Infinitely many solutions for a Ψ-Hilfer fractional problem

Ψ-Hilfer fractional derivative as a generalization of many important nonlocal derivatives such as Riemann-Liouville, Caputo and Hadamard fractional derivatives, has a great importance in fractional calculations and theory of fractional differential equations. Accordingly, in this paper, we study the multiplicity results for Ψ-Hilfer fractional problems. Specially, our goal is to establish the existence of infinitely many nontrivial or distinct weak solutions for a nonlocal Ψ-Hilfer fractional problem by using critical point theory.