QUASI-NORMAL MODES OF REISSNER-NORDSTROM BLACK-HOLES - PHASE-INTEGRALAPPROACH

This paper presents quasinormal-model frequencies for Reissner-Nordstr om black holes calculated using the phase-integral approximation. It i s shown that the eigenfrequencies of the first modes (those with small imaginary parts) are accurately determined by the so-called Bohr-Somm erfeld formula. The formula generates frequencies with roughly the sam e accuracy as obtained in the Schwarzschild case except when the charg e is close to its limiting value. For higher modes a generalized formu la, recently derived by the present authors is used. Numerical calcula tions show that, while it is reasonably accurate for low charges, this formula cannot be trusted for high charges. An intrinsic estimate of the error in the phase-integral calculations is also discussed.