Lower bounds for resonance counting functions for obstacle scattering in even dimensions

T. J. Christiansen

Published 2014-09-26Version 1

In even dimensional Euclidean scattering, the resonances lie on the logarithmic cover of the complex plane. This paper studies resonances for obstacle scattering in ${\mathbb R}^d$ with Dirchlet or admissable Robin boundary conditions, when $d$ is even. Set $n_m(r)$ to be the number of resonances with norm at most $r$ and argument between $m\pi$ and $(m+1)\pi$. Then $\lim\sup _{r\rightarrow \infty}\frac{\log n_m(r)}{\log r}=d$ if $m\in {\mathbb Z}\setminus \{ 0\}$.