Е. Деза_ М.М. Деза. Энциклопедический словарь расстояний (2008) (1185330), страница 14
Текст из файла (страница 14)
Ú‡ÍËÏ ÒÂÏÂÈÒÚ‚ÓÏ ÔÓ‰ÏÌÓÊÂÒÚ‚ ÏÌÓÊÂÒÚ‚‡ ï, ˜ÚÓ ‰Îfl‰‡ÌÌÓÈ ÚÓ˜ÍË x ∈ U („‰Â U – ÓÚÍ˚ÚÓ) ÒÛ˘ÂÒÚ‚ÛÂÚ Ú‡ÍÓ U ∈ , ˜ÚÓ x ∈ U ⊂ U(·‡Á‡ fl‚ÎflÂÚÒfl ÒÂÚ¸˛, ÒÓÒÚÓfl˘ÂÈ ËÁ ÓÚÍ˚Ú˚ı ÏÌÓÊÂÒÚ‚).É·‚‡ 3é·Ó·˘ÂÌËfl ÏÂÚ˘ÂÒÍËı ÔÓÒÚ‡ÌÒÚ‚çÂÍÓÚÓ˚ ӷӷ˘ÂÌËfl ÔÓÌflÚËfl ÏÂÚËÍË, ‚ ˜‡ÒÚÌÓÒÚË ÔÓÌflÚËfl Í‚‡ÁËÏÂÚËÍË,ÔÓ˜ÚË-ÏÂÚËÍË, ‡Ò¯ËÂÌÌÓÈ ÏÂÚËÍË, ·˚ÎË ‡ÒÒÏÓÚÂÌ˚ ‚ „Î. 1.
Ç ‰‡ÌÌÓÈ „·‚ÂÔ‰ÒÚ‡‚ÎÂÌ˚ ÌÂÍÓÚÓ˚ ӷӷ˘ÂÌËfl, Ò‚flÁ‡ÌÌ˚Â Ò ÚÓÔÓÎÓ„ËÂÈ, ÚÂÓËÂÈ ‚ÂÓflÚÌÓÒÚÂÈ, ‡Î„·ÓÈ Ë Ú.Ô.3.1. m-åÖíêàäàm-ïÂÏËÏÂÚË͇ÏÂÚË͇èÛÒÚ¸ ï – ÔÓËÁ‚ÓθÌÓ ÏÌÓÊÂÒÚ‚Ó. îÛÌ͈Ëfl d : Xm+1 → ̇Á˚‚‡ÂÚÒfl m-ıÂÏËÏÂÚËÍÓÈ, ÂÒÎË d ÌÂÓÚˈ‡ÚÂθ̇, Ú.Â. d(x 1 ,…,xn+1) ≥ 0 ‰Îfl ‚ÒÂı x1,…, xn+1 ∈ X, ÂÒÎË d‚ÔÓÎÌ ÒËÏÏÂÚ˘̇, Ú.Â. Û‰Ó‚ÎÂÚ‚ÓflÂÚ ÛÒÎӂ˲ d(x 1 ,…, xm+1 ) = d(xπ(1),…, xπ(m+1))‰Îfl ‚ÒÂı x1,…, xm+1 ∈ X Ë Î˛·ÓÈ ÔÂÂÒÚ‡ÌÓ‚ÍË π ˝ÎÂÏÂÌÚÓ‚ {1,…, m+1}, ÂÒÎË dÔ˂‰Â̇ Í ÌÛβ, Ú.Â.
d(x1,…, xm+1 ) = 0 ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ x 1 ,…, xm+1 ÌÂfl‚Îfl˛ÚÒfl ÔÓÔ‡ÌÓ ‡Á΢Ì˚ÏË, Ë ÂÒÎË ‰Îfl ‚ÒÂı x 1 ,…, xm+2 ∈ X ÙÛÌ͈Ëfl dÛ‰Ó‚ÎÂÚ‚ÓflÂÚ m-ÒËÏÔÎÂÍÒÌÓÏÛ Ì‡‚ÂÌÒÚ‚Û:d ( x1 , …, x m +1 ) ≤m +1∑ d( x1,…, xi −1, xi +1,…, xm + 2 ).i =12-ÏÂÚË͇èÛÒÚ¸ ï – ÔÓËÁ‚ÓθÌÓ ÏÌÓÊÂÒÚ‚Ó. îÛÌ͈Ëfl ̇Á˚‚‡ÂÚÒfl d : X → 2-ÏÂÚËÍÓÈ,ÂÒÎË d ÌÂÓÚˈ‡ÚÂθ̇, ‚ÔÓÎÌ ÒËÏÏÂÚ˘̇, Ô˂‰Â̇ Í ÌÛβ Ë Û‰Ó‚ÎÂÚ‚ÓflÂÚ̇‚ÂÌÒÚ‚Û ÚÂÚ‡˝‰‡d ( x1 , x 2 , x3 ) ≤ d ( x 4 , x 2 x3 ) + d ( x1 , x 4 , x 4 ) + d ( x1 , x 2 , x 4 ).ùÚÓ – ̇˷ÓΠ‚‡ÊÌ˚È ÒÎÛ˜‡È m = 2 ÔÓËÁ‚ÓθÌÓÈ m-ıÂÏËÏÂÚËÍË.(m, s)-ÒÛÔÂÏÂÚË͇èÛÒÚ¸ ï – ÔÓËÁ‚ÓθÌÓ ÏÌÓÊÂÒÚ‚Ó Ë s – ÔÓÎÓÊËÚÂθÌÓ ‚¢ÂÒÚ‚ÂÌÌÓ ˜ËÒÎÓ.îÛÌ͈Ëfl d : Xm+1 → ̇Á˚‚‡ÂÚÒfl (m, s)-ÒÛÔÂÏÂÚËÍÓÈ ([DeDu03]), ÂÒÎË d ÌÂÓÚˈ‡ÚÂθ̇, ‚ÔÓÎÌ ÒËÏÏÂÚ˘̇, Ô˂‰Â̇ Í ÌÛβ Ë Û‰Ó‚ÎÂÚ‚ÓflÂÚ (m, s)-ÒËÏÔÎÂÍÒÌÓÏÛ Ì‡‚ÂÌÒÚ‚Û:d ( x1 , …, x m +1 ) ≤m +1∑ d( x1,…, xi −1, xi +1,…, xm + 2 ).i =1(m, s)-ÒÛÔÂÏÂÚË͇ fl‚ÎflÂÚÒfl m-ÔÓÎÛÏÂÚËÍÓÈ, ÂÒÎË s ≥ 1.62ó‡ÒÚ¸ I.
å‡ÚÂχÚË͇ ‡ÒÒÚÓflÌËÈ3.2. çÖéèêÖÑÖãÖççõÖ åÖíêàäàçÂÓÔ‰ÂÎÂÌ̇fl ÏÂÚË͇çÂÓÔ‰ÂÎÂÌ̇fl ÏÂÚË͇ (ËÎË G-ÏÂÚË͇) ̇ ‚¢ÂÒÚ‚ÂÌÌÓÏ (ÍÓÏÔÎÂÍÒÌÓÏ)‚ÂÍÚÓÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â V ÂÒÚ¸ ·ËÎËÌÂÈ̇fl (‰Îfl ÒÎÛ˜‡fl ÍÓÏÔÎÂÍÒÌÓÈ ÔÂÂÏÂÌÌÓÈ –ÒÂÒÍËÎËÌÂÈ̇fl) ÙÓχ G ̇ V, Ú.Â. ÙÛÌ͈Ëfl G V × V (), ڇ͇fl ˜ÚÓ ‰Îfl β·˚ıx, y, z ∈ V Ë Î˛·˚ı Ò͇ÎflÓ‚ α, β ËÏÂ˛Ú ÏÂÒÚÓ ÒÎÂ‰Û˛˘Ë ҂ÓÈÒÚ‚‡:G(αx + βy, z ) = αG( x, z ) + βG( y, z ) Ë G( x, αy + βz ) = αG( x, z ) + β G( y, z )„‰Â α = a + bi = a − bi Ó·ÓÁ̇˜‡ÂÚ ÍÓÏÔÎÂÍÒÌÓ ÒÓÔflÊÂÌËÂ).ÖÒÎË G – ÔÓÎÓÊËÚÂθÌÓ ÓÔ‰ÂÎÂÌ̇fl ÒËÏÏÂÚ˘̇fl ÙÓχ, ÚÓ ˝ÚÓ Ò͇ÎflÌÓÂÔÓËÁ‚‰ÂÌË ̇ V Ë Â„Ó ÏÓÊÌÓ ËÒÔÓθÁÓ‚‡Ú¸ ‰Îfl ͇ÌÓÌ˘ÂÒÍÓ„Ó ‚‚‰ÂÌËfl ÌÓÏ˚ ËÒÓÓÚ‚ÂÚÒÚ‚Û˛˘ÂÈ ÏÂÚËÍË ÌÓÏ˚ ̇ V. ÑÎfl ÒÎÛ˜‡fl Ó·˘ÂÈ ÙÓÏ˚ G Ì ÒÛ˘ÂÒÚ‚ÛÂÚÌË ÌÓÏ˚, ÌË ÏÂÚËÍË, ͇ÌÓÌ˘ÂÒÍË Ò‚flÁ‡ÌÌÓÈ Ò G, Ë ÚÂÏËÌ ÌÂÓÔ‰ÂÎÂÌ̇flÏÂÚË͇ ÚÓθÍÓ Ì‡ÔÓÏË̇ÂÚ Ó ÚÂÒÌÓÈ Ò‚flÁË ÔÓÎÓÊËÚÂθÌÓ ÓÔ‰ÂÎÂÌÌ˚ı ·ËÎËÌÂÈÌ˚ı ÙÓÏ Ò ÌÂÍÓÚÓ˚ÏË ÏÂÚË͇ÏË ‚ ‚ÂÍÚÓÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â(ÒÏ.
„Î. 7 Ë 26).臇 (V, G) ̇Á˚‚‡ÂÚÒfl ÔÓÒÚ‡ÌÒÚ‚ÓÏ Ò ÌÂÓÔ‰ÂÎÂÌÌÓÈ ÏÂÚËÍÓÈ. äÓ̘ÌÓÏÂÌÓ ÔÓÒÚ‡ÌÒÚ‚Ó Ò ÌÂÓÔ‰ÂÎÂÌÌÓÈ ÏÂÚËÍÓÈ Ì‡Á˚‚‡ÂÚÒfl ·ËÎËÌÂÈÌ˚Ï ÏÂÚ˘ÂÒÍËÏ ÔÓÒÚ‡ÌÒÚ‚ÓÏ. ÉËθ·ÂÚÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó ç, Ò̇·ÊÂÌÌÓ ÌÂÔÂ˚‚ÌÓÈG -ÏÂÚËÍÓÈ, ̇Á˚‚‡ÂÚÒfl „Ëθ·ÂÚÓ‚˚Ï ÔÓÒÚ‡ÌÒÚ‚ÓÏ Ò ÌÂÓÔ‰ÂÎÂÌÌÓÈÏÂÚËÍÓÈ. ç‡Ë·ÓΠ‚‡ÊÌ˚Ï ÔËÏÂÓÏ Ú‡ÍÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ fl‚ÎflÂÚÒfl J-ÔÓÒÚ‡ÌÒÚ‚Ó.èÓ‰ÔÓÒÚ‡ÌÒÚ‚Ó L ‚ ÔÓÒÚ‡ÌÒÚ‚Â (V, G) Ò ÌÂÓÔ‰ÂÎÂÌÌÓÈ ÏÂÚËÍÓÈ Ì‡Á˚‚‡ÂÚÒfl ÔÓÎÓÊËÚÂθÌ˚Ï, ÓÚˈ‡ÚÂθÌ˚Ï ËÎË ÌÂÈڇθÌ˚Ï ÔÓ‰ÔÓÒÚ‡ÌÒÚ‚ÓÏ‚ Á‡‚ËÒËÏÓÒÚË ÓÚ ‚˚ÔÓÎÌÂÌËfl ̇‚ÂÌÒÚ‚ G(x, x) > 0, G(x, x) < 0 ËÎË G(x, x) = 0 ‰Îfl‚ÒÂı x → L.ùÏËÚÓ‚‡ G-ÏÂÚË͇ùÏËÚÓ‚‡ G -ÏÂÚË͇ ÌÂÓÔ‰ÂÎÂÌ̇fl ÏÂÚË͇ GH ̇ ÍÓÏÔÎÂÍÒÌÓÏ ‚ÂÍÚÓÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â V , ڇ͇fl ˜ÚÓ ‰Îfl ‚ÒÂı x , y ∈ V ËÏÂÂÚ ÏÂÒÚÓ ‡‚ÂÌÒÚ‚ÓG H ( x, y) = G H ( y, x ), „‰Â α = a + bi = a − bi ÓÁ̇˜‡ÂÚ ÍÓÏÔÎÂÍÒÌÓ ÒÓÔflÊÂÌËÂ.ê„ÛÎfl̇fl G-ÏÂÚË͇ê„ÛÎfl̇fl G -ÏÂÚË͇ ÂÒÚ¸ ÌÂÔÂ˚‚̇fl ÌÂÓÔ‰ÂÎÂÌ̇fl ÏÂÚË͇ G ̇ „Ëθ·ÂÚÓ‚ÓÏ ÔÓÒÚ‡ÌÒÚ‚Â ç ̇‰ , ÔÓÓʉ‡Âχfl Ó·‡ÚËÏ˚Ï ˝ÏËÚÓ‚˚Ï ÓÔ‡ÚÓÓÏí ÔÓ ÙÓÏÛÎÂG(x, y) = 〈T(x), y〉,„‰Â 〈,〉 – Ò͇ÎflÌÓ ÔÓËÁ‚‰ÂÌË ̇ ç.ùÏËÚÓ‚ ÓÔ‡ÚÓ Ì‡ „Ëθ·ÂÚÓ‚ÓÏ ÔÓÒÚ‡ÌÒÚ‚Â ç – ·ËÎËÌÂÈÌ˚È ÓÔ‡ÚÓ í̇ ç, Á‡‰‡‚‡ÂÏ˚È Ì‡ ӷ·ÒÚË ÔÎÓÚÌÓÒÚË D(T) ÔÓÒÚ‡ÌÒÚ‚‡ ç ÔÓ Á‡ÍÓÌÛ 〈T(x), y〉 == 〈x, T(y)〉 ‰Îfl β·˚ı x, y ∈ D(T).
鄇Ì˘ÂÌÌ˚È ˝ÏËÚÓ‚ ÓÔ‡ÚÓ ÎË·Ó ÓÔ‰ÂÎÂÌ̇ ‚ÒÂÏ ç, ÎË·Ó ÏÓÊÂÚ ·˚Ú¸ ÌÂÔÂ˚‚ÌÓ ÔÓ‰ÓÎÊÂÌ Ì‡ ‚Ò ç Ë ÚÓ„‰‡ í = í * . ç‡ÍÓ̘ÌÓÏÂÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â ˝ÏËÚÓ‚ ÓÔ‡ÚÓ ÏÓÊÂÚ ·˚Ú¸ Á‡‰‡Ì ˝ÏËÚÓ‚ÓÈχÚˈÂÈ (( aij )) = (( a ji )).É·‚‡ 3. é·Ó·˘ÂÌËfl ÏÂÚ˘ÂÒÍËı ÔÓÒÚ‡ÌÒÚ‚63J-ÏÂÚË͇J-ÏÂÚË͇ – ÌÂÔÂ˚‚̇fl ÌÂÓÔ‰ÂÎÂÌ̇fl ÏÂÚË͇ G ̇ „Ëθ·ÂÚÓ‚ÓÏ ÔÓÒÚ‡ÌÒÚ‚Â ç ̇‰ ë, Á‡‰‡‚‡Âχfl ÌÂÍËÏ ˝ÏËÚÓ‚˚Ï ËÌ‚ÓβÚË‚Ì˚Ï ÓÚÓ·‡ÊÂÌËÂÏ J̇ ç ÔÓ ÙÓÏÛÎÂG(x, y) = 〈J(x), y〉,„‰Â 〈,〉 – ÂÒÚ¸ Ò͇ÎflÌÓ ÔÓËÁ‚‰ÂÌË ̇ ç.àÌ‚ÓβÚË‚ÌÓ ÓÚÓ·‡ÊÂÌË – ÓÚÓ·‡ÊÂÌË ç ̇ ç, Í‚‡‰‡Ú ÍÓÚÓÓ„Ó fl‚ÎflÂÚÒflÚÓʉÂÒÚ‚ÂÌÌ˚Ï ÓÚÓ·‡ÊÂÌËÂÏ.
àÌ‚ÓβÚË‚ÌÓ ÓÚÓ·‡ÊÂÌË J ÏÓÊÂÚ ·˚Ú¸Ô‰ÒÚ‡‚ÎÂÌÓ ‡‚ÂÌÒÚ‚ÓÏ J = P + – P– , , „‰Â ê+ Ë ê – fl‚Îfl˛ÚÒfl ÓÚÓ„Ó̇θÌ˚ÏËÔÓÂ͈ËflÏË ‚ ç, ‡ P + + P– = H. ê‡Ì„ ÌÂÓÔ‰ÂÎÂÌÌÓÒÚË J-ÏÂÚËÍË ÓÔ‰ÂÎflÂÚÒfl ͇Ímin{dim P+, dim P– }.èÓÒÚ‡ÌÒÚ‚Ó (H, G) ̇Á˚‚‡ÂÚÒfl J-ÔÓÒÚ‡ÌÒÚ‚ÓÏ. J-ÔÓÒÚ‡ÌÒÚ‚Ó Ò ÍÓ̘Ì˚χ̄ÓÏ ÌÂÓÔ‰ÂÎÂÌÌÓÒÚË Ì‡Á˚‚‡ÂÚÒfl ÔÓÒÚ‡ÌÒÚ‚ÓÏ èÓÌÚfl„Ë̇.3.3. íéèéãéÉàóÖëäàÖ éÅéÅôÖçàüó‡ÒÚ˘ÌÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Óó‡ÒÚ˘ÌÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó (å˝Ú¸˛Á, 1992) ÓÔ‰ÂÎflÂÚÒfl Í‡Í Ô‡‡ (X,d), „‰Â ï – ÌÂÍÓÚÓÓ ÏÌÓÊÂÒÚ‚Ó, ‡ d – ÌÂÓÚˈ‡ÚÂθ̇fl ÒËÏÏÂÚ˘̇fl ÙÛÌ͈Ëfld : X × X → , ڇ͇fl ˜ÚÓ d(x, x) ≤ d(x, y) ‰Îfl ‚ÒÂı x, y ∈ X (Ú.Â.
β·Ó ҇ÏÓ‡ÒÒÚÓflÌËÂx(x. x), χÎÓ), ı = Û, ÂÒÎË d(x, x) = d(x, y) = d(y, y) = 0 (í 0 – ‡ÍÒËÓχ ÓÚ‰ÂÎËÏÓÒÚË) Ë̇‚ÂÌÒÚ‚Ód(x, y) ≤ d(x, z) + d(z, y) – d(z, z)‚˚ÔÓÎÌflÂÚÒfl ‰Îfl ‚ÒÂı x, y, z ∈ X (ÒËθÌӠ̇‚ÂÌÒÚ‚Ó ÚÂÛ„ÓθÌË͇).ÖÒÎË d fl‚ÎflÂÚÒfl ˜‡ÒÚ˘ÌÓÈ ÏÂÚËÍÓÈ, ÚÓ d(x, y) – d(x, x) ·Û‰ÂÚ Í‚‡ÁËÔÓÎÛÏÂÚËÍÓÈË (X, d) ÏÓÊÂÚ ·˚Ú¸ ˜‡ÒÚ˘ÌÓ ÛÔÓfl‰Ó˜ÂÌÓ, ÂÒÎË Ï˚ ÓÔ‰ÂÎËÏ x p− y ÚÓ„‰‡ Ë ÚÓθÍÓÚÓ„‰‡ d(x, y) – d(x, x) = 0.ëıÓ‰ÒÚ‚ÓèÛÒÚ¸ ï – ÔÓËÁ‚ÓθÌÓ ÏÌÓÊÂÒÚ‚Ó. îÛÌ͈Ëfl d : X × X → ̇Á˚‚‡ÂÚÒflÒıÓ‰ÒÚ‚ÓÏ Ì‡ ï, ÂÒÎË d ÒËÏÏÂÚ˘ÌÓ Ë ÂÒÎË ‰Îfl ‚ÒÂı x, y ∈ X ‚˚ÔÓÎÌflÂÚÒfl ÎË·Ód(x, x) ≤ d(x, y) – ‚ Ú‡ÍÓÏ ÒÎÛ˜‡Â d ̇Á˚‚‡ÂÚÒfl ÒıÓ‰ÒÚ‚ÓÏ ‚Ô‰ ̇‚ÂÌÒÚ‚Ó, ÎË·Ód(x, x) ≥ d(x, y) – ÚÓ„‰‡ d ̇Á˚‚‡ÂÚÒfl ÒıÓ‰ÒÚ‚ÓÏ Ì‡Á‡‰.ÇÒflÍÓ ÒıÓ‰ÒÚ‚Ó d ÔÓÓʉ‡ÂÚ ÒÚÓ„ËÈ ˜‡ÒÚ˘Ì˚È ÔÓfl‰ÓÍ Ɱ ̇ ÏÌÓÊÂÒÚ‚Â ‚ÒÂıÌÂÛÔÓfl‰Ó˜ÂÌÌ˚ı Ô‡ ˝ÎÂÏÂÌÚÓ‚ ï ÔÓÒ‰ÒÚ‚ÓÏ Á‡‰‡ÌËfl {x, y} Ɱ {u, ν} ÚÓ„‰‡ ËÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ d(x, y) < d(u, ν).ÑÎfl β·Ó„Ó ÒıÓ‰ÒÚ‚‡ ̇Á‡‰ d ÒıÓ‰ÒÚ‚Ó ‚Ô‰ – d ÔÓÓʉ‡ÂÚ ÚÓÚ Ê ˜‡ÒÚ˘Ì˚ÈÔÓfl‰ÓÍ.èÓÒÚ‡ÌÒÚ‚Ó -‡ÒÒÚÓflÌËflèÓÒÚ‡ÌÒÚ‚Ó - ‡ Ò Ò Ú Ó fl Ì Ë fl ÂÒÚ¸ Ô‡‡ (X, f), „‰Â ï – ÚÓÔÓÎӄ˘ÂÒÍÓÂÔÓÒÚ‡ÌÒÚ‚Ó, ‡ f fl‚ÎflÂÚÒfl τ-‡ÒÒÚÓflÌËÂÏ ÄÏË–åÛÚ‡‚‡ÍËÎfl ̇ ï, Ú.Â.
ÌÂÓÚˈ‡ÚÂθÌÓÈ ÙÛÌ͈ËÂÈ f : X × X → , Ú‡ÍÓÈ ˜ÚÓ ‰Îfl β·Ó„Ó x ∈ X Ë Î˛·ÓÈÓÍÂÒÚÌÓÒÚË U ÚÓ˜ÍË ı ÒÛ˘ÂÒÚ‚ÛÂÚ ε > 0 c ÛÒÎÓ‚ËÂÏ {y ∈ X : f(x, y) < ε} ⊂ U.ã˛·Ó ÔÓÒÚ‡ÌÒÚ‚Ó ‡ÒÒÚÓflÌËÈ (X, d) ÂÒÚ¸ ÔÓÒÚ‡ÌÒÚ‚Ó τ-‡ÒÒÚÓflÌËfl ‰ÎflÚÓÔÓÎÓ„ËË τ f, ÓÔ‰ÂÎÂÌÌÓÈ ÒÎÂ‰Û˛˘ËÏ Ó·‡ÁÓÏ: A ∈ τf, ÂÒÎË ‰Îfl β·Ó„Ó x ∈ XÒÛ˘ÂÒÚ‚ÛÂÚ ε > 0, Ú‡ÍÓ ˜ÚÓ {y ∈ X : f(x, y) < ε} ⊂ A. é‰Ì‡ÍÓ ÒÛ˘ÂÒÚ‚Û˛Ú ÌÂÏÂÚËÁÛÂÏ˚ ÔÓÒÚ‡ÌÒÚ‚‡ τ-‡ÒÒÚÓflÌËfl. τ-ê‡ÒÒÚÓflÌË f(x, y) Ì ӷflÁ‡ÚÂθÌÓ ‰ÓÎÊÌÓ64ó‡ÒÚ¸ I. å‡ÚÂχÚË͇ ‡ÒÒÚÓflÌËÈ·˚Ú¸ ÒËÏÏÂÚ˘Ì˚Ï ËÎË Ó·‡˘‡Ú¸Òfl ‚ ÌÛθ ‰Îfl x = y; ̇ÔËÏÂ, e| x–y | fl‚ÎflÂÚÒflτ-‡ÒÒÚÓflÌËÂÏ Ì‡ ï = Ò Ó·˚˜ÌÓÈ ÚÓÔÓÎÓ„ËÂÈ.èÓÒÚ‡ÌÒÚ‚Ó ·ÎËÁÓÒÚËèÓÒÚ‡ÌÒÚ‚Ó ·ÎËÁÓÒÚË (ÖÙÂÏӂ˘, 1936) – ÏÌÓÊÂÒÚ‚Ó ï Ò ·Ë̇Ì˚Ï ÓÚÌÓ¯ÂÌËÂÏ δ ̇ ÒÚÂÔÂÌÌÓÏ ÏÌÓÊÂÒÚ‚Â ê(ï) ‚ÒÂı Â„Ó ÔÓ‰ÏÌÓÊÂÒÚ‚, ÍÓÚÓÓ ۉӂÎÂÚ‚ÓflÂÚ ÒÎÂ‰Û˛˘ËÏ ÛÒÎÓ‚ËflÏ:1) ÄδÇ ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ ÇδÄ (ÒËÏÏÂÚ˘ÌÓÒÚ¸);2) Äδ(Ç ∪ ë) ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ ÄδÇ ËÎË Äδë (‡‰‰ËÚË‚ÌÓÒÚ¸);3) ÄδA ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ A ≠ 0/ (ÂÙÎÂÍÒË‚ÌÓÒÚ¸).éÚÌÓ¯ÂÌË δ ÓÔ‰ÂÎflÂÚ ·ÎËÁÓÒÚ¸ (ËÎË ÒÚÛÍÚÛÛ ·ÎËÁÓÒÚË) ̇ ï.
ÖÒÎË ÄδÇÌ ‚˚ÔÓÎÌflÂÚÒfl, ÚÓ ÏÌÓÊÂÒÚ‚‡ Ä Ë Ç Ì‡Á˚‚‡˛ÚÒfl Û‰‡ÎÂÌÌ˚ÏË ÏÌÓÊÂÒÚ‚‡ÏË.ÇÒflÍÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó (X, d) ÂÒÚ¸ ÔÓÒÚ‡ÌÒÚ‚Ó ·ÎËÁÓÒÚË: ÓÔ‰ÂÎËÏ,˜ÚÓ ÄδÇ ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ d(A, B) = infx∈A,y∈B d(x, y) = 0.ã˛·‡fl ·ÎËÁÓÒÚ¸ ̇ ï ÔÓÓʉ‡ÂÚ (‚ÔÓÎÌ „ÛÎflÌÛ˛) ÚÓÔÓÎӄ˲ ̇ ï Á‡‰‡ÌËÂÏ̇ ÏÌÓÊÂÒÚ‚Â ‚ÒÂı ÔÓ‰ÏÌÓÊÂÒÚ‚ ï ÓÔ‡ÚÓ‡ Á‡Ï˚͇ÌËfl cl : P(X) → P(X) ÔÓ Á‡ÍÓÌÛcl(A) = {x ∈ X : {x}δA}.ꇂÌÓÏÂÌÓ ÔÓÒÚ‡ÌÒÚ‚Óí‡ÍË ÚÓÔÓÎӄ˘ÂÒÍË ÔÓÒÚ‡ÌÒÚ‚‡ (Ò ‰ÓÔÓÎÌËÚÂθÌ˚ÏË ÒÚÛÍÚÛ‡ÏË) ‰‡˛ÚÓ·Ó·˘ÂÌËfl ÏÂÚ˘ÂÒÍËı ÔÓÒÚ‡ÌÒÚ‚, ÓÒÌÓ‚‡ÌÌ˚ ̇ ‡ÒÒÚÓflÌËË ÏÂÊ‰Û ÏÌÓÊÂÒÚ‚‡ÏË.ꇂÌÓÏÂÌ˚Ï ÔÓÒÚ‡ÌÒÚ‚ÓÏ (Ç˝Èθ, 1937) ̇Á˚‚‡ÂÚÒfl ÏÌÓÊÂÒÚ‚Ó ï Ò ‡‚ÌÓÏÂÌÓÒÚ¸˛ (ËÎË ‡‚ÌÓÏÂÌÓÈ ÒÚÛÍÚÛÓÈ) – ÌÂÔÛÒÚ˚Ï ÒÂÏÂÈÒÚ‚ÓÏ ÔÓ‰ÏÌÓÊÂÒÚ‚ÏÌÓÊÂÒÚ‚‡ ï × ï, ̇Á˚‚‡ÂÏ˚ı ÓÍÛÊÂÌËflÏË Ë Ó·Î‡‰‡˛˘Ëı ÒÎÂ‰Û˛˘ËÏË Ò‚ÓÈÒÚ‚‡ÏË:1) ͇ʉÓ ËÁ ÔÓ‰ÏÌÓÊÂÒÚ‚ ï × ï, ÒÓ‰Âʇ˘Â ÏÌÓÊÂÒÚ‚Ó ËÁ , ÔË̇‰ÎÂÊËÚ ;2) ‚ÒflÍÓ ÍÓ̘ÌÓ ÔÂÂÒ˜ÂÌË ÏÌÓÊÂÒÚ‚ ËÁ ÔË̇‰ÎÂÊËÚ ;3) ͇ʉÓ ÏÌÓÊÂÒÚ‚Ó V ∈ ÒÓ‰ÂÊËÚ ‰Ë‡„Ó̇θ, Ú.Â.
ÏÌÓÊÂÒÚ‚Ó {(x, x):x ∈ X} ⊂ ï × ï;4) ÂÒÎË V ÔË̇‰ÎÂÊËÚ , ÚÓ ÏÌÓÊÂÒÚ‚Ó {(y, x) : (x, y) ∈ V} ÔË̇‰ÎÂÊËÚ ;5) ÂÒÎË V ÔË̇‰ÎÂÊËÚ , ÚÓ ÒÛ˘ÂÒÚ‚ÛÂÚ Ú‡ÍÓ V ∈ , ˜ÚÓ (x, z) ∈ V ‚Ó ‚ÒÂıÒÎÛ˜‡flı, ÍÓ„‰‡ (x, y), (y, z) ∈ V.ä‡Ê‰Ó ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó (ï, d) fl‚ÎflÂÚÒfl ‡‚ÌÓÏÂÌ˚Ï ÔÓÒÚ‡ÌÒÚ‚ÓÏ.éÍÛÊÂÌË ‚ (ï, d) ÂÒÚ¸ ÔÓ‰ÏÌÓÊÂÒÚ‚Ó ï × ï, ÒÓ‰Âʇ˘Â ÏÌÓÊÂÒÚ‚Ó Vε == {(x, y) ∈ X × X : d(x, y) < ε } ‰Îfl ÌÂÍÓÚÓÓ„Ó ÔÓÎÓÊËÚÂθÌÓ„Ó ‰ÂÈÒÚ‚ËÚÂθÌÓ„Ó˜ËÒ· ε. ÑÛ„ËÏ ·‡ÁÓ‚˚Ï ÔËÏÂÓÏ ‡‚ÌÓÏÂÌÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ fl‚Îfl˛ÚÒfl ÚÓÔÓÎӄ˘ÂÒÍË „ÛÔÔ˚.èÓÒÚ‡ÌÒÚ‚Ó ÔË·ÎËÊÂÌÌÓÒÚËèÓÒÚ‡ÌÒÚ‚Ó ÔË·ÎËÊÂÌÌÓÒÚË (ïÂËı, 1974) ÂÒÚ¸ ÏÌÓÊÂÒÚ‚Ó ï ÒÓ ÒÚÛÍÚÛÓÈ ÔË·ÎËÊÂÌÌÓÒÚË, Ú.Â.