Relaxing the cosmological constant in the extreme ultra-infrared

TL;DR

This paper explores a theoretical framework where gravity's behavior at ultra-long distances could naturally relax the cosmological constant, potentially explaining its small observed value without fine-tuning.

Contribution

It proposes a dynamical critical behavior of gravity in the ultra-infrared regime, linking the relaxation of the cosmological constant to a high critical exponent and scale ratios.

Findings

Cosmological constant becomes irrelevant for z_EuIR > 1

Relaxation mechanism connects IR and EuIR scales via critical exponent

Lorentz invariance may emerge at shorter distances

Abstract

We speculate on the dynamical critical behavior of gravity in the extreme ultra-infrared (EuIR) sector and a mechanism to relax the cosmological constant. We show that in the EuIR the cosmological constant term could be made irrelevant for values of the dynamical critical exponent z_EuIR greater than one. We discuss a possible realization of this idea that connects the relaxation of the cosmological constant to the ratio between the EuIR and IR scales, where the latter serves as the 'UV' cutoff of our (ultra long distance) effective theory, with z_IR ~ 1. For distances smaller than the IR regime Lorentz invariance emerges. We entertain the possibility that the effective description of the universe may not be Lorentz invariant at much larger scales. We discuss why local physics cannot detect the 'natural' value for the density of dark energy below the IR scale, and briefly comment on possible connections with holography.