Lower bounds on the number of scattering poles. II (Q1332194)

In continuation of their paper [Commun. Partial Differ. Equ. 18, No. 5-6, 847-857 (1993; Zbl 0784.35070)] (where several examples were treated), here the authors obtain a very general lower bound on the number of scattering poles, for a wide class of abstract compactly supported perturbations of the Laplacian in \(\mathbb{R}^ n\) (\(n\) odd). The proof is based on the exploitation of the singularities of the wave trace at zero.