De Rham Cohomology and Hodge decomposition for Quantum Groups

Abstract

Let G=G(t,z) be one of the N^2-dimensional bicovariant first order differential calculi for the quantum groups GL_q(N), SL_q(N), O_q(N), or Sp_q(N), where q is a transcendental complex number and z is a regular parameter. It is shown that the de Rham cohomology of Woronowicz' external algebra G^ coincides with the de Rham cohomologies of its left-coinvariant, its right-coinvariant and its (twosided) coinvariant subcomplexes. In the cases GL_q(N) and SL_q(N) the cohomology ring is isomorphic to the coinvariant external algebra G^_{inv} and to the vector space of harmonic forms. We prove a Hodge decomposition theorem in these cases. The main technical tool is the spectral decomposition of the quantum Laplace-Beltrami operator. Keywords: quantum groups, bicovariant differential calculi, de Rham cohomology, Laplace-Beltrami operator, Hodge theory