The Log term in the Bergman and Szeg\H o kernels in strictly pseudoconvex domains in $\mathbb C^2$

Abstract

In this paper, we consider bounded strictly pseudoconvex domains $D\subset \mathbb C^2$ with smooth boundary $M=M^3:=\partial D$. If we consider the asymptotic expansion of the Bergman kernel on the diagonal $$ K_B\sim \frac{\phi_B}{\rho^{n+1}}+\psi_B\log\rho, $$ where $\rho>0$ is a Fefferman defining equation for $D$, then it is well known that the trace of the log term $b\psi_B:=(\psi_B)|_M$ on $M$ does not determine the CR geometry of $M$ locally; e.g., the vanishing of $b\psi_B$ on an open subset of $M$ does not imply that $M$ is locally spherical there. Nevertheless, the main result in this paper is that if $D\subset \mathbb C^2$ is assumed to have transverse symmetry, then the global vanishing of $b\psi_B$ on $M$ implies that $M$ is locally spherical. A similar result is proved for the Szeg\H o kernel.