Uploaded November 2025 | Updated September 2026, 2 weeks ago
Speaker: Niayesh Afshordi (Perimeter Institute & University of Waterloo)
Abstract: Quadratic gravity—also known as Stelle gravity—stands out as (arguably) the unique renormalizable and diffeomorphism-invariant theory of gravity in four dimensions. Despite its historical dismissal due to the presence of ghost instabilities, recent developments in non-perturbative and/or non-standard quantization approaches have sparked renewed interest in its viability. In this talk, I will explore how quadratic gravity may provide a consistent ultraviolet (UV) completion of the Universe, specifically for the quantum structure of spacetime at the cores of black holes and the Big Bang. I will also discuss potential observational consequences that could bring these high-energy phenomena within the reach of current or future experiments.
Speaker: Niayesh Afshordi (Perimeter Institute & University of Waterloo)
Abstract: Quadratic gravity—also known as Stelle gravity—stands out as (arguably) the unique renormalizable and diffeomorphism-invariant theory of gravity in four dimensions. Despite its historical dismissal due to the presence of ghost instabilities, recent developments in non-perturbative and/or non-standard quantization approaches have sparked renewed interest in its viability. In this talk, I will explore how quadratic gravity may provide a consistent ultraviolet (UV) completion of the Universe, specifically for the quantum structure of spacetime at the cores of black holes and the Big Bang. I will also discuss potential observational consequences that could bring these high-energy phenomena within the reach of current or future experiments.
