I will describe a complete, top-down example of celestial holography, based on recent work with Costello and Paquette. Our duality relates certain models of self-dual gauge theory and conformal gravity, placed on an asymptotically flat four-dimensional spacetime called Burns space, to a two-dimensional chiral algebra living on D1 branes in a topological string theory on twistor space.

What can be measured asymptotically in quantum field theory? Among the answers to this question are scattering amplitudes, but also a whole compendium of inclusive measurements, such as expectation values of gravitational radiation and out-of-time-ordered amplitudes. We show that these asymptotic observables can be related to one another through new versions of crossing symmetry. Assuming...

I will explain a new 2d gravity/matrix model duality. The bulk theory can be defined as a minimal string theory whose matter sector is given by timelike Liouville theory instead of a minimal model. The theory admits a dual description in terms of a double-scaled matrix integral whose leading density of states is given by the universal Cardy density of states in a 2d CFT of central charge c,...

I will explain a cohomology problem in the SU(N) maximal super-Yang-Mills theory which we expect to capture BPS black holes in AdS. I also explain the recent progress for the SU(2) theory.

I will review some recent developments that attempt to put modern mathematical tools and structural insights to effective use in physics. The focus will be on two such tools. The first is a perspective on superspace geometry that leads to powerful structural analogies between twisted theories (which encode the dynamics of particular BPS subsectors) and their untwisted parents. The second deals...

In this talk we will analyze renormalization group flows on d-dimensional planar defects, embedded in a D-dimensional conformal field theory. This general setup includes the case of quantum field theory with no defects ($D=d$), as well as defects of different dimensionality that are of interest in high energy and condensed matter physics. Using methods from quantum information theory, we will...

I will discuss the interplay between 2d de Sitter and supersymmetry in two concrete supergravity models coupled to superconformal field theories. Upon fixing a supersymmetric analogue of the Weyl gauge these theories can be viewed as supersymmetric extensions of timelike Liouville theory with N=1 and N=2 supersymmetry respectively. Supersymmetric timelike Liouville is well behaved in the UV...

We obtain all solutions of the Wheeler-DeWitt equation with positive cosmological constant for a closed universe in the large-volume limit. We define a natural norm on the solution space and thereby obtain a description of the Hilbert space of quantum gravity in an asymptotically de Sitter spacetime. This provides the finite G_N generalization of the Hilbert space constructed by Higuchi using...

In order to derive the classical string action from the worldsheet, it is necessary to take string theory off shell. This can be done by a prescription of Tseytlin, who proposed taking the worldsheet sphere QFT partition function and *differentiating* it with the log of the UV cutoff. I will explain why this strange prescription always gives the correct answers, for both the S-matrix and...

String amplitudes famously accomplish several extraordinary and interrelated mathematical feats, including an infinite spin tower, tame UV behavior, and dual resonance: the ability of the amplitude to be represented as a sum over a single scattering channel. But how unique are these properties to string amplitudes? In this talk, I will demonstrate that it is possible to construct infinite new...

To define an algebra of observables in quantum gravity in a way that is universal and does not depend on a background spacetime, one can consider the observables along the worldline of an observer, rather than the observables in a region of spacetime.

A long-standing problem in QFT and quantum gravity is the construction of an “IR-finite” S-matrix. Infrared divergences in scattering theory are intimately tied to the “memory effect” and the existence of an infinite number of “large gauge charges”. A suitable “IR finite” S-matrix requires the inclusion of states with memory (which do not lie in the standard Fock space). For QED such a...

There are several suggestions for an appropriate entry for quantum complexity in the holographic duality dictionary. The question is which notion of complexity and what is the precise duality. In this talk I endeavor to answer exactly this question for one, well studied, system. Krylov complexity has the signatures of quantum complexity at all time scales; it can be defined for operators or...