Quasinormal modes of Kerr-Newman black holes: coupling of electromagnetic and gravitational perturbations

We compute numerically the quasinormal modes of Kerr-Newman black holes in the scalar case, for which the perturbation equations are separable. Then we study different approximations to decouple electromagnetic and gravitational perturbations of the Kerr-Newman metric, computing the corresponding quasinormal modes. Our results suggest that the Teukolsky-like equation derived by Dudley and Finley gives a good approximation to the dynamics of a rotating charged black hole for Q<M/2. Though insufficient to deal with Kerr-Newman based models of elementary particles, the Dudley-Finley equation should be adequate for astrophysical applications.Comment: 13 pages, 3 figures. Minor changes to match version accepted in Phys. Rev.

Cardy-Verlinde Formula and entropy bounds in Kerr-Newman-AdS4_4/dS4_4 black holes backgrounds

The Cardy-Verlinde formula is further verified by using the Kerr-Newman-AdS$_4$ and Kerr-Newman-dS$_4$ black holes. In the Kerr-Newman-AdS$_4$ spacetime, we find that, for strongly coupled CFTs with AdS duals, to cast the entropy of the CFT into the Cardy-Verlinde formula the Casimir energy must contains the terms $-n ({\mathcal{J}} \Omega_H+ \frac{Q\Phi}{2}+ \frac{Q\Phi_0}{2})$, which associate with rotational and electric potential energies, and the extensive energy includes the term $-Q \Phi_0$. For the Kerr-Newman-dS$_4$ black hole, we note that the Casimir energy is negative but the extensive energy is positive on the cosmological horizon; while the Casimir energy is positive but the extensive energy is negative on the event horizon (the definitions for the two energies possess the same forms as the corresponding quantities of the Kerr-Newman-AdS$_4$ black hole). Thus we have to take the absolute value of the Casimir (extensive) energy in the Cardy-Verlinde formula for the cosmological (event) horizon. The result for the Kerr-Newman-dS$_4$ spacetime provides support of the dS/CFT correspondence. Furthermore, we also obtain the Bekenstein-Verlinde-like entropy bound for the Kerr-Newman-AdS$_4$ black hole and the D-bound on the entropy of matter system in Kerr-Newman-dS$_4$ spacetime. We find that both the bounds are tightened by the electric charge.Comment: 14 pages, no figur

Neutrino Quasinormal Modes of a Kerr-Newman-de Sitter Black Hole

Using the P\"{o}shl-Teller approximation, we evaluate the neutrino quasinormal modes (QNMs) of a Kerr-Newman-de Sitter black hole. The result shows that for a Kerr-Newman-de Sitter black hole, massless neutrino perturbation of large $\Lambda$, positive $m$ and small value of $n$ will decay slowly.Comment: 25 pages, 13 figure

The Quasinormal Modes of Weakly Charged Kerr-Newman Spacetimes

The resonant mode spectrum of the Kerr-Newman spacetime is presently unknown. These modes, called the quasinormal modes, play a central role in determining the stability of Kerr-Newman black holes and their response to perturbations. We present a new formalism, generalized from time-independent perturbation theory in quantum mechanics, for calculating the quasinormal mode frequencies of weakly charged Kerr-Newman spacetimes of arbitrary spin. Our method makes use of an original technique for applying perturbation theory to zeroth-order solutions that are not square- integrable, and it can be applied to other problems in theoretical physics. The new formalism reveals no unstable modes, which together with previous results in the slow-rotation limit strongly indicates the modal stability of the Kerr-Newman spacetime. Our techniques and results are of interest in the areas of holographic duality, foundational problems in General Relativity, and possibly in astrophysical systems.Comment: 4+3 pages, 2 figures, data (along with a read-me file) provided for eight mode

Accretion of New Variable Modified Chaplygin Gas and Generalized Cosmic Chaplygin Gas onto Schwarzschild and Kerr-Newman Black holes

In this work, we have studied accretion of the dark energies NVMCG and GCCG onto the Schwarzschild and Kerr-Newman Black holes. We find the expression of the critical four velocity component which gradually decreases for the fluid flow towards the Schwarzschild as well as Kerr-Newman Black hole. We also find the expression for change of masses of the black hole in both cases. For the Kerr-Newman black hole which is rotating and charged we calculate the specific angular momentum and total angular momentum. We showed that in both cases due to accretion of the dark energy mass of the black hole increases and angular momentum increases in case of Kerr-Newman black hole.Comment: 12 pages, 14 figures, Accepted for publication in European Physical Journal

Entropy in the NUT-Kerr-Newman Black Holes Due to an Arbitrary Spin Field

Membrane method is used to compute the entropy of the NUT-Kerr-Newman black holes. It is found that even though the Euler characteristic is greater than two, the Bekenstein-Hawking area law is still satisfied. The formula $S=\chi A/8$ relating the entropy and the Euler characteristic becomes inapplicable for non-extreme four dimensional NUT-Kerr-Newman black holes