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In [[mathematics]], especially in the area of [[abstract algebra|algebra]] known as [[group theory]], the '''Prüfer rank''' of a [[pro-p group]] measures the size of a group in terms of the ranks of its [[elementary abelian group|elementary abelian]] [[section (group theory)|section]]s. The rank is well behaved and helps to define analytic pro-p-groups. The term is named after [[Heinz Prüfer]]. | |||
== Definition == | |||
The Prüfer rank of [[pro-p-group]] <math>G</math> is | |||
::<math>\sup\{d(H)|H\leq G\}</math> | |||
where <math>d(H)</math> is the [[rank of an abelian group|rank]] of the abelian group | |||
:<math>H/\Phi(H)</math>, | |||
where <math>\Phi(H)</math> is the [[Frattini subgroup]] of <math>H</math>. | |||
As the Frattini subgroup of <math>H</math> can be thought of as the group of non-generating elements of <math>H</math>, it can be seen that <math>d(H)</math> will be equal to the ''size of any minimal generating set'' of <math>H</math>. | |||
== Properties == | |||
Those [[profinite group]]s with finite Prüfer rank are more amenable to analysis. | |||
Specifically in the case of finitely generated [[pro-p group]]s, having finite Prüfer rank is equivalent to having an [[open set|open]] [[normal subgroup]] that is [[powerful p-groups|powerful]]. In turn these are precisely the class of [[pro-p group]]s that are [[p-adic number|p-adic]] analytic - that is groups that can be imbued with a | |||
[[p-adic number|p-adic]] [[manifold]] structure. | |||
== References == | |||
{{unref|date=March 2008}} | |||
{{DEFAULTSORT:Prufer Rank}} | |||
[[Category:Infinite group theory]] |
Revision as of 14:46, 17 November 2013
In mathematics, especially in the area of algebra known as group theory, the Prüfer rank of a pro-p group measures the size of a group in terms of the ranks of its elementary abelian sections. The rank is well behaved and helps to define analytic pro-p-groups. The term is named after Heinz Prüfer.
Definition
The Prüfer rank of pro-p-group is
where is the rank of the abelian group
where is the Frattini subgroup of .
As the Frattini subgroup of can be thought of as the group of non-generating elements of , it can be seen that will be equal to the size of any minimal generating set of .
Properties
Those profinite groups with finite Prüfer rank are more amenable to analysis.
Specifically in the case of finitely generated pro-p groups, having finite Prüfer rank is equivalent to having an open normal subgroup that is powerful. In turn these are precisely the class of pro-p groups that are p-adic analytic - that is groups that can be imbued with a p-adic manifold structure.
References
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