Non-zero density-velocity consistency relations for large scale structures

TL;DR

This paper derives exact kinematic consistency relations linking density and velocity fields in cosmology, enabling measurements of large-scale structure dynamics at equal times, which can test fundamental physics and bias models.

Contribution

It introduces non-zero density-velocity consistency relations valid at equal times, relying solely on the weak equivalence principle and Gaussian initial conditions.

Findings

Relations remain valid in the non-linear regime

Applicable to biased galaxy fields

Can constrain non-standard cosmologies

Abstract

We present exact kinematic consistency relations for cosmological structures that do not vanish at equal times and can thus be measured in surveys. These rely on cross-correlations between the density and velocity, or momentum, fields. Indeed, the uniform transport of small-scale structures by long wavelength modes, which cannot be detected at equal times by looking at density correlations only, gives rise to a shift in the amplitude of the velocity field that could be measured. These consistency relations only rely on the weak equivalence principle and Gaussian initial conditions. They remain valid in the non-linear regime and for biased galaxy fields. They can be used to constrain non-standard cosmological scenarios or the large-scale galaxy bias.