Morse inequalities for Fourier components of Kohn-Rossi cohomology of CR covering manifolds with $S^1$-action

TL;DR

This paper establishes Morse inequalities for Fourier components of Kohn-Rossi cohomology on CR manifolds with $S^1$-action, extending previous results using heat kernel asymptotics and covering space techniques.

Contribution

It introduces a new approach using heat kernel asymptotics to derive Morse inequalities for Fourier components on CR covering manifolds with $S^1$-action, generalizing prior results.

Findings

Derived Morse inequalities for Fourier components of Kohn-Rossi cohomology.

Extended Morse inequalities to CR covering manifolds with $S^1$-action.

Connected heat kernel asymptotics with Morse inequalities in CR geometry.

Abstract

Let $X$ be a compact connected CR manifold of dimension $2n+1, n \geq 1$. Let $\widetilde{X}$ be a paracompact CR manifold with a transversal CR $S^1$-action, such that there is a discrete group $\Gamma$ acting freely on $\widetilde{X}$ having $X \, = \, \widetilde{X}/\Gamma$. Based on an asymptotic formula for the Fourier components of the heat kernel with respect to the $S^1$-action, we establish the Morse inequalities for Fourier components of reduced $L^2$-Kohn-Rossi cohomology with values in a rigid CR vector bundle over $\widetilde{X}$. As a corollary, we obtain the Morse inequalities for Fourier components of Kohn-Rossi cohomology on $X$ which were obtained by Hsiao-Li by using Szeg\"{o} kernel method.