On fractional semilinear wave equations in non-cylindrical domains
Mauro Bonafini, Van Phu Cuong Le, Riccardo Molinarolo
TL;DR
This work studies the fractional semilinear wave equation $\ddot{u}+(-\Delta)^s u+\nabla W(u)=f$ in a time-dependent, non-cylindrical domain $\mathcal{O}$ with exterior Dirichlet conditions and evolving spatial domains $\{\Omega_t\}$. It develops two existence proofs under mild regularity and monotonicity assumptions: a constructive time-discretization scheme and a Lions-type penalty method, both accommodating nonlocal operators and vector-valued maps. The main results guarantee the existence of weak solutions and an energy inequality, with the energy $E(u(t))$ decreasing suitably under forcing. This extends prior cylindrical-domain results to non-cylindrical, time-evolving domains and provides robust variational methods for fractional hyperbolic problems.
Abstract
In this paper, we investigate a class of semilinear wave equations in non-cylindrical time-dependent domains, subject to exterior homogeneous Dirichlet conditions. Under mild regularity and monotonicity assumptions on the evolving spatial domains, we establish existence of weak solutions by two different methods: a constructive time-discretization scheme and a penalty approach. The analysis applies to nonlocal fractional Laplacians and potentials with Lipschitz continuous gradient, and to vector-valued maps.
