Unless noted otherwise, all seminars are on Tuesdays in Room SPL 52 at 3:30pm.

Date Speaker (Affiliation) and Title
Sep 6 Michael Dine (UCSC): Revisiting some questions about QCD at Large N:  $\theta$ and the $\eta^\prime$
Sep 13 Apratim Kaviraj (IIS)
Sep 20  
Sep 27  
Oct 4 Liam Fitzpatrick (BU) “On Information Loss in AdS3/CFT2”
Oct 11 Walter Tangarife (Tel Aviv U) “Relaxed Inflation”
Oct 18  
Oct 25  
Nov 1 Massimo Porrati (NYU)
Nov 8

Dan Roberts (IAS) “Chaos and complexity by design”

Abstract: Motivated by black hole physics, we study the relationship between quantum chaos, holographic complexity, and fined grained notions of randomness. First, we develop a diagnostic of quantum chaos by directly considering the time evolution of a simple local operator. This leads us to out-of-time-order correlation functions as natural probes of the butterfly effect. Next, we attempt to understand when random unitary operators can be used to approximate chaotic dynamics and how the quantum circuit complexity of such operators can grow. Quasi-periodically, we will return to holography and connect these results to a recent conjecture that the complexity of a holographic state is related to the black hole interior.

Nov 15

Greg Moore (Rutgers) “Three Projects Using Lattices, Modular Forms, K3-Surfaces,
And String Theory”

Abstract: Part 1 begins with a very brief review of Moonshine - old and new. I will then describe some special points (called CSS points) in the toroidal compactifications of heterotic strings with large (but finite) symmetry groups that are naturally subgroups of the Conway group. Then I will, regrettably, conclude that a conjectured M24 Moonshine property of refined Gromov-Witten invariants of K3 surfaces is actually not present.  Part 2 will examine some applications of the CSS points in view of heterotic-typeII string duality. This will raise the question of the validity of a consistency condition for asymmetric orbifolds that has been used in string theory since 1987. I will argue that it has been misinterpreted.  Part 3 briefly describes the computation of Zamolodchikov volumes of moduli spaces of 2d CFT’s associated to symmetric products of K3 surfaces, as well as the motivation for this computation from questions regarding AdS/CFT duality. The talk is modular in the sense that I can stop after part 1 or part 2, depending on the time and interest of the audience.

Nov 22 Thanksgiving Break
Nov 29 Agnese Bissi (Harvard)
Dec 6

Sergei Dubovsky (Perimeter) “Yang-Mills Glueballs as Closed Bosonic Strings”

We put forward the Axionic String Ansatz (ASA), which provides a unified description for the worldsheet dynamics of confining strings in pure Yang–Mills theory both in D=3 and D=4 space-time dimensions. The ASA is motivated by the excitation spectrum of long confining strings, as measured on a lattice, and by recently constructed integrable axionic non-critical string models. According to the ASA, pure gluodynamics in 3D is described by a non-critical bosonic string theory without any extra local worldsheet degrees of freedom. We argue that this assumption fixes the set of quantum numbers (spins, P- and C-parities) of almost all glueball states. We confront the resulting predictions with the properties of approximately 1^2+2^2+3^2+5^2=39 lightest glueball states measured on a lattice and find a good agreement. On the other hand, the spectrum of low lying glueballs in 4D gluodynamics suggests the presence of a massive pseudoscalar mode on the string worldsheet, in agreement with the ASA and lattice data for long strings.

Dec 8

Xiaochuan Lu (UC Davis) (Note this is a Thursday) “Scale Anomalies in Conformal Field Theory”

We study scale anomalies in conformal field theories. We first use Euclidean position space to show that scale anomaly coefficients can be computed in terms of CFT data (dimensions and OPE coefficients). We give an explicit expression in the form of a sum over operators, and we show that the series is not positive-definite. We then use a different approach by coupling the CFT to a weakly-coupled probe quantum field in Minkowski space. The scattering amplitudes of the probe particles are sensitive to the scale anomaly, and the optical theorem then gives an expression for the scale anomaly coefficient in terms of a positive sum of states.

Dec 13

Mario Martone (Cincinnati) “Understanding the landscape of N=2 Super-conformal field theories”

In this talk I will argue that a systematic classification of 4d N=2 superconformal field theories is possible through a careful analysis of the geometry of their Coulomb branches. I will carefully describe this general framework and then carry out the classification explicitly in the rank-1, that is one complex dimensional Coulomb branch, case. We find that the landscape of rank-1 theories is still largely unexplored and make a strong case for the existence of many new rank-1 SCFTs, almost doubling the number of theories already known in the literature. The existence of 4 of them has been recently confirmed using alternative methods and others have an enlarged N=3, supersymmetry. 

While our study focuses on Coulomb Branch geometries, we can extract many more information about these SCFTs. I will spend the last part of my talk outlining what else we can learn and the extent in which our study can be complementary to other method to study SCFTs (Conformal Bootstrap above all!).