# Hunting for extra dimensions in the shadow of M87*

## TL;DR

This paper uses the M87* black hole shadow image to set constraints on extra-dimensional theories, specifically limiting the AdS$_5$ curvature radius in the Randall-Sundrum model to less than approximately 170 AU.

## Contribution

It introduces a novel method to constrain extra dimensions using black hole shadow observations, providing one of the first quantitative bounds from such astrophysical data.

## Key findings

- Limits the AdS$_5$ curvature radius to $ extless 170$ AU based on M87* shadow
- Demonstrates the shadow's shape constrains deviations from Kerr black hole models
- Provides new astrophysical bounds on exotic higher-dimensional physics

## Abstract

The Event Horizon Telescope has recently provided the first image of the dark shadow around the supermassive black hole M87*. The observation of a highly circular shadow provides strong limits on deviations of M87*'s quadrupole moment from the Kerr value. We show that the absence of such a deviation can be used to constrain the physics of extra dimensions of spacetime. Focusing on the Randall-Sundrum AdS$_5$ brane-world scenario, we show that the observation of M87*'s dark shadow sets the limit $\ell \lesssim 170\,{\rm AU}$, where $\ell$ is the AdS$_5$ curvature radius. This limit is among the first quantitative constraints on exotic physics obtained from the extraordinary first ever image of the dark shadow of a black hole.