String Theory Seminar Series

Except where otherwise noted, seminars are held on Tuesdays at 11 a.m. in Abelson 307 (directions to Abelson). The length of the talk depends on the mode of presentation: 60 minutes for a computer talk and 80 minutes for a blackboard talk.

Please note: There are currently no seminars scheduled for Oct. 29 and Nov. 26.

Fall 2019 Seminars

Edgar Shaghoulian, Cornell University

September 6, 2019

Quantum Gravity in a Finite Box

Stefan Stanojevic, Brown University

September 10, 2019

All-Loop Singularities of Scattering Amplitudes in Massless Planar Theories

Djordje Radicevic, Brandeis University

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.

Xi Yin, Harvard University

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.

Shu-Heng Shao, Institute for Advanced Study, Princeton University

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.

Albion Lawrence, Brandeis University

October 8, 2019

Hamiltonian fluid dynamics and the quasilinear approximation

Andrea Dei, ETH Zürich

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.

Matthew Headrick, Brandeis University

October 22, 2019

Topic TBA

Thomas Faulkner, University of Illinois

November 5, 2019

Topic TBA

Jennie Traschen, UMass Amherst

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/δTb as well as in the curve δS/δTb, 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.

Juan Pedraza, University of Amsterdam

November 19, 2019

Topic TBA

Mark Hertzberg, Tufts University

December 3, 2019

Topic TBA

Hong Liu, Massachusetts Institute of Technology

December 10, 2019

Topic TBA