Gradient higher integrability of bounded solutions to parabolic double-phase systems

Abstract: We prove that bounded solutions to degenerate parabolic double-phase problem modelled upon [u_t-\dv(|\na u|^{p-2}\na u+a(x,t)|\na u|^{q-2}\na u)=-\dv(|F|^{p-2}F+a(x,t)|F|^{q-2}F)\,, ] where a nonnegative weight $a$ is $α$-Hölder continuous in space and $\tfrac α2$-Hölder continuous in time, have locally higher integrable gradients for the sharp range of exponents $p<q\le p+α$.