scholarly journals Constraining the number of horizons with energy conditions

2021 ◽  
Author(s):  
Run-Qiu Yang ◽  
Rong-Gen Cai ◽  
Li Li
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Strong Energy ◽  
Killing Horizon ◽  
Static Black Hole ◽  
Matter Fields

Abstract We show that the number of horizons of static black holes can be strongly constrained by energy conditions of matter fields. After a careful clarification on the ``interior'' of a black hole, we prove that if the interior of a static black hole satisfies strong energy condition or null energy condition, there is at most one non-degenerated inner Killing horizon behind the non-degenerated event horizon. Our result offers some universal restrictions on the number of horizons. Interestingly and importantly, it also suggests that matter not only promotes the formation of event horizon but also prevents the appearance of multiple horizons inside black holes. Furthermore, using the geometrical construction, we obtain a radially conserved quantity which is valid for general static spacetimes.

scholarly journals New version of the gedanken experiments to test the weak cosmic censorship in charged dilaton-Lifshitz black holes

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Jie Jiang ◽  
Ming Zhang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Order Approximation ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Cosmic Censorship ◽  
Second Order ◽  
Lifshitz Black Holes ◽  
Lifshitz Black Hole ◽  
Matter Fields

AbstractIn this paper, based on the new version of the gedanken experiments proposed by Sorce and Wald, we examine the weak cosmic censorship in the perturbation process of accreting matter fields for the charged dilaton-Lifshitz black holes. In the investigation, we assume that the black hole is perturbed by some extra matter source satisfied the null energy condition and ultimately settle down to a static charged dilaton-Lifshitz black hole in the asymptotic future. Then, after applying the Noether charge method, we derive the first-order and second-order perturbation inequalities of the perturbation matter fields. As a result, we find that the nearly extremal charged dilaton-Lifshitz black hole cannot be destroyed under the second-order approximation of perturbation. This result implies that the weak cosmic censorship conjecture might be a general feature of the Einstein gravity, and it is independent of the asymptotic behaviors of the black holes.

scholarly journals BEHAVIOR OF TACHYON IN STRING COSMOLOGY BASED ON GAUGED WZW MODEL

2009 ◽  
Vol 24 (04) ◽  
pp. 277-289
Author(s):  
SUNGGEUN LEE ◽  
SOONKEON NAM
Keyword(s):  
Cosmological Model ◽  
Energy Condition ◽  
Flat Space ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Dilaton Field ◽  
Coset Space ◽  
Tachyon Field ◽  
Strong Energy ◽  
Matter Fields

We investigate a string theoretic cosmological model in the context of the gauged Wess–Zumino–Witten model. Our model is based on a product of non-compact coset space and a spectator flat space; [ SL (2, R)/ U (1)]k × ℝ2. We extend the formerly studied semiclassical consideration with infinite Kac–Moody level k to a finite one. In this case, the tachyon field appears in the effective action, and we solve the Einstein equation to determine the behavior of tachyon as a function of time. We find that tachyon field dominates over dilaton field in early times. In particular, we consider the energy conditions of the matter fields consisting of the dilaton and the tachyon which affect the initial singularity. We find that not only the strong energy but also the null energy condition is violated.

scholarly journals Charged BTZ black holes cannot be destroyed via the new version of the gedanken experiment

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Xin-Yang Wang ◽  
Jie Jiang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Energy Condition ◽  
Second Order ◽  
Order Perturbation ◽  
Conical Singularity ◽  
Gedanken Experiment ◽  
Btz Black Holes ◽  
Matter Fields

AbstractThe singularity at the center of charged Bañados–Teitelboim–Zanelli (BTZ) black holes is called a conical singularity. Unlike the canonical singularity in typical black holes, a conical singularity does not destroy the causality of spacetime. Due to the special property of the conical singularity, we examine the weak cosmic censorship conjecture (WCCC) using the new version of the gedanken experiment proposed by Sorce and Wald. A perturbation process wherein the spherically symmetric matter fields pass through the event horizon and fall into the black holes is considered. Assuming that the cosmological constant is obtained by the matter fields, it therefore can be seen as a dynamical variable during the process. From this perspective, according to the stability condition and the null energy condition, the first- and second-order perturbation inequalities are derived. Based on the first-order optimal condition and the second-order perturbation inequality, we show that the nearly extremal charged BTZ black hole cannot be destroyed in the above perturbation process. The result also implies that even if the singularity at the center of the black hole is conical, it still should be surrounded by the event horizon and hidden inside the black hole.

scholarly journals Extracting Hawking radiation near the horizon of AdS black holes

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Krishan Saraswat ◽  
Niayesh Afshordi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Evaporation Rate ◽  
Order Term ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Leading Order ◽  
Proper Distance ◽  
Ads Black Holes ◽  
A Cell

Abstract We study how the evaporation rate of spherically symmetric black holes is affected through the extraction of radiation close to the horizon. We adopt a model of extraction that involves a perfectly absorptive screen placed close to the horizon and show that the evaporation rate can be changed depending on how close to the horizon the screen is placed. We apply our results to show that the scrambling time defined by the Hayden-Preskill decoding criterion, which is derived in Pennington’s work (arXiv:1905.08255) through entanglement wedge reconstruction is modified. The modifications appear as logarithmic corrections to Pennington’s time scale which depend on where the absorptive screen is placed. By fixing the proper distance between the horizon and screen we show that for small AdS black holes the leading order term in the scrambling time is consistent with Pennington’s scrambling time. However, for large AdS black holes the leading order Log contains the Bekenstein-Hawking entropy of a cell of characteristic length equal to the AdS radius rather than the entropy of the full horizon. Furthermore, using the correspondence between the radial null energy condition (NEC) and the holographic c-theorem, we argue that the screen cannot be arbitrarily close to the horizon. This leads to a holographic argument that black hole mining using a screen cannot significantly alter the lifetime of a black hole.

scholarly journals Non-Rindler horizons and radiating black holes

2021 ◽  
pp. 2150184
Author(s):  
Vaibhav Wasnik
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Space Time ◽  
Coordinate Transformations ◽  
Spatial Infinity ◽  
Rindler Space ◽  
Black Hole Solutions

In this work we construct metrics corresponding to radiating black holes whose near horizon regions cannot be approximated by Rindler space–time. We first construct infinite parameter coordinate transformations from Minkowski coordinates, such that an observer using these coordinates to describe space–time events measures the Minkowski vacuum to be Planckian. Utilizing these results, we construct a family of black holes that radiate at spatial infinity. As an illustration, we study a subset of the black hole solutions and show that they satisfy the null energy condition.

scholarly journals Traversable wormhole in logarithmic f(R) gravity by various shape and redshift functions

2022 ◽  
Author(s):  
Jafar Sadeghi ◽  
Mehdi Shokri ◽  
Saeed Noori Gashti ◽  
Behnam Pourhassan ◽  
Prabir Rudra
Keyword(s):  
Energy Condition ◽  
Radial Pressure ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Dominant Energy Condition ◽  
Tangential Pressure ◽  
Strong Energy Condition ◽  
Traversable Wormhole ◽  
Strong Energy ◽  
Text Model

In this paper, we study the traversable wormhole solutions for a logarithmic corrected [Formula: see text] model by considering two different statements of shape [Formula: see text] and redshift [Formula: see text] functions. We calculate the parameters of the model including energy density [Formula: see text], tangential pressure [Formula: see text] and radial pressure [Formula: see text] for the corresponding forms of the functions. Then, we investigate different energy conditions such as null energy condition, weak energy condition, dominant energy condition and strong energy condition for our considered cases. Finally, we explain the satisfactory conditions of energy of the models by related plots.

scholarly journals Gedanken experiments at high-order approximation: Kerr black hole cannot be overspun

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Aofei Sang ◽  
Jie Jiang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Order Approximation ◽  
Energy Condition ◽  
Kerr Black Hole ◽  
Null Energy Condition ◽  
Higher Order ◽  
High Order ◽  
Order Perturbation ◽  
Kerr Black Holes

Abstract Sorce and Wald proposed a new version of gedanken experiments to examine the weak cosmic censorship conjecture (WCCC) in Kerr-Newmann black holes. However, their discussion only includes the second-order approximation of perturbation and there exists an optimal condition such that the validity of the WCCC is determined by the higher-order approximations. Therefore, in this paper, we extended their discussions into the high-order approximations to study the WCCC in a nearly extremal Kerr black hole. After assuming that the spacetime satisfies the stability condition and the perturbation matter fields satisfy the null energy condition, based on the Noether charge method by Iyer and Wald, we completely calculate the first four order perturbation inequalities and discuss the corresponding gedanken experiment to overspin the Kerr black hole. As a result, we find that the nearly extremal Kerr black holes cannot be destroyed under the fourth-order approximation of perturbation. Then, by using the mathematical induction, we strictly prove the nth order perturbation inequality when the first (n − 1) order perturbation inequalities are saturated. Using these results, we discuss the first 100 order approximation of the gedanken experiments and find that the WCCC in Kerr black hole is valid under the higher-order approximation of perturbation. Our investigation implies that the WCCC might be strictly satisfied in Kerr black holes under the perturbation level.

scholarly journals LOCAL FREE-FALL TEMPERATURE OF A RN–AdS BLACK HOLE

2010 ◽  
Vol 25 (15) ◽  
pp. 3107-3120 ◽  
Author(s):  
YONG-WAN KIM ◽  
JAEDONG CHOI ◽  
YOUNG-JAI PARK
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Minkowski Space ◽  
Event Horizon ◽  
Free Fall ◽  
Flat Space ◽  
Space Time ◽  
Local Temperature ◽  
Static Black Hole ◽  
Fall Temperature

We use the global embedding Minkowski space geometries of a (3+1)-dimensional curved Reissner–Nordström (RN)–AdS black hole space–time into a (5+2)-dimensional flat space–time to define a proper local temperature, which remains finite at the event horizon, for freely falling observers outside a static black hole. Our extended results include the known limiting cases of the RN, Schwarzschild–AdS and Schwarzschild black holes.

scholarly journals ENERGY EXTRACTION FROM GRAVITATIONAL COLLAPSE TO STATIC BLACK HOLES

2003 ◽  
Vol 12 (01) ◽  
pp. 121-127 ◽  
Author(s):  
REMO RUFFINI ◽  
LUCA VITAGLIANO
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Extraction Process ◽  
Maximum Efficiency ◽  
Energy Extraction ◽  
Mass Energy ◽  
Classical Level ◽  
Static Black Hole ◽  
Exact Analytic Expression ◽  
Analytic Expression

The mass-energy formula of black holes implies that up to 50% of the energy can be extracted from a static black hole. Such a result is reexamined using the recently established analytic formulas for the collapse of a shell and the expression for the irreducible mass of a static black hole. It is shown that the efficiency of energy extraction process during the formation of the black hole is linked in an essential way to the gravitational binding energy, the formation of the horizon and the reduction of the kinetic energy of implosion. Here a maximum efficiency of 50% in the extraction of the mass energy is shown to be generally attainable in the collapse of a spherically symmetric shell: surprisingly this result holds as well in the two limiting cases of the Schwarzschild and extreme Reissner–Nordström space–times. Moreover, the analytic expression recently found for the implosion of a spherical shell to an already formed black hole leads to a new exact analytic expression for the energy extraction which results in an efficiency strictly less than 100% for any physical implementable process. There appears to be no incompatibility between General Relativity and Thermodynamics at this classical level.

scholarly journals LUKEWARM BLACK HOLES IN QUADRATIC GRAVITY

2011 ◽  
Vol 26 (14) ◽  
pp. 999-1007 ◽  
Author(s):  
JERZY MATYJASEK ◽  
KATARZYNA ZWIERZCHOWSKA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Fourth Order ◽  
Spherically Symmetric ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Quadratic Gravity ◽  
De Sitter Universe ◽  
Electrically Charged

Perturbative solutions to the fourth-order gravity describing spherically-symmetric, static and electrically charged black hole in an asymptotically de Sitter universe is constructed and discussed. Special emphasis is put on the lukewarm configurations, in which the temperature of the event horizon equals the temperature of the cosmological horizon.

Sign in / Sign up

Export Citation Format

Share Document