Bulk viscous barotropic magnetised string cosmological models

Abstract

Spatially homogeneous and anisotropic 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 a magnetic field. A barotropic equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscous pressure is assumed to be proportional to the energy density. The effects of viscosity and electromagnetic field on the properties of the model are investigated. The role of bulk viscosity and electromagnetic field in getting an inflationary phase and in establishing a string phase in the universe is studied.

Anisotropic universe with cosmic strings and bulk viscosity

“…We have assumed a barotropic bulk viscous pressure to account for the bulk viscosity. This is in the motivation to keep the proper pressure and the contribution of bulk viscosity to pressure in the same dimension (Tripathy et al 2009b). In the present work the role of bulk viscosity in establishing an inflationary phase of universe is investigated.…”

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.…”

Bianchi type-VIh string cloud cosmological models with bulk viscosity

“…Right after the pioneer works of Letelier (1983) and Stachel (1980), there has been a good many works on string cosmologies with different space times, either in the frame work of Einstein Relativity or modified theories of gravity. Recently, Bali and Pradhan (2007), Bali et al (2007a), Pradhan et al (2007), Wang (2006), Tripathy et al (2008Tripathy et al ( , 2009aTripathy et al ( , 2009bTripathy et al ( , 2009cTripathy et al ( , 2010 have investigated different aspects of cosmic string in general relativity. Since the universe can be represented by a collection of extended objects like galaxies, string cloud cosmological models can help understand the evolution of the early universe.…”

“…It is generally believed that a non-zero positive cosmological constant ∼ 2h 2 × 10 −56 cm −2 is required to account for the observations of the distant type Ia Supernova (Reiss et al 1998(Reiss et al , 2004Perlmutter et al 1998Perlmutter et al , 1999. On the other hand, cosmological models with dissipative phenomena like bulk viscosity are more interesting because of their prime roles in getting inflationary phases of the universe (Barrow 1986;Zimdahl 1996;Pavon et al 1991;Maartens 1995;Lima et al 1993;Tripathy et al 2009cTripathy et al , 2010. Bulk viscosity driven inflation is primarily due to the negative bulk viscous pressure giving rise to a total negative effective pressure which may overcome the pressure due to the usual gravity of matter distribution in the universe and provides an impetus to drive it apart.…”