Electronic Journal of Differential Equations,
Conference 05 (2000), pp. 173-180.

Title: Existence of a principal eigenvalue for the Tricomi problem.

Authors: Daniela Lupo (Politecnico di Milano, Milano, Italy)
  Kevin R. Payne (Politecnico di Milano, Milano, Italy)
 
Abstract: 
  The existence of a principal eigenvalue is established for the Tricomi problem
  in normal domains; that is, the existence of a positive
  eigenvalue of minimum modulus with an associated positive eigenfunction.
  The argument here uses prior results of the authors on the generalized
  solvability in weighted Sobolev spaces and associated
  maximum/minimum principles \cite{[LP2]} coupled with known results
  of Krein-Rutman type.

Published October 24, 2000.
Math Subject Classifications: 35M10, 35P05, 35B10.
Key Words: Tricomi problem; mixed type equations; spectral theory;
  principal eigenvalue; maximum principle.