Properties of solutions to variational problems

In the context of the variational problems related to integral functionals, we study some necessary conditions for a solution u without standard growth assumptions and strong differentiability conditions on the Lagrangian L. In particular, we investigate the validity of the Euler-Lagrange equation, in its classical and non-classical form, in the cases of functionals with non-differentiable convex Lagrangian or with super-exponential growth for L. Moreover, we investigate the regularity properties for minimizers, concerning higher integrability of the gradient as well as higher differentiability under general growth conditions and mild differentiability assumptions on L.