Browsing by Author "Ray, Saibal"

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Classical electron model with negative energy density in Einstein-Cartan theory of gravitation
(2011-07-05) Ray, Saibal; Bhadra, Sumana
Experimental result regarding the maximum limit of the radius of the electron ∼ 10−16 cm and a few of the theoretical works suggest that there might have some negative energy density regions within the particle in general theory of relativity. It is argued in the present investigation that such a negative energy density also can be obtained with a better physical interpretation in the framework of Einstein-Cartan theory.
Electromgnetic Mass in (n+2) Dimensional Space-times
(2005-11-01) Ray, Saibal
Einstein-Maxwell ﬁeld equations correspoding to higher dimensional description of static spherically symmetric space-time have been solved under two speciﬁc set of conditions, viz., (i) ρ = 0, ν′= 0 and (ii) ρ = 0, ν′= 0 where ρ and ν represent the mass density and metric potential. The solution sets thus obtained satisfy the criteria of being electromagnetic mass model such that the gravitational mass vanishes for the vanishing charge density σ and also the space-time becomes ﬂat. Physical features related to other parameters also have been discussed.
Energy density in general relativity : a possible role of cosmological constant
(2011-07-05) Ray, Saibal; Bhadra, Sumana
We consider a static spherically symmetric charged anisotropic ﬂuid source of radius ∼ 10−16 cm by introducing a variable Λ dependent on the radial coordinate r under general relativity. From the solution sets a possible role of the cosmological constant is investigated which indicates the dependency of energy density on it.
Physical properties of Tolman-Bayin solutions: Some cases of static charged fluid spheres in general relativity
(2005-05-01) Ray, Saibal; Rahaman, Farook; Ray, Subharthi; et al.
In this article, Einstein-Maxwell space-time has been considered in connection to some of the astrophysical solutions as previously obtained by Tolman (1939) and Bayin (1978). The eﬀect of inclusion of charge into these solutions has been investigated thoroughly and also the nature of ﬂuid pressure and mass density throughout the sphere have been discussed. Mass-radius and mass-charge relations have been derived for various cases of the charged matter distribution. Two cases are obtained where perfect ﬂuid with positive pressures give rise to electromagnetic mass models such that gravitational mass is of purely electromagnetic origin.
Relativistic anisotropic charged fluid spheres with varying cosmological constant
(2011-07-05) Ray, Saibal; Bhadra, Sumana; Sengupta, Anand
Static spherically symmetric anisotropic source has been studied for the Einstein- Maxwell ﬁeld equations assuming the erstwhile cosmological constant Λ to be a space-variable scalar, viz., Λ = Λ(r). Two cases are examined out of which one reduces to isotropic sphere. The solutions thus obtained are shown to be electromagnetic in origin as a particular case. It is also shown that the generally used pure charge condition, viz., ρ+pr = 0 is not always required for constructing electromagnetic mass models.
Relativistic Gravitational mass in Tolman-VI type solution
(2011-07-06) Ray, Saibal; Das, Basanti
Some known solutions for static charged ﬂuid spheres of Tolman-VI type in general relativity are reexamined. The gravitational mass that appears in the Pant and Sah [1] and Tikekar [2] solutions is shown to be of electromagnetic origin in the sense that the gravitational mass, along with all other physical quantities, depends on the electromag- netic ﬁeld alone. The energy condition, singularity and stability problems of the models are discussed thoroughly. VI
Searching for a solution to the age problem of the universe
(2011-07-06) Ray, Saibal; Mukhopadhyay, Utpal
(Dated: August 20, 2010) We present here a phenomenological cosmological model under perfect ﬂuid distribution with a stiﬀ equation of state p = ρ. The erstwhile cosmological constant is assumed to be a time dependent variable, i.e., Λ = Λ(t) in our study. It has been shown that the estimates of diﬀerent cosmological parameters from this model are in good agreement with the experimental results, especially 13.79 Gyr as the age of the universe is quite satisfactory. The behavior and relation of Λ-stiﬀ ﬂuid model with dust, viscous ﬂuid and variable G have also been investigated in detail.
Tolman - Bayin type static charged fluid spheres in general relativity
(2011-07-05) Ray, Saibal; Das, Basanti
In a static spherically symmetric Einstein-Maxwell spacetime the class of astrophysical solu- tion found out by Ray and Das (2002) and Pant and Sah (1979) are revisited here in connection to the phenomenological relationship between the gravitational and electromagnetic ﬁelds. It is qualitatively shown that the charged relativistic stars of Tolman (1939) and Bayin (1978) type are of purely electromagnetic origin. The existence of this type of astrophysical solutions is a probable extension of Lorentz’s conjecture that electron-like extended charged particle possesses only ‘electromagnetic mass’ and no ‘material mass’.