n-DBI Gravity in a nutshell

TL;DR

This paper introduces n-DBI gravity, a Lorentz-invariance-breaking model with a scalar degree of freedom, capable of explaining inflation and black holes without additional fields, and demonstrates its well-behaved scalar mode.

Contribution

It presents a novel gravity model that breaks Lorentz invariance, predicts inflation without an inflaton, and admits GR black hole solutions, with a well-behaved scalar mode.

Findings

Predicts inflation without inflaton

Admits GR black hole solutions

Scalar mode is stable and free of pathologies

Abstract

We present a new model of gravity which explicitly breaks Lorentz-invariance by the introduction of a unit time-like vector field, thereby giving rise to an extra (scalar) degree of freedom. We discuss its cosmology, exact solutions and the dynamics of the scalar mode. We show that it predicts inflation without an inflaton and admits the black hole solutions of General Relativity (GR). We argue that the scalar mode is well behaved and contains none of the pathologies previously found in similar models.