Shadows and Light: Testing Lorentz Violation with M87*
This presentation explores how the Event Horizon Telescope's observations of M87* can test fundamental physics. The authors investigate strong gravitational lensing and black hole shadows in Einstein bumblebee gravity, a theory where Lorentz symmetry breaks down. By calculating how light bends around slowly rotating black holes in this modified framework and comparing shadow observables with M87* data, they derive constraints on Lorentz violation parameters, revealing how the most extreme objects in the universe can probe the foundations of spacetime symmetry.Script
The Event Horizon Telescope showed us the shadow of M87*, a supermassive black hole 55 million light-years away. But this image does more than capture gravity's most extreme arena. It can test whether the symmetries we assume govern spacetime actually hold near a black hole's edge.
The authors work within Einstein bumblebee gravity, where a vector field spontaneously breaks Lorentz symmetry. This produces a slowly rotating black hole solution that resembles the Kerr metric but carries a Lorentz violation parameter. The question becomes: can we see this violation in how the black hole bends light and casts its shadow?
Light circling close to the black hole's photon sphere offers the strongest probe of spacetime geometry.
Strong lensing happens when light makes multiple loops around the photon sphere before escaping. The authors use the Hamilton-Jacobi method to trace these paths, calculating deflection angles, image positions, magnification, and time delays. The Lorentz violation parameter shifts the photon sphere radius, altering every one of these observables. For a lens like M87*, the resulting image separations and brightness ratios encode information about whether Lorentz symmetry holds.
The shadow is the photon sphere projected onto the observer's sky. The authors model infalling accretion to compute specific intensity and extract shadow radius, distortion, area, and oblateness. Each quantity depends sensitively on the Lorentz violation parameter. By comparing these predictions with the Event Horizon Telescope's measurements of M87*, they derive constraints on how much Lorentz symmetry can be broken in this gravitational theory.
The results show that gravitational lensing and shadow observables are powerful diagnostics. The Lorentz violation parameter leaves measurable fingerprints in deflection angles, image separations, time delays, and shadow geometry. M87* and future targets like Sagittarius A* become laboratories for testing fundamental symmetries. If Lorentz violation exists in nature's gravitational sector, black hole shadows will eventually reveal it.
Black holes at the universe's edge now test the symmetries at physics' foundation. Visit EmergentMind.com to explore more research and create your own videos.
