Torsion in string-inspired cosmologies and the universe dark sector

TY - JOUR

T1 - Torsion in string-inspired cosmologies and the universe dark sector

AU - Mavromatos, Nick E.

N1 - Funding Information: Funding: This research was funded in part by the UK Science and Technology Facilities Council (STFC) under research grant ST/T000759/1. Publisher Copyright: © 2021 by the author.

PY - 2021/12

Y1 - 2021/12

N2 - Several aspects of torsion in string-inspired cosmologies are reviewed. In particular, its connection with fundamental, string-model independent, axion fields associated with the massless gravitational multiplet of the string are discussed. It is argued in favour of the role of primordial gravitational anomalies coupled to such axions in inducing inflation of a type encountered in the “Running-Vacuum-Model (RVM)” cosmological framework, without fundamental inflaton fields. The gravitational-anomaly terms owe their existence to the Green-Schwarz mechanism for the (extra-dimensional) anomaly cancellation, and may be non-trivial in such theories in the presence of (primordial) gravitational waves at early stages of the four-dimensional string universe (after compactification). The paper also discusses how the torsion-induced stringy axions can acquire a mass in the post inflationary era, due to non-perturbative effects, thus having the potential to play the role of (a component of) dark matter in such models. Finally, the current-era phenomenology of this model is briefly described with emphasis placed on the possibility of alleviating tensions observed in the current-era cosmological data. A brief phenomenological comparison with other cosmological models in contorted geometries is also made.

AB - Several aspects of torsion in string-inspired cosmologies are reviewed. In particular, its connection with fundamental, string-model independent, axion fields associated with the massless gravitational multiplet of the string are discussed. It is argued in favour of the role of primordial gravitational anomalies coupled to such axions in inducing inflation of a type encountered in the “Running-Vacuum-Model (RVM)” cosmological framework, without fundamental inflaton fields. The gravitational-anomaly terms owe their existence to the Green-Schwarz mechanism for the (extra-dimensional) anomaly cancellation, and may be non-trivial in such theories in the presence of (primordial) gravitational waves at early stages of the four-dimensional string universe (after compactification). The paper also discusses how the torsion-induced stringy axions can acquire a mass in the post inflationary era, due to non-perturbative effects, thus having the potential to play the role of (a component of) dark matter in such models. Finally, the current-era phenomenology of this model is briefly described with emphasis placed on the possibility of alleviating tensions observed in the current-era cosmological data. A brief phenomenological comparison with other cosmological models in contorted geometries is also made.

KW - Anomalies

KW - Axions

KW - Cosmology

KW - Gravitational waves

KW - Running vacuum

KW - Strings

KW - Torsion

UR - http://www.scopus.com/inward/record.url?scp=85122024828&partnerID=8YFLogxK

U2 - 10.3390/universe7120480

DO - 10.3390/universe7120480

M3 - Review article

AN - SCOPUS:85122024828

SN - 2218-1997

VL - 7

JO - Universe

JF - Universe

IS - 12

M1 - 480

ER -