LOGARITHMIC PERTURBATION-THEORY FOR QUASI-NORMAL MODES

Logarithmic perturbation theory (LPT) is developed and applied to quas inormal modes (QNMs) in open systems. QNMs often do not form a complet e set, so LPT is especially convenient because summation over a comple te set of unperturbed states is not required. Attention is paid to pot entials with exponential tails, and the example of a Poschl-Teller pot ential is briefly discussed. A numerical method is developed that hand les the exponentially large wavefunctions which appear in dealing with QNMs.