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arXiv math/0606216math.LOmath.GR
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无中心群的自同构塔(大多数)没有选择

The automorphism tower of a centerless group (mostly) without choice

Itay Kaplan, Saharon Shelah

摘要:

对于一个无中心群G,我们可以定义它的自同构塔。我们定义G^{alpha}:G^0=G,G^{alpha +1}=Aut(G^alpha),对于极限序数G^delta= bigcup_{alpha < delta} G^alpha。设tau_G为序列稳定时的序数。托马斯著名的定理说τ_G<2^{ |G| })^{+}和更多。如果我们考虑托马斯的证明太集理论,我们在这里有一个较短的证明与小集合论。然而,从理论上讲,我们得到了一个平行定理,没有选择公理。我们给G^alpha中的每一个元素,G的自同构塔的第alpha个成员,一个在G上唯一的无量词类型(它是来自G* 的一组词< x>)。通过定义“(G,A)是一个特殊的对”来推广这种情况。

英文摘要:

For a centerless group G, we can define its automorphism tower. We define G^{alpha} : G^0=G, G^{alpha +1}=Aut(G^alpha) and for limit ordinals G^delta=bigcup_{alpha < delta}G^alpha . Let tau_G be the ordinal when the sequence stabilizes. Thomas' celebrated theorem says tau_G<2^{|G|})^{+} and more. If we consider Thomas' proof too set theoretical, we have here a shorter proof with little set theory. However, set theoretically we get a parallel theorem without the axiom of choice. We attach to every element in G^alpha, the alpha-th member of the automorphism tower of G, a unique quantifier free type over G (whish is a set of words from G*< x>). This situation is generalized by defining ``(G,A) is a special pair''.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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