Emergent inflation from a Nambu--Jona-Lasinio mechanism in gravity with non-dynamical torsion

Understand

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 $r\sim 10^{-4} \div 10^{-2}$, which nonetheless would be detectable by the next generation of experiments, including BICEP 3 and the AliCPT projects.