COSMOLOGICAL MODELS WITH CONSTANT DECELERATION PARAMETER IN BRANS-DICKE THEORY

A detailed study of cosmological models with constant deceleration parameter q is undertaken in the framework of Brans-Dicke theory. These models are divided into two categories: (i) singular models with expansion driven by big-bang impulse, (ii) non-singlar models with expansion driven by creation of matter particles. Prigogine's hypothesis of creation of matter out of gravitational energy is analysed and extended to BD cosmology To accommodate the creation of new particles, the universe is regarded as an open thermodynamical system and the energy conservation equation is modified with the incorporation of a creation pressure term p(c) in the energy-momentum tensor ($) over tilde T-ab. The exact solutions of the field equations of BD theory with ($) over tilde T-ab are obtained using the power law relation phi = KR(alpha), which leads to models with constant q. The behaviour of the solutions is investigated for different range of values of alpha. The role played by the BD scalar field phi and creation of matter particles in the expansion of the universe is investigated. It is found that one particular model with constant q has exponential expansion.