Abstract:  We construct algebras of diff-invariant observables in a global de Sitter universe with two observers and a free scalar QFT in two dimensions. We work in the strict G_N→0 limit, but allow the observers to have an order one mass in cosmic units. The observers are fully quantized. In the limit when the observers have infinite mass and are … Read More

Abstract: I will address the question of how background independent target space physics emerges in string theory. The point of view I will take is to identify the configuration space of target space with the space of 2d worldsheet QFTs. On-shell configurations are identified with c=0 worldsheet theories (i.e. a c=26 matter sector), and non-conformal QFTs correspond to generic off-shell … Read More

I will discuss some work in progress computing the norm of the Hartle-Hawking state in the simple model of pure three-dimensional gravity with positive cosmological constant. To one-loop order and including the contributions from universes with sphere boundaries in the far future, the result appears to be exp(|Z|) with Z the sphere partition function of 3d gravity.

Abstract: In recent years, the Euclidean gravitational path integral has proven to be a reliable tool for studying quantum mechanical aspects of black holes. An important quantity that can help us probe whether black holes behave like conventional quantum mechanical systems is the supersymmetric index computed directly from the gravitational path integral. In this talk, I will discuss the issue … Read More

Abstract: In 2307.03707 we introduced a framework for random matrix theory (RMT) in AdS_3 quantum gravity and chaotic 2D CFTs that is manifestly conformal and modular invariant. On the CFT side this leads to a 2d CFT trace formula, analogous to the Gutzwiller trace formula for chaotic quantum systems, which we use to derive necessary and sufficient conditions for an … Read More

Abstract: The geometric entropy is a localized contribution to the entropy obtained using Euclidean gravity methods. In this talk, I will discuss the Hamiltonian flow generated by the geometric entropy operator in general theories of gravity using Lorentzian methods of the Peierls/Poisson brackets. I will discuss examples with higher derivative corrections to illustrate the general features of the geometric flow. … Read More

Semiclassical gravity is a description of gravitational physics in terms of local observables evolving on a classical spacetime manifold. This appears to be at odds with diffeomorphism invariance, which forbids the existence of truly local physical degrees of freedom. To resolve this, one needs to replace the standard notion of locality with a relational version, in which some of the … Read More

Abstract: In the AdS/CFT correspondence, a subregion of the CFT allows for the recovery of a corresponding subregion of the bulk known as its entanglement wedge. In some cases, an entanglement wedge contains a locally but not globally minimal surface homologous to the CFT subregion, in which case it is said to contain a python’s lunch. It has been proposed that … Read More

There is a lot of evidence that geometry is closely tied with complexity in holographic models of quantum gravity. While complexity is typically hard to pin down precisely, the Python’s Lunch conjecture (PLC) makes quantitative predictions for complexity that seem strong enough to be testable. I will present evidence that the PLC is not quantitatively accurate within various tensor network models, predicting … Read More

Abstract: We give further evidence that the matrix-tensor model studied in [arXiv:2308.03829] is dual to AdS3 gravity including the sum over topologies. This provides a 3D version of the duality between JT gravity and an ensemble of random Hamiltonians, in which the matrix and tensor provide random CFT2 data subject to a potential that incorporates the bootstrap constraints. We show how the Feynman rules of the ensemble … Read More