Bi-scalar modified gravity and cosmology with conformal invariance

Journal Article · Fri Apr 01 04:00:00 EDT 2016 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2016/04/017· OSTI ID:22524886

Saridakis, Emmanuel N. ^[1]; Tsoukalas, Minas ^[2]

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1. CASPER, Physics Department, Baylor University, Waco, TX 76798-7310 (United States)
2. Physics Department, Bo\ugaziçi University, 34342 Bebek, Istanbul (Turkey)

We investigate the cosmological applications of a bi-scalar modified gravity that exhibits partial conformal invariance, which could become full conformal invariance in the absence of the usual Einstein-Hilbert term and introducing additionally either the Weyl derivative or properly rescaled fields. Such a theory is constructed by considering the action of a non-minimally conformally-coupled scalar field, and adding a second scalar allowing for a nonminimal derivative coupling with the Einstein tensor and the energy-momentum tensor of the first field. At a cosmological framework we obtain an effective dark-energy sector constituted from both scalars. In the absence of an explicit matter sector we extract analytical solutions, which for some parameter regions correspond to an effective matter era and/or to an effective radiation era, thus the two scalars give rise to 'mimetic dark matter' or to 'dark radiation' respectively. In the case where an explicit matter sector is included we obtain a cosmological evolution in agreement with observations, that is a transition from matter to dark energy era, with the onset of cosmic acceleration. Furthermore, for particular parameter regions, the effective dark-energy equation of state can transit to the phantom regime at late times. These behaviors reveal the capabilities of the theory, since they arise purely from the novel, bi-scalar construction and the involved couplings between the two fields.

• OSTI ID: 22524886
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 04 Vol. 2016; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ACTION INTEGRAL
ANALYTICAL SOLUTION
CONFORMAL INVARIANCE
COSMOLOGICAL MODELS
COSMOLOGY
ENERGY-MOMENTUM TENSOR
EQUATIONS OF STATE
GRAVITATION
NONLUMINOUS MATTER
PHANTOMS
SCALAR FIELDS
SCALARS