Browsing by Author "Ghosh, S. G."

Now showing 1 - 18 of 18

5D radiating black holes in einstein-yang-mills-gauss-bonnet gravity
(2011-08-25) Ghosh, S. G.
We derive nonstatic spherically symmetric solutions of a null uid, in ve dimension (5D), to Einstein-Yang-Mills (EYM) equations with the coupling of Gauss-Bonnet (GB) combination of quadratic curvature terms, namely, 5D-EYMGB radiating black hole solution. It is shown that, in the limit, we can recover known radiating black hole solutions. The spherically symmetric known 5D static black hole solutions are also retrieved. The e ect of the GB term and Yang-Mills (YM) gauge charge on the structure and location of horizons, of the 5D radiating black hole, is also discussed.
Collapsing perfect fluid in self-similar five dimensional space-time and cosmic censorship
(2011-07-06) Ghosh, S. G.; Sarwe, S. B.; Saraykar, R. V.
We investigate the occurrence and nature of naked singularities in the gravitational collapse of a self-similar adiabatic perfect ﬂuid in a ﬁve dimensional space-time. The naked singularities are found to be gravitationally strong in the sense of Tipler and thus violate the cosmic censorship conjecture.
Collapsing shells of radiation in higher dimensional spacetime and cosmic censorship conjecture
(2001-06-26) Ghosh, S. G.; Saraykar, R. V.; Beesham, A.
Gravitational collapse of radiation shells in a non self-similar higher dimensional spherically symmetric spacetime is studied. Strong curvature naked singularities form for a highly inhomogeneous collapse, violating the cosmic censorship conjecture. As a special case, self similar models can be constructed.
Exact non-spherical radiating collapse
(2006-07-30) Ghosh, S. G.; Deshkar, D. W.
We study the junction conditions for non-spherical collapsing radiating star consisting of a shearing fluid undergoing radial heat flow with outgoing radiation. Radiation of the system is described by plane symmetric version of Vaidya solution. Junction conditions which match the collapse solutions to an exterior Vaidya metric show that, at the boundary, the pressure is proportional to the magnitude of the heat flow vector. Physical quantities, analogous to spherical symmetry related to the local conservation of momentum and surface red-shift, are also obtained. Finally, exact gravitational collapse solutions, for both shear and shear-free case, have been obtained by integrating a field equation.
Five dimensional dust collaspe with cosmological constant
(2006-07-31) Ghosh, S. G.; Deshkar, D. W.; Saste, N. N.
We study ﬁve dimensional spherical collapse of a inhomogeneous dust in presence of a positive cosmological constant. The general interior solutions, in the closed form, of the Einstein ﬁeld equations, i.e., the 5D Tolman-Bondi-de Sitter, is obtained which in turn is matched to exterior 5D Scwarschild-de Sitter. It turns out that the collapse proceed in the same way as in the Minkowski background, i.e., the strong curvature naked singularities form and thus violate the cosmic censorship conjecture. A brief discussion on the causal structure singularities and horizons is also given.
Generating dynamical black hole solutions
(2011-07-06) Dawood, A.K.; Ghosh, S. G.
We prove a theorem that characterizes a large family of non-static solutions to Einstein equations, representing, in general, spherically symmetric Type II ﬂuid. It is shown that the best known dynamical black hole solutions to Einstein equations are particular cases from this family. Thus we extend a recent work of Salgado [12] to non-static case. The spherically symmetric static black hole solutions, for Type I ﬂuid, are also retrieved.
Gravitational collapse of null strange quark fluid and cosmic censorship
(2002-04-01) Ghosh, S. G.; Dadhich, Naresh
We study gravitational collapse of the general spherically symmetric null strange quark ﬂuid having the equation of state, p = (ρ − 4B)/n, where B is the bag constant. An interesting feature that emerges is that the initial data set giving rise to naked singularity in the Vaidya collapse of null ﬂuid gets covered due to the presence of strange quark matter component. Its implication to the Cosmic Censorship Conjecture is discussed.
Gravitational collapse of perfect fluid in self-similar higher dimensional space-times
(2011-07-05) Ghosh, S. G.; Deshkar, D. W.
We investigate the occurrence and nature of naked singularities in the gravitational collapse of an adiabatic perfect ﬂuid in self-similar higher dimensional space-times. It is shown that strong curvature naked singularities could occur if the weak energy condition holds. Its implication for cosmic censorship conjecture is discussed. Known results of analogous studies in four dimensions can be recovered.
Gravitational collapse of type II fluid in higher dimensional space-times
(2002-04-30) Ghosh, S. G.
We ﬁnd the general solution of the Einstein equation for spherically symmetric collapse of Type II ﬂuid (null strange quark ﬂuid) in higher dimensions. It turns out that the nakedness and curva- ture strength of the shell focusing singularities carry over to higher dimensions. However, there is shrinkage of the initial data space for a naked singularity of the Vaidya collapse due to the presence of strange quark matter.
Higher dimensional dust collapse with a cosmological constant
(2005-07-01) Ghosh, S. G.; Deshkar, D. W.
The general solution of the Einstein equation for higher dimensional (HD) spherically symmetric collapse of inhomogeneous dust in presence of a cosmological term, i.e., exact interior solutions of the Einstein ﬁeld equations is presented for the HD Tolman-Bondi metrics imbedded in a de Sitter background. The solution is then matched to exterior HD Scwarschild-de Sitter. A brief discussion on the causal structure singularities and horizons is provided. It turns out that the collapse proceed in the same way as in the Minkowski background, i.e., the strong curvature naked singularities form and that the higher dimensions seem to favor black holes rather than naked singularities.
Higher Dimensional Radiation Collapse and Cosmic Censorship
(2000-11-12) Ghosh, S. G.; Saraykar, R. V.
We study the occurrence of naked singularities in the spherically symmetric collapse of radiation shells in a higher dimensional spacetime. The necessary conditions for the formation of a naked singularity or a black hole are obtained. The naked singularities are found to be strong in the Tipler’s sense and thus violating cosmic censorship conjecture.
Non-marginally bound inhomogeneous dust collapse in higher dimensional space-time
(2002-03-01) Ghosh, S. G.; Banerjee, A.
We investigate the occurrence and nature of a naked singularity in the gravitational collapse of an inhomogeneous dust cloud described by a self-similar higher dimensional Tolman-Bondi space-time. Bound, marginally bound and unbound space-times are analyzed. The degree of inhomogeneity of the collapsing matter necessary to form a naked singularity is given.
Non-spherical collapse of a radiating star
(2002-04-01) Ghosh, S. G.; Deshkar, D. W.
We study the junction conditions for non-spherical (plane symmetric) collapsing ra- diating star consisting of a shearing ﬂuid undergoing radial heat ﬂow with outgoing radiation. Radiation of the system is described by plane symmetric Vaidya solution. Physical quantities relating to the local conservation of momentum and surface red-shift are also obtained.
On naked singularities in higher dimensional Vaidya space-times
(2000-08-16) Ghosh, S. G.; Dadhich, Naresh
We investigate the end state of gravitational collapse of null ﬂuid in higher di- mensional space-times. Both naked singularities and black holes are shown to be developing as ﬁnal outcome of the collapse. The naked singularity spectrum in col- lapsing Vaidya region (4D) gets covered with increase in dimensions and hence higher dimensions favor black hole in comparison to naked singularity. The Cosmic Censor- ship Conjecture will be fully respected for a space of inﬁnite dimension.
On naked singularities in higher dimensional Vaidya space-times
(2001-04-03) Ghosh, S. G.; Dadhich, Naresh
We investigate the end state of gravitational collapse of null ﬂuid in higher di- mensional space-times. Both naked singularities and black holes are shown to be developing as ﬁnal outcome of the collapse. The naked singularity spectrum in col- lapsing Vaidya region (4D) gets covered with increase in dimensions and hence higher dimensions favor black hole in comparison to naked singularity. The Cosmic Censor- ship Conjecture will be fully respected for a space of inﬁnite dimension
Radiating Kerr-Newman black hole in f(R) gravity
(IUCAA, 2015-02) Ghosh, S. G.; Maharaj, S. D.; Papnoi, Uma
Role of the space-time dimensions & the fluid equation of state in spherical gravitational collapse
(2011-07-06) Dadhich, Naresh; Ghosh, S. G.; Deshkar, D. W.
We study the spherically symmetric collapse of a ﬂuid with non-vanishing radial pressure in higher dimensional space-time. We obtain the general exact solution in the closed form for the equation of state (Pr = γρ) which leads to the explicit construction of the root equation governing the nature (black hole versus naked singularity) of the central singularity. A remarkable feature of the root equation is its invariance for the three cases: (D + 1, γ = −1), (D, γ = 0) and (D − 1, γ = 1) where D is the dimension of space-time. That is, for the ultimate end result of the collapse, D-dimensional dust, D + 1 - AdS (anti de Sitter)-like and D − 1 - dS-like are absolutely equivalent.
Spinning Higher Dimensional Einstein-Yang-Mills black holes
(IUCAA, 2015-02) Ghosh, S. G.; Papnoi, Uma