String fluid cosmological models in general relativity

Abstract

LRS Bianchi type-I string cosmological models are studied in the frame work of general relativity when the source for the energy momentum tensor is a bulk viscous fluid containing one dimensional strings embedded in electromagnetic field. A barotropic equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscosity is assumed to be inversely proportional to the scalar expansion. The physical and kinematical properties of the models are discussed. The effect of viscosity and electromagnetic field on the physical and kinematical properties is also investigated.

Bulk viscous string cosmological models with electromagnetic field

“…The necessity of electromagnetic field along with the topological defects in the form of cosmic string has already been established in our earlier work (Tripathy et al 2008a). In a recent work (Tripathy et al 2008b), we have justified the need of viscosity in describing the evolution of the properties of universe. In that work (Tripathy et al 2008b), we have assumed a general linear relationship between the string tension density and the energy density and the viscous fluid is taken to be barotropic i.e.…”

“…Besides the pioneer works of Letelier (1983) and Stachel (1980), , , Yadav et al (2007aYadav et al ( , 2007b, Banerjee et al (1990), Rahaman et al (2003), Ram and Singh (1995), Singh and Singh (1999), Tikekar and Patel (1992), Reddy (2003aReddy ( , 2003b, Pradhan et al (2007), Katore and Rane (2006), Bali and Anjali (2006), Tripathy et al (2008aTripathy et al ( , 2008bTripathy et al ( , 2009) have studied string cloud cosmology. String cosmologies with bulk viscosity have been studied by Wang (2004Wang ( , 2005Wang ( , 2006, Bali et al ( , 2008 and Tripathy et al (2008b).…”

“…In a recent work (Tripathy et al 2008b), we have justified the need of viscosity in describing the evolution of the properties of universe. In that work (Tripathy et al 2008b), we have assumed a general linear relationship between the string tension density and the energy density and the viscous fluid is taken to be barotropic i.e. the proper pressure is considered to be directly proportional to the energy density.…”

Cosmic acceleration and anisotropic models with magnetic field

“…In order to address the issue of the smallness in the angular power spectrum of the temperature anisotropy, plane symmetric models have been proposed in recent times [38,39,40,41]. Plane Symmetric or Locally Rotationally Symmetric Bianchi type I (LRSBI) models have also been studied in different context to address different issues of cosmology [42,43,44,45,46,47,48,49,50]. These models are more interesting in the sense that they are more general then FRW models.…”

“…The pressure anisotropy in the cosmic fluid comes from the presence of cosmic strings and magnetic field. In our earlier works [42,43,44,45], we have investigated plane symmetric anisotropic models with cosmic strings, bulk viscosity or magnetic strings in GR. However, in the present work, we extend those works to investigate the role of magnetic field towards cosmic acceleration in the framework of Barber's Self Creation Cosmology.…”