scholarly journals Apparent horizons of anN-black-hole system in a space-time with a cosmological constant

1993 ◽  
Vol 47 (8) ◽  
pp. 3203-3213 ◽  
Author(s):  
Ken-ichi Nakao ◽  
Kazuhiro Yamamoto ◽  
Kei-ichi Maeda
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Space Time ◽  
Apparent Horizons

scholarly journals Entropic gravity from noncommutative black holes

2017 ◽  
Vol 15 (01) ◽  
pp. 1850004 ◽  
Author(s):  
Rafael C. Nunes ◽  
Hooman Moradpour ◽  
Edésio M. Barboza ◽  
Everton M. C. Abreu ◽  
Jorge Ananias Neto
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Cosmological Constant ◽  
Black Hole Entropy ◽  
Space Time ◽  
Isotropic Universe ◽  
Entropic Gravity ◽  
The Universe

In this paper, we investigated the effects of a noncommutative (NC) space-time on the dynamics of the Universe. We generalize the black hole entropy for a NC black hole. Then, using the entropic gravity formalism, we will show that the noncommutativity changes the strength of the gravitational field. By applying this result to a homogeneous and isotropic Universe containing nonrelativistic matter and a cosmological constant, we show that the modified scenario by the noncommutativity of the space-time is a better fit to the obtained data than the standard one at 68% CL.

scholarly journals SPECTROSCOPY OF AN AdS REISSNER–NORDSTRØM BLACK HOLE

2006 ◽  
Vol 15 (03) ◽  
pp. 439-457 ◽  
Author(s):  
CLAUDIO DAPPIAGGI ◽  
SIMONA RASCHI
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Flat Space ◽  
Space Time ◽  
Charged Black Hole ◽  
Area Spectrum ◽  
Asymptotically Flat ◽  
Negative Cosmological Constant

In the framework of black hole spectroscopy, we extend the results obtained for a charged black hole in an asymptotically flat space–time to the scenario with non-vanishing negative cosmological constant. In particular, exploiting Hamiltonian techniques, we construct the area spectrum for an AdS Reissner–Nordstrøm black hole.

The apparent horizons of Einstein-Rosen bridges in the space-time with a cosmological constant

1993 ◽  
Vol 37 ◽  
pp. 453-456
Author(s):  
Ken-ichi Nakao ◽  
Kazuhiro Yamamoto ◽  
Kei-ichi Maeda
Keyword(s):  
Cosmological Constant ◽  
Space Time ◽  
Apparent Horizons

scholarly journals SPACE TIME FOAM

2002 ◽  
Vol 17 (06n07) ◽  
pp. 829-832 ◽  
Author(s):  
REMO GARATTINI
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Ground State ◽  
Casimir Energy ◽  
Space Time ◽  
De Sitter ◽  
Schwarzschild Black Hole ◽  
Positive Cosmological Constant ◽  
Hole Transition

In the context of a model of space-time foam, made by N wormholes we discuss the possibility of having a foam formed by different configurations. An equivalence between Schwarzschild and Schwarzschild-Anti-de Sitter wormholes in terms of Casimir energy is shown. An argument to discriminate which configuration could represent a foamy vacuum coming from Schwarzschild black hole transition frequencies is used. The case of a positive cosmological constant is also discussed. Finally, a discussion involving charged wormholes leads to the conclusion that they cannot be used to represent a ground state of the foamy type.

GRAVITATIONAL PERFECT FLUID COLLAPSE WITH COSMOLOGICAL CONSTANT

2007 ◽  
Vol 22 (20) ◽  
pp. 1493-1502 ◽  
Author(s):  
M. SHARIF ◽  
ZAHID AHMAD
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Perfect Fluid ◽  
Physical Significance ◽  
Spherically Symmetric ◽  
Positive Cosmological Constant ◽  
Matching Conditions ◽  
Apparent Horizons ◽  
Dust Case

In this paper, the effect of a positive cosmological constant on spherically symmetric collapse with perfect fluid has been investigated. The matching conditions between static exterior and non-static interior spacetimes are given in the presence of a cosmological constant. We also study the apparent horizons and their physical significance. It is concluded that the cosmological constant slows down the collapse of matter and hence limit the size of the black hole. This analysis gives the generalization of the dust case to the perfect fluid. We recover the results of the dust case for p = 0.

scholarly journals BLACK HOLE EVAPORATION BASED UPON A q-DEFORMATION DESCRIPTION

2005 ◽  
Vol 20 (26) ◽  
pp. 6039-6049 ◽  
Author(s):  
XIN ZHANG
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Radiation Spectrum ◽  
Correlation Effect ◽  
Space Time ◽  
Noncommutative Space ◽  
Schwarzschild Black Hole ◽  
Black Hole Evaporation ◽  
Starting Point ◽  
New Distribution

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to make an attempt to consider the space–time noncommutativity in the vicinity of black hole horizon. We use a trick that all the space–time noncommutative effects are ascribed to the modification of the behavior of the radiation field of black hole and a kind of q-deformed degrees of freedom are postulated to mimic the radiation particles that live on the noncommutative space–time, meanwhile the background metric is preserved as usual. We calculate the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectrum evidently. The result indicates that some correlation effect will be introduced to the system if the noncommutativity is taken into account. In addition, an infrared cutoff of the spectrum is the prediction of the model.

scholarly journals Does Hawking predict the correct temperature of a black-hole?

2020 ◽  
Vol 29 (1) ◽  
pp. 56-58
Author(s):  
Kapil Chandra
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Extreme Temperature ◽  
Extreme Value ◽  
Radiation Temperature ◽  
Calculated Temperature ◽  
Actual Temperature

AbstractIn our study of the validity of Hawking’s predicted radiation temperature of a black-hole, we found that the calculated temperature is another form of Zeldovich’s expression for the cosmological constant. We reasoned that as Zeldovich predicted the extreme value of cosmological constant thus Hawking might have also predicted an extreme temperature. However, the actual temperature might be something different. This result implies that all predictions based on Hawking’s radiation temperature might be incorrect.

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