Curvature Invariants and Black Hole Horizons

2021 ◽  
Vol 65 (10) ◽  
pp. 947-951
Author(s):  
D. Gregoris
Keyword(s):  
Black Hole ◽  
Curvature Invariants

scholarly journals On the quantum improved Schwarzschild black hole

2020 ◽  
Vol 35 (04) ◽  
pp. 2050016
Author(s):  
R. Moti ◽  
A. Shojai
Keyword(s):  
Black Hole ◽  
Vacuum Solution ◽  
General Covariance ◽  
Gravitational Coupling ◽  
Curved Space ◽  
Curvature Invariants ◽  
Symmetric Vacuum ◽  
Non Gaussian ◽  
Exact Renormalization Group ◽  
Tensor Square

Deriving the gravitational effective action directly from exact renormalization group is very complicated, if not impossible. Hence, to study the effects of running gravitational coupling which tends to a non-Gaussian UV fixed point (as it is supposed by the asymptotic safety conjecture), two steps are usually adopted. Cutoff identification and improvement of the gravitational coupling to the running one. As suggested in Ref. 1, a function of all independent curvature invariants seems to be the best choice for cutoff identification of gravitational quantum fluctuations in curved space–time and makes the action improvement, which saves the general covariance of theory, possible. Here, we choose Ricci tensor square for this purpose and then the equation of motion of improved gravitational action and its spherically symmetric vacuum solution are obtained. Indeed, its effect on the massive particles’ trajectory and the black hole thermodynamics is studied.

Gravitational collapse and dark universe with LTB geometry

2016 ◽  
Vol 26 (06) ◽  
pp. 1750045 ◽  
Author(s):  
M. Zaeem-ul-Haq Bhatti ◽  
Z. Yousaf
Keyword(s):  
Black Hole ◽  
Electromagnetic Field ◽  
Time Interval ◽  
Curvature Scalar ◽  
Field Equations ◽  
Dark Sector ◽  
Curvature Invariants ◽  
Text Model ◽  
Polynomial Formula ◽  
Electrically Charged

The objective of this paper is to examine the influence of polynomial [Formula: see text] dark sector cosmic terms on the collapse of electrically charged Lemaître–Tolman–Bondi geometry. We explored a class of solutions for [Formula: see text] field equations in the existence of electromagnetic field and under the constraint of constant curvature scalar. The influence of [Formula: see text] model on the dynamics of collapsing object have been discussed by studying its black hole and cosmological horizons. Also, the effects of these dark sources on the time interval between the corresponding singularities and horizons have been studied. We investigated that the process of collapse slows down due to the higher order curvature invariants of polynomial [Formula: see text] model and electromagnetic field.

scholarly journals Curvature invariants and lower dimensional black hole horizons

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Daniele Gregoris ◽  
Yen Chin Ong ◽  
Bin Wang
Keyword(s):  
Black Hole ◽  
Local Extremum ◽  
Tidal Force ◽  
Curvature Invariants ◽  
Dimensional Spacetime ◽  
Dimensional Black Hole ◽  
Cartan Invariants ◽  
Cartan Curvature ◽  
Curvature Tensors ◽  
Lower Dimensional

AbstractIt is known that the event horizon of a black hole can often be identified from the zeroes of some curvature invariants. The situation in lower dimensions has not been thoroughly clarified. In this work we investigate both ($$2+1$$2+1)- and ($$1+1$$1+1)-dimensional black hole horizons of static, stationary and dynamical black holes, identified with the zeroes of scalar polynomial and Cartan curvature invariants, with the purpose of discriminating the different roles played by the Weyl and Riemann curvature tensors. The situations and applicability of the methods are found to be quite different from that in 4-dimensional spacetime. The suitable Cartan invariants employed for detecting the horizon can be interpreted as a local extremum of the tidal force suggesting that the horizon of a black hole is a genuine special hypersurface within the full manifold, contrary to the usual claim that there is nothing special at the horizon, which is said to be a consequence of the equivalence principle.

Construction of thin shell wormholes from metric f(R) gravity

2017 ◽  
Vol 32 (20) ◽  
pp. 1750111 ◽  
Author(s):  
M. Zaeem-ul-Haq Bhatti ◽  
A. Anwar ◽  
S. Ashraf
Keyword(s):  
Black Hole ◽  
Equation Of State ◽  
Thin Shell ◽  
Chaplygin Gas ◽  
Spherically Symmetric ◽  
Modified Chaplygin Gas ◽  
Potential Approach ◽  
Curvature Invariants ◽  
Radial Perturbation ◽  
Thin Shell Wormholes

In this paper, we have constructed spherically symmetric thin-shell wormholes (WHs) by surgically grafting two geometries of charged black hole in the framework of f(R) higher curvature invariants (threaded by exotic matter). We have investigated the stable/unstable regimes for couple of f(R) models using the potential approach formulated by Eiroa with radial perturbation. We have categorized our analysis for different values of charge as well as the parameters involved in the particular mode of f(R) gravity. We have found both stable and unstable regions using modified Chaplygin gas in this scenario and the results are shown through plots. We found that there exists a parametric space for equation of state and quadratic as well as cubic gravities in which one can accommodate more stable thin-shell WHs.

scholarly journals A critical assessment of black hole solutions with a linear term in their redshift function

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Daniele Gregoris ◽  
Yen Chin Ong ◽  
Bin Wang
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Black Hole Solution ◽  
Massive Gravity ◽  
Linear Term ◽  
Curvature Invariants ◽  
Stable Circular Orbit ◽  
De Rham ◽  
Innermost Stable Circular Orbit ◽  
Theories Of Gravity

AbstractDifferent theories of gravity can admit the same black hole solution, but the parameters usually have different physical interpretations. In this work we study in depth the linear term $$\beta r$$ β r in the redshift function of black holes, which arises in conformal gravity, de Rham–Gabadadze–Tolley (dRGT) massive gravity, f(R) gravity (as approximate solution) and general relativity. Geometrically we quantify the parameter $$\beta $$ β in terms of the curvature invariants. Astrophysically we found that $$\beta $$ β can be expressed in terms of the cosmological constant, the photon orbit radius and the innermost stable circular orbit (ISCO) radius. The metric degeneracy can be broken once black hole thermodynamics is taken into account. Notably, we show that under Hawking evaporation, different physical theories with the same black hole solution (at the level of the metric) can lead to black hole remnants with different values of their physical masses with direct consequences on their viability as dark matter candidates. In particular, the mass of the graviton in massive gravity can be expressed in terms of the cosmological constant and of the formation epoch of the remnant. Furthermore the upper bound of remnant mass can be estimated to be around $$0.5 \times 10^{27}$$ 0.5 × 10 27 kg.

scholarly journals Regular model of magnetized black hole with rational nonlinear electrodynamics

2021 ◽  
pp. 2150158
Author(s):  
S. I. Kruglov
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
General Relativity ◽  
Black Hole ◽  
Nonlinear Electrodynamics ◽  
De Sitter ◽  
Regular Model ◽  
Curvature Invariants ◽  
Fundamental Length ◽  
Gravity Effects

A modified Hayward metric of magnetically charged black hole space–time based on rational nonlinear electrodynamics with the Lagrangian [Formula: see text] is considered. We introduce the fundamental length, characterizing quantum gravity effects. If the fundamental length vanishes the general relativity coupling to rational nonlinear electrodynamics is recovered. We obtain corrections to the Reissner–Nordström solution as the radius approaches infinity. The metric possesses a de Sitter core without singularities as [Formula: see text]. The Hawking temperature and the heat capacity are calculated. It was shown that phase transitions occur and black holes are thermodynamically stable at some event horizon radii. We demonstrate that curvature invariants are bounded and the limiting curvature conjecture takes place.

scholarly journals Rotating spacetimes generalizing Lifshitz black holes

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Alfredo Herrera-Aguilar ◽  
Jhony A. Herrera-Mendoza ◽  
Daniel F. Higuita-Borja
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Solution ◽  
Causal Structure ◽  
Global Perspective ◽  
Local Analysis ◽  
Specific Heats ◽  
Curvature Invariants ◽  
Lifshitz Black Holes ◽  
Rotation Parameters

AbstractWe present a spinning black hole solution in d dimensions with a maximal number of rotation parameters in the context of the Einstein–Maxwell-Dilaton theory. An interesting feature of such a solution is that it accommodates Lifshitz black holes when the rotation parameters are set to zero. We verify the rotating nature of the black hole solution by performing the quasi-local analysis of conserved charges and defining the corresponding angular momenta. In addition, we perform the thermodynamical analysis of the black hole configuration, show that the first law of thermodynamics is completely consistent, and obtain a Smarr-like formula. We further study the thermodynamic stability of the constructed solution from a local viewpoint, by computing the associated specific heats, and from a global perspective, by using the so-called new thermodynamic geometry. We finally make some comments related to a pathology found in the causal structure of the obtained rotating black hole spacetime and compute some of its curvature invariants.

scholarly journals Thermodynamic stability of the stationary Lifshitz black hole of new massive gravity

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
K. Kolev ◽  
K. Staykov ◽  
T. Vetsov
Keyword(s):  
Black Hole ◽  
Phase Transitions ◽  
Thermodynamic Stability ◽  
Black Hole Solution ◽  
Information Geometry ◽  
Massive Gravity ◽  
Equilibrium States ◽  
Point Of View ◽  
Curvature Invariants ◽  
Lifshitz Black Hole

AbstractIn this paper we investigate the thermodynamic properties of the stationary Lifshitz black hole solution of New Massive Gravity. We study the thermodynamic stability from local and global point of view. We also consider the space of equilibrium states for the solution within the framework of thermodynamic information geometry. By investigating the proper thermodynamic metrics and their curvature invariants we find a set of restrictions on the parameter space and the critical points indicating phase transitions of the system. We confirm our findings by analytical analysis of the geodesics on the space of equilibrium states.

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