Asymptotic profile of solutions for semilinear wave equations with structural damping

This paper is concerned with the initial value problem for semilinear wave equation with structural damping $u_{tt}+(-\Delta)^{\sigma}u_t -\Delta u =f(u)$,where$\sigma \in (0,\frac{1}{2})$and$f(u) \sim |u|^p$or$u |u|^{p-1}$with$p> 1 + {2}/(n - 2 \sigma)$. We first show the global existence for initial data small in some weighted Sobolev spaces on ${\mathcal{R}}^n$ ($n \ge 2$). Next, we show that the asymptotic profile of the solution above is given by a constant multiple of the fundamental solution of the corresponding parabolic equation, provided the initial data belong to weighted $L^1$ spaces.