Speaker: Bianca Dittrich, Perimeter Institute

Title: From space-time atoms to gravitational waves

Abstract: Is spacetime smooth, or is it — like matter — built from fundamental atoms? Spin foams are an approach to quantum gravity based on the latter idea: spacetime atoms, glued together, form quantum spacetime. A central difficulty in the field has been to understand this gluing, as it determines whether spin foams reproduce, in the continuum and semi-classical limit, a smooth spacetime governed by Einstein's equations — and in particular whether they support gravitational waves. I will describe a series of works showing that, assuming the theory admits a continuum limit to smooth spacetimes, the resulting dynamics does admit gravitational waves. Remarkably, these waves carry a quantum gravitational imprint, and I will argue that this leads to an observable which is measurable, although only in principle. 

Refreshments at 3:45pm in Lewis 104