The aim of this paper is to show that every infinite Boolean algebra which admits a countable minimally acting group contains a dense projective subalgebra.
MSC:54B35, 54A05, 52A01, 54D30
Regular and relatively complete subalgebrasAll Boolean algebras considered here are assumed to be infinite. Boolean algebraic notions, excluding symbols for Boolean operations, follow the Koppelberg's monograph [9]. In particular, if (B ∧ ∨ − 0 1) is a Boolean algebra, then B + = B \ {0} denotes the set of all non-zero elements of B. A set A ⊆ B is a subalgebra of the Boolean algebra B, A ≤ B for short, if 1 0 ∈ A and A is closed under Boolean operations or, equivalently, − ∈ A for all ∈ A. We shall write A ∼ = B whenever A and B are isomorphic Boolean algebras. A non-empty set X ⊆ B + is called a partition of B whenever ∧ = 0 for distinct ∈ X and B X = 1 *