Existence of infinitely many solutions for double phase problem with sign-changing potential

In this paper, we investigate the existence of infinitely many solutions for the following double phase problem $$\begin{aligned} \left\{ \begin{array}{l@{\quad }l} -\mathrm{div}(|\nabla u|^{p-2}\nabla u+a(x)|\nabla u|^{q-2}\nabla u)= f(x,u),&{}\hbox {in }\;\Omega , \\ u=0, &{}\hbox {on }\;\partial \Omega , \end{array} \right. \end{aligned}$$where $$N\ge 2$$ and $$1