$Γ$-convergence for power-law functionals with variable exponents

We study the $Γ$-convergence of the functionals $F_n(u):= || f(\cdot,u(\cdot),Du(\cdot))||_{p_n(\cdot)}$ and $\mathcal{F}_n(u):= \int_Ω \frac{1}{p_n(x)} f^{p_n(x)}(x,u(x),Du(x))dx$ defined on $X\in \{L^1(Ω,\mathbb{R}^d), L^\infty(Ω,\mathbb{R}^d), C(Ω,\mathbb{R}^d)\}$ (endowed with their usual norms) with effective domain the Sobolev space $W^{1,p_n(\cdot)}(Ω, \mathbb{R}^d )$. Here $Ω\subseteq \mathbb{R}^N$ is a bounded open set, $N,d \ge 1$ and the measurable functions $p_n: \overlineΩ \rightarrow (1, + \infty)$ satisfy the conditions ${\mathop{\rm ess\: sup }}_{\ \overline Ω} p_n \le \, β\, {\mathop{\rm ess\: inf }}_{\ \overline Ω} p_n$ for a fixed constant $β> 1$ and ${\mathop{\rm ess\: inf }}_{\ \overline Ω} p_n \rightarrow + \infty$ 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 $(F_n)_n$ $Γ$-converges in $X$ to the functional $F$ represented as $F(u)= || f(\cdot,u(\cdot),Du(\cdot))||_{\infty}$ on the effective domain $W^{1,\infty}(Ω, \mathbb{R}^d )$. Moreover we show that the $Γ$-$\lim_n \mathcal F_n$ is given by the functional $\mathcal{F}(u):=\left\{\begin {array}{lll} \!\!\!\!\!\! & 0 & \hbox{if } || f(\cdot,u(\cdot),Du(\cdot)) ||_{\infty}\leq 1,\\ \!\!\!\!\!\! & +\infty & \hbox{otherwise in } X.\\ \end{array}\right.$

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