Higher differentiability of minimizers of convex variational integrals

In this paper we consider integral functionals of the form F(nu, Omega) = integral(Omega) F(D nu(x))dx with convex integrand satisfying (p, q) growth conditions. We prove local higher differentiability results for bounded minimizers of the functional F under dimension-free conditions on the gap between the growth and the coercivity exponents. As a novel feature, the main results are achieved through uniform higher differentiability estimates for solutions to a class of auxiliary problems, constructed adding singular higher order perturbations to the integrand. (C) 2011 Elsevier Masson SAS. All rights reserved.