A Bass–Serre theoretic proof of a theorem of Romanovskii and Burns

Abstract

A well-known theorem of Romanovskii and Burns states that a free product of subgroup separable groups is itself subgroup separable. We provide a proof using the language of immersions and coverings of graphs of groups, due to Bass.

KEYWORD:

• Bass–Serre theory
• subgroup separability

2020MATHEMATICS SUBJECT CLASSIFICATION:

• 20E06