Abstract
We discuss how inflation can emerge from a four-fermion interaction induced by torsion. Inflation can arise from coupling torsion to Standard Model fermions, without any need of introducing new scalar particles beyond the Standard Model. Within this picture, the inflaton field can be a composite field of the SM-particles and arises from a Nambu–Jona-Lasinio mechanism in curved space-time, non-minimally coupled with the Ricci scalar. The model we specify predicts small value of the r-parameter, namely rsim 10^{-4} div 10^{-2}, which nonetheless would be detectable by the next generation of experiments, including BICEP 3 and the AliCPT projects.
Highlights
The origin of the inflaton field, mediating the inflation dynamics, is still unknown: an infinite class of Standard Model extensions or of extended theories of gravity are compatible with current Cosmic Microwave Background (CMB) data
We propose that inflation is triggered by the coupling of Standard Model fermions with gravitational torsion
Such a new mechanism can be realized within the context of the Einstein–Cartan–Holst–Sciama–Kibble theory (ECHSK) [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
Summary
The origin of the inflaton field, mediating the inflation dynamics, is still unknown: an infinite class of Standard Model extensions or of extended theories of gravity are compatible with current CMB data. We propose that inflation is triggered by the coupling of Standard Model fermions with gravitational torsion. Internal consistency of the ECHSK theory requires a new coupling between the torsion component of the connection to the Standard Model fermion fields. Integrating out torsion entails new effective four-fermion interactions, compatible with the Standard Model gauge symmetries.
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