Wave equations with a damping term degenerating near low and high frequency regions

We consider wave equations with a nonlocal polynomial type of damping depending on a small parameter \(\theta \in (0,1)\). This research is a trial to consider a new type of dissipation mechanisms produced by a bounded linear operator for wave equations. These researches were initiated in a series of our previous works with various dissipations modeled by a logarithmic function published in (Charão et al. in Math Methods Appl Sci 44:14003-14024, 2021; Charão and Ikehata in Angew Math Phys 71:26, 2020; Piske et al. in J Diff Eqns 311:188-228, 2022). The model of dissipation considered in this work is probably the first defined by more than one sentence and it opens field to consider other more general. We obtain an asymptotic profile and optimal estimates in time of solutions as \(t \rightarrow \infty \) in \(L^{2}\)-sense, particularly, to the case \(0<\theta <1/ 2\).