Inflation by spin and torsion in the Poincaré gauge theory of gravity

Department of Physics, Golestan University - P. O. Box 49138-15759, Gorgan, Iran

Received: 29 June 2017
Accepted: 6 September 2017

Abstract

In the Poincaré gauge theory of gravity, in addition to the mass-energy content, spin is also a source for gravitational interactions. Although the effects of spin are negligible at low energies, they can play a crucial role at the very early Universe when the spin density was very high. In this paper by choosing a suitable Lagrangian for the Poincaré gauge theory of gravity, and suitable energy-momentum and spin density tensors, we show that the effects of spin and torsion can lead to a inflationary phase without the need for any additional fields. No fine-tuning of parameters is required in this setup. We also calculate the scalar spectral index at the end of inflation and show that it agrees with the most recent observational data.