Knowledge

Exact functor

Source πŸ“

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Despite its abstraction, this general definition has useful consequences. For example, in section 1.8, Grothendieck proves that a functor is pro-representable if and only if it is left exact, under some mild conditions on the category
4076: 2424: 197: 3973: 2170: 4283:{\displaystyle :\mathbf {Z} /12\mathbf {Z} \otimes _{Z}P\cong (\mathbf {Z} \otimes _{Z}P)/(12\mathbf {Z} \otimes _{Z}P)=(\mathbf {Z} \otimes _{Z}P)/(3\mathbf {Z} \otimes _{Z}P)\cong \mathbf {Z} P/3\mathbf {Z} P} 2587: 1815: 1538: 57:. Exact functors are convenient for algebraic calculations because they can be directly applied to presentations of objects. Much of the work in homological algebra is designed to cope with functors that 3068: 2604: 2186: 3351: 3552: 216: 2512: 3728: 2929: 1990: 1955: 2983: 3030: 4330: 3343: 3301: 4351:
into colimits; a contravariant functor is left exact iff it turns finite colimits into limits; a contravariant functor is right exact iff it turns finite limits into colimits.
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This article is about exact functors in homological algebra. For exact functors between regular categories, see
4587: 2938: 518: 2988: 4293: 3306: 4648: 4643: 3267: 2874:{\displaystyle R/I\otimes _{R}P\cong (R\otimes _{R}P)/Image(f\otimes P)=(R\otimes _{R}P)/(I\otimes _{R}P)} 1618:. The given tensor products only have pure tensors. Therefore, it suffices to show that if a pure tensor 4602: 1041: 730:β†’0 to have some exactness preserved. The following definitions are equivalent to the ones given above: 4290:. The last congruence follows by a similar argument to one in the proof of the corollary showing that 1893:{\displaystyle 5\mathbf {Z} \hookrightarrow \mathbf {Z} \twoheadrightarrow \mathbf {Z} /5\mathbf {Z} } 1824:
is not flat, then tensor product is not left exact. For example, consider the short exact sequence of
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Left and right exact functors are ubiquitous mainly because of the following fact: if the functor
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While tensoring may not be left exact, it can be shown that tensoring is a right exact functor:
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A covariant (not necessarily additive) functor is left exact if and only if it turns finite
4071:{\displaystyle P=\mathbf {Z} ,A=12\mathbf {Z} ,B=\mathbf {Z} ,C=\mathbf {Z} /12\mathbf {Z} } 4567: 4413:
is left (resp. right) exact if it commutes with finite projective (resp. inductive) limits.
2419:{\displaystyle f\otimes P(a\otimes p):=f(a)\otimes p,g\otimes P(b\otimes p):=g(b)\otimes p} 2173: 1231: 1173: 1165: 203: 54: 1677: 8: 2886: 2439: 1595: 1244: 1188: 1108: 42: 4358:; the degree to which a right exact functor fails to be exact can be measured with its 1726: 1706: 1575: 1219: 78: 4436:
are sometimes called exact functors and generalize the exact functors discussed here.
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The degree to which a left exact functor fails to be exact can be measured with its
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be a category with finite projective (resp. injective) limits. Then a functor from
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modules by the usual multiplication action and satisfy the conditions of the main
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into limits; a covariant functor is right exact if and only if it turns finite
4094:. By the exactness implied by the theorem and by the above note we obtain that 2004: 1256: 192:{\displaystyle 0\to A\ {\stackrel {f}{\to }}\ B\ {\stackrel {g}{\to }}\ C\to 0} 4637: 1441: 1192: 1116: 3968:{\displaystyle (12\mathbf {Z} \otimes _{Z}P)=(3\mathbf {Z} \otimes _{Z}P)} 2165:{\displaystyle A\ {\stackrel {f}{\to }}\ B\ {\stackrel {g}{\to }}\ C\to 0} 718:
It is not always necessary to start with an entire short exact sequence 0β†’
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generalize the exact functors between abelian categories discussed here.
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A functor is exact if and only if it is both left exact and right exact.
1341: 994: 38: 1176:, and any additive functor turns split sequences into split sequences.) 3535: 3261: 3032:. So, the kernel of this map cannot contain any nonzero pure tensors. 1142: 2431: 2582:{\displaystyle I{\stackrel {f}{\to }}R{\stackrel {g}{\to }}R/I\to 0} 1092:) is a contravariant left-exact functor; it is exact if and only if 1168:. Alternatively, one can argue that every short exact sequence of 4545: 4348: 4091: 50: 4514: 347:. (The maps are often omitted and implied, and one says: "if 0β†’ 1810:{\displaystyle M\otimes \mathbb {Q} \to N\otimes \mathbb {Q} } 1533:{\displaystyle M\otimes \mathbb {Q} \to N\otimes \mathbb {Q} } 2313:-modules and not merely of abelian groups). Here, we define 1498:, then the corresponding map between the tensor products 993:
The most basic examples of left exact functors are the
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to be exact, but in ways that can still be controlled.
1199:. The covariant functor that associates to each sheaf 1145:). This yields a contravariant exact functor from the 4296: 4100: 3981: 3907: 3731: 3555: 3495: 3354: 3309: 3270: 3071: 3038: 2991: 2941: 2935:-linearly extending the map defined on pure tensors: 2898: 2734: 2607: 2523: 2456: 2322: 2189: 2102: 1963: 1928: 1906: 1852: 1830: 1781: 1749: 1729: 1709: 1680: 1654: 1624: 1598: 1578: 1546: 1504: 1472: 1450: 1416: 1394: 1372: 1350: 219: 123: 4324: 4282: 4070: 3967: 3893: 3717: 3522: 3481: 3337: 3295: 3252: 3057: 3024: 2977: 2923: 2873: 2716: 2581: 2506: 2418: 2290: 2164: 1984: 1949: 1914: 1892: 1838: 1809: 1767: 1735: 1715: 1695: 1666: 1636: 1610: 1584: 1564: 1532: 1490: 1458: 1424: 1402: 1380: 1358: 517:) is exact. This is distinct from the notion of a 332: 191: 4635: 1957:gives a sequence that is no longer exact, since 2309:is commutative, this sequence is a sequence of 1187:, we can consider the abelian category of all 1153:to itself. (Exactness follows from the above: 1036:) defines a covariant left-exact functor from 4530: 3427: 3386: 2507:{\displaystyle P\otimes _{R}(R/I)\cong P/IP} 27:Functor that preserves short exact sequences 3260:. So, this map is injective. It is clearly 2924:{\displaystyle R\otimes _{R}P\rightarrow P} 2597:is the projection, is an exact sequence of 4537: 4523: 4335: 3348:As another application, we show that for, 1985:{\displaystyle \mathbf {Z} /5\mathbf {Z} } 1950:{\displaystyle \mathbf {Z} /5\mathbf {Z} } 2978:{\displaystyle r\otimes p\mapsto rp.rp=0} 2601:-modules. By the above we get that : 1803: 1789: 1526: 1512: 1452: 1418: 1396: 1374: 1352: 4491: 3025:{\displaystyle 0=rp\otimes 1=r\otimes p} 1992:is not torsion-free and thus not flat. 1300:modules, the sequence of abelian groups 3065:is composed only of pure tensors: For 14: 4636: 4325:{\displaystyle I\otimes _{R}P\cong IP} 3338:{\displaystyle I\otimes _{R}P\cong IP} 4518: 4499:. Vol. 2 (2nd ed.). Dover. 4425:The exact functors between Quillen's 3296:{\displaystyle R\otimes _{R}P\cong P} 4469:Jacobson (2009), p. 99, Theorem 3.1. 4451:Jacobson (2009), p. 98, Theorem 3.1. 2885:is the inclusion. Now, consider the 2096:having multiplicative identity. Let 4460:Jacobson (2009), p. 149, Prop. 3.9. 1674:is an element of the kernel. Then, 1388:-module. Therefore, tensoring with 24: 4388: 2724:is also a short exact sequence of 2301:is also a short exact sequence of 25: 4665: 4544: 1141:) (this is commonly known as the 877:turns cokernels into cokernels"); 4273: 4257: 4233: 4201: 4174: 4142: 4118: 4105: 4064: 4051: 4037: 4023: 3989: 3945: 3915: 3781: 3605: 3472: 3453: 3440: 3423: 3362: 2017:consisting of all functors from 1978: 1965: 1943: 1930: 1908: 1886: 1873: 1865: 1857: 1832: 1648:, then it is zero. Suppose that 1540:is injective. One can show that 990:of abelian categories is exact. 977:turns kernels into cokernels"). 927:turns cokernels into kernels"); 4472: 4463: 4454: 4445: 4250: 4226: 4218: 4197: 4191: 4167: 4159: 4138: 4007: 3993: 3962: 3938: 3932: 3908: 3888: 3861: 3855: 3846: 3840: 3819: 3813: 3804: 3798: 3774: 3768: 3747: 3741: 3732: 3712: 3685: 3679: 3670: 3664: 3643: 3637: 3628: 3622: 3598: 3592: 3571: 3565: 3556: 3549:Proof: Consider a pure tensor 3380: 3366: 3247: 3204: 3192: 3159: 3137: 3111: 3058:{\displaystyle R\otimes _{R}P} 2951: 2915: 2868: 2849: 2841: 2822: 2816: 2804: 2781: 2762: 2708: 2666: 2628: 2573: 2550: 2531: 2484: 2470: 2407: 2401: 2392: 2380: 2359: 2353: 2344: 2332: 2282: 2248: 2210: 2156: 2138: 2113: 1869: 1861: 1793: 1690: 1684: 1516: 1482: 519:topological half-exact functor 324: 321: 315: 302: 296: 288: 278: 272: 259: 253: 245: 235: 229: 223: 183: 165: 140: 127: 64: 13: 1: 4484: 4432:The regular functors between 3345:. This proves the corollary. 1432:-module is an exact functor. 1203:the group of global sections 827:turns kernels into kernels"); 343:is a short exact sequence in 1915:{\displaystyle \mathbf {Z} } 1839:{\displaystyle \mathbf {Z} } 1768:{\displaystyle m\otimes q=0} 1565:{\displaystyle m\otimes q=0} 1459:{\displaystyle \mathbb {Z} } 1436:It suffices to show that if 1425:{\displaystyle \mathbb {Z} } 1403:{\displaystyle \mathbb {Q} } 1381:{\displaystyle \mathbb {Z} } 1359:{\displaystyle \mathbb {Q} } 7: 3542:. We prove a special case: 1999:is an abelian category and 1001:is an abelian category and 981: 10: 4670: 2050:by evaluating functors at 1667:{\displaystyle m\otimes q} 1637:{\displaystyle m\otimes q} 1234:, we can define a functor 29: 4553: 3523:{\displaystyle k=m/2^{n}} 102:(so that, in particular, 4478:Jacobson (2009), p. 156. 4439: 2728:-modules. By exactness, 2033:, then we get a functor 1592:is a torsion element or 1491:{\displaystyle i:M\to N} 1336:is exact if and only if 1057:is exact if and only if 4336:Properties and theorems 1743:is torsion. Therefore, 106:(0) = 0). We say that 4588:Essentially surjective 4356:right derived functors 4326: 4284: 4072: 3969: 3895: 3719: 3524: 3483: 3339: 3297: 3254: 3059: 3026: 2979: 2925: 2875: 2718: 2583: 2508: 2420: 2292: 2166: 2010:, we can consider the 1986: 1951: 1916: 1894: 1840: 1811: 1769: 1737: 1717: 1697: 1668: 1638: 1612: 1586: 1566: 1534: 1492: 1460: 1426: 1404: 1382: 1360: 988:equivalence or duality 541:, we similarly define 533:additive functor from 383:)β†’0 is also exact".) 334: 193: 4360:left derived functors 4327: 4285: 4073: 3970: 3896: 3720: 3525: 3484: 3340: 3298: 3255: 3060: 3027: 2980: 2926: 2876: 2719: 2593:is the inclusion and 2584: 2509: 2421: 2293: 2167: 2029:is a given object of 1987: 1952: 1917: 1895: 1841: 1812: 1770: 1738: 1718: 1698: 1669: 1639: 1613: 1587: 1567: 1535: 1493: 1461: 1427: 1405: 1383: 1361: 1245:category of all left 386:Further, we say that 335: 194: 55:short exact sequences 4409:to another category 4294: 4098: 3979: 3905: 3729: 3553: 3493: 3352: 3307: 3268: 3069: 3036: 2989: 2939: 2896: 2890:-module homomorphism 2732: 2605: 2521: 2454: 2320: 2187: 2174:short exact sequence 2100: 2025:; it is abelian. If 1961: 1926: 1904: 1850: 1828: 1779: 1747: 1727: 1707: 1696:{\displaystyle i(m)} 1678: 1652: 1622: 1596: 1576: 1544: 1502: 1470: 1448: 1414: 1392: 1370: 1348: 973:)β†’0 exact (i.e. if " 873:)β†’0 exact (i.e. if " 359:β†’0 is exact, then 0β†’ 217: 204:short exact sequence 121: 4649:Additive categories 4644:Homological algebra 4381:is right exact and 1817:is also injective. 1611:{\displaystyle q=0} 899:β†’0 exact implies 0β†’ 606:β†’0 is exact then 0β†’ 564:β†’0 is exact then 0β†’ 409:β†’0 is exact then 0β†’ 43:homological algebra 18:Right-exact functor 4434:regular categories 4322: 4280: 4068: 3965: 3901:. This shows that 3891: 3715: 3520: 3479: 3335: 3293: 3250: 3216: 3152: 3100: 3055: 3022: 2975: 2921: 2871: 2714: 2579: 2504: 2450:is as above, then 2430:This has a useful 2416: 2288: 2162: 1982: 1947: 1912: 1890: 1836: 1807: 1765: 1733: 1713: 1703:is torsion. Since 1693: 1664: 1634: 1608: 1582: 1562: 1530: 1488: 1456: 1422: 1400: 1378: 1356: 923:) exact (i.e. if " 823:) exact (i.e. if " 330: 189: 79:abelian categories 4631: 4630: 4603:Full and faithful 4506:978-0-486-47187-7 3207: 3143: 3091: 2681: 2643: 2559: 2540: 2305:-modules. (Since 2263: 2225: 2152: 2147: 2133: 2127: 2122: 2108: 1900:. Tensoring over 1736:{\displaystyle m} 1716:{\displaystyle i} 1585:{\displaystyle m} 1243:from the abelian 1211:) is left-exact. 1185:topological space 1046:of abelian groups 937:if and only if 0β†’ 849:β†’0 exact implies 787:if and only if 0β†’ 690:β†’0 is exact then 648:β†’0 is exact then 493:β†’0 is exact then 451:β†’0 is exact then 311: 306: 283: 268: 263: 240: 179: 174: 160: 154: 149: 135: 16:(Redirected from 4661: 4539: 4532: 4525: 4516: 4515: 4510: 4493:Jacobson, Nathan 4479: 4476: 4470: 4467: 4461: 4458: 4452: 4449: 4427:exact categories 4331: 4329: 4328: 4323: 4309: 4308: 4289: 4287: 4286: 4281: 4276: 4268: 4260: 4246: 4245: 4236: 4225: 4214: 4213: 4204: 4187: 4186: 4177: 4166: 4155: 4154: 4145: 4131: 4130: 4121: 4113: 4108: 4077: 4075: 4074: 4069: 4067: 4059: 4054: 4040: 4026: 4003: 3992: 3974: 3972: 3971: 3966: 3958: 3957: 3948: 3928: 3927: 3918: 3900: 3898: 3897: 3892: 3887: 3886: 3871: 3839: 3838: 3829: 3794: 3793: 3784: 3767: 3766: 3757: 3724: 3722: 3721: 3716: 3711: 3710: 3695: 3663: 3662: 3653: 3618: 3617: 3608: 3591: 3590: 3581: 3529: 3527: 3526: 3521: 3519: 3518: 3509: 3488: 3486: 3485: 3480: 3475: 3467: 3456: 3448: 3443: 3426: 3406: 3405: 3396: 3376: 3365: 3344: 3342: 3341: 3336: 3322: 3321: 3302: 3300: 3299: 3294: 3283: 3282: 3259: 3257: 3256: 3251: 3246: 3245: 3236: 3235: 3226: 3225: 3215: 3191: 3190: 3181: 3180: 3171: 3170: 3151: 3136: 3135: 3123: 3122: 3110: 3109: 3099: 3081: 3080: 3064: 3062: 3061: 3056: 3051: 3050: 3031: 3029: 3028: 3023: 2984: 2982: 2981: 2976: 2930: 2928: 2927: 2922: 2911: 2910: 2880: 2878: 2877: 2872: 2864: 2863: 2848: 2837: 2836: 2788: 2777: 2776: 2755: 2754: 2742: 2723: 2721: 2720: 2715: 2704: 2703: 2691: 2683: 2682: 2680: 2669: 2664: 2658: 2657: 2645: 2644: 2642: 2631: 2626: 2620: 2619: 2588: 2586: 2585: 2580: 2569: 2561: 2560: 2558: 2553: 2548: 2542: 2541: 2539: 2534: 2529: 2513: 2511: 2510: 2505: 2497: 2480: 2469: 2468: 2425: 2423: 2422: 2417: 2297: 2295: 2294: 2289: 2278: 2277: 2265: 2264: 2262: 2251: 2246: 2240: 2239: 2227: 2226: 2224: 2213: 2208: 2202: 2201: 2180:-modules. Then 2171: 2169: 2168: 2163: 2150: 2149: 2148: 2146: 2141: 2136: 2131: 2125: 2124: 2123: 2121: 2116: 2111: 2106: 2091:commutative ring 2012:functor category 2003:is an arbitrary 1991: 1989: 1988: 1983: 1981: 1973: 1968: 1956: 1954: 1953: 1948: 1946: 1938: 1933: 1921: 1919: 1918: 1913: 1911: 1899: 1897: 1896: 1891: 1889: 1881: 1876: 1868: 1860: 1845: 1843: 1842: 1837: 1835: 1816: 1814: 1813: 1808: 1806: 1792: 1774: 1772: 1771: 1766: 1742: 1740: 1739: 1734: 1722: 1720: 1719: 1714: 1702: 1700: 1699: 1694: 1673: 1671: 1670: 1665: 1643: 1641: 1640: 1635: 1617: 1615: 1614: 1609: 1591: 1589: 1588: 1583: 1571: 1569: 1568: 1563: 1539: 1537: 1536: 1531: 1529: 1515: 1497: 1495: 1494: 1489: 1465: 1463: 1462: 1457: 1455: 1431: 1429: 1428: 1423: 1421: 1409: 1407: 1406: 1401: 1399: 1387: 1385: 1384: 1379: 1377: 1365: 1363: 1362: 1357: 1355: 1005:is an object of 799:exact implies 0β†’ 339: 337: 336: 331: 309: 308: 307: 305: 291: 286: 281: 266: 265: 264: 262: 248: 243: 238: 198: 196: 195: 190: 177: 176: 175: 173: 168: 163: 158: 152: 151: 150: 148: 143: 138: 133: 100:additive functor 94: 32:regular category 21: 4669: 4668: 4664: 4663: 4662: 4660: 4659: 4658: 4634: 4633: 4632: 4627: 4549: 4543: 4513: 4507: 4487: 4482: 4477: 4473: 4468: 4464: 4459: 4455: 4450: 4446: 4442: 4391: 4389:Generalizations 4385:is left exact. 4338: 4304: 4300: 4295: 4292: 4291: 4272: 4264: 4256: 4241: 4237: 4232: 4221: 4209: 4205: 4200: 4182: 4178: 4173: 4162: 4150: 4146: 4141: 4126: 4122: 4117: 4109: 4104: 4099: 4096: 4095: 4063: 4055: 4050: 4036: 4022: 3999: 3988: 3980: 3977: 3976: 3953: 3949: 3944: 3923: 3919: 3914: 3906: 3903: 3902: 3876: 3872: 3867: 3834: 3830: 3825: 3789: 3785: 3780: 3762: 3758: 3753: 3730: 3727: 3726: 3700: 3696: 3691: 3658: 3654: 3649: 3613: 3609: 3604: 3586: 3582: 3577: 3554: 3551: 3550: 3534:is the highest 3514: 3510: 3505: 3494: 3491: 3490: 3471: 3463: 3452: 3444: 3439: 3422: 3401: 3397: 3392: 3372: 3361: 3353: 3350: 3349: 3317: 3313: 3308: 3305: 3304: 3278: 3274: 3269: 3266: 3265: 3241: 3237: 3231: 3227: 3221: 3217: 3211: 3186: 3182: 3176: 3172: 3166: 3162: 3147: 3131: 3127: 3118: 3114: 3105: 3101: 3095: 3076: 3072: 3070: 3067: 3066: 3046: 3042: 3037: 3034: 3033: 2990: 2987: 2986: 2940: 2937: 2936: 2906: 2902: 2897: 2894: 2893: 2859: 2855: 2844: 2832: 2828: 2784: 2772: 2768: 2750: 2746: 2738: 2733: 2730: 2729: 2699: 2695: 2687: 2670: 2665: 2663: 2662: 2653: 2649: 2632: 2627: 2625: 2624: 2615: 2611: 2606: 2603: 2602: 2565: 2554: 2549: 2547: 2546: 2535: 2530: 2528: 2527: 2522: 2519: 2518: 2493: 2476: 2464: 2460: 2455: 2452: 2451: 2321: 2318: 2317: 2273: 2269: 2252: 2247: 2245: 2244: 2235: 2231: 2214: 2209: 2207: 2206: 2197: 2193: 2188: 2185: 2184: 2142: 2137: 2135: 2134: 2117: 2112: 2110: 2109: 2101: 2098: 2097: 2089:-modules for a 2062: 2054:. This functor 2041: 1977: 1969: 1964: 1962: 1959: 1958: 1942: 1934: 1929: 1927: 1924: 1923: 1907: 1905: 1902: 1901: 1885: 1877: 1872: 1864: 1856: 1851: 1848: 1847: 1831: 1829: 1826: 1825: 1820:In general, if 1802: 1788: 1780: 1777: 1776: 1748: 1745: 1744: 1728: 1725: 1724: 1708: 1705: 1704: 1679: 1676: 1675: 1653: 1650: 1649: 1623: 1620: 1619: 1597: 1594: 1593: 1577: 1574: 1573: 1572:if and only if 1545: 1542: 1541: 1525: 1511: 1503: 1500: 1499: 1471: 1468: 1467: 1451: 1449: 1446: 1445: 1417: 1415: 1412: 1411: 1395: 1393: 1390: 1389: 1373: 1371: 1368: 1367: 1351: 1349: 1346: 1345: 1344:. For example, 1335: 1324:β†’ 0 is exact. 1271: 1242: 1172:-vector spaces 1132: 1083: 1073: 1056: 1027: 1017: 984: 887:if and only if 837:if and only if 741:if and only if 292: 287: 285: 284: 249: 244: 242: 241: 218: 215: 214: 169: 164: 162: 161: 144: 139: 137: 136: 122: 119: 118: 82: 67: 53:that preserves 41:, particularly 35: 28: 23: 22: 15: 12: 11: 5: 4667: 4657: 4656: 4651: 4646: 4629: 4628: 4626: 4625: 4620: 4615: 4610: 4605: 4600: 4595: 4590: 4585: 4580: 4575: 4570: 4565: 4560: 4554: 4551: 4550: 4542: 4541: 4534: 4527: 4519: 4512: 4511: 4505: 4488: 4486: 4483: 4481: 4480: 4471: 4462: 4453: 4443: 4441: 4438: 4415: 4414: 4390: 4387: 4337: 4334: 4321: 4318: 4315: 4312: 4307: 4303: 4299: 4279: 4275: 4271: 4267: 4263: 4259: 4255: 4252: 4249: 4244: 4240: 4235: 4231: 4228: 4224: 4220: 4217: 4212: 4208: 4203: 4199: 4196: 4193: 4190: 4185: 4181: 4176: 4172: 4169: 4165: 4161: 4158: 4153: 4149: 4144: 4140: 4137: 4134: 4129: 4125: 4120: 4116: 4112: 4107: 4103: 4066: 4062: 4058: 4053: 4049: 4046: 4043: 4039: 4035: 4032: 4029: 4025: 4021: 4018: 4015: 4012: 4009: 4006: 4002: 3998: 3995: 3991: 3987: 3984: 3964: 3961: 3956: 3952: 3947: 3943: 3940: 3937: 3934: 3931: 3926: 3922: 3917: 3913: 3910: 3890: 3885: 3882: 3879: 3875: 3870: 3866: 3863: 3860: 3857: 3854: 3851: 3848: 3845: 3842: 3837: 3833: 3828: 3824: 3821: 3818: 3815: 3812: 3809: 3806: 3803: 3800: 3797: 3792: 3788: 3783: 3779: 3776: 3773: 3770: 3765: 3761: 3756: 3752: 3749: 3746: 3743: 3740: 3737: 3734: 3714: 3709: 3706: 3703: 3699: 3694: 3690: 3687: 3684: 3681: 3678: 3675: 3672: 3669: 3666: 3661: 3657: 3652: 3648: 3645: 3642: 3639: 3636: 3633: 3630: 3627: 3624: 3621: 3616: 3612: 3607: 3603: 3600: 3597: 3594: 3589: 3585: 3580: 3576: 3573: 3570: 3567: 3564: 3561: 3558: 3517: 3513: 3508: 3504: 3501: 3498: 3478: 3474: 3470: 3466: 3462: 3459: 3455: 3451: 3447: 3442: 3438: 3435: 3432: 3429: 3425: 3421: 3418: 3415: 3412: 3409: 3404: 3400: 3395: 3391: 3388: 3385: 3382: 3379: 3375: 3371: 3368: 3364: 3360: 3357: 3334: 3331: 3328: 3325: 3320: 3316: 3312: 3292: 3289: 3286: 3281: 3277: 3273: 3249: 3244: 3240: 3234: 3230: 3224: 3220: 3214: 3210: 3206: 3203: 3200: 3197: 3194: 3189: 3185: 3179: 3175: 3169: 3165: 3161: 3158: 3155: 3150: 3146: 3142: 3139: 3134: 3130: 3126: 3121: 3117: 3113: 3108: 3104: 3098: 3094: 3090: 3087: 3084: 3079: 3075: 3054: 3049: 3045: 3041: 3021: 3018: 3015: 3012: 3009: 3006: 3003: 3000: 2997: 2994: 2974: 2971: 2968: 2965: 2962: 2959: 2956: 2953: 2950: 2947: 2944: 2920: 2917: 2914: 2909: 2905: 2901: 2870: 2867: 2862: 2858: 2854: 2851: 2847: 2843: 2840: 2835: 2831: 2827: 2824: 2821: 2818: 2815: 2812: 2809: 2806: 2803: 2800: 2797: 2794: 2791: 2787: 2783: 2780: 2775: 2771: 2767: 2764: 2761: 2758: 2753: 2749: 2745: 2741: 2737: 2713: 2710: 2707: 2702: 2698: 2694: 2690: 2686: 2679: 2676: 2673: 2668: 2661: 2656: 2652: 2648: 2641: 2638: 2635: 2630: 2623: 2618: 2614: 2610: 2578: 2575: 2572: 2568: 2564: 2557: 2552: 2545: 2538: 2533: 2526: 2503: 2500: 2496: 2492: 2489: 2486: 2483: 2479: 2475: 2472: 2467: 2463: 2459: 2428: 2427: 2415: 2412: 2409: 2406: 2403: 2400: 2397: 2394: 2391: 2388: 2385: 2382: 2379: 2376: 2373: 2370: 2367: 2364: 2361: 2358: 2355: 2352: 2349: 2346: 2343: 2340: 2337: 2334: 2331: 2328: 2325: 2299: 2298: 2287: 2284: 2281: 2276: 2272: 2268: 2261: 2258: 2255: 2250: 2243: 2238: 2234: 2230: 2223: 2220: 2217: 2212: 2205: 2200: 2196: 2192: 2161: 2158: 2155: 2145: 2140: 2130: 2120: 2115: 2105: 2058: 2037: 1980: 1976: 1972: 1967: 1945: 1941: 1937: 1932: 1910: 1888: 1884: 1880: 1875: 1871: 1867: 1863: 1859: 1855: 1834: 1805: 1801: 1798: 1795: 1791: 1787: 1784: 1764: 1761: 1758: 1755: 1752: 1732: 1723:is injective, 1712: 1692: 1689: 1686: 1683: 1663: 1660: 1657: 1633: 1630: 1627: 1607: 1604: 1601: 1581: 1561: 1558: 1555: 1552: 1549: 1528: 1524: 1521: 1518: 1514: 1510: 1507: 1487: 1484: 1481: 1478: 1475: 1454: 1420: 1398: 1376: 1354: 1331: 1267: 1257:tensor product 1238: 1193:abelian groups 1151:-vector spaces 1128: 1127: * = Hom 1079: 1069: 1065:. The functor 1052: 1048:. The functor 1023: 1013: 983: 980: 979: 978: 949:exact implies 928: 878: 828: 778: 753:exact implies 716: 715: 678:if whenever 0β†’ 673: 636:if whenever 0β†’ 631: 594:if whenever 0β†’ 589: 552:if whenever 0β†’ 523: 522: 481:if whenever 0β†’ 476: 439:if whenever 0β†’ 434: 397:if whenever 0β†’ 341: 340: 329: 326: 323: 320: 317: 314: 304: 301: 298: 295: 290: 280: 277: 274: 271: 261: 258: 255: 252: 247: 237: 234: 231: 228: 225: 222: 200: 199: 188: 185: 182: 172: 167: 157: 147: 142: 132: 129: 126: 66: 63: 26: 9: 6: 4: 3: 2: 4666: 4655: 4652: 4650: 4647: 4645: 4642: 4641: 4639: 4624: 4621: 4619: 4618:Representable 4616: 4614: 4611: 4609: 4606: 4604: 4601: 4599: 4596: 4594: 4591: 4589: 4586: 4584: 4581: 4579: 4576: 4574: 4571: 4569: 4566: 4564: 4561: 4559: 4556: 4555: 4552: 4547: 4540: 4535: 4533: 4528: 4526: 4521: 4520: 4517: 4508: 4502: 4498: 4497:Basic algebra 4494: 4490: 4489: 4475: 4466: 4457: 4448: 4444: 4437: 4435: 4430: 4428: 4423: 4421: 4412: 4408: 4404: 4400: 4399: 4398: 4396: 4386: 4384: 4380: 4376: 4372: 4368: 4363: 4361: 4357: 4352: 4350: 4346: 4341: 4333: 4319: 4316: 4313: 4310: 4305: 4301: 4297: 4277: 4269: 4265: 4261: 4253: 4247: 4242: 4238: 4229: 4222: 4215: 4210: 4206: 4194: 4188: 4183: 4179: 4170: 4163: 4156: 4151: 4147: 4135: 4132: 4127: 4123: 4114: 4110: 4101: 4093: 4089: 4085: 4081: 4060: 4056: 4047: 4044: 4041: 4033: 4030: 4027: 4019: 4016: 4013: 4010: 4004: 4000: 3996: 3985: 3982: 3959: 3954: 3950: 3941: 3935: 3929: 3924: 3920: 3911: 3883: 3880: 3877: 3873: 3868: 3864: 3858: 3852: 3849: 3843: 3835: 3831: 3826: 3822: 3816: 3810: 3807: 3801: 3795: 3790: 3786: 3777: 3771: 3763: 3759: 3754: 3750: 3744: 3738: 3735: 3707: 3704: 3701: 3697: 3692: 3688: 3682: 3676: 3673: 3667: 3659: 3655: 3650: 3646: 3640: 3634: 3631: 3625: 3619: 3614: 3610: 3601: 3595: 3587: 3583: 3578: 3574: 3568: 3562: 3559: 3547: 3545: 3541: 3537: 3533: 3515: 3511: 3506: 3502: 3499: 3496: 3476: 3468: 3464: 3460: 3457: 3449: 3445: 3436: 3433: 3430: 3419: 3416: 3413: 3410: 3407: 3402: 3398: 3393: 3389: 3383: 3377: 3373: 3369: 3358: 3355: 3346: 3332: 3329: 3326: 3323: 3318: 3314: 3310: 3303:. Similarly, 3290: 3287: 3284: 3279: 3275: 3271: 3263: 3242: 3238: 3232: 3228: 3222: 3218: 3212: 3208: 3201: 3198: 3195: 3187: 3183: 3177: 3173: 3167: 3163: 3156: 3153: 3148: 3144: 3140: 3132: 3128: 3124: 3119: 3115: 3106: 3102: 3096: 3092: 3088: 3085: 3082: 3077: 3073: 3052: 3047: 3043: 3039: 3019: 3016: 3013: 3010: 3007: 3004: 3001: 2998: 2995: 2992: 2985:implies that 2972: 2969: 2966: 2963: 2960: 2957: 2954: 2948: 2945: 2942: 2934: 2918: 2912: 2907: 2903: 2899: 2891: 2889: 2884: 2865: 2860: 2856: 2852: 2845: 2838: 2833: 2829: 2825: 2819: 2813: 2810: 2807: 2801: 2798: 2795: 2792: 2789: 2785: 2778: 2773: 2769: 2765: 2759: 2756: 2751: 2747: 2743: 2739: 2735: 2727: 2711: 2705: 2700: 2696: 2692: 2688: 2684: 2677: 2674: 2671: 2659: 2654: 2650: 2646: 2639: 2636: 2633: 2621: 2616: 2612: 2608: 2600: 2596: 2592: 2576: 2570: 2566: 2562: 2555: 2543: 2536: 2524: 2515: 2501: 2498: 2494: 2490: 2487: 2481: 2477: 2473: 2465: 2461: 2457: 2449: 2445: 2441: 2437: 2433: 2413: 2410: 2404: 2398: 2395: 2389: 2386: 2383: 2377: 2374: 2371: 2368: 2365: 2362: 2356: 2350: 2347: 2341: 2338: 2335: 2329: 2326: 2323: 2316: 2315: 2314: 2312: 2308: 2304: 2285: 2279: 2274: 2270: 2266: 2259: 2256: 2253: 2241: 2236: 2232: 2228: 2221: 2218: 2215: 2203: 2198: 2194: 2190: 2183: 2182: 2181: 2179: 2175: 2159: 2153: 2143: 2128: 2118: 2103: 2095: 2092: 2088: 2084: 2080: 2076: 2072: 2069:Theorem: Let 2067: 2064: 2061: 2057: 2053: 2049: 2045: 2040: 2036: 2032: 2028: 2024: 2020: 2016: 2013: 2009: 2006: 2002: 1998: 1993: 1974: 1970: 1939: 1935: 1882: 1878: 1853: 1823: 1818: 1799: 1796: 1785: 1782: 1775:. Therefore, 1762: 1759: 1756: 1753: 1750: 1730: 1710: 1687: 1681: 1661: 1658: 1655: 1647: 1631: 1628: 1625: 1605: 1602: 1599: 1579: 1559: 1556: 1553: 1550: 1547: 1522: 1519: 1508: 1505: 1485: 1479: 1476: 1473: 1443: 1442:injective map 1439: 1435: 1343: 1339: 1334: 1330: 1325: 1323: 1319: 1315: 1311: 1307: 1303: 1299: 1295: 1291: 1287: 1283: 1279: 1275: 1270: 1266: 1262: 1258: 1255:by using the 1254: 1250: 1248: 1241: 1237: 1233: 1229: 1225: 1221: 1217: 1212: 1210: 1206: 1202: 1198: 1194: 1190: 1186: 1182: 1177: 1175: 1171: 1167: 1163: 1160: 1156: 1152: 1150: 1144: 1140: 1136: 1131: 1126: 1122: 1118: 1114: 1110: 1106: 1101: 1099: 1095: 1091: 1087: 1082: 1077: 1072: 1068: 1064: 1060: 1055: 1051: 1047: 1045: 1039: 1035: 1031: 1026: 1021: 1016: 1012: 1008: 1004: 1000: 996: 991: 989: 976: 972: 968: 964: 960: 956: 952: 948: 944: 940: 936: 932: 929: 926: 922: 918: 914: 910: 906: 902: 898: 894: 890: 886: 882: 879: 876: 872: 868: 864: 860: 856: 852: 848: 844: 840: 836: 832: 829: 826: 822: 818: 814: 810: 806: 802: 798: 794: 790: 786: 782: 779: 776: 772: 768: 764: 760: 756: 752: 748: 744: 740: 736: 733: 732: 731: 729: 725: 721: 713: 709: 705: 701: 697: 693: 689: 685: 681: 677: 674: 672:)β†’0 is exact; 671: 667: 663: 659: 655: 651: 647: 643: 639: 635: 632: 629: 625: 621: 617: 613: 609: 605: 601: 597: 593: 590: 588:)β†’0 is exact; 587: 583: 579: 575: 571: 567: 563: 559: 555: 551: 548: 547: 546: 544: 540: 536: 532: 531:contravariant 528: 520: 516: 512: 508: 504: 500: 496: 492: 488: 484: 480: 477: 475:)β†’0 is exact; 474: 470: 466: 462: 458: 454: 450: 446: 442: 438: 435: 432: 428: 424: 420: 416: 412: 408: 404: 400: 396: 393: 392: 391: 389: 384: 382: 378: 374: 370: 366: 362: 358: 354: 350: 346: 327: 318: 312: 299: 293: 275: 269: 256: 250: 232: 226: 220: 213: 212: 211: 209: 205: 186: 180: 170: 155: 145: 130: 124: 117: 116: 115: 114:if whenever 113: 112:exact functor 109: 105: 101: 98: 93: 89: 85: 80: 76: 72: 62: 60: 56: 52: 48: 47:exact functor 44: 40: 33: 19: 4592: 4568:Conservative 4496: 4474: 4465: 4456: 4447: 4431: 4424: 4419: 4416: 4410: 4406: 4402: 4392: 4382: 4378: 4374: 4371:left adjoint 4366: 4364: 4353: 4342: 4339: 4087: 4083: 4079: 3725:. Also, for 3548: 3543: 3539: 3531: 3347: 2932: 2887: 2882: 2725: 2598: 2594: 2590: 2516: 2447: 2443: 2435: 2429: 2310: 2306: 2302: 2300: 2177: 2093: 2086: 2082: 2078: 2074: 2070: 2068: 2065: 2059: 2055: 2051: 2047: 2043: 2038: 2034: 2030: 2026: 2022: 2018: 2014: 2000: 1996: 1994: 1821: 1819: 1437: 1433: 1337: 1332: 1328: 1327:The functor 1326: 1321: 1317: 1313: 1309: 1305: 1301: 1297: 1293: 1289: 1285: 1281: 1277: 1273: 1268: 1264: 1260: 1252: 1246: 1239: 1235: 1227: 1223: 1215: 1213: 1208: 1204: 1200: 1196: 1180: 1178: 1169: 1161: 1154: 1148: 1147:category of 1138: 1134: 1129: 1124: 1120: 1117:vector space 1112: 1104: 1102: 1093: 1089: 1085: 1080: 1075: 1070: 1066: 1058: 1053: 1049: 1043: 1037: 1033: 1029: 1024: 1019: 1014: 1010: 1006: 1002: 998: 995:Hom functors 992: 985: 974: 970: 966: 962: 958: 954: 950: 946: 942: 938: 934: 930: 924: 920: 916: 912: 908: 904: 900: 896: 892: 888: 884: 880: 874: 870: 866: 862: 858: 854: 850: 846: 842: 838: 834: 830: 824: 820: 816: 812: 808: 804: 800: 796: 792: 788: 784: 780: 774: 770: 766: 762: 758: 754: 750: 746: 742: 738: 734: 727: 723: 719: 717: 711: 707: 703: 699: 695: 691: 687: 683: 679: 675: 669: 665: 661: 657: 653: 649: 645: 641: 637: 633: 627: 623: 619: 615: 611: 607: 603: 599: 595: 591: 585: 581: 577: 573: 569: 565: 561: 557: 553: 549: 542: 538: 534: 526: 524: 514: 510: 506: 502: 498: 494: 490: 486: 482: 478: 472: 468: 464: 460: 456: 452: 448: 444: 440: 436: 430: 426: 422: 418: 414: 410: 406: 402: 398: 394: 387: 385: 380: 376: 372: 368: 364: 360: 356: 352: 348: 344: 342: 207: 201: 111: 107: 103: 91: 87: 83: 74: 70: 68: 58: 46: 36: 1296:β†’0 of left 1226:is a right 1123:, we write 935:right-exact 835:right-exact 714:) is exact. 634:right-exact 630:) is exact; 437:right-exact 433:) is exact; 65:Definitions 39:mathematics 4638:Categories 4485:References 3975:. Letting 3536:power of 2 2063:is exact. 1644:is in the 1366:is a flat 1143:dual space 1063:projective 885:left-exact 785:left-exact 676:half-exact 592:left-exact 479:half-exact 395:left-exact 81:, and let 4598:Forgetful 4314:≅ 4302:⊗ 4254:≅ 4239:⊗ 4207:⊗ 4180:⊗ 4148:⊗ 4136:≅ 4124:⊗ 3951:⊗ 3921:⊗ 3859:⊗ 3817:⊗ 3787:⊗ 3772:∈ 3745:⊗ 3705:− 3683:⊗ 3641:⊗ 3611:⊗ 3596:∈ 3569:⊗ 3538:dividing 3458:≅ 3437:⊗ 3420:∈ 3327:≅ 3315:⊗ 3288:≅ 3276:⊗ 3209:∑ 3202:⊗ 3157:⊗ 3145:∑ 3125:⊗ 3093:∑ 3083:∈ 3044:⊗ 3017:⊗ 3005:⊗ 2952:↦ 2946:⊗ 2931:given by 2916:→ 2904:⊗ 2857:⊗ 2830:⊗ 2811:⊗ 2770:⊗ 2760:≅ 2748:⊗ 2709:→ 2697:⊗ 2675:⊗ 2667:→ 2651:⊗ 2637:⊗ 2629:→ 2613:⊗ 2574:→ 2551:→ 2532:→ 2488:≅ 2462:⊗ 2432:corollary 2411:⊗ 2387:⊗ 2375:⊗ 2363:⊗ 2339:⊗ 2327:⊗ 2283:→ 2271:⊗ 2257:⊗ 2249:→ 2233:⊗ 2219:⊗ 2211:→ 2195:⊗ 2157:→ 2139:→ 2114:→ 1870:↠ 1862:↪ 1846:-modules 1800:⊗ 1794:→ 1786:⊗ 1754:⊗ 1659:⊗ 1629:⊗ 1551:⊗ 1523:⊗ 1517:→ 1509:⊗ 1483:→ 1466:-modules 1159:injective 1098:injective 1042:category 325:→ 289:⟶ 246:⟶ 224:→ 184:→ 166:→ 141:→ 128:→ 97:covariant 4654:Functors 4613:Monoidal 4583:Enriched 4578:Diagonal 4558:Additive 4495:(2009). 4411:C′ 4349:colimits 2881:, since 2589:, where 2008:category 1249:-modules 982:Examples 777:) exact; 4608:Logical 4573:Derived 4563:Adjoint 4546:Functor 4377:, then 4092:theorem 4080:A,B,C,P 2517:Proof: 1189:sheaves 1078:) = Hom 1040:to the 1022:) = Hom 1009:, then 51:functor 4623:Smooth 4503:  4345:limits 3489:where 3264:. So, 2438:is an 2151:  2132:  2126:  2107:  1646:kernel 1440:is an 1434:Proof: 1232:module 1174:splits 1166:module 1157:is an 986:Every 545:to be 390:is 310:  282:  267:  239:  210:then 178:  159:  153:  134:  110:is an 4593:Exact 4548:types 4440:Notes 3546:=12. 2892:from 2440:ideal 2434:: If 2172:be a 2042:from 2005:small 1922:with 1410:as a 1259:over 1218:is a 1183:is a 1119:over 1115:is a 1109:field 1107:is a 997:: if 739:exact 550:exact 529:is a 202:is a 95:be a 49:is a 45:, an 4501:ISBN 4401:Let 4395:SGA4 4082:are 3530:and 3262:onto 2446:and 2176:of 2081:and 1342:flat 1276:) = 1222:and 1220:ring 1111:and 73:and 69:Let 59:fail 4393:In 4373:to 4369:is 4078:, 2442:of 2085:be 2046:to 2021:to 1995:If 1444:of 1340:is 1251:to 1214:If 1195:on 1191:of 1179:If 1103:If 1096:is 1061:is 933:is 883:is 833:is 783:is 737:is 537:to 525:If 206:in 77:be 37:In 4640:: 4422:. 4362:. 4332:. 4171:12 4115:12 4061:12 4020:12 3912:12 3850:12 3632:12 3602:12 3560:12 3384::= 2514:. 2396::= 2348::= 1320:βŠ— 1316:β†’ 1312:βŠ— 1308:β†’ 1304:βŠ— 1280:βŠ— 1263:: 1253:Ab 1100:. 1044:Ab 965:)β†’ 957:)β†’ 915:)β†’ 907:)β†’ 865:)β†’ 857:)β†’ 815:)β†’ 807:)β†’ 769:)β†’ 761:)β†’ 706:)β†’ 698:)β†’ 664:)β†’ 656:)β†’ 622:)β†’ 614:)β†’ 580:)β†’ 572:)β†’ 509:)β†’ 501:)β†’ 467:)β†’ 459:)β†’ 425:)β†’ 417:)β†’ 375:)β†’ 367:)β†’ 86:: 4538:e 4531:t 4524:v 4509:. 4420:C 4407:C 4403:C 4383:G 4379:F 4375:G 4367:F 4320:P 4317:I 4311:P 4306:R 4298:I 4278:P 4274:Z 4270:3 4266:/ 4262:P 4258:Z 4251:) 4248:P 4243:Z 4234:Z 4230:3 4227:( 4223:/ 4219:) 4216:P 4211:Z 4202:Z 4198:( 4195:= 4192:) 4189:P 4184:Z 4175:Z 4168:( 4164:/ 4160:) 4157:P 4152:Z 4143:Z 4139:( 4133:P 4128:Z 4119:Z 4111:/ 4106:Z 4102:: 4088:Z 4086:= 4084:R 4065:Z 4057:/ 4052:Z 4048:= 4045:C 4042:, 4038:Z 4034:= 4031:B 4028:, 4024:Z 4017:= 4014:A 4011:, 4008:] 4005:2 4001:/ 3997:1 3994:[ 3990:Z 3986:= 3983:P 3963:) 3960:P 3955:Z 3946:Z 3942:3 3939:( 3936:= 3933:) 3930:P 3925:Z 3916:Z 3909:( 3889:) 3884:2 3881:+ 3878:k 3874:2 3869:/ 3865:a 3862:( 3856:) 3853:z 3847:( 3844:= 3841:) 3836:k 3832:2 3827:/ 3823:a 3820:( 3814:) 3811:z 3808:3 3805:( 3802:, 3799:) 3796:P 3791:Z 3782:Z 3778:3 3775:( 3769:) 3764:k 3760:2 3755:/ 3751:a 3748:( 3742:) 3739:z 3736:3 3733:( 3713:) 3708:2 3702:k 3698:2 3693:/ 3689:a 3686:( 3680:) 3677:z 3674:3 3671:( 3668:= 3665:) 3660:k 3656:2 3651:/ 3647:a 3644:( 3638:) 3635:z 3629:( 3626:. 3623:) 3620:P 3615:Z 3606:Z 3599:( 3593:) 3588:k 3584:2 3579:/ 3575:a 3572:( 3566:) 3563:z 3557:( 3544:m 3540:m 3532:n 3516:n 3512:2 3507:/ 3503:m 3500:= 3497:k 3477:P 3473:Z 3469:k 3465:/ 3461:P 3454:Z 3450:m 3446:/ 3441:Z 3434:P 3431:, 3428:} 3424:Z 3417:k 3414:, 3411:a 3408:: 3403:k 3399:2 3394:/ 3390:a 3387:{ 3381:] 3378:2 3374:/ 3370:1 3367:[ 3363:Z 3359:= 3356:P 3333:P 3330:I 3324:P 3319:R 3311:I 3291:P 3285:P 3280:R 3272:R 3248:) 3243:i 3239:p 3233:i 3229:x 3223:i 3219:r 3213:i 3205:( 3199:1 3196:= 3193:) 3188:i 3184:p 3178:i 3174:x 3168:i 3164:r 3160:( 3154:1 3149:i 3141:= 3138:) 3133:i 3129:p 3120:i 3116:r 3112:( 3107:i 3103:x 3097:i 3089:, 3086:R 3078:i 3074:x 3053:P 3048:R 3040:R 3020:p 3014:r 3011:= 3008:1 3002:p 2999:r 2996:= 2993:0 2973:0 2970:= 2967:p 2964:r 2961:. 2958:p 2955:r 2949:p 2943:r 2933:R 2919:P 2913:P 2908:R 2900:R 2888:R 2883:f 2869:) 2866:P 2861:R 2853:I 2850:( 2846:/ 2842:) 2839:P 2834:R 2826:R 2823:( 2820:= 2817:) 2814:P 2808:f 2805:( 2802:e 2799:g 2796:a 2793:m 2790:I 2786:/ 2782:) 2779:P 2774:R 2766:R 2763:( 2757:P 2752:R 2744:I 2740:/ 2736:R 2726:R 2712:0 2706:P 2701:R 2693:I 2689:/ 2685:R 2678:P 2672:g 2660:P 2655:R 2647:R 2640:P 2634:f 2622:P 2617:R 2609:I 2599:R 2595:g 2591:f 2577:0 2571:I 2567:/ 2563:R 2556:g 2544:R 2537:f 2525:I 2502:P 2499:I 2495:/ 2491:P 2485:) 2482:I 2478:/ 2474:R 2471:( 2466:R 2458:P 2448:P 2444:R 2436:I 2426:. 2414:p 2408:) 2405:b 2402:( 2399:g 2393:) 2390:p 2384:b 2381:( 2378:P 2372:g 2369:, 2366:p 2360:) 2357:a 2354:( 2351:f 2345:) 2342:p 2336:a 2333:( 2330:P 2324:f 2311:R 2307:R 2303:R 2286:0 2280:P 2275:R 2267:C 2260:P 2254:g 2242:P 2237:R 2229:B 2222:P 2216:f 2204:P 2199:R 2191:A 2178:R 2160:0 2154:C 2144:g 2129:B 2119:f 2104:A 2094:R 2087:R 2083:P 2079:C 2077:, 2075:B 2073:, 2071:A 2060:X 2056:E 2052:X 2048:A 2044:A 2039:X 2035:E 2031:C 2027:X 2023:A 2019:C 2015:A 2001:C 1997:A 1979:Z 1975:5 1971:/ 1966:Z 1944:Z 1940:5 1936:/ 1931:Z 1909:Z 1887:Z 1883:5 1879:/ 1874:Z 1866:Z 1858:Z 1854:5 1833:Z 1822:T 1804:Q 1797:N 1790:Q 1783:M 1763:0 1760:= 1757:q 1751:m 1731:m 1711:i 1691:) 1688:m 1685:( 1682:i 1662:q 1656:m 1632:q 1626:m 1606:0 1603:= 1600:q 1580:m 1560:0 1557:= 1554:q 1548:m 1527:Q 1520:N 1513:Q 1506:M 1486:N 1480:M 1477:: 1474:i 1453:Z 1438:i 1419:Z 1397:Q 1375:Z 1353:Q 1338:T 1333:T 1329:H 1322:C 1318:T 1314:B 1310:T 1306:A 1302:T 1298:R 1294:C 1292:β†’ 1290:B 1288:β†’ 1286:A 1282:X 1278:T 1274:X 1272:( 1269:T 1265:H 1261:R 1247:R 1240:T 1236:H 1230:- 1228:R 1224:T 1216:R 1209:X 1207:( 1205:F 1201:F 1197:X 1181:X 1170:k 1164:- 1162:k 1155:k 1149:k 1139:k 1137:, 1135:V 1133:( 1130:k 1125:V 1121:k 1113:V 1105:k 1094:A 1090:A 1088:, 1086:X 1084:( 1081:A 1076:X 1074:( 1071:A 1067:G 1059:A 1054:A 1050:F 1038:A 1034:X 1032:, 1030:A 1028:( 1025:A 1020:X 1018:( 1015:A 1011:F 1007:A 1003:A 999:A 975:G 971:A 969:( 967:G 963:B 961:( 959:G 955:C 953:( 951:G 947:C 945:β†’ 943:B 941:β†’ 939:A 931:G 925:G 921:A 919:( 917:G 913:B 911:( 909:G 905:C 903:( 901:G 897:C 895:β†’ 893:B 891:β†’ 889:A 881:G 875:F 871:C 869:( 867:F 863:B 861:( 859:F 855:A 853:( 851:F 847:C 845:β†’ 843:B 841:β†’ 839:A 831:F 825:F 821:C 819:( 817:F 813:B 811:( 809:F 805:A 803:( 801:F 797:C 795:β†’ 793:B 791:β†’ 789:A 781:F 775:C 773:( 771:F 767:B 765:( 763:F 759:A 757:( 755:F 751:C 749:β†’ 747:B 745:β†’ 743:A 735:F 728:C 726:β†’ 724:B 722:β†’ 720:A 712:A 710:( 708:G 704:B 702:( 700:G 696:C 694:( 692:G 688:C 686:β†’ 684:B 682:β†’ 680:A 670:A 668:( 666:G 662:B 660:( 658:G 654:C 652:( 650:G 646:C 644:β†’ 642:B 640:β†’ 638:A 628:A 626:( 624:G 620:B 618:( 616:G 612:C 610:( 608:G 604:C 602:β†’ 600:B 598:β†’ 596:A 586:A 584:( 582:G 578:B 576:( 574:G 570:C 568:( 566:G 562:C 560:β†’ 558:B 556:β†’ 554:A 543:G 539:Q 535:P 527:G 521:. 515:C 513:( 511:F 507:B 505:( 503:F 499:A 497:( 495:F 491:C 489:β†’ 487:B 485:β†’ 483:A 473:C 471:( 469:F 465:B 463:( 461:F 457:A 455:( 453:F 449:C 447:β†’ 445:B 443:β†’ 441:A 431:C 429:( 427:F 423:B 421:( 419:F 415:A 413:( 411:F 407:C 405:β†’ 403:B 401:β†’ 399:A 388:F 381:C 379:( 377:F 373:B 371:( 369:F 365:A 363:( 361:F 357:C 355:β†’ 353:B 351:β†’ 349:A 345:Q 328:0 322:) 319:C 316:( 313:F 303:) 300:g 297:( 294:F 279:) 276:B 273:( 270:F 260:) 257:f 254:( 251:F 236:) 233:A 230:( 227:F 221:0 208:P 187:0 181:C 171:g 156:B 146:f 131:A 125:0 108:F 104:F 92:Q 90:β†’ 88:P 84:F 75:Q 71:P 34:. 20:)

Index

Right-exact functor
regular category
mathematics
homological algebra
functor
short exact sequences
abelian categories
covariant
additive functor
short exact sequence
topological half-exact functor
contravariant
equivalence or duality
Hom functors
category Ab of abelian groups
projective
injective
field
vector space
dual space
category of k-vector spaces
injective
module
splits
topological space
sheaves
abelian groups
ring
module
category of all left R-modules

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