On my upcoming European lecture tour (on which I will soon post more), I will be giving the following talk on 7 March at LSE’s Sigma Club and on 9 March in the physics and philosophy colloquium at the University of Bristol:
“To the Planck scale and back: On the emergence of spacetime in quantum theories of gravity”
Abstract: Among the most striking features of most approaches to quantum gravity is their claim that spacetime as we know and love it disappears in one form or another from the fundamental furniture of the world. I shall explicate this disappearance, using the examples of loop quantum gravity and causal set theory. For any quantum theory of gravity to succeed, it must offer an explanation of how the smooth, classical spacetimes of general relativity re-emerge in the appropriate low-energy limit of the fundamental theory. I will show how similar philosophical and technical problems arise in the case of spacetime as they do for the emergence of classicality from ordinary quantum mechanics. The case at hand, however, poses the additional threat of empirical incoherence, as the absence of space and time deprives us of apparent prerequisites for the empirical testing of physical theories.