Deconstructible classes of modules and stability

Abstract

We show that every deconstructible class of modules with all embeddings, all pure embedding and all RD-embeddings is stable. The argument is presented in the context of abstract classes of modules without amalgamation and the key idea is to construct a stable-like independence relation. In particular, the following classes of modules with all embeddings, all pure embedding and all RD-embeddings are shown to be stable: all free and torsion-free modules over any ring, and for each $n\ge 0$, the classes of all modules of projective and flat dimension $\le n$ over any ring, and the class of all modules of injective dimension $\le n$ over any right noetherian ring.

21 pages