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arXiv · 2604.26690

Nonlinear Relativistic Effects on Cosmological Redshift Drift

Pierre Béchaz·Giuseppe Fanizza·Giovanni Marozzi·Matheus R. Medeiros Silva
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Abstract

Using a fully gauge-invariant approach, we compute for the first time in the literature relativistic effects on the redshift drift up to second order in cosmological perturbation theory. This is achieved by employing a set of light-cone coordinates that simplify the description of light propagation in an inhomogeneous and anisotropic universe. We show that redshift-space distortion occurs only as a second-order effect whereas, as known, it is not present among the linear perturbations. We then derive analytical expressions of the bispectrum for the leading-order perturbative contributions on sub-Hubble scales, providing some numerical evaluations. Our finding is that, at low redshift and for large momenta, the non-linearities in the bispectrum are enhanced more than the squared power spectrum.

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Pierre Béchaz, Giuseppe Fanizza, Giovanni Marozzi, Matheus R. Medeiros Silva. 2026-04-29. Nonlinear Relativistic Effects on Cosmological Redshift Drift. https://arxiv.org/abs/2604.26690

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