K-mouflage Imprints on Cosmological Observables and Data Constraints

TL;DR

This paper explores how K-mouflage modified gravity models impact cosmological observations, compares their predictions with data, and derives constraints, showing they can alleviate some tensions in current cosmological measurements.

Contribution

It introduces and tests two K-mouflage scenarios against various datasets, providing new bounds on model parameters and highlighting their potential to resolve cosmological tensions.

Findings

K-mouflage models can ease the Hubble tension.

Constraints on model parameters are comparable to solar system tests.

Future probes could tighten these constraints significantly.

Abstract

We investigate cosmological constraints on K-mouflage models of modified gravity. We consider two scenarios: one where the background evolution is free to deviate from $\Lambda$CDM (K-mouflage) and another one which reproduces a $\Lambda$CDM expansion (K-mimic), implementing both of them into the EFTCAMB code. We discuss the main observational signatures of these models and we compare their cosmological predictions to different datasets, including CMB, CMB lensing, SNIa and different galaxy catalogues. We argue about the possibility of relieving the $H_0$ and weak lensing tensions within these models, finding that K-mouflage scenarios effectively ease the tension on the Hubble Constant. Our final 95\% C.L. bounds on the $\epsilon_{2,0}$ parameter that measures the overall departure from $\Lambda$CDM (corresponding to $\epsilon_{2,0}=0$) are $-0.04\leq \epsilon_{2,0} <0$ for K-mouflage and $0< \epsilon_{2,0} <0.002$ for K-mimic. In the former case the main constraining power comes from changes in the background expansion history, while in the latter case the model is strongly constrained by measurements of the amplitude of matter perturbations. The sensitivity of these cosmological constraints closely matches that of solar system probes. We show that these constraints could be significantly tightened with future ideal probes like CORE.