Exponential decaying states for the wave equations are considered and some examples are given. Moreover, the spectral structure of the operator with coulomb type dissipation is investigated.
"Exponential Decay and Spectral Structure for Wave Equation with Some Dissipations." Tokyo J. Math. 28 (2) 463 - 470, December 2005. https://doi.org/10.3836/tjm/1244208201