Modular Algorithm for Computing Cohomology: Lie Superalgebra of Special Vector Fields on (2|2)-dimensional Odd-Symplectic Superspace

Abstract

We describe an essential improvement of our recent algorithm for computing cohomology of Lie (super)algebra based on partition of the whole cochain complex into minimal subcomplexes. We replace the arithmetic of rational numbers or integers by a much cheaper arithmetic of a modular field and use the inequality between the dimensions of cohomology H over any modular field F_p = Z/pZ and over Q: dim H(F_p) >= dim H(Q). With this inequality we can, by computing over arbitrary F_p, quickly find the (usually, rare) subcomplexes for which dim H(F_p) > 0 and then carry out the full computation over Q within these subcomplexes. We also present the results of application of the corresponding C program to the Lie superalgebra of special vector fields preserving an "odd-symplectic" structure on the (2|2)-dimensional supermanifold. For this algebra, we found some new basis elements of the cohomology in the trivial module.