Schwarzschild-de Sitter Background Research Articles

Massive scalar field perturbations of black holes immersed in Chaplygin-like dark fluid

We consider massive scalar field perturbations in the background of black holes immersed in Chaplygin-like dark fluid (CDF), and we analyze the photon sphere modes, the de Sitter modes as well as the near extremal modes and discuss their dominance, by using the pseudospectral Chebyshev method and the third order Wentzel-Kramers-Brillouin approximation. We also discuss the impact of the parameter representing the intensity of the CDF on the families of quasinormal modes. Mainly, we find that the propagation of a massive scalar field is stable in this background, and it is characterized by quasinormal frequencies with a smaller oscillation frequency and a longer decay time compared to the propagation of the same massive scalar field within the Schwarzschild-de Sitter background.

Analytic formula for quasinormal modes in the near-extreme Kerr-Newman–de Sitter spacetime governed by a non-Pöschl-Teller potential

Quasinormal modes of scalar, electromagnetic, and gravitational fields in the extreme Schwarzschild-de Sitter background are known to be expressed in analytic form as eigenvalues of the P\"oschl-Teller wavelike equation. We show that perturbations of fermionic fields (given by Dirac and Rarita-Schwinger equations) do not lead to the P\"oschl-Teller effective potential. Nevertheless, using the Frobenius method we find quasinormal modes analytically in this case as well. We write down the analytical formula for quasinormal frequencies of the near-extreme Schwarzschild-de Sitter black holes, which is valid for both bosonic and fermionic fields. We further extend the analysis to the case of charged rotating black holes and find a general analytical formula for quasinormal modes of the fields of various spin for the near extreme Kerr-Newman-de Sitter spacetime.

Anomalous decay rate of quasinormal modes in Schwarzschild-dS and Schwarzschild-AdS black holes

Recently an anomalous decay rate of the quasinormal modes of a massive scalar field in Schwarzschild black holes backgrounds was reported in which the longest-lived modes are the ones with higher angular number, for a scalar field mass smaller than a critical value, while that beyond this value the behaviour is inverted. In this work, we extend the study to other asymptotic geometries, such as, Schwarzschild-de Sitter and Schwarzschild-AdS black holes. Mainly, we found that such behaviour and the critical mass are present in the Schwarzschild-de Sitter background. Also, we found that the value of the critical mass increases when the cosmological constant increases and also when the overtone number is increasing. On the other hand, despite the critical mass is not present in Schwarzschild-AdS black holes backgrounds, the decay rate of the quasinormal modes always exhibits an anomalous behaviour.

Nonequatorial circular orbits of spinning particles in the Schwarzschild–de Sitter background

In this paper analytical solutions of the Mathisson-Papapetrou equations that describe nonequatorial circular orbits of a spinning particle in the Schwarzschild-de Sitter background are studied, and the role of the cosmological constant is emphasized. It is shown that generally speaking a highly relativistic velocity of the particle is a necessary condition of motion along this type of orbits, with an exception of orbits locating close to the position of the static equilibrium, where low velocities are possible as well. Depending on the correlation between the spin orientation of the particle and its orbital velocity some of the possible nonequatorial circular orbits exist due to the repulsive action on the particle caused by the spin-gravity coupling and the others are caused by the attractive action.Here values of the energy of the particle on the corresponding orbits are also analyzed.

Highly relativistic spin-gravity- Λ coupling

The effects of highly relativistic spin-gravity coupling in the Schwarzschild-de Sitter background which follow from the Mathisson-Papapetrou equations are investigated. The dependence of gravitoelectric and gravitomagnetic components of gravitational field on the velocity of an observer which is moving in Schwarzschild-de Sitter's background is estimated. The action of gravitomagnetic components on a fast moving spinning particle is considered. Different cases of the highly relativistic circular orbits of a spinning particle which essentially differ from the corresponding geodesic orbits are described.

Scalar field as a Bose–Einstein condensate in a Schwarzschild–de Sitter spacetime

In this paper, we analyze some properties of a scalar field configuration, where it is considered as a trapped Bose–Einstein condensate in a Schwarzschild–de Sitter background spacetime. In a natural way, the geometry of the curved spacetime provides an effective trapping potential for the scalar field configuration. This allows us to explore some thermodynamical properties of the system. Additionally, the curved geometry of the spacetime also induces a position-dependent self-interaction parameter, which can be interpreted as a kind of gravitational Feshbach resonance, that could affect the stability of the cloud and could be used to obtain information about the interactions among the components of the system.

The cosmological constant and the gravitational light bending

The solution of the null non-radial geodesic in a Schwarzschild-de Sitter background is revisited. The gravitational bending of a light ray is affected by the cosmological constant, in agreement with the findings of some previous investigations. The present study confirms that the leading correction term depends directly not only on Λ but also on the impact parameter and on the angular distance to the source. Using the resulting lens equation, the projected mass of the lens was estimated for several systems displaying Einstein rings. Corrections on the masses due to Λ are, on the average, of the order of 2%, indicating that they are not completly negligible for lens systems at cosmological distances.

Bending of light in conformal Weyl gravity

We reexamine the bending of light issue associated with the metric of the static, spherically symmetric solution of Weyl gravity discovered by Mannheim and Kazanas (1989). To this end we employ the procedure used recently by Rindler and Ishak to obtain the bending angle of light by a centrally concentrated spherically symmetric matter distribution in a Schwarzschild-de Sitter background. In earlier studies the term {gamma}r in the metric led to the paradoxical result of a bending angle proportional to the photon impact parameter, when using the usual formalism appropriate to asymptotically flat space-times. However, employing the approach of light bending of Rindler and Ishak we show that the effects of this term are in fact insignificant, with the discrepancy between the two procedures attributed to the definition of the bending angle between the asymptotically flat and nonflat spaces.

Stability of branes trapped byd-dimensional black holes

The system of extended objects interacting with a black hole describes or mimics various gravitational phenomena. In this brief paper, we report the results of stability analysis of codimension-one Dirac-Nambu-Goto branes at rest at the equatorial plane of $d$-dimensional spherical black holes, including the Schwarzschild and Schwarzschild-(anti-)de Sitter black holes. For the Schwarzschild and Schwarzschild-anti-de Sitter backgrounds the stability of branes is shown analytically by means of a deformation technique. In contrast, for the Schwarzschild-de Sitter background we demonstrate with the help of numerics that the brane is unstable (only) against the $s$-wave sector of perturbations.

On the stability of spherical membranes in curved space-times

We study the existence and stability of spherical membranes in curved space-times. For Dirac membranes in the Schwarzschild-de Sitter background we find that there exists an equilibrium solution. By fine-tuning the dimensionless parameter ΛM 2, the static membrane can be at any position outside the black hole event horizon, even at the stretched horizon, but the solution is unstable. We show that modes having l = 0 (and for ΛM 2 < 16/243 also l = 1) are responsible for the instability. We also find that spherical higher order membranes (membranes with extrinsic curvature corrections), contrary to what happens in flat Minkowski space, do have equilibrium solutions in a general curved background and, in particular, also in the “plain” Schwarzschild geometry (while Dirac membranes do not have equilibrium solutions there). These solutions, however, are also unstable. We shall discuss a way of bypassing these instability problems, and we also relate our results to the recent ideas of representing the black hole event horizon as a relativistic bosonic membrane.