Intersections of Sylow subgroups in finite groups  pp. 191-197

By V. D. Mazurov and V. I. Zenkov

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For every finite group G and every prime p, ip(G) ≤ 3, where ip(G) denotes the smallest number of Sylow p-subgroups of G whose intersection coincides with the intersection of all Sylow p-subgroups of G. For all simple groups (G, ip(G) ≤ 2.


Let G be a finite group and p be a prime. Denote by Op(G) the intersection of all Sylow p-subgroups of G and by ip(G) the smallest number i such that Op(G) is equal to the intersection of i Sylow p-subgroups. Obviously, ip(G) = 1 if and only if G has an unique Sylow p-subgroup. J. Brodkey [2] proved that ip(G) ≤ 2 if a Sylow p-subgroup of G is abelian and N. Ito [5] found sufficient conditions for a finite solvable group to satisfy ip(G) ≤ 2.

This paper discuss some recent results in this direction. The main theorems are the following:

Theorem 1 [10] If G is a simple non-abelian group then ip(G) = 2 for every prime p dividing the order of G.

Theorem 2 [9] For every finite group G and every prime p, ip(G) ≤ 3.

Section 2 contains a sketch of a proof of Theorem 1 which uses the Classification of Finite Simple Groups. Section 3 presents results about intersections of Sylow subgroups in arbitrary finite groups. We use the notation of the atlas [3].

Preliminary results

The following elementary results, the first of which is trivial, give a base for induction arguments in the proof of the main theorems of this paper.