Abstract
We establish new, optimal geometric gradient estimates for solutions to a class of 2nd order partial differential equations, \(\mathcal {L}(X, \nabla u, D^2 u) = f\), whose diffusion properties (ellipticity) degenerate along the a priori unknown set of critical points of an existing solution, \(\mathcal {S}(u) := \{ X : \nabla u(X) = 0 \}\). Such a quantitative information plays a decisive role in the analysis of a number of analytic and geometric problems. The results proven in this work are new even for simple equation \(|\nabla u | \cdot \Delta u = 1\). Under natural nondegeneracy condition on the source term \(f\), we further establish the precise asymptotic behavior of solutions at interior gradient vanishing points. These new estimates are then employed in the study of some well known problems in the theory of elliptic PDEs.
Similar content being viewed by others
References
Birindelli, I., Demengel, F.: Comparison principle and Liouville type results for singular fully nonlinear operators. Ann. Fac. Sci Toulouse Math. (6) 13, 261–287 (2004)
Birindelli, I., Demengel, F.: Eigenvalue, maximum principle and regularity for fully non linear homogeneous operators. Commun. Pure Appl. Anal. 6, 335–366 (2007)
Birindelli, I., Demengel, F.: Eigenvalue and Dirichlet problem for fully-nonlinear operators in non-smooth domains. J. Math. Anal. Appl. 352, 822–835 (2009)
Birindelli, I., Demengel, F.: \(C^{1,\beta }\) regularity for Dirichlet problems associated to fully nonlinear degenerate elliptic equations. COCV (to appear, 2104)
Caffarelli, L.A.: Interior a priori estimates for solutions of fully nonlinear equations. Ann. Math. (2) 130(1), 189–213 (1989)
Caffarelli, L.A., Cabré, X.: Fully nonlinear elliptic equations. American Mathematical Society Colloquium Publications, vol. 43. American Mathematical Society, Providence (1995)
Caffarelli, L., Salazar, J.: Solutions of fully nonlinear elliptic equations with patches of zero gradient: existence, regularity and convexity of level curves. Trans. Am. Math. Soc. 354(8), 3095–3115 (2002)
Caffarelli, L., Salazar, J., Shahgholian, H.: Free-boundary regularity for a problem arising in superconductivity. Arch. Rational. Mech. Anal. 171(1), 115–128 (2004)
Chapman, S.J.: A mean-field model of superconducting vortices in three dimensions. SIAM J. App. Math. 55, 1259–1274 (1995)
Crandall, M.G., Ishii, H., Lions, P.L.: User’s guide to viscosity solutions of second order partial differential equations. Bull. Am. Math. Soc. (N.S.) 27(1), 1–67 (1992)
Dávila, G., Felmer, P., Quaas, A.: Alexandroff–Bakelman–Pucci estimate for singular or degenerate fully nonlinear elliptic equations. C. R. Math. Acad. Sci. Paris 347, 1165–1168 (2009)
Evans, L.C.: Classical solutions of fully nonlinear, convex, second-order elliptic equations. Commun. Pure Appl. Math. 35(3), 333–363 (1982)
Evans, L.C., Savin, O.: \(C^{1, \alpha }\) regularity for infinity harmonic functions in two dimensions. Calc. Var. Partial Differ. Equ. 32, 325–347 (2008)
Evans, L.C., Smart, C.K.: Everywhere differentiability of infinity harmonic functions. Calc. Var. Partial Differ. Equ. 42, 289–299 (2011)
Guisti, E.: Direct Methods in the Calculus of Variations. World Scientific Publishing, Singapore (2003)
Imbert, C.: Alexandroff–Bakelman–Pucci estimate and Harnack inequality for degenerate/singular fully non-linear elliptic equations. J. Differ. Equ. 250, 1553–1574 (2011)
Imbert, C., Silvestre, L.: \(C^{1,\alpha }\) regularity of solutions of degenerate fully non-linear elliptic equations. Adv. Math. 233, 196–206 (2013)
Ishii, H.: On uniqueness and existence of viscosity solutions of fully nonlinear second-order elliptic PDE’s. Commun. Pure Appl. Math. 42, 14–45 (1989)
Iwaniec, T., Manfredi, J.: Regularity of p-harmonic functions in the plane. Revista Matematica Iberoamericana 5, 1–19 (1989)
Juutinen, P., Lindqvist, P., Manfredi, J.J.: On the equivalence of viscosity solutions and weak solutions for a quasi-linear elliptic equation. SIAM J. Math. Anal. 33, 699–717 (2001)
Krylov, N.V.: Boundedly nonhomogeneous elliptic and parabolic equations. Izv. Akad. Nak. SSSR Ser. Mat. 46, 487–523 (1982). English transl. in Math. USSR Izv. 20, 459–492 (1983)
Krylov, N.V.: Boundedly nonhomogeneous elliptic and parabolic equations in a domain. Izv. Akad. Nak. SSSR Ser. Mat. 47, 75–108 (1983). English transl. in Math. USSR Izv. 22, 67–97 (1984)
Lee, K., Shahgholian, H.: Hausdorff dimension and stability for the \(p\)-obstacle problem\((2<p<\infty )\). J. Differ. Equ. 195(1), 14–24 (2003)
Nadirashvili, N., Vladut, S.: Nonclassical solutions of fully nonlinear elliptic equations. Geom. Funct. Anal. 17(4), 1283–1296 (2007)
Nadirashvili, N., Vladut, S.: Singular viscosity solutions to fully nonlinear elliptic equations. J. Math. Pure Appl. (9) 89(2), 107–113 (2008)
Nadirashvili, N., Vladut, S.: Nonclassical solutions of fully nonlinear elliptic equations II. Hessian equations and octonions. Geom. Funct. Anal. 21, 483–498 (2011)
Rossi, J.D., Teixeira, E.V., Urbano, J.: Miguel optimal regularity at the free boundary for the infinity obstacle problem (Preprint)
Savin, O.: \(C^1\) regularity for infinity harmonic functions in two dimensions. Arch. Rational Mech. Anal. 176, 351–361 (2005)
Savin, O.: Small perturbation solutions for elliptic equations. Commun. Partial Differ. Equ. 32(4–6), 557–578 (2007)
Savin, O.: Regularity of flat level sets in phase transitions. Ann. Math. (2) 169(1), 41–78 (2009)
Teixeira, E.V.: Sharp regularity for general Poisson equations with borderline sources. J. Math. Pure Appl. (9) 99(2), 150–164 (2013)
Teixeira, E.V.: Universal moduli of continuity for solutions to fully nonlinear elliptic equations. Arch. Rational Mech. Anal. 211(3), 911–927 (2014)
Teixeira, E.V.: Regularity for quasilinear equations on degenerate singular sets. Math. Ann. 358(1), 241–256 (2014)
Uraltseva, N.N.: Degenerate quasilinear elliptic systems. Zap. Na. Sem. Leningrad. Otdel. Mat. Inst. Steklov. (LOMI) 7, 184–222 (1968)
Acknowledgments
The authors would like to thank Luis Silvestre for insightful and stimulating comments and suggestions. This work has been partially supported by CNPq-Brazil.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by O. Savin.
Rights and permissions
About this article
Cite this article
Araújo, D.J., Ricarte, G. & Teixeira, E.V. Geometric gradient estimates for solutions to degenerate elliptic equations. Calc. Var. 53, 605–625 (2015). https://doi.org/10.1007/s00526-014-0760-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00526-014-0760-7