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By
Johri, V B; Singh, G P
The behaviour of gravitational energy and scalar field during the evolution of the universe within the framework of BransDicke theory has been discussed. With help of the LandauLifshitz pseudotensor for the flat FriedmannRobertsonWalker model, it is found that (i) the total energy of the universe is always zero, (ii) the BransDicke scalar field for all Ω >0 contributes energy to the negative energy of gravitational field and this gets transferred to the vacuum energy which accelerates the expansion of the universe.
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By
Desikan, Kalyani
4 Citations
BDFRW universe filled with imperfect fluid having bulk viscosity is investigated under the framework of IsraelStewartHiscock causal theory. The field equations have been solved by using the relationφ=KR^{α} whereK andα are constants, between the BransDicke scalar fieldϕ and the scale factorR. This relation, in fact, leads to a constant deceleration parameterq. It is shown that the constancy of the deceleration parameter permits only two possibilities i.e. eitherH=constant withm=1 orm=(1+b −α)/(2(1+b) −α), irrespective of the value ofɛ.
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By
Maharana, K; Singh, L P
A scheme is presented for baryon asymmetry generation in early universe through monpoleinduced baryon number violating processes in the context of a preonic model.
By
Sahni, Varun
2 Citations
The inflationary Universe resolves some of the most outstanding issues of standard cosmology including the horizon and flatness problems and the origin of density fluctuations in the Universe. Inflationary models also predict the existence of a relic gravity wave background. Both gravity waves and density fluctuations induce fluctuations in the cosmic microwave background (CMB), the discovery of large angle anisotropies in the CMB having the scale invariant spectrum predicted by inflationary models has fuelled the hope that the inflationary scenario may indeed provide the correct description of the very early Universe. Upcoming large scale galaxy surveys (SDSS & 2dF) and CMB missions (MAP, Planck Surveyor) will further probe the inflationary scenario by throwing light on the origin and evolution of large scale structure in the Universe.
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By
Singh, J P; Prasad, A; Tiwari, R K
1 Citations
Some of the RobertsonWalker cosmological models filled with a fluid with bulk viscosity have been derived which are consistent with causal thermodynamics. The models are discussed briefly.
By
Chakraborty, Subenoy; Rahaman, Md. Farook
8 Citations
A detailed analysis of the motion of test particles around global monopole in BransDicke theory of gravity has been prescribed using the HamiltonJacobi (HJ) formalism. The trajectory of the test particles are trapped by the monopole with some restriction on the coupling parameter ω.
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By
Banerjee, N
3 Citations
An isotropic homogeneous cosmological model with RobertsonWalker line element is studied in general scalar tensor theory where the parameterω is a function of the scalar field. The model consists of perfect fluid with the equation of statep=ερ. Exact solutions are obtained in Dicke’s conformally transformed units forε=1 andε=1/3 assuming a functional relationship betweenω and the scalar fieldφ. The properties are compared with vacuum models in this theory.
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By
Dadhich, Naresh
2 Citations
We prove the theorem: A necessary and sufficient condition for a spacetime to represent an isothermal fluid sphere (linear equation of state with density falling off as inverse square of the curvature radius) without boundary is that it is conformal to a spacetime of zero gravitational mass (‘minimally’ curved).
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By
Chakraborty, Subenoy; Roy, Anusua
3 Citations
Stringdust cosmology in an inhomogeneous cylindrically symmetric model is considered. Solutions are obtained only for geometric string with the separability assumption for metric coefficients.
By
Bhattacharya, Tanmoy; Roy, Probir
The known lower bound on the unstable photino mass gets invalidated by a gravitino lighter than 10^{−3} eV. Nevertheless, general bounds can be derived by feeding early universe constraints from the primary abundance of He^{4} and the extant lower bound on the gravitino mass into the lifetime for the decay photino → photon + gravitino. The massrangeO(100) eV toO(1) MeV is excluded.
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