Bohr sets in sumsets II: countable abelian groups

John T. Griesmer, Anh N. Le, Thái Hoàng Lê

We prove three results concerning the existence of Bohr sets in threefold sumsets. More precisely, letting $G$ be a countable discrete abelian group and ${\varphi }_1,{\varphi }_2,{\varphi }_3:G\to G$ be…