Gravitational collapse in f(R) theories of gravity with non-minimal coupling

2019 ◽  
Vol 34 (03) ◽  
pp. 1950025 ◽  
Author(s):  
H. Nazar ◽  
G. Abbas
Keyword(s):  
Perfect Fluid ◽  
Gravitational Collapse ◽  
Spherically Symmetric ◽  
Coupling Constant ◽  
Minimal Coupling ◽  
Apparent Horizons ◽  
Exterior Regions ◽  
Theories Of Gravity ◽  
Minimal Curvature ◽  
Zero Coupling

The purpose of this paper is to discuss the perfect fluid gravitational collapse in modified f(R) metric gravity theories with non-minimal curvature coupled to matter. For this inference, we investigate the effects on self-gravitating implosion with spherically symmetric non-static geometry in the presence of extra force [Formula: see text], that express the cosmic expansion with dark source constraints. Matching conditions are given in which we have taken the insertion of non-static interior and static exterior regions along with cosmological constant. We have investigated the apparent horizons with effective results and along with their physical interpretation. It is analyzed that the extra component of dark source material reduces the gravitating implosion, hence slowing the rate of collapse. This study also reflects the contribution towards the perfect fluid for the generalization in f(R) gravity with zero coupling constant [Formula: see text].

Charged perfect fluid gravitational collapse in f(R, T) gravity

2019 ◽  
Vol 34 (20) ◽  
pp. 1950153 ◽  
Author(s):  
G. Abbas ◽  
Riaz Ahmed
Keyword(s):  
Perfect Fluid ◽  
Gravitational Collapse ◽  
Coupling Parameter ◽  
Apparent Horizon ◽  
Momentum Tensor ◽  
Spherically Symmetric ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Apparent Horizons ◽  
Spherically Symmetric Metric

We explore the problem of charged perfect fluid spherically symmetric gravitational collapse in f(R, T) gravity (R is Ricci scalar and T is the trace of energy–momentum tensor). We have taken the interior boundary of a star as spherically symmetric metric filled with the charged perfect fluid. In order to study charged perfect fluid collapse, we have investigated the exact solutions of the Maxwell–Einstein field equations solutions using the most simplified form for f(R, T) model f(R, T) = R + 2[Formula: see text]T, where [Formula: see text] is model parameter. This study involves the effects of charge as well as coupling parameter on collapse of a star. We studied the nature of trapped surfaces, apparent horizon and singularity structure in detail. It has been found that singularity is formed earlier than the apparent horizons, so the end state of gravitational collapse in this case is black hole.

scholarly journals EFFECTS OF ELECTROMAGNETIC FIELD ON GRAVITATIONAL COLLAPSE

2009 ◽  
Vol 24 (31) ◽  
pp. 2551-2563 ◽  
Author(s):  
M. SHARIF ◽  
G. ABBAS
Keyword(s):  
Electromagnetic Field ◽  
Cosmological Constant ◽  
Perfect Fluid ◽  
Gravitational Collapse ◽  
Physical Significance ◽  
Spherically Symmetric ◽  
Junction Conditions ◽  
Positive Cosmological Constant ◽  
Symmetric Spacetimes ◽  
Apparent Horizons

In this paper, the effect of electromagnetic field has been investigated on the spherically symmetric gravitational collapse with the perfect fluid in the presence of positive cosmological constant. Junction conditions between the static exterior and non-static interior spherically symmetric spacetimes are discussed. We study the apparent horizons and their physical significance. It is found that electromagnetic field reduces the bound of cosmological constant by reducing the pressure and hence collapsing process is faster as compared to the perfect fluid case. This work gives the generalization of the perfect fluid case to the charged perfect fluid. Results for the perfect fluid case are recovered.

scholarly journals GRAVITATIONAL COLLAPSE OF SPHERICALLY SYMMETRIC PERFECT FLUID WITH KINEMATIC SELF-SIMILARITY

2002 ◽  
Vol 11 (02) ◽  
pp. 155-186 ◽  
Author(s):  
C. F. C. BRANDT ◽  
L.-M. LIN ◽  
J. F. VILLAS DA ROCHA ◽  
A. Z. WANG
Keyword(s):  
Black Holes ◽  
Perfect Fluid ◽  
Gravitational Collapse ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Self Similarity ◽  
Schwarzschild Solution ◽  
Naked Singularities

Analytic spherically symmetric solutions of the Einstein field equations coupled with a perfect fluid and with self-similarities of the zeroth, first and second kinds, found recently by Benoit and Coley [Class. Quantum Grav.15, 2397 (1998)], are studied, and found that some of them represent gravitational collapse. When the solutions have self-similarity of the first (homothetic) kind, some of the solutions may represent critical collapse but in the sense that now the "critical" solution separates the collapse that forms black holes from the collapse that forms naked singularities. The formation of such black holes always starts with a mass gap, although the "critical" solution has homothetic self-similarity. The solutions with self-similarity of the zeroth and second kinds seem irrelevant to critical collapse. Yet, it is also found that the de Sitter solution is a particular case of the solutions with self-similarity of the zeroth kind, and that the Schwarzschild solution is a particular case of the solutions with self-similarity of the second kind with the index α=3/2.

Spherically symmetric gravitational collapse in Einstein Gauss–Bonnet theory

2019 ◽  
Vol 16 (12) ◽  
pp. 1950194
Author(s):  
M. Tahir ◽  
G. Abbas
Keyword(s):  
Gravitational Collapse ◽  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Coupling Constant ◽  
Last Stage ◽  
Physical Quantities ◽  
Reasonable Energy

This paper deals with spherically symmetric gravitational collapse of inhomogeneous perfect fluid in Einstein Gauss–Bonnet gravity. The physical quantities have been plotted in the EGB gravity. The Ricci Scalar and Kretschmann scalar have been determined to study the curvature singularity. The shell focusing curvature singularities are generated at last stage of gravitational collapse of object. The formation of singularity and apparent horizon depends on the initial data. Also, the energy conditions have been discussed for the reasonable energy momentum tensor. The presence of GB coupling constant [Formula: see text] modifies the structure of singularity and formation of apparent horizon.

A Metric Theory of Gravitation without Minimal Coupling of Matter and Gravitational Field

1976 ◽  
Vol 31 (12) ◽  
pp. 1451-1456 ◽  
Author(s):  
H. Goenner
Keyword(s):  
Gravitational Collapse ◽  
Symmetric Solution ◽  
Free Parameter ◽  
Universal Constant ◽  
Matter Density ◽  
Spherically Symmetric ◽  
Material System ◽  
Minimal Coupling ◽  
Spherically Symmetric Solution ◽  
Theory Of Gravitation

Abstract A metric theory of gravitation is suggested which reduces to Einstein's theory in the case of vanishing matter. If matter is present, in the Lagrangian formulation of the theory the principle of minimal coupling is given up by directly linking the matter variables to the curvature tensor. The theory contains a free parameter of dimension length. It is considered not to be a universal constant but a length characteristic for the mass of the material system described. Results diverging from those of General Relativity are to be expected for regions with high curvature i. e. especially for gravitational collapse and dense phases of the cosmos. An exact, static and spherically symmetric solution with constant matter density is discussed; it indicates that, possibly, gravitational collapse is avoided.

Five-dimensional spherical symmetric perfect fluid collapse in f(R, T) gravity

2019 ◽  
Vol 97 (6) ◽  
pp. 637-643
Author(s):  
M. Jamil Amir ◽  
Sadia Sattar
Keyword(s):  
Black Hole ◽  
Perfect Fluid ◽  
Spherically Symmetric ◽  
Junction Conditions ◽  
Field Equations ◽  
Interior Region ◽  
Exterior Region ◽  
Modified Theory Of Gravity ◽  
Apparent Horizons ◽  
Modified Theory

This paper contains the study of spherically symmetric perfect fluid collapse in the framework of f(R, T) modified theory of gravity using five-dimensional background. We consider the five-dimensional spherical symmetric metric as the interior region and a five-dimensional Schwarzschild metric as an exterior region. The Darmois junction conditions between exterior and interior regions are discussed. By taking the particular f(R, T) model, the corresponding field equations are evaluated for both marginally bound L(r) = 1 and non-marginally bound L(r) ≠ 1 cases. We find the gravitational mass of the collapsing system and discuss the apparent horizons and their time formation for different possible cases. Also, the cosmological and black hole horizons have been discussed. It has been concluded that the term involving λ plays a double role: it accelerates the collapse in the region where ρ0 < 4p0 and it slows down the collapsing of matter when ρ0 > 4p0. Further, it is noted that our results reduce to the results found by Sharif and Ahmad (J. Korean Phys. Soc. 52, 980 (2008). doi: 10.3938/jkps.52.980) in general relativity for λ = 0.

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 Conformal mapping of the Misner–Sharp mass from gravitational collapse

2016 ◽  
Vol 25 (07) ◽  
pp. 1650081 ◽  
Author(s):  
Fayçal Hammad
Keyword(s):  
Conformal Mapping ◽  
Gravitational Collapse ◽  
Conformal Transformation ◽  
Conformal Mappings ◽  
Conformal Transformations ◽  
Theories Of Gravity ◽  
Definition Of ◽  
Geometric Definition

The conformal transformation of the Misner–Sharp mass is reexamined. It has recently been found that this mass does not transform like usual masses do under conformal mappings of spacetime. We show that when it comes to conformal transformations, the widely used geometric definition of the Misner–Sharp mass is fundamentally different from the original conception of the latter. Indeed, when working within the full hydrodynamic setup that gave rise to that mass, i.e. the physics of gravitational collapse, the familiar conformal transformation of a usual mass is recovered. The case of scalar–tensor theories of gravity is also examined.

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