Quasilinear systems involving curl

Abstract

We study a quasilinear degenerately elliptic system involving the operator curl. The leading-order term of the associated energy functional is a q-power of curl of the unknowns. It is interesting to us that the structure of the lower-order terms will play an important role in both the existence and regularity of the solutions. When the lower-order part of the energy functional is convex we obtain weak solutions by minimizing the functional in some suitable spaces of vector fields. When it is concave we obtain critical points of the truncated functional, which are weak solutions of a nonlinear eigenvalue problem. We also examine the interior Hölder regularity of the weak solutions, which indicates that the weak solution is composed of a ‘good’ divergence-free part and a ‘bad’ part in gradient form. The analysis involves local higher integrability and local Hölder gradient estimates for a translated q′-Laplace equation and a translated quasilinear equation with p-growth.