P-stable group

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Template:Short description Template:Distinguish Template:Lowercase In finite group theory, a p-stable group for an odd prime p is a finite group satisfying a technical condition introduced by Template:Harvs in order to extend Thompson's uniqueness results in the odd order theorem to groups with dihedral Sylow 2-subgroups.

Definitions

There are several equivalent definitions of a p-stable group.

First definition.

We give definition of a p-stable group in two parts. The definition used here comes from Template:Harv.

1. Let p be an odd prime and G be a finite group with a nontrivial p-core Op(G). Then G is p-stable if it satisfies the following condition: Let P be an arbitrary p-subgroup of G such that Op(G) is a normal subgroup of G. Suppose that xNG(P) and x¯ is the coset of CG(P) containing x. If [P,x,x]=1, then xOn(NG(P)/CG(P)).

Now, define p(G) as the set of all p-subgroups of G maximal with respect to the property that Op(M)=1.

2. Let G be a finite group and p an odd prime. Then G is called p-stable if every element of p(G) is p-stable by definition 1.

Second definition.

Let p be an odd prime and H a finite group. Then H is p-stable if F*(H)=Op(H) and, whenever P is a normal p-subgroup of H and gH with [P,g,g]=1, then gCH(P)Op(H/CH(P)).

Properties

If p is an odd prime and G is a finite group such that SL2(p) is not involved in G, then G is p-stable. If furthermore G contains a normal p-subgroup P such that CG(P)P, then Z(J0(S)) is a characteristic subgroup of G, where J0(S) is the subgroup introduced by John Thompson in Template:Harv.

See also

References