Motivated by the partial differential equations of mixed type that arise in the reduction of the Einstein equations by a helical Killing vector field, we consider a boundary value problem for the helically-reduced wave equation with an arbitrary source in 2+1 dimensional Minkowski spacetime. The reduced equation is a second-order partial differential equation which is elliptic inside a disk and hyperbolic outside the disk. We show that the reduced equation can be cast into symmetric-positive form. Using results from the theory of symmetric-positive differential equations, we show that this form of the helically-reduced wave equation admits unique, strong solutions for a class of boundary conditions which include Sommerfeld conditions at the outer boundary.
Article
The Helically Reduced Wave Equation as a Symmetric Positive System
Journal of Mathematical Physics
Document Type
Article
Publisher
American Institute of Physics
Publication Date
1-1-2003
Disciplines
Abstract
Comments
Originally published by the American Institute of Physics. Publisher's PDF can be accessed through the Journal of Mathematical Physics.
http://arxiv.org/abs/math-ph/0309008
Citation Information
C.G. Torre, “The helically-reduced wave equation as a symmetric-positive system,” Journal of Mathematical Physics, vol. 44, 2003, p. 6223.