Speaker
Description
Quantum gravity is usually associated with distances near the Planck scale, seemingly far beyond direct experimental reach. But horizons—from black holes to the early Universe and the cosmological horizon—may provide enormous amplifiers of microscopic physics. I will begin with a pedagogical overview of how observations of these systems can turn questions about quantum gravity into falsifiable ones.
I will then focus on a concrete example in the early Universe. In quadratic gravity, asymptotic freedom at high energies and the quantum running of gravitational couplings can dynamically generate a period of slow-roll inflation. Remarkably, the same running connects a UV-complete theory of gravity to CMB observables and predicts a tensor-to-scalar ratio large enough to be tested by forthcoming experiments.
I will next discuss two complementary windows on horizon-scale quantum physics. Near black holes, quantum modifications may produce departures from the Kerr no-hair paradigm and delayed gravitational-wave echoes, providing targets for LISA, next-generation gravitational-wave detectors, and horizon-scale imaging. On the largest cosmological scales, current data allow—and mildly favour—a percent-level mismatch between the strength of gravity measured locally and cosmologically, a “cosmic glitch” that can mimic aspects of dynamical dark energy.
I will close by asking whether these apparently disparate phenomena could be telling us something common about quantum horizons, and what observations over the coming decade could do to distinguish such ideas from conventional extensions of general relativity.