Talks

I show how to make sense of physical probability even for a single atom at a single time in an otherwise empty universe. The ideas are in https://arxiv.org/abs/2404.12954 and http://arxiv.org/abs/2505.06983. As applied to the EPRB setup, probability defined in this way is perfectly local.

A statistical mechanics of geometry based on the quasi-local energy of constantly accelerating observers outside black holes is proposed. By assuming particle statistics for the geometric quanta, the geometry condenses in the large area limit, providing a quantum gravity cutoff for the entropy of the thermal atmosphere of geometric excitations. These excitations model the fluctuating ``shape of the black hole" and form an effectively two dimensional quantum thermal geometric atmosphere. The entropy from these ``Debye" excitations is proportional to the area. Prospects of for the observation of the fluctuations are briefly discussed.

Cosmological data is consistent with a positive cosmological constant. In this talk I discuss an approach pioneered by Smolin that uses a non-perturbative exact quantization of gavity with a cosmological constant in the Ashtekar formalism. I discuss follow up work by the Author and his collaborators that address some conceptual and potential physical predictions of this approach. I end with a discussion of Smolin's cosmic natural selection as a predictive mechanism which also had consequences in particular Anthrophic landscape realizations in string theory.

I will tell stories. About Lee's physics. About his insights that have shaped many of the ideas that we take for granted today. From the birth of Loop Quantum Gravity to the discreteness of physical space.

Recent advancements in tabletop experiments may offer the first empirical proof that gravity is not classical. In the first part of my talk, I will present two effects that overcome the current limitations of Newton potential phenomenology, involving generic quantum sources of gravity. These effects are derived using a field-basis formulation of linearised gravity, which is particularly suited for describing superposition of macroscopically distinct gravitational field configurations in the low energy regime. This formalism also offers a natural setting for exploring the gauge symmetries. In particular, I will discuss the construction of linearised quantum diffeomorphism transformations by extending the notion of quantum reference frames to quantum fields.