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.