[Math] The intersection of two Sylow p-subgroups has the same order

abstract-algebrafinite-groupsgroup-theorysylow-theory

Let $G$ be a finite group and assume it has more than one Sylow $p$-subgroup.

It is known that order of intersection of two Sylow p-subgroups may change depending on the pairs of Sylow p-subgroups.

I wonder whether there is a condition which guarantees that intersection of any two Sylow $p$-subgroups has the same order.

Thanks for your help.

Best Answer

I can prove the following, which provides a criterion to start with.

Theorem Let $G$ be a finite group. Then the following are equivalent.

$(a)$ For all $S,T \in Syl_p(G)$ with $S \neq T$, $S \cap T=1$.
$(b)$ For each non-trivial $p$-subgroup $P$ of $G$, $N_G(P)$ has a unique Sylow $p$-subgroup.
$(c)$ For each non-trivial $p$-subgroup $P$ of $G$, $P$ is contained in a unique Sylow $p$-subgroup of $G$.

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