“…Alabau–Boussouira in [
2] proved sharp or quasi‐optimal upper energy decay rates for a class of nonlinear feedbacks ranging from very weak nonlinear dissipation to polynomial or polynomial‐logarithmic decaying feedbacks at the origin. For the case of damped semilinear wave equations with a nonlinearity
, as considered in [
3], with
, we reference [
3] and the references presented therein (in particular, [
22, 28, 45], and [51]). The case
has been investigated by Dehman, Lebeau, and Zuazua in [
24] and Joly and Laurent in [
32].…”