S. K. Banerjee

Bianchi type II string cosmological models in general relativity

The paper deals with locally rotationally symmetric (LRS) cosmological models of Bianchi type II representing clouds of geometrical as well as massive strings. The energy--momentum tensor for such strings as formulated by Letelier is used to construct a massless string cosmological model and some massive string cosmological models for which is a constant. The physical behaviour of these models is also discussed.

Possible Interpretations of the Magnitude-Redshift Relation for Supernovae of Type Ia

It has been shown by Riess et al. and Perlmutter et al. that the observed redshift-magnitude relation for supernovae of type Ia, which suggests that the deceleration parameter q0 is negative, can be explained in a Friedmann model with a positive cosmological constant. We show that a quasi–steady state cosmology (QSSC) model can also fit the supernova data. Since most of the emphasis and publicity have been concentrated on explanations involving the Friedmann model, we show how a good fit can be obtained to the observations in the framework of the QSSC. Using this model, we show that absorption due to intergalactic dust may play an important role. This may explain why a few of the supernovae observed show large deviations from the curve determined by the majority of the data.

The quasi-steady state cosmology: a problem of stability

This paper examines the gravitational stability against small perturbations of the quasi-steady state cosmological model. This model was first introduced by Hoyle et al., who in subsequent papers looked at its various theoretical and observational implications. Here we carry out a perturbation analysis of the exact solution of the field equations obtained by Sachs et al. in the noncreative mode which describes the oscillatory feature of this model. We show that the perturbations grow only to a limited amount and then fall off, thus confirming the stability of the solution. We discuss the implications of this result for structure formation in this cosmology.

Bianchi VI0 electric type cosmological models in General Relativity with stiff fluid and heat conduction

The paper consists of some exact tilted solutions for a homogeneous Bianchi type VI0 universe. The material distribution is taken to be a stiff fluid with heat conduction. The physical and kinematical parameters have also been calculated to discuss the models in detail.

A Bianchi type II cosmological model of Petrov type D representing an imperfect fluid with a source-free magnetic field

We consider a Bianchi type II spacetime of Petrov type D representing an imperfect fluid and an incident source-free magnetic field. The physical behaviour of the realistic model is discussed in detail.

Bianchi VI cosmological models representing perfect fluid and radiation with electric-type free gravitational fields

A homogeneous Bianchi type VIh cosmological model filled with perfect fluid, null electromagnetic field and streaming neutrinos is obtained for which the free gravitational field is of the electric type. The barotropic equation of statep = (γ−1)ɛ is imposed in the particular case of Bianchi VI0 string models. Various physical and kinematical properties of the models are discussed.

On searches for gravitational waves from mini-creation events by laser interferometric detectors

As an alternative view to the standard big bang cosmology, the quasi-steady-state cosmology argues that the Universe was not created in a single great explosion: it did not have a beginning, nor will it ever come to an end. The creation of new matter in the Universe is a regular feature occurring through finite explosive events. Each creation event is called a mini-bang, or a mini-creation event. Gravitational waves are expected to be generated as a result of any anisotropy present in this process of creation. A mini-creation event that ejects matter in two oppositely directed jets is thus a source of gravitational waves, which can in principle be detected by laser interferometric detectors. In the present work we consider the gravitational waveforms propagated by linear jets and then estimate the response of laser interferometric detectors such as LIGO and LISA.

Dynamics of ejection from galaxies and the variable mass hypothesis

Increasing numbers of active galaxies with significant alignments of quasars are being observed. It is the purpose of this paper to explore ejection dynamics of these quasars using the variable mass hypothesis (VMH) originally discussed by Narlikar and Das in 1980. According to the VMH quasars are ejected from parent galaxies initially with zero rest mass which grows through a Machian interaction. The intrinsic redshift of the quasar steadily decreases as its mass grows, but always remains in excess of the redshift of the galaxy. The ultimate aim of this hypothesis is to quantitatively relate the observed ordering of redshifts of ejected quasars, with separation from the galaxy, their intrinsic redshifts and the age of the evolutionary stage of the ejecta.

Some bianchi type II universes with special free-gravitational fields

The paper considers a homogeneous Bianchi type II universe. Under each of the conditionsChijkChijk=0 and*ChijkChijk=0 different types of models have been studied and their physical and kinematical properties have been discussed.