In this paper, we study one of the new dark energy models named Tsallis holographic dark energy (THDE) model considering the Bianchi type-III spacetime model. Considering deceleration parameter, transition from deceleration to acceleration phase happens at [Formula: see text]. The equation of state (EoS) parameter has been found using the Granda–Oliveros (GO) scale. It is found that for [Formula: see text] values, EoS parameter behaves like the quintessence era; for [Formula: see text], EoS parameter behaves like the phantom dark energy and approaches [Formula: see text]CDM model at late-time cosmic acceleration phase. Also, we reconstructed a correspondence between THDE model and some well-known scalar fields, such as tachyon, quintessence and [Formula: see text]-essence. In addition, we evaluated equation of state parameter, kinetic energy and scalar potential versus time.
In this work we solve Dirac equation by using the method of seperation of variables. Then we analyzed the particle creation process. To compute the density number of particles created Bogoliubov transformation technique is used.
We mainly focus on the idea that the dynamics of the whole universe may be understood by making use of torsion [Formula: see text] and curvature [Formula: see text] at the same time. The [Formula: see text]-gravity can be considered as a fundamental gravitational theory describing the evolution of the universe. The model can produce the unification of the general relativity (GR), teleparallel gravity (TPG), [Formula: see text]-gravity and [Formula: see text]-gravity theories. For this purpose, the corresponding Lagrangian density is written in terms of an arbitrary function of the torsion and curvature scalars. Furthermore, we use the absence/existence puzzle of relativistic neutron stars and thermodynamical laws as constraining tools for the new proposal.
Abstract. Considering the Møller, Weinberg and Qadir-Sharif's definitions in general relativity, we find the momentum four-vector of the closed universe based on the Bianchi-type metrics. The momentum four-vector(due to matter plus fields) is found to be zero. This result supports the viewpoints of Albrow and Tryon and extends the previous works by Cooperstock-Israelit, Rosen, Johri et al., Banerjee-Sen and Vargas who investigated the problem of the energy in Friedmann-Robertson-Walker universe and Saltı-Havare who studied the problem of the energy-momentum of the viscous Kasner-type space-times.
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