Morrey estimates for the gradient in non-linear variational transmission problems

Abstract

We study a class of variational transmission problems driven by nonlinear energies with discontinuous coefficients across a prescribed interface. The model setting consists of integral functionals of the form \[ \mathcal{F}(u;E)=\int_Ωσ_E(x)\,F(\nabla u)\,dx, \] where the coefficient $\ddot{I}{ƒ}_E$ takes two constant values on complementary regions separated by a $C^1$ hypersurface, and the integrand $F$ satisfies standard $p$-growth and monotonicity conditions with $p>2$. In this nonlinear variational framework, we establish local Morrey-space regularity for the gradient of local minimizers, proving that $\nabla u\in L_{\mathrm{loc}}^{2,\hat{I}»}(\hat{I}\text{c◯})$ for every $0\le \hat{I}»<n$, provided $2<p<\frac{2n}{n-2}$. The proof is based on quantitative decay estimates for the energy near the interface, first obtained in a flat configuration and then extended to the general case by a suitable approximation argument.