Spectral action for scalar perturbations of Dirac operators

Abstract

We investigate the leading terms of the spectral action for odd-dimensional Riemannian spin manifolds with the Dirac operator perturbed by a scalar function. We calculate first two Gilkey-de Witt coefficients and make explicit calculations for the case of $n$-spheres with a completely symmetric Dirac. In the special case of dimension 3, when such perturbation corresponds to the completely antisymmetric torsion we carry out the noncommutative calculation following Chamseddine and Connes and study the case of $SU_q(2)$.