Comment on "Dark Energy from Time Crystals"

TL;DR

This paper critiques a recent proposal that time crystal models could explain dark energy, highlighting an instability that causes the energy density to become negative, thus questioning its viability.

Contribution

It identifies a fundamental instability in the proposed time crystal dark energy model, challenging its suitability for explaining dark energy.

Findings

The model exhibits an instability leading to negative energy density.

The instability questions the model's physical viability.

The critique suggests the need for more stable dark energy models.

Abstract

It was recently proposed (arxiv:2502.08887) that the time crystal Lagrangian introduced by Shapere and Wilczek in 2012 could be a model of dark energy. I point out that the model has an instability that drives its energy density to negative values, which may render it unsuitable as a model of dark energy.