Almost free modules, perfect decomposition and Enochs's conjecture

Given a module $X$ and a regular cardinal $\kappa$ we study various notions of $(\kappa ,\mathrm{A}\mathrm{d}\mathrm{d}(X))$-freeness and $(\kappa ,\mathrm{A}\mathrm{d}\mathrm{d}(X))$-separability. Bearing on appropriate set-theoretic assumptions, we construct a non-trivial ${\kappa }^{+}$-generated, $({\kappa }^{+},\mathrm{A}\mathrm{d}\mathrm{d}(X))$-free and $({\kappa }^{+},\mathrm{A}\mathrm{d}\mathrm{d}(X))$-separable module. Our construction allows $\kappa$ to be singular thus extending \cite[Theorem~4.7]{CortesGuilTorrecillas}. Bearing on similar set-theoretic assumptions, we characterize when every module $X$ has a perfect decomposition. As a subproduct we show that Enoch’s conjecture for classes $\mathrm{A}\mathrm{d}\mathrm{d}(X)$ is consistent with ZFC – a fact first proved by Šaroch \cite{Saroch}.