Consistency of Relevant Cosmological Deformations on all Scales

TL;DR

This paper demonstrates that relevant cosmological deformations of gravity remain consistent at the linear level across all scales, ensuring no unitarity violations and extending the classical self-protection mechanism throughout the entire kinematic domain.

Contribution

It proves the linear-level consistency of relevant gravitational deformations across all scales, confirming the extension of the self-protection mechanism.

Findings

Absence of unitarity-violating negative norm states

Consistency of deformations from sub- to super-Hubble scales

Extension of the self-protection mechanism to all scales

Abstract

Using cosmological perturbation theory we show that the most relevant defor- mation of gravity is consistent at the linear level. In particular, we prove the absence of uni- tarity violating negative norm states in the weak coupling regime from sub- to super-Hubble scales. This demonstrates that the recently proposed classical self-protection mechanism of deformed gravity extends to the entire kinematical domain.