Γ-convergence for power-law functionals with variable exponents

We study the $\Gamma$-convergence of the functionals $F_n(u):= || f(\cdot,u(\cdot),Du(\cdot))||_{p_n(\cdot)}$ and $\F_n(u):=\displaystyle \int_{\Omega} \frac{1}{p_n(x)} f^{p_n(x)}(x,u(x),Du(x))dx$ defined on $X\in \{L^1(\Omega,\R^d), L^\infty(\Omega,\R^d), C(\Omega,\R^d)\}$ (endowed with their usual norms) with effective domain the Sobolev space $W^{1,p_n(\cdot)}(\Omega, \mathbb{R}^d )$. Here $\Omega\subseteq \R^N$ is a bounded open set, $N,d \ge 1$ and the measurable functions $p_n: \Omega \rightarrow [1, + \infty) $ satisfy the conditions $\displaystyle{\supess_{\Omega} p_n \le \, \beta \, \infess_{ \Omega} p_n < +\infty}$ for a fixed constant $\beta > 1$ and $\displaystyle{\infess_{\Omega} p_n \rightarrow + \infty}$ as $n \rightarrow + \infty$. We show that when $f(x,u,\cdot)$ is level convex and lower semicontinuous and it satisfies a uniform growth condition from below, then, as $n\to \infty$, the sequences $(F_n)_n$ $\Gamma$-converges in $X$ to the functional $F$ represented as $F(u)= || f(\cdot,u(\cdot),Du(\cdot))||_{\infty}$ on the effective domain $W^{1,\infty}(\Omega, \mathbb{R}^d )$. Moreover we show that the $\Gamma$-$\lim_n \F_n$ is given by the functional $ \F(u):=\left\{\begin {array}{lll} \!\!\!\!\!\! & \displaystyle 0 & \hbox{if } || f(\cdot,u(\cdot),Du(\cdot)) ||_{\infty}\leq 1,\\ \!\!\!\!\!\! & +\infty & \hbox{otherwise in } X.\\ \end{array}\right. $