Remnant Symmetry, Propagation and Evolution in f(T) Gravity

TL;DR

This paper clarifies that the presence of remnant symmetry in f(T) gravity does not resolve its known issues like superluminal propagation and acausality, but actually supports the theory's problematic nature.

Contribution

The paper clarifies misconceptions about remnant symmetry in f(T) gravity and demonstrates that it does not eliminate the theory's pathologies, reinforcing its problematic aspects.

Findings

Remnant symmetry exists in f(T) gravity.

Remnant symmetry does not fix superluminal propagation.

Remnant symmetry supports the theory's issues.

Abstract

It was recently argued that f(T) gravity could inherit "remnant symmetry" from the full Lorentz group, despite the fact that the theory is not locally Lorentz invariant. Confusion has arisen regarding the implication of this result for the previous works, which established that f(T) gravity is pathological due to superluminal propagation, local acausality, and non-unique time evolution. We clarify that the existence of the "remnant group" does not rid the theory of these various problems, but instead strongly supports it.