Embeddings into P(ℕ)/fin and extension of automorphisms

Abstract

Given a Boolean algebra double-struk B sign and an embedding e: double-struk B sign → P(ℕ)/fin we consider the possibility of extending each or some automorphism of double-struk B sign to the whole P(ℕ)/fin. Among other things, we show, assuming CH, that for a wide class of Boolean algebras there are embeddings for which no non-trivial automorphism can be extended.