Quantum Fields and Strings

Recently there has been significant interest in energy-energy correlators which measure the energy flux created at the point of collision by calorimeter-like detectors at asymptotically large distances. The primary building blocks of these observables are Average Null Energy operators (ANECs) which bear a strong resemblance to part of the charges associated to the symmetries of asymptotically flat spacetimes. In this talk, I will elucidate that relationship and show that calculable quantities that are more familiar in discussions of asymptotic symmetries and flat-space holography can be written in terms of energy-energy correlators, thereby allowing for natural connections to observables at particle experiments.

I will present a complex matrix model (CMM) for the computation of protected two-point and three-point correlation functions of 1/2-BPS operators. The model can be efficiently studied in large N limit for huge operators (with dimensions ~N^2). An advantage of this approach is the direct identification of the distribution of eigenvalues of complex matrix with the shapes of droplets in Lin-Lunin-Maldacena (LLM) bubbling geometry. For correlators of two huge operators with a small SO(4) symmetric "probe" operator (with dimension N^0) we established a perfect correspondence with old computations of Skenderis-Taylor in dual LLM gravity. CMM allows efficient analytic study of certain two- and three-point correlators of huge operators of exponential and coherent state types and relates these problems to the Laplacian growth and 2d quantum gravity. We also compute explicitly the correlators of two huge operators with giant magnon operator. In a much more difficult case of 1/4- and 1/8-BPS operators we make a curious observation of equivalence of a pair correlator of such coherent state operators to the quenched Eguchi-Kawai reduction of the principal chiral model.

 In this talk I'll explain how to take a well-defined flat-space limit of brane models of AdS coupled to a non-gravitating bath. In the dual BCFT this amounts to a triple-scaling limit where both the number of boundary degrees of freedom and the boundary coupling are taken to infinity while the BCFT boundary piecewise approaches a lightcone. The resulting construction offers a new approach to study the relation between the flat limit of AdS and Carrollian/Celestial CFT, as well as the potential to carry over ideas from AdS/CFT to flat space. I will discuss some implications for entanglement entropy in flat space, in particular the fact that two different notions of entanglement entropy arise on scri, depending on whether one traces out modes which have left through scri.