scholarly journals COSMIC BLACK HOLES

2003 ◽  
Vol 12 (09) ◽  
pp. 1699-1704 ◽  
Author(s):  
EUN-JOO AHN ◽  
MARCO CAVAGLIÀ
Keyword(s):  
Black Holes ◽  
Quantum Gravity ◽  
Physical Properties ◽  
Early Universe ◽  
High Energy ◽  
Natural Setting ◽  
Present Epoch ◽  
The Past ◽  
Gravitational Theories ◽  
The Creation

Production of high-energy gravitational objects is a common feature of gravitational theories. The primordial universe is a natural setting for the creation of black holes and other nonperturbative gravitational entities. Cosmic black holes can be used to probe physical properties of the very early universe which would usually require the knowledge of the theory of quantum gravity. They may be the only tool to explore thermalization of the early universe. Whereas the creation of cosmic black holes was active in the past, it seems to be negligible at the present epoch.

scholarly journals ACCELERATION AND DECELERATION IN THE CURVATURE-INDUCED PHANTOM MODEL OF THE LATE AND FUTURE UNIVERSE: COSMIC COLLAPSE AND ITS QUANTUM ESCAPE

2009 ◽  
Vol 18 (05) ◽  
pp. 865-887
Author(s):  
S. K. SRIVASTAVA ◽  
J. DUTTA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Early Universe ◽  
High Energy ◽  
High Energy Density ◽  
Energy Models ◽  
Acceleration And Deceleration ◽  
The Universe

In this paper, the cosmology of the late and future universe is obtained from f(R) gravity with nonlinear curvature terms R2 and R3 (R is the Ricci scalar curvature). It is different from f(R) dark energy models where nonlinear curvature terms are taken as a gravitational alternative to dark energy. In the present model, neither linear nor nonlinear curvature terms are taken as dark energy. Rather, dark energy terms are induced by curvature terms and appear in the Friedmann equation derived from f(R) gravitational equations. This approach has an advantage over f(R) dark energy models in three ways: (i) results are consistent with WMAP observations, (ii) dark matter is produced from the gravitational sector and (iii) the universe expands as ~ t2/3 during dominance of the curvature-induced dark matter, which is consistent with the standard cosmology. Curvature-induced dark energy mimics phantom and causes late acceleration. It is found that transition from matter-driven deceleration to acceleration takes place at the redshift 0.36 at time 0.59 t0 (t0 is the present age of the universe). Different phases of this model, including acceleration and deceleration during the phantom phase, are investigated. It is found that expansion of the universe will stop at the age of 3.87 t0 + 694.4 kyr. After this epoch, the universe will contract and collapse by the time of 336.87 t0 + 694.4 kyr. Further, it is shown that cosmic collapse obtained from classical mechanics can be avoided by making quantum gravity corrections relevant near the collapse time due to extremely high energy density and large curvature analogous to the state of the very early universe. Interestingly, the cosmological constant is also induced here; it is extremely small in the classical domain but becomes very high in the quantum domain. This result explains the largeness of the cosmological constant in the early universe due to quantum gravity effects during this era and its very low value in the present universe due to negligible quantum effect in the late universe.

scholarly journals Beyond General Relativity: Models for Quantum Gravity, Loop Quantum Cosmology and Black Holes

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 232
Author(s):  
Nick E. Mavromatos
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Quantum Gravity ◽  
Quantum Cosmology ◽  
Precision Measurements ◽  
Loop Quantum Cosmology ◽  
The Past

In the past two decades, we have witnessed extraordinary progress in precision measurements in cosmology [...]

MICRO BLACK HOLES IN THE LABORATORY AND OTHER EXPERIMENTAL SIGNATURES OF QUANTUM GRAVITY

2011 ◽  
Vol 20 (supp01) ◽  
pp. 85-93
Author(s):  
MARCUS BLEICHER ◽  
MARTIN SPRENGER
Keyword(s):  
Experimental Data ◽  
Black Holes ◽  
Quantum Gravity ◽  
High Precision ◽  
Planck Scale ◽  
High Energy ◽  
Precision Measurements ◽  
Gyroscopic Moment ◽  
Gravity Effects ◽  
Comparison With Experimental Data

We investigate the possibility of quantum gravity effects setting in at much lower energies than the Planck scale. In particular, we study the formation and detection of microscopic black holes at the LHC as well as precision measurements of the gyroscopic moment of the muon and neutrino oscillations. We find that quantum gravity effects lead to observable signatures both in high energy and high precision scenarios. Comparison with experimental data allows us to constrain the parameters of the models.

scholarly journals NONSINGULAR COSMOLOGIES FROM BRANES

2004 ◽  
Vol 19 (04) ◽  
pp. 557-574 ◽  
Author(s):  
ANINDYA BISWAS ◽  
SUDIPTA MUKHERJI ◽  
SHESANSU SEKHAR PAL
Keyword(s):  
Black Holes ◽  
Wave Function ◽  
Quantum Gravity ◽  
De Sitter ◽  
Superspace Formalism ◽  
The Creation ◽  
Bulk Parameters

We analyze possible cosmological scenarios on a brane where the brane acts as a dynamical boundary of various black holes with anti-de Sitter or de Sitter asymptotic. In many cases, the brane is found to describe the completely nonsingular universe. In some cases, quantum gravity era of the brane-universe can also be avoided by properly tuning bulk parameters. We further discuss the creation of a brane-universe by studying its wave function. This is done by employing Wheeler–De Witt equation in the mini superspace formalism.

scholarly journals Microquasars as Sources of High Energy Phenomena

2003 ◽  
Vol 214 ◽  
pp. 201-210 ◽  
Author(s):  
I. F. Mirabel
Keyword(s):  
Black Holes ◽  
Cosmic Rays ◽  
Physical Properties ◽  
Gamma Rays ◽  
High Energy ◽  
Common Phenomenon ◽  
Relativistic Jets ◽  
Massive Black Holes ◽  
X Ray ◽  
X Ray Binaries

Relativistic outflows are a common phenomenon in accreting black holes. Despite the enormous differences in scale, accreting stellar-mass black holes (X-ray binaries, collapsars) and super-massive black holes produce jets with analogous physical properties. Here I review microquasars as sources of relativistic jets, gamma-rays, cosmic rays, and high energy neutrinos.

scholarly journals Symmetry reduced loop quantum gravity: A bird’s eye view

2016 ◽  
Vol 25 (08) ◽  
pp. 1642010 ◽  
Author(s):  
Abhay Ashtekar
Keyword(s):  
Black Holes ◽  
Quantum Gravity ◽  
Early Universe ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Current Status ◽  
Loop Quantum Cosmology ◽  
Reduced Models ◽  
Quantum Aspects

This is a brief overview of the current status of symmetry reduced models in Loop Quantum Gravity. The goal is to provide an introduction to other more specialized and detailed reviews that follow. Since most of this work is motivated by the physics of the very early universe, I will focus primarily on Loop Quantum Cosmology and discuss quantum aspects of black holes only briefly.

scholarly journals QUANTUM NATURE OF BLACK HOLES

2004 ◽  
Vol 13 (10) ◽  
pp. 2299-2305 ◽  
Author(s):  
ADAM D. HELFER
Keyword(s):  
Black Holes ◽  
Quantum Gravity ◽  
Gravitational Collapse ◽  
Dominant Role ◽  
High Energy ◽  
Ultra High Energy ◽  
Quantum Fields ◽  
Vacuum Fluctuations ◽  
High Energies ◽  
Quantum Nature

I reconsider Hawking's analysis of the effects of gravitational collapse on quantum fields, taking into account interactions between the fields. The ultra-high energy vacuum fluctuations, which had been considered to be an awkward peripheral feature of the analysis, are shown to play a key role. By interactions, they can scatter particles to, or create pairs of particle at, ultra-high energies. The energies rapidly become so great that quantum gravity must play a dominant role. Thus the vicinities of black holes are essentially quantum-gravitational regimes.

scholarly journals Signatures of primordial black hole dark matter

2014 ◽  
Vol 29 (37) ◽  
pp. 1440005 ◽  
Author(s):  
K. M. Belotsky ◽  
A. E. Dmitriev ◽  
E. A. Esipova ◽  
V. A. Gani ◽  
A. V. Grobov ◽  
...  
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Symmetry Breaking ◽  
Early Universe ◽  
High Energy Physics ◽  
Gamma Ray ◽  
High Energy ◽  
Primordial Black Hole ◽  
Dominant Form ◽  
The Universe

The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. In the early Universe heavy metastable particles can dominate, leaving primordial black holes (PBHs) after their decay, as well as the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which massive black holes (BHs) and/or their clusters can originate. PBHs can be formed in such transitions within a narrow interval of masses about 1017 g and, avoiding severe observational constraints on PBHs, can be a candidate for the dominant form of dark matter. PBHs in this range of mass can give solution of the problem of reionization in the Universe at the redshift z~5–10. Clusters of massive PBHs can serve as a nonlinear seeds for galaxy formation, while PBHs evaporating in such clusters can provide an interesting interpretation for the observations of point-like gamma-ray sources. Analysis of possible PBH signatures represents a universal probe for super-high energy physics in the early Universe in studies of indirect effects of the dark matter.

The Scientific Value Of Research On Mirmukhsin Fikriy

2020 ◽  
Vol 2 (08) ◽  
pp. 583-589
Author(s):  
Umriniso Rahmatovna Turaeva
Keyword(s):  
Political Environment ◽  
Continuous Development ◽  
The Past ◽  
Works Of Art ◽  
Literary Heritage ◽  
History Of ◽  
The Creation ◽  
Scientific Value

The history of the Turkestan Jadid movement and the study of Jadid literature show that it has not been easy to study this subject. The socio-political environment of the time led to the blind reduction of the history of continuous development of Uzbek literature, artificial reduction of the literary heritage of the past on the basis of dogmatic thinking, neglect of the study of works of art and literary figures. As a result, the creation of literary figures of a certain period, no matter how important, remained unexplored.

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