Е. Деза_ М.М. Деза. Энциклопедический словарь расстояний (2008) (1185330), страница 39
Текст из файла (страница 39)
ê‡ÒÒÚÓflÌËfl ‚ ‡Î„·ÂåÂÚË͇ (‚ Ó·˘ÂÏ ÒÎÛ˜‡Â – ÔÓÎÛÏÂÚË͇) d ̇ „ÛÔÔ (G, ⋅, e) ̇Á˚‚‡ÂÚÒfl ΂ÓËÌ‚‡Ë‡ÌÚÌÓÈ, ÂÒÎË ‡‚ÂÌÒÚ‚Ó d(x, y) = d (z ⋅ x , z ⋅ y) ÒÔ‡‚‰ÎË‚Ó ‰Îfl β·˚ıx, y, z ∈ G, Ú.Â. ÓÔ‡ˆËfl ÎÂ‚Ó„Ó ÛÏÌÓÊÂÌËfl ̇ ˝ÎÂÏÂÌÚ z fl‚ÎflÂÚÒfl ‰‚ËÊÂÌËÂÏÏÂÚ˘ÂÒÍÓ„Ó ÔÓÒÚ‡ÌÒÚ‚‡ (G, d).
ã˛·‡fl ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚, ÓÔ‰ÂÎflÂχflÍ‡Í || y ⋅ x–1 ||, fl‚ÎflÂÚÒfl ΂ÓËÌ‚‡Ë‡ÌÚÌÓÈ.ã˛·‡fl Ô‡‚Ó‚‡Ë‡ÌÚ̇fl, ‡‚ÌÓ Í‡Í Ë Î‚ÓËÌ‚‡Ë‡ÌÚ̇fl, ‚ ˜‡ÒÚÌÓÒÚË, β·‡fl·ËËÌ‚‡Ë‡ÌÚ̇fl ÏÂÚË͇ d ̇ G fl‚ÎflÂÚÒfl ÏÂÚËÍÓÈ ÌÓÏ˚ „ÛÔÔ˚, ÔÓÒÍÓθÍÛÌÓÏÛ „ÛÔÔ˚ ̇ G ÏÓÊÌÓ Á‡‰‡Ú¸ Í‡Í || x || = d(x, 0).èÓÎÓÊËÚÂθÌÓ Ó‰ÌÓӉ̇fl ÏÂÚË͇åÂÚË͇ (‚ Ó·˘ÂÏ ÒÎÛ˜‡Â – ‡ÒÒÚÓflÌËÂ) d ̇ ‡·Â΂ÓÈ „ÛÔÔ (G, +, 0) ̇Á˚‚‡ÂÚÒfl ÔÓÎÓÊËÚÂθÌÓ Ó‰ÌÓÓ‰ÌÓÈ, ÂÒÎË ‡‚ÂÌÒÚ‚Ód(mx, my) = md(x, y)ÒÔ‡‚‰ÎË‚Ó ‰Îfl ‚ÒÂı x, y ∈ G Ë ‚ÒÂı m ∈ , „‰Â mx – ÒÛÏχ m ˝ÎÂÏÂÌÚÓ‚, ͇ʉ˚È ËÁÍÓÚÓ˚ı ‡‚ÂÌ ı.ÑËÒÍÂÚ̇fl ÔÂÂÌÓÒ‡ ÏÂÚË͇åÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚ (‚ Ó·˘ÂÏ ÒÎÛ˜‡Â – ÔÓÎÛÏÂÚË͇ ÔÓÎÛÌÓÏ˚ „ÛÔÔ˚) ̇„ÛÔÔ (G , ⋅ , e) ̇Á˚‚‡ÂÚÒfl ‰ËÒÍÂÚÌÓÈ ÏÂÚËÍÓÈ ÔÂÂÌÓÒ‡, ÂÒÎË ‡ÒÒÚÓflÌËflÔÂÂÌÓÒ‡ (ËÎË ˜ËÒ· ÔÂÂÌÓÒ‡)|| x n ||n →∞nτ G ( x ) = lim˝ÎÂÏÂÌÚÓ‚ ı ·ÂÁ ÍÛ˜ÂÌËfl (Ú.Â. Ú‡ÍËı, ˜ÚÓ xn ≠ e ‰Îfl β·Ó„Ó n ∈ ) ÔÓ ÓÚÌÓ¯ÂÌ˲ Í˝ÚÓÈ ÏÂÚËÍ fl‚Îfl˛ÚÒfl ÓÚ‰ÂÎÂÌÌ˚ÏË ÓÚ ÌÛÎfl.ÖÒÎË ˜ËÒ· τ G(x) fl‚Îfl˛ÚÒfl ÌÂÌÛ΂˚ÏË, ÚÓ Ú‡Í‡fl ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚̇Á˚‚‡ÂÚÒfl ÒÓ·ÒÚ‚ÂÌÌÓÈ ÏÂÚËÍÓÈ ÔÂÂÌÓÒ‡.ëÎÓ‚‡Ì‡fl ÏÂÚË͇èÛÒÚ¸ (G, ⋅, e) – ÍÓ̘ÌÓ ÔÓÓʉÂÌ̇fl „ÛÔÔ‡ Ò ÏÌÓÊÂÒÚ‚ÓÏ Ä ÔÓÓʉ‡˛˘Ëı˝ÎÂÏÂÌÚÓ‚.
ëÎÓ‚‡Ì‡fl ‰ÎË̇ wWA ( x ) ˝ÎÂÏÂÌÚ‡ x ∈ G\{e} ÓÔ‰ÂÎflÂÚÒfl ͇ÍwWA ( x ) = inf{r : x = a1a1 ...arar , ai ∈ A, ei ∈{±1}},Ë wWA (e) = 0.ëÎÓ‚‡Ì‡fl ÏÂÚË͇ dWA , ÒÓÓÚ‚ÂÚÒÚ‚Û˛˘‡fl ÏÌÓÊÂÒÚ‚Û Ä, ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚„ÛÔÔ˚ ̇ G, ÓÔ‰ÂÎflÂχfl ͇ÍwWA ( x ⋅ y −1 ),í‡Í Í‡Í ÒÎÓ‚‡Ì‡fl ‰ÎË̇ wWA fl‚ÎflÂÚÒfl ÌÓÏÓÈ „ÛÔÔ˚ ̇ G, ÚÓ dWA Ô‡‚ÓËÌ‚‡Ë‡ÌÚ̇. àÌÓ„‰‡ Ó̇ ÓÔ‰ÂÎflÂÚÒfl Í‡Í wWA ( y −1 ⋅ x ), Ë ÚÓ„‰‡ Ó̇ ÒÚ‡ÌÓ‚ËÚÒfl ΂ÓËÌ‚‡Ë‡ÌÚÌÓÈ. àÏÂÌÌÓ, dWA – ˝ÚÓ Ï‡ÍÒËχθ̇fl ÏÂÚË͇ ̇ G, ÍÓÚÓ‡fl fl‚ÎflÂÚÒflÔ‡‚Ó‚‡Ë‡ÌÚÌÓÈ Ë Ó·Î‡‰‡ÂÚ ÚÂÏ Ò‚ÓÈÒÚ‚ÓÏ, ˜ÚÓ ‡ÒÒÚÓflÌË ÓÚ Î˛·Ó„Ó ˝ÎÂÏÂÌÚ‡ ËÁÄ ËÎË ËÁ Ä–1 ‰Ó ‰ËÌ˘ÌÓ„Ó ˝ÎÂÏÂÌÚ‡  ‡‚ÌÓ Â‰ËÌˈÂ.ÖÒÎË Ä Ë Ç – ‰‚‡ ÍÓ̘Ì˚ı ÏÌÓÊÂÒÚ‚‡ ÔÓÓʉ‡˛˘Ëı ˝ÎÂÏÂÌÚÓ‚ „ÛÔÔ˚ (G, ⋅, e),ÚÓ ÚÓʉÂÒÚ‚ÂÌÌÓ ÓÚÓ·‡ÊÂÌË ÏÂÊ‰Û ÏÂÚ˘ÂÒÍËÏË ÔÓÒÚ‡ÌÒÚ‚‡ÏË (G, dWA ) Ë170ó‡ÒÚ¸ III.
ê‡ÒÒÚÓflÌËfl ‚ Í·ÒÒ˘ÂÒÍÓÈ Ï‡ÚÂχÚËÍÂ(G, dWB ) fl‚ÎflÂÚÒfl Í‚‡ÁËËÁÓÏÂÚËÂÈ, Ú.Â. ÒÎÓ‚‡Ì‡fl ÏÂÚË͇ ‰ËÌÒÚ‚ÂÌa Ò ÚÓ˜ÌÓÒÚ¸˛‰Ó Í‚‡ÁËËÁÓÏÂÚËË.ëÎÓ‚‡Ì‡fl ÏÂÚË͇ – ÏÂÚË͇ ÔÛÚË „‡Ù‡ ä˝ÎË É „ÛÔÔ˚ (G, ⋅, e), ÔÓÒÚÓÂÌÌÓ„ÓÓÚÌÓÒËÚÂθÌÓ Ä. àÏÂÌÌÓ, É fl‚ÎflÂÚÒfl „‡ÙÓÏ Ò ÏÌÓÊÂÒÚ‚ÓÏ ‚¯ËÌ G, ‚ ÍÓÚÓÓω‚ ‚¯ËÌ˚ ı Ë y ∈ G ÒÓ‰ËÌÂÌ˚ ·ÓÏ ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ y = aεx, ε = ±1,a ∈ A.ÇÁ‚¯ÂÌ̇fl ÒÎÓ‚‡Ì‡fl ÏÂÚË͇èÛÒÚ¸ (G, ⋅, e) – ÍÓ̘ÌÓ ÔÓÓʉÂÌ̇fl „ÛÔÔ‡ Ò ÏÌÓÊÂÒÚ‚ÓÏ Ä ÔÓÓʉ‡˛˘Ëı˝ÎÂÏÂÌÚÓ‚. ÖÒÎË ËÏÂÂÚÒfl Ó„‡Ì˘ÂÌ̇fl ‚ÂÒÓ‚‡fl ÙÛÌ͈Ëfl w: A → (0, ∞ ), ÚÓA‚Á‚¯ÂÌ̇fl ÒÎÓ‚‡Ì‡fl ‰ÎË̇ wWW( x ) ˝ÎÂÏÂÌÚ‡ x ∈ G\{e} ÓÔ‰ÂÎflÂÚÒfl Í‡Í tAwWW( x ) = inf w( ai ), t ∈ : x = a1e1 ...atet , ai ∈ A, ei ∈{±1} , i =1∑AË wWW(e) = 0.A, ÒÓÓÚ‚ÂÚÒÚ‚Û˛˘‡fl Ä, ÂÒÚ¸ ÏÂÚË͇ÇÁ‚¯ÂÌ̇fl ÒÎÓ‚‡Ì‡fl ÏÂÚË͇ dWWÌÓÏ˚ „ÛÔÔ˚ ̇ G, ÓÔ‰ÂÎÂÌ̇fl ͇ÍA( x ⋅ y −1 ).wWWAèÓÒÍÓθÍÛ ‚Á‚¯ÂÌ̇fl ÒÎÓ‚‡Ì‡fl ‰ÎË̇ wWWfl‚ÎflÂÚÒfl ÌÓÏÓÈ „ÛÔÔ˚ ̇ G, ÚÓAAdWW·Û‰ÂÚ Ô‡‚ÓËÌ‚‡Ë‡ÌÚÌÓÈ.
àÌÓ„‰‡ Ó̇ Á‡‰‡ÂÚÒfl Í‡Í wWW( y −1 ⋅ x ) Ë ‚ ˝ÚÓÏÒÎÛ˜‡Â Ó̇ fl‚ÎflÂÚÒfl ΂ÓËÌ‚‡Ë‡ÌÚÌÓÈ.AåÂÚË͇ dWWfl‚ÎflÂÚÒfl ÒÛÔÂÏÛÏÓÏ ÔÓÎÛÏÂÚËÍ d ̇ G, ӷ·‰‡˛˘Ëı Ò‚ÓÈÒÚ‚ÓÏd(e, a) ≤ w(a) ‰Îfl β·Ó„Ó a ∈ A.AåÂÚË͇ dWWfl‚ÎflÂÚÒfl ÏÂÚËÍÓÈ ÛÔÓ˘ÂÌÌÓ„Ó ÔÛÚË, Ë Í‡Ê‰‡fl Ô‡‚ÓËÌ‚‡Ë‡ÌÚ̇fl ÏÂÚË͇ ÛÔÓ˘ÂÌÌÓ„Ó ÔÛÚË fl‚ÎflÂÚÒfl ‚ÂÒÓ‚ÓÈ ÒÎÓ‚‡ÌÓÈ ÏÂÚËÍÓÈ Ò ÚÓ˜ÌÓÒÚ¸˛ ‰Ó „Û·ÓÈ ËÁÓÏÂÚËË.AåÂÚË͇ dWWfl‚ÎflÂÚÒfl ÏÂÚËÍÓÈ ÔÛÚË ‚Á‚¯ÂÌÌÓ„Ó „‡Ù‡ ä˝ÎË ÉW „ÛÔÔ˚(G, ⋅, e), ÔÓÒÚÓÂÌÌÓ„Ó ÓÚÌÓÒËÚÂθÌÓ Ä.
àÏÂÌÌÓ, ÉW fl‚ÎflÂÚÒfl ‚Á‚¯ÂÌÌ˚Ï „‡ÙÓÏ ÒÏÌÓÊÂÒÚ‚ÓÏ ‚¯ËÌ G, ‚ ÍÓÚÓÓÏ ‰‚ ‚¯ËÌ˚ ı Ë y ∈ G ÒÓ‰ËÌÂÌ˚ ·ÓÏ Ò‚ÂÒÓÏ w(a) ÚÓ„‰‡ Ë ÚÓθÍÓ ÚÓ„‰‡, ÍÓ„‰‡ y = aεx, ε = ±1, a ∈ A.åÂÚË͇ ËÌÚ‚‡Î¸ÌÓÈ ÌÓÏ˚åÂÚË͇ ËÌÚ‚‡Î¸ÌÓÈ ÌÓÏ˚ ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚ ̇ ÍÓ̘ÌÓÈ „ÛÔÔÂ(G, ⋅, e), ÓÔ‰ÂÎÂÌ̇fl ͇Í|| x ⋅ y–1 || int,„‰Â || ⋅ ||int – ËÌÚ‚‡Î¸Ì‡fl ÌÓχ ̇ G, Ú.Â.
ڇ͇fl ÌÓχ „ÛÔÔ˚, ˜ÚÓ Á̇˜ÂÌËfl || ⋅ ||intÓ·‡ÁÛ˛Ú ÏÌÓÊÂÒÚ‚Ó ÔÓÒΉӂ‡ÚÂθÌ˚ı ˆÂÎ˚ı ˜ËÒÂÎ, ̇˜Ë̇fl Ò 0.ä‡Ê‰ÓÈ ËÌÚ‚‡Î¸ÌÓÈ ÌÓÏ || ⋅ ||int ÒÓÓÚ‚ÂÚÒÚ‚ÛÂÚ ÛÔÓfl‰Ó˜ÂÌÌÓ ‡Á·ËÂÌËÂ{B0 ,..., Bm} ÏÌÓÊÂÒÚ‚‡ G Ò Bi = {x ∈ G: || x ||int = i} (ÒÏ. ‡ÒÒÚÓflÌË ò‡Ï‡–äÓ¯Â͇,„Î. 16). çÓχ ï˝ÏÏËÌ„‡ Ë ÌÓχ ãË fl‚Îfl˛ÚÒfl ÓÒÓ·˚ÏË ÒÎÛ˜‡flÏË ËÌÚ‚‡Î¸ÌÓÈÌÓÏ˚.
é·Ó·˘ÂÌ̇fl ÌÓχ ãË – ËÌÚ‚‡Î¸Ì‡fl ÌÓχ, ‰Îfl ÍÓÚÓÓÈ Í‡Ê‰˚È Í·ÒÒËÏÂÂÚ ÙÓÏÛ Bi = {a, a –1}.171É·‚‡ 10. ê‡ÒÒÚÓflÌËfl ‚ ‡Î„·Âë-ÏÂÚË͇ë-ÏÂÚË͇ d – ÏÂÚË͇ ̇ „ÛÔÔ (G , ⋅ , e), Û‰Ó‚ÎÂÚ‚Ófl˛˘‡fl ÒÎÂ‰Û˛˘ËÏÛÒÎÓ‚ËflÏ:1) Á̇˜ÂÌËfl d Ó·‡ÁÛ˛Ú ÏÌÓÊÂÒÚ‚Ó ÔÓÒΉӂ‡ÚÂθÌ˚ı ˆÂÎ˚ı ˜ËÒÂÎ, ̇˜Ë̇fl Ò 0;2) ͇‰Ë̇θÌÓ ˜ËÒÎÓ ÒÙÂ˚ S(x, r) = {y ∈ G: d(x, y) = r} Ì Á‡‚ËÒËÚ ÓÚ ‚˚·Ó‡x ∈ G.ëÎÓ‚‡Ì‡fl ÏÂÚË͇, ı˝ÏÏË̄ӂ‡ ÏÂÚË͇ Ë ÏÂÚË͇ ãË fl‚Îfl˛ÚÒfl ë-ÏÂÚË͇ÏË.ã˛·‡fl ÏÂÚË͇ ËÌÚ‚‡Î¸ÌÓÈ ÌÓÏ˚ ÂÒÚ¸ ë-ÏÂÚË͇.åÂÚË͇ ÌÓÏ˚ ÔÓfl‰Í‡èÛÒÚ¸ (G, ⋅, e) – ÍÓ̘̇fl ‡·Â΂‡ „ÛÔÔ‡. èÛÒÚ¸ ord(x) – ÔÓfl‰ÓÍ ˝ÎÂÏÂÌÚ‡ x ∈ G,Ú.Â.
̇ËÏÂ̸¯Â ÔÓÎÓÊËÚÂθÌÓ ˆÂÎÓ ˜ËÒÎÓ n, Ú‡ÍÓ ˜ÚÓ xn = e. íÓ„‰‡ ÙÛÌ͈Ëfl|| ⋅ ||ord: G → , ÓÔ‰ÂÎÂÌ̇fl Í‡Í || ⋅ ||ord = lnord(x), fl‚ÎflÂÚÒfl ÌÓÏÓÈ „ÛÔÔ˚ ̇ G Ë̇Á˚‚‡ÂÚÒfl ÌÓÏÓÈ ÔÓfl‰Í‡.åÂÚË͇ ÌÓÏ˚ ÔÓfl‰Í‡ – ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚ ̇ G, ÓÔ‰ÂÎÂÌ̇fl ͇Í|| x ⋅ y–1 || ord.åÂÚË͇ ÌÓÏ˚ ÏÓÌÓÏÓÙËÁχèÛÒÚ¸ (G , +, 0) – „ÛÔÔa Ë (H , ⋅, e ) – „ÛÔÔa Ò ÌÓÏÓÈ „ÛÔÔ˚ || ⋅ ||H.
èÛÒÚ¸ f:G → H – ÏÓÌÓÏÓÙËÁÏ „ÛÔÔ G Ë H, Ú.Â. ËÌ˙ÂÍÚ˂̇fl ÙÛÌ͈Ëfl, ڇ͇fl ˜ÚÓ f(x + y) == f(x) ⋅ f(y ) ‰Îfl ‚ÒÂı x, y ∈ G . íÓ„‰‡ ÙÛÌ͈Ëfl || ⋅ ||Gf : G → , Á‡‰‡Ì̇fl ͇Í|| x ||Gf =|| f ( x ) || H , fl‚ÎflÂÚÒfl ÌÓÏÓÈ „ÛÔÔ˚ ̇ G Ë Ì‡Á˚‚‡ÂÚÒfl ÌÓÏÓÈ ÏÓÌÓÏÓÙËÁχ.åÂÚË͇ ÌÓÏ˚ ÏÓÌÓÏÓÙËÁχ – ÏÂÚËÍa ÌÓÏ˚ „ÛÔÔ˚ ̇ G, ÓÔ‰ÂÎflÂχfl ͇Í|| x − y ||Gf .åÂÚË͇ ÌÓÏ˚ ÔÓËÁ‚‰ÂÌËflèÛÒÚ¸ (G, +, 0) – „ÛÔÔa Ò ÌÓÏÓÈ „ÛÔÔ˚ || ⋅ ||G Ë (H , ⋅, e ) – „ÛÔÔa Ò ÌÓÏÓÈ„ÛÔÔ˚ || ⋅ ||H.
èÛÒÚ¸ G × H = {α = (x, y): x ∈ G, y ∈ H} – ‰Â͇ÚÓ‚Ó ÔÓËÁ‚‰ÂÌËÂG Ë H , Ë ÔÛÒÚ¸ (x, y) ⋅ (x, t) = (x + z, y ⋅ t). íÓ„‰‡ ÙÛÌ͈Ëfl || ⋅ ||G×H: G × H → ,ÓÔ‰ÂÎÂÌ̇fl Í‡Í || α ||G × H =|| ( x, y) ||G × H =|| x ||G + || y || H , , ÂÒÚ¸ ÌÓχ „ÛÔÔ˚ ̇ G × H,̇Á˚‚‡Âχfl ÌÓÏÓÈ ÔÓËÁ‚‰ÂÌËfl.åÂÚË͇ ÌÓÏ˚ ÔÓËÁ‚‰ÂÌËfl ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚, ÓÔ‰ÂÎÂÌ̇fl ͇Í|| α ⋅ β −1 ||G × F .ç‡ ‰Â͇ÚÓ‚ÓÏ ÔÓËÁ‚‰ÂÌËË G × H ‰‚Ûı ÍÓ̘Ì˚ı „ÛÔÔ Ò ËÌÚ‚‡Î¸Ì˚ÏËintÌÓχÏË || ⋅ ||Gint Ë || ⋅ ||intH ÏÓÊÂÚ ·˚Ú¸ Á‡‰‡Ì‡ ËÌÚ‚‡Î¸Ì‡fl ÌÓχ || ⋅ ||G × H . àÏÂÌÌÓ,|| α ||Gint× H =|| ( x, y ||Gint× H =|| x ||G +( m + 1) || y || H , „‰Â m = max a ∈G || a ||Gint .åÂÚË͇ Ù‡ÍÚÓ-ÌÓÏ˚èÛÒÚ¸ (G, ⋅, e) – „ÛÔÔa Ò ÌÓÏÓÈ „ÛÔÔ˚ || ⋅ ||G Ë (H, ⋅, e) – ÌÓχθ̇fl ÔÓ‰„ÛÔÔ‡„ÛÔÔ˚ (G, ⋅, e), xN = N x ‰Îfl β·˚ı x ∈ G. èÛÒÚ¸ (G/N, ⋅, eN) – Ù‡ÍÚÓ-„ÛÔÔ‡„ÛÔÔ˚ G, Ú.Â.
G/N = {xN: x ∈ G: Ò xN = {x ⋅ a: a ∈ N} Ë xN ⋅ yN = xyN. íÓ„‰‡ ÙÛÌ͈Ëfl|| ⋅ ||G / N : G / N → , Á‡‰‡Ì̇fl Í‡Í || xN ||G / N = min || xa || X , – ÌÓÏa „ÛÔÔ˚ G/N ̇ Ëa ∈ṄÁ˚‚‡Âχfl Ù‡ÍÚÓ-ÌÓÏÓÈ.172ó‡ÒÚ¸ III. ê‡ÒÒÚÓflÌËfl ‚ Í·ÒÒ˘ÂÒÍÓÈ Ï‡ÚÂχÚËÍÂåÂÚË͇ Ù‡ÍÚÓ-ÌÓÏ˚ ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚ ̇ G/N, ÓÔ‰ÂÎÂÌ̇fl ͇Í|| xN ⋅ ( yN ) −1 ||G / N =|| xy −1 N ||G / N .ÖÒÎË G = Ò ÌÓÏÓÈ, ‡‚ÌÓÈ ‡·ÒÓβÚÌÓÏÛ Á̇˜ÂÌ˲, Ë N = m , m ∈ , ÚÓÙ‡ÍÚÓ-ÌÓχ ̇ /m = m ÒÓ‚Ô‡‰‡ÂÚ Ò ÌÓÏÓÈ ãË.ÖÒÎË ÏÂÚË͇ d ̇ „ÛÔÔ (G, ⋅, e) Ô‡‚ÓËÌ‚‡Ë‡ÌÚÌa, ÚÓ ‰Îfl β·ÓÈ ÌÓχθÌÓÈÔÓ‰„ÛÔÔ˚ (N, ⋅, e) „ÛÔÔ˚ (G , ⋅, e) ÏÂÚË͇ d ÔÓÓʉ‡ÂÚ Ô‡‚ÓËÌ‚‡Ë‡ÌÚÌÛ˛ÏÂÚËÍÛ (ËÏÂÌÌÓ, ı‡ÛÒ‰ÓÙÓ‚Û ÏÂÚËÍÛ) d* ̇ G/N ÔÓ Á‡ÍÓÌÛd ∗ ( xN , yN ) = max max min d ( a, b), max min d ( a, b) .a ∈xN b ∈yNb ∈yN a ∈xNê‡ÒÒÚÓflÌË ÍÓÏÏÛÚËÓ‚‡ÌËflèÛÒÚ¸ (G, ⋅, e) – ÍÓ̘̇fl ̇·Â΂‡ „ÛÔÔ‡.
èÛÒÚ¸ Z(G) = {c ∈ G: x ⋅ c = c ⋅ x ‰Îflβ·Ó„Ó z ∈ G} – ˆÂÌÚ G. ɇ٠ÍÓÏÏÛÚËÓ‚‡ÌËfl „ÛÔÔ˚ G ÓÔ‰ÂÎflÂÚÒfl Í‡Í „‡ÙÒ ÏÌÓÊÂÒÚ‚ÓÏ ‚¯ËÌ G, ‚ ÍÓÚÓÓÏ ‡Á΢Ì˚ ˝ÎÂÏÂÌÚ˚ x, y ∈ G ÒÓ‰ËÌÂÌ˚·ÓÏ ‚ÒflÍËÈ ‡Á, ÍÓ„‰‡ ÓÌË ÍÓÏÏÛÚËÛ˛Ú, Ú.Â. x ⋅ y = y ⋅ x. é˜Â‚ˉÌÓ, ˜ÚÓ Î˛·˚‰‚‡ ‡Á΢Ì˚ı ˝ÎÂÏÂÌÚ‡ x, y ∈ G, ÍÓÚÓ˚ Ì ÍÓÏÏÛÚËÛ˛Ú, ‚ ‰‡ÌÌÓÏ „‡ÙÂÒÓ‰ËÌÂÌ˚ ÔÛÚÂÏ x, c, y, „‰Â Ò – β·ÓÈ ˝ÎÂÏÂÌÚ ËÁ Z(G) (̇ÔËÏÂ, Â). èÛÚ¸ x = x1,x2,..., x k = y ‚ „‡Ù ÍÓÏÏÛÚËÓ‚‡ÌËfl ̇Á˚‚‡ÂÚÒfl (x – y)N – ÔÛÚÂÏ, ÂÒÎË xi ∉ Z(G) ‰Îflβ·Ó„Ó i ∈ {1,…, k}. Ç ˝ÚÓÏ ÒÎÛ˜‡Â ˝ÎÂÏÂÌÚ˚ x, y ∈ G \Z(G) ̇Á˚‚‡˛ÚÒflN-ÒÓ‰ËÌÂÌÌ˚ÏË.ê‡ÒÒÚÓflÌËÂÏ ÍÓÏÏÛÚËÓ‚‡ÌËfl (ÒÏ.
[DeHu98]) d ̇Á˚‚‡ÂÚÒfl ‡Ò¯ËÂÌÌÓ ‡ÒÒÚÓflÌË ̇ G, Ú‡ÍÓ ˜ÚÓ ‚˚ÔÓÎÌfl˛ÚÒfl ÒÎÂ‰Û˛˘Ë ÛÒÎÓ‚Ëfl:1) d(x, x) = 0;2) d(x, x) = 1, ÂÒÎË x ≠ y Ë x ⋅ y = y ⋅ x;3) d(x, x) fl‚ÎflÂÚÒfl ÏËÌËχθÌÓÈ ‰ÎËÌÓÈ (x – y)N-ÔÛÚË ‰Îfl β·˚ı N-ÒÓ‰ËÌÂÌÌ˚ı˝ÎÂÏÂÌÚÓ‚ ı Ë y ∈ G\Z(G);4) d(x, x) = ∞, ÂÒÎË x, y ∈ G\Z(G) Ì ÒÓ‰ËÌÂÌ˚ ÌË͇ÍËÏ N-ÔÛÚÂÏ.åÓ‰ÛÎflÌÓ ‡ÒÒÚÓflÌËÂèÛÒÚ¸ (m, +, 0), m ≥ 2 – ÍÓ̘̇fl ˆËÍ΢ÂÒ͇fl „ÛÔÔ‡ Ë r ∈ , r ≥ 2.
åÓ‰ÛÎflÌ˚Èr-‚ÂÒ wr (x) ˝ÎÂÏÂÌÚ‡ x ∈ m = {0, 1,…, m} ÓÔ‰ÂÎflÂÚÒfl Í‡Í w r(x) = min{w r(x),w r(m – x)}, „‰Â wr(x) – ‡ËÙÏÂÚ˘ÂÒÍËÈ r-‚ÂÒ ˆÂÎÓ„Ó ˜ËÒ· ı. á̇˜ÂÌË w r(x) ÏÓÊÌÓÔÓÎÛ˜ËÚ¸ Í‡Í ˜ËÒÎÓ ÌÂÌÛ΂˚ı ÍÓ˝ÙÙˈËÂÌÚÓ‚ ‚ Ó·Ó·˘ÂÌÌÓÈ ÌÂÒÏÂÊÌÓÈ ÙÓÏÂx = en r n + … + e1r + e0 Ò ei = , | ei |< r, | ei + ei +1 |< r Ë | ei |<| ei +1 |, ÂÒÎË ei ei +1 < 0(ÒÏ. ÏÂÚË͇ ‡ËÙÏÂÚ˘ÂÒÍÓÈ r-ÌÓÏ˚, „Î. 12).åÓ‰ÛÎflÌÓ ‡ÒÒÚÓflÌË – ‡ÒÒÚÓflÌË ̇ m, ÓÔ‰ÂÎÂÌÌÓ ͇Íw r(x – y).åÓ‰ÛÎflÌÓ ‡ÒÒÚÓflÌË fl‚ÎflÂÚÒfl ÏÂÚËÍÓÈ ‰Îfl w r(m) = 1, w r(m) = 2 Ë ‰ÎflÌÂÍÓÚÓ˚ı ÓÒÓ·˚ı ÒÎÛ˜‡Â‚ Ò wr(m) = 3 ËÎË 4.
Ç ˜‡ÒÚÌÓÒÚË, ÓÌÓ fl‚ÎflÂÚÒfl ÏÂÚËÍÓȉÎfl m = r n ËÎË m = rn – 1; ÂÒÎË r = 2, ÚÓ ÓÌÓ ·Û‰ÂÚ ÏÂÚËÍÓÈ Ë ‰Îfl m = 2n + 1(ÒÏ., ̇ÔËÏÂ, [Ernv85]).ç‡Ë·ÓΠÔÓÔÛÎflÌÓÈ ÏÂÚËÍÓÈ Ì‡ m fl‚ÎflÂÚÒfl ÏÂÚË͇ ãË, ÓÔ‰ÂÎflÂχfl ͇Í|| x − y || Lee , „‰Â || x || Lee = min{x, m − x} – ÌÓχ ãË ˝ÎÂÏÂÌÚa x ∈ m.åÂÚË͇ G-ÌÓÏ˚ê‡ÒÒÏÓÚËÏ ÍÓ̘ÌÓ ÔÓΠFp n ‰Îfl ÔÓÒÚÓ„Ó ˜ËÒ· Ë Ì‡ÚۇθÌÓ„Ó ˜ËÒ· n.173É·‚‡ 10. ê‡ÒÒÚÓflÌËfl ‚ ‡Î„·ÂÑÎfl ‰‡ÌÌÓ„Ó ÍÓÏÔ‡ÍÚÌÓ„Ó ‚˚ÔÛÍÎÓ„Ó ˆÂÌڇθÌÓÒËÏÏÂÚ˘ÌÓ„Ó Ú· G ‚ ÓÔ‰ÂÎËÏ G-ÌÓÏÛ ˝ÎÂÏÂÌÚ‡ x ∈ Fp n Í‡Í || x ||G = inf{µ ≥ 0 : x ∈ p n + µG}.nåÂÚË͇ G-ÌÓÏ˚ ÂÒÚ¸ ÏÂÚË͇ ÌÓÏ˚ „ÛÔÔ˚ ̇ Fp n , ÓÔ‰ÂÎÂÌ̇fl ͇Í|| x ⋅ y −1 ||G .åÂÚË͇ ÌÓÏ˚ ÔÂÂÒÚ‡ÌÓ‚ÓÍÇÓÁ¸ÏÂÏ ÍÓ̘ÌÓ ÏÂÚ˘ÂÒÍÓ ÔÓÒÚ‡ÌÒÚ‚Ó (X, d).