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Rademacher's theorem

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The one-dimensional case of Rademacher's theorem is a standard result in introductory texts on measure-theoretic analysis. In this context, it is natural to prove the more general statement that any single-variable function of
408:{\displaystyle \int _{\mathbf {R} ^{n}}{\frac {u(x+h\nu )-u(x)}{h}}\zeta (z)\,d{\mathcal {L}}^{n}(x)=-\int _{\mathbf {R} ^{n}}{\frac {\zeta (x)-\zeta (x-h\nu )}{h}}u(x)\,d{\mathcal {L}}^{n}(x).} 1186:. Proceedings of the Centre for Mathematical Analysis, Australian National University. Vol. 3. Canberra: Australian National University, Centre for Mathematical Analysis. 93:
zero. Differentiability here refers to infinitesimal approximability by a linear map, which in particular asserts the existence of the coordinate-wise partial derivatives.
610:, the proof of which can be modeled on that of the Rademacher theorem. In some special cases, the Rademacher theorem is even used as part of the proof. 602:
remain more subtle, since their usual definitions require more differentiability than is achieved by the Rademacher theorem. In the presence of
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fails to exist (which must be proved to be measurable), the latter condition is met due to the one-dimensional case of Rademacher's theorem.
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is differentiable almost everywhere. (This one-dimensional generalization of Rademacher's theorem fails to extend to higher dimensions.)
716: 477:-directional derivative almost everywhere (although perhaps on a smaller set). Hence, for any countable collection of unit vectors 1092:"Ăśber partielle und totale Differenzierbarkeit von Funktionen mehrerer Variabeln und ĂĽber die Transformation der Doppelintegrale" 1241: 1061: 920: 870: 1359: 667:
There is a version of Rademacher's theorem that holds for Lipschitz functions from a Euclidean space into an arbitrary
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holding in its standard form. With appropriate modification, this also extends to the more general Sobolev spaces
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to be dense in the unit sphere, it is possible to use the Lipschitz condition to prove the existence of
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Weakly differentiable functions. Sobolev spaces and functions of bounded variation
461:-tuple of partial derivatives) is guaranteed to exist almost everywhere; for each 149:
has (one-dimensional) Lebesgue measure zero. Considering in particular the set in
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The second step of Morrey's proof establishes the linear dependence of the
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One of the standard proofs of the general Rademacher theorem was found by
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is preserved under a bi-Lipschitz transformation of the domain, with the
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exists almost everywhere. This is a consequence of a special case of the
123:. The first step of the proof is to show that, for any fixed unit vector 1224:. Grundlehren der mathematischen Wissenschaften. Vol. 338. Berlin: 1174: 1109: 572: 145:
has Lebesgue measure zero if its restriction to every line parallel to
854: 599: 862: 36: 804: 1340:(Rademacher's theorem with a proof is on page 18 and further.) 1091: 776: 764: 740: 509:-directional derivative exist everywhere on the complement of 752: 648:. CalderĂłn's theorem is a relatively direct corollary of the 1335:
Lectures at the 14th Jyväskylä Summer School in August 2004
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Rademacher's theorem is also significant in the study of
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At this point in the proof, the gradient (defined as the
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Rademacher's theorem can be used to prove that, for any
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Real analysis. Modern techniques and their applications
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directional derivative everywhere on the complement of
1140:(Third edition of 1966 original ed.). New York: 189: 606:, second-order differentiability is achieved by the 638:is differentiable almost everywhere, provided that 541:Morrey's proof can also be put into the context of 513:, and are linked by the dot product. By selecting 407: 1346: 1042:Multiple integrals in the calculus of variations 498:of measure zero such that the gradient and each 851:Measure theory and fine properties of functions 430:in the above expression by the corresponding 180:. This is based upon the following identity: 845: 825: 794: 722: 452:fundamental lemma of calculus of variations 1086: 117:denote a Lipschitz-continuous function on 375: 266: 1325: 986: 829: 1216: 945: 895: 810: 758: 730: 706: 702: 1347: 1266: 1036: 798: 782: 770: 746: 734: 1173: 1132: 992:Lectures on analysis on metric spaces 726: 710: 621:proved the more general fact that if 1180:Lectures on geometric measure theory 13: 613: 426:can be applied to replace the two 418:Using the Lipschitz assumption on 382: 273: 96: 14: 1371: 1319: 675:instead of the usual derivative. 1328:"Lectures on Lipschitz Analysis" 650:Lebesgue differentiation theorem 598:. Higher-order concepts such as 306: 197: 552: 1222:Optimal transport. Old and new 399: 393: 372: 366: 354: 339: 330: 324: 290: 284: 263: 257: 245: 239: 230: 215: 1: 1273:Graduate Texts in Mathematics 849:; Gariepy, Ronald F. (2015). 690: 424:dominated convergence theorem 89:differentiable form a set of 446:, the same can be proved of 7: 1275:. Vol. 120. New York: 1267:Ziemer, William P. (1989). 955:John Wiley & Sons, Inc. 678: 660:is an element of the space 631:then every function in the 438:-directional derivative of 170:-directional derivative of 159:-directional derivative of 131:-directional derivative of 31:, states the following: If 10: 1376: 1360:Theorems in measure theory 994:. Universitext. New York: 625:is an open bounded set in 1285:10.1007/978-1-4612-1015-3 1234:10.1007/978-3-540-71050-9 1138:Real and complex analysis 1054:10.1007/978-3-540-69952-1 1004:10.1007/978-1-4613-0131-8 913:10.1007/978-3-642-62010-2 801:, pp. 243, 249, 281. 654:Sobolev embedding theorem 77:; that is, the points in 901:Geometric measure theory 826:Evans & Gariepy 2015 795:Evans & Gariepy 2015 723:Evans & Gariepy 2015 584:geometric measure theory 494:, there is a single set 113:. In the following, let 1326:Heinonen, Juha (2004). 543:generalized derivatives 1038:Morrey, Charles B. Jr. 409: 139:: a measurable set in 1097:Mathematische Annalen 410: 21:mathematical analysis 1142:McGraw-Hill Book Co. 733:, Theorem 10.8(ii); 673:metric differentials 428:difference quotients 187: 63:Lipschitz continuous 25:Rademacher's theorem 16:Mathematical theorem 1110:10.1007/BF01498415 947:Folland, Gerald B. 847:Evans, Lawrence C. 705:, Theorem 2.9.19; 608:Alexandrov theorem 547:approximate limits 405: 69:is differentiable 1243:978-3-540-71049-3 1063:978-3-540-69915-6 922:978-3-540-60656-7 872:978-1-4822-4238-6 361: 252: 104:bounded variation 71:almost everywhere 1367: 1338: 1332: 1314: 1263: 1213: 1185: 1170: 1129: 1088:Rademacher, Hans 1083: 1033: 983: 942: 897:Federer, Herbert 892: 833: 823: 814: 813:, Theorem 14.25. 808: 802: 792: 786: 785:, Theorem 3.1.7. 780: 774: 773:, Theorem 2.2.2. 768: 762: 756: 750: 749:, Theorem 3.1.6. 744: 738: 720: 714: 700: 685:Pansu derivative 663: 659: 647: 637: 630: 624: 619:Alberto CalderĂłn 588:rectifiable sets 578: 570: 563: 537: 529: 512: 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303: 299: 278: 272: 271: 270: 211: 209: 201: 196: 195: 194: 190: 188: 185: 184: 175: 171: 167: 160: 156: 150: 146: 140: 132: 128: 124: 118: 114: 99: 97:Sketch of proof 82: 78: 74: 66: 48: 40: 32: 29:Hans Rademacher 17: 12: 11: 5: 1373: 1363: 1362: 1357: 1355:Lipschitz maps 1343: 1342: 1321: 1320:External links 1318: 1316: 1315: 1293: 1264: 1242: 1214: 1192: 1171: 1149: 1130: 1104:(4): 340–359. 1084: 1062: 1034: 1012: 988:Heinonen, Juha 984: 962: 943: 921: 893: 871: 863:10.1201/b18333 842: 835: 834: 815: 803: 787: 775: 763: 761:, Section 3.1. 751: 739: 737:, Section 2.2. 715: 694: 692: 689: 688: 687: 680: 677: 615: 612: 596:normal vectors 592:tangent planes 554: 551: 525: 518: 503: 489: 482: 416: 415: 404: 401: 398: 395: 390: 384: 378: 374: 371: 368: 365: 360: 356: 353: 350: 347: 344: 341: 338: 335: 332: 329: 326: 323: 313: 308: 302: 298: 295: 292: 289: 286: 281: 275: 269: 265: 262: 259: 256: 251: 247: 244: 241: 238: 235: 232: 229: 226: 223: 220: 217: 214: 204: 199: 193: 137:Fubini theorem 111:Charles Morrey 98: 95: 27:, named after 15: 9: 6: 4: 3: 2: 1372: 1361: 1358: 1356: 1353: 1352: 1350: 1341: 1336: 1329: 1324: 1323: 1312: 1308: 1304: 1300: 1296: 1294:0-387-97017-7 1290: 1286: 1282: 1278: 1274: 1270: 1265: 1261: 1257: 1253: 1249: 1245: 1239: 1235: 1231: 1227: 1223: 1219: 1215: 1211: 1207: 1203: 1199: 1195: 1193:0-86784-429-9 1189: 1182: 1181: 1176: 1172: 1168: 1164: 1160: 1156: 1152: 1150:0-07-054234-1 1146: 1143: 1139: 1135: 1134:Rudin, Walter 1131: 1127: 1123: 1119: 1115: 1111: 1107: 1103: 1099: 1098: 1093: 1089: 1085: 1081: 1077: 1073: 1069: 1065: 1059: 1055: 1051: 1047: 1043: 1039: 1035: 1031: 1027: 1023: 1019: 1015: 1013:0-387-95104-0 1009: 1005: 1001: 997: 993: 989: 985: 981: 977: 973: 969: 965: 963:0-471-31716-0 959: 956: 952: 948: 944: 940: 936: 932: 928: 924: 918: 914: 910: 906: 902: 898: 894: 890: 886: 882: 878: 874: 868: 864: 860: 856: 852: 848: 844: 843: 841: 840: 831: 830:Heinonen 2001 827: 822: 820: 812: 807: 800: 796: 791: 784: 779: 772: 767: 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151: 141: 119: 108: 100: 86: 57: 53: 49: 42: 24: 18: 1175:Simon, Leon 799:Ziemer 1989 783:Morrey 1966 771:Ziemer 1989 747:Morrey 1966 735:Ziemer 1989 473:equals the 467:dot product 37:open subset 1349:Categories 1311:0692.46022 1260:1156.53003 1210:0546.49019 1167:0925.00005 1118:47.0243.01 1080:1213.49002 1030:0985.46008 980:0924.28001 939:0176.00801 889:1310.28001 727:Simon 1983 711:Rudin 1987 691:References 573:chain rule 155:where the 855:CRC Press 662:W(Ω) 636:W(Ω) 604:convexity 600:curvature 577:W(Ω) 569:W(Ω) 352:ν 346:− 337:ζ 334:− 322:ζ 301:∫ 297:− 255:ζ 234:− 228:ν 192:∫ 81:at which 1220:(2009). 1177:(1983). 1136:(1987). 1090:(1919). 1040:(1966). 990:(2001). 949:(1999). 899:(1969). 679:See also 450:via the 1303:1014685 1252:2459454 1202:0756417 1159:0924157 1126:1511935 1072:0202511 1022:1800917 972:1681462 931:0257325 881:3409135 839:Sources 65:, then 1309:  1301:  1291:  1258:  1250:  1240:  1208:  1200:  1190:  1165:  1157:  1147:  1124:  1116:  1078:  1070:  1060:  1028:  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Index

mathematical analysis
Hans Rademacher
open subset
R
Lipschitz continuous
almost everywhere
Lebesgue measure
bounded variation
Charles Morrey
Fubini theorem
dominated convergence theorem
difference quotients
fundamental lemma of calculus of variations
dot product
generalized derivatives
approximate limits
Sobolev space
chain rule
geometric measure theory
rectifiable sets
tangent planes
normal vectors
curvature
convexity
Alexandrov theorem
Alberto CalderĂłn
Sobolev space
Lebesgue differentiation theorem
Sobolev embedding theorem
metric space

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