Quasinormal modes as a distinguisher between general relativity and f(R) gravity: Charged black-holes

The ring-down phase of black-hole perturbations is governed by the Quasi-Normal modes (QNM) and offer valuable insight into the nature of the objects emitting them. In General relativity, we identify a dimensionless parameter that can estimate the charge of a black-hole from the energetics of quasi-normal modes. We then extend the analysis for f(R) theories of gravity. Using Isaacson's prescription to modified theories of gravity, we obtain an accurate and robust method to estimate the difference in the radiated energies in the scalar and vector modes due to modifications to general relativity. We then discuss how to quantify the deviation from general relativity.