Knowledge (XXG)

Almost complex manifold

Source 📝

1432: 1278: 1441:
The converse question, whether the almost complex structure implies the existence of a complex structure is much less trivial, and not true in general. On an arbitrary almost complex manifold one can always find coordinates for which the almost complex structure takes the above canonical form at any
2101: 288:. Only when this local tensor can be patched together to be defined globally does the pointwise linear complex structure yield an almost complex structure, which is then uniquely determined. The possibility of this patching, and therefore existence of an almost complex structure on a manifold 1437:
One easily checks that this map defines an almost complex structure. Thus any complex structure on a manifold yields an almost complex structure, which is said to be 'induced' by the complex structure, and the complex structure is said to be 'compatible with' the almost complex structure.
2235:
The existence of an almost complex structure is a topological question and is relatively easy to answer, as discussed above. The existence of an integrable almost complex structure, on the other hand, is a much more difficult analytic question. For example, it is still not known whether
1289: 2135: = 0. The compatible complex structure is unique, as discussed above. Since the existence of an integrable almost complex structure is equivalent to the existence of a complex structure, this is sometimes taken as the definition of a complex structure. 2138:
There are several other criteria which are equivalent to the vanishing of the Nijenhuis tensor, and which therefore furnish methods for checking the integrability of an almost complex structure (and in fact each of these can be found in the literature):
1162: 617:, we can build exterior powers of the complexified cotangent bundle (which is canonically isomorphic to the bundle of dual spaces of the complexified tangent bundle). The almost complex structure induces the decomposition of each space of 1086: 727: 1889: 899: 1427:{\displaystyle J{\frac {\partial }{\partial z^{\mu }}}=i{\frac {\partial }{\partial z^{\mu }}}\qquad J{\frac {\partial }{\partial {\bar {z}}^{\mu }}}=-i{\frac {\partial }{\partial {\bar {z}}^{\mu }}}.} 2184: 840: 1154: 1665: 2227: 2465:
In each of these equations, the two structures on the right hand side are called compatible when the corresponding construction yields a structure of the type specified. For example,
965: 404: 463: 1273:{\displaystyle J{\frac {\partial }{\partial x^{\mu }}}={\frac {\partial }{\partial y^{\mu }}}\qquad J{\frac {\partial }{\partial y^{\mu }}}=-{\frac {\partial }{\partial x^{\mu }}}} 1853: 180: 1711: 922: 136: 984: 3814: 2705: 3005: 43:
is an almost complex manifold, but there are almost complex manifolds that are not complex manifolds. Almost complex structures have important applications in
3809: 2096:{\displaystyle -(N_{A})_{ij}^{k}=A_{i}^{m}\partial _{m}A_{j}^{k}-A_{j}^{m}\partial _{m}A_{i}^{k}-A_{m}^{k}(\partial _{i}A_{j}^{m}-\partial _{j}A_{i}^{m}).} 627: 3096: 3120: 2248: 1486: 3315: 3185: 2915: 2240:
admits an integrable almost complex structure, despite a long history of ultimately unverified claims. Smoothness issues are important. For
3411: 2559: 2629: 3464: 2992: 264:
shows that any even dimensional vector space admits a linear complex structure. Therefore, an even dimensional manifold always admits a
2656: 2107: 3748: 2895: 2872: 3513: 846: 293: 3105: 2765: 2763:; Bazzoni, Giovanni; Goertsches, Oliver; Konstantis, Panagiotis; Rollenske, Sönke (2018). "On the history of the Hopf problem". 3496: 2934: 788:). Thus we may use the almost complex structure to refine the action of the exterior derivative to the forms of definite type 85:
which squares to −1) on each tangent space of the manifold, which varies smoothly on the manifold. In other words, we have a
3708: 2613: 3693: 3416: 3190: 2641: 2590: 756: 3738: 2148: 3743: 3713: 3421: 3377: 3358: 3125: 3069: 2608:
An almost complex structure integrates to a complex structure if the half-dimensional subspace is closed under the
794: 3857: 3280: 3145: 2505: 1103: 1518: 3665: 3530: 3222: 3064: 2190: 32: 943: 351: 3362: 3332: 3256: 3202: 3032: 2985: 1451: 413: 3130: 3703: 3322: 3217: 3037: 1719: 508:, inherits an almost complex structure from the octonion multiplication; the question of whether it has a 3352: 3347: 2815: 2493:: the complex structures on the tangent fibres compatible with the restriction to the symplectic forms. 197:
admits an almost complex structure, it must be even-dimensional. This can be seen as follows. Suppose
147: 3683: 3621: 3469: 3173: 3163: 3135: 3110: 3020: 2883: 2714: 2567: 1467: 967:
is a map which increases the antiholomorphic part of the type by one. These operators are called the
2571: 3821: 3794: 3503: 3381: 3366: 3295: 3054: 2860: 2678: 774: 254: 44: 3763: 3718: 3615: 3486: 3290: 3115: 2978: 2951: 2840: 2792: 2774: 2586: 968: 321: 3300: 2661: 2537: 1677: 1081:{\displaystyle d=\sum _{r+s=p+q+1}\pi _{r,s}\circ d=\partial +{\overline {\partial }}+\cdots .} 907: 3698: 3678: 3673: 3580: 3491: 3305: 3285: 3140: 3079: 2929: 2911: 2891: 2868: 2832: 2742: 2602: 2279: 2259:, analysis is required (with more difficult techniques as the regularity hypothesis weakens). 975: 606: 105: 51: 3836: 3630: 3585: 3508: 3479: 3337: 3270: 3265: 3260: 3250: 3042: 3025: 2943: 2824: 2784: 2732: 2722: 2667: 2594: 2315: 1470: 1097: 614: 598:
on the (1, 0)-vector fields of the complexified tangent bundle, and multiplication by −
336:
admits an almost complex structure. An example for such an almost complex structure is (1 ≤
40: 2963: 2852: 3779: 3688: 3518: 3474: 3240: 2959: 2848: 2810: 2617: 2575: 2298: 2272: 86: 28: 1858:
The individual expressions on the right depend on the choice of the smooth vector fields
2718: 2232:
Any of these conditions implies the existence of a unique compatible complex structure.
1458:. Such coordinates, if they exist, are called 'local holomorphic coordinates for J'. If 3645: 3570: 3540: 3438: 3431: 3371: 3342: 3212: 3207: 3168: 2673: 2620:. If furthermore this half-dimensional space is the annihilator of a nowhere vanishing 2609: 2579: 924:
is a map which increases the holomorphic part of the type by one (takes forms of type (
610: 593: 497: 261: 183: 2737: 2700: 3851: 3831: 3655: 3650: 3635: 3625: 3575: 3552: 3426: 3386: 3327: 3275: 3074: 2796: 2760: 2555: 2544: 2241: 1493:
is induced by a complex structure, then it is induced by a unique complex structure.
722:{\displaystyle \Omega ^{r}(M)^{\mathbf {C} }=\bigoplus _{p+q=r}\Omega ^{(p,q)}(M).\,} 139: 36: 3758: 3753: 3595: 3562: 3535: 3443: 3084: 2925: 581: 89: 492:
cannot be given an almost complex structure (Ehresmann and Hopf). In the case of
2788: 2143:
The Lie bracket of any two (1, 0)-vector fields is again of type (1, 0)
3601: 3590: 3547: 3448: 3049: 2650: 2621: 142: 20: 568:(which is the vector bundle of complexified tangent spaces at each point) into 3826: 3784: 3610: 3523: 3155: 3059: 545: 517: 82: 55: 2836: 496:, the almost complex structure comes from an honest complex structure on the 3640: 3605: 3310: 3197: 2598: 2746: 2727: 2585:. A generalized almost complex structure is a choice of a half-dimensional 2110:, which generalizes the Lie bracket of vector fields, the Nijenhuis tensor 3804: 3799: 3789: 3180: 3001: 2574:. An ordinary almost complex structure is a choice of a half-dimensional 505: 272:(which is just a linear transformation on each tangent space) such that 2970: 2955: 2879:
Information on compatible triples, Kähler and Hermitian manifolds, etc.
2844: 1100:
is itself an almost complex manifold. In local holomorphic coordinates
2701:"On the Chern numbers of certain complex and almost complex manifolds" 1446:. In general, however, it is not possible to find coordinates so that 3396: 2566:, which was elaborated in the doctoral dissertations of his students 1866:, but the left side actually depends only on the pointwise values of 473: 96: 2947: 2828: 2813:(1957). "Complex analytic coordinates in almost complex manifolds". 186:. A manifold equipped with an almost complex structure is called an 2779: 2379:
when each structure can be specified by the two others as follows:
2664: – Manifold with Riemannian, complex and symplectic structure 2974: 2485:
whose sections are the almost complex structures compatible to
253:
has an almost complex structure. One can show that it must be
2932:(1953). "Groupes de Lie et puissances réduites de Steenrod". 1883:
is a tensor. This is also clear from the component formula
894:{\displaystyle {\overline {\partial }}=\pi _{p,q+1}\circ d} 2500:, one can show that a compatible almost complex structure 564:
allows a decomposition of the complexified tangent bundle
2612:. A generalized almost complex structure integrates to a 509: 2902:
Short section which introduces standard basic material.
2670: – Mathematical structure in differential geometry 2646:
Pages displaying short descriptions of redirect targets
2597:. In both cases one demands that the direct sum of the 1466:
around every point then these patch together to form a
1670:
or, for the usual case of an almost complex structure
1477:
giving it a complex structure, which moreover induces
978:, we note that the exterior derivative can be written 2193: 2151: 1892: 1722: 1680: 1521: 1292: 1165: 1106: 987: 946: 910: 849: 797: 630: 416: 354: 150: 108: 504:, when considered as the set of unit norm imaginary 3772: 3731: 3664: 3561: 3457: 3404: 3395: 3231: 3154: 3093: 3013: 2496:Using elementary properties of the symplectic form 2247:, the Newlander–Nirenberg theorem follows from the 560:, respectively), so an almost complex structure on 2221: 2178: 2095: 1847: 1705: 1659: 1426: 1283:(just like a counterclockwise rotation of π/2) or 1272: 1148: 1080: 959: 916: 893: 834: 721: 457: 398: 174: 130: 2681: – Type of manifold in differential geometry 974:Since the sum of all the projections must be the 524:Differential topology of almost complex manifolds 2653: – Characteristic classes of vector bundles 1508:is a tensor field of rank (1, 1), then the 2706:Proceedings of the National Academy of Sciences 2363:. With this understood, the three structures ( 2179:{\displaystyle d=\partial +{\bar {\partial }}} 528:Just as a complex structure on a vector space 2986: 835:{\displaystyle \partial =\pi _{p+1,q}\circ d} 8: 1149:{\displaystyle z^{\mu }=x^{\mu }+iy^{\mu }} 3401: 2993: 2979: 2971: 2888:Differential Analysis on Complex Manifolds 2766:Differential Geometry and Its Applications 2359:, is given by the analogous operation for 1660:{\displaystyle N_{A}(X,Y)=-A^{2}+A(+)-.\,} 485: 476:which admit almost complex structures are 320:. The existence question is then a purely 81:is a linear complex structure (that is, a 2778: 2736: 2726: 2481:•) is a Riemannian metric. The bundle on 2222:{\displaystyle {\bar {\partial }}^{2}=0.} 2207: 2196: 2195: 2192: 2165: 2164: 2150: 2081: 2076: 2066: 2053: 2048: 2038: 2025: 2020: 2007: 2002: 1992: 1982: 1977: 1964: 1959: 1949: 1939: 1934: 1921: 1913: 1903: 1891: 1844: 1727: 1721: 1685: 1679: 1656: 1557: 1526: 1520: 1512:is a tensor field of rank (1,2) given by 1462:admits local holomorphic coordinates for 1412: 1401: 1400: 1390: 1372: 1361: 1360: 1350: 1337: 1324: 1309: 1296: 1291: 1261: 1248: 1233: 1220: 1207: 1194: 1182: 1169: 1164: 1140: 1124: 1111: 1105: 1059: 1032: 998: 986: 947: 945: 909: 867: 850: 848: 808: 796: 736:) admits a decomposition into a sum of Ω( 718: 688: 666: 652: 651: 635: 629: 437: 421: 415: 378: 359: 353: 149: 113: 107: 2908:Algebraic Geometry, a concise dictionary 2545:2 out of 3 property of the unitary group 2124:states that an almost complex structure 2691: 960:{\displaystyle {\overline {\partial }}} 588:is a vector field of type (0, 1). Thus 399:{\displaystyle J_{ij}=-\delta _{i,j-1}} 1450:takes the canonical form on an entire 458:{\displaystyle J_{ij}=\delta _{i,j+1}} 7: 2910:. Berlin/Boston: Walter De Gruyter. 2616:if the subspace is closed under the 2560:generalized almost complex structure 2551:Generalized almost complex structure 2301:, each induces a bundle isomorphism 1848:{\displaystyle N_{J}(X,Y)=+J(+)-.\,} 1092:Integrable almost complex structures 332:For every integer n, the flat space 759:, there is a canonical projection π 584:of type (1, 0), while a section of 324:one and is fairly well understood. 219:be an almost complex structure. If 2578:of each fiber of the complexified 2285:, and an almost complex structure 2198: 2167: 2158: 2063: 2035: 1989: 1946: 1396: 1392: 1356: 1352: 1330: 1326: 1302: 1298: 1254: 1250: 1226: 1222: 1200: 1196: 1175: 1171: 1061: 1053: 949: 911: 852: 798: 685: 632: 602:on the (0, 1)-vector fields. 14: 2543:These triples are related to the 2350:, •) and the other, denoted 592:corresponds to multiplication by 2593:of the complexified tangent and 653: 294:reduction of the structure group 175:{\displaystyle J\colon TM\to TM} 2935:American Journal of Mathematics 2865:Lectures on Symplectic Geometry 2630:generalized Calabi–Yau manifold 2305:, where the first map, denoted 1346: 1216: 3033:Differentiable/Smooth manifold 2589:subspace of each fiber of the 2473:are compatible if and only if 2201: 2170: 2087: 2031: 1910: 1896: 1838: 1820: 1814: 1811: 1796: 1790: 1775: 1772: 1763: 1751: 1745: 1733: 1650: 1632: 1626: 1623: 1608: 1602: 1587: 1584: 1575: 1563: 1544: 1532: 1406: 1366: 712: 706: 701: 689: 648: 641: 163: 1: 2890:. New York: Springer-Verlag. 2614:generalized complex structure 2128:is integrable if and only if 2789:10.1016/j.difgeo.2017.10.014 2699:Van de Ven, A. (June 1966). 2642:Almost quaternionic manifold 1064: 952: 855: 3739:Classification of manifolds 2657:Frölicher–Nijenhuis bracket 2644: – Concept in geometry 2605:yield the original bundle. 2558:introduced the notion of a 2122:Newlander–Nirenberg theorem 2108:Frölicher–Nijenhuis bracket 296:of the tangent bundle from 3874: 2508:for the Riemannian metric 532:allows a decomposition of 3815:over commutative algebras 1706:{\displaystyle J^{2}=-Id} 1500:on each tangent space of 917:{\displaystyle \partial } 773:) to Ω. We also have the 238:is a real manifold, then 70:be a smooth manifold. An 3531:Riemann curvature tensor 1156:one can define the maps 486:Borel & Serre (1953) 245:is a real number – thus 131:{\displaystyle J^{2}=-1} 72:almost complex structure 33:linear complex structure 2506:almost Kähler structure 732:In other words, each Ω( 188:almost complex manifold 31:equipped with a smooth 25:almost complex manifold 3323:Manifold with boundary 3038:Differential structure 2728:10.1073/pnas.55.6.1624 2223: 2180: 2117:is just one-half of . 2097: 1849: 1707: 1661: 1428: 1274: 1150: 1082: 961: 918: 895: 836: 723: 459: 400: 205:-dimensional, and let 176: 132: 50:The concept is due to 2906:Rubei, Elena (2014). 2816:Annals of Mathematics 2524:is integrable, then ( 2224: 2181: 2098: 1850: 1708: 1662: 1496:Given any linear map 1429: 1275: 1151: 1083: 962: 919: 896: 837: 724: 460: 401: 322:algebraic topological 177: 133: 3470:Covariant derivative 3021:Topological manifold 2861:Cannas da Silva, Ana 2191: 2149: 1890: 1720: 1678: 1519: 1485:is then said to be ' 1290: 1163: 1104: 985: 944: 932:) to forms of type ( 908: 847: 795: 628: 414: 352: 260:An easy exercise in 148: 106: 3504:Exterior derivative 3106:Atiyah–Singer index 3055:Riemannian manifold 2809:Newlander, August; 2719:1966PNAS...55.1624V 2679:Symplectic manifold 2491:contractible fibres 2271:is equipped with a 2086: 2058: 2030: 2012: 1987: 1969: 1944: 1926: 969:Dolbeault operators 775:exterior derivative 292:is equivalent to a 138:when regarded as a 45:symplectic geometry 3810:Secondary calculus 3764:Singularity theory 3719:Parallel transport 3487:De Rham cohomology 3126:Generalized Stokes 2930:Serre, Jean-Pierre 2314:, is given by the 2263:Compatible triples 2255:(and less smooth) 2219: 2176: 2093: 2072: 2044: 2016: 1998: 1973: 1955: 1930: 1909: 1845: 1703: 1657: 1424: 1270: 1146: 1078: 1027: 957: 914: 891: 832: 719: 683: 607:differential forms 552:corresponding to + 488:). In particular, 455: 396: 172: 128: 3845: 3844: 3727: 3726: 3492:Differential form 3146:Whitney embedding 3080:Differential form 2917:978-3-11-031622-3 2884:Wells, Raymond O. 2819:. Second Series. 2603:complex conjugate 2595:cotangent bundles 2377:compatible triple 2280:Riemannian metric 2249:Frobenius theorem 2204: 2173: 1419: 1409: 1379: 1369: 1344: 1316: 1268: 1240: 1214: 1189: 1067: 994: 955: 858: 662: 605:Just as we build 510:complex structure 62:Formal definition 52:Charles Ehresmann 3865: 3858:Smooth manifolds 3837:Stratified space 3795:Fréchet manifold 3509:Interior product 3402: 3099: 2995: 2988: 2981: 2972: 2967: 2921: 2901: 2878: 2856: 2811:Nirenberg, Louis 2801: 2800: 2782: 2757: 2751: 2750: 2740: 2730: 2713:(6): 1624–1627. 2696: 2668:Poisson manifold 2647: 2562:on the manifold 2316:interior product 2228: 2226: 2225: 2220: 2212: 2211: 2206: 2205: 2197: 2185: 2183: 2182: 2177: 2175: 2174: 2166: 2106:In terms of the 2102: 2100: 2099: 2094: 2085: 2080: 2071: 2070: 2057: 2052: 2043: 2042: 2029: 2024: 2011: 2006: 1997: 1996: 1986: 1981: 1968: 1963: 1954: 1953: 1943: 1938: 1925: 1920: 1908: 1907: 1854: 1852: 1851: 1846: 1732: 1731: 1712: 1710: 1709: 1704: 1690: 1689: 1666: 1664: 1663: 1658: 1562: 1561: 1531: 1530: 1510:Nijenhuis tensor 1433: 1431: 1430: 1425: 1420: 1418: 1417: 1416: 1411: 1410: 1402: 1391: 1380: 1378: 1377: 1376: 1371: 1370: 1362: 1351: 1345: 1343: 1342: 1341: 1325: 1317: 1315: 1314: 1313: 1297: 1279: 1277: 1276: 1271: 1269: 1267: 1266: 1265: 1249: 1241: 1239: 1238: 1237: 1221: 1215: 1213: 1212: 1211: 1195: 1190: 1188: 1187: 1186: 1170: 1155: 1153: 1152: 1147: 1145: 1144: 1129: 1128: 1116: 1115: 1098:complex manifold 1087: 1085: 1084: 1079: 1068: 1060: 1043: 1042: 1026: 966: 964: 963: 958: 956: 948: 923: 921: 920: 915: 900: 898: 897: 892: 884: 883: 859: 851: 841: 839: 838: 833: 825: 824: 728: 726: 725: 720: 705: 704: 682: 658: 657: 656: 640: 639: 615:cotangent bundle 512:is known as the 500:. The 6-sphere, 464: 462: 461: 456: 454: 453: 429: 428: 405: 403: 402: 397: 395: 394: 367: 366: 319: 307: 283: 267: 249:must be even if 244: 233: 225: 218: 181: 179: 178: 173: 137: 135: 134: 129: 118: 117: 101: 41:complex manifold 3873: 3872: 3868: 3867: 3866: 3864: 3863: 3862: 3848: 3847: 3846: 3841: 3780:Banach manifold 3773:Generalizations 3768: 3723: 3660: 3557: 3519:Ricci curvature 3475:Cotangent space 3453: 3391: 3233: 3227: 3186:Exponential map 3150: 3095: 3089: 3009: 2999: 2948:10.2307/2372495 2924: 2918: 2905: 2898: 2882: 2875: 2859: 2829:10.2307/1970051 2808: 2805: 2804: 2759: 2758: 2754: 2698: 2697: 2693: 2688: 2662:Kähler manifold 2645: 2638: 2618:Courant bracket 2568:Marco Gualtieri 2553: 2538:Kähler manifold 2456: 2447: 2358: 2338: 2325: 2313: 2273:symplectic form 2265: 2194: 2189: 2188: 2147: 2146: 2133: 2115: 2062: 2034: 1988: 1945: 1899: 1888: 1887: 1882: 1874:, which is why 1723: 1718: 1717: 1681: 1676: 1675: 1553: 1522: 1517: 1516: 1399: 1395: 1359: 1355: 1333: 1329: 1305: 1301: 1288: 1287: 1257: 1253: 1229: 1225: 1203: 1199: 1178: 1174: 1161: 1160: 1136: 1120: 1107: 1102: 1101: 1094: 1028: 983: 982: 942: 941: 906: 905: 863: 845: 844: 804: 793: 792: 768: 684: 647: 631: 626: 625: 611:exterior powers 576:. A section of 526: 433: 417: 412: 411: 374: 355: 350: 349: 330: 309: 297: 281: 273: 265: 239: 227: 220: 206: 146: 145: 109: 104: 103: 99: 64: 29:smooth manifold 17: 16:Smooth manifold 12: 11: 5: 3871: 3869: 3861: 3860: 3850: 3849: 3843: 3842: 3840: 3839: 3834: 3829: 3824: 3819: 3818: 3817: 3807: 3802: 3797: 3792: 3787: 3782: 3776: 3774: 3770: 3769: 3767: 3766: 3761: 3756: 3751: 3746: 3741: 3735: 3733: 3729: 3728: 3725: 3724: 3722: 3721: 3716: 3711: 3706: 3701: 3696: 3691: 3686: 3681: 3676: 3670: 3668: 3662: 3661: 3659: 3658: 3653: 3648: 3643: 3638: 3633: 3628: 3618: 3613: 3608: 3598: 3593: 3588: 3583: 3578: 3573: 3567: 3565: 3559: 3558: 3556: 3555: 3550: 3545: 3544: 3543: 3533: 3528: 3527: 3526: 3516: 3511: 3506: 3501: 3500: 3499: 3489: 3484: 3483: 3482: 3472: 3467: 3461: 3459: 3455: 3454: 3452: 3451: 3446: 3441: 3436: 3435: 3434: 3424: 3419: 3414: 3408: 3406: 3399: 3393: 3392: 3390: 3389: 3384: 3374: 3369: 3355: 3350: 3345: 3340: 3335: 3333:Parallelizable 3330: 3325: 3320: 3319: 3318: 3308: 3303: 3298: 3293: 3288: 3283: 3278: 3273: 3268: 3263: 3253: 3243: 3237: 3235: 3229: 3228: 3226: 3225: 3220: 3215: 3213:Lie derivative 3210: 3208:Integral curve 3205: 3200: 3195: 3194: 3193: 3183: 3178: 3177: 3176: 3169:Diffeomorphism 3166: 3160: 3158: 3152: 3151: 3149: 3148: 3143: 3138: 3133: 3128: 3123: 3118: 3113: 3108: 3102: 3100: 3091: 3090: 3088: 3087: 3082: 3077: 3072: 3067: 3062: 3057: 3052: 3047: 3046: 3045: 3040: 3030: 3029: 3028: 3017: 3015: 3014:Basic concepts 3011: 3010: 3000: 2998: 2997: 2990: 2983: 2975: 2969: 2968: 2942:(3): 409–448. 2922: 2916: 2903: 2896: 2880: 2873: 2857: 2823:(3): 391–404. 2803: 2802: 2761:Agricola, Ilka 2752: 2690: 2689: 2687: 2684: 2683: 2682: 2676: 2674:Rizza manifold 2671: 2665: 2659: 2654: 2648: 2637: 2634: 2580:tangent bundle 2572:Gil Cavalcanti 2552: 2549: 2463: 2462: 2452: 2443: 2430: 2407: 2354: 2334: 2330:) =  2321: 2309: 2264: 2261: 2230: 2229: 2218: 2215: 2210: 2203: 2200: 2186: 2172: 2169: 2163: 2160: 2157: 2154: 2144: 2131: 2113: 2104: 2103: 2092: 2089: 2084: 2079: 2075: 2069: 2065: 2061: 2056: 2051: 2047: 2041: 2037: 2033: 2028: 2023: 2019: 2015: 2010: 2005: 2001: 1995: 1991: 1985: 1980: 1976: 1972: 1967: 1962: 1958: 1952: 1948: 1942: 1937: 1933: 1929: 1924: 1919: 1916: 1912: 1906: 1902: 1898: 1895: 1878: 1856: 1855: 1843: 1840: 1837: 1834: 1831: 1828: 1825: 1822: 1819: 1816: 1813: 1810: 1807: 1804: 1801: 1798: 1795: 1792: 1789: 1786: 1783: 1780: 1777: 1774: 1771: 1768: 1765: 1762: 1759: 1756: 1753: 1750: 1747: 1744: 1741: 1738: 1735: 1730: 1726: 1702: 1699: 1696: 1693: 1688: 1684: 1668: 1667: 1655: 1652: 1649: 1646: 1643: 1640: 1637: 1634: 1631: 1628: 1625: 1622: 1619: 1616: 1613: 1610: 1607: 1604: 1601: 1598: 1595: 1592: 1589: 1586: 1583: 1580: 1577: 1574: 1571: 1568: 1565: 1560: 1556: 1552: 1549: 1546: 1543: 1540: 1537: 1534: 1529: 1525: 1435: 1434: 1423: 1415: 1408: 1405: 1398: 1394: 1389: 1386: 1383: 1375: 1368: 1365: 1358: 1354: 1349: 1340: 1336: 1332: 1328: 1323: 1320: 1312: 1308: 1304: 1300: 1295: 1281: 1280: 1264: 1260: 1256: 1252: 1247: 1244: 1236: 1232: 1228: 1224: 1219: 1210: 1206: 1202: 1198: 1193: 1185: 1181: 1177: 1173: 1168: 1143: 1139: 1135: 1132: 1127: 1123: 1119: 1114: 1110: 1093: 1090: 1089: 1088: 1077: 1074: 1071: 1066: 1063: 1058: 1055: 1052: 1049: 1046: 1041: 1038: 1035: 1031: 1025: 1022: 1019: 1016: 1013: 1010: 1007: 1004: 1001: 997: 993: 990: 954: 951: 913: 902: 901: 890: 887: 882: 879: 876: 873: 870: 866: 862: 857: 854: 842: 831: 828: 823: 820: 817: 814: 811: 807: 803: 800: 760: 730: 729: 717: 714: 711: 708: 703: 700: 697: 694: 691: 687: 681: 678: 675: 672: 669: 665: 661: 655: 650: 646: 643: 638: 634: 525: 522: 498:Riemann sphere 452: 449: 446: 443: 440: 436: 432: 427: 424: 420: 393: 390: 387: 384: 381: 377: 373: 370: 365: 362: 358: 329: 326: 284:at each point 277: 262:linear algebra 184:tangent bundle 171: 168: 165: 162: 159: 156: 153: 127: 124: 121: 116: 112: 63: 60: 58:in the 1940s. 15: 13: 10: 9: 6: 4: 3: 2: 3870: 3859: 3856: 3855: 3853: 3838: 3835: 3833: 3832:Supermanifold 3830: 3828: 3825: 3823: 3820: 3816: 3813: 3812: 3811: 3808: 3806: 3803: 3801: 3798: 3796: 3793: 3791: 3788: 3786: 3783: 3781: 3778: 3777: 3775: 3771: 3765: 3762: 3760: 3757: 3755: 3752: 3750: 3747: 3745: 3742: 3740: 3737: 3736: 3734: 3730: 3720: 3717: 3715: 3712: 3710: 3707: 3705: 3702: 3700: 3697: 3695: 3692: 3690: 3687: 3685: 3682: 3680: 3677: 3675: 3672: 3671: 3669: 3667: 3663: 3657: 3654: 3652: 3649: 3647: 3644: 3642: 3639: 3637: 3634: 3632: 3629: 3627: 3623: 3619: 3617: 3614: 3612: 3609: 3607: 3603: 3599: 3597: 3594: 3592: 3589: 3587: 3584: 3582: 3579: 3577: 3574: 3572: 3569: 3568: 3566: 3564: 3560: 3554: 3553:Wedge product 3551: 3549: 3546: 3542: 3539: 3538: 3537: 3534: 3532: 3529: 3525: 3522: 3521: 3520: 3517: 3515: 3512: 3510: 3507: 3505: 3502: 3498: 3497:Vector-valued 3495: 3494: 3493: 3490: 3488: 3485: 3481: 3478: 3477: 3476: 3473: 3471: 3468: 3466: 3463: 3462: 3460: 3456: 3450: 3447: 3445: 3442: 3440: 3437: 3433: 3430: 3429: 3428: 3427:Tangent space 3425: 3423: 3420: 3418: 3415: 3413: 3410: 3409: 3407: 3403: 3400: 3398: 3394: 3388: 3385: 3383: 3379: 3375: 3373: 3370: 3368: 3364: 3360: 3356: 3354: 3351: 3349: 3346: 3344: 3341: 3339: 3336: 3334: 3331: 3329: 3326: 3324: 3321: 3317: 3314: 3313: 3312: 3309: 3307: 3304: 3302: 3299: 3297: 3294: 3292: 3289: 3287: 3284: 3282: 3279: 3277: 3274: 3272: 3269: 3267: 3264: 3262: 3258: 3254: 3252: 3248: 3244: 3242: 3239: 3238: 3236: 3230: 3224: 3221: 3219: 3216: 3214: 3211: 3209: 3206: 3204: 3201: 3199: 3196: 3192: 3191:in Lie theory 3189: 3188: 3187: 3184: 3182: 3179: 3175: 3172: 3171: 3170: 3167: 3165: 3162: 3161: 3159: 3157: 3153: 3147: 3144: 3142: 3139: 3137: 3134: 3132: 3129: 3127: 3124: 3122: 3119: 3117: 3114: 3112: 3109: 3107: 3104: 3103: 3101: 3098: 3094:Main results 3092: 3086: 3083: 3081: 3078: 3076: 3075:Tangent space 3073: 3071: 3068: 3066: 3063: 3061: 3058: 3056: 3053: 3051: 3048: 3044: 3041: 3039: 3036: 3035: 3034: 3031: 3027: 3024: 3023: 3022: 3019: 3018: 3016: 3012: 3007: 3003: 2996: 2991: 2989: 2984: 2982: 2977: 2976: 2973: 2965: 2961: 2957: 2953: 2949: 2945: 2941: 2937: 2936: 2931: 2927: 2926:Borel, Armand 2923: 2919: 2913: 2909: 2904: 2899: 2897:0-387-90419-0 2893: 2889: 2885: 2881: 2876: 2874:3-540-42195-5 2870: 2866: 2862: 2858: 2854: 2850: 2846: 2842: 2838: 2834: 2830: 2826: 2822: 2818: 2817: 2812: 2807: 2806: 2798: 2794: 2790: 2786: 2781: 2776: 2772: 2768: 2767: 2762: 2756: 2753: 2748: 2744: 2739: 2734: 2729: 2724: 2720: 2716: 2712: 2708: 2707: 2702: 2695: 2692: 2685: 2680: 2677: 2675: 2672: 2669: 2666: 2663: 2660: 2658: 2655: 2652: 2649: 2643: 2640: 2639: 2635: 2633: 2631: 2627: 2623: 2619: 2615: 2611: 2606: 2604: 2600: 2596: 2592: 2588: 2584: 2581: 2577: 2573: 2569: 2565: 2561: 2557: 2556:Nigel Hitchin 2550: 2548: 2546: 2541: 2539: 2535: 2531: 2527: 2523: 2519: 2515: 2511: 2507: 2503: 2499: 2494: 2492: 2488: 2484: 2480: 2476: 2472: 2468: 2460: 2455: 2451: 2446: 2442: 2438: 2434: 2431: 2428: 2424: 2420: 2416: 2412: 2408: 2405: 2401: 2397: 2393: 2389: 2385: 2382: 2381: 2380: 2378: 2374: 2370: 2366: 2362: 2357: 2353: 2349: 2345: 2342: =  2341: 2337: 2333: 2329: 2324: 2320: 2317: 2312: 2308: 2304: 2300: 2299:nondegenerate 2296: 2292: 2288: 2284: 2281: 2277: 2274: 2270: 2262: 2260: 2258: 2254: 2250: 2246: 2243: 2242:real-analytic 2239: 2233: 2216: 2213: 2208: 2187: 2161: 2155: 2152: 2145: 2142: 2141: 2140: 2136: 2134: 2127: 2123: 2118: 2116: 2109: 2090: 2082: 2077: 2073: 2067: 2059: 2054: 2049: 2045: 2039: 2026: 2021: 2017: 2013: 2008: 2003: 1999: 1993: 1983: 1978: 1974: 1970: 1965: 1960: 1956: 1950: 1940: 1935: 1931: 1927: 1922: 1917: 1914: 1904: 1900: 1893: 1886: 1885: 1884: 1881: 1877: 1873: 1869: 1865: 1861: 1841: 1835: 1832: 1829: 1826: 1823: 1817: 1808: 1805: 1802: 1799: 1793: 1787: 1784: 1781: 1778: 1769: 1766: 1760: 1757: 1754: 1748: 1742: 1739: 1736: 1728: 1724: 1716: 1715: 1714: 1700: 1697: 1694: 1691: 1686: 1682: 1673: 1653: 1647: 1644: 1641: 1638: 1635: 1629: 1620: 1617: 1614: 1611: 1605: 1599: 1596: 1593: 1590: 1581: 1578: 1572: 1569: 1566: 1558: 1554: 1550: 1547: 1541: 1538: 1535: 1527: 1523: 1515: 1514: 1513: 1511: 1507: 1503: 1499: 1494: 1492: 1488: 1484: 1480: 1476: 1472: 1469: 1465: 1461: 1457: 1453: 1449: 1445: 1439: 1421: 1413: 1403: 1387: 1384: 1381: 1373: 1363: 1347: 1338: 1334: 1321: 1318: 1310: 1306: 1293: 1286: 1285: 1284: 1262: 1258: 1245: 1242: 1234: 1230: 1217: 1208: 1204: 1191: 1183: 1179: 1166: 1159: 1158: 1157: 1141: 1137: 1133: 1130: 1125: 1121: 1117: 1112: 1108: 1099: 1091: 1075: 1072: 1069: 1056: 1050: 1047: 1044: 1039: 1036: 1033: 1029: 1023: 1020: 1017: 1014: 1011: 1008: 1005: 1002: 999: 995: 991: 988: 981: 980: 979: 977: 972: 970: 939: 935: 931: 927: 888: 885: 880: 877: 874: 871: 868: 864: 860: 843: 829: 826: 821: 818: 815: 812: 809: 805: 801: 791: 790: 789: 787: 783: 780:which maps Ω( 779: 776: 772: 767: 763: 758: 753: 751: 748: +  747: 744: =  743: 739: 735: 715: 709: 698: 695: 692: 679: 676: 673: 670: 667: 663: 659: 644: 636: 624: 623: 622: 620: 616: 612: 608: 603: 601: 597: 596: 591: 587: 583: 579: 575: 571: 567: 563: 559: 555: 551: 547: 543: 539: 535: 531: 523: 521: 519: 515: 514:Hopf problem, 511: 507: 503: 499: 495: 491: 487: 483: 479: 475: 470: 468: 450: 447: 444: 441: 438: 434: 430: 425: 422: 418: 409: 391: 388: 385: 382: 379: 375: 371: 368: 363: 360: 356: 347: 343: 339: 335: 327: 325: 323: 317: 313: 305: 301: 295: 291: 287: 280: 276: 271: 268:-rank tensor 263: 258: 256: 252: 248: 243: 237: 231: 223: 217: 213: 209: 204: 200: 196: 191: 189: 185: 169: 166: 160: 157: 154: 151: 144: 141: 140:vector bundle 125: 122: 119: 114: 110: 98: 94: 91: 88: 84: 80: 76: 73: 69: 61: 59: 57: 53: 48: 46: 42: 38: 37:tangent space 34: 30: 26: 22: 3759:Moving frame 3754:Morse theory 3744:Gauge theory 3536:Tensor field 3465:Closed/Exact 3444:Vector field 3412:Distribution 3353:Hypercomplex 3348:Quaternionic 3246: 3085:Vector field 3043:Smooth atlas 2939: 2933: 2907: 2887: 2867:. Springer. 2864: 2820: 2814: 2770: 2764: 2755: 2710: 2704: 2694: 2625: 2607: 2582: 2563: 2554: 2542: 2533: 2529: 2525: 2521: 2520:). Also, if 2517: 2513: 2509: 2501: 2497: 2495: 2490: 2486: 2482: 2478: 2474: 2470: 2466: 2464: 2458: 2453: 2449: 2444: 2440: 2436: 2432: 2426: 2422: 2418: 2414: 2410: 2403: 2399: 2395: 2391: 2387: 2383: 2376: 2372: 2368: 2364: 2360: 2355: 2351: 2347: 2343: 2339: 2335: 2331: 2327: 2322: 2318: 2310: 2306: 2302: 2294: 2290: 2286: 2282: 2275: 2268: 2266: 2256: 2252: 2244: 2237: 2234: 2231: 2137: 2129: 2125: 2121: 2119: 2111: 2105: 1879: 1875: 1871: 1867: 1863: 1859: 1857: 1671: 1669: 1509: 1505: 1501: 1497: 1495: 1490: 1482: 1478: 1474: 1463: 1459: 1455: 1452:neighborhood 1447: 1443: 1442:given point 1440: 1436: 1282: 1095: 976:identity map 973: 937: 933: 929: 925: 903: 785: 781: 777: 770: 765: 761: 755:As with any 754: 749: 745: 741: 737: 733: 731: 618: 604: 599: 594: 589: 585: 582:vector field 580:is called a 577: 573: 569: 565: 561: 557: 553: 549: 541: 537: 533: 529: 527: 513: 501: 493: 489: 481: 477: 471: 466: 407: 345: 341: 337: 333: 331: 315: 311: 303: 299: 289: 285: 278: 274: 269: 259: 250: 246: 241: 235: 229: 221: 215: 211: 207: 202: 198: 194: 192: 187: 92: 90:tensor field 78: 74: 71: 67: 65: 49: 24: 18: 3704:Levi-Civita 3694:Generalized 3666:Connections 3616:Lie algebra 3548:Volume form 3449:Vector flow 3422:Pushforward 3417:Lie bracket 3316:Lie algebra 3281:G-structure 3070:Pushforward 3050:Submanifold 2651:Chern class 2622:pure spinor 2610:Lie bracket 1468:holomorphic 546:eigenspaces 143:isomorphism 21:mathematics 3827:Stratifold 3785:Diffeology 3581:Associated 3382:Symplectic 3367:Riemannian 3296:Hyperbolic 3223:Submersion 3131:Hopf–Rinow 3065:Submersion 3060:Smooth map 2780:1708.01068 2686:References 2591:direct sum 1674:such that 1487:integrable 757:direct sum 518:Heinz Hopf 255:orientable 102:such that 83:linear map 56:Heinz Hopf 3709:Principal 3684:Ehresmann 3641:Subbundle 3631:Principal 3606:Fibration 3586:Cotangent 3458:Covectors 3311:Lie group 3291:Hermitian 3234:manifolds 3203:Immersion 3198:Foliation 3136:Noether's 3121:Frobenius 3116:De Rham's 3111:Darboux's 3002:Manifolds 2837:0003-486X 2797:119297359 2599:subbundle 2587:isotropic 2375:) form a 2202:¯ 2199:∂ 2171:¯ 2168:∂ 2159:∂ 2064:∂ 2060:− 2036:∂ 2014:− 1990:∂ 1971:− 1947:∂ 1894:− 1818:− 1695:− 1630:− 1551:− 1414:μ 1407:¯ 1397:∂ 1393:∂ 1385:− 1374:μ 1367:¯ 1357:∂ 1353:∂ 1339:μ 1331:∂ 1327:∂ 1311:μ 1303:∂ 1299:∂ 1263:μ 1255:∂ 1251:∂ 1246:− 1235:μ 1227:∂ 1223:∂ 1209:μ 1201:∂ 1197:∂ 1184:μ 1176:∂ 1172:∂ 1142:μ 1126:μ 1113:μ 1073:⋯ 1065:¯ 1062:∂ 1054:∂ 1045:∘ 1030:π 996:∑ 953:¯ 950:∂ 912:∂ 886:∘ 865:π 856:¯ 853:∂ 827:∘ 806:π 799:∂ 686:Ω 664:⨁ 633:Ω 506:octonions 472:The only 465:for even 435:δ 389:− 376:δ 372:− 270:pointwise 257:as well. 234:. But if 164:→ 155:: 123:− 3852:Category 3805:Orbifold 3800:K-theory 3790:Diffiety 3514:Pullback 3328:Oriented 3306:Kenmotsu 3286:Hadamard 3232:Types of 3181:Geodesic 3006:Glossary 2886:(1980). 2863:(2001). 2747:16578639 2636:See also 2601:and its 2576:subspace 2303:TM → T*M 2289:. Since 2267:Suppose 1504:; i.e., 940:)), and 904:so that 740:), with 406:for odd 328:Examples 232:) = (−1) 210: : 39:. Every 35:on each 3749:History 3732:Related 3646:Tangent 3624:)  3604:)  3571:Adjoint 3563:Bundles 3541:density 3439:Torsion 3405:Vectors 3397:Tensors 3380:)  3365:)  3361:,  3359:Pseudo− 3338:Poisson 3271:Finsler 3266:Fibered 3261:Contact 3259:)  3251:Complex 3249:)  3218:Section 2964:0058213 2956:2372495 2853:0088770 2845:1970051 2773:: 1–9. 2715:Bibcode 2536:) is a 928:,  784:) to Ω( 769:from Ω( 621:-forms 613:of the 609:out of 474:spheres 182:on the 3714:Vector 3699:Koszul 3679:Cartan 3674:Affine 3656:Vector 3651:Tensor 3636:Spinor 3626:Normal 3622:Stable 3576:Affine 3480:bundle 3432:bundle 3378:Almost 3301:Kähler 3257:Almost 3247:Almost 3241:Closed 3141:Sard's 3097:(list) 2962:  2954:  2914:  2894:  2871:  2851:  2843:  2835:  2795:  2745:  2738:224368 2735:  2504:is an 2251:; for 1489:'. If 1096:Every 516:after 266:(1, 1) 100:(1, 1) 97:degree 87:smooth 3822:Sheaf 3596:Fiber 3372:Rizza 3343:Prime 3174:Local 3164:Curve 3026:Atlas 2952:JSTOR 2841:JSTOR 2793:S2CID 2775:arXiv 2628:is a 2624:then 2439:) = ( 1471:atlas 556:and − 544:(the 536:into 228:(det 226:then 27:is a 23:, an 3689:Form 3591:Dual 3524:flow 3387:Tame 3363:Sub− 3276:Flat 3156:Maps 2912:ISBN 2892:ISBN 2869:ISBN 2833:ISSN 2743:PMID 2570:and 2489:has 2477:(•, 2469:and 2417:) = 2394:) = 2297:are 2293:and 2278:, a 2120:The 1870:and 1862:and 1473:for 936:+1, 572:and 540:and 480:and 298:GL(2 282:= −1 240:det 224:= −1 66:Let 54:and 3611:Jet 2944:doi 2825:doi 2785:doi 2733:PMC 2723:doi 2461:)). 1672:A=J 1454:of 548:of 348:): 344:≤ 2 310:GL( 308:to 201:is 193:If 95:of 77:on 19:In 3854:: 3602:Co 2960:MR 2958:. 2950:. 2940:75 2938:. 2928:; 2849:MR 2847:. 2839:. 2831:. 2821:65 2791:. 2783:. 2771:57 2769:. 2741:. 2731:. 2721:. 2711:55 2709:. 2703:. 2632:. 2583:TM 2547:. 2540:. 2532:, 2528:, 2518:Jv 2516:, 2448:)( 2425:, 2423:Ju 2413:, 2409:ω( 2404:Jv 2402:, 2390:, 2371:, 2367:, 2217:0. 1713:, 1481:. 971:. 752:. 586:TM 578:TM 574:TM 570:TM 566:TM 520:. 469:. 410:, 340:, 314:, 302:, 216:TM 214:→ 212:TM 190:. 47:. 3620:( 3600:( 3376:( 3357:( 3255:( 3245:( 3008:) 3004:( 2994:e 2987:t 2980:v 2966:. 2946:: 2920:. 2900:. 2877:. 2855:. 2827:: 2799:. 2787:: 2777:: 2749:. 2725:: 2717:: 2626:M 2564:M 2534:J 2530:ω 2526:M 2522:J 2514:u 2512:( 2510:ω 2502:J 2498:ω 2487:ω 2483:M 2479:J 2475:ω 2471:J 2467:ω 2459:u 2457:( 2454:ω 2450:φ 2445:g 2441:φ 2437:u 2435:( 2433:J 2429:) 2427:v 2421:( 2419:g 2415:v 2411:u 2406:) 2400:u 2398:( 2396:ω 2392:v 2388:u 2386:( 2384:g 2373:J 2369:ω 2365:g 2361:g 2356:g 2352:φ 2348:u 2346:( 2344:ω 2340:ω 2336:u 2332:i 2328:u 2326:( 2323:ω 2319:φ 2311:ω 2307:φ 2295:g 2291:ω 2287:J 2283:g 2276:ω 2269:M 2257:J 2253:C 2245:J 2238:S 2214:= 2209:2 2162:+ 2156:= 2153:d 2132:J 2130:N 2126:J 2114:A 2112:N 2091:. 2088:) 2083:m 2078:i 2074:A 2068:j 2055:m 2050:j 2046:A 2040:i 2032:( 2027:k 2022:m 2018:A 2009:k 2004:i 2000:A 1994:m 1984:m 1979:j 1975:A 1966:k 1961:j 1957:A 1951:m 1941:m 1936:i 1932:A 1928:= 1923:k 1918:j 1915:i 1911:) 1905:A 1901:N 1897:( 1880:A 1876:N 1872:Y 1868:X 1864:Y 1860:X 1842:. 1839:] 1836:Y 1833:J 1830:, 1827:X 1824:J 1821:[ 1815:) 1812:] 1809:Y 1806:J 1803:, 1800:X 1797:[ 1794:+ 1791:] 1788:Y 1785:, 1782:X 1779:J 1776:[ 1773:( 1770:J 1767:+ 1764:] 1761:Y 1758:, 1755:X 1752:[ 1749:= 1746:) 1743:Y 1740:, 1737:X 1734:( 1729:J 1725:N 1701:d 1698:I 1692:= 1687:2 1683:J 1654:. 1651:] 1648:Y 1645:A 1642:, 1639:X 1636:A 1633:[ 1627:) 1624:] 1621:Y 1618:A 1615:, 1612:X 1609:[ 1606:+ 1603:] 1600:Y 1597:, 1594:X 1591:A 1588:[ 1585:( 1582:A 1579:+ 1576:] 1573:Y 1570:, 1567:X 1564:[ 1559:2 1555:A 1548:= 1545:) 1542:Y 1539:, 1536:X 1533:( 1528:A 1524:N 1506:A 1502:M 1498:A 1491:J 1483:J 1479:J 1475:M 1464:J 1460:M 1456:p 1448:J 1444:p 1422:. 1404:z 1388:i 1382:= 1364:z 1348:J 1335:z 1322:i 1319:= 1307:z 1294:J 1259:x 1243:= 1231:y 1218:J 1205:y 1192:= 1180:x 1167:J 1138:y 1134:i 1131:+ 1122:x 1118:= 1109:z 1076:. 1070:+ 1057:+ 1051:= 1048:d 1040:s 1037:, 1034:r 1024:1 1021:+ 1018:q 1015:+ 1012:p 1009:= 1006:s 1003:+ 1000:r 992:= 989:d 938:q 934:p 930:q 926:p 889:d 881:1 878:+ 875:q 872:, 869:p 861:= 830:d 822:q 819:, 816:1 813:+ 810:p 802:= 786:M 782:M 778:d 771:M 766:q 764:, 762:p 750:q 746:p 742:r 738:M 734:M 716:. 713:) 710:M 707:( 702:) 699:q 696:, 693:p 690:( 680:r 677:= 674:q 671:+ 668:p 660:= 654:C 649:) 645:M 642:( 637:r 619:r 600:i 595:i 590:J 562:M 558:i 554:i 550:J 542:V 538:V 534:V 530:V 502:S 494:S 490:S 484:( 482:S 478:S 467:i 451:1 448:+ 445:j 442:, 439:i 431:= 426:j 423:i 419:J 408:i 392:1 386:j 383:, 380:i 369:= 364:j 361:i 357:J 346:n 342:j 338:i 334:R 318:) 316:C 312:n 306:) 304:R 300:n 290:M 286:p 279:p 275:J 251:M 247:n 242:J 236:M 230:J 222:J 208:J 203:n 199:M 195:M 170:M 167:T 161:M 158:T 152:J 126:1 120:= 115:2 111:J 93:J 79:M 75:J 68:M

Index

mathematics
smooth manifold
linear complex structure
tangent space
complex manifold
symplectic geometry
Charles Ehresmann
Heinz Hopf
linear map
smooth
tensor field
degree
vector bundle
isomorphism
tangent bundle
orientable
linear algebra
reduction of the structure group
algebraic topological
spheres
Borel & Serre (1953)
Riemann sphere
octonions
complex structure
Heinz Hopf
eigenspaces
vector field
i
differential forms
exterior powers

Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.