Comment on [arXiv:1106.1417] "Small Lorentz violations in quantum gravity: do they lead to unacceptably large effects?"

TL;DR

This paper critiques recent claims that small Lorentz violations in quantum gravity could lead to large observable effects, arguing that most models are incompatible with low-energy tests unless based on supersymmetry.

Contribution

It provides a critical analysis showing that most Lorentz-violating quantum gravity models are ruled out by existing low-energy experiments, except those involving supersymmetry.

Findings

Most Lorentz-violating models are incompatible with low-energy tests.

Supersymmetry-based models remain viable.

The critique challenges the validity of recent analyses on Lorentz violations.

Abstract

A recent paper by Gambini, Rastgoo and Pullin [arXiv:1106.1417 investigates the important issue of constraints from Lorentz invariance on Planck scale physics, arguing that the classic analysis of Collins, Perez, Sudarsky, Urrutia and Vucetich \cite{cpsuv} is not generally valid. We argue that the new work is based on models that do not capture the relevant physics, and that almost all models of observable high energy Lorentz violation, and proposed Lorentz-violating theories of quantum gravity, are ruled out by low energy tests; the only known exceptions are based on supersymmetry.