EXISTENCE AND PERTURBATION OF PRINCIPAL EIGENVALUES FOR A PERIODIC-PARABOLIC PROBLEM

We give a necessary and sufficient condition for the existence of a positive principal eigenvalue for a periodic-parabolic problem with indefinite weight function.The condition was originally established by Beltramo and 2006 nissan altima radio Hess [extit{frenchspacing Comm.Part.Diff.Eq.}, extbf{9} (1984), 919--941] in the framework of the Schaude