Seth Koren (Notre Dame): Generalized Global Symmetries and Nonperturbative Quantum Flavodynamics | 9/11/2024
Generalized global symmetries are present in theories of particle physics, and understanding their structure can give insight into these theories and UV completions thereof. We will identify noninvertible chiral symmetries in certain flavorful Z' extensions of the Standard Model, and our understanding of generalized symmetry breaking will lead us to short-distance theories of gauged non-Abelian flavor where nonperturbative effects can resolve important naturalness questions. For the leptons we will find naturally exponentially small Dirac neutrino masses, and in the quark sector we will construct a massless down-type quarks solution to strong CP in color-flavor unification. Intriguingly, the fact that we have three generations of fermions plays a crucial role in the existence of these noninvertible symmetries.
Sam Leutheusser (IAS): Superadditivity and the performance of quantum tasks in large N field theories and holography | 9/25/2024
Holographic conformal field theories exhibit dramatic changes in the structure of their operator algebras in the limit where the number of local degrees of freedom (N) becomes infinite. An important example of such phenomena is the violation of the additivity property for algebras associated to local subregions. I will first review several examples of superadditive algebras in quantum field theory and then investigate their consequences in the context of holographic duality. As an important application, I will demonstrate how superadditivity of local algebras is intimately related to the ability of holographic field theories to perform quantum tasks that would naievely be impossible. Finally, I will argue that the connected wedge theorems (CWTs) of May, Penington, Sorce, and Yoshida, which characterize holographic protocols for quantum tasks, can be re-phrased in terms of superadditive algebras. This re-phrasing allows for a potential generalization of the CWTs into an equivalence statement.
Yiming Chen (Stanford): Fortuity and Chaos of BPS states | 10/2/2024
It was recently suggested that holographic BPS states can be divided into two categories: monotone and fortuitous. Various pieces of evidence suggest that monotone states correspond to horizonless microstate geometries, while fortuitous states are dual to supersymmetric black holes. In this talk, I will connect this classification to the fine-grained features of BPS states using concepts from quantum chaos. In concrete models such as the N=4 SYM theory, explicit calculations demonstrate that monotone states are only weakly chaotic, whereas fortuitous states can exhibit strong chaos due to an “invasion” mechanism. I propose using the N=2 SUSY SYK model as a toy model to explore many of these ideas.
Hirosi Ooguri (Caltech): Two Exact Results on 2d CFTs | 10/23/2024
As I will discuss in my Ta-You Wu Lecture, exact statements about conformal field theories can be used to identify and derive constraints on quantum gravity theories. In this technical talk, I will present a couple of new results on conformal field theory in two dimensions motivated by gravitational theories in three dimensions.
Matthew Dodelson (Harvard): Quasinormal ringdown in the SYK model | 10/30/2024
Thermal correlators in large N systems equilibrate at late times, but the precise late-time behavior is unknown away from holographic and free field limits. In this talk I will analyze this problem in the case of the SYK model away from the low-temperature limit, finding a discrete spectrum of quasinormal modes. The basic technique is a resummation of perturbation theory which is reminiscent of the double cone construction. We will also discuss the interpretation of the result in terms of a dual stringy black hole.
Sam van Leuven (Witswaterrand): 4d modularity | 11/6/2024
Modular invariance plays an important role in the study of two-dimensional CFTs. Most famously, it exhibits the universality of CFT spectra at high energy, but there are numerous other applications, including in the context of holography. In recent years, a combination of exact results in supersymmetric CFTs and developments in AdS/CFT have sparked renewed interest in possible generalizations of modularity to CFTs in dimensions greater than two. We briefly survey these developments for both supersymmetric and non-supersymmetric CFTs and note that a satisfactory geometric understanding is lacking. We aim to improve on this situation in the context of the 4d N=1 superconformal index, using the free chiral multiplet as our main example. We argue that a factorization of the BPS Hilbert space allows a KK reduction on the base of the Hopf fibration to a two-dimensional torus, comprised of the Hopf fiber and the temporal circle. This provides a 2d description, in terms of two infinite KK towers, of the 4d BPS Hilbert space. We argue, and prove, that this implies the unconventional modular property of the superconformal index, referred to before as “modular factorization”. We comment on the generalized notion of modularity, on generalizations to more interesting 4d SCFTs and other dimensions. If time permits, we discuss an SL(2,Z) family of 3d limits of the 4d index, realizing lens space partition functions of the dimensionally reduced theory.
William DeRocco (UMaryland/John Hopkins): Exploring the dark side in the era of Roman | 11/13/2024
Gravitational microlensing is one of the most sensitive methods we have to search for macroscopic dark matter. NASA’s upcoming Roman Space Telescope will dramatically advance this search by performing a comprehensive microlensing survey of the Galactic Bulge at sensitivities orders of magnitude stronger than existing telescopes. Its unprecedented sensitivity will provide the opportunity to search for dark matter across a wide range of unexplored parameter space; however, it will also pose new challenges, including an irreducible astrophysical background in the form of free-floating planets. In this talk, I will discuss how population-level modeling can help mitigate this background and open the potential for Roman to make a first discovery of macroscopic dark matter in our galaxy.
Vladimir Narovlansky (IAS): An SYK-like model with curious low energy behavior | 11/20/2024
I will discuss a disordered quantum mechanical model with interesting low energy dynamics differing from what we have in SYK. One motivation for this model is to describe black holes in Einstein gravity in higher dimensions. Indeed, the equations of this model generalize an uncontrolled truncation of the BFSS model, but correctly describe the large N limit of our model. The entropy at low energies has a non-trivial scaling with temperature, with an exponent that we calculate, and we will discuss additional unusual low temperature features in this model. We study the possibility of a spin glass phase which has been suggested in the past in a similar context.
Carlos Perez (UTexas): Entanglement Islands in Braneworlds | 12/4/2024
The information paradox has been a long-standing problem in black hole physics. Recent proposals suggest that a region called an "island" contributes to the entanglement entropy of black hole radiation. Lower-dimensional models demonstrate that the inclusion of this region reproduces the so-called Page curve for the entropy of radiation. However, in higher dimensions, all models attempting to reproduce these results include a massive graviton. In this talk, I will discuss these higher-dimensional models, presenting the associated issues and how they suggest the use of tools from holography to construct swampland criteria for braneworlds as effective field theories.
