“…On compact domains, dispersion, scattering and time-decay mechanisms are not available, and there are no results of global existence, nor of finite time blowup, for initial data (α, β) of Sobolev, or C ∞ , or Gevrey regularity. The local wellposedness in the Sobolev class H ) and other open questions, we refer to Lions [37] and the surveys of Arosio [2], Spagnolo [49], and Matsuyama and Ruzhansky [41].…”