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Category of metric spaces

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344: 240:. However, the product of an infinite set of metric spaces may not exist, because the distances in the base spaces may not have a supremum. That is, 470: 353: 415: 335: 249: 213: 192:
of their metric balls, and because of this alternative definition Aronszajn and Panitchpakdi named these spaces
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of its points, and assigns to each metric map the underlying set-theoretic function. This functor is
84: 52: 311:. The metric maps are both uniformly continuous and Lipschitz, with Lipschitz constant at most one. 121:
is a monomorphism and an epimorphism, but it is clearly not an isomorphism; this example shows that
95: 91: 41: 449: 320: 300: 411: 367: 285: 273: 260: 245: 225: 217: 126: 429: 405: 338: – category whose objects are topological spaces and whose morphisms are continuous maps 441: 383: 329: 277: 268: 196:. Any metric space has a smallest injective metric space into which it can be isometrically 169: 154: 114: 17: 299:
is not the only category whose objects are metric spaces; others include the category of
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of the spaces as its points; the distance in the product space is given by the
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between metric spaces that do not increase any pairwise distance) as its
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of two metric maps is again a metric map. It was first considered by
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as a category; they may also be defined intrinsically in terms of a
180:. Injective metric spaces were introduced and studied first by 332: – Category in mathematics where the objects are sets 232:
of the distances in the base spaces. That is, it is the
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Pages displaying wikidata descriptions as a fallback
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Pages displaying wikidata descriptions as a fallback
345:Category of topological spaces with base point 8: 430:"Six theorems about injective metric spaces" 272:assigns to each metric space the underlying 248:, but it is finitely complete. There is no 387: 106:, i.e. metric maps which are injective, 56: 404:(2009), "Category of metric spaces", 354:Category of topological vector spaces 7: 113:As an example, the inclusion of the 182:Aronszajn & Panitchpakdi (1956) 83:are the metric maps for which the 14: 51:. This is a category because the 200:, called its metric envelope or 410:, Springer-Verlag, p. 38, 323: – category in mathematics 224:is a metric space that has the 376:Pacific Journal of Mathematics 336:Category of topological spaces 301:uniformly continuous functions 1: 471:Categories in category theory 356: – Topological category 370:; Panitchpakdi, P. (1956), 110:, and distance-preserving. 492: 407:Encyclopedia of Distances 309:quasi-Lipschitz mappings 184:, prior to the study of 178:injective metric spaces 389:10.2140/pjm.1956.6.405 208:Products and functors 434:Comment. Math. Helv. 307:and the category of 220:of metric spaces in 141:metric space is the 305:Lipschitz functions 446:10.1007/BF02566944 398:Deza, Michel Marie 321:Category of groups 303:, the category of 292:Related categories 194:hyperconvex spaces 153:metric space is a 286:concrete category 261:forgetful functor 246:complete category 226:cartesian product 170:injective objects 127:balanced category 87:of the map has a 79:metric maps. The 483: 456: 420: 392: 391: 350: 341: 330:Category of sets 326: 280:, and therefore 115:rational numbers 491: 490: 486: 485: 484: 482: 481: 480: 476:Metric geometry 461: 460: 424: 418: 396: 366: 363: 348: 339: 324: 317: 294: 210: 155:terminal object 135: 65: 18:category theory 12: 11: 5: 489: 487: 479: 478: 473: 463: 462: 459: 458: 422: 416: 394: 382:(3): 405–439, 362: 359: 358: 357: 351: 342: 333: 327: 316: 313: 293: 290: 234:product metric 209: 206: 190:Helly property 143:initial object 134: 131: 64: 61: 13: 10: 9: 6: 4: 3: 2: 488: 477: 474: 472: 469: 468: 466: 455: 451: 447: 443: 439: 435: 431: 427: 426:Isbell, J. R. 423: 419: 417:9783642002342 413: 409: 408: 403: 399: 395: 390: 385: 381: 377: 373: 369: 368:Aronszajn, N. 365: 364: 360: 355: 352: 346: 343: 337: 334: 331: 328: 322: 319: 318: 314: 312: 310: 306: 302: 298: 291: 289: 287: 283: 279: 275: 271: 270: 265: 262: 257: 255: 251: 247: 243: 239: 235: 231: 227: 223: 219: 215: 207: 205: 203: 199: 195: 191: 187: 183: 179: 175: 171: 166: 164: 160: 156: 152: 148: 144: 140: 132: 130: 128: 124: 120: 116: 111: 109: 105: 101: 97: 93: 90: 86: 82: 78: 74: 70: 69:monomorphisms 62: 60: 58: 57:Isbell (1964) 54: 50: 46: 43: 39: 35: 31: 30:metric spaces 27: 23: 19: 440:(1): 65–76, 437: 433: 406: 379: 375: 296: 295: 281: 267: 263: 258: 253: 241: 221: 216:of a finite 211: 193: 185: 173: 167: 162: 159:zero objects 146: 136: 122: 119:real numbers 112: 100:isomorphisms 81:epimorphisms 72: 66: 21: 15: 402:Deza, Elena 176:are called 53:composition 38:metric maps 465:Categories 361:References 202:tight span 108:surjective 104:isometries 42:continuous 454:121857986 250:coproduct 244:is not a 236:with the 151:singleton 125:is not a 117:into the 77:injective 49:morphisms 45:functions 28:that has 428:(1964), 315:See also 278:faithful 238:sup norm 230:supremum 198:embedded 102:are the 75:are the 26:category 214:product 133:Objects 94:in the 34:objects 32:as its 452:  414:  149:; any 98:. The 85:domain 63:Arrows 450:S2CID 284:is a 139:empty 96:range 92:image 89:dense 24:is a 412:ISBN 259:The 212:The 168:The 137:The 67:The 36:and 442:doi 384:doi 297:Met 282:Met 274:set 269:Set 264:Met 254:Met 252:in 242:Met 222:Met 218:set 186:Met 174:Met 172:in 163:Met 161:in 147:Met 145:of 123:Met 73:Met 71:in 22:Met 16:In 467:: 448:, 438:39 436:, 432:, 400:; 378:, 374:, 288:. 266:→ 256:. 204:. 165:. 129:. 59:. 20:, 457:. 444:: 421:. 393:. 386:: 380:6 40:(

Index

category theory
category
metric spaces
objects
metric maps
continuous
functions
morphisms
composition
Isbell (1964)
monomorphisms
injective
epimorphisms
domain
dense
image
range
isomorphisms
isometries
surjective
rational numbers
real numbers
balanced category
empty
initial object
singleton
terminal object
zero objects
injective objects
injective metric spaces

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