Distinguishing modified gravity models

TL;DR

This paper investigates how different modified gravity models with screening mechanisms can be distinguished through cosmological observations of fundamental constant variations and spectroscopic velocities, highlighting potential for future ELT-HIRES detection.

Contribution

It proposes a method to differentiate chameleon, K-mouflage, and Vainshtein models using low-redshift cosmological observations of fundamental constants and redshift-dependent velocities.

Findings

Unscreened regions show time variation of constants in chameleon models.

K-mouflage and Vainshtein models predict distinct spectroscopic velocity signatures.

Differences from $ ext{Lambda}$-CDM are detectable with future ELT-HIRES observations.

Abstract

Modified gravity models with screening in local environments appear in three different guises: chameleon, K-mouflage and Vainshtein mechanisms. We propose to look for differences between these classes of models by considering cosmological observations at low redshift. In particular, we analyse the redshift dependence of the fine structure constant and the proton to electron mass ratio in each of these scenarios. When the absorption lines belong to unscreened regions of space such as dwarf galaxies, a time variation would be present for chameleons. For both K-mouflage and Vainshtein mechanisms, the cosmological time variation of the scalar field is not suppressed in both unscreened and screened environments, therefore enhancing the variation of constants and their detection prospect. We also consider the time variation of the redshift of distant objects using their spectrocopic velocities. We find that models of the K-mouflage and Vainshtein types have very different spectroscopic velocities as a function of redshift and that their differences with the $\Lambda$-CDM template should be within reach of the future ELT- HIRES observations.