On the interplay between $(p,q)$-growth and $x$-dependence of the energy integrand: a limit case

Abstract

We establish the local Lipschitz regularity of the local minimizers of non autonomous integral funtionals of the form \[ \int_\Omega F(x, Dz)\,dx, \] where $\Omega$ is a bounded open set of $\mathbb{R}^n$, $n \ge 2$. The energy density $F(x,\xi)$ satisfies $(p,q)-$growth conditions with respect to the gradient variable and belongs to the Sobolev class $W^{1,\phi}$, with $\phi(t)=t^r\log^\alpha(e+t),$ $r\ge n$, $\alpha\ge 0$, as a function of the $x$ variable, under the condition $$ 1\le\frac{q}{p} \le 1 + \frac{1}{n} - \frac{1}{r}. $$ We present a unified approach that covers the limit case $$ \frac{q}{p} = 1 + \frac{1}{n} - \frac{1}{r} $$ and retrieves the results in \cite{EMM16} and in \cite{CGHPdN20}.