Event Horizon Telescope observations exclude compact objects in baseline mimetic gravity

TL;DR

Event Horizon Telescope observations challenge the baseline mimetic gravity theory by showing that its predicted black hole shadows are inconsistent with actual astronomical data, thus constraining its viability for explaining dark matter and dark energy.

Contribution

This study demonstrates that the baseline mimetic gravity model predicts black hole shadows incompatible with EHT observations, providing new constraints on the theory.

Findings

Naked singularity in mimetic gravity does not produce a shadow.

Black hole in mimetic gravity casts a shadow too small compared to observations.

EHT images of M87* and Sgr A* exclude the baseline mimetic gravity model.

Abstract

Mimetic gravity has gained significant appeal in cosmological contexts, but static spherically symmetric space-times within the baseline theory are highly non-trivial: the two natural solutions are a naked singularity and a black hole space-time obtained through an appropriate gluing procedure. We study the shadow properties of these two objects, finding both to be pathological. In particular, the naked singularity does not cast a shadow, whereas the black hole casts a shadow which is too small. We argue that the Event Horizon Telescope images of M87$^{\star}$ and Sgr A$^{\star}$ rule out the baseline version of mimetic gravity, preventing the theory from successfully accounting for the dark sector on cosmological scales. Our results highlight an interesting complementarity between black hole imaging observations and modified gravity theories of cosmological interest.