Eur. Phys. J. C (2018) 78: 480
https://doi.org/10.1140/epjc/s10052-018-5972-0

Letter

On the strong-CP problem and its axion solution in torsionful theories

Arnold Sommerfeld Center, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333, Munich, Germany

^* e-mail: georgios.karananas@physik.uni-muenchen.de

Received: 23 May 2018
Accepted: 4 June 2018
Published online: 11 June 2018

Abstract

Gravitational effects may interfere with the axion solution to the strong-CP problem. We point out that gravity can potentially provide a protection mechanism against itself, in the form of an additional axion-like field associated with torsion.