Bianchi type I cosmological models with variableG and A

Einstein's equations with variableG and A scalars are considered for a Bianchi type I metric. A solution is found in which the cosmological term varies inversely with the square of time. As in the case of the flat Friedmann-Lemaître-Robertson-Walker (flrw) models discussed recently, there is then no dimensional constant associated with A. However, it is shown that the time behaviour of Bianchi type I inflationary solutions cannot be of the pure de Sitter type. This shows that if the flat FLRW inflationary solutions previously considered are perturbed by the introduction of Bianchi type I anisotropy, then the time evolution may be perturbed from the pure exponential form.     

Cosmological models with constant deceleration parameter and bulk viscous mode

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.     

Whitrow-Randall's relation and Brans-Dicke cosmology re-visited

The homogeneous and isotropic Brans-Dicke cosmological solutions satisfying Whitrow-Randall's relation which have been discussed recently by Berman and Som are re-examined. After correcting an error in their work, we extend their results and present the most general solution by solving a differential equation completely. We show that Mach's assumption leads to power-law solutions in the Euclidean case.     

Variable-G cosmology and creation

It has recently been asserted that a universe with a time-varying gravitational constantG necessarily implies creation if the rest mass of matter particles is constant. It is shown that this is not necessarily true. An example of a cosmological model with variableG and is presented, in which there is no creation and in which the rest mass of matter particles is constant.     

Emergence and expansion of cosmic space in an accelerating BIon

The European Physical Journal C - In this paper, we calculate the $$B\rightarrow D$$ transition form factors (TFFs) within the light-cone sum rules (LCSRs) and predict the ratio $$\mathcal {R}(D)$$...     

Causal dissipative cosmology

The full version of the causal thermodynamics of non-equilibrium phenomena is discussed in the context of the flat Friedmann-Robertson-Walker cosmological model. Power law solutions for the scale factor are shown to exist. It is also shown that the temporal behaviour of the temperature depends on the functional dependence of the coefficient of bulk viscosity on density.     

Large numbers hypothesis and Whitrow-Randall-Sciama relation in Brans-Dicke theory

It has recently been suggested in Brans-Dicke theory that the so-called Whitrow-Randall-Sciama relation plus the assumption of a constant deceleration parameter implies the large numbers hypothesis. It is shown that this claim is not always true.     

The large numbers hypothesis and the cosmological constant

A recent generalization of Dirac's large numbers hypothesis has implications for the cosmological constant problem. We show that this generalization follows from the usual large numbers hypothesis.