A note on electromagnetic and gravitational perturbations of the Bardeen de Sitter black hole: quasinormal modes and greybody factors

Bardeen de-Sitter (BdS) black hole is a spherically symmetric solution of Einstein's equation which is coupled to nonlinear electromagnetic field in a way that one gets a regular solution, devoid of any singularity at the origin. We compute the quasinormal (QN) frequencies for BdS black hole due to electromagnetic and gravitational perturbations. We analyse the behaviour of both real and imaginary parts of BdS QN frequencies by varying the black hole parameters and compare frequencies with Reissner-Nordström de-Sitter (RN-dS) black hole. Interestingly, we find that the response of BdS and RN-dS black holes under electromagnetic and gravitational perturbations are different when the charge parameter is varied, which can be used to understand nonlinear and linear electromagnetic fields in curved spacetime separately. A study on the dynamics of perturbation as well as the scattering from the BdS black holes using WKB approach is performed. Greybody factors and their variations with black hole parameters are investigated.