Vek zhivi vek uchis', ili chislo 6
Nov. 29th, 2002 12:54 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
posicOkazyvaetsya, gruppa perestanovok 6-elementnogo mnozhestva imeet vneshnij avtomorfizm. Ya prochital ob etom zdes':
Consider 6 things, e.g. the numerals 123456. There are 15 non-ordered pairs of them. (Call these "duads.") Also there are 15 ways to divide the original set into three duads, e.g. {(12}{34}{56}}. Call these "synthemes." Five synthemes can be chosen so as to contain each duad exactly once; and there turn out to be exactly six ways to make this choice. You can label these six sets ABCDEF. Then a permutation of 123456 induces a permutation of ABCDEF. A two-cycle such as (12) induces a product of three disjoint two-cycles such as (AB)(CD)(EF), so the map from one permutation to the other cannot be an inner automorphism.
Dovol'no zamyslovataya vse-taki konstrukciya, sopostavlyayuschaya 6-elementnomu mnozhestvu drugoe 6-elementnoe mnozhestvo. Ya esche znayu na etu temu gorazdo bolee prostuyu konstrukciyu, sopostavlyayuschuyu 4-elementnomu mnozhestvu 3-elementnoe mnozhestvo.
Ostal'nye gruppy Sn (pri n ne ravnom 6) vneshnih avtomorfizmov ne imeyut, chto netrudno dokazat', rassmotrev klass sopryazhennosti, sostoyaschij iz transpozicij, i ego obraz pri nashem avtomorfizme. Podrobnosti imeyutsya zdes' (fajl v formate postscript).
Consider 6 things, e.g. the numerals 123456. There are 15 non-ordered pairs of them. (Call these "duads.") Also there are 15 ways to divide the original set into three duads, e.g. {(12}{34}{56}}. Call these "synthemes." Five synthemes can be chosen so as to contain each duad exactly once; and there turn out to be exactly six ways to make this choice. You can label these six sets ABCDEF. Then a permutation of 123456 induces a permutation of ABCDEF. A two-cycle such as (12) induces a product of three disjoint two-cycles such as (AB)(CD)(EF), so the map from one permutation to the other cannot be an inner automorphism.
Dovol'no zamyslovataya vse-taki konstrukciya, sopostavlyayuschaya 6-elementnomu mnozhestvu drugoe 6-elementnoe mnozhestvo. Ya esche znayu na etu temu gorazdo bolee prostuyu konstrukciyu, sopostavlyayuschuyu 4-elementnomu mnozhestvu 3-elementnoe mnozhestvo.
Ostal'nye gruppy Sn (pri n ne ravnom 6) vneshnih avtomorfizmov ne imeyut, chto netrudno dokazat', rassmotrev klass sopryazhennosti, sostoyaschij iz transpozicij, i ego obraz pri nashem avtomorfizme. Podrobnosti imeyutsya zdes' (fajl v formate postscript).
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Re: Через 3 года (А_6≤PSL_3(4))
Date: 2005-10-10 06:11 pm (UTC)Да, это было бы очень хорошо. Это требует некоторой работы (поскольку было бы правильно не ссылаться на какие-то давние разговоры, а изложить цельно) --- но того стоит. Если Вы какой-то цельный кусок этого изложите, то будет здорово, и я тоже могу чем-то поучаствовать.