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DTSTART;TZID=America/New_York:20230922T100000
DTEND;TZID=America/New_York:20230922T113000
DTSTAMP:20240223T095601Z
CREATED:20240223T095601Z
LAST-MODIFIED:20240223T095601Z
UID:10002845-1695376800-1695382200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Floquet codes\, automorphisms\, and quantum computation
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Margarita Davydova (MIT) \nTitle: Floquet codes\, automorphisms\, and quantum computation \nAbstract: In this talk\, I will introduce a new kind of measurement-based quantum computation inspired by Floquet codes. In this model\, the quantum logical gates are implemented by short sequences of low-weight measurements which simultaneously encode logical information and enable error correction.  We introduce a new class of quantum error-correcting codes generalizing Floquet codes that achieve this\, which we call dynamic automorphism (DA) codes. \nAs in Floquet codes\, the instantaneous codespace of a DA code at any fixed point in time is that of a topological code. In this case\, the quantum computation can be viewed as a sequence of time-like domain walls implementing automorphisms of the topological order\, which can be understood in terms of reversible anyon condensation paths in a particular parent model.  This talk will introduce all of these concepts as well as provide a new perspective for thinking about Floquet codes. \nThe explicit examples that we construct\, which we call DA color codes\, can implement the full Clifford group of logical gates in 2+1d by two- and\, rarely three-body measurements. Using adaptive two-body measurements\, we can achieve a non-Clifford gate in 3+1d\, making the first step towards universal quantum computation in this model. \nThe talk is based on recent work with Nathanan Tantivasadakarn\, Shankar Balasubramanian\, and David Aasen [arxiv: 2307.10353].
URL:https://live-hu-cmsa-222.pantheonsite.io/event/qm_92223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-09.22.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230920T103000
DTEND;TZID=America/New_York:20230920T113000
DTSTAMP:20240223T104903Z
CREATED:20240223T104903Z
LAST-MODIFIED:20240223T104903Z
UID:10002851-1695205800-1695209400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Exact Results in Flat Band Hubbard Models
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Jonah Herzog-Arbeitman\, Princeton University \nTitle: Exact Results in Flat Band Hubbard Models \nAbstract: Flat bands\, like those in the kagome lattice or twisted bilayer graphene\, are a natural setting for studying strongly coupled physics since the interaction strength is the only energy scale in the problem. They can exhibit unconventional behavior in the multi-orbital case: the mean-field theory of flat band attractive Hubbard models shows the possibility of superconductivity even though the Fermi velocity of the bands is strictly zero. However\, it is not necessary to resort to this approximation. We demonstrate that the groundstates and low-energy excitations of a large class of attractive Hubbard models are exactly solvable\, offering a rare\, microscopic view of their physics. The solution reveals the importance of quantum geometry in escaping (some of) BCS phenomenology within a tractable and nontrivial strong coupling theory.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/tqms_92023/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Topological-Seminar-09.20.23.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230915T120000
DTEND;TZID=America/New_York:20230915T130000
DTSTAMP:20240223T112851Z
CREATED:20240223T112851Z
LAST-MODIFIED:20240223T112851Z
UID:10002864-1694779200-1694782800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Quantum UV-IR map and curve counts in skeins
DESCRIPTION:Member Seminar \nSpeaker: Sunghyuk Park \nTitle: Quantum UV-IR map and curve counts in skeins \nAbstract: Quantum UV-IR map (a.k.a. q-nonabelianization map)\, introduced by Neitzke and Yan\, is a map from UV line defects in a 4d N=2 theory of class S to those of the IR. Mathematically\, it can be described as a map between skein modules and is a close cousin of quantum trace map of Bonahon and Wong. \nIn this talk\, I will discuss how quantum UV-IR map can be generalized to a map between HOMFLYPT skein modules\, using skein-valued curve counts of Ekholm and Shende.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/member-seminar-91523/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230914T130000
DTEND;TZID=America/New_York:20230914T140000
DTSTAMP:20240223T111752Z
CREATED:20240223T111752Z
LAST-MODIFIED:20240223T111752Z
UID:10002860-1694696400-1694700000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Frustration-free states of cell fate networks: the case of the epithelial-mesenchymal transition
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Herbert Levine (Northeastern)\n\nTitle: Frustration-free states of cell fate networks: the case of the epithelial-mesenchymal transition\n\nAbstract: Cell fate decisions are made by allowing external signals to govern the steady-state pattern adopted by networks of interacting regulatory factors governing transcription and translation. One of these decisions\, of importance for both developmental processes and for cancer metastasis\, is the epithelial-mesenchymal transition (EMT). In this talk\, we will argue that these biological networks have highly non-generic interaction structures such that they allow for phenotypic states with very low frustration\, i.e. where most interactions are satisfied. This property has important consequences for the allowed dynamics of these systems.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/am-91423/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230913T163000
DTEND;TZID=America/New_York:20230913T180000
DTSTAMP:20240223T111403Z
CREATED:20240223T111403Z
LAST-MODIFIED:20240223T111403Z
UID:10002859-1694622600-1694628000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Anomalies of Non-Invertible Symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Clay Córdova (U Chicago) \nTitle: Anomalies of Non-Invertible Symmetries
URL:https://live-hu-cmsa-222.pantheonsite.io/event/qm_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-09.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230913T103000
DTEND;TZID=America/New_York:20230913T113000
DTSTAMP:20240223T113738Z
CREATED:20230904T061048Z
LAST-MODIFIED:20240223T113738Z
UID:10001122-1694601000-1694604600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Phase transitions out of quantum Hall states in moire TMD bilayers
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Xueyang Song (MIT) \nTitle: Phase transitions out of quantum Hall states in moire TMD bilayers \nAbstract: Motivated by the recent experimental breakthroughs in observing Fractional Quantum Anomalous Hall (FQAH) states in moir\’e Transition Metal Dichalcogenide (TMD) bilayers\, we propose and study various unconventional phase transitions between quantum Hall phases and Fermi liquids or charge ordered phases upon tuning the bandwidth.  At filling -2/3\, we describe a direct transition between the FQAH state and a Charge Density Wave (CDW) insulator. The critical theory resembles that of the familiar deconfined quantum critical point (DQCP) but with an additional Chern-Simons term. At filling -1/2\, we study the possibility of a continuous transition between the composite Fermi liquid (CFL) and the Fermi liquid (FL) building on and refining previous work by  Barkeshli and McGreevy.   Crucially we show that translation symmetry alone is enough to enable a second order CFL-FL transition. We argue that there must be critical CDW fluctuations though neither phase has long range CDW order.  A striking signature is a universal jump of resistivities at the critical point. With disorder\, we argue that the CDW order gets pinned and the CFL-FL evolution happens through an intermediate electrically insulating phase with mobile neutral fermions. A clean analog of this insulating phase with long range CDW order and a neutral fermi surface can potentially also exist.  We also present a critical theory for the CFL to FL transition at filling -3/4.  Our work opens up a new avenue to realize deconfined criticality and fractionalized phases beyond familiar Landau level physics in the moire Chern band system.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/tqms_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Topological-Seminar-09.12.23.docx-2.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230912T160000
DTEND;TZID=America/New_York:20230912T170000
DTSTAMP:20240223T104300Z
CREATED:20240223T104300Z
LAST-MODIFIED:20240223T104300Z
UID:10002849-1694534400-1694538000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Homotopy classes of loops of Clifford unitaries
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Roman Geiko\, UCLA \nTitle: Homotopy classes of loops of Clifford unitaries \nAbstract: We study Clifford locality-preserving unitaries and stabilizer Hamiltonians by means of Hermitian K-theory. We demonstrate how the notion of algebraic homotopy of modules over Laurent polynomial rings translates into the connectedness of two short-range entangled stabilizer Hamiltonians by a shallow Clifford circuit. We apply this observation to a classification of homotopy classes of loops of Clifford unitaries. The talk is based on a work in collaboration with Yichen Hu.  https://arxiv.org/abs/2306.09903.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/tqms_91223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Topological-Seminar-09.12.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230908T100000
DTEND;TZID=America/New_York:20230908T113000
DTSTAMP:20240116T070515Z
CREATED:20230904T055802Z
LAST-MODIFIED:20240116T070515Z
UID:10001125-1694167200-1694172600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Xiao-Gang Wen (MIT) \nTitle: A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry \nAbstract: Emergent symmetry can be generalized symmetry beyond (higher) group description and/or can be anomalous. I will describe a unified theory for generalized symmetry based on symmetry/topological-order correspondence. I will also discuss some applications of emergent generalized symmetry.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/qm_9823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-09.08.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230516T090000
DTEND;TZID=America/New_York:20230519T170000
DTSTAMP:20231226T172026Z
CREATED:20230705T055549Z
LAST-MODIFIED:20231226T172026Z
UID:10000068-1684227600-1684515600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:GRAMSIA: Graphical Models\, Statistical Inference\, and Algorithms
DESCRIPTION:On May 16 – May 19\, 2023 the CMSA hosted a four-day workshop on GRAMSIA: Graphical Models\, Statistical Inference\, and Algorithms. The workshop was held in room G10 of the CMSA\, located at 20 Garden Street\, Cambridge\, MA. This workshop was organized by David Gamarnik (MIT)\, Kavita Ramanan (Brown)\, and Prasad Tetali  (Carnegie Mellon). \nThe purpose of this workshop is to highlight various mathematical questions and issues associated with graphical models and message-passing algorithms\, and to bring together a group of researchers for discussion of the latest progress and challenges ahead. In addition to the substantial impact of graphical models on applied areas\, they are also connected to various branches of the mathematical sciences. Rather than focusing on the applications\, the primary goal is to highlight and deepen these mathematical connections. \nLocation: Room G10\, CMSA\, 20 Garden Street\, Cambridge MA 02138 \n  \nSpeakers:\n\nJake Abernethy (Georgia Tech)\nGuy Bresler (MIT)\nFlorent Krzakala (Ecole Polytechnique Federale de Lausanne)\nLester Mackey (Microsoft Research New England)\nTheo McKenzie (Harvard)\nAndrea Montanari (Stanford)\nElchanan Mossel (MIT)\nYury Polyanskiy (MIT)\nPatrick Rebeschini (Oxford)\nSubhabrata Sen (Harvard)\nDevavrat Shah (MIT)\nPragya Sur (Harvard)\nAlex Wein (UC Davis)\nYihong Wu (Yale)\nSarath Yasodharan (Brown)\nHorng-Tzer Yau (Harvard)\nChristina Lee Yu (Cornell)\nIlias Zadik (MIT)\n\nSchedule:\nTuesday\, May 16\, 2023 \n\n\n\n9:00 am\nBreakfast\n\n\n9:15 – 9:30 am\nIntroductory remarks by organizers\n\n\n9:30 – 10:20 am\nSubhabrata Sen (Harvard) \nTitle: Mean-field approximations for high-dimensional Bayesian regression \nAbstract: Variational approximations provide an attractive computational alternative to MCMC-based strategies for approximating the posterior distribution in Bayesian inference. The Naive Mean-Field (NMF) approximation is the simplest version of this strategy—this approach approximates the posterior in KL divergence by a product distribution. There has been considerable progress recently in understanding the accuracy of NMF under structural constraints such as sparsity\, but not much is known in the absence of such constraints. Moreover\, in some high-dimensional settings\, the NMF is expected to be grossly inaccurate\, and advanced mean-field techniques (e.g. Bethe approximation) are expected to provide accurate approximations. We will present some recent work in understanding this duality in the context of high-dimensional regression. This is based on joint work with Sumit Mukherjee (Columbia) and Jiaze Qiu (Harvard University).\n\n\n10:30 – 11:00 am\nCoffee break  \n\n\n11:00 – 11:50 am\nElchanan Mossel (MIT) \nTitle: Some modern perspectives on the Kesten-Stigum bound for reconstruction on trees. \nAbstract: The Kesten-Stigum bound is a fundamental spectral bound for reconstruction on trees. I will discuss some conjectures and recent progress on understanding when it is tight as well as some conjectures and recent progress on what it signifies even in cases where it is not tight.\n\n\n12:00 – 2:00 pm\nLunch\n\n\n2:00 – 2:50 pm\nChristina Lee Yu (Cornell) \nTitle: Exploiting Neighborhood Interference with Low Order Interactions under Unit Randomized Design \nAbstract: Network interference\, where the outcome of an individual is affected by the treatment assignment of those in their social network\, is pervasive in many real-world settings. However\, it poses a challenge to estimating causal effects. We consider the task of estimating the total treatment effect (TTE)\, or the difference between the average outcomes of the population when everyone is treated versus when no one is\, under network interference. Under a Bernoulli randomized design\, we utilize knowledge of the network structure to provide an unbiased estimator for the TTE when network interference effects are constrained to low order interactions among neighbors of an individual. We make no assumptions on the graph other than bounded degree\, allowing for well-connected networks that may not be easily clustered. Central to our contribution is a new framework for balancing between model flexibility and statistical complexity as captured by this low order interactions structure.\n\n\n3:00 – 3:30 pm\nCoffee break \n\n\n3:30 – 4:20 pm\nTheo McKenzie (Harvard) \nTitle: Spectral statistics for sparse random graphs \nAbstract: Understanding the eigenvectors and eigenvalues of the adjacency matrix of random graphs is fundamental to many algorithmic questions; moreover\, it is related to longstanding questions in quantum physics. In this talk we focus on random models of sparse graphs\, giving some properties that are unique to these sparse graphs\, as well as some specific obstacles. Based on this\, we show some new results on spectral statistics of sparse random graphs\, as well as some conjectures.\n\n\n4:40 – 6:30 pm\nLightning talk session + welcome reception\n\n\n\n  \nWednesday\, May 17\, 2023 \n\n\n\n9:00 am\nBreakfast\n\n\n9:30 – 10:20\nIlias Zadik (MIT) \nTitle: Revisiting Jerrum’s Metropolis Process for the Planted Clique Problem \nAbstract: Jerrum in 1992 (co-)introduced the planted clique model by proving the (worst-case initialization) failure of the Metropolis process to recover any o(sqrt(n))-sized clique planted in the Erdos-Renyi graph G(n\,1/2). This result is classically cited in the literature of the problem\, as the “first evidence” the o(sqrt(n))-sized planted clique recovery task is “algorithmically hard”.\nIn this work\, we show that the Metropolis process actually fails to work (under worst-case initialization) for any o(n)-sized planted clique\, that is the failure applies well beyond the sqrt(n) “conjectured algorithmic threshold”. Moreover we also prove\, for a large number of temperature values\, that the Metropolis process fails also under “natural initialization”\, resolving an open question posed by Jerrum in 1992.\n\n\n10:30 – 11:00\nCoffee break\n\n\n11:00 – 11:50\nFlorent Krzakala (Ecole Polytechnique Federale de Lausanne) \nTitle: Are Gaussian data all you need for machine learning theory? \nAbstract: Clearly\, no! Nevertheless\, the Gaussian assumption remains prevalent among theoreticians\, particularly in high-dimensional statistics and physics\, less so in traditional statistical learning circles. To what extent are Gaussian features merely a convenient choice for certain theoreticians\, or genuinely an effective model for learning? In this talk\, I will review recent progress on these questions\, achieved using rigorous probabilistic approaches in high-dimension and techniques from mathematical statistical physics. I will demonstrate that\, despite its apparent limitations\, the Gaussian approach is sometimes much closer to reality than one might expect. In particular\, I will discuss key findings from a series of recent papers that showcase the Gaussian equivalence of generative models\, the universality of Gaussian mixtures\, and the conditions under which a single Gaussian can characterize the error in high-dimensional estimation. These results illuminate the strengths and weaknesses of the Gaussian assumption\, shedding light on its applicability and limitations in the realm of theoretical statistical learning.\n\n\n12:00 – 2:00 pm\nLunch\n\n\n2:00 – 2:50 pm\nAndrea Montanari (Stanford) \nTitle: Dimension free ridge regression \nAbstract: Random matrix theory has become a widely useful tool in high-dimensional statistics and theoretical machine learning. However\, random matrix theory is largely focused on the proportional asymptotics in which the number of columns grows proportionally to the number of rows of the data matrix. This is not always the most natural setting in statistics where columns correspond to covariates and rows to samples. With the objective to move beyond the proportional asymptotics\, we revisit ridge regression. We allow the feature vector to be high-dimensional\, or even infinite-dimensional\, in which case it belongs to a separable Hilbert space and assume it to satisfy a certain convex concentration property. Within this setting\, we establish non-asymptotic bounds that approximate the bias and variance of ridge regression in terms of the bias and variance of an ‘equivalent’ sequence model (a regression model with diagonal design matrix). Previously\, such an approximation result was known only in the proportional regime and only up to additive errors: in particular\, it did not allow to characterize the behavior of the excess risk when this converges to 0. Our general theory recovers earlier results in the proportional regime (with better error rates). As a new application\, we obtain a completely explicit and sharp characterization of ridge regression for Hilbert covariates with regularly varying spectrum. Finally\, we analyze the overparametrized near-interpolation setting and obtain sharp ‘benign overfitting’ guarantees. \n[Based on joint work with Chen Cheng]\n\n\n3:00 – 3:50 pm\nYury Polyanskiy (MIT) \nTitle: Recent results on broadcasting on trees and stochastic block model \nAbstract: I will survey recent results and open questions regarding the q-ary stochastic block model and its local version (broadcasting on trees\, or BOT). For example\, establishing uniqueness of non-trivial solution to distribution recursions (BP fixed point) implies a characterization for the limiting mutual information between the graph and community labels. For q=2 uniqueness holds in all regimes. For q>2 uniqueness is currently only proved above a certain threshold that is asymptotically (for large q) is close to Kesten-Stigum (KS) threshold. At the same time between the BOT reconstruction and KS we show that uniqueness does not hold\, at least in the presence of (arbitrary small) vertex-level side information. I will also discuss extension of the robust reconstruction result of Janson-Mossel’2004. \nBased on joint works with Qian Yu (Princeton) and Yuzhou Gu (MIT).\n\n\n4:00 – 4:30 pm\nCoffee break \n\n\n4:30 – 5:20 pm\nAlex Wein (UC Davis) \nTitle: Is Planted Coloring Easier than Planted Clique? \nAbstract: The task of finding a planted clique in the random graph G(n\,1/2) is perhaps the canonical example of a statistical-computational gap: for some clique sizes\, the task is statistically possible but believed to be computationally hard. Really\, there are multiple well-studied tasks related to the planted clique model: detection\, recovery\, and refutation. While these are equally difficult in the case of planted clique\, this need not be true in general. In the related planted coloring model\, I will discuss the computational complexity of these three tasks and the interplay among them. Our computational hardness results are based on the low-degree polynomial model of computation.By taking the complement of the graph\, the planted coloring model is analogous to the planted clique model but with many planted cliques. Here our conclusion is that adding more cliques makes the detection problem easier but not the recovery problem.\n\n\n\n  \nThursday\, May 18\, 2023 \n\n\n\n9:00\nBreakfast\n\n\n9:30 – 10:20\nGuy Bresler (MIT) \nTitle: Algorithmic Decorrelation and Planted Clique in Dependent Random Graphs \nAbstract: There is a growing collection of average-case reductions starting from Planted Clique (or Planted Dense Subgraph) and mapping to a variety of statistics problems\, sharply characterizing their computational phase transitions. These reductions transform an instance of Planted Clique\, a highly structured problem with its simple clique signal and independent noise\, to problems with richer structure. In this talk we aim to make progress in the other direction: to what extent can these problems\, which often have complicated dependent noise\, be transformed back to Planted Clique? Such a bidirectional reduction between Planted Clique and another problem shows a strong computational equivalence between the two problems.  We develop a new general framework for reasoning about the validity of average-case reductions based on low sensitivity to perturbations. As a concrete instance of our general result\, we consider the planted clique (or dense subgraph) problem in an ambient graph that has dependent edges induced by randomly adding triangles to the Erdos-Renyi graph G(n\,p)\, and show how to successfully eliminate dependence by carefully removing the triangles while approximately preserving the clique (or dense subgraph). Joint work with Chenghao Guo and Yury Polyanskiy.\n\n\n10:30 – 11:00\nCoffee break  \n\n\n11:00 – 11:50\nSarath Yasodharan (Brown) \nTitle: A Sanov-type theorem for unimodular marked random graphs and its applications \nAbstract: We prove a Sanov-type large deviation principle for the component empirical measures of certain sequences of unimodular random graphs (including Erdos-Renyi and random regular graphs) whose vertices are marked with i.i.d. random variables. Specifically\, we show that the rate function can be expressed in a fairly tractable form involving suitable relative entropy functionals. As a corollary\, we establish a variational formula for the annealed pressure (or limiting log partition function) for various statistical physics models on sparse random graphs. This is joint work with I-Hsun Chen and Kavita Ramanan.\n\n\n12:00 – 12:15 pm \n12:15 – 2:00 pm\nGroup Photo  \nLunch \n\n\n2:00 – 2:50 pm\nPatrick Rebeschini (Oxford) \nTitle: Implicit regularization via uniform convergence \nAbstract: Uniform convergence is one of the main tools to analyze the complexity of learning algorithms based on explicit regularization\, but it has shown limited applicability in the context of implicit regularization. In this talk\, we investigate the statistical guarantees on the excess risk achieved by early-stopped mirror descent run on the unregularized empirical risk with the squared loss for linear models and kernel methods. We establish a direct link between the potential-based analysis of mirror descent from optimization theory and uniform learning. This link allows characterizing the statistical performance of the path traced by mirror descent directly in terms of localized Rademacher complexities of function classes depending on the choice of the mirror map\, initialization point\, step size\, and the number of iterations. We will discuss other results along the way.\n\n\n3:00 – 3:50 pm\nPragya Sur (Harvard) \nTitle: A New Central Limit Theorem for the Augmented IPW estimator in high dimensions \nAbstract: Estimating the average treatment effect (ATE) is a central problem in causal inference. Modern advances in the field studied estimation and inference for the ATE in high dimensions through a variety of approaches. Doubly robust estimators such as the augmented inverse probability weighting (AIPW) form a popular approach in this context. However\, the high-dimensional literature surrounding these estimators relies on sparsity conditions\, either on the outcome regression (OR) or the propensity score (PS) model. This talk will introduce a new central limit theorem for the classical AIPW estimator\, that applies agnostic to such sparsity-type assumptions. Specifically\, we will study properties of the cross-fit version of the estimator under well-specified OR and PS models\, and the proportional asymptotics regime where the number of confounders and sample size diverge proportional to each other. Under assumptions on the covariate distribution\, our CLT will uncover two crucial phenomena among others: (i) the cross-fit AIPW exhibits a substantial variance inflation that can be quantified in terms of the signal-to-noise ratio and other problem parameters\, (ii) the asymptotic covariance between the estimators used while cross-fitting is non-negligible even on the root-n scale. These findings are strikingly different from their classical counterparts\, and open a vista of possibilities for studying similar other high-dimensional effects. On the technical front\, our work utilizes a novel interplay between three distinct tools—approximate message passing theory\, the theory of deterministic equivalents\, and the leave-one-out approach.\n\n\n4:00 – 4:30 pm\nCoffee break \n\n\n4:30 – 5:20 pm\nYihong Wu (Yale) \nTitle: Random graph matching at Otter’s threshold via counting chandeliers\n\nAbstract: We propose an efficient algorithm for graph matching based on similarity scores constructed from counting a certain family of weighted trees rooted at each vertex. For two Erdős–Rényi graphs G(n\,q) whose edges are correlated through a latent vertex correspondence\, we show that this algorithm correctly matches all but a vanishing fraction of the vertices with high probability\, provided that nq\to\infty and the edge correlation coefficient ρ satisfies ρ^2>α≈0.338\, where α is Otter’s tree-counting constant. Moreover\, this almost exact matching can be made exact under an extra condition that is information-theoretically necessary. This is the first polynomial-time graph matching algorithm that succeeds at an explicit constant correlation and applies to both sparse and dense graphs. In comparison\, previous methods either require ρ=1−o(1) or are restricted to sparse graphs. The crux of the algorithm is a carefully curated family of rooted trees called chandeliers\, which allows effective extraction of the graph correlation from the counts of the same tree while suppressing the undesirable correlation between those of different trees. This is joint work with Cheng Mao\, Jiaming Xu\, and Sophie Yu\, available at https://arxiv.org/abs/2209.12313\n\n\n\n  \nFriday\, May 19\, 2023 \n\n\n\n9:00\nBreakfast\n\n\n9:30 – 10:20\nJake Abernethy (Georgia Tech) \nTitle: Optimization\, Learning\, and Margin-maximization via Playing Games \nAbstract: A very popular trick for solving certain types of optimization problems is this: write your objective as the solution of a two-player zero-sum game\, endow both players with an appropriate learning algorithm\, watch how the opponents compete\, and extract an (approximate) solution from the actions/decisions taken by the players throughout the process. This approach is very generic and provides a natural template to produce new and interesting algorithms. I will describe this framework and show how it applies in several scenarios\, including optimization\, learning\, and margin-maximiation problems. Along the way we will encounter a number of novel tools and rediscover some classical ones as well.\n\n\n10:30 – 11:00\nCoffee break  \n\n\n11:00 – 11:50\nDevavrat Shah (MIT) \nTitle: On counterfactual inference with unobserved confounding via exponential family \nAbstract: We are interested in the problem of unit-level counterfactual inference with unobserved confounders owing to the increasing importance of personalized decision-making in many domains: consider a recommender system interacting with a user over time where each user is provided recommendations based on observed demographics\, prior engagement levels as well as certain unobserved factors. The system adapts its recommendations sequentially and differently for each user. Ideally\, at each point in time\, the system wants to infer each user’s unknown engagement if it were exposed to a different sequence of recommendations while everything else remained unchanged. This task is challenging since: (a) the unobserved factors could give rise to spurious associations\, (b) the users could be heterogeneous\, and (c) only a single trajectory per user is available. \nWe model the underlying joint distribution through an exponential family. This reduces the task of unit-level counterfactual inference to simultaneously learning a collection of distributions of a given exponential family with different unknown parameters with single observation per distribution. We discuss a computationally efficient method for learning all of these parameters with estimation error scaling linearly with the metric entropy of the space of unknown parameters – if the parameters are an s-sparse linear combination of k known vectors in p dimension\, the error scales as O(s log k/p).  En route\, we derive sufficient conditions for compactly supported distributions to satisfy the logarithmic Sobolev inequality. \nBased on a joint work with Raaz Dwivedi\, Abhin Shah and Greg Wornell (all at MIT) with manuscript available here: https://arxiv.org/abs/2211.08209\n\n\n12:00 – 2:00 pm\nLunch  \n\n\n2:00 – 2:50 pm\nLester Mackey  (Microsoft Research New England) \nTitle: Advances in Distribution Compression \nAbstract: This talk will introduce two new tools for summarizing a probability distribution more effectively than independent sampling or standard Markov chain Monte Carlo thinning:\n1. Given an initial n-point summary (for example\, from independent sampling or a Markov chain)\, kernel thinning finds a subset of only square-root n-points with comparable worst-case integration error across a reproducing kernel Hilbert space.\n2. If the initial summary suffers from biases due to off-target sampling\, tempering\, or burn-in\, Stein thinning simultaneously compresses the summary and improves the accuracy by correcting for these biases.\nThese tools are especially well-suited for tasks that incur substantial downstream computation costs per summary point like organ and tissue modeling in which each simulation consumes 1000s of CPU hours.\nBased on joint work with Raaz Dwivedi\, Marina Riabiz\, Wilson Ye Chen\, Jon Cockayne\, Pawel Swietach\, Steven A. Niederer\, Chris. J. Oates\, Abhishek Shetty\, and Carles Domingo-Enrich.\n\n\n3:00 – 3:30 pm\nCoffee break \n\n\n3:30 – 4:20 pm\nHorng-Tzer Yau (Harvard) \nTitle: On the spectral gap of mean-field spin glass models. \nAbstract: We will discuss recent progress regarding spectral gaps for the Glauber dynamics of spin glasses at high temperature. In addition\, we will also report on estimating the operator norm  of the covariance matrix for the SK model.\n\n\n\n  \nModerators: Benjamin McKenna\, Harvard CMSA & Changji Xu\, Harvard CMSA \n\n  \n \nCMSA COVID-19 Policies
URL:https://live-hu-cmsa-222.pantheonsite.io/event/gramsia2023/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Event,Workshop
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/GRAMSIAcover-600x338-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230515T120000
DTEND;TZID=America/New_York:20230515T130000
DTSTAMP:20240216T105142Z
CREATED:20230817T172120Z
LAST-MODIFIED:20240216T105142Z
UID:10001245-1684152000-1684155600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Quantum information and extended topological quantum field theory 
DESCRIPTION:Member Seminar \nSpeaker: Gabriel Wong \nTitle: Quantum information and extended topological quantum field theory \nAbstract: Recently\, ideas from quantum information theory have played an important role in condensed matter and quantum gravity research. Most of these applications focus on the entanglement structure of quantum states\, and the computation of entanglement measures such as entanglement entropy has been an essential part of the story. In this talk\, we will address some subtleties that arise when trying to define entanglement entropy in quantum field theory and quantum gravity. In particular\, we will explain why extended topological field theory provides a useful framework to define and compute entanglement entropy in a continuous system. Time permitting\, we will explain some recent applications of these ideas in low dimensional quantum gravity and to topological string theory. \n  \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/member-seminar-51523/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230507T090000
DTEND;TZID=America/New_York:20230512T180000
DTSTAMP:20240215T100004Z
CREATED:20230705T055311Z
LAST-MODIFIED:20240215T100004Z
UID:10000069-1683450000-1683914400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Workshop on Global Categorical Symmetries
DESCRIPTION:The CMSA will be hosting a Workshop on Global Categorical Symmetries from May 7 – 12\, 2023 \nParticipation in the workshop is by invitation. \nPublic Lectures \nThere will be three lectures on Thursday\, May 11\, 2023\, which are open to the public.\nLocation:  Room G-10\, CMSA\, 20 Garden Street\, Cambridge MA 02138\nNote: The public lectures will be held in-person only. \n2:00 – 2:50 pm\nSpeaker: Kantaro Ohmori (U Tokyo )\nTitle: Fusion Surface Models: 2+1d Lattice Models from Higher Categories\nAbstract: Generalized symmetry in general dimensions is expected to be described by higher categories. Conversely\, one might expect that\, given a higher category with appropriate structures\, there exist models that admit the category as its symmetry. In this talk I will explain a construction of such 2+1d lattice models for fusion 2-categories defined by Douglas and Reutter\, generalizing the work of Aasen\, Fendley and Mong on anyon chains. The construction is by decorating a boundary of a topological Freed-Teleman-Moore sandwich into a non-topological boundary. In particular we can construct a family of candidate lattice systems for chiral topological orders. \n  \n3:00 – 3:50 pm\nSpeaker: David Jordan (Edinburgh)\nTitle: Langlands duality for 3-manifolds\nAbstract: Originating in number theory\, and permeating representation theory\, algebraic geometry\, and quantum field theory\, Langlands duality is a pattern of predictions relating pairs of mathematical objects which have no clear a priori mathematical relation. In this talk I’ll explain a new conjectural appearance of Langlands duality in the setting of 3-manifold topology\, I’ll give some evidence in the form of special cases\, and I’ll survey how the conjecture relates to both the arithmetic and geometric Langlands duality conjectures. \n3:50 – 4:30 pm\nTea/Snack Break \n4:30 – 5:30 pm\nSpeaker: Ken Intriligator (UCSD)\nColloquium\nTitle: QFT Aspects of Symmetry\nAbstract: Everything in the Universe\, including the photons that we see and the quarks and electrons in our bodies\, are actually ripples of quantum fields. Quantum field theory (QFT) is the underlying mathematical framework of Nature\, and in the case of electrons and photons it is the most precisely tested theory in science. Strongly coupled aspects\, e.g. the confinement of quarks and gluons at long distances\, remain challenging. QFT also describes condensed matter systems\, connects to string theory and quantum gravity\, and describes cosmology. Symmetry has deep and powerful realizations and implications throughout physics\, and this is especially so for the study of QFT. Symmetries play a helpful role in characterizing the phases of theories and their behavior under renormalization group flows (zooming out). Quantum field theory has also been an idea generating machine for mathematics\, and there has been increasingly fruitful synergy in both directions. We are currently exploring the symmetry-based interconnections between QFT and mathematics in our Simons Collaboration on Global Categorical Symmetry\, which is meeting here this week. I will try to provide an accessible\, colloquium-level introduction to aspects of symmetries and QFT\, both old and new.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/globalcomputing23/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Workshop
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230504T093000
DTEND;TZID=America/New_York:20230504T103000
DTSTAMP:20240228T073615Z
CREATED:20230818T044217Z
LAST-MODIFIED:20240228T073615Z
UID:10001263-1683192600-1683196200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Testing GR with GWs
DESCRIPTION:General Relativity Seminar \nSpeaker: Vitor Cardoso\, IST\, Lisbon and The Niels Bohr Institute\, Copenhagen \nTitle: Testing GR with GWs \nAbstract: One of the most remarkable possibilities of General Relativity concerns gravitational collapse to black holes\, leaving behind a geometry with light rings\, ergoregions and horizons. These peculiarities are responsible for uniqueness properties and energy extraction mechanisms that turn black holes into ideal laboratories of strong gravity\, of particle physics (yes!) and of possible quantum-gravity effects. I will discuss some of the latest progress in tests of General Relativity with black holes.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/gr_5423/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-GR-Seminar-05.04.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230503T153000
DTEND;TZID=America/New_York:20230503T163000
DTSTAMP:20240111T083748Z
CREATED:20230808T175916Z
LAST-MODIFIED:20240111T083748Z
UID:10001198-1683127800-1683131400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Random Neural Networks
DESCRIPTION:Probability Seminar \nSpeaker: Boris Hanin (Princeton)\n\nTitle: Random Neural Networks \nAbstract: Fully connected neural networks are described two by structural parameters: a depth L and a width N. In this talk\, I will present results and open questions about the asymptotic analysis of such networks with random weights and biases in the regime where N (and potentially L) are large. The first set of results are for deep linear networks\, which are simply products of L random matrices of size N x N. I’ll explain how the setting where the ratio L / N is fixed with both N and L large reveals a number of phenomena not present when only one of them is large. I will then state several results about non-linear networks in which this depth-to-width ratio L / N again plays a crucial role and gives an effective notion of depth for a random neural network.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/probability-5323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Probability-Seminar-05.03.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230503T123000
DTEND;TZID=America/New_York:20230503T133000
DTSTAMP:20240216T085646Z
CREATED:20230817T183740Z
LAST-MODIFIED:20240216T085646Z
UID:10001284-1683117000-1683120600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Generative Adversarial Networks (GANs): An Analytical Perspective
DESCRIPTION:Speaker: Xin Guo\, UC Berkeley \nTitle: Generative Adversarial Networks (GANs): An Analytical Perspective \nAbstract: Generative models have attracted intense interests recently. In this talk\, I will discuss one class of generative models\, Generative Adversarial Networks (GANs).  I will first provide a gentle review of the mathematical framework behind GANs. I will then proceed to discuss a few challenges in GANs training from an analytical perspective. I will finally report some recent progress for GANs training in terms of its stability and convergence analysis. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/collquium-5323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Colloquium-05.03.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230502T120000
DTEND;TZID=America/New_York:20230502T130000
DTSTAMP:20240118T085308Z
CREATED:20230817T171918Z
LAST-MODIFIED:20240118T085308Z
UID:10001244-1683028800-1683032400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Toroidal Positive Mass Theorem
DESCRIPTION:Member Seminar \nSpeaker: Aghil Alaee \nTitle: Toroidal Positive Mass Theorem \nAbstract: In this talk\, we review the positive mass conjecture in general relativity and prove a toroidal version of this conjecture in an asymptotically hyperbolic setting.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/member-seminar-5223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230427T130000
DTEND;TZID=America/New_York:20230427T140000
DTSTAMP:20240209T052245Z
CREATED:20230824T183024Z
LAST-MODIFIED:20240209T052245Z
UID:10001810-1682600400-1682604000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Competition at the front of expanding populations
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Mehran Kardar\, MIT \nTitle: Competition at the front of expanding populations \nAbstract: When competing species grow into new territory\, the population is dominated by descendants of successful ancestors at the expansion front. Successful ancestry depends on the reproductive advantage (fitness)\, as well as ability and opportunity to colonize new domains. (1) Based on symmetry considerations\, we present a model that  integrates both elements by coupling the classic description of one-dimensional competition (Fisher equation) to the minimal model of front shape (KPZ equation). Macroscopic manifestations of these equations on growth morphology are explored\, providing a framework to study spatial competition\, fixation\, and differentiation\, In particular\, we find that ability to expand in space may overcome reproductive advantage in colonizing new territory. (2) Variations of fitness\, as well as fixation time upon differentiation\, are shown to belong to distinct universality classes depending on limits to gain of fitness.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/am-42723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=:
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230426T153000
DTEND;TZID=America/New_York:20230426T163000
DTSTAMP:20240111T083026Z
CREATED:20230808T175545Z
LAST-MODIFIED:20240111T083026Z
UID:10001197-1682523000-1682526600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Boundary current fluctuations for the half space ASEP
DESCRIPTION:Probability Seminar \nSpeaker: Jimmy He (MIT) \nTitle: Boundary current fluctuations for the half space ASEP \nAbstract: The half space asymmetric simple exclusion process (ASEP) is an interacting particle system on the half line\, with particles allowed to enter/exit at the boundary. I will discuss recent work on understanding fluctuations for the number of particles in the half space ASEP started with no particles\, which exhibits the Baik-Rains phase transition between GSE\, GOE\, and Gaussian fluctuations as the boundary rates vary. As part of the proof\, we find new distributional identities relating this system to two other models\, the half space Hall-Littlewood process\, and the free boundary Schur process\, which allows exact formulas to be computed.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/probability-42623/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Probability-Seminar-04.26.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230426T123000
DTEND;TZID=America/New_York:20230426T133000
DTSTAMP:20240122T053311Z
CREATED:20230817T183259Z
LAST-MODIFIED:20240122T053311Z
UID:10001283-1682512200-1682515800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Boundary behavior at classical and quantum phase transitions
DESCRIPTION:Speaker: Max Metlitski (MIT) \nTitle: Boundary behavior at classical and quantum phase transitions \nAbstract: There has been a lot of recent interest in the boundary behavior of materials. This interest is driven in part by the field of topological states of quantum matter\, where exotic protected boundary states are ubiquitous. In this talk\, I’ll ask: what happens at a boundary of a system\, when the bulk goes through a phase transition. While this question was studied in the context of classical statistical mechanics in the 70s and 80s\, basic aspects of the boundary phase diagram for the simplest classical phase transitions have been missed until recently. I’ll describe progress in this field\, as well as some extensions to quantum phase transitions. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/collquium-42623/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Colloquium-04.26.2023.rev2_.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230425T120000
DTEND;TZID=America/New_York:20230425T130000
DTSTAMP:20240118T071815Z
CREATED:20230817T171725Z
LAST-MODIFIED:20240118T071815Z
UID:10001243-1682424000-1682427600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:On complete Calabi-Yau metrics and some related Monge-Ampere equations
DESCRIPTION:Member Seminar \nSpeaker: Freid Tong \nTitle: On complete Calabi-Yau metrics and some related Monge-Ampere equations \nAbstract: We will give a basic introduction to constructions for complete Calabi-Yau metrics. A systematic approach to construct such metrics using PDE methods was proposed in the work of Tian-Yau in the 90s and have attracted a lot of attention in recent years. I will discuss some joint work with B. Guo and T. Collins on a singular version of such a construction\, as well as some ongoing work with Prof. Yau on some related boundary value problems. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/member-seminar-42523/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230424T133000
DTEND;TZID=America/New_York:20230424T143000
DTSTAMP:20240119T052608Z
CREATED:20230818T043218Z
LAST-MODIFIED:20240119T052608Z
UID:10001261-1682343000-1682346600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Recent advances in scalar curvature and positive mass theorems
DESCRIPTION:General Relativity Seminar \nSpeaker: Tin Yau Tsang\, University of California Irvine \nTitle: Recent advances in scalar curvature and positive mass theorems\n\nAbstract:  First\, we have a review of classical tools for studying scalar curvature and positive mass theorem. Then we are going to discuss some advances and new perspectives on these tools which lead to a deeper understanding of geometry and initial data sets.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/gr_42423/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-GR-Seminar-04.24.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230420T133000
DTEND;TZID=America/New_York:20230420T143000
DTSTAMP:20240216T085423Z
CREATED:20230817T182708Z
LAST-MODIFIED:20240216T085423Z
UID:10001282-1681997400-1682001000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Black hole collider physics
DESCRIPTION:Speaker: Julio Parra Martinez\, Caltech \nTitle: Black hole collider physics \nAbstract: Despite more than a century since the development of Einstein’s theory\, the general relativistic two-body problem remains unsolved. A precise description of its solution is now essential\, as it is necessary for understanding the strong-gravity dynamics of compact binaries observed at LIGO/VIRGO/KAGRA and in future gravitational wave observatories. In this talk\, I will describe how considering the scattering of black holes and gravitons can shed new light on this problem. I will explain how using modern ideas from collider and particle physics we can calculate scattering observables in classical gravity\, and extract the basic ingredients that describe the bound binary dynamics. Such calculations have produced state-of-art predictions for current and future gravitational wave observatories\, which open the door for further discovery as we enter this new era of precision gravitational physics.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/collquium-42023/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Colloquium-04.20.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230413T130000
DTEND;TZID=America/New_York:20230413T140000
DTSTAMP:20240216T112442Z
CREATED:20230824T182821Z
LAST-MODIFIED:20240216T112442Z
UID:10001811-1681390800-1681394400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Control of actin cable length by decelerated growth and network geometry
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Shane McInally\, Brandeis \nTitle: Control of actin cable length by decelerated growth and network geometry \nAbstract: The sizes of many subcellular structures are coordinated with cell size to ensure that these structures meet the functional demands of the cell. In eukaryotic cells\, these subcellular structures are often membrane-bound organelles\, whose volume is the physiologically important aspect of their size. Scaling organelle volume with cell volume can be explained by limiting pool mechanisms\, wherein a constant concentration of molecular building blocks enables subcellular structures to increase in size proportionally with cell volume. However\, limiting pool mechanisms cannot explain how the size of linear subcellular structures\, such as cytoskeletal filaments\, scale with the linear dimensions of the cell. Recently\, we discovered that the length of actin cables in budding yeast (used for intracellular transport) precisely matches the length of the cell in which they are assembled. Using mathematical modeling and quantitative imaging of actin cable growth dynamics\, we found that as the actin cables grow longer\, their extension rates slow (or decelerate)\, enabling cable length to match cell length. Importantly\, this deceleration behavior is cell-length dependent\, allowing cables in longer cells to grow faster\, and therefore reach a longer length before growth stops at the back of the cell. In addition\, we have unexpectedly found that cable length is specified by cable shape. Our imaging analysis reveals that cables progressively taper as they extend from the bud neck into the mother cell\, and further\, this tapering scales with cell length. Integrating observations made for tapering actin networks in other systems\, we have developed a novel mathematical model for cable length control that recapitulates our quantitative experimental observations. Unlike other models of size control\, this model does not require length-dependent rates of assembly or disassembly. Instead\, feedback control over the length of the cable is an emergent property due to the cross-linked and bundled architecture of the actin filaments within the cable. This work reveals a new strategy that cells use to coordinate the size of their internal parts with their linear dimensions. Similar design principles may control the size and scaling of other subcellular structures whose physiologically important dimension is their length.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/am-41323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Active-Matter-Seminar-04.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230413T093000
DTEND;TZID=America/New_York:20230413T103000
DTSTAMP:20240228T081413Z
CREATED:20230818T042744Z
LAST-MODIFIED:20240228T081413Z
UID:10001260-1681378200-1681381800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Resolving the photon ring
DESCRIPTION:General Relativity Seminar \nSpeaker: Shahar Hadar (University of Haifa) \nTitle: Resolving the photon ring \nAbstract: In the past few years\, the Event Horizon Telescope has released the first close-up interferometric images of two supermassive black holes\, M87* and SgrA*. It is believed that within these images is embedded a fine\, yet-unresolved brightness enhancement called the photon ring. The ring is a universal consequence of strong lensing by the black hole and thereby conveys information on its spacetime geometry\, potentially providing a new independent avenue for tests of general relativity in the strong-field regime. In the talk I will briefly review the theory of the photon ring and its corresponding spacetime region\, the photon shell\, which governs the universal lensing structure. I will then describe some current efforts and future prospects for resolving the ring\, which include both the construction of transformative new instruments and the development of novel analysis methods. Focusing on the latter\, I will present an upcoming proposal to use spectro-temporal autocorrelations in signals emitted from black hole environs as a probe of strong lensing effects.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/gr_41323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-GR-Seminar-04.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230412T153000
DTEND;TZID=America/New_York:20230412T163000
DTSTAMP:20240228T094844Z
CREATED:20230808T174934Z
LAST-MODIFIED:20240228T094844Z
UID:10001195-1681313400-1681317000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Large deviations of Selberg’s central limit theorem
DESCRIPTION:Probability Seminar \n\nSpeaker: Emma Bailey (CUNY) \nTitle: Large deviations of Selberg’s central limit theorem \nAbstract: Selberg’s CLT concerns the typical behaviour of the Riemann zeta function and shows that the random variable $\Re \log \zeta(1/2 + i t)$\, for a uniformly drawn $t$\, behaves as a Gaussian random variable with a particular variance.  It is natural to investigate how far into the tails this Gaussianity persists\, which is the topic of this work. There are also very close connections to similar problems in circular unitary ensemble characteristic polynomials.  It transpires that a `multiscale scheme’ can be applied to both situations to understand these questions of large deviations\, as well as certain maxima and moments. In this talk I will focus more on the techniques we apply to approach this problem and I will assume no number theoretic knowledge. This is joint work with Louis-Pierre Arguin.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/probability-41223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Probability-Seminar-04.12.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230412T123000
DTEND;TZID=America/New_York:20230412T133000
DTSTAMP:20240215T103145Z
CREATED:20230817T182227Z
LAST-MODIFIED:20240215T103145Z
UID:10001281-1681302600-1681306200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Unexpected Uses of Neural Networks: Field Theory and Metric Flows  
DESCRIPTION:Speaker: James Halverson (Northeastern University)\n \nTitle: Unexpected Uses of Neural Networks: Field Theory and Metric Flows\nAbstract:  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 in a different duality frame. Then\, I will review recent progress in approximating Calabi-Yau metrics as neural networks and cast that story into the language of neural tangent kernel theory\, yielding a theoretical understanding of neural network metric flows induced by gradient descent and recovering famous metric flows\, such as Perelman’s formulation of Ricci flow\, in particular limits.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/colloquium12523/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/02CMSA-Colloquium-04.12.2023.png
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230411T120000
DTEND;TZID=America/New_York:20230411T130000
DTSTAMP:20240118T070619Z
CREATED:20230817T171211Z
LAST-MODIFIED:20240118T070619Z
UID:10001241-1681214400-1681218000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Spectral gap and two-point functions in spin glasses
DESCRIPTION:Member Seminar \nSpeaker: Changji Xu \nTitle: Spectral gap and two-point functions in spin glasses \nAbstract: Many have worked on spin glass models over the past 50 years\, including physicists\, mathematicians\, and computers. A question that arises is whether computers yield dependable simulation results. In this talk\, I will discuss some recent mathematical progress on spectral gap and two-point functions in spin glasses models.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/member-seminar-41123/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230410T110000
DTEND;TZID=America/New_York:20230410T120000
DTSTAMP:20240215T101627Z
CREATED:20230730T190732Z
LAST-MODIFIED:20240215T101627Z
UID:10001161-1681124400-1681128000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Swampland bounds on the abelian gauge sectors
DESCRIPTION:Swampland Seminar \nSpeaker: Seung-Joo Lee (IBS Daejeon)\n\nTitle: Swampland bounds on the abelian gauge sectors \nAbstract: In this talk we will derive various bounds on the 0-form and the 1-form abelian gauge sectors of gravitational effective theories in 6 dimensions with minimal supersymmetry. We will start by considering 6-dimensional F-theory vacua with at least one tensor multiplets\, to bound for them the number of the (0-form) U(1) gauge factors as well as the cyclic orders of the 1-form discrete gauge factors. While the two abelian gauge sectors may look rather independent\, we will observe that both are heavily constrained by the solitonic heterotic strings present in the spectrum\, which provide a common intuition for the derived bounds. Building upon the heterotic intuition\, we will also try extending the arena to address analogous bounds for all F-theory vacua in 6 dimensions and even beyond. If time permits\, several applications and future directions of research will be discussed at the end of the talk.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/swampland_41023/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Swampland Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Swampland-Seminar-04.10.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230407T120000
DTEND;TZID=America/New_York:20230407T130000
DTSTAMP:20240122T075759Z
CREATED:20230825T085705Z
LAST-MODIFIED:20240122T075759Z
UID:10001304-1680868800-1680872400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Modular graph forms and iterated integrals in string amplitudes
DESCRIPTION:Algebraic Geometry in String Theory Seminar \nSpeaker: Oliver Schlotterer (Uppsala University) \nTitle: Modular graph forms and iterated integrals in string amplitudes \nAbstract: I will discuss string amplitudes as a laboratory for special functions and period integrals that drive fruitful cross-talk with particle physicists and mathematicians. At genus zero\, integration over punctures on a disk or sphere worldsheet generates multiple zeta values in the low-energy expansion of open- and closed-string amplitudes. At genus one\, closed-string amplitudes introduce infinite families of non-holomorphic modular forms through the integration over torus punctures known as modular graph forms. The latter inspired Francis Brown’s alternative construction of non-holomorphic modular forms in the mathematics literature via iterated integrals\, and I will report on recent progress in clarifying their connection with modular graph forms.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/agst-4723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230407T100000
DTEND;TZID=America/New_York:20230407T113000
DTSTAMP:20240110T071718Z
CREATED:20230802T170222Z
LAST-MODIFIED:20240110T071718Z
UID:10001174-1680861600-1680867000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Enhancing Detection of Topological Order by Local Error Correction
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Nishad Maskara (Harvard) \nTitle: Enhancing Detection of Topological Order by Local Error Correction \nAbstract: The exploration of topologically-ordered states of matter is a long-standing goal at the interface of several subfields of the physical sciences. Such states feature intriguing physical properties such as long-range entanglement\, emergent gauge fields and non-local correlations\, and can aid in realization of scalable fault-tolerant quantum computation. However\, these same features also make creation\, detection\, and characterization of topologically-ordered states particularly challenging. Motivated by recent experimental demonstrations\, we introduce a new paradigm for quantifying topological states—locally error-corrected decoration (LED)—by combining methods of error correction with ideas of renormalization-group flow. Our approach allows for efficient and robust identification of topological order\, and is applicable in the presence of incoherent noise sources\, making it particularly suitable for realistic experiments. We demonstrate the power of LED using numerical simulations of the toric code under a variety of perturbations\, and we subsequently apply it to an experimental realization of a quantum spin liquid using a Rydberg-atom quantum simulator.  Finally\, we illustrate how LED can be applied to more general phases including non-abelian topological orders. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/qm_4723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-04.07.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230406T093000
DTEND;TZID=America/New_York:20230406T103000
DTSTAMP:20240119T051939Z
CREATED:20230818T042449Z
LAST-MODIFIED:20240119T051939Z
UID:10001259-1680773400-1680777000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Rough solutions of the relativistic Euler equations
DESCRIPTION:General Relativity Seminar \nSpeaker: Sifan Yu\, Vanderbilt University \nTitle: Rough solutions of the relativistic Euler equations \nAbstract: I will discuss recent works on the relativistic Euler equations with dynamic vorticity and entropy. We use a new formulation of the equations\, which has geo-analytic structures. In this geometric formulation\, we decompose the flow into geometric “sound-wave part” and “transport-div-curl part”. This allows us to derive sharp results about the dynamics\, including the existence of low-regularity solutions. Then\, I will discuss the results of rough solutions of the relativistic Euler equations and the role that nonlinear geometric optics plays in the framework. Our main result is that the Sobolev norm $H^{2+}$ of the variables in the “wave-part” and the H\”older norm $C^{0\,0+}$ of the variables in the “transport-part” can be controlled in terms of initial data for short times. We note that the Sobolev norm assumption $H^{2+}$ is the optimal result for the variables in the “wave-part.” This talk will include the main ideas of the proof\, as well as a comparison of the relativistic and non-relativistic scenarios.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/gr_4623/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
END:VEVENT
END:VCALENDAR