Cosmological bounces, cyclic universes, and effective cosmological constant in Einstein-Cartan-Dirac-Maxwell theory

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Einstein-Cartan theory is an extension of the standard formulation of general relativity characterized by a nonvanishing torsion. The latter is sourced by the matter fields via the spin tensor, and its effects are expected to be important at very high spin densities. In this work, we analyze in detail the physics of Einstein-Cartan theory with Dirac and Maxwell fields minimally coupled to the spacetime torsion. This breaks the U(1) gauge symmetry, which is suggested by the possibility of a torsion-induced phase transition in the early Universe. The resulting Dirac-like and Maxwell-like equations are nonlinear with self-interactions as well as having fermion-boson nonminimal couplings. We discuss several cosmological aspects of this theory under the assumption of randomly oriented spin densities (unpolarized matter), including bounces, acceleration phases, and matter-antimatter asymmetry in the torsion era, as well as late-time effects such as the generation of an effective cosmological constant, dark energy, and future bounces within cyclic solutions.
© 2020 American Physical Society. F. C. is funded by the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) doctoral Grant No. PD/BD/128017/2016. F. S. N. L. acknowledges support from the FCT Scientific Employment Stimulus contract with Reference No. CEECIND/04057/2017. D. R. G. is funded by the Atraccion de Talento Investigador programme of the Comunidad de Madrid (Spain) No. 2018-T1/TIC-10431, and acknowledges further support from the Ministerio de Ciencia, Innovacion y Universidades (Spain) Project No. PID2019-108485 GB-I00/AEI/10.13039/501100011033, the Spanish Project No. FIS2017-84440-C2-1-P (MINECO/FEDER, EU), and the Edital 006/2018 PRONEX (FAPESQ-PB/CNPQ, Brazil) Grant No. 0015/2019. The authors also acknowledge funding from FCT Projects No. UID/FIS/04434/2020, No. CERN/FIS-PAR/0037/2019 and No. PTDC/FIS-OUT/29048/2017. F. C. thanks the hospitality of the Department of Theoretical Physics and IPARCOS of the Complutense University of Madrid, where part of this work was carried out. This article is based upon work from COST Actions CA15117 and CA18108, supported by COST (European Cooperation in Science and Technology).
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