Exact structures for operator modules

Quasi-Exact Sequence and Finitely Presented Modules

The notion of quasi-exact sequence of modules was introduced by B. Davvaz and coauthors in 1999 as a generalization of the notion of exact sequence. In this paper we investigate further this notion. In particular, some interesting results concerning this concept and torsion functor are given.

Induced modules for vertex operator algebras

For a vertex operator algebra V and a vertex operator subalgebra V ′ which is invariant under an automorphism g of V of finite order, we introduce a g-twisted induction functor from the category of g-twisted V ′-modules to the category of g-twisted V -modules. This functor satisfies the Frobenius reciprocity and transitivity. The results are illustrated with V ′ being the g-invariants in simple...

Twisted modules for vertex operator algebras

In this contribution, I explain the general principles of twisted modules for vertex operator algebras in its powerful formulation using formal series, and derive new general relations satisfied by twisted and non-twisted vertex operators. I prove new “equivalence” and “construction” theorems, identifying a very restricted set of sufficient conditions in order to have a twisted module for a ver...

Exact Operator Spaces

Splitting of Short Exact Sequences for Modules

(1.1) 0 −→ N f −−→M g −−→ P −→ 0 which is exact at N , M , and P . That means f is injective, g is surjective, and im f = ker g. Example 1.1. For an R-module M and submodule N , there is a short exact sequence 0 // N // M // M/N // 0, where the map N →M is the inclusion and the map M →M/N is reduction modulo N . Example 1.2. For R-modules N and P , the direct sum N ⊕ P fits into the short exact...