Multielement Order Separability in Free Products of Groups

Subgroup Separability in Residually Free Groups

We prove that the finitely presentable subgroups of residually free groups are separable and that the subgroups of type FP∞ are virtual retracts. We describe a uniform solution to the membership problem for finitely presentable subgroups of residually free groups.

Automata generating free products of groups of order 2

We construct a family of automata with n states, n ≥ 4, acting on a rooted binary tree that generate the free products of cyclic groups of order 2.

On the Cyclic Subgroup Separability of Free Products of Two Groups with Amalgamated Subgroup

Let G be a free product of two groups with amalgamated subgroup, π be either the set of all prime numbers or the one-element set {p} for some prime number p. Denote by Σ the family of all cyclic subgroups of group G, which are separable in the class of all finite π-groups. Obviously, cyclic subgroups of the free factors, which aren’t separable in these factors by the family of all normal subgro...

Profinite Topologies in Free Products of Groups

Let H be an abstract group and let C be a variety of finite groups (i.e., a class of finite groups closed under taking subgroups, quotients and finite direct products); for example the variety of all finite p-groups, for a fixed prime p. Consider the smallest topology on H such that all the homomorphism H −→ C from H to any group C ∈ C (endowed with the discrete topology) is continuous. We refe...

Free Products of Absolute Galois Groups *