879: 875: 868: 864: 857: 853: 846: 842: 835: 831: 827: 823: 819: 812: 805: 801: 797: 790: 780: 774: 767: 760: 756: 752: 748: 741: 737: 730: 722: 718: 714: 710: 706: 702: 698: 687: 677: 673: 659: 653: 649: 645: 641: 634: 627: 623: 619: 615: 608: 606:quotient map 601: 597: 593: 589: 585: 577: 566: 562: 554: 549: 535: 533: 521: 511: 506:free product 489: 475: 469: 462: 458: 454: 447: 443: 436: 432: 428: 421: 417: 413: 409: 402: 398: 394: 390: 378: 372: 367:: sets with 364: 358: 351: 347: 343: 339: 332: 325: 321: 317: 313: 303: 285: 272:homomorphism 264: 260: 250: 245: 238: 232:monomorphism 192:(and in the 187: 95: 91: 84: 77: 72: 64: 60: 56: 49: 43: 32:Epimorphosis 2756:epimorphism 2490:epimorphism 2476:epimorphism 2470:Terminology 2321:unit circle 2300:) : D( 1916:if for any 1868:isomorphism 1731:isomorphism 1624:coequalizer 1622:if it is a 1528:coequalizer 1249:subcategory 1179:isomorphism 1115:IV 17.2.6). 1109:isomorphism 929:monoid ring 878:). Either 261:epimorphism 50:epimorphism 2784:Categories 2571:References 2420:equivalent 2367:, the map 2335:to exp(2Ο€i 2313:bimorphism 2196:such that 2085:such that 2015:such that 1193:such that 1173:Properties 759:with both 630:) and the 504:using the 420:) and let 296:surjective 269:surjective 259:define an 2790:Morphisms 2693:EMS Press 2667:. Nauka. 2256:ε 2236:μ 2210:μ 2207:∘ 2204:ε 2184:μ 2160:ε 2137:β 2131:δ 2128:∘ 2125:μ 2105:α 2099:ε 2096:∘ 2093:δ 2070:→ 2061:δ 2041:α 2038:∘ 2035:μ 2029:ε 2026:∘ 2023:β 2000:→ 1991:β 1968:→ 1959:α 1936:→ 1927:μ 1897:→ 1888:ε 1854:μ 1830:ε 1805:μ 1781:ε 1777:∘ 1774:μ 1768:ε 1758:immediate 1744:ε 1717:μ 1693:μ 1673:φ 1670:∘ 1667:μ 1661:ε 1637:ε 1494:− 1482:⁡ 1474:→ 1466:− 1454:⁡ 1427:injective 1398:↦ 1371:⁡ 1363:→ 1343:⁡ 1218:split epi 1140:injective 1099:) β†’ Frac( 751:and 1 on 502:equalizer 393: : ( 209:→ 146:⟹ 139:∘ 120:∘ 2516:See also 2486:Bourbaki 2426: : 2407: : 2389: : 2371: β†’ 2355: β†’ 2325:subspace 1833:′ 1797:, where 1784:′ 1685:, where 1651:extremal 1541: : 1532:cokernel 1317: : 1278: : 1221:. In a 1185: : 1107:) is an 1044: : 923:, where 747:is 0 on 721:. Since 632:zero map 498:subgroup 453: : 427: : 292:function 282:Examples 236:category 67:that is 59: : 54:morphism 2770:at the 2758:at the 2695:, 2001 2339:) (see 2327:of the 1620:regular 1308:duality 1203:, then 1083:is not 1032:In the 990:In the 927:is the 915:, take 785:In the 692:compact 573:over a 545:over a 278:below. 2712:  2671:  2652:  2631:  2612:  2591:  2444:  2304:) β†’ D( 1914:strong 1610:, and 1526:Every 1247:is a 1177:Every 1151:monoid 886:is in 856:), so 793:, the 512:FinGrp 500:is an 482:groups 446:} and 2585:(PDF) 2533:Notes 2440:with 2365:rings 2174:split 1817:is a 1705:is a 1553:= im( 1223:topos 1166:every 1160:If a 1149:If a 1124:dense 688:HComp 547:field 538:-Vect 468:< 389:. If 52:is a 48:, an 2710:ISBN 2669:ISBN 2650:ISBN 2629:ISBN 2610:ISBN 2589:ISBN 2478:and 2400:and 2361:Haus 2296:: D( 2117:and 1983:and 1821:and 1425:are 1306:. A 1197:= id 1155:ring 1120:Haus 1089:Frac 1036:, a 996:Ring 897:and 882:or βˆ’ 867:) β‰  845:) β‰  811:and 668:and 580:and 575:ring 552:and 484:and 385:and 310:sets 265:onto 255:and 228:dual 2775:Lab 2763:Lab 2737:doi 2349:Top 2308:). 2292:on 1614:. 1521:Set 1479:Hom 1451:Hom 1368:Hom 1340:Hom 1251:of 1153:or 1113:EGA 1059:of 1010:on 983:of 967:in 959:of 904:to 830:in 791:Mon 777:β†’ . 678:Set 674:Top 661:Top 598:Mod 596:in 563:Mod 490:Grp 477:Grp 408:in 379:Pos 373:Set 365:Rel 326:Set 324:in 305:Set 294:is 267:or 248:). 44:In 2786:: 2733:77 2731:. 2727:. 2691:, 2685:, 2541:^ 2466:. 2451:= 2433:β†’ 2411:β†’ 2393:β†’ 2284:β†’ 2280:: 2268:). 1606:, 1602:, 1598:, 1577:β†’ 1565:β†’ 1545:β†’ 1523:. 1321:β†’ 1282:β†’ 1234:fg 1211:β†’ 1207:: 1195:fj 1189:β†’ 1142:. 1130:β†’ 1048:β†’ 1002:β†’ 994:, 939:β†’ 919:β†’ 874:(βˆ’ 863:(βˆ’ 834:, 800:β†’ 789:, 773:: 749:fX 723:fX 719:fX 705:β†’ 701:: 690:: 664:: 656:). 644:β†’ 640:: 618:β†’ 614:: 592:β†’ 588:: 569:: 541:: 526:: 523:Ab 514:: 480:: 461:| 442:≀ 435:| 412:\ 381:: 357:: 338:: 320:β†’ 316:: 308:: 99:, 94:β†’ 90:: 83:, 63:β†’ 2773:n 2761:n 2743:. 2739:: 2718:. 2677:. 2658:. 2637:. 2618:. 2597:. 2563:. 2551:. 2464:X 2456:2 2453:f 2449:1 2446:f 2442:j 2438:2 2435:Y 2431:1 2428:Y 2424:j 2416:2 2413:Y 2409:X 2405:2 2402:f 2398:1 2395:Y 2391:X 2387:1 2384:f 2373:Q 2369:Z 2357:R 2353:Q 2337:x 2333:x 2306:A 2302:B 2298:f 2286:B 2282:A 2278:f 2216:1 2213:= 2149:. 2134:= 2102:= 2073:C 2067:B 2064:: 2032:= 2003:D 1997:B 1994:: 1971:C 1965:A 1962:: 1939:D 1933:C 1930:: 1900:B 1894:A 1891:: 1870:. 1771:= 1733:. 1664:= 1579:H 1575:K 1571:f 1567:K 1563:G 1559:f 1555:f 1551:K 1547:H 1543:G 1539:f 1497:) 1491:, 1488:X 1485:( 1469:) 1463:, 1460:Y 1457:( 1431:Z 1406:f 1403:g 1393:g 1386:) 1383:Z 1380:, 1377:X 1374:( 1358:) 1355:Z 1352:, 1349:Y 1346:( 1323:Y 1319:X 1315:f 1304:D 1300:f 1298:( 1296:F 1292:C 1288:f 1284:D 1280:C 1276:F 1265:D 1261:C 1257:D 1253:C 1245:D 1238:f 1213:Y 1209:X 1205:f 1200:Y 1191:X 1187:Y 1183:j 1132:R 1128:Q 1111:( 1105:Q 1103:/ 1101:S 1097:P 1095:/ 1093:R 1091:( 1085:S 1081:Q 1077:S 1073:P 1071:( 1069:f 1065:Q 1061:R 1057:P 1050:S 1046:R 1042:f 1023:R 1016:Z 1012:Q 1004:Q 1000:Z 987:. 985:Z 981:1 977:R 973:n 969:Z 965:n 961:Z 957:0 953:R 949:R 945:1 941:Z 937:N 933:G 925:R 921:R 917:R 913:R 906:N 902:2 899:g 895:1 892:g 888:N 884:n 880:n 876:n 872:2 869:g 865:n 861:1 858:g 854:n 852:( 850:2 847:g 843:n 841:( 839:1 836:g 832:Z 828:n 824:M 820:Z 816:2 813:g 809:1 806:g 802:Z 798:N 775:Y 771:2 768:g 764:1 761:g 757:f 753:y 745:1 742:g 738:Y 736:: 734:1 731:g 715:Y 711:y 707:Y 703:X 699:f 654:X 652:( 650:f 648:/ 646:Y 642:Y 638:2 635:g 628:X 626:( 624:f 622:/ 620:Y 616:Y 612:1 609:g 602:R 600:- 594:Y 590:X 586:f 578:R 567:R 565:- 559:. 555:K 550:K 536:K 470:y 466:0 463:y 459:y 455:Y 451:2 448:g 444:y 440:0 437:y 433:y 429:Y 425:1 422:g 418:X 416:( 414:f 410:Y 406:0 403:y 399:Y 395:X 391:f 359:Y 355:2 352:g 348:X 346:( 344:f 340:Y 336:1 333:g 322:Y 318:X 314:f 246:C 239:C 213:Q 205:Z 173:. 168:2 164:g 160:= 155:1 151:g 142:f 134:2 130:g 126:= 123:f 115:1 111:g 96:Z 92:Y 88:2 85:g 81:1 78:g 73:Z 65:Y 61:X 57:f 34:. 20:)

Index

Regular epimorphism
Epimorphosis

category theory
morphism
right-cancellative
onto or surjective functions
category of sets
dual
monomorphism
category
dual category
abstract algebra
universal algebra
surjective
homomorphism
Β§ Terminology
concrete category
function
surjective
Set
sets
characteristic function
binary relations
partially ordered sets
monotone functions
Grp
groups
group homomorphisms
Otto Schreier

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