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and Lipschitz continuous maps, and it is free in the category of metric spaces bounded by 1 and short maps. That is, any function from a discrete metric space to another bounded metric space is Lipschitz continuous, and any function from a discrete metric space to another metric space bounded by 1 is
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The underlying uniformity on a discrete metric space is the discrete uniformity, and the underlying topology on a discrete uniform space is the discrete topology. Thus, the different notions of discrete space are compatible with one another. On the other hand, the underlying topology of a
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A discrete structure is often used as the "default structure" on a set that doesn't carry any other natural topology, uniformity, or metric; discrete structures can often be used as "extreme" examples to test particular suppositions. For example, any
589: 919: 3880:(or differentiable or analytic manifold) is nothing but a discrete and countable topological space (an uncountable discrete space is not second-countable). We can therefore view any discrete countable group as a 0-dimensional 2026: 3455:
of topological spaces and continuous maps or in the category of uniform spaces and uniformly continuous maps. These facts are examples of a much broader phenomenon, in which discrete structures are usually free on sets.
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by giving it the discrete topology, implying that theorems about topological groups apply to all groups. Indeed, analysts may refer to the ordinary, non-topological groups studied by algebraists as "
1921: 1662: 2540: 1407: 490: 2958: 3019: 1224: 1860: 1345: 1186: 3157: 374: 3463:. Certainly the discrete metric space is free when the morphisms are all uniformly continuous maps or all continuous maps, but this says nothing interesting about the metric 834: 3621: 1319: 1070: 3801: 3385: 1587: 1125: 941: 2510: 2293: 973: 2130: 3342: 2183: 1517: 806: 750: 714: 656: 624: 400: 2322: 4018: 3942: 2465: 1099: 2252: 1482: 1290: 1041: 2432: 1443: 465: 1543: 2872: 2405: 3845: 3821: 3749: 3729: 3705: 3641: 3591: 3567: 3541: 3521: 3501: 3449: 3425: 3316: 3296: 3276: 3107: 3043: 2892: 2849: 2829: 2530: 2382: 2362: 2342: 2226: 2203: 2150: 1808: 1248: 1145: 999: 770: 485: 424: 320: 281: 253: 229: 196: 843: 3954: 1926: 3475:; however, these categories don't have free objects (on more than one element). However, the discrete metric space is free in the category of 2031: 1589:
The topology underlying a metric space can be discrete, without the metric being uniformly discrete: for example the usual metric on the set
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With metric spaces, things are more complicated, because there are several categories of metric spaces, depending on what is chosen for the
3646: 3467:, only the uniform or topological structure. Categories more relevant to the metric structure can be found by limiting the morphisms to 4109:
Pleasants, Peter A.B. (2000). "Designer quasicrystals: Cut-and-project sets with pre-assigned properties". In Baake, Michael (ed.).
1592: 1783:{\textstyle X=\left\{2^{-n}:n\in \mathbb {N} _{0}\right\}=\left\{1,{\frac {1}{2}},{\frac {1}{4}},{\frac {1}{8}},\dots \right\},} 1865: 4217: 100: 72: 1350: 79: 4179: 4122: 119: 2907: 53: 17: 403: 86: 3400: 57: 4114: 2967: 3025:
and hence not discrete as a uniform space. Nevertheless, it is discrete as a topological space. We say that
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and the space itself). Where the discrete topology is initial or free, the indiscrete topology is final or
1191: 68: 4254: 4166: 4025: 1813: 584:{\displaystyle \rho (x,y)={\begin{cases}1&{\text{if}}\ x\neq y,\\0&{\text{if}}\ x=y\end{cases}}} 3981: 3970: 1324: 1150: 3112: 329: 4249: 3545: 811: 3602: 520: 3597: 3570: 1295: 1046: 155: 3786: 3368: 1548: 1104: 924: 3072: 2470: 2257: 946: 163: 46: 2099: 4161: 3958: 3950: 3464: 3321: 3217: 2831:
bigger than any given real number, it follows that there will always be at least two points in
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non-discrete uniform or metric space can be discrete; an example is the metric space
979: 773: 141: 4193: 4128: 4089: 4047: 4041: 3888: 3083: 2021:{\displaystyle \varepsilon ={\tfrac {1}{2}}\left(x_{n}-x_{n+1}\right)=2^{-(n+2)}.} 4205: 4185: 4171: 4029: 3452: 3235: 3171: 808:
induces on it) whose topology is equal to the discrete topology. For example, if
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Any function from a discrete topological space to another topological space is
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Combining the above two facts, every discrete uniform or metric space is
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expansion. A product of countably infinite copies of the discrete space
2089:{\displaystyle \left(x_{n}-\varepsilon ,x_{n}+\varepsilon \right)\cap X} 3946: 3912: 3760: 3185: 260: 4055: 3881: 3472: 3356: 3221: 2961: 3680:{\displaystyle \tau ={\mathcal {U}}\cup \left\{\varnothing \right\}} 1790:
consider this set using the usual metric on the real numbers. Then,
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are open, which is the case if and only if it doesn't contain any
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cannot be uniformly discrete. To see why, suppose there exists an
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Proof that a discrete space is not necessarily uniformly discrete
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from each other in a certain sense. The discrete topology is the
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Since the intersection of an open set of the real numbers and
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A discrete space is separable if and only if it is countable.
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Every discrete space is metrizable (by the discrete metric).
3021:). This is not the discrete metric; also, this space is not 1646:{\displaystyle \left\{2^{-n}:n\in \mathbb {N} _{0}\right\}.} 4046:
In some ways, the opposite of the discrete topology is the
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on the product. Such a homeomorphism is given by using
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Every discrete topological space satisfies each of the
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It suffices to show that there are at least two points
4113:. CRM Monograph Series. Vol. 13. Providence, RI: 3771:
closed but (in contrast to the discrete topology) the
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in the discrete topology so that in particular, every
4139: 4054:), which has the fewest possible open sets (just the 3994: 3918: 3833: 3809: 3789: 3737: 3717: 3693: 3649: 3629: 3605: 3579: 3555: 3529: 3509: 3489: 3437: 3413: 3371: 3324: 3304: 3284: 3264: 3115: 3095: 3031: 2970: 2910: 2880: 2857: 2837: 2817: 2538: 2518: 2473: 2440: 2413: 2390: 2370: 2350: 2330: 2301: 2260: 2234: 2214: 2191: 2158: 2138: 2102: 2034: 1929: 1868: 1816: 1796: 1595: 1551: 1525: 1490: 1464: 1419: 1353: 1327: 1298: 1263: 1236: 1194: 1153: 1133: 1107: 1078: 1049: 1014: 987: 949: 927: 846: 814: 782: 758: 726: 690: 632: 597: 493: 473: 453: 412: 382: 332: 308: 269: 241: 217: 184: 158:
topology that can be given on a set. Every subset is
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or similar structure, one in which the points form a
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A finite space is metrizable only if it is discrete.
3071:A topological space is discrete if and only if its 60:. Unsourced material may be challenged and removed. 4012: 3936: 3839: 3815: 3795: 3743: 3723: 3699: 3679: 3635: 3615: 3585: 3561: 3535: 3515: 3495: 3443: 3419: 3379: 3336: 3310: 3290: 3270: 3151: 3101: 3037: 3013: 2952: 2886: 2866: 2843: 2823: 2801: 2524: 2504: 2459: 2426: 2399: 2376: 2356: 2336: 2316: 2287: 2246: 2220: 2197: 2177: 2152:is open for the induced topology, it follows that 2144: 2124: 2088: 2020: 1915: 1854: 1802: 1782: 1645: 1581: 1537: 1511: 1476: 1437: 1401: 1339: 1313: 1284: 1242: 1218: 1180: 1139: 1119: 1093: 1064: 1035: 993: 967: 935: 913: 828: 800: 764: 744: 708: 650: 618: 583: 479: 459: 418: 394: 368: 314: 275: 247: 223: 190: 4236: 2851:that are closer to each other than any positive 1402:{\displaystyle x,y\in S,d(x,y)>\varepsilon .} 434:if it is equipped with its discrete uniformity. 4212:. Mineola, New York: Dover Publications, Inc. 4020:is central to the topological approach to the 3298:is a set carrying the discrete topology, then 2953:{\displaystyle X=\{n^{-1}:n\in \mathbb {N} \}} 291:if it is equipped with its discrete topology; 4156: 4007: 3995: 3931: 3919: 3344:(the projection map is the desired covering) 3146: 3116: 2947: 2917: 2172: 2159: 2116: 2103: 1213: 1207: 962: 956: 363: 333: 2407:Since the distance between adjacent points 3973:is necessarily a discrete subspace of its 3191:Every discrete uniform or metric space is 1862:we can surround it with the open interval 1810:is a discrete space, since for each point 4108: 3373: 3170:; in particular, every discrete space is 2943: 1701: 1625: 929: 822: 120:Learn how and when to remove this message 4204: 4145: 4111:Directions in mathematical quasicrystals 4070:an indiscrete space is continuous, etc. 3109:is discrete if and only if the diagonal 3014:{\displaystyle d(x,y)=\left|x-y\right|} 14: 4237: 3907:, with the homeomorphism given by the 3483:Going the other direction, a function 3241:Any two discrete spaces with the same 140:is a particularly simple example of a 2096:is therefore trivially the singleton 1219:{\displaystyle y\in S\setminus \{x\}} 4035: 3854: 3763:, but never both. Said differently, 58:adding citations to reliable sources 29: 3543:is continuous if and only if it is 2384:that are closer to each other than 2185:is open so singletons are open and 24: 4170:(2nd ed.). Berlin, New York: 3658: 3643:can be associated with a topology 3608: 3391:) that is discrete is necessarily 3234:Every non-empty discrete space is 3068:of a discrete space is equal to 0. 1855:{\displaystyle x_{n}=2^{-n}\in X,} 25: 4266: 3851:closed in the discrete topology. 3670: 3549:in the sense that every point in 1340:{\displaystyle \varepsilon >0} 1204: 1181:{\displaystyle d(x,y)>\delta } 3953:to the Cantor set if we use the 3895:copies of the discrete space of 3152:{\displaystyle \{(x,x):x\in X\}} 2960:(with metric inherited from the 2532:that satisfies this inequality: 684:of some given topological space 369:{\displaystyle \{(x,x):x\in X\}} 34: 4028:), which is a weak form of the 3205:Every discrete metric space is 1347:such that for any two distinct 829:{\displaystyle Y:=\mathbb {R} } 45:needs additional citations for 4102: 3616:{\displaystyle {\mathcal {U}}} 3407:. That is, the discrete space 3131: 3119: 2986: 2974: 2782: 2776: 2731: 2725: 2563: 2551: 2494: 2482: 2276: 2264: 2010: 1998: 1907: 1869: 1567: 1555: 1432: 1420: 1387: 1375: 1276: 1264: 1169: 1157: 1027: 1015: 795: 783: 739: 727: 703: 691: 645: 633: 509: 497: 348: 336: 173: 13: 1: 4115:American Mathematical Society 4095: 2898: 1314:{\displaystyle S\subseteq X,} 1065:{\displaystyle S\subseteq X,} 3796:{\displaystyle \varnothing } 3380:{\displaystyle \mathbb {R} } 3365:Any topological subspace of 3202:if and only if it is finite. 1582:{\displaystyle d(x,y)>r.} 1120:{\displaystyle \delta >0} 936:{\displaystyle \mathbb {R} } 322:is defined by letting every 231:is defined by letting every 7: 4167:Counterexamples in Topology 4073: 4026:Boolean prime ideal theorem 3278:is a topological space and 2894:is not uniformly discrete. 2505:{\displaystyle 2^{-(n+1)},} 2288:{\displaystyle d(x,y)>r} 968:{\displaystyle S\cup \{0\}} 10: 4271: 4039: 3988:properties of products of 3982:foundations of mathematics 3971:locally injective function 3086:for the discrete topology. 2125:{\displaystyle \{x_{n}\}.} 287:discrete topological space 170:in the discrete topology. 3503:from a topological space 3359:is the discrete topology. 3337:{\displaystyle X\times Y} 2811:Since there is always an 2178:{\displaystyle \{x_{n}\}} 1512:{\displaystyle x,y\in E,} 1226:; such a set consists of 801:{\displaystyle (Y,\tau )} 745:{\displaystyle (Y,\tau )} 709:{\displaystyle (Y,\tau )} 651:{\displaystyle (X,\rho )} 619:{\displaystyle x,y\in X.} 395:{\displaystyle X\times X} 27:Type of topological space 3711:non-empty proper subset 3227:Every discrete space is 3212:Every discrete space is 2317:{\displaystyle x\neq y.} 4013:{\displaystyle \{0,1\}} 3945:is homeomorphic to the 3937:{\displaystyle \{0,1\}} 3864:can be considered as a 3707:with the property that 2460:{\displaystyle x_{n+1}} 1094:{\displaystyle x\in S,} 4162:Seebach, J. Arthur Jr. 4014: 3951:uniformly homeomorphic 3938: 3841: 3817: 3797: 3779:open and closed (i.e. 3745: 3725: 3701: 3681: 3637: 3617: 3587: 3563: 3537: 3517: 3497: 3445: 3421: 3381: 3338: 3312: 3292: 3272: 3153: 3103: 3082:The singletons form a 3047:topologically discrete 3039: 3015: 2954: 2888: 2868: 2845: 2825: 2803: 2526: 2506: 2461: 2428: 2401: 2378: 2358: 2338: 2318: 2289: 2248: 2247:{\displaystyle r>0} 2222: 2199: 2179: 2146: 2126: 2090: 2022: 1917: 1856: 1804: 1784: 1647: 1583: 1539: 1513: 1478: 1477:{\displaystyle r>0} 1439: 1403: 1341: 1315: 1286: 1285:{\displaystyle (X,d),} 1244: 1220: 1182: 1141: 1121: 1095: 1066: 1037: 1036:{\displaystyle (X,d),} 995: 969: 937: 915: 830: 802: 766: 746: 710: 652: 620: 585: 481: 461: 430:discrete uniform space 420: 396: 370: 316: 277: 249: 225: 192: 146:discontinuous sequence 4210:Topology for Analysis 4015: 3939: 3842: 3818: 3798: 3746: 3726: 3702: 3682: 3638: 3618: 3588: 3564: 3538: 3518: 3498: 3477:bounded metric spaces 3446: 3422: 3382: 3355:as a subspace of the 3339: 3318:is evenly covered by 3313: 3293: 3273: 3220:if and only if it is 3174:, that is, separated. 3154: 3104: 3066:topological dimension 3040: 3016: 2955: 2889: 2869: 2846: 2826: 2804: 2527: 2507: 2462: 2429: 2427:{\displaystyle x_{n}} 2402: 2379: 2359: 2339: 2319: 2290: 2249: 2223: 2205:is a discrete space. 2200: 2180: 2147: 2127: 2091: 2023: 1918: 1857: 1805: 1785: 1648: 1584: 1540: 1514: 1479: 1440: 1438:{\displaystyle (E,d)} 1404: 1342: 1316: 1287: 1245: 1221: 1183: 1142: 1122: 1096: 1067: 1038: 996: 970: 938: 916: 831: 803: 767: 747: 711: 662:discrete metric space 653: 621: 586: 482: 462: 460:{\displaystyle \rho } 421: 397: 371: 317: 278: 250: 226: 193: 4208:(17 October 2008) . 4066:a topological space 3992: 3916: 3831: 3807: 3787: 3735: 3715: 3691: 3647: 3627: 3603: 3577: 3553: 3527: 3523:to a discrete space 3507: 3487: 3469:Lipschitz continuous 3435: 3411: 3405:uniformly continuous 3369: 3322: 3302: 3282: 3262: 3229:totally disconnected 3177:A discrete space is 3113: 3093: 3029: 2968: 2908: 2878: 2855: 2835: 2815: 2536: 2516: 2471: 2438: 2411: 2388: 2368: 2348: 2328: 2299: 2258: 2232: 2212: 2189: 2156: 2136: 2100: 2032: 1927: 1866: 1814: 1794: 1663: 1593: 1549: 1523: 1488: 1462: 1417: 1351: 1325: 1296: 1261: 1234: 1192: 1151: 1131: 1105: 1076: 1047: 1012: 985: 947: 925: 844: 812: 780: 756: 724: 718:topological subspace 688: 630: 595: 491: 471: 451: 410: 380: 330: 306: 267: 239: 215: 182: 54:improve this article 4117:. pp. 95–141. 4052:indiscrete topology 4024:(equivalently, the 3623:on a non-empty set 3077:accumulation points 3055:metrically discrete 2512:we need to find an 1538:{\displaystyle x=y} 1484:such that, for any 298:discrete uniformity 148:, meaning they are 4255:Topological spaces 4158:Steen, Lynn Arthur 4085:List of topologies 4010: 3955:product uniformity 3934: 3909:continued fraction 3905:irrational numbers 3893:countably infinite 3876:. A 0-dimensional 3874:Pontryagin duality 3837: 3813: 3793: 3741: 3721: 3697: 3677: 3633: 3613: 3583: 3559: 3533: 3513: 3493: 3441: 3417: 3389:Euclidean topology 3377: 3334: 3308: 3288: 3268: 3149: 3099: 3051:uniformly discrete 3035: 3011: 2950: 2884: 2867:{\displaystyle r,} 2864: 2841: 2821: 2799: 2797: 2522: 2502: 2457: 2424: 2400:{\displaystyle r.} 2397: 2374: 2354: 2334: 2314: 2285: 2244: 2218: 2195: 2175: 2142: 2122: 2086: 2018: 1946: 1913: 1852: 1800: 1780: 1657: 1643: 1579: 1535: 1509: 1474: 1451:if there exists a 1448:uniformly discrete 1435: 1399: 1337: 1311: 1282: 1252:uniformly discrete 1240: 1216: 1178: 1137: 1117: 1101:there exists some 1091: 1062: 1033: 991: 965: 933: 911: 898: 883: 868: 838:Euclidean topology 826: 798: 772:together with the 762: 742: 706: 648: 616: 581: 576: 477: 457: 416: 392: 366: 312: 273: 245: 221: 188: 4219:978-0-486-46903-4 4062:: every function 4050:(also called the 4036:Indiscrete spaces 4022:ultrafilter lemma 3961:of numbers. (See 3866:topological group 3855:Examples and uses 3840:{\displaystyle X} 3823:. In comparison, 3816:{\displaystyle X} 3775:subsets that are 3744:{\displaystyle X} 3724:{\displaystyle S} 3700:{\displaystyle X} 3636:{\displaystyle X} 3586:{\displaystyle f} 3562:{\displaystyle Y} 3536:{\displaystyle X} 3516:{\displaystyle Y} 3496:{\displaystyle f} 3444:{\displaystyle X} 3420:{\displaystyle X} 3349:subspace topology 3311:{\displaystyle X} 3291:{\displaystyle Y} 3271:{\displaystyle X} 3216:; it is moreover 3168:separation axioms 3102:{\displaystyle X} 3038:{\displaystyle X} 2887:{\displaystyle X} 2844:{\displaystyle X} 2824:{\displaystyle n} 2525:{\displaystyle n} 2377:{\displaystyle X} 2357:{\displaystyle y} 2337:{\displaystyle x} 2221:{\displaystyle X} 2198:{\displaystyle X} 2145:{\displaystyle X} 2028:The intersection 1945: 1803:{\displaystyle X} 1764: 1751: 1738: 1655: 1243:{\displaystyle S} 1140:{\displaystyle x} 994:{\displaystyle S} 897: 882: 867: 774:subspace topology 765:{\displaystyle Y} 680:discrete subspace 564: 560: 535: 531: 480:{\displaystyle X} 419:{\displaystyle X} 315:{\displaystyle X} 276:{\displaystyle X} 248:{\displaystyle X} 224:{\displaystyle X} 207:discrete topology 191:{\displaystyle X} 142:topological space 130: 129: 122: 104: 16:(Redirected from 4262: 4250:General topology 4231: 4206:Wilansky, Albert 4201: 4149: 4143: 4137: 4136: 4106: 4090:Taxicab geometry 4048:trivial topology 4042:Trivial topology 4019: 4017: 4016: 4011: 3959:ternary notation 3943: 3941: 3940: 3935: 3903:to the space of 3846: 3844: 3843: 3838: 3822: 3820: 3819: 3814: 3802: 3800: 3799: 3794: 3750: 3748: 3747: 3742: 3730: 3728: 3727: 3722: 3706: 3704: 3703: 3698: 3686: 3684: 3683: 3678: 3676: 3662: 3661: 3642: 3640: 3639: 3634: 3622: 3620: 3619: 3614: 3612: 3611: 3592: 3590: 3589: 3584: 3568: 3566: 3565: 3560: 3546:locally constant 3542: 3540: 3539: 3534: 3522: 3520: 3519: 3514: 3502: 3500: 3499: 3494: 3450: 3448: 3447: 3442: 3426: 3424: 3423: 3418: 3387:(with its usual 3386: 3384: 3383: 3378: 3376: 3343: 3341: 3340: 3335: 3317: 3315: 3314: 3309: 3297: 3295: 3294: 3289: 3277: 3275: 3274: 3269: 3218:second-countable 3158: 3156: 3155: 3150: 3108: 3106: 3105: 3100: 3089:A uniform space 3044: 3042: 3041: 3036: 3020: 3018: 3017: 3012: 3010: 3006: 2959: 2957: 2956: 2951: 2946: 2932: 2931: 2893: 2891: 2890: 2885: 2873: 2871: 2870: 2865: 2850: 2848: 2847: 2842: 2830: 2828: 2827: 2822: 2808: 2806: 2805: 2800: 2798: 2772: 2771: 2721: 2720: 2688: 2684: 2683: 2664: 2663: 2650: 2649: 2627: 2626: 2607: 2606: 2567: 2566: 2531: 2529: 2528: 2523: 2511: 2509: 2508: 2503: 2498: 2497: 2466: 2464: 2463: 2458: 2456: 2455: 2433: 2431: 2430: 2425: 2423: 2422: 2406: 2404: 2403: 2398: 2383: 2381: 2380: 2375: 2363: 2361: 2360: 2355: 2343: 2341: 2340: 2335: 2323: 2321: 2320: 2315: 2294: 2292: 2291: 2286: 2253: 2251: 2250: 2245: 2227: 2225: 2224: 2219: 2204: 2202: 2201: 2196: 2184: 2182: 2181: 2176: 2171: 2170: 2151: 2149: 2148: 2143: 2131: 2129: 2128: 2123: 2115: 2114: 2095: 2093: 2092: 2087: 2079: 2075: 2068: 2067: 2049: 2048: 2027: 2025: 2024: 2019: 2014: 2013: 1986: 1982: 1981: 1980: 1962: 1961: 1947: 1938: 1922: 1920: 1919: 1914: 1900: 1899: 1881: 1880: 1861: 1859: 1858: 1853: 1842: 1841: 1826: 1825: 1809: 1807: 1806: 1801: 1789: 1787: 1786: 1781: 1776: 1772: 1765: 1757: 1752: 1744: 1739: 1731: 1715: 1711: 1710: 1709: 1704: 1689: 1688: 1652: 1650: 1649: 1644: 1639: 1635: 1634: 1633: 1628: 1613: 1612: 1588: 1586: 1585: 1580: 1544: 1542: 1541: 1536: 1518: 1516: 1515: 1510: 1483: 1481: 1480: 1475: 1457: 1456: 1444: 1442: 1441: 1436: 1408: 1406: 1405: 1400: 1346: 1344: 1343: 1338: 1321:if there exists 1320: 1318: 1317: 1312: 1291: 1289: 1288: 1283: 1249: 1247: 1246: 1241: 1225: 1223: 1222: 1217: 1187: 1185: 1184: 1179: 1146: 1144: 1143: 1138: 1126: 1124: 1123: 1118: 1100: 1098: 1097: 1092: 1071: 1069: 1068: 1063: 1042: 1040: 1039: 1034: 1000: 998: 997: 992: 974: 972: 971: 966: 942: 940: 939: 934: 932: 920: 918: 917: 912: 910: 906: 899: 890: 884: 875: 869: 860: 835: 833: 832: 827: 825: 807: 805: 804: 799: 771: 769: 768: 763: 751: 749: 748: 743: 715: 713: 712: 707: 682: 681: 664: 663: 657: 655: 654: 649: 625: 623: 622: 617: 590: 588: 587: 582: 580: 579: 562: 561: 558: 533: 532: 529: 486: 484: 483: 478: 466: 464: 463: 458: 446: 445: 432: 431: 425: 423: 422: 417: 401: 399: 398: 393: 375: 373: 372: 367: 326:of the diagonal 321: 319: 318: 313: 300: 299: 289: 288: 282: 280: 279: 274: 259:(and hence also 254: 252: 251: 246: 230: 228: 227: 222: 209: 208: 197: 195: 194: 189: 164:singleton subset 125: 118: 114: 111: 105: 103: 69:"Discrete space" 62: 38: 30: 21: 4270: 4269: 4265: 4264: 4263: 4261: 4260: 4259: 4235: 4234: 4220: 4182: 4172:Springer-Verlag 4153: 4152: 4144: 4140: 4125: 4107: 4103: 4098: 4076: 4044: 4038: 4030:axiom of choice 3993: 3990: 3989: 3984:, the study of 3917: 3914: 3913: 3897:natural numbers 3870:discrete groups 3857: 3832: 3829: 3828: 3808: 3805: 3804: 3788: 3785: 3784: 3767:subset is open 3736: 3733: 3732: 3716: 3713: 3712: 3692: 3689: 3688: 3666: 3657: 3656: 3648: 3645: 3644: 3628: 3625: 3624: 3607: 3606: 3604: 3601: 3600: 3578: 3575: 3574: 3554: 3551: 3550: 3528: 3525: 3524: 3508: 3505: 3504: 3488: 3485: 3484: 3436: 3433: 3432: 3412: 3409: 3408: 3372: 3370: 3367: 3366: 3323: 3320: 3319: 3303: 3300: 3299: 3283: 3280: 3279: 3263: 3260: 3259: 3236:second category 3214:first-countable 3200:totally bounded 3114: 3111: 3110: 3094: 3091: 3090: 3030: 3027: 3026: 2996: 2992: 2969: 2966: 2965: 2942: 2924: 2920: 2909: 2906: 2905: 2901: 2896: 2879: 2876: 2875: 2856: 2853: 2852: 2836: 2833: 2832: 2816: 2813: 2812: 2796: 2795: 2785: 2767: 2763: 2751: 2750: 2734: 2716: 2712: 2706: 2705: 2689: 2676: 2672: 2668: 2659: 2655: 2652: 2651: 2639: 2635: 2628: 2619: 2615: 2612: 2611: 2596: 2592: 2585: 2579: 2578: 2568: 2547: 2543: 2539: 2537: 2534: 2533: 2517: 2514: 2513: 2478: 2474: 2472: 2469: 2468: 2445: 2441: 2439: 2436: 2435: 2418: 2414: 2412: 2409: 2408: 2389: 2386: 2385: 2369: 2366: 2365: 2349: 2346: 2345: 2329: 2326: 2325: 2300: 2297: 2296: 2259: 2256: 2255: 2233: 2230: 2229: 2213: 2210: 2209: 2190: 2187: 2186: 2166: 2162: 2157: 2154: 2153: 2137: 2134: 2133: 2110: 2106: 2101: 2098: 2097: 2063: 2059: 2044: 2040: 2039: 2035: 2033: 2030: 2029: 1994: 1990: 1970: 1966: 1957: 1953: 1952: 1948: 1936: 1928: 1925: 1924: 1895: 1891: 1876: 1872: 1867: 1864: 1863: 1834: 1830: 1821: 1817: 1815: 1812: 1811: 1795: 1792: 1791: 1756: 1743: 1730: 1723: 1719: 1705: 1700: 1699: 1681: 1677: 1676: 1672: 1664: 1661: 1660: 1629: 1624: 1623: 1605: 1601: 1600: 1596: 1594: 1591: 1590: 1550: 1547: 1546: 1524: 1521: 1520: 1519:one has either 1489: 1486: 1485: 1463: 1460: 1459: 1454: 1453: 1418: 1415: 1414: 1413:A metric space 1411: 1352: 1349: 1348: 1326: 1323: 1322: 1297: 1294: 1293: 1262: 1259: 1258: 1235: 1232: 1231: 1228:isolated points 1193: 1190: 1189: 1152: 1149: 1148: 1132: 1129: 1128: 1106: 1103: 1102: 1077: 1074: 1073: 1048: 1045: 1044: 1013: 1010: 1009: 986: 983: 982: 948: 945: 944: 928: 926: 923: 922: 888: 873: 858: 857: 853: 845: 842: 841: 821: 813: 810: 809: 781: 778: 777: 757: 754: 753: 725: 722: 721: 689: 686: 685: 679: 678: 670:isolated points 661: 660: 631: 628: 627: 596: 593: 592: 575: 574: 557: 555: 549: 548: 528: 526: 516: 515: 492: 489: 488: 472: 469: 468: 452: 449: 448: 440: 439: 429: 428: 411: 408: 407: 381: 378: 377: 331: 328: 327: 307: 304: 303: 297: 296: 286: 285: 268: 265: 264: 240: 237: 236: 216: 213: 212: 206: 205: 183: 180: 179: 176: 126: 115: 109: 106: 63: 61: 51: 39: 28: 23: 22: 18:Discrete metric 15: 12: 11: 5: 4268: 4258: 4257: 4252: 4247: 4233: 4232: 4218: 4202: 4180: 4151: 4150: 4138: 4123: 4100: 4099: 4097: 4094: 4093: 4092: 4087: 4082: 4075: 4072: 4040:Main article: 4037: 4034: 4009: 4006: 4003: 4000: 3997: 3949:; and in fact 3933: 3930: 3927: 3924: 3921: 3856: 3853: 3836: 3826: 3812: 3792: 3778: 3774: 3766: 3754: 3740: 3720: 3710: 3696: 3675: 3672: 3669: 3665: 3660: 3655: 3652: 3632: 3610: 3582: 3558: 3532: 3512: 3492: 3440: 3416: 3397: 3396: 3375: 3363: 3360: 3345: 3333: 3330: 3327: 3307: 3287: 3267: 3256: 3253: 3250: 3239: 3232: 3225: 3210: 3203: 3196: 3189: 3182:if and only if 3175: 3164: 3148: 3145: 3142: 3139: 3136: 3133: 3130: 3127: 3124: 3121: 3118: 3098: 3087: 3080: 3069: 3060:Additionally: 3034: 3009: 3005: 3002: 2999: 2995: 2991: 2988: 2985: 2982: 2979: 2976: 2973: 2949: 2945: 2941: 2938: 2935: 2930: 2927: 2923: 2919: 2916: 2913: 2900: 2897: 2883: 2863: 2860: 2840: 2820: 2794: 2791: 2788: 2786: 2784: 2781: 2778: 2775: 2770: 2766: 2762: 2759: 2756: 2753: 2752: 2749: 2746: 2743: 2740: 2737: 2735: 2733: 2730: 2727: 2724: 2719: 2715: 2711: 2708: 2707: 2704: 2701: 2698: 2695: 2692: 2690: 2687: 2682: 2679: 2675: 2671: 2667: 2662: 2658: 2654: 2653: 2648: 2645: 2642: 2638: 2634: 2631: 2629: 2625: 2622: 2618: 2614: 2613: 2610: 2605: 2602: 2599: 2595: 2591: 2588: 2586: 2584: 2581: 2580: 2577: 2574: 2571: 2569: 2565: 2562: 2559: 2556: 2553: 2550: 2546: 2542: 2541: 2521: 2501: 2496: 2493: 2490: 2487: 2484: 2481: 2477: 2454: 2451: 2448: 2444: 2421: 2417: 2396: 2393: 2373: 2353: 2333: 2313: 2310: 2307: 2304: 2284: 2281: 2278: 2275: 2272: 2269: 2266: 2263: 2243: 2240: 2237: 2217: 2194: 2174: 2169: 2165: 2161: 2141: 2121: 2118: 2113: 2109: 2105: 2085: 2082: 2078: 2074: 2071: 2066: 2062: 2058: 2055: 2052: 2047: 2043: 2038: 2017: 2012: 2009: 2006: 2003: 2000: 1997: 1993: 1989: 1985: 1979: 1976: 1973: 1969: 1965: 1960: 1956: 1951: 1944: 1941: 1935: 1932: 1912: 1909: 1906: 1903: 1898: 1894: 1890: 1887: 1884: 1879: 1875: 1871: 1851: 1848: 1845: 1840: 1837: 1833: 1829: 1824: 1820: 1799: 1779: 1775: 1771: 1768: 1763: 1760: 1755: 1750: 1747: 1742: 1737: 1734: 1729: 1726: 1722: 1718: 1714: 1708: 1703: 1698: 1695: 1692: 1687: 1684: 1680: 1675: 1671: 1668: 1654: 1642: 1638: 1632: 1627: 1622: 1619: 1616: 1611: 1608: 1604: 1599: 1578: 1575: 1572: 1569: 1566: 1563: 1560: 1557: 1554: 1534: 1531: 1528: 1508: 1505: 1502: 1499: 1496: 1493: 1473: 1470: 1467: 1455:packing radius 1445:is said to be 1434: 1431: 1428: 1425: 1422: 1410: 1409: 1398: 1395: 1392: 1389: 1386: 1383: 1380: 1377: 1374: 1371: 1368: 1365: 1362: 1359: 1356: 1336: 1333: 1330: 1310: 1307: 1304: 1301: 1281: 1278: 1275: 1272: 1269: 1266: 1239: 1215: 1212: 1209: 1206: 1203: 1200: 1197: 1177: 1174: 1171: 1168: 1165: 1162: 1159: 1156: 1136: 1127:(depending on 1116: 1113: 1110: 1090: 1087: 1084: 1081: 1061: 1058: 1055: 1052: 1032: 1029: 1026: 1023: 1020: 1017: 990: 976: 964: 961: 958: 955: 952: 931: 909: 905: 902: 896: 893: 887: 881: 878: 872: 866: 863: 856: 852: 849: 836:has its usual 824: 820: 817: 797: 794: 791: 788: 785: 761: 741: 738: 735: 732: 729: 705: 702: 699: 696: 693: 674: 647: 644: 641: 638: 635: 615: 612: 609: 606: 603: 600: 578: 573: 570: 567: 556: 554: 551: 550: 547: 544: 541: 538: 527: 525: 522: 521: 519: 514: 511: 508: 505: 502: 499: 496: 487:is defined by 476: 456: 435: 415: 391: 388: 385: 365: 362: 359: 356: 353: 350: 347: 344: 341: 338: 335: 311: 292: 272: 244: 220: 200: 187: 175: 172: 147: 138:discrete space 128: 127: 42: 40: 33: 26: 9: 6: 4: 3: 2: 4267: 4256: 4253: 4251: 4248: 4246: 4243: 4242: 4240: 4229: 4225: 4221: 4215: 4211: 4207: 4203: 4199: 4195: 4191: 4187: 4183: 4181:3-540-90312-7 4177: 4173: 4169: 4168: 4163: 4159: 4155: 4154: 4148:, p. 35. 4147: 4146:Wilansky 2008 4142: 4134: 4130: 4126: 4124:0-8218-2629-8 4120: 4116: 4112: 4105: 4101: 4091: 4088: 4086: 4083: 4081: 4078: 4077: 4071: 4069: 4065: 4061: 4057: 4053: 4049: 4043: 4033: 4031: 4027: 4023: 4004: 4001: 3998: 3987: 3983: 3978: 3976: 3972: 3968: 3964: 3960: 3956: 3952: 3948: 3944: 3928: 3925: 3922: 3910: 3906: 3902: 3898: 3894: 3890: 3885: 3883: 3879: 3875: 3871: 3867: 3863: 3852: 3850: 3834: 3824: 3810: 3790: 3782: 3776: 3772: 3770: 3764: 3762: 3761:closed subset 3758: 3752: 3738: 3718: 3708: 3694: 3673: 3667: 3663: 3653: 3650: 3630: 3599: 3594: 3593:is constant. 3580: 3572: 3556: 3548: 3547: 3530: 3510: 3490: 3481: 3478: 3474: 3470: 3466: 3462: 3457: 3454: 3438: 3430: 3414: 3406: 3402: 3394: 3390: 3364: 3361: 3358: 3354: 3350: 3346: 3331: 3328: 3325: 3305: 3285: 3265: 3257: 3254: 3251: 3248: 3244: 3240: 3237: 3233: 3230: 3226: 3223: 3219: 3215: 3211: 3208: 3204: 3201: 3197: 3194: 3190: 3187: 3183: 3180: 3176: 3173: 3169: 3165: 3162: 3143: 3140: 3137: 3134: 3128: 3125: 3122: 3096: 3088: 3085: 3081: 3078: 3074: 3070: 3067: 3063: 3062: 3061: 3058: 3056: 3052: 3048: 3032: 3024: 3007: 3003: 3000: 2997: 2993: 2989: 2983: 2980: 2977: 2971: 2964:and given by 2963: 2939: 2936: 2933: 2928: 2925: 2921: 2914: 2911: 2895: 2881: 2861: 2858: 2838: 2818: 2809: 2792: 2789: 2787: 2779: 2773: 2768: 2764: 2760: 2757: 2754: 2747: 2744: 2741: 2738: 2736: 2728: 2722: 2717: 2713: 2709: 2702: 2699: 2696: 2693: 2691: 2685: 2680: 2677: 2673: 2669: 2665: 2660: 2656: 2646: 2643: 2640: 2636: 2632: 2630: 2623: 2620: 2616: 2608: 2603: 2600: 2597: 2593: 2589: 2587: 2582: 2575: 2572: 2570: 2560: 2557: 2554: 2548: 2544: 2519: 2499: 2491: 2488: 2485: 2479: 2475: 2452: 2449: 2446: 2442: 2419: 2415: 2394: 2391: 2371: 2351: 2331: 2311: 2308: 2305: 2302: 2282: 2279: 2273: 2270: 2267: 2261: 2241: 2238: 2235: 2215: 2206: 2192: 2167: 2163: 2139: 2119: 2111: 2107: 2083: 2080: 2076: 2072: 2069: 2064: 2060: 2056: 2053: 2050: 2045: 2041: 2036: 2015: 2007: 2004: 2001: 1995: 1991: 1987: 1983: 1977: 1974: 1971: 1967: 1963: 1958: 1954: 1949: 1942: 1939: 1933: 1930: 1910: 1904: 1901: 1896: 1892: 1888: 1885: 1882: 1877: 1873: 1849: 1846: 1843: 1838: 1835: 1831: 1827: 1822: 1818: 1797: 1777: 1773: 1769: 1766: 1761: 1758: 1753: 1748: 1745: 1740: 1735: 1732: 1727: 1724: 1720: 1716: 1712: 1706: 1696: 1693: 1690: 1685: 1682: 1678: 1673: 1669: 1666: 1653: 1640: 1636: 1630: 1620: 1617: 1614: 1609: 1606: 1602: 1597: 1576: 1573: 1570: 1564: 1561: 1558: 1552: 1532: 1529: 1526: 1506: 1503: 1500: 1497: 1494: 1491: 1471: 1468: 1465: 1458: 1450: 1449: 1429: 1426: 1423: 1396: 1393: 1390: 1384: 1381: 1378: 1372: 1369: 1366: 1363: 1360: 1357: 1354: 1334: 1331: 1328: 1308: 1305: 1302: 1299: 1279: 1273: 1270: 1267: 1257: 1253: 1237: 1229: 1210: 1201: 1198: 1195: 1175: 1172: 1166: 1163: 1160: 1154: 1134: 1114: 1111: 1108: 1088: 1085: 1082: 1079: 1072:if for every 1059: 1056: 1053: 1050: 1030: 1024: 1021: 1018: 1008: 1004: 988: 981: 977: 959: 953: 950: 907: 903: 900: 894: 891: 885: 879: 876: 870: 864: 861: 854: 850: 847: 839: 818: 815: 792: 789: 786: 775: 759: 752:(a subset of 736: 733: 730: 719: 700: 697: 694: 683: 675: 672: 671: 665: 642: 639: 636: 626:In this case 613: 610: 607: 604: 601: 598: 571: 568: 565: 552: 545: 542: 539: 536: 523: 517: 512: 506: 503: 500: 494: 474: 454: 447: 444: 436: 433: 413: 405: 389: 386: 383: 360: 357: 354: 351: 345: 342: 339: 325: 309: 301: 293: 290: 270: 262: 258: 242: 234: 218: 210: 202: 201: 199: 185: 171: 169: 165: 161: 157: 153: 152: 145: 143: 139: 135: 124: 121: 113: 102: 99: 95: 92: 88: 85: 81: 78: 74: 71: –  70: 66: 65:Find sources: 59: 55: 49: 48: 43:This article 41: 37: 32: 31: 19: 4209: 4165: 4141: 4110: 4104: 4080:Cylinder set 4067: 4063: 4051: 4045: 3979: 3963:Cantor space 3901:homeomorphic 3886: 3858: 3595: 3571:neighborhood 3544: 3482: 3458: 3398: 3247:homeomorphic 3059: 3054: 3050: 3046: 2902: 2810: 2207: 1658: 1452: 1446: 1412: 1256:metric space 1251: 1147:) such that 1007:metric space 1002: 716:refers to a 677: 667: 659: 658:is called a 438: 427: 295: 284: 204: 178:Given a set 177: 149: 137: 131: 116: 107: 97: 90: 83: 76: 64: 52:Please help 47:verification 44: 3986:compactness 3757:open subset 3598:ultrafilter 3471:maps or to 3431:on the set 3243:cardinality 174:Definitions 4239:Categories 4198:0386.54001 4133:0982.52018 4096:References 3947:Cantor set 3827:subset of 3759:or else a 3473:short maps 3401:continuous 3073:singletons 2899:Properties 2874:therefore 2254:such that 110:March 2011 80:newspapers 4228:227923899 4056:empty set 3965:.) Every 3882:Lie group 3791:∅ 3671:∅ 3664:∪ 3651:τ 3573:on which 3465:structure 3461:morphisms 3393:countable 3357:real line 3329:× 3222:countable 3172:Hausdorff 3161:entourage 3141:∈ 3001:− 2962:real line 2940:∈ 2926:− 2774:⁡ 2761:− 2755:− 2723:⁡ 2710:− 2678:− 2666:⁡ 2621:− 2549:− 2480:− 2306:≠ 2295:whenever 2208:However, 2081:∩ 2073:ε 2054:ε 2051:− 1996:− 1964:− 1931:ε 1905:ε 1886:ε 1883:− 1844:∈ 1836:− 1770:… 1697:∈ 1683:− 1621:∈ 1607:− 1501:∈ 1394:ε 1364:∈ 1329:ε 1303:⊆ 1230:. A set 1205:∖ 1199:∈ 1176:δ 1109:δ 1083:∈ 1054:⊆ 954:∪ 904:… 793:τ 737:τ 701:τ 668:space of 643:ρ 608:∈ 540:≠ 495:ρ 455:ρ 441:discrete 404:entourage 387:× 358:∈ 4245:Topology 4164:(1978). 4074:See also 3878:manifold 3847:is open 3453:category 3353:integers 3193:complete 3049:but not 3023:complete 1188:for all 1003:discrete 591:for any 324:superset 168:open set 151:isolated 134:topology 4190:0507446 3980:In the 3889:product 3480:short. 3451:in the 3351:on the 3207:bounded 3179:compact 1254:in the 975:is not. 263:), and 94:scholar 4226:  4216:  4196:  4188:  4178:  4131:  4121:  4060:cofree 3975:domain 3783:) are 3781:clopen 3753:either 3596:Every 3569:has a 3186:finite 3184:it is 3159:is an 1923:where 563:  534:  443:metric 406:, and 402:be an 261:closed 233:subset 166:is an 156:finest 96:  89:  82:  75:  67:  3969:of a 3967:fiber 3862:group 3825:every 3765:every 3709:every 3084:basis 1005:in a 840:then 776:that 666:or a 426:is a 283:is a 101:JSTOR 87:books 4224:OCLC 4214:ISBN 4176:ISBN 4119:ISBN 4064:from 3803:and 3777:both 3773:only 3429:free 3347:The 3245:are 3064:The 2790:< 2739:< 2694:< 2633:< 2590:< 2573:< 2434:and 2344:and 2280:> 2239:> 1659:Let 1571:> 1469:> 1391:> 1332:> 1292:for 1173:> 1112:> 1043:for 943:but 437:the 294:the 257:open 203:the 160:open 136:, a 73:news 4194:Zbl 4129:Zbl 3977:. 3899:is 3891:of 3849:and 3755:an 3751:is 3731:of 3687:on 3427:is 3258:If 3053:or 3045:is 2765:log 2714:log 2657:log 2467:is 2364:in 1545:or 1250:is 1001:is 980:set 720:of 467:on 376:in 302:on 255:be 235:of 211:on 132:In 56:by 4241:: 4222:. 4192:. 4186:MR 4184:. 4174:. 4160:; 4127:. 4068:to 4032:. 3887:A 3884:. 3769:or 3057:. 978:a 819::= 676:a 559:if 530:if 4230:. 4200:. 4135:. 4008:} 4005:1 4002:, 3999:0 3996:{ 3932:} 3929:1 3926:, 3923:0 3920:{ 3835:X 3811:X 3739:X 3719:S 3695:X 3674:} 3668:{ 3659:U 3654:= 3631:X 3609:U 3581:f 3557:Y 3531:X 3511:Y 3491:f 3439:X 3415:X 3395:. 3374:R 3332:Y 3326:X 3306:X 3286:Y 3266:X 3249:. 3238:. 3231:. 3224:. 3209:. 3195:. 3188:. 3163:. 3147:} 3144:X 3138:x 3135:: 3132:) 3129:x 3126:, 3123:x 3120:( 3117:{ 3097:X 3079:. 3033:X 3008:| 3004:y 2998:x 2994:| 2990:= 2987:) 2984:y 2981:, 2978:x 2975:( 2972:d 2948:} 2944:N 2937:n 2934:: 2929:1 2922:n 2918:{ 2915:= 2912:X 2882:X 2862:, 2859:r 2839:X 2819:n 2793:n 2783:) 2780:r 2777:( 2769:2 2758:1 2748:1 2745:+ 2742:n 2732:) 2729:r 2726:( 2718:2 2703:1 2700:+ 2697:n 2686:) 2681:1 2674:r 2670:( 2661:2 2647:1 2644:+ 2641:n 2637:2 2624:1 2617:r 2609:r 2604:1 2601:+ 2598:n 2594:2 2583:1 2576:r 2564:) 2561:1 2558:+ 2555:n 2552:( 2545:2 2520:n 2500:, 2495:) 2492:1 2489:+ 2486:n 2483:( 2476:2 2453:1 2450:+ 2447:n 2443:x 2420:n 2416:x 2395:. 2392:r 2372:X 2352:y 2332:x 2312:. 2309:y 2303:x 2283:r 2277:) 2274:y 2271:, 2268:x 2265:( 2262:d 2242:0 2236:r 2216:X 2193:X 2173:} 2168:n 2164:x 2160:{ 2140:X 2120:. 2117:} 2112:n 2108:x 2104:{ 2084:X 2077:) 2070:+ 2065:n 2061:x 2057:, 2046:n 2042:x 2037:( 2016:. 2011:) 2008:2 2005:+ 2002:n 1999:( 1992:2 1988:= 1984:) 1978:1 1975:+ 1972:n 1968:x 1959:n 1955:x 1950:( 1943:2 1940:1 1934:= 1911:, 1908:) 1902:+ 1897:n 1893:x 1889:, 1878:n 1874:x 1870:( 1850:, 1847:X 1839:n 1832:2 1828:= 1823:n 1819:x 1798:X 1778:, 1774:} 1767:, 1762:8 1759:1 1754:, 1749:4 1746:1 1741:, 1736:2 1733:1 1728:, 1725:1 1721:{ 1717:= 1713:} 1707:0 1702:N 1694:n 1691:: 1686:n 1679:2 1674:{ 1670:= 1667:X 1641:. 1637:} 1631:0 1626:N 1618:n 1615:: 1610:n 1603:2 1598:{ 1577:. 1574:r 1568:) 1565:y 1562:, 1559:x 1556:( 1553:d 1533:y 1530:= 1527:x 1507:, 1504:E 1498:y 1495:, 1492:x 1472:0 1466:r 1433:) 1430:d 1427:, 1424:E 1421:( 1397:. 1388:) 1385:y 1382:, 1379:x 1376:( 1373:d 1370:, 1367:S 1361:y 1358:, 1355:x 1335:0 1309:, 1306:X 1300:S 1280:, 1277:) 1274:d 1271:, 1268:X 1265:( 1238:S 1214:} 1211:x 1208:{ 1202:S 1196:y 1170:) 1167:y 1164:, 1161:x 1158:( 1155:d 1135:x 1115:0 1089:, 1086:S 1080:x 1060:, 1057:X 1051:S 1031:, 1028:) 1025:d 1022:, 1019:X 1016:( 989:S 963:} 960:0 957:{ 951:S 930:R 908:} 901:, 895:4 892:1 886:, 880:3 877:1 871:, 865:2 862:1 855:{ 851:= 848:S 823:R 816:Y 796:) 790:, 787:Y 784:( 760:Y 740:) 734:, 731:Y 728:( 704:) 698:, 695:Y 692:( 673:. 646:) 640:, 637:X 634:( 614:. 611:X 605:y 602:, 599:x 572:y 569:= 566:x 553:0 546:, 543:y 537:x 524:1 518:{ 513:= 510:) 507:y 504:, 501:x 498:( 475:X 414:X 390:X 384:X 364:} 361:X 355:x 352:: 349:) 346:x 343:, 340:x 337:( 334:{ 310:X 271:X 243:X 219:X 198:: 186:X 123:) 117:( 112:) 108:( 98:· 91:· 84:· 77:· 50:. 20:)

Index

Discrete metric

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topology
topological space
isolated
finest
open
singleton subset
open set
subset
open
closed
superset
entourage
metric
isolated points
topological subspace
subspace topology
Euclidean topology
set

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