Speaker
Description
In the past decade, black holes evolved from a theoretical prediction by General Relativity to actually observable objects. In particular, accretion and outflow of plasma leave key signatures across the electromagnetic spectrum, from the Event Horizon Telescope radio observations to X- and γ-rays, from the shadow size to the shape of the spectral energy distribution (SED). These signatures allow to test gravity because extended theories typically predict the presence of black hole mimickers, i.e., objects of similar compactness but without an event horizon.
In this talk, based on state-of-the-art GRMHD simulations, I will contrast Sgr A observations with the multiwavelength appearance of compact objects predicted by Quadratic Gravity, the unique extension of General Relativity to capture first-order manifestations of quantum gravity. Constraining the allowed parameter range of black hole mimickers implies identifying the viable parameter range of quantum-gravity theories. Indeed, our simulations of accretion and outflow attribute some of these black hole mimickers with properties incompatible with multiwavelength observations of Sgr A, e.g., the absence of a central brightness depression (“shadow”) for EHT observations and a strong X-ray flux exceeding the observed SED. This enables pioneering multiwavelength tests of gravity.
| Talk category | Plenary |
|---|---|
| Second preference | NOVA Network 3 |
