Existence and upper semicontinuity of pullback attractors for Kirchhoff wave equations in time-dependent spaces

In this paper, we shall investigate the existence and upper semicontinuity of pullback attractors for non-autonomous Kirchhoff wave equations with a strong damping in the time-dependent space $X_t$. After deriving the existence and uniqueness of solutions by the Faedo-Galerkin approximation method, we establish the existence of pullback attractors. Later on, we prove the upper semicontinuity of pullback attractors between the Kirchhoff-type wave equations with $\delta \geq 0$ and the conventional wave equations with $\delta=0$ by a series of complex energy estimates.