Е. Деза_ М.М. Деза. Энциклопедический словарь расстояний (2008) (1185330), страница 19
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ÙÛÌ͈ËÂÈ 〈 , 〉 : V × V → (), Ú‡ÍÓÈ ˜ÚÓ ‰Îfl ‚ÒÂıx, y, z ∈ V Ë ‚ÒÂı Ò͇ÎflÌ˚ı ‚Â΢ËÌ α, β ËÏÂ˛Ú ÏÂÒÚÓ ÒÎÂ‰Û˛˘Ë ҂ÓÈÒÚ‚‡:1) 〈 x, x 〉 ≥ 0 c 〈 x, x 〉 ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ x = 0;2) 〈 x, y 〉 = 〈 y, x 〉, „‰Â α = a + bi = a − bi ÓÁ̇˜‡ÂÚ ÍÓÏÔÎÂÍÒÌÓ ÒÓÔflÊÂÌËÂ;3) 〈αx + βy, z 〉 = α 〈 x, z 〉 + β〈 y, z 〉.ÑÎfl ÍÓÏÔÎÂÍÒÌÓ„Ó ‚ÂÍÚÓÌÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ Ò͇ÎflÌÓ ÔÓËÁ‚‰ÂÌË ̇Á˚‚‡ÂÚÒflÚ‡ÍÊ ˝ÏËÚÓ‚˚Ï Ò͇ÎflÌ˚Ï ÔÓËÁ‚‰ÂÌËÂÏ, ‡ ÒÓÓÚ‚ÂÚÒÚ‚Û˛˘Â ÏÂÚ˘ÂÒÍÓÂÔÓÒÚ‡ÌÒÚ‚Ó – ÔÓÒÚ‡ÌÒÚ‚ÓÏ Ò ˝ÏËÚÓ‚˚Ï Ò͇ÎflÌ˚Ï ÔÓËÁ‚‰ÂÌËÂÏ .84ó‡ÒÚ¸ I. å‡ÚÂχÚË͇ ‡ÒÒÚÓflÌËÈçÓχ || ⋅ || ‚ ÌÓÏËÓ‚‡ÌÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â (V , || ⋅ ||) ÔÓÓʉ‡ÂÚÒfl Ò͇ÎflÌ˚ÏÔÓËÁ‚‰ÂÌËÂÏ ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ ‰Îfl ‚ÒÂı x, y ∈ V ËÏÂÂÚ ÏÂÒÚÓ ‡‚ÂÌÒÚ‚Ó|| x + y ||2 + || x − y ||2 = 2(|| x ||2 + || y ||2 ).ÉËθ·ÂÚÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚ÓÉËθ·ÂÚÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó ÂÒÚ¸ ÔÓÒÚ‡ÌÒÚ‚Ó ÒÓ Ò͇ÎflÌ˚Ï ÔÓËÁ‚‰ÂÌËÂÏ, ÍÓÚÓÓÂ, Í‡Í ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó, fl‚ÎflÂÚÒfl ÔÓÎÌ˚Ï.
íӘ̠„Ó‚Ófl, „Ëθ·ÂÚÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó ÂÒÚ¸ ÔÓÎÌÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó ( H , || x − y ||) ̇ ‰ÂÈÒÚ‚ËÚÂθÌÓÏ (ÍÓÏÔÎÂÍÒÌÓÏ) ‚ÂÍÚÓÌÓÏ ÔÓÒÚ‡ÌÒÚ‚Â ç ÒÓ Ò͇ÎflÌ˚Ï ÔÓËÁ‚‰ÂÌËÂÏ〈 , 〉, Ú‡ÍËÏ ˜ÚÓ ÏÂÚË͇ ÌÓÏ˚ || x − y || ÒÚÓËÚÒfl ÔÓ ÌÓÏ Ò͇ÎflÌÓ„Ó ÔÓËÁ‚‰ÂÌËfl|| x ||= 〈 x, x 〉 . ã˛·Ó „Ëθ·ÂÚÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó ÂÒÚ¸ ·‡Ì‡ıÓ‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó.èËÏÂÓÏ „Ëθ·ÂÚÓ‚‡ ÔÓÒÚ‡ÌÒÚ‚‡ ÒÎÛÊËÚ ÏÌÓÊÂÒÚ‚Ó ‚ÒÂı ÔÓÒΉӂ‡ÚÂθÌÓÒÚÂÈ x = {x n}n ‰ÂÈÒÚ‚ËÚÂθÌ˚ı (ÍÓÏÔÎÂÍÒÌ˚ı) ˜ËÒÂÎ, Ú‡ÍËı ˜ÚÓ∞∑ | xi |2 ÒıÓ‰ËÚÒfli =1ÔÓ „Ëθ·ÂÚÓ‚ÓÈ ÏÂÚËÍÂ, Á‡‰‡‚‡ÂÏÓÈ Í‡Í ∞| xi − yi i =1∑| 21/ 2.Ç Í‡˜ÂÒÚ‚Â ‰Û„Ëı ÔËÏÂÓ‚ „Ëθ·ÂÚÓ‚˚ı ÔÓÒÚ‡ÌÒÚ‚ ÏÓÊÌÓ ÔË‚ÂÒÚË Î˛·ÓÂL2 -ÔÓÒÚ‡ÌÒÚ‚Ó Ë Î˛·Ó ÍÓ̘ÌÓÏÂÌÓ ÔÓÒÚ‡ÌÒÚ‚Ó ÒÓ Ò͇ÎflÌ˚Ï ÔÓËÁ‚‰ÂÌËÂÏ.
Ç ˜‡ÒÚÌÓÒÚË, β·Ó ‚ÍÎË‰Ó‚Ó ÔÓÒÚ‡ÌÒÚ‚Ó fl‚ÎflÂÚÒfl „Ëθ·ÂÚÓ‚˚Ï.èflÏÓ ÔÓËÁ‚‰ÂÌË ‰‚Ûı „Ëθ·ÂÚÓ‚˚ı ÔÓÒÚ‡ÌÒÚ‚ ̇Á˚‚‡˛Ú ÔÓÒÚ‡ÌÒÚ‚ÓÏ ãËÛ‚ËÎÎfl (ËÎË ‡Ò¯ËÂÌÌ˚Ï „Ëθ·ÂÚÓ‚˚Ï ÔÓÒÚ‡ÌÒÚ‚ÓÏ).åÂÚË͇ ÌÓÏ˚ êËÒÒ‡èÓÒÚ‡ÌÒÚ‚Ó êËÒÒ‡ (ËÎË ‚ÂÍÚÓ̇fl ¯ÂÚ͇) ÂÒÚ¸ ˜‡ÒÚ˘ÌÓ ÛÔÓfl‰Ó˜ÂÌÌÓ‚ÂÍÚÓÌÓ ÔÓÒÚ‡ÌÒÚ‚Ó (VRi , p− ), ‚ ÍÓÚÓÓÏ ‚˚ÔÓÎÌfl˛ÚÒfl ÒÎÂ‰Û˛˘Ë ÛÒÎÓ‚Ëfl:1. ëÚÛÍÚÛ‡ ‚ÂÍÚÓÌÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ Ë ˜‡ÒÚ˘ÌÓ ÛÔÓfl‰Ó˜ÂÌ̇fl ÒÚÛÍÚÛ‡ÒÓ‚ÏÂÒÚËÏ˚, Ú.Â. ËÁ x p− y ÒΉÛÂÚ, ˜ÚÓ x + z p− y + z, ‡ ËÁ x f 0, a ∈ , a > 0 ÒΉÛÂÚ,˜ÚÓ ax f 0.2. ÑÎfl ‰‚Ûı β·˚ı ˝ÎÂÏÂÌÚÓ‚ x, y ∈ VRi ÒÛ˘ÂÒÚ‚ÛÂÚ Ó·˙‰ËÌÂÌË x ∧ y ∈ VRi ËÔÂÂÒ˜ÂÌË (ÒÏ.
„Î. 10).åÂÚË͇ ÌÓÏ˚ êËÒÒ‡ ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ ̇ VRi, Á‡‰‡‚‡Âχfl ͇Í|| x − y || Ri ,„‰Â || ⋅ || Ri ÂÒÚ¸ ÌÓχ êËÒÒ‡ ̇ V Ri , Ú.Â. ڇ͇fl ÌÓχ, ˜ÚÓ ‰Îfl ‚ÒÂı x, y ∈ VRi ̇‚ÂÌÒÚ‚Ó | x | p− | y |, „‰Â | x | = ( − x ) ∨ ( x ), ÔÓÓʉ‡ÂÚ Ì‡‚ÂÌÒÚ‚Ó || x || Ri ≤ || y || Ri .èÓÒÚ‡ÌÒÚ‚Ó (VRi , || ⋅ || Ri ) ̇Á˚‚‡ÂÚÒfl ÌÓÏËÓ‚‡ÌÌ˚Ï ÔÓÒÚ‡ÌÒÚ‚ÓÏ êËÒÒ‡.Ç ÒÎÛ˜‡Â ÔÓÎÌÓÚ˚ ÓÌÓ Ì‡Á˚‚‡ÂÚÒfl ·‡Ì‡ıÓ‚ÓÈ Â¯ÂÚÍÓÈ.äÓÏÔ‡ÍÚ Å‡Ì‡ı‡–å‡ÁÛ‡ê‡ÒÒÚÓflÌË Ň̇ı‡–å‡ÁÛ‡ dBM ÏÂÊ‰Û ‰‚ÛÏfl n-ÏÂÌ˚ÏË ÌÓÏËÓ‚‡ÌÌ˚ÏË ÔÓÒÚ‡ÌÒÚ‚‡ÏË (V , || ⋅ ||V ) Ë (W , || ⋅ ||W ) ÓÔ‰ÂÎflÂÚÒfl ͇Íln inf || T || ⋅ || T −1 ||,T85É·‚‡ 5. åÂÚËÍË Ì‡ ÌÓÏËÓ‚‡ÌÌ˚ı ÒÚÛÍÚÛ‡ı„‰Â ËÌÙËÏÛÏ ·ÂÂÚÒfl ÔÓ ‚ÒÂÏ ËÁÓÏÓÙËÁÏ‡Ï T : V → W .
éÌÓ fl‚ÎflÂÚÒfl ÏÂÚËÍÓÈ Ì‡ÏÌÓÊÂÒÚ‚Â Xn ‚ÒÂı Í·ÒÒÓ‚ ˝Í‚Ë‚‡ÎÂÌÚÌÓÒÚË n-ÏÂÌ˚ı ÌÓÏËÓ‚‡ÌÌ˚ı ÔÓÒÚ‡ÌÒÚ‚, „‰Â V ~ W ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ ÓÌË ËÁÓÏÓÙÌ˚. íÓ„‰‡ Ô‡‡( X n , dBM ) fl‚ÎflÂÚÒfl ÍÓÏÔ‡ÍÚÌ˚Ï ÏÂÚ˘ÂÒÍËÏ ÔÓÒÚ‡ÌÒÚ‚ÓÏ, ̇Á˚‚‡ÂÏ˚Ï ÍÓÏÔ‡ÍÚÓÏ Å‡Ì‡ı‡–å‡ÁÛ‡.î‡ÍÚÓ-ÏÂÚËÍ‡Ç ÒÎÛ˜‡Â ÌÓÏËÓ‚‡ÌÌÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ (V , || ⋅ ||V ) Ò ÌÓÏÓÈ || ⋅ ||V Ë Á‡ÏÍÌÛÚ˚ÏÔÓ‰ÔÓÒÚ‡ÌÒÚ‚ÓÏ W ÔÓÒÚ‡ÌÒÚ‚‡ V ÔÛÒÚ¸ (V / W , || ⋅ ||V / W ) ·Û‰ÂÚ ÌÓÏËÓ‚‡ÌÌ˚ÏÔÓÒÚ‡ÌÒÚ‚ÓÏ ÒÏÂÊÌ˚ı Í·ÒÒÓ‚ x + W = {x + w : w ∈ W}, x ∈ V Ò Ù‡ÍÚÓ-ÌÓÏÓÈ|| x + W ||V / VW = infw ∈W || x + w ||V .î‡ÍÚÓ-ÏÂÚËÍÓÈ Ì‡Á˚‚‡ÂÚÒfl ÏÂÚË͇ ÌÓÏ˚ ̇ V/W, Á‡‰‡Ì̇fl ͇Í|| ( x + W ) − ( y + W ) ||V / W .åÂÚË͇ ÚÂÌÁÓÌÓÈ ÌÓÏ˚ÑÎfl ÌÓÏËÓ‚‡ÌÌ˚ı ÔÓÒÚ‡ÌÒÚ‚ (V , || ⋅ ||V ) Ë (W , || ⋅ ||W ) ÌÓχ || ⋅ ||⊗ ̇ ÚÂÌÁÓÌÓÏ ÔÓËÁ‚‰ÂÌËË V ⊗ W ̇Á˚‚‡ÂÚÒfl ÚÂÌÁÓÌÓÈ ÌÓÏÓÈ (ËÎË ÍÓÒÒ-ÌÓÏÓÈ),ÂÒÎË || x ⊗ y ||⊗ = || x ||V || y ||W ‰Îfl ‚ÒÂı ‡ÁÎÓÊËÏ˚ı ÚÂÌÁÓÓ‚ x ⊗ y.åÂÚË͇ ÚÂÌÁÓÌÓÈ ÌÓÏ˚ ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ ̇ V ⊗ W , Á‡‰‡Ì̇fl ͇Í|| z − t ||⊗ .ÑÎfl β·˚ı z ∈ V ⊗ W , z =∑ x j ⊗ yj,jπ-ÌÓχ) ÓÔ‰ÂÎflÂÚÒfl Í‡Í || z || pr = infx j ∈ V , y j ∈ W  ÔÓÂÍÚ˂̇fl ÌÓχ (ËÎË∑ || x j ||V || y j ||W ,„‰Â ËÌÙËÏÛÏ ·ÂÂÚÒfl ÔÓj‚ÒÂÏ Ô‰ÒÚ‡‚ÎÂÌËflÏ z ‚ ‚ˉ ÒÛÏÏ˚ ‡ÁÎÓÊËÏ˚ı ‚ÂÍÚÓÓ‚.
ùÚÓ Ò‡Ï‡fl ·Óθ¯‡flÚÂÌÁÓ̇fl ÌÓχ ̇ V ⊗ W .åÂÚË͇ ‚‡Î˛‡ˆËËåÂÚË͇ ‚‡Î˛‡ˆËË – ˝ÚÓ ÏÂÚË͇ ̇ ÔÓΠ, Á‡‰‡Ì̇fl ͇Í|| x − y ||,„‰Â || ⋅ || – ‚‡Î˛‡ˆËfl ̇ , Ú.Â. ÙÛÌ͈Ëfl || ⋅ ||: → , ڇ͇fl ˜ÚÓ ‰Îfl ‚ÒÂı x, y ∈ ËϲÚÏÂÒÚÓ ÒÎÂ‰Û˛˘Ë ҂ÓÈÒÚ‚‡:1) || x || ≥ 0 Ò || x || = 0 ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ x = 0;2) || xy || = || x || || y ||;3) || x + y || ≤ || x || || y || ̇‚ÂÌÒÚ‚Ó ÚÂÛ„ÓθÌË͇).ÖÒÎË || x + y || ≤ max{|| x || || y ||}, ÚÓ ‚‡Î˛‡ˆËfl || ⋅ || ̇Á˚‚‡ÂÚÒfl ̇ıËωӂÓÈ.Ç ˝ÚÓÏ ÒÎÛ˜‡Â ÏÂÚË͇ ‚‡Î˛‡ˆËË ·Û‰ÂÚ ÛθڇÏÂÚËÍÓÈ.
èÓÒÚÂȯËÏ ÔËÏÂÓÏ‚‡Î˛‡ˆËË fl‚ÎflÂÚÒfl Ú˂ˇθÌÓ ÌÓÏËÓ‚‡ÌË || ⋅ ||tr : || 0 ||tr = 0 Ë || ⋅ ||tr = 1 ‰Îflx ∈ \ {0}, ÍÓÚÓÓ fl‚ÎflÂÚÒfl ̇ıËωӂ˚Ï.Ç Ï‡ÚÂχÚËÍ ÒÛ˘ÂÒÚ‚Û˛Ú ‡ÁÌ˚ ÓÔ‰ÂÎÂÌËfl ÔÓÌflÚËfl ‚‡Î˛‡ˆËË. í‡Í,̇ÔËÏÂ, ÙÛÌ͈Ëfl ν : → ∪ {∞} ̇Á˚‚‡ÂÚÒfl ‚‡Î˛‡ˆËÂÈ, ÂÒÎË ν( x ) ≥ 0, ν(0) = ∞,ν( xy) = ν( x ) + ν( y) Ë ν( x + y) ≥ min{ν( x ), ν( y)} ‰Îfl ‚ÒÂı x, y ∈. LJβ‡ˆË˛ || ⋅ ||ÏÓÊÌÓ ÔÓÎÛ˜ËÚ¸ ËÁ ÙÛÌ͈ËË ν ÔÓ ÙÓÏÛΠ|| x || = α ν( x ) ‰Îfl ÌÂÍÓÚÓÓ„Ó ÙËÍÒË-86ó‡ÒÚ¸ I. å‡ÚÂχÚË͇ ‡ÒÒÚÓflÌËÈÓ‚‡ÌÌÓ„Ó 0 < α < 1 (ÒÏ.
p-‡‰Ë˜ÂÒ͇fl ÏÂÚË͇, „Î. 12). LJβ‡ˆËfl äÛ¯‡Í‡ | ⋅ |KrsÁ‡‰‡ÂÚÒfl Í‡Í ÙÛÌ͈Ëfl | ⋅ |Krs : → , ڇ͇fl ˜ÚÓ | x |Krs ≥ 0, | x |Krs = 0 ÚÓ„‰‡ Ë ÚÓθÍÓÚÓ„‰‡, ÍÓ„‰‡ x = 0, | x |Krs = | x |Krs | y |Krs Ë | x + y |Krs ≤ C max{| x |Krs , | y |Krs} ‰Îfl ‚ÒÂıx, y ∈ Ë ‰Îfl ÌÂÍÓÚÓÓÈ ÔÓÎÓÊËÚÂθÌÓÈ ÍÓÌÒÚ‡ÌÚ˚ ë, ̇Á˚‚‡ÂÏÓÈ ÍÓÌÒÚ‡ÌÚÓÈ‚‡Î˛‡ˆËË.
ÖÒÎË C ≥ 2, ÚÓ ÔÓÎÛ˜‡ÂÚÒfl Ó·˚˜ÌÓ ÓÔ‰ÂÎÂÌË ‚‡Î˛‡ˆËË || ⋅ ||, ÍÓÚÓÓ·ۉÂÚ Ì‡ıËωӂ˚Ï, ÂÒÎË ë ≤ 1. Ç ˆÂÎÓÏ Î˛·‡fl ‚‡Î˛‡ˆËfl | ⋅ |Krs ˝Í‚Ë‚‡ÎÂÌÚ̇ÌÂÍÓÚÓÓÈ ‚‡Î˛‡ˆËË || ⋅ ||, Ú.Â. | ⋅ |Krs ÔË ÌÂÍÓÚÓÓÏ p > 0. à ̇ÍÓ̈, ‰Îfl ÛÔÓfl‰Ó˜ÂÌÌÓÈ „ÛÔÔ˚ (G, ⋅, e, ≤), Ò̇·ÊÂÌÌÓÈ ÌÛÎÂÏ, ‚‡Î˛‡ˆËfl äÛη ÓÔ‰ÂÎflÂÚÒflÍ‡Í ÙÛÌ͈Ëfl | ⋅ |: → G, ڇ͇fl ˜ÚÓ | x | = 0 ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ x = 0,| xy | = | x | | y | Ë | x + y | ≤ max{| x |, | y |} ‰Îfl β·˚ı x, y ∈.
ùÚÓ fl‚ÎflÂÚÒfl Ó·Ó·˘ÂÌËÂÏÓÔ‰ÂÎÂÌËfl ̇ıËωӂÓÈ ‚‡Î˛‡ˆËË || ⋅ || (ÒÏ. é·Ó·˘ÂÌ̇fl ÏÂÚË͇, „Î. 3).påÂÚË͇ ÒÚÂÔÂÌÌÓ„Ó fl‰‡èÛÒÚ¸ – ÔÓËÁ‚ÓθÌÓ ‡Î„·‡Ë˜ÂÒÍÓ ÔÓÎÂ Ë ÔÛÒÚ¸ 〈 x −1 〉 – ÔÓΠÒÚÂÔÂÌÌ˚ıfl‰Ó‚ ‚ˉ‡ w = α − m x m + ... + α 0 + α1 x + ..., α i ∈. èË Á‡‰‡ÌÌÓÏ l > 1 ̇ıËωӂ‡‚‡Î˛‡ˆËfl || ⋅ || ̇ 〈 x −1 〉 ÓÔ‰ÂÎflÂÚÒfl ͇Íl m , ÂÒÎË w ≠ 0,|| w || = 0, ÂÒÎË w = 0.åÂÚË͇ ÒÚÂÔÂÌÌÓ„Ó fl‰‡ ÂÒÚ¸ ÏÂÚË͇ ‚‡Î˛‡ˆËË || w − v || ̇ 〈 x −1 〉.ó‡ÒÚ¸ IIÉÖéåÖíêàü à êÄëëíéüçàüÉ·‚‡ 6ê‡ÒÒÚÓflÌËfl ‚ „ÂÓÏÂÚËËÉÂÓÏÂÚËfl ‚ÓÁÌËÍ· Í‡Í Ó·Î‡ÒÚ¸ Á̇ÌËÈ, Ò‚flÁ‡Ì̇fl Ò ‡Á΢Ì˚ÏË ÒÓÓÚÌÓ¯ÂÌËflÏË‚ ÔÓÒÚ‡ÌÒÚ‚Â.
ùÚÓ ·˚· Ӊ̇ ËÁ ‰‚Ûı ӷ·ÒÚÂÈ, Ô‰¯ÂÒÚ‚Ó‚‡‚¯Ëı ÒÓ‚ÂÏÂÌÌÓÈχÚÂχÚËÍÂ, ‚ÚÓ‡fl Á‡ÌËχ·Ҹ ËÁÛ˜ÂÌËÂÏ ˜ËÒÂÎ. Ç Ì‡ÒÚÓfl˘Â ‚ÂÏfl „ÂÓÏÂÚ˘ÂÒÍË ÍÓ̈ÂÔˆËË ‰ÓÒÚË„ÎË ‚ÂҸχ ‚˚ÒÓÍÓ„Ó ÛÓ‚Ìfl ‡·ÒÚ‡ÍÚÌÓÒÚË Ë ÒÎÓÊÌÓÒÚËÓ·Ó·˘ÂÌËÈ.6.1. ÉÖéÑÖáàóÖëäÄü ÉÖéåÖíêàüÇ Ï‡ÚÂχÚËÍ ÔÓÌflÚË "„ÂÓ‰ÂÁ˘ÂÒÍËÈ" fl‚ÎflÂÚÒfl Ó·Ó·˘ÂÌËÂÏ ÔÓÌflÚËfl "ÔflχflÎËÌËfl" ÔÓ ÓÚÌÓ¯ÂÌ˲ Í ËÒÍË‚ÎÂÌÌÓÏÛ ÔÓÒÚ‡ÌÒÚ‚Û.
чÌÌ˚È ÚÂÏËÌ Á‡ËÏÒÚ‚Ó‚‡ÌËÁ „ÂÓ‰ÂÁËË, ̇ÛÍË, Á‡ÌËχ˛˘ÂÈÒfl ËÁÏÂÂÌËÂÏ ‡Áχ Ë ÙÓÏ˚ áÂÏÎË.èÛÒÚ¸ (ï, d) – ÔÓËÁ‚ÓθÌÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó. åÂÚ˘ÂÒ͇fl ÍË‚‡fl γÂÒÚ¸ ÌÂÔÂ˚‚̇fl ÙÛÌ͈Ëfl γ : I → X, „‰Â I – ËÌÚ‚‡Î (Ú.Â. ÌÂÔÛÒÚÓ ҂flÁÌÓÂÔÓ‰ÏÌÓÊÂÒÚ‚Ó) ‚ . ÖÒÎË γ fl‚ÎflÂÚÒfl r ‡Á ÌÂÔÂ˚‚ÌÓ ‰ËÙÙÂÂ̈ËÛÂÏÓÈ, ÚÓ Ó̇̇Á˚‚‡ÂÚÒfl „ÛÎflÌÓÈ ÍË‚ÓÈ Í·ÒÒ‡ Cr; ÂÒÎË r = ∞, ÚÓ γ ̇Á˚‚‡ÂÚÒfl „·‰ÍÓÈÍË‚ÓÈ.ÇÓÓ·˘Â „Ó‚Ófl, ÍË‚‡fl ÎËÌËfl ÏÓÊÂÚ ÔÂÂÒÂ͇ڸ Ò‡ÏÛ Ò·fl.
äË‚‡fl ·Û‰ÂÚ Ì‡Á˚‚‡Ú¸Òfl ÔÓÒÚÓÈ ÍË‚ÓÈ (ËÎË ‰Û„ÓÈ, ÔÛÚÂÏ), ÂÒÎË Ó̇ Ì ÔÂÂÒÂ͇ÂÚ Ò‡ÏÛ Ò·fl,Ú.Â. fl‚ÎflÂÚÒfl ËÌ˙ÂÍÚË‚ÌÓÈ. äË‚‡fl γ: [a, b] → X ̇Á˚‚‡ÂÚÒfl ÊÓ‰‡ÌÓ‚ÓÈ ÍË‚ÓÈ(ËÎË ÔÓÒÚÓÈ Á‡ÏÍÌÛÚÓÈ ÍË‚ÓÈ), ÂÒÎË Ó̇ Ì ÔÂÂÒÂ͇ÂÚ Ò·fl Ë γ(‡) = γ(b).ÑÎË̇ (ÍÓÚÓ‡fl ÏÓÊÂÚ ·˚Ú¸ ‡‚̇ ∞) l(γ) ÍË‚ÓÈ (γ: [a, b] → X ÓÔ‰ÂÎflÂÚÒfl ͇Ínsup∑ d(γ (ti −1 ), γ (ti )),„‰Â ‚ÂıÌflfl „‡Ì¸ ·ÂÂÚÒfl ÔÓ ‚ÒÂÏ ÍÓ̘Ì˚Ï ‡Á·ËÂÌËflÏi =1a = t0 < t1 < ... < tn = b, n ∈ ÓÚÂÁ͇ [a, b]. äË‚‡fl ÍÓ̘ÌÓÈ ‰ÎËÌ˚ ̇Á˚‚‡ÂÚÒflÒÔflÏÎflÂÏÓÈ. ÑÎfl β·ÓÈ Â„ÛÎflÌÓÈ ÍË‚ÓÈ γ: [a, b] → X Á‡‰‡‰ËÏ Ì‡ÚۇθÌ˚ÈÔ‡‡ÏÂÚ s ÍË‚ÓÈ γ Í‡Í s = s(t ) = l( γ | [ a,t ] ), „‰Â l( γ | [ a,t ] ) ÂÒÚ¸ ‰ÎË̇ ˜‡ÒÚË γ,ÒÓÓÚ‚ÂÚÒÚ‚Û˛˘ÂÈ ËÌÚ‚‡ÎÛ [a, t].
äË‚‡fl Ò Ú‡ÍÓÈ Ì‡ÚۇθÌÓÈ Ô‡‡ÏÂÚËÁ‡ˆËÂÈγ = γ(s) ̇Á˚‚‡ÂÚÒfl ÍË‚ÓÈ Â‰ËÌ˘ÌÓÈ ÒÍÓÓÒÚË (ËÎË Ô‡‡ÏÂÚËÁÓ‚‡ÌÌÓÈ ‰ÎËÌÓȉۄË, ÌÓÏËÓ‚‡ÌÌÓÈ); ÔË ‰‡ÌÌÓÈ Ô‡‡ÏÂÚËÁ‡ˆËË ‰Îfl β·˚ı t1 , t2 ∈ I ÔÓÎÛ˜‡ÂÏl( γ |[t1 , t 2 ] ) = | t2 − t1 | Ë l( γ ) = | b − a | .ÑÎË̇ β·ÓÈ ÍË‚ÓÈ γ: [a, b] → X ‡‚̇ ÔÓ ÏÂ̸¯ÂÈ Ï ‡ÒÒÚÓflÌ˲ ÏÂÊ‰Û ÂÂÍÓ̈‚˚ÏË ÚӘ͇ÏË: l( γ ) ≥ d ( γ ( a), γ (b)). äË‚‡fl γ, ‰Îfl ÍÓÚÓÓÈ l( γ ) = d ( γ ( a), γ (b)),̇Á˚‚‡ÂÚÒfl „ÂÓ‰ÂÁ˘ÂÒÍËÏ ÓÚÂÁÍÓÏ (ËÎË Í‡Ú˜‡È¯ËÏ ÔÛÚÂÏ) ÓÚ ı = γ(‡) ‰Ó Û = γ(b)Ë Ó·ÓÁ̇˜‡ÂÚÒfl Í‡Í [x, y]. í‡ÍËÏ Ó·‡ÁÓÏ, „ÂÓ‰ÂÁ˘ÂÒÍËÈ ÓÚÂÁÓÍ ÂÒÚ¸ ͇ژ‡È¯ËÈÔÛÚ¸ ÏÂÊ‰Û Â„Ó ÍÓ̈‚˚ÏË ÚӘ͇ÏË; ÓÌ fl‚ÎflÂÚÒfl ËÁÓÏÂÚ˘ÂÒÍËÏ ‚ÎÓÊÂÌËÂÏ [a, b]‚ ï. Ç ˆÂÎÓÏ „ÂÓ‰ÂÁ˘ÂÒÍË ÓÚÂÁÍË ÏÓ„ÛÚ Ë Ì ÒÛ˘ÂÒÚ‚Ó‚‡Ú¸, ÍÓÏ Ú˂ˇθÌÓ„ÓÒÎÛ˜‡fl, ÍÓ„‰‡ ÓÚÂÁÓÍ ÒÓÒÚÓËÚ ÚÓθÍÓ ËÁ Ó‰ÌÓÈ ÚÓ˜ÍË.
ÅÓΠÚÓ„Ó, „ÂÓ‰ÂÁ˘ÂÒÍËÈÓÚÂÁÓÍ, ÒÓ‰ËÌfl˛˘ËÈ ‰‚ ÚÓ˜ÍË, Ì ӷflÁ‡ÚÂθÌÓ Â‰ËÌÒÚ‚ÂÌ.É·‚‡ 6. ê‡ÒÒÚÓflÌËfl ‚ „ÂÓÏÂÚËË89ÉÂÓ‰ÂÁ˘ÂÒÍÓÈ Ì‡Á˚‚‡ÂÚÒfl ÍË‚‡fl, ÍÓÚÓ‡fl ·ÂÒÍÓ̘ÌÓ ‡ÒÔÓÒÚ‡ÌflÂÚÒfl ‚ Ó·ÂÒÚÓÓÌ˚ Ë ÎÓ͇θÌÓ ‚‰ÂÚ Ò·fl Í‡Í ÓÚÂÁÓÍ, Ú.Â. ÎÓ͇θÌÓ ‚Ò˛‰Û fl‚ÎflÂÚÒfl ÏËÌËÏËÁ‡ÚÓÓÏ ‡ÒÒÚÓflÌËfl. íӘ̠„Ó‚Ófl, ÍË‚‡fl γ: → X ‚ ÂÒÚÂÒÚ‚ÂÌÌÓÈ Ô‡‡ÏÂÚËÁ‡ˆËË Ì‡Á˚‚‡ÂÚÒfl „ÂÓ‰ÂÁ˘ÂÒÍÓÈ, ÂÒÎË ‰Îfl β·Ó„Ó t ∈ ÒÛ˘ÂÒÚ‚ÛÂÚ Ú‡Í‡fl ÓÍÂÒÚÌÓÒÚ¸ U, ˜ÚÓ ‰Îfl β·˚ı t1 , t2 ∈ U ËÏÂÂÏ d ( γ (t1 ), γ (t2 )) = | t1 − t2 | .