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Stalk (sheaf)

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33: 1127: 2373:, respectively, if and only if the induced morphisms on all stalks have the same property. (However it is not true that two sheaves, all of whose stalks are isomorphic, are isomorphic, too, because there may be no map between the sheaves in question.) 1833:, because the latter function is not identically one on any neighborhood of the origin. This example shows that germs contain more information than the power series expansion of a function, because the power series of 964: 453: 2678: 1505:, we find that the germ at a point determines the function on any connected open set where the function can be everywhere defined. (This does not imply that all the restriction maps of this sheaf are injective!) 2754: 1211: 2556: 2467: 1555: 588: 1439: 1947: 858: 2232:. This idea makes more sense if one adopts the common visualisation of functions mapping from some space above to a space below; with this visualisation, any function that maps 817: 371: 1306: 1379: 2580: 2515: 2491: 2423: 1975: 1882: 1831: 320: 293: 269: 536: 930: 1561:
that is identically one in a neighborhood of the origin and identically zero far away from the origin. On any sufficiently small neighborhood containing the origin,
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As outlined in the introduction, stalks capture the local behaviour of a sheaf. As a sheaf is supposed to be determined by its local restrictions (see
1122:{\displaystyle i^{-1}{\mathcal {F}}(\{x\})=\varinjlim _{U\supseteq \{x\}}{\mathcal {F}}(U)=\varinjlim _{U\ni x}{\mathcal {F}}(U)={\mathcal {F}}_{x}.} 379: 1625:
is a bump function, the germ does not tell us how large its bump is. From what the germ tells us, the bump could be infinitely wide, that is,
1497:, a germ of a function at a point determines the function in a small neighborhood of a point. This is because the germ records the function's 2588: 1884:
is identically one. (This extra information is related to the fact that the stalk of the sheaf of smooth functions at the origin is a non-
2875: 225:. Conceptually speaking, we do this by looking at small neighborhoods of the point. If we look at a sufficiently small neighborhood of 2683: 1581:
is identically one, so at the origin it has the same germ as the constant function with value 1. Suppose that we want to reconstruct
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the direct limit used to define the stalk may not exist. However, it exists for most categories that occur in practice, such as the
2815: 2786: 116: 1521:, germs contain some local information, but are not enough to reconstruct the function on any open neighborhood. For example, let 2357:), it can be expected that the stalks capture a fair amount of the information that the sheaf is encoding. This is indeed true: 2871: 1166: 54: 50: 1782:
On the other hand, germs of smooth functions can distinguish between the constant function with value one and the function
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A sheaf is zero (if we are dealing with sheafs of groups), if and only if all stalks of the sheaf vanish. Therefore, the
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at that point. Of course, no single neighborhood will be small enough, so we will have to take a limit of some sort.
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consists of points. It is reasonable to attempt to isolate the behavior of a sheaf at a single fixed point
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can be tested on the stalks, which is often easier as one can pass to smaller and smaller neighbourhoods.
1312:, that is, its equivalence class in the direct limit. This is a generalization of the usual concept of a 2895: 1502: 820: 791: 345: 65: 1278: 1357: 2342: 1950: 2561: 2496: 2472: 2404: 1956: 1836: 1785: 1501:
expansion, and all analytic functions are by definition locally equal to their power series. Using
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There is another approach to defining a stalk that is useful in some contexts. Choose a point
2811: 2782: 1494: 1490: 645: 157: 489: 2803: 2774: 2583: 2235: 2102: 1145: 2069: 935: 889: 863: 745: 620: 593: 1885: 1518: 1514: 1316:, which can be recovered by looking at the stalks of the sheaf of continuous functions on 2878:)Spring 2009. Massachusetts Institute of Technology: MIT OpenCourseWare Creative Commons 90: 2426: 2301: 2281: 2261: 2211: 2191: 2171: 2151: 2131: 2111: 2046: 2022: 2001: 1981: 1761: 1739: 1717: 1695: 1673: 1651: 1629: 1607: 1585: 1564: 1464: 1444: 1384: 1352: 1320: 1258: 1237: 1216: 771: 725: 705: 685: 656: 466: 325: 229: 207: 185: 163: 2889: 2382: 1901: 1558: 1149: 2370: 2354: 1498: 544:) of the direct limit, an element of the stalk is an equivalence class of elements 459: 17: 2860: 2366: 2362: 2041: 141: 32: 2778: 2229: 2106: 1157: 2807: 2680:(because the sheafification functor is left adjoint to the inclusion functor 2851: 2842: 1647:
could equal the constant function with value 1. We cannot even reconstruct
448:{\displaystyle {\mathcal {F}}_{x}:=\varinjlim _{U\ni x}{\mathcal {F}}(U).} 2879: 2394: 2319: 153: 2673:{\displaystyle (-)^{+}:\mathbf {Set} ^{{\mathcal {O}}(X)^{op}}\to Sh(X)} 2386: 2339: 2831: 144:
construction capturing the behaviour of a sheaf around a given point.
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space is closed. This feature is the basis of the construction of
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containing the origin, because we cannot tell whether the bump of
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on that small neighborhood should be the same as the behavior of
2835: 2749:{\displaystyle Sh(X)\to \mathbf {Set} ^{{\mathcal {O}}(X)^{op}}} 2397:. However, stalks of sheaves and presheaves are tightly linked: 26: 2720: 2626: 2567: 2537: 2526: 2502: 2478: 2448: 2437: 2410: 1962: 1284: 1192: 1172: 1105: 1085: 1040: 983: 845: 798: 566: 428: 386: 352: 307: 280: 256: 860:. Notice that the only open sets of the one point space 648:
if the restrictions of the two sections coincide on some
1206:{\displaystyle {\mathcal {F}}(U)\to {\mathcal {F}}_{x}} 2686: 2591: 2564: 2523: 2499: 2475: 2434: 2407: 2304: 2284: 2264: 2238: 2214: 2194: 2174: 2154: 2134: 2114: 2072: 2049: 2025: 2004: 1984: 1959: 1909: 1892:
says that this cannot happen for a Noetherian ring.)
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Unsourced material may be challenged and removed. 2748: 2672: 2574: 2550: 2509: 2485: 2461: 2417: 2310: 2290: 2270: 2250: 2220: 2200: 2180: 2160: 2140: 2120: 2085: 2055: 2031: 2010: 1990: 1969: 1941: 1876: 1825: 1770: 1748: 1726: 1704: 1682: 1660: 1638: 1616: 1594: 1573: 1549: 1473: 1453: 1433: 1393: 1373: 1329: 1300: 1267: 1246: 1225: 1205: 1121: 950: 924: 904: 878: 852: 811: 780: 760: 734: 714: 694: 665: 636: 609: 582: 530: 504: 475: 447: 365: 334: 314: 287: 263: 238: 216: 194: 172: 2551:{\displaystyle {\mathcal {F}}={\mathcal {P}}^{+}} 2517:agree. This follows from the fact that the sheaf 2462:{\displaystyle {\mathcal {F}}={\mathcal {P}}^{+}} 932:, and there is no data over the empty set. Over 1603:from its germ. Even if we know in advance that 1148:or most categories of algebraic objects such as 1550:{\displaystyle f:\mathbb {R} \to \mathbb {R} } 1401:, (or group, ring, etc) is a sheaf for which 462:is indexed over all the open sets containing 8: 1030: 1024: 997: 991: 945: 939: 899: 893: 873: 867: 755: 749: 2318:if the topological space in question is a 583:{\displaystyle f_{U}\in {\mathcal {F}}(U)} 2735: 2719: 2718: 2717: 2706: 2685: 2641: 2625: 2624: 2623: 2612: 2602: 2590: 2566: 2565: 2563: 2542: 2536: 2535: 2525: 2524: 2522: 2501: 2500: 2498: 2477: 2476: 2474: 2453: 2447: 2446: 2436: 2435: 2433: 2409: 2408: 2406: 2303: 2283: 2263: 2237: 2213: 2193: 2173: 2153: 2133: 2113: 2077: 2071: 2048: 2024: 2003: 1983: 1961: 1960: 1958: 1916: 1908: 1866: 1857: 1850: 1838: 1815: 1806: 1799: 1787: 1763: 1741: 1719: 1697: 1675: 1653: 1631: 1609: 1587: 1566: 1543: 1542: 1535: 1534: 1526: 1466: 1446: 1419: 1409: 1406: 1386: 1361: 1359: 1322: 1283: 1282: 1280: 1260: 1239: 1218: 1197: 1191: 1190: 1171: 1170: 1168: 1110: 1104: 1103: 1084: 1083: 1068: 1058: 1039: 1038: 1017: 1007: 982: 981: 972: 966: 937: 917: 891: 865: 844: 843: 834: 828: 803: 797: 796: 793: 773: 747: 727: 707: 687: 658: 628: 622: 601: 595: 565: 564: 555: 549: 517: 491: 468: 427: 426: 411: 401: 391: 385: 384: 381: 357: 351: 350: 347: 327: 306: 305: 303: 279: 278: 276: 255: 254: 252: 231: 209: 187: 165: 117:Learn how and when to remove this message 2298:. The same property holds for any point 742:be the inclusion of the one point space 1434:{\displaystyle {\underline {S}}_{x}=S} 7: 2852:"6.27 Skyscraper sheaves and stalks" 1942:{\displaystyle X=\mathrm {Spec} (A)} 853:{\displaystyle i^{-1}{\mathcal {F}}} 55:adding citations to reliable sources 2861:"Introduction to Perverse Sheaves" 1926: 1923: 1920: 1917: 919: 812:{\displaystyle {\mathcal {F}}_{x}} 366:{\displaystyle {\mathcal {F}}_{x}} 25: 1301:{\displaystyle {\mathcal {F}}(U)} 2713: 2710: 2707: 2619: 2616: 2613: 1374:{\displaystyle {\underline {S}}} 31: 2866:. Institute for Advanced Study. 1735:or whether it is so large that 42:needs additional citations for 2732: 2725: 2702: 2699: 2693: 2667: 2661: 2652: 2638: 2631: 2599: 2592: 2575:{\displaystyle {\mathcal {P}}} 2510:{\displaystyle {\mathcal {F}}} 2486:{\displaystyle {\mathcal {P}}} 2418:{\displaystyle {\mathcal {P}}} 2393:Both statements are false for 2242: 2101:On any topological space, the 1970:{\displaystyle {\mathcal {F}}} 1936: 1930: 1877:{\displaystyle 1+e^{-1/x^{2}}} 1826:{\displaystyle 1+e^{-1/x^{2}}} 1539: 1513:In contrast, for the sheaf of 1295: 1289: 1186: 1183: 1177: 1096: 1090: 1051: 1045: 1000: 988: 577: 571: 439: 433: 315:{\displaystyle {\mathcal {F}}} 288:{\displaystyle {\mathcal {F}}} 264:{\displaystyle {\mathcal {F}}} 1: 1669:on a small open neighborhood 1489:For example, in the sheaf of 1485:Sheaves of analytic functions 2850:The Stacks Project authors. 2841:The Stacks Project authors. 2361:A morphism of sheaves is an 1163:There is a natural morphism 531:{\displaystyle U\supseteq V} 247:, the behavior of the sheaf 1509:Sheaves of smooth functions 590:, where two such sections 2912: 2767:Hartshorne, Robin (1977). 2326:, since every point of a T 2278:positioned directly above 1890:Krull intersection theorem 925:{\displaystyle \emptyset } 2779:10.1007/978-1-4757-3849-0 148:Motivation and definition 129:Mathematical construction 2808:10.1017/CBO9780511661761 2796:Tennison, B. R. (1975). 1381:associated to some set, 2349:Properties of the stalk 505:{\displaystyle U\leq V} 152:Sheaves are defined on 2870:Kiran Kedlaya. 18.726 2750: 2674: 2576: 2552: 2511: 2487: 2463: 2419: 2334:, used for example in 2312: 2292: 2272: 2252: 2251:{\displaystyle G\to x} 2228:—hence the name 2222: 2202: 2182: 2162: 2142: 2122: 2087: 2057: 2033: 2012: 1992: 1971: 1943: 1896:Quasi-coherent sheaves 1878: 1827: 1772: 1757:is identically one in 1750: 1728: 1706: 1684: 1662: 1640: 1618: 1596: 1575: 1551: 1475: 1455: 1435: 1395: 1375: 1331: 1302: 1269: 1248: 1227: 1207: 1123: 952: 926: 906: 880: 854: 813: 782: 762: 736: 716: 696: 678:Alternative definition 667: 638: 611: 584: 532: 506: 477: 449: 367: 336: 316: 289: 265: 240: 218: 196: 174: 2751: 2675: 2577: 2553: 2512: 2488: 2464: 2420: 2343:injective resolutions 2313: 2293: 2273: 2253: 2223: 2203: 2183: 2163: 2143: 2123: 2088: 2086:{\displaystyle M_{p}} 2058: 2034: 2013: 1993: 1972: 1944: 1879: 1828: 1773: 1751: 1729: 1707: 1685: 1663: 1641: 1619: 1597: 1576: 1552: 1503:analytic continuation 1476: 1456: 1436: 1396: 1376: 1332: 1303: 1270: 1255:: it takes a section 1249: 1228: 1208: 1124: 953: 951:{\displaystyle \{x\}} 927: 907: 905:{\displaystyle \{x\}} 881: 879:{\displaystyle \{x\}} 855: 814: 783: 763: 761:{\displaystyle \{x\}} 737: 717: 697: 668: 639: 637:{\displaystyle f_{V}} 612: 610:{\displaystyle f_{U}} 585: 533: 507: 478: 450: 368: 337: 317: 290: 266: 241: 219: 197: 175: 156:, but the underlying 2684: 2589: 2562: 2521: 2497: 2473: 2432: 2405: 2332:Godement resolutions 2302: 2282: 2262: 2236: 2212: 2192: 2172: 2152: 2132: 2128:and a group or ring 2112: 2070: 2047: 2023: 2002: 1982: 1978:corresponding to an 1957: 1951:quasi-coherent sheaf 1907: 1837: 1786: 1762: 1740: 1718: 1696: 1674: 1652: 1630: 1608: 1586: 1565: 1525: 1465: 1445: 1405: 1385: 1358: 1321: 1279: 1259: 1238: 1217: 1167: 965: 936: 916: 890: 864: 827: 792: 772: 746: 726: 706: 686: 657: 621: 594: 548: 516: 490: 467: 380: 346: 326: 302: 275: 251: 230: 208: 186: 164: 132:In mathematics, the 51:improve this article 2876:LEC # 3 - 5 Sheaves 2040:corresponding to a 1156:, which are namely 958:, however, we get: 819:is the same as the 18:Stalk (mathematics) 2872:Algebraic Geometry 2770:Algebraic Geometry 2746: 2670: 2572: 2548: 2507: 2483: 2459: 2415: 2336:algebraic geometry 2308: 2288: 2268: 2248: 2218: 2198: 2178: 2158: 2138: 2118: 2083: 2053: 2029: 2008: 1988: 1967: 1939: 1874: 1823: 1768: 1746: 1724: 1702: 1680: 1658: 1636: 1614: 1592: 1571: 1547: 1491:analytic functions 1471: 1451: 1431: 1417: 1391: 1371: 1369: 1327: 1298: 1265: 1244: 1223: 1203: 1119: 1079: 1066: 1034: 1015: 948: 922: 902: 876: 850: 809: 788:. Then the stalk 778: 758: 732: 712: 692: 663: 634: 607: 580: 542:universal property 540:By definition (or 528: 502: 473: 445: 422: 409: 363: 342:, usually denoted 332: 312: 285: 261: 236: 214: 192: 170: 66:"Stalk" sheaf 2401:Given a presheaf 2311:{\displaystyle x} 2291:{\displaystyle x} 2271:{\displaystyle G} 2221:{\displaystyle x} 2201:{\displaystyle G} 2181:{\displaystyle x} 2161:{\displaystyle 0} 2141:{\displaystyle G} 2121:{\displaystyle x} 2056:{\displaystyle p} 2032:{\displaystyle x} 2011:{\displaystyle M} 1991:{\displaystyle A} 1949:, the stalk of a 1771:{\displaystyle U} 1749:{\displaystyle f} 1727:{\displaystyle U} 1713:fits entirely in 1705:{\displaystyle f} 1683:{\displaystyle U} 1661:{\displaystyle f} 1639:{\displaystyle f} 1617:{\displaystyle f} 1595:{\displaystyle f} 1574:{\displaystyle f} 1495:analytic manifold 1474:{\displaystyle X} 1454:{\displaystyle x} 1410: 1394:{\displaystyle S} 1362: 1330:{\displaystyle X} 1268:{\displaystyle s} 1247:{\displaystyle x} 1226:{\displaystyle U} 1213:for any open set 1059: 1057: 1008: 1006: 781:{\displaystyle X} 735:{\displaystyle i} 715:{\displaystyle X} 695:{\displaystyle x} 666:{\displaystyle x} 476:{\displaystyle x} 402: 400: 335:{\displaystyle x} 239:{\displaystyle x} 217:{\displaystyle X} 195:{\displaystyle x} 173:{\displaystyle X} 158:topological space 127: 126: 119: 101: 16:(Redirected from 2903: 2867: 2865: 2855: 2846: 2821: 2792: 2755: 2753: 2752: 2747: 2745: 2744: 2743: 2742: 2724: 2723: 2716: 2679: 2677: 2676: 2671: 2651: 2650: 2649: 2648: 2630: 2629: 2622: 2607: 2606: 2581: 2579: 2578: 2573: 2571: 2570: 2558:is the image of 2557: 2555: 2554: 2549: 2547: 2546: 2541: 2540: 2530: 2529: 2516: 2514: 2513: 2508: 2506: 2505: 2492: 2490: 2489: 2484: 2482: 2481: 2469:, the stalks of 2468: 2466: 2465: 2460: 2458: 2457: 2452: 2451: 2441: 2440: 2424: 2422: 2421: 2416: 2414: 2413: 2317: 2315: 2314: 2309: 2297: 2295: 2294: 2289: 2277: 2275: 2274: 2269: 2257: 2255: 2254: 2249: 2227: 2225: 2224: 2219: 2207: 2205: 2204: 2199: 2187: 2185: 2184: 2179: 2167: 2165: 2164: 2159: 2147: 2145: 2144: 2139: 2127: 2125: 2124: 2119: 2105:associated to a 2103:skyscraper sheaf 2097:Skyscraper sheaf 2092: 2090: 2089: 2084: 2082: 2081: 2062: 2060: 2059: 2054: 2038: 2036: 2035: 2030: 2017: 2015: 2014: 2009: 1997: 1995: 1994: 1989: 1976: 1974: 1973: 1968: 1966: 1965: 1948: 1946: 1945: 1940: 1929: 1883: 1881: 1880: 1875: 1873: 1872: 1871: 1870: 1861: 1832: 1830: 1829: 1824: 1822: 1821: 1820: 1819: 1810: 1777: 1775: 1774: 1769: 1755: 1753: 1752: 1747: 1733: 1731: 1730: 1725: 1711: 1709: 1708: 1703: 1689: 1687: 1686: 1681: 1667: 1665: 1664: 1659: 1645: 1643: 1642: 1637: 1623: 1621: 1620: 1615: 1601: 1599: 1598: 1593: 1580: 1578: 1577: 1572: 1556: 1554: 1553: 1548: 1546: 1538: 1515:smooth functions 1480: 1478: 1477: 1472: 1460: 1458: 1457: 1452: 1440: 1438: 1437: 1432: 1424: 1423: 1418: 1400: 1398: 1397: 1392: 1380: 1378: 1377: 1372: 1370: 1347:Constant sheaves 1336: 1334: 1333: 1328: 1307: 1305: 1304: 1299: 1288: 1287: 1274: 1272: 1271: 1266: 1253: 1251: 1250: 1245: 1232: 1230: 1229: 1224: 1212: 1210: 1209: 1204: 1202: 1201: 1196: 1195: 1176: 1175: 1146:category of sets 1128: 1126: 1125: 1120: 1115: 1114: 1109: 1108: 1089: 1088: 1078: 1067: 1044: 1043: 1033: 1016: 987: 986: 980: 979: 957: 955: 954: 949: 931: 929: 928: 923: 911: 909: 908: 903: 885: 883: 882: 877: 859: 857: 856: 851: 849: 848: 842: 841: 818: 816: 815: 810: 808: 807: 802: 801: 787: 785: 784: 779: 767: 765: 764: 759: 741: 739: 738: 733: 721: 719: 718: 713: 701: 699: 698: 693: 672: 670: 669: 664: 643: 641: 640: 635: 633: 632: 616: 614: 613: 608: 606: 605: 589: 587: 586: 581: 570: 569: 560: 559: 539: 537: 535: 534: 529: 511: 509: 508: 503: 482: 480: 479: 474: 454: 452: 451: 446: 432: 431: 421: 410: 396: 395: 390: 389: 372: 370: 369: 364: 362: 361: 356: 355: 341: 339: 338: 333: 321: 319: 318: 313: 311: 310: 294: 292: 291: 286: 284: 283: 270: 268: 267: 262: 260: 259: 245: 243: 242: 237: 223: 221: 220: 215: 201: 199: 198: 193: 179: 177: 176: 171: 122: 115: 111: 108: 102: 100: 59: 35: 27: 21: 2911: 2910: 2906: 2905: 2904: 2902: 2901: 2900: 2886: 2885: 2863: 2859:Goresky, Mark. 2858: 2849: 2840: 2828: 2818: 2795: 2789: 2766: 2763: 2731: 2705: 2682: 2681: 2637: 2611: 2598: 2587: 2586: 2560: 2559: 2534: 2519: 2518: 2495: 2494: 2471: 2470: 2445: 2430: 2429: 2403: 2402: 2377:In particular: 2351: 2329: 2323: 2300: 2299: 2280: 2279: 2260: 2259: 2234: 2233: 2210: 2209: 2190: 2189: 2170: 2169: 2150: 2149: 2148:has the stalks 2130: 2129: 2110: 2109: 2099: 2073: 2068: 2067: 2045: 2044: 2021: 2020: 2000: 1999: 1980: 1979: 1955: 1954: 1905: 1904: 1898: 1886:Noetherian ring 1862: 1846: 1835: 1834: 1811: 1795: 1784: 1783: 1760: 1759: 1738: 1737: 1716: 1715: 1694: 1693: 1672: 1671: 1650: 1649: 1628: 1627: 1606: 1605: 1584: 1583: 1563: 1562: 1523: 1522: 1519:smooth manifold 1511: 1487: 1463: 1462: 1443: 1442: 1408: 1403: 1402: 1383: 1382: 1356: 1355: 1349: 1344: 1319: 1318: 1277: 1276: 1257: 1256: 1236: 1235: 1215: 1214: 1189: 1165: 1164: 1135: 1102: 968: 963: 962: 934: 933: 914: 913: 888: 887: 862: 861: 830: 825: 824: 795: 790: 789: 770: 769: 744: 743: 724: 723: 704: 703: 684: 683: 680: 655: 654: 644:are considered 624: 619: 618: 597: 592: 591: 551: 546: 545: 514: 513: 488: 487: 485: 465: 464: 383: 378: 377: 349: 344: 343: 324: 323: 300: 299: 273: 272: 249: 248: 228: 227: 206: 205: 184: 183: 162: 161: 150: 130: 123: 112: 106: 103: 60: 58: 48: 36: 23: 22: 15: 12: 11: 5: 2909: 2907: 2899: 2898: 2888: 2887: 2884: 2883: 2868: 2856: 2847: 2838: 2827: 2826:External links 2824: 2823: 2822: 2816: 2793: 2787: 2762: 2759: 2758: 2757: 2741: 2738: 2734: 2730: 2727: 2722: 2715: 2712: 2709: 2704: 2701: 2698: 2695: 2692: 2689: 2669: 2666: 2663: 2660: 2657: 2654: 2647: 2644: 2640: 2636: 2633: 2628: 2621: 2618: 2615: 2610: 2605: 2601: 2597: 2594: 2569: 2545: 2539: 2533: 2528: 2504: 2480: 2456: 2450: 2444: 2439: 2427:sheafification 2412: 2391: 2390: 2375: 2374: 2350: 2347: 2327: 2321: 2307: 2287: 2267: 2247: 2244: 2241: 2217: 2197: 2177: 2157: 2137: 2117: 2098: 2095: 2080: 2076: 2052: 2028: 2007: 1987: 1964: 1938: 1935: 1932: 1928: 1925: 1922: 1919: 1915: 1912: 1897: 1894: 1869: 1865: 1860: 1856: 1853: 1849: 1845: 1842: 1818: 1814: 1809: 1805: 1802: 1798: 1794: 1791: 1767: 1745: 1723: 1701: 1679: 1657: 1635: 1613: 1591: 1570: 1545: 1541: 1537: 1533: 1530: 1510: 1507: 1486: 1483: 1470: 1450: 1430: 1427: 1422: 1416: 1413: 1390: 1368: 1365: 1353:constant sheaf 1348: 1345: 1343: 1340: 1326: 1297: 1294: 1291: 1286: 1264: 1243: 1222: 1200: 1194: 1188: 1185: 1182: 1179: 1174: 1150:abelian groups 1134: 1131: 1130: 1129: 1118: 1113: 1107: 1101: 1098: 1095: 1092: 1087: 1082: 1077: 1074: 1071: 1065: 1062: 1056: 1053: 1050: 1047: 1042: 1037: 1032: 1029: 1026: 1023: 1020: 1014: 1011: 1005: 1002: 999: 996: 993: 990: 985: 978: 975: 971: 947: 944: 941: 921: 901: 898: 895: 875: 872: 869: 847: 840: 837: 833: 806: 800: 777: 757: 754: 751: 731: 711: 691: 679: 676: 662: 631: 627: 604: 600: 579: 576: 573: 568: 563: 558: 554: 527: 524: 521: 501: 498: 495: 472: 456: 455: 444: 441: 438: 435: 430: 425: 420: 417: 414: 408: 405: 399: 394: 388: 360: 354: 331: 309: 282: 258: 235: 213: 191: 169: 149: 146: 128: 125: 124: 39: 37: 30: 24: 14: 13: 10: 9: 6: 4: 3: 2: 2908: 2897: 2894: 2893: 2891: 2881: 2877: 2873: 2869: 2862: 2857: 2853: 2848: 2844: 2843:"6.11 Stalks" 2839: 2837: 2833: 2830: 2829: 2825: 2819: 2817:9780521207843 2813: 2809: 2805: 2801: 2800: 2794: 2790: 2788:9780387902449 2784: 2780: 2776: 2772: 2771: 2765: 2764: 2760: 2739: 2736: 2728: 2696: 2690: 2687: 2664: 2658: 2655: 2645: 2642: 2634: 2608: 2603: 2595: 2585: 2543: 2531: 2454: 2442: 2428: 2400: 2399: 2398: 2396: 2388: 2384: 2380: 2379: 2378: 2372: 2368: 2364: 2360: 2359: 2358: 2356: 2348: 2346: 2344: 2341: 2337: 2333: 2325: 2305: 2285: 2265: 2245: 2239: 2231: 2215: 2195: 2175: 2155: 2135: 2115: 2108: 2104: 2096: 2094: 2078: 2074: 2066: 2050: 2043: 2039: 2026: 2005: 1985: 1977: 1952: 1933: 1913: 1910: 1903: 1902:affine scheme 1895: 1893: 1891: 1887: 1867: 1863: 1858: 1854: 1851: 1847: 1843: 1840: 1816: 1812: 1807: 1803: 1800: 1796: 1792: 1789: 1780: 1778: 1765: 1756: 1743: 1734: 1721: 1712: 1699: 1690: 1677: 1668: 1655: 1646: 1633: 1624: 1611: 1602: 1589: 1568: 1560: 1559:bump function 1531: 1528: 1520: 1516: 1508: 1506: 1504: 1500: 1496: 1492: 1484: 1482: 1468: 1448: 1428: 1425: 1420: 1414: 1411: 1388: 1366: 1363: 1354: 1346: 1341: 1339: 1337: 1324: 1315: 1311: 1292: 1262: 1254: 1241: 1220: 1198: 1180: 1161: 1159: 1155: 1151: 1147: 1143: 1140: 1132: 1116: 1111: 1099: 1093: 1080: 1075: 1072: 1069: 1063: 1060: 1054: 1048: 1035: 1027: 1021: 1018: 1012: 1009: 1003: 994: 976: 973: 969: 961: 960: 959: 942: 896: 870: 838: 835: 831: 822: 821:inverse image 804: 775: 752: 729: 709: 689: 677: 675: 673: 660: 651: 647: 629: 625: 602: 598: 574: 561: 556: 552: 543: 525: 522: 519: 499: 496: 493: 483: 470: 461: 442: 436: 423: 418: 415: 412: 406: 403: 397: 392: 376: 375: 374: 358: 329: 296: 246: 233: 224: 211: 202: 189: 180: 167: 159: 155: 147: 145: 143: 139: 135: 121: 118: 110: 99: 96: 92: 89: 85: 82: 78: 75: 71: 68: –  67: 63: 62:Find sources: 56: 52: 46: 45: 40:This article 38: 34: 29: 28: 19: 2896:Sheaf theory 2799:Sheaf Theory 2798: 2769: 2584:left adjoint 2582:through the 2392: 2376: 2371:monomorphism 2355:gluing axiom 2352: 2345:of sheaves. 2107:closed point 2100: 2065:localization 2063:is just the 2019: 1953: 1899: 1781: 1758: 1736: 1714: 1692: 1670: 1648: 1626: 1604: 1582: 1512: 1499:power series 1488: 1350: 1317: 1309: 1234: 1162: 1141: 1136: 681: 653: 650:neighborhood 463: 460:direct limit 457: 297: 226: 204: 182: 160: 151: 142:mathematical 133: 131: 113: 104: 94: 87: 80: 73: 61: 49:Please help 44:verification 41: 2385:of a given 2367:epimorphism 2363:isomorphism 2042:prime ideal 2018:in a point 1233:containing 2395:presheaves 2340:functorial 2230:skyscraper 1158:cocomplete 1139:categories 722:, and let 646:equivalent 77:newspapers 2761:Reference 2703:→ 2653:→ 2596:− 2383:exactness 2243:→ 1852:− 1801:− 1540:→ 1415:_ 1367:_ 1187:→ 1137:For some 1081:⁡ 1073:∋ 1064:→ 1036:⁡ 1022:⊇ 1013:→ 974:− 920:∅ 836:− 562:∈ 523:⊇ 497:≤ 458:Here the 424:⁡ 416:∋ 407:→ 154:open sets 107:June 2022 2890:Category 2880:BY-NC-SA 2425:and its 1998:-module 1441:for all 1342:Examples 2387:functor 2338:to get 1888:. The 1308:to its 1133:Remarks 91:scholar 2814:  2785:  1900:On an 1493:on an 823:sheaf 373:, is: 93:  86:  79:  72:  64:  2864:(PDF) 2832:stalk 2369:, or 2324:space 1557:be a 1517:on a 1154:rings 768:into 617:and 512:, if 140:is a 138:sheaf 136:of a 134:stalk 98:JSTOR 84:books 2836:nLab 2812:ISBN 2783:ISBN 2493:and 2258:has 2188:and 2168:off 1351:The 1314:germ 1310:germ 912:and 886:are 70:news 2834:in 2804:doi 2775:doi 2208:on 1461:in 1275:in 1152:or 1061:lim 1010:lim 702:of 652:of 404:lim 322:at 203:of 53:by 2892:: 2810:. 2802:. 2781:. 2773:. 2365:, 2093:. 1779:. 1481:. 1338:. 1160:. 674:. 538:). 398::= 2882:. 2874:( 2854:. 2845:. 2820:. 2806:: 2791:. 2777:: 2740:p 2737:o 2733:) 2729:X 2726:( 2721:O 2714:t 2711:e 2708:S 2700:) 2697:X 2694:( 2691:h 2688:S 2668:) 2665:X 2662:( 2659:h 2656:S 2646:p 2643:o 2639:) 2635:X 2632:( 2627:O 2620:t 2617:e 2614:S 2609:: 2604:+ 2600:) 2593:( 2568:P 2544:+ 2538:P 2532:= 2527:F 2503:F 2479:P 2455:+ 2449:P 2443:= 2438:F 2411:P 2328:1 2322:1 2320:T 2306:x 2286:x 2266:G 2246:x 2240:G 2216:x 2196:G 2176:x 2156:0 2136:G 2116:x 2079:p 2075:M 2051:p 2027:x 2006:M 1986:A 1963:F 1937:) 1934:A 1931:( 1927:c 1924:e 1921:p 1918:S 1914:= 1911:X 1868:2 1864:x 1859:/ 1855:1 1848:e 1844:+ 1841:1 1817:2 1813:x 1808:/ 1804:1 1797:e 1793:+ 1790:1 1766:U 1744:f 1722:U 1700:f 1678:U 1656:f 1634:f 1612:f 1590:f 1569:f 1544:R 1536:R 1532:: 1529:f 1469:X 1449:x 1429:S 1426:= 1421:x 1412:S 1389:S 1364:S 1325:X 1296:) 1293:U 1290:( 1285:F 1263:s 1242:x 1221:U 1199:x 1193:F 1184:) 1181:U 1178:( 1173:F 1142:C 1117:. 1112:x 1106:F 1100:= 1097:) 1094:U 1091:( 1086:F 1076:x 1070:U 1055:= 1052:) 1049:U 1046:( 1041:F 1031:} 1028:x 1025:{ 1019:U 1004:= 1001:) 998:} 995:x 992:{ 989:( 984:F 977:1 970:i 946:} 943:x 940:{ 900:} 897:x 894:{ 874:} 871:x 868:{ 846:F 839:1 832:i 805:x 799:F 776:X 756:} 753:x 750:{ 730:i 710:X 690:x 661:x 630:V 626:f 603:U 599:f 578:) 575:U 572:( 567:F 557:U 553:f 526:V 520:U 500:V 494:U 486:( 471:x 443:. 440:) 437:U 434:( 429:F 419:x 413:U 393:x 387:F 359:x 353:F 330:x 308:F 281:F 257:F 234:x 212:X 190:x 168:X 120:) 114:( 109:) 105:( 95:· 88:· 81:· 74:· 47:. 20:)

Index

Stalk (mathematics)

verification
improve this article
adding citations to reliable sources
"Stalk" sheaf
news
newspapers
books
scholar
JSTOR
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sheaf
mathematical
open sets
topological space
direct limit
universal property
equivalent
neighborhood
inverse image
categories
category of sets
abelian groups
rings
cocomplete
germ
constant sheaf
analytic functions
analytic manifold

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