The Cosmology of Interacting Spin-2 Fields

TL;DR

This paper explores a novel multi-vierbein theory of interacting spin-2 fields, revealing rich cosmological behaviors such as de Sitter, dark-energy, and bouncing solutions, while avoiding ghosts present in metric-based models.

Contribution

It introduces a ghost-free multi-vierbein gravitational theory without constraints, expanding the class of multi-gravitational models and analyzing their cosmological implications.

Findings

Discovery of de Sitter solutions with effective cosmological constant

Identification of dark-energy and bouncing cosmological solutions

Demonstration of ghost-free multi-vierbein interactions

Abstract

We investigate the cosmology of interacting spin-2 particles, formulating the multi-gravitational theory in terms of vierbeins and without imposing any Deser-van Nieuwenhuizen-like constraint. The resulting multi-vierbein theory represents a wider class of gravitational theories if compared to the corresponding multi-metric models. Moreover, as opposed to its metric counterpart which in general seems to contain ghosts, it has already been proved to be ghost-free. We outline a discussion about the possible matter couplings and we focus on the study of cosmological scenarios in the case of three and four interacting vierbeins. We find rich behavior, including de Sitter solutions with an effective cosmological constant arising from the multi-vierbein interaction, dark-energy solutions and nonsingular bouncing solutions.