scholarly journals Improved dynamics and gravitational collapse of tachyon field coupled with a barotropic fluid

2015 ◽  
Vol 24 (03) ◽  
pp. 1550025 ◽  
Author(s):  
João Marto ◽  
Yaser Tavakoli ◽  
Paulo Vargas Moniz
Keyword(s):  
Black Hole ◽  
Gravitational Collapse ◽  
Classical Model ◽  
Saddle Points ◽  
Tachyon Field ◽  
Naked Singularities ◽  
Barotropic Fluid ◽  
Gravity Effects ◽  
Present Context ◽  
General Relativistic

We consider a spherically symmetric gravitational collapse of a tachyon field with an inverse square potential, which is coupled with a barotropic fluid. By employing an holonomy correction imported from loop quantum cosmology (LQC), we analyze the dynamics of the collapse within a semiclassical description. Using a dynamical system approach, we find that the stable fixed points given by the standard general relativistic setting turn into saddle points in the present context. This provides a new dynamics in contrast to the black hole and naked singularities solutions appearing in the classical model. Our results suggest that classical singularities can be avoided by quantum gravity effects and are replaced by a bounce. By a thorough numerical studies we show that, depending on the barotropic parameter γ, there exists a class of solutions corresponding to either a fluid or a tachyon dominated regimes. Furthermore, for the case γ ~ 1, we find an interesting tracking behavior between the tachyon and the fluid leading to a dust-like collapse. In addition, we show that, there exists a threshold scale which determines when an outward energy flux emerges, as a nonsingular black hole is forming, at the corresponding collapse final stages.

SPHERICAL AND NON-SPHERICAL GRAVITATIONAL COLLAPSE IN HUSAIN SPACETIME

2005 ◽  
Vol 14 (05) ◽  
pp. 873-882 ◽  
Author(s):  
K. D. PATIL ◽  
U. S. THOOL
Keyword(s):  
Black Hole ◽  
Gravitational Collapse ◽  
Naked Singularities

We investigate the nature of singularities arising in Husain solution. We analyze both spherical and non-spherical gravitational collapse in Husain spacetime. An interesting feature that emerges is that gravitational collapse of spherical cosmological Husain solution leads to the formation of naked singularities, while non-spherical cosmological collapse proceeds to form a black hole. Further strength of naked singularities arising in these spacetimes has been analyzed. It is found that these naked singularities are strong in Tipler's sense.

Naked singularities and other features of self-similar general-relativistic gravitational collapse

1990 ◽  
Vol 42 (4) ◽  
pp. 1068-1090 ◽  
Author(s):  
Amos Ori ◽  
Tsvi Piran
Keyword(s):  
Gravitational Collapse ◽  
Naked Singularities ◽  
General Relativistic ◽  
Self Similar

scholarly journals RECENT DEVELOPMENTS IN GRAVITATIONAL COLLAPSE AND SPACETIME SINGULARITIES

2011 ◽  
Vol 20 (14) ◽  
pp. 2641-2729 ◽  
Author(s):  
PANKAJ S. JOSHI ◽  
DANIELE MALAFARINA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Collapse ◽  
Spacetime Singularities ◽  
Black Hole Physics ◽  
Naked Singularity ◽  
Theory Of Relativity ◽  
Quantum Theories ◽  
Naked Singularities ◽  
Astrophysical Objects

It is now known that when a massive star collapses under the force of its own gravity, the final fate of such a continual gravitational collapse will be either a black hole or a naked singularity under a wide variety of physically reasonable circumstances within the framework of general theory of relativity. The research of recent years has provided considerable clarity and insight on stellar collapse, black holes and the nature and structure of spacetime singularities. We discuss several of these developments here. There are also important fundamental questions that remain unanswered on the final fate of collapse of a massive matter cloud in gravitation theory, especially on naked singularities which are hypothetical astrophysical objects and on the nature of cosmic censorship hypothesis. These issues have key implications for our understanding on black hole physics today, its astrophysical applications, and for certain basic questions in cosmology and possible quantum theories of gravity. We consider these issues here and summarize recent results and current progress in these directions. The emerging astrophysical and observational perspectives and implications are discussed, with particular reference to the properties of accretion disks around black holes and naked singularities, which may provide characteristic signatures and could help distinguish these objects.

scholarly journals Gravitational collapse with tachyon field and barotropic fluid

2013 ◽  
Vol 45 (4) ◽  
pp. 819-844 ◽  
Author(s):  
Yaser Tavakoli ◽  
João Marto ◽  
Amir Hadi Ziaie ◽  
Paulo Vargas Moniz
Keyword(s):  
Gravitational Collapse ◽  
Tachyon Field ◽  
Barotropic Fluid

THE EFFECTS OF DIFFERENT PERTURBATIONS ON THE DYNAMICS OF THE ACCRETION DISK AROUND THE BLACK HOLE

2007 ◽  
Vol 22 (10) ◽  
pp. 1875-1898 ◽  
Author(s):  
ORHAN DÖNMEZ
Keyword(s):  
Shock Wave ◽  
Black Hole ◽  
Shock Waves ◽  
Accretion Disk ◽  
Periodic Oscillation ◽  
Single Star ◽  
Special Cases ◽  
Galactic Black Hole ◽  
General Relativistic ◽  
Armed Spiral

We investigate the special cases of the formation of shocks in the accretion disks around the nonrotating (Schwarzschild) black holes in cases where one or few stars perturb the disk. We model the structure of disk with a 2D fully general relativistic hydrodynamic code and investigate a variety of cases in which the stars interacting with the disk are captured at various locations. We have found the following results: (1) if the stars perturb the disk at nonsymmetric locations, a moving one-armed spiral shock wave is produced and it destroys the disk eventually; (2) if the disk is perturbed by a single star located close to the black hole, a standing shock wave is produced while the disk becomes an accretion tori; (3) if the disk is perturbed by stars at symmetric locations, moving two-armed spiral shock waves are produced while the disk reaches a steady state; (4) continuous injection of matter into the stable disk produces a standing shock wave behind the black hole. Our outcomes reinforce the view that different perturbations on the stable accretion disk carry out different types of shock waves which produce Quasi-Periodic Oscillation (QPO) phenomena in galactic black hole candidates and it is observed as a X-ray.

scholarly journals Influence of the geometric configuration of accretion flow on the black hole spin dependence of relativistic acoustic geometry

2018 ◽  
Vol 27 (03) ◽  
pp. 1850023 ◽  
Author(s):  
Pratik Tarafdar ◽  
Tapas K. Das
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Geometric Configuration ◽  
Surface Gravity ◽  
Linear Perturbation ◽  
Flow Profile ◽  
White Hole ◽  
Accretion Flow ◽  
Black Hole Spin ◽  
General Relativistic

Linear perturbation of general relativistic accretion of low angular momentum hydrodynamic fluid onto a Kerr black hole leads to the formation of curved acoustic geometry embedded within the background flow. Characteristic features of such sonic geometry depend on the black hole spin. Such dependence can be probed by studying the correlation of the acoustic surface gravity [Formula: see text] with the Kerr parameter [Formula: see text]. The [Formula: see text]–[Formula: see text] relationship further gets influenced by the geometric configuration of the accretion flow structure. In this work, such influence has been studied for multitransonic shocked accretion where linear perturbation of general relativistic flow profile leads to the formation of two analogue black hole-type horizons formed at the sonic points and one analogue white hole-type horizon which is formed at the shock location producing divergent acoustic surface gravity. Dependence of the [Formula: see text]–[Formula: see text] relationship on the geometric configuration has also been studied for monotransonic accretion, over the entire span of the Kerr parameter including retrograde flow. For accreting astrophysical black holes, the present work thus investigates how the salient features of the embedded relativistic sonic geometry may be determined not only by the background spacetime, but also by the flow configuration of the embedding matter.

ON MAGNETIC SELF-COLLIMATION OF RELATIVISTIC JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 689-694
Author(s):  
N. GLOBUS ◽  
V. CAYATTE ◽  
C. SAUTY
Keyword(s):  
Black Hole ◽  
Total Energy ◽  
Ideal Fluid ◽  
Polar Axis ◽  
Kerr Metric ◽  
Relativistic Jets ◽  
Simple Criterion ◽  
General Relativistic ◽  
Time Splitting ◽  
Relativistic Magnetohydrodynamics

We present a semi-analytical model using the equations of general relativistic magnetohydrodynamics (GRMHD) for jets emitted by a rotating black hole. We assume steady axisymmetric outflows of a relativistic ideal fluid in Kerr metrics. We express the conservation equations in the frame of the FIDucial Observer (FIDO or ZAMO) using a 3+1 space–time splitting. Calculating the total energy variation between a non-polar field line and the polar axis, we extend to the Kerr metric the simple criterion for the magnetic collimation of jets obtained for a nonrotating black hole by Meliani et al.10 We show that the black role rotation induced a more efficient magnetic collimation of the jet.

scholarly journals Rebounce and black hole formation in a gravitational collapse model with vanishing radial pressure

2007 ◽  
Vol 39 (6) ◽  
pp. 825-838 ◽  
Author(s):  
Ashutosh Mahajan ◽  
Pankaj S. Joshi
Keyword(s):  
Black Hole ◽  
Gravitational Collapse ◽  
Radial Pressure ◽  
Hole Formation ◽  
Black Hole Formation ◽  
Collapse Model

scholarly journals DIRECTLY OBSERVING ENTROPY ACCUMULATION ON THE HORIZON AND HOLOGRAPHY

2012 ◽  
Vol 21 (11) ◽  
pp. 1242010
Author(s):  
ARIEL EDERY ◽  
HUGUES BEAUCHESNE
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Gravitational Collapse ◽  
Spherical Symmetry ◽  
Proper Time ◽  
Horizon Area

Recent numerical simulations of gravitational collapse show that there exists a special foliation of the spacetime where matter and entropy accumulate directly on the inside of the horizon surface. In this foliation, the time coincides with the proper time of the asymptotic static observer (ASO) and for spherical symmetry, this corresponds to isotropic co-ordinates. In this gauge, the three-volume in the interior shrinks to zero and only the horizon area remains at the end of collapse. In a different foliation, matter and entropy accumulate in the volume. The entropy is however independent of the foliation. Black hole holography is therefore a mapping from an arbitrary foliation, where information resides in the volume, to the special ASO frame, where it resides directly on the horizon surface.

scholarly journals General Relativistic MHD Simulations of the Gravitational Collapse of a Rotating Star with Magnetic Field as a Model of Gamma-Ray Bursts

2004 ◽  
Vol 155 ◽  
pp. 387-388
Author(s):  
Yosuke Mizuno ◽  
Kazunari Shibata ◽  
Shoichi Yamada ◽  
Shinji Koide
Keyword(s):  
Magnetic Field ◽  
Gravitational Collapse ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Mhd Simulations ◽  
General Relativistic ◽  
Rotating Star
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