Cohomological varieties associated to vertex operator algebras

TL;DR

This paper introduces the cohomological variety of a vertex algebra, exploring its properties and examples, revealing that it can be large even when the associated variety is a point, thus offering new invariants for vertex algebras.

Contribution

It defines and studies the cohomological variety of vertex algebras, providing initial properties, examples, and comparisons with associated varieties, expanding the understanding of vertex algebra invariants.

Findings

Cohomological varieties can be large even for simple associated varieties.

Constructed examples for rational affine vertex operator algebras and Virasoro VOAs.

Cohomological support varieties can differ significantly from associated varieties.

Abstract

Given a vertex operator algebra V , one can attach a graded Poisson algebra called the C2-algebra R(V). The associate Poisson scheme provides an important invariant for V and has been studied by Arakawa as the associated variety. In this article, we define and examine the cohomological variety of a vertex algebra, a notion cohomologically dual to that of the associated variety, which measures the smoothness of the associated scheme at the vertex point. We study its basic properties and then construct a closed subvariety of the cohomological variety for rational affine vertex operator algebras constructed from finite dimensional simple Lie algebras. We also determine the cohomological varieties of the simple Virasoro vertex operator algebras. These examples indicate that, although the associated variety for a rational C2-cofinite vertex operator algebra is always a simple point, the cohomological variety can have as large a dimension as possible. In this paper, we study R(V) as a commutative algebra only and do not use the property of its Poisson structure, which is expected to provide more refined invariants. The goal of this work is to study the cohomological supports of modules for vertex algebras as the cohomological support varieties for finite groups and restricted Lie algebras.