An LRS Bianchi I model is considered with constant deceleration parameter, $$q=\alpha -1$$, where $$\alpha \ge 0$$ is a constant. The physical and kinematical behaviour of the models for $$\alpha =0$$ and $$\alpha \ne 0$$ is studied in detail. The model with $$\alpha =0$$ describes late time acceleration, but eternal inflation demands a violation of the NEC and WEC. The acceleration is caused by phantom matter which approaches a cosmological constant at late times. The solutions with a scalar field also show that the model is compatible with a phantom field only. A comparison with the observational outcomes indicates that the universe has entered into the present accelerating phase in recent past somewhere between $$0.2\lesssim z\lesssim 0.5$$. The model obeys the “cosmic no hair conjecture”. The models with $$0 3$$ violate the DEC and the corresponding scalar field models have negative potential which is physically unrealistic.

LRS Bianchi I model with constant deceleration parameter

The effect of particle production on the evolution of the spatially flat Friedmann-Lemaitre-Robertson-Walker cosmological model during the early stages of the universe is analysed in the framework of higher derivative theory. The universe has been considered as an open thermodynamic system where particle production gives rise to a supplementary negative creation pressure in addition to the thermodynamic pressure. The dynamical behaviour of both exponential as well as power law solutions have been discussed.

Particle production in higher derivative theory

The main purpose of this paper is to investigate LRS Bianchi type I metric in the presence of perfect fluid and dark energy. In order to obtain a deterministic solution of the field equations we ha...

Accelerating dark energy universe with LRS Bianchi type-I space-time

An LRS Bianchi I model is considered with constant deceleration parameter, $q=\alpha-1$, where $\alpha\geq0$ is a constant. The physical and kinematical behaviour of the models for $\alpha=0$ and $\alpha\neq0$ is studied in detail. The model with $\alpha=0$ describes late time acceleration, but eternal inflation demands a violation of the NEC and WEC. The acceleration is caused by phantom matter which approaches a cosmological constant at late times. The solutions with a scalar field also show that the model is compatible with a phantom field only. A comparison with the observational outcomes indicates that the universe has entered into the present accelerating phase in recent past somewhere between $0.2\lesssim z\lesssim0.5$. The model obeys the "cosmic no hair conjecture". The models with $0 3$ violate the DEC and the corresponding scalar field models have negative potential which is physically unrealistic.

This paper reviews research in theoretical cosmology in South Africa, providing an overview of the work that has been done and the groups involved in that work.

Cosmology in South Africa

Recently Berman and Gomide have presented cosmological models with a constant deceleration parameter in general relativity without assuming a specific equation of state. It is shown that these models are equivalent to those with bulk viscosity. Some general remarks are made on the former models, including implications for violations of causality.

Aroonkumar Beesham

Papers

Cosmological models with constant deceleration parameter and bulk viscous mode