Rescuing constraints on modified gravity using gravitational redshift in large-scale structure

Understand

The distribution of galaxies provides an ideal laboratory to test for deviations from General Relativity.

• In particular, redshift-space distortions are commonly used to constrain modifications to the Poisson equation, which governs the strength of dark matter clustering.
• Here, we show that these constraints rely on the validity of the weak equivalence principle, which has never been tested for the dark matter component.
• Relaxing this restrictive assumption leads to modifications in the growth of structure that are fully degenerate with modifications induced by the Poisson equation.