Vineeth Krishna (UMICH): New (Non-)Supersymmetric Phases in N=4 SYM | 9/13/2024
In this work, we extend our current understanding of the phase diagram of N=4 SYM at any given set of charges (Microcanonical Ensemble) by proposing various new phases. These new phases correspond to hairy black hole solutions in the bulk gravitational theory and are easier to construct and analyze due to the emergence of a "Non-interacting" picture. The new phases continue to exist even in the supersymmetric limit and contribute to an extra parameter (amount of "hair") worth of solutions. The presence of new supersymmetric solutions predicts a phase transition in the superconformal index of N=4 SYM.
Emil Martinec (UChicago): Fivebrane Stars | 9/20/2024
We revisit a construction due to Lunin and Mathur of 1/2-BPS solutions of string theory involving fivebranes, which are the magnetic duals of fundamental strings; and interpret the generic solution as describing a “fivebrane star”. The effective field theory governing these objects provides insights into gravitational collapse and black hole formation.
Nathan Benjamin (USC): Angular fractals in thermal CFT | 9/27/2024
I will discuss universal properties of thermal partition functions at high temperature and large angular fugacity, in d>2 CFTs. This provides spin-refined information -- namely the statistics of spins of local operators -- valid for all conformal field theories, that in some sense generalizes modular invariance of d=2 CFTs. Based on arXiv:2405.17562.
Yifan Wang (NYU): Fusing conformal defects in higher dimensions | 10/4/2024
We study operator algebra of extended conformal defects in more than two spacetime dimensions. Such algebra structure encodes the combined effect of multiple impurities on physical observables at long distances as well as the interactions among the impurities. These features are formalized by a fusion product which we define for a pair of defects, after isolating divergences that capture the effective potential between the defects. These divergences generalize the usual Casimir energy and define a novel effective field theory for defects. We discuss general properties of the corresponding fusion algebra and give explicit examples. We also derive universal formulas for defect structure constants from the defect effective field theory.
Bibhushan Shakya (DESY): Cosmic Colliders: High Energy Physics with First Order Phase Transitions | 10/25/2024
Vacuum decay through runaway first order phase transitions (FOPTs) presents a unique opportunity for particle physics and cosmology: collisions of vacuum bubbles can act as cosmic scale high energy colliders close to the Planck scale, providing access to high energy physics far beyond any temperature or energy scale ever reached in the history of our Universe. This talk will cover recent developments and challenges in the physics for understanding such frameworks, as well as applications to solve some of the fundamental problems in particle physics: the production of dark matter and the baryon asymmetry of the Universe.
Mirjam Cvetic (UPenn): Generalized Global Symmetries in Quantum Field Theory and Nested Symmetry Theories | 11/8/2024
Generalized Global Symmetries of D-dimensional Quantum Field Theories (QFTs) can be interpreted in terms of (D+1)-dimensional bulk Symmetry Theory (SymTh), which often turns out to be a gapped Symmetry Topological Field Theory (SymTFT). In this setting interacting degrees of freedom arise as edge modes of a higher-dimensional bulk system. We further show that the combined (D + 1)-dimensional bulk and D-dimensional edge mode theory can serve as the edge modes of a (D+2)-dimensional bulk theory, which leads to a nested structure of SymThs. We show how this structure naturally arises in a number of string-based constructions of QFTs with both discrete and continuous symmetries.
Kevin Zhang (Utah): Neural Networks, Scaling Laws and Effective Field Theories | 11/15/2024
Starting from simple curve fitting problems, I will explain how modern AI works by learning a large number of features from data: wide neural networks fit data to linear combinations of many random features, and stacking layers to form deep neural networks allows the features to evolve according to data. It has been empirically observed that the performance of neural networks scales as power laws with respect to the sizes of the model and training data set. I will discuss a recently proposed random feature model that captures the physics of neural scaling laws, and its solution in an effective theory framework using large-N field theory methods. The solution reveals a duality that is indicative of a deeper connection between neural networks and field theories.
Pierre Heidman (Ohio State): The Microstructure of the Schwarzschild Black Hole | 11/22/2024
Understanding the microscopic structure of black holes has been a central goal in string theory. While significant progress has been made for supersymmetric solutions, a key question remains: what is the microstructure of the Schwarzschild black hole, the simplest solution in General Relativity? In this talk, we will introduce a new approach to account for the entropy of the Schwarzschild black hole through branes and antibranes in string theory. We will explore recent progress in constructing Schwarzschild microstates in supergravity, which appear as smooth, horizonless geometries that deviate from the Schwarzschild black hole in the near-horizon region.
Matt Strassler (Harvard): Illuminating the Dark Forests of the Hidden Valley Scenario | 12/6/2024
In the Hidden Valley/Dark Sector scenario, which has various theoretical motivations, a hidden sector couples to the Standard Model at TeV scales or below. A wide variety of exotic phenomena may result, posing serious experimental and/or theoretical challenges. The main theoretical hurdle is that hidden sectors may host phenomena that we cannot currently calculate or simulate, thereby making predictions difficult or impossible. I'll discuss a couple of projects at the frontiers of this subject.
