Emanuela Caliceti, Sandro Graffi, Johannes Sjoestrand
SPECTRA OF PT-SYMMETRIC OPERATORS AND PERTURBATION THEORY
(33K, latex)

ABSTRACT.  Criteria are formulated both for the existence and for the 
non-existence of complex eigenvalues for a class of non 
self-adjoint operators in Hilbert space invarariant under a 
particular discrete symmetry. Applications to the PT-symmetric 
Schr\"odinger operators are discussed.