Model independent measurement of the growth rate from the consistency relations of the LSS

TL;DR

This paper proposes a model-independent method to measure the growth rate of cosmic structures using consistency relations between the bispectrum and power spectrum, validated with simulations and forecasted for Euclid-like surveys.

Contribution

It introduces a novel, exact, and model-independent approach to extract the growth rate and bias from large-scale structure data without relying on theoretical approximations.

Findings

Method successfully breaks the bias-growth rate degeneracy.

Simulations confirm the method's accuracy for dark matter and haloes.

Forecasts indicate <10% measurement precision for Euclid-like surveys.

Abstract

The Consistency Relations for the Large Scale Structure provide a link between the amplitude of Baryonic Acoustic Oscillations in the squeezed bispectrum (BS) and in the power spectrum (PS). This relation depends on the large scale bias of the considered tracer, $b_\alpha$, and on the growth rate of structures, $f$. Remarkably, originating from basic symmetry principles, this relation is exact and independent on the underlying cosmological model. By analysing data from large volume simulations, both for dark matter and for haloes, we illustrate how BS and PS measurements can be used to extract $b_\alpha$ and $f$ without the need of any theoretical approximation scheme for the computation of the BS and the PS. We show that, combining measurements of the squeezed BS with the quadrupole to monopole ratios for the PS at large scales can successfully break the $b_\alpha -f$ degeneracy. We forecast that this method, applied to a Euclid-like survey, will be able to measure bias, and then the growth rate, at better than $10\%$ level, with no extra assumption.