Superfluids and the Cosmological Constant Problem

TL;DR

This paper proposes a Lorentz-violating superfluid as a novel approach to address the cosmological constant problem, enabling self-tuning of vacuum energy without instabilities.

Contribution

It introduces a new phase of massive gravity using a finite-temperature superfluid that self-tunes the cosmological constant while remaining free of pathologies.

Findings

Superfluid can degravitate a large cosmological constant.

Identifies a class of healthy, phenomenologically viable theories.

Graviton acquires a Lorentz-violating mass without instabilities.

Abstract

We introduce a novel method to circumvent Weinberg's no-go theorem for self-tuning the cosmological vacuum energy: a Lorentz-violating finite-temperature superfluid can counter the effects of an arbitrarily large cosmological constant. Fluctuations of the superfluid result in the graviton acquiring a Lorentz-violating mass and we identify a unique class of theories that are pathology free, phenomenologically viable, and do not suffer from instantaneous modes. This new and hitherto unidentified phase of massive gravity propagates the same degrees of freedom as general relativity with an additional Lorentz-violating scalar that is introduced by higher-derivative operators in a UV insensitive manner. The superfluid is therefore a consistent infrared modification of gravity. We demonstrate how the superfluid can degravitate a cosmological constant and discuss its phenomenology.