scholarly journals Making near-extremal wormholes traversable

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Seamus Fallows ◽  
Simon F. Ross
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Instability Threshold ◽  
Traversable Wormhole ◽  
Amount Of Information ◽  
Extremal Limit

Abstract We construct a traversable wormhole from a charged AdS black hole by adding a coupling between the two boundary theories. We investigate how the effect of this deformation behaves in the extremal limit of the black hole. The black holes have finite entropy but an infinitely long throat in the extremal limit. We argue that it is still possible to make the throat traversable even in the extremal limit, but this requires either tuning the field for which we add a boundary coupling close to an instability threshold or scaling the strength of the coupling inversely with the temperature. In the latter case we show that the amount of information that can be sent through the wormhole scales with the entropy.

scholarly journals Seeking connections between wormholes, gravastars, and black holes via noncommutative geometry

2019 ◽  
Vol 35 (09) ◽  
pp. 2050059
Author(s):  
Peter K. F. Kuhfittig ◽  
Vance D. Gladney
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Energy ◽  
String Theory ◽  
Noncommutative Geometry ◽  
Thin Shell ◽  
Traversable Wormhole ◽  
Thin Shell Wormholes ◽  
Theoretical Construction

Noncommutative geometry, an offshoot of string theory, replaces point-like objects by smeared objects. The resulting uncertainty may cause a black hole to be observationally indistinguishable from a traversable wormhole, while the latter, in turn, may become observationally indistinguishable from a gravastar. The same noncommutative-geometry background allows the theoretical construction of thin-shell wormholes from gravastars and may even serve as a model for dark energy.

scholarly journals Traversable Wormholes, Regular Black Holes, and Black-Bounces

2021 ◽  
Author(s):  
◽  
Alexander Simpson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Einstein Equations ◽  
Time Dependent ◽  
Alternative Theories Of Gravity ◽  
Regular Black Hole ◽  
Traversable Wormhole ◽  
Regular Black Holes ◽  
Traversable Wormholes

<p>Various spacetime candidates for traversable wormholes, regular black holes, and ‘black-bounces’ are presented and thoroughly explored in the context of the gravitational theory of general relativity. All candidate spacetimes belong to the mathematically simple class of spherically symmetric geometries; the majority are static (time-independent as well as nonrotational), with a single dynamical (time-dependent) geometry explored. To the extent possible, the candidates are presented through the use of a global coordinate patch – some of the prior literature (especially concerning traversable wormholes) has often proposed coordinate systems for desirable solutions to the Einstein equations requiring a multi-patch atlas. The most interesting cases include the so-called ‘exponential metric’ – well-favoured by proponents of alternative theories of gravity but which actually has a standard classical interpretation, and the ‘black-bounce’ to traversable wormhole case – where a metric is explored which represents either a traversable wormhole or a regular black hole, depending on the value of the newly introduced scalar parameter a. This notion of ‘blackbounce’ is defined as the case where the spherical boundary of a regular black hole forces one to travel towards a one-way traversable ‘bounce’ into a future reincarnation of our own universe. The metric of interest is then explored further in the context of a time-dependent spacetime, where the line element is rephrased with a Vaidya-like time-dependence imposed on the mass of the object, and in terms of outgoing/ingoing EddingtonFinkelstein coordinates. Analysing these candidate spacetimes extends the pre-existing discussion concerning the viability of non-singular black hole solutions in the context of general relativity, as well as contributing to the dialogue on whether an arbitrarily advanced civilization would be able to construct a traversable wormhole.</p>

scholarly journals S-DUALITY AND THE ENTROPY OF BLACK HOLES IN HETEROTIC STRING THEORY

1996 ◽  
Vol 11 (39n40) ◽  
pp. 3103-3111 ◽  
Author(s):  
AMIT GHOSH ◽  
JNANADEVA MAHARANA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Partition Function ◽  
Heterotic String ◽  
Heterotic String Theory ◽  
Charged Black Holes ◽  
Duality Transformations ◽  
Extremal Limit ◽  
Electrically Charged ◽  
Black Hole Solutions

Four-dimensional heterotic string effective action is known to admit non-rotating electrically and magnetically charged black hole solutions. The partition function and entropy is computed for electrically charged black holes and is vanishing in some extremal limit. For the magnetically charged black holes the entropy is also argued to be vanishing in the same extremal limit when these black hole solutions are related by S-duality transformations.

scholarly journals Extremal charged Vaidya and its near horizon geometry

2017 ◽  
Vol 26 (04) ◽  
pp. 1750036
Author(s):  
S. Sadeghian ◽  
A. Shafiekhani
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Solution ◽  
Spherically Symmetric ◽  
Nonstationary Solution ◽  
Vaidya Black Hole ◽  
Extremal Limit ◽  
Horizon Geometry ◽  
Extremal Black Holes

Recently [Formula: see text]-dimensional spherically symmetric charged Vaidya black hole solution has been constructed. We observe that this nonstationary solution admits extremal limit and study its near horizon geometry. We show that the symmetry of the near horizon geometry is [Formula: see text]. Our analysis shows that the theorems for the near horizon geometry of stationary extremal black holes, may be extended to nonstationary cases.

scholarly journals Remarks on holographic models of the Kerr-AdS5 geometry

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Julián Barragán Amado ◽  
Bruno Carneiro da Cunha ◽  
Elisabetta Pallante
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Low Temperatures ◽  
Quasinormal Modes ◽  
Temperature Limit ◽  
Conformal Blocks ◽  
Small Black Hole ◽  
Intermediate States ◽  
Extremal Limit ◽  
Scalar Perturbations

Abstract We study the low-temperature limit of scalar perturbations of the Kerr-AdS5 black-hole for generic rotational parameters. We motivate the study by considering real-time holography of small black hole backgrounds. Using the isomonodromic technique, we show that corrections to the extremal limit can be encoded in the monodromy parameters of the Painlevé V transcendent, whose expansion is given in terms of irregular chiral conformal blocks. After discussing the contribution of the intermediate states to the quasinormal modes, we perform a numerical analysis of the low-lying frequencies. We find that the fundamental mode is perturbatively stable at low temperatures for small black holes and that excited perturbations are superradiant, as expected from thermodynamical considerations. We close by considering the holographic interpretation of the unstable modes and the decaying process.

scholarly journals Squashed black holes at large D

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Ryotaku Suzuki ◽  
Shinya Tomizawa
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Static Solution ◽  
Flow Equation ◽  
Effective Theory ◽  
Theory Approach ◽  
First Order ◽  
Extremal Limit ◽  
Horizon Geometry ◽  
Kaluza Klein

Abstract Using the large D effective theory approach, we construct a static solution of non-extremal and squashed black holes with/without an electric charge, which describes a spherical black hole in a Kaluza-Klein spacetime with a compactified dimension. The asymptotic background with a compactified dimension and near-horizon geometry are analytically solved by the 1/D expansion. Particularly, our work demonstrates that the large D limit can be applied to solve the non-trivial background with a compactified direction, which leads to a first-order flow equation. Moreover, we show that the extremal limit consistently reproduces the known extremal result.

scholarly journals How black holes store information in high-order correlations

2020 ◽  
Vol 29 (14) ◽  
pp. 2043011
Author(s):  
Charis Anastopoulos ◽  
Konstantina Savvidou
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Gravity ◽  
Hawking Radiation ◽  
High Order ◽  
Black Hole Horizon ◽  
Quantum Fields ◽  
Amount Of Information ◽  
Key Aspects

We explain how Hawking radiation stores significant amount of information in high-order correlations of quantum fields. This information can be retrieved by multi-time measurements on the quantum fields close to the black hole horizon. This result requires no assumptions about quantum gravity, it takes into account the differences between Gibbs’s and Boltzmann’s accounts of thermodynamics, and it clarifies misconceptions about key aspects of Hawking radiation and about informational notions in QFT.

Information loss in black holes due to transition point

2019 ◽  
Vol 16 (02) ◽  
pp. 1950026
Author(s):  
Alireza Sepehri ◽  
Richard Pincak ◽  
Tooraj Ghaffary
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hawking Radiation ◽  
Transition Point ◽  
Information Loss ◽  
Total Entropy ◽  
Amount Of Information ◽  
Theoretical Question

An interesting theoretical question is the probability of information loss in the black hole due to the transition point. The presented study is an attempt to investigate this subject. When the black hole is exhausted due to Hawking radiation, the entropy carried away by all emissions and string ball is not equal to the entropy in the original black hole. We conclude that the total entropy is not conserved due to the transition point. This means that some information is lost at the corresponding point. Using the Gottesman and Preskill method, the amount of information loss in the black hole at the correspondence point is obtained.

ON THE QUANTIZATION OF CHARGED BLACK HOLES

1998 ◽  
Vol 07 (04) ◽  
pp. 521-534 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Apparent Horizon ◽  
Hamiltonian Formalism ◽  
Back Reaction ◽  
Cauchy Horizon ◽  
Electron Positron ◽  
Extremal Limit ◽  
Electron Positron Pair ◽  
Constant Charge

The Wheeler–DeWitt equation for the wave function Ψ of the Schwarzschild black hole has been derived by Tomimatsu in the form of a Schrödinger equation, valid on the apparent horizon, using the two-dimensional Hamiltonian formalism of Hajicek and the radiating Vaidya metric. Here, the analysis is generalized to the Reissner–Nordström black hole. At constant charge Q, the evaporation rate is calculated from the solution for Ψ to be [Formula: see text], where k is a constant and [Formula: see text] are the radii of the outer event horizon and inner Cauchy horizon. In the extremal limit M → Q, however, the Hawking temperature [Formula: see text] tends to zero, suggesting, when the back reaction is taken into account, that the evaporation cannot occur this way and in agreement with the known discharging process of the hole via the Schwinger electron–positron pair-production mechanism. The more general charged dilaton black holes obtained from the theory L4 = [R4 - 2 (∇ Φ)2 - e-2aΦF2 ]/16π are also discussed, and it is explained why this quantization procedure cannot be applied when a is non-zero.

scholarly journals Traversable Wormholes, Regular Black Holes, and Black-Bounces

2021 ◽  
Author(s):  
◽  
Alexander Simpson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Einstein Equations ◽  
Time Dependent ◽  
Alternative Theories Of Gravity ◽  
Regular Black Hole ◽  
Traversable Wormhole ◽  
Regular Black Holes ◽  
Traversable Wormholes

<p>Various spacetime candidates for traversable wormholes, regular black holes, and ‘black-bounces’ are presented and thoroughly explored in the context of the gravitational theory of general relativity. All candidate spacetimes belong to the mathematically simple class of spherically symmetric geometries; the majority are static (time-independent as well as nonrotational), with a single dynamical (time-dependent) geometry explored. To the extent possible, the candidates are presented through the use of a global coordinate patch – some of the prior literature (especially concerning traversable wormholes) has often proposed coordinate systems for desirable solutions to the Einstein equations requiring a multi-patch atlas. The most interesting cases include the so-called ‘exponential metric’ – well-favoured by proponents of alternative theories of gravity but which actually has a standard classical interpretation, and the ‘black-bounce’ to traversable wormhole case – where a metric is explored which represents either a traversable wormhole or a regular black hole, depending on the value of the newly introduced scalar parameter a. This notion of ‘blackbounce’ is defined as the case where the spherical boundary of a regular black hole forces one to travel towards a one-way traversable ‘bounce’ into a future reincarnation of our own universe. The metric of interest is then explored further in the context of a time-dependent spacetime, where the line element is rephrased with a Vaidya-like time-dependence imposed on the mass of the object, and in terms of outgoing/ingoing EddingtonFinkelstein coordinates. Analysing these candidate spacetimes extends the pre-existing discussion concerning the viability of non-singular black hole solutions in the context of general relativity, as well as contributing to the dialogue on whether an arbitrarily advanced civilization would be able to construct a traversable wormhole.</p>

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