Cohomology of Heisenberg Lie Superalgebras

TL;DR

This paper computes the cohomology and Betti numbers of Heisenberg Lie superalgebras, revealing their algebraic structures in characteristic zero and positive characteristic, using spectral sequences and divided power cohomology.

Contribution

It provides a complete determination of cohomology and Betti numbers for these superalgebras in characteristic zero and explores their structures in positive characteristic.

Findings

Betti numbers and cohomology structures are fully determined in characteristic zero.

Associative superalgebra structures for divided power cohomology are identified in characteristic p>3.

Partial results and computations are provided for low-dimensional cases in positive characteristic.

Abstract

Suppose the ground field to be algebraically closed and of characteristic different from $2$ and $3$. All Heisenberg Lie superalgebras consist of two super versions of the Heisenberg Lie algebras, $\frak{h}_{2m,n}$ and $\frak{ba}_n$ with $m$ a nonnegative integer and $n$ a positive integer. The space of a "classical" Heisenberg Lie superalgebra $\frak{h}_{2m,n}$ is the direct sum of a superspace with a non-degenerate anti-supersymmetric even bilinear form and a one-dimensional space of values of this form constituting the even center. The other super analog of the Heisenberg Lie algebra, $\frak{ba}_n$, is constructed by means of a non-degenerate anti-supersymmetric odd bilinear form with values in the one-dimensional odd center. In this paper, we study the cohomology of $\frak{h}_{2m,n}$ and $\frak{ba}_n$ with coefficients in the trivial module by using the Hochschild-Serre spectral sequences relative to a suitable ideal. In characteristic zero case, for any Heisenberg Lie superalgebra, we determine completely the Betti numbers and associative superalgebra structure for their cohomology. In characteristic $p>3$ case, we determine the associative superalgebra structures for the divided power cohomology of $\frak{ba}_n$ and we also make an attempt to determine the cohomology of $\frak{h}_{2m,n}$ by computing it in a low-dimensional case.