Year: 2016
Type: article
Abstract: A new covariant generalization of Einstein's general relativity is developed which allows the existence of a term proportional to ${T}_{\ensuremath{\alpha}\ensuremath{\beta}}{T}^{\ensuremath{\alpha}\ensuremath{\beta}}$ in the action functional of the theory (${T}_{\ensuremath{\alpha}\ensuremath{\beta}}$ is the energy-momentum tensor). Consequently, the relevant field equations are different from general relativity only in the presence of matter sources. In the case of a charged black hole, we find exact solutions for the field equations. Applying this theory to a homogeneous and isotropic spacetime, we find that there is a maximum energy density ${\ensuremath{\rho}}_{\mathrm{max}}$, and correspondingly a minimum length ${a}_{\mathrm{min}}$, at the early Universe. This means that there is a bounce at early times, and this theory avoids the existence of an early-time singularity. Moreover, we show that this theory possesses a true sequence of cosmological eras. We also argue that, although in the context of the standard cosmological model the cosmological constant $\mathrm{\ensuremath{\Lambda}}$ does not play any important role in the early times and becomes important only after the matter-dominated era, in this theory the ``repulsive'' nature of the cosmological constant plays a crucial role at early times in resolving the singularity.
Authors: Mahmood Roshan, Fatimah Shojai
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2485831159