Higher differentiability of solutions for a class of obstacle problems with variable exponents

In this paper we prove a higher differentiability result for the solutions to a class of obstacle problems in the form \begin{equation*} \label{obst-def0} \min\left\{\int_\Omega F(x,Dw) dx : w\in \mathcal{K}_{\psi}(\Omega)\right\} \end{equation*} where $\psi\in W^{1,p(x)}(\Omega)$ is a fixed function called obstacle and \mathcal{K}_{\psi}=\{w \in W^{1,p(x)}_{0}(\Omega)+u_0: w \ge \psi \,\, \textnormal{a.e. in \Omega}\} is the class of the admissible functions, for a suitable boundary value $u_0$. We deal with a convex integrand $F$ which satisfies the $p(x)$-growth conditions \begin{equation*}\label{growth}|\xi|^{p(x)}\le F(x,\xi)\le C(1+|\xi|^{p(x)}),\quad p(x)>1 \end{equation*}