High-Energy and Gravitational Theory Group

September 6, 2019

Quantum Gravity in a Finite Box

September 10, 2019

All-Loop Singularities of Scattering Amplitudes in Massless Planar Theories

September 17, 2019

Gauge Theories With Nonstandard Gauge Constraints

Abstract: Pure Yang-Mills theory obeys a local constraint given by the Gauss law div E = 0. Alternative gauge constraints are known to exist: the most notable example is provided by Chern-Simons theory. However, detailed explorations of theories with nonstandard gauge constraints in the UV (e.g. on a lattice) have not been performed until very recently, when their importance was affirmed on several different fronts. In this talk I will discuss two new classes of nonstandard gauge theories. The first class involves theories in arbitrary dimension that can be shown to dualize to theories of ordinary fermions (these are higher-dimensional exact bosonization dualities). The second class involves theories of fractons, pioneered by condensed matter and quantum information communities, which are some of the most interesting examples of gapped theories not described by any kind of conventional topological order.

September 24, 2019

D-instantons and the non-perturbative completion of c=1 string theory

Abstract: I will discuss the effect of ZZ instantons in c=1 string theory, which leads to a new proposal for the non-perturbative completion of the duality between c=1 string and the matrix quantum mechanics.

October 1, 2019

Anomalies and Bounds on Charged Operators

Abstract: We study the implications of ’t Hooft anomaly (i.e. obstruction to gauging) on conformal field theory, focusing on the case when the global symmetry is Z2. Using the modular bootstrap, universal bounds on (1+1)-dimensional bosonic conformal field theories with an internal Z2 global symmetry are derived. The bootstrap bounds depend dramatically on the ’t Hooft anomaly. In particular, there is a universal upper bound on the lightest Z2 odd operator if the symmetry is anomalous, but there is no bound if the symmetry is non-anomalous. We comment on the implication to the Weak Gravity Conjecture in AdS3.

October 8, 2019

Hamiltonian fluid dynamics and the quasilinear approximation

October 15, 2019

Different perspectives on AdS3/CFT2 holography

Abstract: I will discuss AdS3/CFT2 holography from the two perspectives of integrability and worldsheet CFT and comment on their relations and recent results. In particular, I will show how to match null-vector constraints on correlation functions and explain how some structure constants can be explicitly derived and matched on the two sides of the duality. This amounts to one of the very first holographic matches of non-protected AdS3/CFT2 correlators.

October 22, 2019

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November 5, 2019

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November 12, 2019

The Schottky Anomaly of de Sitter Black Holes

Abstract: Black holes with Λ > 0 (SdS) have fascinating properties that are distinct from the asymptotically flat or AdS cases, starting with the fact that there are two horizons in the spacetime, one black hole and one cosmological. The two horizons have different temperatures and the total gravitational entropy is the sum of the horizon areas. As a result, both the mass M and entropy S are bounded between minimum and maximum values. Intriguingly, there is an extremum in the specific heat δM/δT_b as well as in the curve δS/δT_b, which resemble the Schottky anomaly of a two level system in statistical mechanics. In this talk we investigate classical and quantum mechanical features of SdS thermodynamics that make it resemble the physics of a paramagnet. We start by showing that the Schottky behavior is to be expected for classical fluctuations based on the first laws for SdS black holes. Second, we present calculations of black hole and cosmological particle production in SdS and find that the quantum fluctuations share the behavior of classical ones.

November 19, 2019

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December 3, 2019

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December 10, 2019

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