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Snake lemma

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575: 805: 818: 556: 258: 81: 2084: 124: 1485: 1802:. Then the connecting homomorphism can still be defined, and one can write down a sequence as in the statement of the snake lemma. This will always be a chain complex, but it may fail to be exact. Exactness can be asserted, however, when the vertical sequences in the diagram are exact, that is, when the images of 582:
The maps between the kernels and the maps between the cokernels are induced in a natural manner by the given (horizontal) maps because of the diagram's commutativity. The exactness of the two induced sequences follows in a straightforward way from the exactness of the rows of the original diagram.
1949: 253:{\displaystyle \ker a~{\color {Gray}\longrightarrow }~\ker b~{\color {Gray}\longrightarrow }~\ker c~{\overset {d}{\longrightarrow }}~\operatorname {coker} a~{\color {Gray}\longrightarrow }~\operatorname {coker} b~{\color {Gray}\longrightarrow }~\operatorname {coker} c} 1667: 2277: 779:
Once that is done, the theorem is proven for abelian groups or modules over a ring. For the general case, the argument may be rephrased in terms of properties of arrows and cancellation instead of elements. Alternatively, one may invoke
384: 1197: 1478: 1368: 540: 489: 438: 2079:{\displaystyle {\begin{matrix}&1&\to &C_{3}&\to &C_{3}&\to 1\\&\downarrow &&\downarrow &&\downarrow \\1\to &1&\to &S_{3}&\to &A_{5}\end{matrix}}} 811:
is a commutative diagram with exact rows, then the snake lemma can be applied twice, to the "front" and to the "back", yielding two long exact sequences; these are related by a commutative diagram of the form
328: 1941: 1685:, hold for abelian categories as well as in the category of groups, the snake lemma does not. Indeed, arbitrary cokernels do not exist. However, one can replace cokernels by (left) cosets 1800: 1761: 1722: 1493: 1264: 2225: 2190: 968: 341: 2217: 2144: 2114: 1884: 1854: 1220: 1057: 1028: 1008: 988: 936: 907: 887: 867: 847: 1065: 1373: 562:
and then the exact sequence that is the conclusion of the lemma can be drawn on this expanded diagram in the reversed "S" shape of a slithering
2425: 1269: 2543: 494: 443: 392: 2474: 2451: 285: 781: 804: 772:), that it is a homomorphism, and that the resulting long sequence is indeed exact. One may routinely verify the exactness by 2392: 817: 2466: 2538: 1893: 1662:{\displaystyle \ker(t_{M})\to \ker(t_{N})\to \ker(t_{P})\to M\otimes _{k}k\to N\otimes _{k}k\to P\otimes _{k}k\to 0} 99: 1766: 1727: 1688: 1225: 2435: 2382: 2297: 2272:{\displaystyle 1\longrightarrow 1\longrightarrow 1\longrightarrow 1\longrightarrow C_{2}\longrightarrow 1} 793: 2342: 1669:
by applying the snake lemma. Thus, the snake lemma reflects the tensor product's failure to be exact.
792:
In the applications, one often needs to show that long exact sequences are "natural" (in the sense of
594: 2387: 773: 72: 32: 28: 2153: 598: 40: 574: 379:{\displaystyle \operatorname {coker} b~{\color {Gray}\longrightarrow }~\operatorname {coker} c} 2493: 2470: 2447: 2421: 2413: 1827: 941: 2439: 56: 36: 2195: 2122: 2092: 1862: 1832: 1480:
is not exact in general. Hence, a natural question arises. Why is this sequence not exact?
1857: 1815: 68: 2292: 1205: 1033: 1013: 993: 973: 912: 892: 872: 852: 832: 88: 2510: 2532: 2310: 60: 555: 2367: 2147: 1887: 1192:{\displaystyle V\otimes _{k}k=V\otimes _{k}(k/(t))=V/tV=\operatorname {coker} (t).} 279: 64: 39:
and is a crucial tool in homological algebra and its applications, for instance in
80: 796:). This follows from the naturality of the sequence produced by the snake lemma. 550:
To see where the snake lemma gets its name, expand the diagram above as follows:
2496: 335: 92: 24: 2519: 2514: 2409: 2150:, the right vertical arrow has trivial cokernel. Meanwhile the quotient group 1682: 1678: 625: 2501: 1473:{\displaystyle 0\to M\otimes _{k}k\to N\otimes _{k}k\to P\otimes _{k}k\to 0} 103: 2523: 1363:{\displaystyle M\otimes _{k}k\to N\otimes _{k}k\to P\otimes _{k}k\to 0} 1484: 563: 2219:. The sequence in the statement of the snake lemma is therefore 1490:
According to the diagram above, we can induce an exact sequence
535:{\displaystyle \operatorname {coker} c=C'/\operatorname {im} c} 484:{\displaystyle \operatorname {coker} b=B'/\operatorname {im} b} 433:{\displaystyle \operatorname {coker} a=A'/\operatorname {im} a} 43:. Homomorphisms constructed with its help are generally called 323:{\displaystyle \ker a~{\color {Gray}\longrightarrow }~\ker b} 1943:. This gives rise to the following diagram with exact rows: 1886:, which in turn can be written as a semidirect product of 1677:
While many results of homological algebra, such as the
1370:
by right exactness of tensor product. But the sequence
648:. Because of the commutativity of the diagram, we have 1954: 2228: 2198: 2156: 2125: 2095: 1952: 1896: 1865: 1835: 1769: 1730: 1691: 1496: 1376: 1272: 1228: 1208: 1068: 1036: 1016: 996: 976: 944: 915: 895: 875: 855: 835: 497: 446: 395: 344: 288: 127: 2295:'s character at the very beginning of the 1980 film 2116:
is not a normal subgroup in the semidirect product.
700:. Since the bottom row is exact, we find an element 2271: 2211: 2184: 2138: 2108: 2078: 1935: 1878: 1848: 1794: 1755: 1716: 1661: 1472: 1362: 1258: 1214: 1191: 1051: 1022: 1002: 982: 962: 930: 901: 881: 861: 841: 534: 483: 432: 378: 322: 252: 2368:"The Topological Snake Lemma and Corona Algebras" 583:The important statement of the lemma is that a 1936:{\displaystyle S_{3}\simeq C_{3}\rtimes C_{2}} 1856:: this contains a subgroup isomorphic to the 578:An animation of the construction of the map d 98:Then there is an exact sequence relating the 8: 590:exists which completes the exact sequence. 2420:(3rd ed.). Springer. pp. 157–9. 2291:The proof of the snake lemma is taught by 2089:Note that the middle column is not exact: 2386: 2257: 2227: 2203: 2197: 2176: 2167: 2161: 2155: 2130: 2124: 2100: 2094: 2066: 2049: 1989: 1972: 1953: 1951: 1927: 1914: 1901: 1895: 1870: 1864: 1840: 1834: 1778: 1768: 1739: 1729: 1700: 1690: 1635: 1607: 1579: 1560: 1535: 1510: 1495: 1446: 1418: 1390: 1375: 1336: 1308: 1280: 1271: 1227: 1207: 1157: 1134: 1104: 1076: 1067: 1035: 1015: 995: 990:-linear transformation, so we can tensor 975: 943: 914: 894: 874: 854: 834: 518: 496: 467: 445: 416: 394: 357: 343: 301: 287: 231: 209: 184: 162: 140: 126: 573: 2322: 1795:{\displaystyle C'/\operatorname {im} c} 1756:{\displaystyle B'/\operatorname {im} b} 1717:{\displaystyle A'/\operatorname {im} a} 1259:{\displaystyle 0\to M\to N\to P\to 0} 358: 302: 232: 210: 163: 141: 7: 2329: 35:. The snake lemma is valid in every 2444:Introduction to Commutative Algebra 2461:Hilton, P.; Stammbach, U. (1997). 1266:, we can induce an exact sequence 776:(see the proof of Lemma 9.1 in ). 14: 593:In the case of abelian groups or 2398:from the original on 2022-10-09. 2283:which indeed fails to be exact. 1483: 1202:Given a short exact sequence of 816: 803: 554: 267:is a homomorphism, known as the 79: 2463:A course in homological algebra 2375:New York Journal of Mathematics 605:can be constructed as follows: 2263: 2250: 2244: 2238: 2232: 2057: 2040: 2030: 2020: 2014: 2008: 1997: 1980: 1963: 1653: 1645: 1639: 1625: 1617: 1611: 1597: 1589: 1583: 1569: 1566: 1553: 1544: 1541: 1528: 1519: 1516: 1503: 1464: 1456: 1450: 1436: 1428: 1422: 1408: 1400: 1394: 1380: 1354: 1346: 1340: 1326: 1318: 1312: 1298: 1290: 1284: 1250: 1244: 1238: 1232: 1183: 1177: 1148: 1145: 1139: 1131: 1125: 1119: 1114: 1108: 1086: 1080: 1046: 1040: 954: 925: 919: 359: 303: 233: 211: 186: 164: 142: 16:Theorem in homological algebra 1: 2467:Graduate Texts in Mathematics 752:). Now one has to check that 616:and view it as an element of 274:Furthermore, if the morphism 782:Mitchell's embedding theorem 728:is unique by injectivity of 2185:{\displaystyle S_{3}/C_{3}} 2560: 282:, then so is the morphism 2544:Lemmas in category theory 1673:In the category of groups 768:and not on the choice of 59:(such as the category of 2520:Proof of the Snake Lemma 2469:. Springer. p. 99. 2414:"III §9 The Snake Lemma" 2366:Schochet, C. L. (1999). 2343:"Extensions of C2 by C3" 963:{\displaystyle t:V\to V} 732: '. We then define 570:Construction of the maps 389:The cokernels here are: 45:connecting homomorphisms 794:natural transformations 756:is well-defined (i.e., 585:connecting homomorphism 546:Explanation of the name 269:connecting homomorphism 2273: 2213: 2186: 2140: 2110: 2080: 1937: 1880: 1850: 1796: 1757: 1718: 1663: 1474: 1364: 1260: 1216: 1193: 1053: 1024: 1004: 984: 964: 932: 903: 883: 863: 843: 696:) is in the kernel of 579: 536: 485: 434: 380: 324: 254: 2274: 2214: 2212:{\displaystyle C_{2}} 2187: 2141: 2139:{\displaystyle A_{5}} 2111: 2109:{\displaystyle C_{2}} 2081: 1938: 1881: 1879:{\displaystyle S_{3}} 1851: 1849:{\displaystyle A_{5}} 1797: 1758: 1719: 1664: 1475: 1365: 1261: 1217: 1194: 1054: 1025: 1005: 985: 965: 933: 904: 884: 864: 844: 577: 537: 486: 435: 381: 325: 255: 2226: 2196: 2154: 2123: 2093: 1950: 1894: 1863: 1833: 1767: 1728: 1689: 1494: 1374: 1270: 1226: 1206: 1066: 1034: 1014: 994: 974: 942: 913: 893: 873: 853: 833: 684:is in the kernel of 495: 444: 393: 342: 286: 125: 33:long exact sequences 2539:Homological algebra 87:where the rows are 73:commutative diagram 63:or the category of 29:homological algebra 2494:Weisstein, Eric W. 2446:. Addison–Wesley. 2287:In popular culture 2269: 2209: 2182: 2136: 2106: 2076: 2074: 1933: 1876: 1846: 1792: 1753: 1714: 1659: 1470: 1360: 1256: 1212: 1189: 1049: 1020: 1000: 980: 960: 928: 899: 879: 859: 839: 764:) only depends on 580: 532: 481: 430: 376: 362: 320: 306: 250: 236: 214: 167: 145: 41:algebraic topology 23:is a tool used in 2427:978-0-387-95385-4 2192:is isomorphic to 1828:alternating group 1215:{\displaystyle k} 1052:{\displaystyle k} 1023:{\displaystyle k} 1003:{\displaystyle V} 983:{\displaystyle k} 931:{\displaystyle k} 902:{\displaystyle V} 882:{\displaystyle k} 862:{\displaystyle V} 842:{\displaystyle k} 688:), and therefore 366: 356: 310: 300: 240: 230: 218: 208: 196: 192: 183: 171: 161: 149: 139: 2551: 2507: 2506: 2480: 2457: 2440:Macdonald, I. G. 2431: 2400: 2399: 2397: 2390: 2372: 2363: 2357: 2356: 2354: 2353: 2339: 2333: 2327: 2278: 2276: 2275: 2270: 2262: 2261: 2218: 2216: 2215: 2210: 2208: 2207: 2191: 2189: 2188: 2183: 2181: 2180: 2171: 2166: 2165: 2145: 2143: 2142: 2137: 2135: 2134: 2115: 2113: 2112: 2107: 2105: 2104: 2085: 2083: 2082: 2077: 2075: 2071: 2070: 2054: 2053: 2018: 2012: 2006: 1994: 1993: 1977: 1976: 1956: 1942: 1940: 1939: 1934: 1932: 1931: 1919: 1918: 1906: 1905: 1885: 1883: 1882: 1877: 1875: 1874: 1855: 1853: 1852: 1847: 1845: 1844: 1816:normal subgroups 1801: 1799: 1798: 1793: 1782: 1777: 1762: 1760: 1759: 1754: 1743: 1738: 1723: 1721: 1720: 1715: 1704: 1699: 1668: 1666: 1665: 1660: 1649: 1648: 1621: 1620: 1593: 1592: 1565: 1564: 1540: 1539: 1515: 1514: 1487: 1479: 1477: 1476: 1471: 1460: 1459: 1432: 1431: 1404: 1403: 1369: 1367: 1366: 1361: 1350: 1349: 1322: 1321: 1294: 1293: 1265: 1263: 1262: 1257: 1221: 1219: 1218: 1213: 1198: 1196: 1195: 1190: 1161: 1138: 1118: 1117: 1090: 1089: 1058: 1056: 1055: 1050: 1029: 1027: 1026: 1021: 1009: 1007: 1006: 1001: 989: 987: 986: 981: 969: 967: 966: 961: 937: 935: 934: 929: 908: 906: 905: 900: 888: 886: 885: 880: 868: 866: 865: 860: 848: 846: 845: 840: 820: 807: 608:Pick an element 558: 541: 539: 538: 533: 522: 517: 490: 488: 487: 482: 471: 466: 439: 437: 436: 431: 420: 415: 385: 383: 382: 377: 364: 363: 354: 329: 327: 326: 321: 308: 307: 298: 259: 257: 256: 251: 238: 237: 228: 216: 215: 206: 194: 193: 185: 181: 169: 168: 159: 147: 146: 137: 83: 57:abelian category 37:abelian category 31:, to construct 2559: 2558: 2554: 2553: 2552: 2550: 2549: 2548: 2529: 2528: 2492: 2491: 2488: 2483: 2477: 2460: 2454: 2434: 2428: 2408: 2404: 2403: 2395: 2370: 2365: 2364: 2360: 2351: 2349: 2341: 2340: 2336: 2328: 2324: 2319: 2307: 2289: 2253: 2224: 2223: 2199: 2194: 2193: 2172: 2157: 2152: 2151: 2126: 2121: 2120: 2096: 2091: 2090: 2073: 2072: 2062: 2060: 2055: 2045: 2043: 2038: 2033: 2024: 2023: 2017: 2011: 2004: 2003: 1995: 1985: 1983: 1978: 1968: 1966: 1961: 1948: 1947: 1923: 1910: 1897: 1892: 1891: 1866: 1861: 1860: 1858:symmetric group 1836: 1831: 1830: 1824: 1770: 1765: 1764: 1731: 1726: 1725: 1692: 1687: 1686: 1675: 1631: 1603: 1575: 1556: 1531: 1506: 1492: 1491: 1442: 1414: 1386: 1372: 1371: 1332: 1304: 1276: 1268: 1267: 1224: 1223: 1222:-vector spaces 1204: 1203: 1100: 1072: 1064: 1063: 1032: 1031: 1012: 1011: 992: 991: 972: 971: 940: 939: 911: 910: 891: 890: 889:-vector space. 871: 870: 851: 850: 831: 830: 827: 790: 774:diagram chasing 628:, there exists 572: 548: 510: 493: 492: 459: 442: 441: 408: 391: 390: 340: 339: 284: 283: 123: 122: 89:exact sequences 53: 27:, particularly 17: 12: 11: 5: 2557: 2555: 2547: 2546: 2541: 2531: 2530: 2527: 2526: 2517: 2508: 2487: 2486:External links 2484: 2482: 2481: 2475: 2458: 2452: 2432: 2426: 2405: 2402: 2401: 2388:10.1.1.73.1568 2358: 2334: 2321: 2320: 2318: 2315: 2314: 2313: 2306: 2303: 2293:Jill Clayburgh 2288: 2285: 2281: 2280: 2268: 2265: 2260: 2256: 2252: 2249: 2246: 2243: 2240: 2237: 2234: 2231: 2206: 2202: 2179: 2175: 2170: 2164: 2160: 2133: 2129: 2103: 2099: 2087: 2086: 2069: 2065: 2061: 2059: 2056: 2052: 2048: 2044: 2042: 2039: 2037: 2034: 2032: 2029: 2026: 2025: 2022: 2019: 2016: 2013: 2010: 2007: 2005: 2002: 1999: 1996: 1992: 1988: 1984: 1982: 1979: 1975: 1971: 1967: 1965: 1962: 1960: 1957: 1955: 1930: 1926: 1922: 1917: 1913: 1909: 1904: 1900: 1873: 1869: 1843: 1839: 1823: 1822:Counterexample 1820: 1791: 1788: 1785: 1781: 1776: 1773: 1752: 1749: 1746: 1742: 1737: 1734: 1713: 1710: 1707: 1703: 1698: 1695: 1674: 1671: 1658: 1655: 1652: 1647: 1644: 1641: 1638: 1634: 1630: 1627: 1624: 1619: 1616: 1613: 1610: 1606: 1602: 1599: 1596: 1591: 1588: 1585: 1582: 1578: 1574: 1571: 1568: 1563: 1559: 1555: 1552: 1549: 1546: 1543: 1538: 1534: 1530: 1527: 1524: 1521: 1518: 1513: 1509: 1505: 1502: 1499: 1469: 1466: 1463: 1458: 1455: 1452: 1449: 1445: 1441: 1438: 1435: 1430: 1427: 1424: 1421: 1417: 1413: 1410: 1407: 1402: 1399: 1396: 1393: 1389: 1385: 1382: 1379: 1359: 1356: 1353: 1348: 1345: 1342: 1339: 1335: 1331: 1328: 1325: 1320: 1317: 1314: 1311: 1307: 1303: 1300: 1297: 1292: 1289: 1286: 1283: 1279: 1275: 1255: 1252: 1249: 1246: 1243: 1240: 1237: 1234: 1231: 1211: 1200: 1199: 1188: 1185: 1182: 1179: 1176: 1173: 1170: 1167: 1164: 1160: 1156: 1153: 1150: 1147: 1144: 1141: 1137: 1133: 1130: 1127: 1124: 1121: 1116: 1113: 1110: 1107: 1103: 1099: 1096: 1093: 1088: 1085: 1082: 1079: 1075: 1071: 1048: 1045: 1042: 1039: 1019: 999: 979: 959: 956: 953: 950: 947: 927: 924: 921: 918: 898: 878: 858: 838: 826: 823: 822: 821: 809: 808: 789: 786: 571: 568: 560: 559: 547: 544: 531: 528: 525: 521: 516: 513: 509: 506: 503: 500: 480: 477: 474: 470: 465: 462: 458: 455: 452: 449: 429: 426: 423: 419: 414: 411: 407: 404: 401: 398: 375: 372: 369: 361: 353: 350: 347: 319: 316: 313: 305: 297: 294: 291: 261: 260: 249: 246: 243: 235: 227: 224: 221: 213: 205: 202: 199: 191: 188: 180: 177: 174: 166: 158: 155: 152: 144: 136: 133: 130: 85: 84: 71:), consider a 61:abelian groups 52: 49: 15: 13: 10: 9: 6: 4: 3: 2: 2556: 2545: 2542: 2540: 2537: 2536: 2534: 2525: 2521: 2518: 2516: 2512: 2509: 2504: 2503: 2498: 2497:"Snake Lemma" 2495: 2490: 2489: 2485: 2478: 2476:0-387-94823-6 2472: 2468: 2464: 2459: 2455: 2453:0-201-00361-9 2449: 2445: 2441: 2437: 2433: 2429: 2423: 2419: 2415: 2411: 2407: 2406: 2394: 2389: 2384: 2380: 2376: 2369: 2362: 2359: 2348: 2344: 2338: 2335: 2332:, p. 159 2331: 2326: 2323: 2316: 2312: 2311:Zig-zag lemma 2309: 2308: 2304: 2302: 2300: 2299: 2294: 2286: 2284: 2266: 2258: 2254: 2247: 2241: 2235: 2229: 2222: 2221: 2220: 2204: 2200: 2177: 2173: 2168: 2162: 2158: 2149: 2131: 2127: 2117: 2101: 2097: 2067: 2063: 2050: 2046: 2035: 2027: 2000: 1990: 1986: 1973: 1969: 1958: 1946: 1945: 1944: 1928: 1924: 1920: 1915: 1911: 1907: 1902: 1898: 1889: 1888:cyclic groups 1871: 1867: 1859: 1841: 1837: 1829: 1826:Consider the 1821: 1819: 1817: 1813: 1809: 1805: 1789: 1786: 1783: 1779: 1774: 1771: 1750: 1747: 1744: 1740: 1735: 1732: 1711: 1708: 1705: 1701: 1696: 1693: 1684: 1680: 1672: 1670: 1656: 1650: 1642: 1636: 1632: 1628: 1622: 1614: 1608: 1604: 1600: 1594: 1586: 1580: 1576: 1572: 1561: 1557: 1550: 1547: 1536: 1532: 1525: 1522: 1511: 1507: 1500: 1497: 1488: 1486: 1481: 1467: 1461: 1453: 1447: 1443: 1439: 1433: 1425: 1419: 1415: 1411: 1405: 1397: 1391: 1387: 1383: 1377: 1357: 1351: 1343: 1337: 1333: 1329: 1323: 1315: 1309: 1305: 1301: 1295: 1287: 1281: 1277: 1273: 1253: 1247: 1241: 1235: 1229: 1209: 1186: 1180: 1174: 1171: 1168: 1165: 1162: 1158: 1154: 1151: 1142: 1135: 1128: 1122: 1111: 1105: 1101: 1097: 1094: 1091: 1083: 1077: 1073: 1069: 1062: 1061: 1060: 1043: 1037: 1017: 997: 977: 957: 951: 948: 945: 922: 916: 896: 876: 856: 836: 824: 819: 815: 814: 813: 806: 802: 801: 800: 797: 795: 787: 785: 783: 777: 775: 771: 767: 763: 759: 755: 751: 747: 743: 739: 735: 731: 727: 723: 719: 715: 711: 707: 703: 699: 695: 691: 687: 683: 680:) = 0 (since 679: 675: 671: 667: 663: 659: 655: 651: 647: 643: 639: 635: 631: 627: 623: 619: 615: 611: 606: 604: 600: 596: 591: 589: 586: 576: 569: 567: 565: 557: 553: 552: 551: 545: 543: 529: 526: 523: 519: 514: 511: 507: 504: 501: 498: 478: 475: 472: 468: 463: 460: 456: 453: 450: 447: 427: 424: 421: 417: 412: 409: 405: 402: 399: 396: 387: 373: 370: 367: 351: 348: 345: 338:, then so is 337: 333: 317: 314: 311: 295: 292: 289: 281: 277: 272: 270: 266: 247: 244: 241: 225: 222: 219: 203: 200: 197: 189: 178: 175: 172: 156: 153: 150: 134: 131: 128: 121: 120: 119: 117: 113: 109: 105: 101: 96: 94: 91:and 0 is the 90: 82: 78: 77: 76: 74: 70: 67:over a given 66: 65:vector spaces 62: 58: 50: 48: 46: 42: 38: 34: 30: 26: 22: 2524:It's My Turn 2522:in the film 2500: 2462: 2443: 2436:Atiyah, M.F. 2417: 2378: 2374: 2361: 2350:. Retrieved 2346: 2337: 2325: 2298:It's My Turn 2296: 2290: 2282: 2118: 2088: 1825: 1811: 1807: 1803: 1676: 1489: 1482: 1201: 828: 810: 798: 791: 778: 769: 765: 761: 757: 753: 749: 745: 741: 737: 733: 729: 725: 721: 717: 713: 709: 705: 701: 697: 693: 689: 685: 681: 677: 673: 669: 665: 661: 657: 653: 649: 645: 641: 637: 633: 629: 621: 617: 613: 612:in ker  609: 607: 602: 592: 587: 584: 581: 561: 549: 388: 331: 280:monomorphism 275: 273: 268: 264: 262: 115: 111: 107: 97: 86: 54: 44: 20: 18: 2511:Snake Lemma 2410:Lang, Serge 938:-module by 336:epimorphism 93:zero object 25:mathematics 21:snake lemma 2533:Categories 2515:PlanetMath 2352:2021-11-06 2347:GroupNames 2317:References 1683:nine lemma 1679:five lemma 849:be field, 788:Naturality 626:surjective 601:, the map 597:over some 2502:MathWorld 2383:CiteSeerX 2381:: 131–7. 2330:Lang 2002 2264:⟶ 2251:⟶ 2245:⟶ 2239:⟶ 2233:⟶ 2058:→ 2041:→ 2031:→ 2021:↓ 2015:↓ 2009:↓ 1998:→ 1981:→ 1964:→ 1921:⋊ 1908:≃ 1787:⁡ 1748:⁡ 1709:⁡ 1654:→ 1633:⊗ 1626:→ 1605:⊗ 1598:→ 1577:⊗ 1570:→ 1551:⁡ 1545:→ 1526:⁡ 1520:→ 1501:⁡ 1465:→ 1444:⊗ 1437:→ 1416:⊗ 1409:→ 1388:⊗ 1381:→ 1355:→ 1334:⊗ 1327:→ 1306:⊗ 1299:→ 1278:⊗ 1251:→ 1245:→ 1239:→ 1233:→ 1175:⁡ 1102:⊗ 1074:⊗ 955:→ 527:⁡ 502:⁡ 476:⁡ 451:⁡ 425:⁡ 400:⁡ 371:⁡ 360:⟶ 349:⁡ 330:, and if 315:⁡ 304:⟶ 293:⁡ 245:⁡ 234:⟶ 223:⁡ 212:⟶ 201:⁡ 187:⟶ 176:⁡ 165:⟶ 154:⁡ 143:⟶ 132:⁡ 104:cokernels 51:Statement 2442:(1969). 2412:(2002). 2393:Archived 2305:See also 1775:′ 1736:′ 1697:′ 970:being a 712: '( 620:; since 515:′ 464:′ 413:′ 2418:Algebra 1681:or the 825:Example 595:modules 100:kernels 2473:  2450:  2424:  2385:  2148:simple 2119:Since 1810:, and 1763:, and 365:  355:  334:is an 309:  299:  263:where 239:  229:  217:  207:  195:  182:  170:  160:  148:  138:  114:, and 55:In an 2396:(PDF) 2371:(PDF) 1172:coker 1030:over 869:be a 708:with 672:)) = 660:)) = 636:with 564:snake 499:coker 448:coker 397:coker 368:coker 346:coker 278:is a 242:coker 220:coker 198:coker 69:field 2471:ISBN 2448:ISBN 2422:ISBN 1814:are 1010:and 829:Let 740:) = 716:) = 644:) = 599:ring 102:and 19:The 2513:at 2146:is 1548:ker 1523:ker 1498:ker 909:is 799:If 724:). 706:A' 704:in 698:g' 632:in 624:is 312:ker 290:ker 173:ker 151:ker 129:ker 106:of 2535:: 2499:. 2465:. 2438:; 2416:. 2391:. 2377:. 2373:. 2345:. 2301:. 1890:: 1818:. 1806:, 1784:im 1745:im 1724:, 1706:im 1059:. 784:. 746:im 744:+ 650:g' 566:. 542:. 524:im 491:, 473:im 440:, 422:im 386:. 332:g' 271:. 118:: 110:, 95:. 75:: 47:. 2505:. 2479:. 2456:. 2430:. 2379:5 2355:. 2279:, 2267:1 2259:2 2255:C 2248:1 2242:1 2236:1 2230:1 2205:2 2201:C 2178:3 2174:C 2169:/ 2163:3 2159:S 2132:5 2128:A 2102:2 2098:C 2068:5 2064:A 2051:3 2047:S 2036:1 2028:1 2001:1 1991:3 1987:C 1974:3 1970:C 1959:1 1929:2 1925:C 1916:3 1912:C 1903:3 1899:S 1872:3 1868:S 1842:5 1838:A 1812:c 1808:b 1804:a 1790:c 1780:/ 1772:C 1751:b 1741:/ 1733:B 1712:a 1702:/ 1694:A 1657:0 1651:k 1646:] 1643:t 1640:[ 1637:k 1629:P 1623:k 1618:] 1615:t 1612:[ 1609:k 1601:N 1595:k 1590:] 1587:t 1584:[ 1581:k 1573:M 1567:) 1562:P 1558:t 1554:( 1542:) 1537:N 1533:t 1529:( 1517:) 1512:M 1508:t 1504:( 1468:0 1462:k 1457:] 1454:t 1451:[ 1448:k 1440:P 1434:k 1429:] 1426:t 1423:[ 1420:k 1412:N 1406:k 1401:] 1398:t 1395:[ 1392:k 1384:M 1378:0 1358:0 1352:k 1347:] 1344:t 1341:[ 1338:k 1330:P 1324:k 1319:] 1316:t 1313:[ 1310:k 1302:N 1296:k 1291:] 1288:t 1285:[ 1282:k 1274:M 1254:0 1248:P 1242:N 1236:M 1230:0 1210:k 1187:. 1184:) 1181:t 1178:( 1169:= 1166:V 1163:t 1159:/ 1155:V 1152:= 1149:) 1146:) 1143:t 1140:( 1136:/ 1132:] 1129:t 1126:[ 1123:k 1120:( 1115:] 1112:t 1109:[ 1106:k 1098:V 1095:= 1092:k 1087:] 1084:t 1081:[ 1078:k 1070:V 1047:] 1044:t 1041:[ 1038:k 1018:k 998:V 978:k 958:V 952:V 949:: 946:t 926:] 923:t 920:[ 917:k 897:V 877:k 857:V 837:k 770:y 766:x 762:x 760:( 758:d 754:d 750:a 748:( 742:z 738:x 736:( 734:d 730:f 726:z 722:y 720:( 718:b 714:z 710:f 702:z 694:y 692:( 690:b 686:c 682:x 678:x 676:( 674:c 670:y 668:( 666:g 664:( 662:c 658:y 656:( 654:b 652:( 646:x 642:y 640:( 638:g 634:B 630:y 622:g 618:C 614:c 610:x 603:d 588:d 530:c 520:/ 512:C 508:= 505:c 479:b 469:/ 461:B 457:= 454:b 428:a 418:/ 410:A 406:= 403:a 374:c 352:b 318:b 296:a 276:f 265:d 248:c 226:b 204:a 190:d 179:c 157:b 135:a 116:c 112:b 108:a

Index

mathematics
homological algebra
long exact sequences
abelian category
algebraic topology
abelian category
abelian groups
vector spaces
field
commutative diagram

exact sequences
zero object
kernels
cokernels
monomorphism
epimorphism

snake
An animation of the diagram chase to construct the map d by finding d(x) given some x in ker c
modules
ring
surjective
diagram chasing
Mitchell's embedding theorem
natural transformations
commutative diagram with exact rows
commutative diagram with exact rows

five lemma

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