Thinking Effectively About Gravity
Prof. Cliff Burgess
Department of Physics & Astronomy, McMaster University and Perimeter Institute for Theoretical Physics
Thursday, October 29, 2026
4:00 p.m.
In-person: PHY 150
Abstract: We live in remarkable times: we have an extremely good Core Theory (the Standard Model plus General Relativity) that describes very accurately almost all observations that have been made. Yet there are a handful of observations it does NOT describe - so we know it cannot be the entire story – though these observations do not yet determine what the correct alternative must be. We also have plausible candidates for physics at the highest energies that can reconcile General Relativity with Quantum Mechanics and so might provide a framework in which to seek a way forward. This talk asks what this situation is likely telling us, building on a central organizing feature of Nature: decoupling (whose mathematical exploitation is captured by Effective Field Theories). Decoupling beautifully explains why low-energy measurements are insensitive to unknown high-energy details – which is why we do not have to understand everything at once (arguably why Science is possible at all). It also provides an important clue when seeking how to organize what we see. At first sight decoupling can seem obstructive, since it thwarts our ability to extract fundamental insights about higher energies from those indications of Core Theory failure coming from cosmology (the longest distances to which we have access). In this talk I argue why decoupling is actually a boon and not an obstacle, since a few UV features can penetrate the fog of decoupling in interesting ways and these seem to play important roles in what we see in cosmology.