Gravity with dynamical torsion

TL;DR

This paper introduces four ghost- and tachyon-free gravity models with dynamical torsion, allowing torsion to propagate multiple spin states alongside the standard massless graviton.

Contribution

It proposes new gravity Lagrangians with dynamical torsion that are free from instabilities and include propagating torsion modes.

Findings

Models are free from ghosts and tachyons.

Torsion propagates spin 1 and 0 particles.

Includes both massive and massless torsion modes.

Abstract

We propose four simple Lagrangians for gravity models with dynamical torsion which are free from ghosts and tachyons. The torsion propagates two massive or massless particles of spin 1^\pm and 0^\pm besides the massless graviton 2^+ propagated by metric.