scholarly journals BLACK HOLE FORMATION IN BIDIMENSIONAL DILATON GRAVITY COUPLED TO SCALAR MATTER SYSTEMS

1999 ◽  
Vol 14 (39) ◽  
pp. 2687-2694 ◽  
Author(s):  
M. ALVES ◽  
D. BAZEIA ◽  
V. B. BEZERRA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Fields ◽  
The Other ◽  
Gravity Models ◽  
Fourth Power ◽  
Dilaton Gravity ◽  
Hole Formation ◽  
Scalar Matter ◽  
Matter Fields

This work deals with the formation of black hole in bidimensional dilaton gravity coupled to scalar matter fields. We investigate two scalar matter systems, one described by a sixth power potential and the other defined with two scalar fields containing up to the fourth power in the fields. The topological solutions that appear in these cases allow the formation of black holes in the corresponding dilaton gravity models.

scholarly journals Perturbative and nonperturbative quasinormal modes of 4D Einstein–Gauss–Bonnet black holes

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Almendra Aragón ◽  
Ramón Bécar ◽  
P. A. González ◽  
Yerko Vásquez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Imaginary Part ◽  
Quasinormal Modes ◽  
Scalar Fields ◽  
The Other ◽  
Coupling Constant ◽  
De Sitter ◽  
Other Hand

Abstract We study the propagation of probe scalar fields in the background of 4D Einstein–Gauss–Bonnet black holes with anti-de Sitter (AdS) asymptotics and calculate the quasinormal modes. Mainly, we show that the quasinormal spectrum consists of two different branches, a branch perturbative in the Gauss–Bonnet coupling constant $$\alpha $$α and another branch, nonperturbative in $$\alpha $$α. The perturbative branch consists of complex quasinormal frequencies that approximate the quasinormal frequencies of the Schwarzschild AdS black hole in the limit of a null coupling constant. On the other hand, the nonperturbative branch consists of purely imaginary frequencies and is characterized by the growth of the imaginary part when $$\alpha $$α decreases, diverging in the limit of null coupling constant; therefore they do not exist for the Schwarzschild AdS black hole. Also, we find that the imaginary part of the quasinormal frequencies is always negative for both branches; therefore, the propagation of scalar fields is stable in this background.

scholarly journals WEYL INVARIANCE AND SPURIOUS BLACK HOLES IN TWO-DIMENSIONAL DILATON GRAVITY

1994 ◽  
Vol 09 (27) ◽  
pp. 4811-4835 ◽  
Author(s):  
TAKANORI FUJIWARA ◽  
YUJI IGARASHI ◽  
JISUKE KUBO
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hawking Radiation ◽  
Gravity Models ◽  
Conformal Anomaly ◽  
Quantum Level ◽  
Two Dimensional ◽  
Dilaton Gravity ◽  
Matter Coupling ◽  
Weyl Invariance

In two-dimensional dilaton gravity theories, there may exist a global Weyl invariance which makes the black hole spurious. If the global invariance and the local Weyl invariance of the matter coupling are intact at the quantum level, there is no Hawking radiation. We explicitly verify the absence of anomalies in these symmetries for the model proposed by Callan, Giddings, Harvey and Strominger. The crucial observation is that the conformal anomaly can be cohomologically trivial and so not truly anomalous in such dilaton gravity models.

scholarly journals DISTORTED BLACK HOLES WITH CHARGE

2001 ◽  
Vol 10 (05) ◽  
pp. 691-709 ◽  
Author(s):  
STEPHEN FAIRHURST ◽  
BADRI KRISHNAN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Maxwell Equations ◽  
The Other ◽  
Charged Black Hole ◽  
Matter Fields ◽  
Black Hole Solutions

We present new solutions to the Einstein–Maxwell equations representing a class of charged distorted black holes. These solutions are static-axisymmetric and are generalizations of the distorted black hole solutions studied by Geroch and Hartle. Physically, they represent a charged black hole distorted by external matter fields. We discuss the zeroth and first law for these black holes. The first law is proved in two different forms, one motivated by the isolated horizon framework and the other using normalizations at infinity.

Covariant perturbations of Schwarzschild black holes in f(R) gravity

2016 ◽  
Vol 26 (06) ◽  
pp. 1750048 ◽  
Author(s):  
Anne Marie Nzioki ◽  
Rituparno Goswami ◽  
Peter K. S. Dunsby
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Wave Equations ◽  
Quasinormal Modes ◽  
The Other ◽  
Primordial Black Holes ◽  
Hole Formation ◽  
High Multipoles ◽  
Theories Of Gravity ◽  
Scalar Perturbations

We consider general perturbations of a Schwarzschild black holes in the context of [Formula: see text] gravity. A reduced set of frame independent master variables are determined, which obey two closed wave equations — one for the transverse, trace-free, tensor perturbations and the other for the additional scalar degree of freedom which characterize fourth-order theories of gravity. We show that for the tensor modes, the underlying dynamics in [Formula: see text] gravity is governed by a modified Regge–Wheeler tensor which obeys the same Regge–Wheeler equation as in General Relativity (GR). We find that the possible sources of scalar quasinormal modes (QNMs) that follow from scalar perturbations for the lower multipoles result from primordial black holes, while higher mass, stellar black holes are associated with extremely high multipoles, which can only be produced in the first stage of black hole formation. Since scalar quasinormal modes are short ranged, this scenario makes their detection beyond the range of current experiments.

Thermodynamics of new black hole solutions in the Einstein–Maxwell-dilaton gravity

2018 ◽  
Vol 27 (07) ◽  
pp. 1850073 ◽  
Author(s):  
M. Dehghani
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Fields ◽  
Dilaton Gravity ◽  
Field Equations ◽  
Two Phase ◽  
Transition Analysis ◽  
Coupled Equations ◽  
Scalar Field Equations ◽  
Black Hole Solutions

In the present work, thermodynamics of the new black hole solutions to the four-dimensional Einstein–Maxwell-dilaton gravity theory have been studied. The dilaton potential, as the solution to the scalar field equations, has been constructed out by a linear combination of three Liouville-type potentials. Three new classes of charged dilatonic black hole solutions, as the exact solutions to the coupled equations of gravitational, electromagnetic and scalar fields, have been introduced. The conserved charge and mass of the new black holes have been calculated by utilizing Gauss's electric law and Abbott–Deser mass proposal, respectively. Also, the temperature, entropy and the electric potential of these new classes of charged dilatonic black holes have been calculated, making use of the geometrical approaches. Through a Smarr-type mass formula, the intensive parameters of the black holes have been calculated and validity of the first law of black hole thermodynamics has been confirmed. A thermal stability or phase transition analysis has been performed, making use of the canonical ensemble method. The heat capacity of the new black holes has been calculated and the points of type one- and type two-phase transitions as well as the ranges at which the new charged dilatonic black holes are locally stable have been determined, precisely.

scholarly journals BLACK HOLES IN TWO-DIMENSIONAL DILATON GRAVITY AND NONLINEAR KLEIN-GORDON SOLITON

1995 ◽  
Vol 10 (32) ◽  
pp. 4681-4687 ◽  
Author(s):  
HYEON-MIN JOHNG ◽  
HAK-SOO SHIN ◽  
KWANG-SUP SOH
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Classical Solution ◽  
Matter Field ◽  
Two Dimensional ◽  
Dilaton Gravity ◽  
Hole Formation ◽  
Klein Gordon ◽  
Quartic Interaction ◽  
Interaction Term

Two-dimensional dilaton gravity coupled to a Klein-Gordon matter field with a quartic interaction term is considered. The theory has a classical solution which exhibits black hole formation by a soliton. The geometry of a black hole induced by a soliton is investigated.

scholarly journals Feeding and feedback from little monsters: AGN in dwarf galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 238-242
Author(s):  
Mar Mezcua
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Early Universe ◽  
Dwarf Galaxies ◽  
Scaling Relations ◽  
Strong Impact ◽  
Hole Formation ◽  
Intermediate Mass ◽  
Black Hole Formation ◽  
Low Mass

AbstractDetecting the seed black holes from which quasars formed is extremely challenging; however, those seeds that did not grow into supermassive should be found as intermediate-mass black holes (IMBHs) of 100 – 105 M⊙ in local dwarf galaxies. The use of deep multiwavelength surveys has revealed that a population of actively accreting IMBHs (low-mass AGN) exists in dwarf galaxies at least out to z ˜3. The black hole occupation fraction of these galaxies suggests that the early Universe seed black holes formed from direct collapse of gas, which is reinforced by the possible flattening of the black hole-galaxy scaling relations at the low-mass end. This scenario is however challenged by the finding that AGN feedback can have a strong impact on dwarf galaxies, which implies that low-mass AGN in dwarf galaxies might not be the untouched relics of the early seed black holes. This has important implications for seed black hole formation models.

scholarly journals THE VIRTUAL BLACK HOLE IN 2D QUANTUM GRAVITY AND ITS RELEVANCE FOR THE S-MATRIX

2002 ◽  
Vol 17 (06n07) ◽  
pp. 989-992 ◽  
Author(s):  
DANIEL GRUMILLER
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Wave Scattering ◽  
Black Hole Mass ◽  
Hole Formation ◽  
S Wave ◽  
Scalar Matter ◽  
S Matrix ◽  
Tree Vertex ◽  
Classical Mechanism

As shown recently 2d quantum gravity theories — including spherically reduced Einstein-gravity — after an exact path integral of its geometric part can be treated perturbatively in the loops of (scalar) matter. Obviously the classical mechanism of black hole formation should be contained in the tree approximation of the theory. This is shown to be the case for the scattering of two scalars through an intermediate state which by its effective black hole mass is identified as a "virtual black hole". We discuss the lowest order tree vertex for minimally and non-minimally coupled scalars and find a non-trivial finite S-matrix for gravitational s-wave scattering in the latter case.

scholarly journals Thermodynamics of black holes in Rastall gravity

2018 ◽  
Vol 27 (07) ◽  
pp. 1850069 ◽  
Author(s):  
Iarley P. Lobo ◽  
H. Moradpour ◽  
J. P. Morais Graça ◽  
I. G. Salako
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
General Relativity ◽  
Black Hole ◽  
Momentum Conservation ◽  
Thermodynamic Quantities ◽  
Horizon Radius ◽  
Thermodynamics Of Black Holes ◽  
Matter Fields ◽  
Energy Momentum Conservation

A promising theory in modifying general relativity (GR) by violating the ordinary energy–momentum conservation law in curved spacetime is the Rastall theory of gravity. In this theory, geometry and matter fields are coupled to each other in a nonminimal way. Here, we study thermodynamic properties of some black hole (BH) solutions in this framework, and compare our results with those of GR. We demonstrate how the presence of these matter sources amplifies the effects caused by the Rastall parameter in thermodynamic quantities. Our investigation also shows that BHs with radius smaller than a certain amount ([Formula: see text]) have negative heat capacity in the Rastall framework. In fact, it is a lower bound for the possible values of horizon radius satisfied by the stable BHs.

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.

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