A special law of variation for Hubble’s parameter

Universe with Time Dependent Deceleration Parameter and Λ Term in General Relativity

“…In order to solve the field equations we normally assume a form for the matter content or that spacetime admits killing vector symmetries [10]. Solutions to the field equations may also be generated by applying a law of variation for Hubble's parameter which was proposed by Berman [11]. In simple cases the Hubble law yields a constant value of deceleration parameter.…”

“…It is worth observing that most of the well-known models of Einstein's theory and Brans-Deke theory with curvature parameter k = 0, including inflationary models, are models with constant deceleration parameter. In earlier literature cosmological models with a constant deceleration parameter have been studied by Berman [11], Berman and Gomide [12], Johri and Desikan [13], Singh and Desikan [14], Maharaj and Naidoo [15], Pradhan and et al [16] and others. But redshift magnitude test has had a chequered history.…”

Magnetized Dark Energy Cosmological Models with Constant Deceleration Parameter

“…(i) We constrain the system of equations with a law of variation for the Hubble parameter proposed by Berman [31] for solving FRW models, which yields a constant value of deceleration parameter (DP). Singh et al [32] have studied flat FRW and Bianchi type models by using the special law of Hubble parameter that yields constant value of deceleration parameter.…”

“…As the line element (2.1) is completely characterized by Hubble parameter H. We also use a well-known relation Berman [31] between the average Hubble parameter H and average scale factor given as We assume that the magnetized dark energy is minimally interacting, hence energy conservation equation (2.8) can be split into two separately additive conserver components: namely, the conservation of energy -momentum tensor for the anisotropic fluid and for the magnetic field.…”

A General Bianchi Type Viscous Fluid Cosmological Model with Both Deceleration and Acceleration

“…So far some authors proposed constant as well as time-dependent forms of q and derived expressions for the average scale factor a, which are further used for solving the field equations. It has been observed that the cosmological models based on constant deceleration parameter by Berman [23] and linearly varying deceleration parameter proposed by Akarsu and Dereli [24] are either decelerating or accelerating. But for an universe which was decelerating in the the past and accelerating at present time, the deceleration parameter must show signature flipping (Riess et al [25], Amendola [26]).…”