Metamorphosis of the Cosmological Constant and 5D Origin of the Fiducial Metric

TL;DR

This paper proposes a novel framework where the cosmological constant is absorbed into a 5D universe, linking it to the fiducial metric in massive gravity, and resolving quantum strong coupling issues.

Contribution

It introduces a 5D AdS gravity setup where the fiducial metric of massive gravity arises from the bulk, removing the cosmological constant from our universe and addressing quantum strong coupling problems.

Findings

The fiducial metric is derived from a 5D AdS bulk.

The approach eliminates quantum loop counterterms in massive gravity.

The cosmological constant is absorbed into a separate universe.

Abstract

In a recently proposed theory, the cosmological constant (CC) does not curve spacetime in our universe, but instead gets absorbed into another universe endowed with its own dynamical metric, nonlocally coupled to ours. Thus, one achieves a long standing goal of removing entirely any cosmological constant from our universe. Dark energy then cannot be due to a cosmological constant, but must be obtained via other mechanisms. Here we focus on the scenario in which dark energy is due to massive gravity and its extensions. We show how the metric of the other universe, that absorbs our CC, also gives rise to the fiducial metric known to be necessary for the diffeomorphism invariant formulation of massive gravity. This is achieved in a framework where the other universe is described by 5D AdS gravity, while our universe lives on its boundary and is endowed with dynamical massive gravity. A non-dynamical pullback of the bulk AdS metric acts as the fiducial metric for massive gravity on the boundary. This framework also removes a difficulty caused by the quantum strongly coupled behavior of massive gravity at the Lambda3 scale: in the present approach, the massive gravity action does not receive any loop-induced counterterms, despite being strongly coupled.