Eigenvalue Estimates of the ${\mathrm{spin}}^c$ Dirac Operator and Harmonic Forms on Kähler-Einstein Manifolds

Abstract

We establish a lower bound for the eigenvalues of the Dirac operator defined on a compact Kähler-Einstein manifold of positive scalar curvature and endowed with particular ${\mathrm{spin}}^c$ structures. The limiting case is characterized by the existence of Kählerian Killing ${\mathrm{spin}}^c$ spinors in a certain subbundle of the spinor bundle. Moreover, we show that the Clifford multiplication between an effective harmonic form and a Kählerian Killing ${\mathrm{spin}}^c$ spinor field vanishes. This extends to the ${\mathrm{spin}}^c$ case the result of A. Moroianu stating that, on a compact Kähler-Einstein manifold of complex dimension $4\ell +3$ carrying a complex contact structure, the Clifford multiplication between an effective harmonic form and a Kählerian Killing spinor is zero.