I was asked to discuss quasinormal modes in the context of black holes.
Think about a linearized differential equation like the one in general relativity or a Schrodinger tyoe equation. The solutions of these equations with some boundary conditions are called quasinormal modes. In the case of quasinormal modes that the eigenvalue may be complex. The imaginary part of the eigenvalue (frequency) relates to the exponential decrease of the wavefunction in time. A geometry of a perturbed black hole will be a ring after a damped oscillation. The frequencies and the damping time are independent of the the initual perubation. The field can fall radiate to infinity or fall into the blackhole. The modes decay and the corresponding frequencies are complex. These oscillations are known as quasinormal modes.A quasinormal mode of a blackhole would exponentially decrease the asymmetry of blackhole. This occurs as the black hole evolves in time to be a spherical object. One of the successed of string theory is to (re)derive the Bekenstein-Hawking entropy by counting black hole microstates. This was derived by for a five dimensional extremal black holes in string theory by counting the degeneracy of BPS soliton bound states. More on quasinormal modes/black holes to follow….
Tags: Black Holes, Quasi Normal modes
