Intermediate categories for proper abelian subcategories

Abstract

Let \(\mathscr{A}\) be an extension closed proper abelian subcategory of a triangulated category \(\mathscr{T}\), with no negative 1 and 2 extensions. From this, two functors from \(\Sigma\mathscr{A}\ast\mathscr{A}\) to \(\mathscr{A}\) can be constructed giving a snake lemma mirroring that of homology without needing a t-structure. We generalize the concept of intermediate categories, which originates from a paper by Enomoto and Saito, to the setting of proper abelian subcategories and show that under certain assumptions this collection is in bijection with torsion-free classes in \(\mathscr{A}\).