“…In the AdS spacetime, one finds that when it is linearly perturbed with reflective boundary conditions, also called box boundary conditions, it oscillates normally, rather than quasinormally, as there are no losses of the field to infinity. For the AdS spacetime, the normal modes of scalar [8], electromagnetic and gravitational perturbations [9], and massive Proca perturbations [10,11] have been studied.…”