2016/07/31 by Mahmood Roshan, Fatimah Shojai · 190 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Classical mechanics #Cosmological constant #Cosmology and Gravitation Theories #General relativity #Geometry #Mathematical physics #Noncommutative and Quantum Gravity Theories #Physics #Quantum mechanics #Singularity #Theoretical physics #Universe #astro-ph.CO #gr-qc
paper · pdf · doi:10.1103/physrevd.94.044002
published in Physical review. D/Physical review. D. 94(4) (American Physical Society)
openalex publication_date 2016/08/01 · arxiv created 2016/08/03 · arxiv updated 2016/08/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A new covariant generalization of Einstein's general relativity is developed which allows the existence of a term proportional to T_\ensuremathα\ensuremathβT^\ensuremathα\ensuremathβ in the action functional of the theory (T_\ensuremathα\ensuremathβ 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 \ensuremathρmax, and correspondingly a minimum length amin, 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\ensuremathΛ 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.