Abstract

We obtain Lipschitz regularity results for a fairly general class of nonlinear first-order PDEs. These equations arise from the inner variation of certain energy integrals. Even in the simplest model case of the Dirichlet energy the inner-stationary solutions need not be differentiable everywhere; the Lipschitz continuity is the best possible. But the proofs, even in the Dirichlet case, turn out to relay on topological arguments. The appeal to the inner-stationary solutions in this context is motivated by the classical problems of existence and regularity of the energy-minimal deformations in the theory of harmonic mappings and certain mathematical models of nonlinear elasticity; specifically, neo-Hookian type problems.

Highlights

  • We establish Lipschitz regularity of solutions of nonlinear first-order PDEs that arise from inner variation of numerous energy integrals

  • When dealing with mappings with nonnegative Jacobian the inner variation is necessary to preserve the sign of the Jacobian

  • We look for h in the form h(z) = 2z ψ(−2 log|z|), |z| 1 where ψ : [0, ∞) → [1, ∞) is a strictly increasing function with ψ(0) = 1

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Summary

Introduction

We establish Lipschitz regularity of solutions of nonlinear first-order PDEs that arise from inner variation of numerous energy integrals. 2. Inner-variational equations Let us consider the energy integral for mappings h : Ω → C (2.1). Given any test function η ∈ C0∞(Ω) and a complex parameter t , small enough so that the map z → z + t η(z) represents a diffeomorphism of Ω onto itself, consider the inner variation ht(z) = h(z + tη) and its energy. Let h ∈ Wlo1c,1(Ω) be an inner-stationary mapping for the energy integral (2.6) with E [h] < ∞, where F satisfies the conditions (2.7)– (2.11). Subject to homeomorphisms h : Ω −on−→to Ω∗ in the Sobolev space W 1,2(Ω) This case gains additional interest in Geometric Function Theory because the transition to the energy of the inverse mapping f = h−1 : Ω∗ o−n−t→o Ω results in the L p-norm of the distortion function.

Elaborate statement and examples
Model case: the Hopf-Laplace equation
Good solutions
16 Sp 4 81 Sp L
Tω p 54 M
The difference of two solutions

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