Comment on: Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy

TL;DR

This paper critiques a recent claim that primordial gravitational wave spectra can reveal vanishing dimensions in quantum gravity models, arguing that the claim is misleading and not as robust as suggested.

Contribution

The paper challenges the assertion that a cutoff in gravitational wave spectra is a generic signature of vanishing dimensions in quantum gravity.

Findings

The claim about the cutoff being a robust test is misleading.

Vanishing dimensions do not necessarily imply observable signatures in gravitational waves.

Abstract

It has been recently claimed [arXiv:1102.3434] that quantum gravity models where the number of dimensions reduces at the ultraviolet exhibit a potentially observable cutoff in the primordial gravitational wave spectrum, and that this is a "generic" and "robust" test for such models, since "(2+1)-dimensional spacetimes have no gravitational degrees of freedom". We argue that such a claim is misleading.