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Speaker: Julio Parra MartinezTitle: Title TBAVenue: CMSA Room G10Speaker: Julio Parra Martinez, Caltech |
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Speaker: James HalversonTitle: Unexpected Uses of Neural Networks: Field Theory and Metric FlowsVenue: CMSA Room G10Speaker: James Halverson (Northeastern University) Title: Unexpected Uses of Neural Networks: Field Theory and Metric Flows Abstract: We are now quite used to the idea that deep neural networks may be trained in a variety of ways to tackle cutting-edge problems in physics and mathematics, sometimes leading to rigorous results. In this talk, however, I will argue that breakthroughs in deep learning theory are also useful for making progress, focusing on applications to field theory and metric flows. Specifically, I will introduce a neural network approach to field theory with a different statistical origin, that exhibits generalized free field behavior at infinite width and interactions at finite width, and that allows for the study of symmetries via the study of correlation functions… |
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Speaker: Luca IliesiuTitle: Title TBAVenue: CMSA Room G10Colloquium Speaker: Luca Iliesiu |
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Speaker: Ruth BrittoTitle: Scattering amplitudes in quantum field theoryVenue: CMSA Room G10Speaker: Ruth Britto (Trinity College Dublin) Title: Scattering amplitudes in quantum field theory Abstract: Particle collider experiments require a detailed description of scattering events, traditionally computed through sums of Feynman diagrams. However, it is not practical to evaluate Feynman diagrams directly for all significant scattering processes. Moreover, adding all diagrams reveals many cancellations: scattering amplitudes in theories such as QCD take remarkably simple forms. This simplicity is a clue that the perturbative theory is perhaps best understood without reference to Feynman diagrams. In fact, it has recently become possible to explain some of this simplicity. I will show how to derive many amplitudes efficiently and elegantly, and propose taming the remaining complexity with ideas drawn from combinatorics and… |
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Speaker: Mete SonerTitle: Synchronization in a Kuramoto Mean Field GameVenue: CMSA Room G10Speaker: Mete Soner (Princeton University) Title: Synchronization in a Kuramoto Mean Field Game Abstract: Originally motivated by systems of chemical and biological oscillators, the classical Kuramoto model has found an amazing range of applications from neuroscience to Josephson junctions in superconductors, and has become a key mathematical model to describe self organization in complex systems. These autonomous oscillators are coupled through a nonlinear interaction term which plays a central role in the long term behavior of the system. While the system is not synchronized when this term is not sufficiently strong, fascinatingly, they exhibit an abrupt transition to a full synchronization above a critical value of the interaction parameter. We explore this system in the mean field formalism. We treat the system… |
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Speaker: Ning SuTitle: Conformal symmetry, Optimization algorithms and the Critical PhenomenaVenue: CMSA Room G10Speaker: Ning Su, University of Pisa Title: Conformal symmetry, Optimization algorithms and the Critical Phenomena Abstract: In the phase diagram of many substances, the critical points have emergent conformal symmetry and are described by conformal field theories. Traditionally, physical quantities near the critical point can be computed by perturbative field theory method, where conformal symmetry is not fully utilized. In this talk, I will explain how conformal symmetry can be used to determine certain physical quantities, without even knowing the fine details of the microscopic structure. To compute the observables precisely, one needs to develop powerful numerical techniques. In the last few years, we have invented many computational tools and algorithms, and predicted critical exponents of Helium-4 superfluid… |
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Speaker: Erez UrbachTitle: The stringblack hole transition in anti de Sitter spaceVenue: CMSA Room G10Speaker: Erez Urbach, Weizmann Institute of Science Title: The string/black hole transition in anti de Sitter space Abstract: String stars, or Horowitz-Polchinski solutions, are string theory saddles with normalizable condensates of thermal-winding strings. In the past, string stars were offered as a possible description of stringy (Euclidean) black holes in asymptotically flat spacetime, close to the Hagedorn temperature. I will discuss the thermodynamic properties of string stars in asymptotically (thermal) anti-de Sitter background (including AdS3 with NS-NS flux), their possible connection to small black holes in AdS, and their implications for holography. I will also present new “winding-string gas” saddles for confining holographic backgrounds such as the Witten model, and their relation to the deconfined phase of 3+1 pure… |
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Speaker: Netta EngelhardtTitle: The Black Hole Information Paradox: A Resolution on the Horizon?Venue: CMSA Room G10Speaker: Netta Engelhardt (MIT) Title: The Black Hole Information Paradox: A Resolution on the Horizon? Abstract: The black hole information paradox — whether information escapes an evaporating black hole or not — remains one of the most longstanding mysteries of theoretical physics. The apparent conflict between validity of semiclassical gravity at low energies and unitarity of quantum mechanics has long been expected to find its resolution in a complete quantum theory of gravity. Recent developments in the holographic dictionary, and in particular its application to entanglement and complexity, however, have shown that a semiclassical analysis of gravitational physics can reproduce a hallmark feature of unitary evolution. I will describe this recent progress and discuss some promising indications of… |
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Speaker: Tristan CollinsTitle: Complete Calabi-Yau metrics: Recent progress and open problemsVenue: CMSA Room G10Title: Complete Calabi-Yau metrics: Recent progress and open problems Abstract: Complete Calabi-Yau metrics are fundamental objects in Kahler geometry arising as singularity models or “bubbles” in degenerations of compact Calabi-Yau manifolds. The existence of these metrics and their relationship with algebraic geometry are the subjects of several long standing conjectures due to Yau and Tian-Yau. I will describe some recent progress towards the question of existence, and explain some future directions, highlighting connections with notions of algebro-geometric stability. |
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Speaker: David GamarnikTitle: From spin glasses to Boolean circuits lower bounds &#; Algorithmic barriers from the overlap gap propertyVenue: CMSA Room G10Speaker: David Gamarnik (MIT) Title: From spin glasses to Boolean circuits lower bounds. Algorithmic barriers from the overlap gap property Abstract: Many decision and optimization problems over random structures exhibit an apparent gap between the existentially optimal values and algorithmically achievable values. Examples include the problem of finding a largest independent set in a random graph, the problem of finding a near ground state in a spin glass model, the problem of finding a satisfying assignment in a random constraint satisfaction problem, and many many more. Unfortunately, at the same time no formal computational hardness results exist which explains this persistent algorithmic gap. In the talk we will describe a new approach for establishing an algorithmic intractability for these problems called… |
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Speaker: Max ReppenTitle: Neural Optimal Stopping BoundaryVenue: CMSA Room G10Speaker: Max Reppen (Boston University) Title: Neural Optimal Stopping Boundary Abstract: A method based on deep artificial neural networks and empirical risk minimization is developed to calculate the boundary separating the stopping and continuation regions in optimal stopping. The algorithm parameterizes the stopping boundary as the graph of a function and introduces relaxed stopping rules based on fuzzy boundaries to facilitate efficient optimization. Several financial instruments, some in high dimensions, are analyzed through this method, demonstrating its effectiveness. The existence of the stopping boundary is also proved under natural structural assumptions. |
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Speaker: Hidenori TanakaTitle: Noether’s Learning Dynamics: Role of Symmetry Breaking in Neural NetworksVenue: CMSA Room G10Colloquium Speaker: Hidenori Tanaka (NTT Research at Harvard) Title: Noether’s Learning Dynamics: Role of Symmetry Breaking in Neural Networks Abstract: In nature, symmetry governs regularities, while symmetry breaking brings texture. In artificial neural networks, symmetry has been a central design principle, but the role of symmetry breaking is not well understood. Here, we develop a Lagrangian formulation to study the geometry of learning dynamics in neural networks and reveal a key mechanism of explicit symmetry breaking behind the efficiency and stability of modern neural networks. Then, we generalize Noether’s theorem known in physics to describe a unique symmetry breaking mechanism in learning and derive the resulting motion of the Noether charge: Noether’s Learning Dynamics (NLD). Finally, we apply… |
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Speaker: Liang FuTitle: Doping and inverting Mott insulators on semiconductor moire superlatticesVenue: CMSA Room G10Speaker: Liang Fu (MIT) Title: Doping and inverting Mott insulators on semiconductor moire superlattices Abstract: Semiconductor bilayer heterostructures provide a remarkable platform for simulating Hubbard models on an emergent lattice defined by moire potential minima. As a hallmark of Hubbard model physics, the Mott insulator state with local magnetic moments has been observed at half filling of moire band. In this talk, I will describe new phases of matter that grow out of the canonical 120-degree antiferromagnetic Mott insulator on the triangular lattice. First, in an intermediate range of magnetic fields, doping this Mott insulator gives rise to a dilute gas of spin polarons, which form a pseudogap metal. Second, the application of an electric field between… |
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Speaker: Virginia Vassilevska WilliamsTitle: Clique listing algorithmsVenue: CMSA Room G10Speaker: Virginia Vassilevska Williams (MIT) Title: Clique listing algorithms Abstract: A k-clique in a graph G is a subgraph of G on k vertices in which every pair of vertices is linked by an edge. Cliques are a natural notion of social network cohesiveness with a long history. A fundamental question, with many applications, is “How fast can one list all k-cliques in a given graph?”. Even just detecting whether an n-vertex graph contains a k-Clique has long been known to be NP-complete when k can depend on n (and hence no efficient algorithm is likely to exist for it). If k is a small constant, such as 3 or 4 (independent of n), even the brute-force algorithm… |
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Speaker: Patrick LopattoTitle: The Mobility Edge of Lévy MatricesVenue: CMSA Room G10Colloquium Speaker: Patrick Lopatto (Brown) Title: The Mobility Edge of Lévy Matrices Abstract: Lévy matrices are symmetric random matrices whose entry distributions lie in the domain of attraction of an alpha-stable law; such distributions have infinite variance when alpha is less than 2. Due to the ubiquity of heavy-tailed randomness, these models have been broadly applied in physics, finance, and statistics. When the entries have infinite mean, Lévy matrices are predicted to exhibit a phase transition separating a region of delocalized eigenvectors from one with localized eigenvectors. We will discuss the physical context for this conjecture, and describe a result establishing it for values of alpha close to zero and one. This is joint work with Amol Aggarwal… |
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Speaker: James CummingsTitle: Complete disorder is impossible: Some topics in Ramsey theoryVenue: CMSA Room G10Colloquium Title: Complete disorder is impossible: Some topics in Ramsey theory Speaker: James Cummings, Carnegie Mellon University Abstract: The classical infinite Ramsey theorem states that if we colour pairs of natural numbers using two colours, there is an infinite set all of whose pairs get the same colour. This is the beginning of a rich theory, which touches on many areas of mathematics including graph theory, set theory and dynamics. I will give an overview of Ramsey theory, emphasizing the diverse ideas which are at play in this area. |
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Speaker: Subir SachdevTitle: Quantum statistical mechanics of charged black holes and strange metalsVenue: CMSA Room G10Colloquium Please note this colloquium will be held at a special time: 4:00-5:00 pm. Speaker: Subir Sachdev (Harvard) Title: Quantum statistical mechanics of charged black holes and strange metals Abstract: The Sachdev-Ye-Kitaev model was introduced as a toy model of interacting fermions without any particle-like excitations. I will describe how this toy model yields the universal low energy quantum theory of generic charged black holes in asymptotically 3+1 dimensional Minkowski space. I will also discuss how extensions of the SYK model yield a realistic theory of the strange metal phase of correlated electron systems. Slides: cmsa22 |
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Speaker: Dima SinapovaTitle: The Tree Property and uncountable cardinalsVenue: CMSA Room G10Colloquium Speaker: Dima Sinapova (Rutgers University) Title: The Tree Property and uncountable cardinals Abstract: In the late 19th century Cantor discovered that there are different levels of infinity. More precisely he showed that there is no bijection between the natural numbers and the real numbers, meaning that the reals are uncountable. He then went on to discover a whole hierarchy of infinite cardinal numbers. It is natural to ask if finitary and countably infinite combinatorial objects have uncountable analogues. It turns out that the answer is yes. We will focus on one such key combinatorial property, the tree property. A classical result from graph theory (König’s infinity lemma) shows the existence of this property for countable trees. We… |
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Speaker: Melody ChanTitle: Moduli spaces of graphsVenue: CMSA Room G10Colloquium Speaker: Melody Chan Title: Moduli spaces of graphs Abstract: A metric graph is a graph—a finite network of vertices and edges—together with a prescription of a positive real length on each edge. I’ll use the term “moduli space of graphs” to refer to certain combinatorial spaces—think simplicial complexes—that furnish parameter spaces for metric graphs. There are different flavors of spaces depending on some additional choices of decorations on the graphs, but roughly, each cell parametrizes all possible metrizations of a fixed combinatorial graph. Many flavors of these moduli spaces have been in circulation for a while, starting with the work of Culler-Vogtmann in the 1980s on Outer Space. They have also recently played an important role in… |