Location of eigenvalues for the wave equation with dissipative boundary conditions (Q338607)

The location of the eigenvalues of the generator \(G\) of a semi-group \(V(t)=e^{tG}, t\geq 0,\) related to the wave equation on an unbounded domain in \(\mathbb{R}^d, d\geq 2\) with dissipative boundary condition is studied in the work. The purpose of the paper is to improve earlier results for the location of the eigenvalues. The main results are Theorem 1.1 and Theorem 1.2. Two cases (A) and (B) are considered and discussed.