Another way to say subsolution: the maximum principle and sums of Green functions

Authors

  • R.S. Laugesen
  • N. A. Watson

DOI:

https://doi.org/10.7146/math.scand.a-14968

Abstract

Consider an elliptic second order differential operator L with no zeroth order term (for example the Laplacian L=Δ). If Lu0 in a domain U, then of course u satisfies the maximum principle on every subdomain VU. We prove a converse, namely that Lu0 on U if on every subdomain V, the maximum principle is satisfied by u+v whenever v is a finite linear combination (with positive coefficients) of Green functions with poles outside ¯V. This extends a result of Crandall and Zhang for the Laplacian. We also treat the heat equation, improving Crandall and Wang's recent result. The general parabolic case remains open.

Downloads

Published

2005-09-01

How to Cite

Laugesen, R., & Watson, N. A. (2005). Another way to say subsolution: the maximum principle and sums of Green functions. MATHEMATICA SCANDINAVICA, 97(1), 127–153. https://doi.org/10.7146/math.scand.a-14968

Issue

Section

Articles