Gravitational Field of Domain Walls in Higher Dimension

In this paper, we study the gravitational field of domain wall in fivedimensional space-time. Exact solutions of Einstein's equations for a scalarfield with a potential V(Ø) are presented, describing thegravitational field of plane symmetric domain walls. The solution showsthat the energy density as well as pressure in the perpendicular directionon both sides of the walls to be reflection symmetric with respect to thewalls.PACS numbers: 98.80 cq, 0450     

A Study of an Inhomogeneous Bianchi-I Model in Lyra Geometry

The inhomogeneous Bianchi-I model based on Lyra's geometry has been studied in the cosmological theory in presence of a massless inhomogeneous scalar field whose potential has a flat part. The field equations are solved using separation of variables and it is shown that one of the time part of the field equations are solvable for any arbitrary other cosmic scale function. Solutions for a particular form of cosmic scale (time part) is presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrobiology of some solar salt works in India

The hydrobiology of two Indian solar salt works was investigated. A salient feature was variability in physico-chemical and biological characteristics. The filamentous cyanophyceansLyngbya majuscula andOscillatoria salina and the chlorophyceanXenococcus aceervatus were the major primary producers. Significant fauna were protozoans, rotifers and copepods.Artemia was present in only one set of solar salt pans, where it was dominant. The study illustrates the importance ofArtemia in the biological management of solar salt works. This paper is dedicated to Thiru. K. Ayyaru Vandayar, Member, Governing body, A.V.V.M. Sri Pshpam College (Autonomous), Poondi, on his sixtieth birthday     

Anisotropic quintessence stars

We propose a relativistic model for: quintessence stars with the combination of an anisotropic pressure corresponding to normal matter and a quintessence dark energy having a characteristic parameter ω _q such that $-1<\omega_{q}< -\frac{1}{3}$ . We discuss various physical features of the model and show that the model satisfies all the regularity conditions and can provide stable equilibrium configurations.     

Wormholes supported by two non-interacting fluids

We provide a new matter source that supplies fuel to construct wormhole spacetime. The exact wormhole solutions are found in the model having, besides real matter, an anisotropic dark energy. We have shown that the exotic matters that are the necessary ingredients for wormhole physics violate null and weak energy conditions but obey strong energy condition marginally. Though the wormhole comprises of exotic matters yet the effective mass remains positive. We have calculated the effective mass of the wormhole up to 8 km from the throat (assuming throat radius as 4 km) as 1.3559M _⊙. Some physical features are briefly discussed.     

Galactic rotation curves and brane-world models

In the present investigation, flat rotational curves of the galaxies are considered under the framework of brane-world models where the four-dimensional effective Einstein equation has extra terms which arise from the embedding of the 3-brane in the five-dimensional bulk. It has been shown here that these long-range bulk gravitational degrees of freedom can act as a mechanism to yield the observed galactic rotation curves without the need for dark matter. The present model has the advantage that the observed rotation curves result solely from well-established non-local effects of gravitation, such as dark radiation and dark pressure under a direct use of the condition of flat rotation curves and does not invoke any exotic matter field.     

Gravitational field of domain wall in Lyra geometry

In this paper, we study the domain wall with time dependent displacement vectors based on Lyra geometry in normal gauge i.e. displacement vector φ _i ^* =[β(t),0,0,0]. The field theoretic energy momentum tensor is considered with zero pressure perpendicular to the wall. We find an exact solutions of Einstein’s equation for a scalar field φ with a potential V(φ) describing the gravitational field of a plane symmetric domain wall. We have seen that the hyper surfaces parallel to the wall (z=constant) are three dimensional de-sitter spaces. It is also shown that the gravitational field experienced by test particle is attractive.