Cosmological perturbations in the energy-momentum squared gravity theory: constraints from gravitational wave standard sirens and redshift space distortions

TL;DR

This paper studies linear cosmological perturbations in energy-momentum squared gravity, analyzing gravitational wave propagation and matter growth, and constrains model parameters using GW and redshift space distortion data, showing good observational agreement.

Contribution

It derives perturbation equations for EMSG models and constrains their parameters with observational data, highlighting their viability as alternatives to standard cosmology.

Findings

Model parameters are small and positive within 1σ confidence

EMSG can reproduce background cosmology similar to ΛCDM

Good agreement with gravitational wave and redshift space distortion data

Abstract

We investigate the linear cosmological perturbations in the context of the so-called energy-momentum squared gravity (EMSG) theory. Recent researches show that the EMSG theory can reproduce viable background cosmological evolution comparable to $\Lambda$CDM, while the matter-dominated era exhibits slight distinctions. In this paper, we mainly focus on the power-law EMSG models and derive the equations for the linear cosmological perturbations. We explore the propagation of the gravitational wave (GW) and the growth of matter density perturbation at the first order, and estimate the model parameters from the simulated GW data and the observed redshift space distortion data. Our analysis reveals that the model parameters should be small and positive in $1\sigma$ confidence interval, which indicates that the theory is in good agreement with the observational data and can be regarded as an alternative for the standard cosmological model.