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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220926T090000
DTEND;TZID=America/New_York:20220926T103000
DTSTAMP:20260630T103425
CREATED:20240216T113233Z
LAST-MODIFIED:20240229T110730Z
UID:10002766-1664182800-1664188200@cmsa.fas.harvard.edu
SUMMARY:Candidates for Non-Supersymmetric Dualities
DESCRIPTION:Quantum Matter in Mathematics and Physics \nSpeaker: Avner Karasik (University of Cambridge\, UK)\nTitle: Candidates for Non-Supersymmetric Dualities \nAbstract: In the talk I will discuss the possibility and the obstructions of finding non-supersymmetric dualities for 4d gauge theories. I will review consistency conditions based on Weingarten inequalities\, anomalies and large N\, and clarify some subtle points and misconceptions about them. Later I will go over some old and new examples of candidates for non-supersymmetric dualities. The will be based on 2208.07842 \n 
URL:https://cmsa.fas.harvard.edu/event/non-invertible-symmetries-in-nature-2/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-09.26.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220826T090000
DTEND;TZID=America/New_York:20220826T130000
DTSTAMP:20260630T103425
CREATED:20230705T044827Z
LAST-MODIFIED:20250328T145239Z
UID:10000058-1661504400-1661518800@cmsa.fas.harvard.edu
SUMMARY:Big Data Conference 2022
DESCRIPTION:On August 26\, 2022 the CMSA hosted our eighth annual Conference on Big Data. The Big Data Conference features speakers from the Harvard community as well as scholars from across the globe\, with talks focusing on computer science\, statistics\, math and physics\, and economics. \nThe 2022 Big Data Conference took place virtually on Zoom. \nOrganizers: \n\nScott Duke Kominers\, MBA Class of 1960 Associate Professor\, Harvard Business\nHorng-Tzer Yau\, Professor of Mathematics\, Harvard University\nSergiy Verstyuk\, CMSA\, Harvard University\n\nSpeakers: \n\nXiaohong Chen\, Yale\nMiles Cranmer\, Princeton\nJessica Jeffers\, University of Chicago\nDan Roberts\, MIT\n\nSchedule \n\n\n\n\n9:00 am\nConference Organizers\nIntroduction and Welcome\n\n\n9:10 am – 9:55 am\nXiaohong Chen\nTitle: On ANN optimal estimation and inference for policy functionals of nonparametric conditional moment restrictions \nAbstract:  Many causal/policy parameters of interest are expectation functionals of unknown infinite-dimensional structural functions identified via conditional moment restrictions. Artificial Neural Networks (ANNs) can be viewed as nonlinear sieves that can approximate complex functions of high dimensional covariates more effectively than linear sieves. In this talk we present ANN optimal estimation and inference on  policy functionals\, such as average elasticities or value functions\, of unknown structural functions of endogenous covariates. We provide ANN efficient estimation and optimal t based confidence interval for regular policy functionals such as average derivatives in nonparametric instrumental variables regressions. We also present ANN quasi likelihood ratio based inference for possibly irregular policy functionals of general nonparametric conditional moment restrictions (such as quantile instrumental variables models or Bellman equations) for time series data. We conduct intensive Monte Carlo studies to investigate computational issues with ANN based optimal estimation and inference in economic structural models with endogeneity. For economic data sets that do not have very high signal to noise ratios\, there are current gaps between theoretical advantage of ANN approximation theory vs inferential performance in finite samples.\nSome of the results are applied to efficient estimation and optimal inference for average price elasticity in consumer demand and BLP type demand. \nThe talk is based on two co-authored papers:\n(1) Efficient Estimation of Average Derivatives in NPIV Models: Simulation Comparisons of Neural Network Estimators\n(Authors: Jiafeng Chen\, Xiaohong Chen and Elie Tamer)\nhttps://arxiv.org/abs/2110.06763 \n(2) Neural network Inference on Nonparametric conditional moment restrictions with weakly dependent data\n(Authors: Xiaohong Chen\, Yuan Liao and Weichen Wang). \nView/Download Lecture Slides (pdf)\n\n\n10:00 am – 10:45 am\nJessica Jeffers\nTitle: Labor Reactions to Credit Deterioration: Evidence from LinkedIn Activity \nAbstract: We analyze worker reactions to their firms’ credit deterioration. Using weekly networking activity on LinkedIn\, we show workers initiate more connections immediately following a negative credit event\, even at firms far from bankruptcy. Our results suggest that workers are driven by concerns about both unemployment and future prospects at their firm. Heightened networking activity is associated with contemporaneous and future departures\, especially at financially healthy firms. Other negative events like missed earnings and equity downgrades do not trigger similar reactions. Overall\, our results indicate that the build-up of connections triggered by credit deterioration represents a source of fragility for firms.\n\n\n10:50 am – 11:35 am\nMiles Cranmer\nTitle: Interpretable Machine Learning for Physics \nAbstract: Would Kepler have discovered his laws if machine learning had been around in 1609? Or would he have been satisfied with the accuracy of some black box regression model\, leaving Newton without the inspiration to discover the law of gravitation? In this talk I will explore the compatibility of industry-oriented machine learning algorithms with discovery in the natural sciences. I will describe recent approaches developed with collaborators for addressing this\, based on a strategy of “translating” neural networks into symbolic models via evolutionary algorithms. I will discuss the inner workings of the open-source symbolic regression library PySR (github.com/MilesCranmer/PySR)\, which forms a central part of this interpretable learning toolkit. Finally\, I will present examples of how these methods have been used in the past two years in scientific discovery\, and outline some current efforts. \nView/Download Lecture Slides (pdf) \n\n\n11:40 am – 12:25 pm\nDan Roberts\nTitle: A Statistical Model of Neural Scaling Laws \nAbstract: Large language models of a huge number of parameters and trained on near internet-sized number of tokens have been empirically shown to obey “neural scaling laws” for which their performance behaves predictably as a power law in either parameters or dataset size until bottlenecked by the other resource. To understand this better\, we first identify the necessary properties allowing such scaling laws to arise and then propose a statistical model — a joint generative data model and random feature model — that captures this neural scaling phenomenology. By solving this model using tools from random matrix theory\, we gain insight into (i) the statistical structure of datasets and tasks that lead to scaling laws (ii) how nonlinear feature maps\, i.e the role played by the deep neural network\, enable scaling laws when trained on these datasets\, and (iii) how such scaling laws can break down\, and what their behavior is when they do. A key feature is the manner in which the power laws that occur in the statistics of natural datasets are translated into power law scalings of the test loss\, and how the finite extent of such power laws leads to both bottlenecks and breakdowns. \nView/Download Lecture Slides (pdf) \n \n\n\n12:30 pm\nConference Organizers\nClosing Remarks\n\n\n\n\n  \nInformation about last year’s conference can be found here.
URL:https://cmsa.fas.harvard.edu/event/big-data-conference-2022/
LOCATION:Virtual
CATEGORIES:Big Data Conference,Conference,Event
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/Big-Data-2022_web.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220816T100000
DTEND;TZID=America/New_York:20220816T113000
DTSTAMP:20260630T103425
CREATED:20240215T100758Z
LAST-MODIFIED:20240229T092227Z
UID:10002738-1660644000-1660649400@cmsa.fas.harvard.edu
SUMMARY:Transport in large-N critical Fermi surface
DESCRIPTION:Speaker: Haoyu Guo (Harvard) \nTitle: Transport in large-N critical Fermi surface\n\nAbstract: A Fermi surface coupled to a scalar field can be described in a 1/N expansion by choosing the fermion-scalar Yukawa coupling to be random in the N-dimensional flavor space\, but invariant under translations. We compute the conductivity of such a theory in two spatial dimensions for a critical scalar. We find a Drude contribution\, and show that a previously proposed \omega^{-2/3} contribution to the optical conductivity at frequency \omega has vanishing co-efficient. We also describe the influence of impurity scattering of the fermions\, and find that while the self energy resembles a marginal Fermi liquid\, the resistivity behaves like a Fermi liquid. Arxiv references: 2203.04990\, 2207.08841
URL:https://cmsa.fas.harvard.edu/event/qm_81622/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220810T090000
DTEND;TZID=America/New_York:20220810T100000
DTSTAMP:20260630T103425
CREATED:20240215T095253Z
LAST-MODIFIED:20240229T090234Z
UID:10002731-1660122000-1660125600@cmsa.fas.harvard.edu
SUMMARY:Recent Advances on Maximum Flows and Minimum-Cost Flows
DESCRIPTION:Interdisciplinary Science Seminar\n\n\n\n\n\n\nSpeaker: Yang P. Liu\n\n\nTitle: Recent Advances on Maximum Flows and Minimum-Cost Flows\n\nAbstract: We survey recent advances on computing flows in graphs\, culminating in an almost linear time algorithm for solving minimum-cost flow and several other problems to high accuracy on directed graphs. Along the way\, we will discuss intuitions from linear programming\, graph theory\, and data structures that influence these works\, and the resulting natural open problems. \nBio: Yang P. Liu is a final-year graduate student at Stanford University. He is broadly interested in the efficient design of algorithms\, particularly flows\, convex optimization\, and online algorithms. For his work\, he has been awarded STOC and ITCS best student papers.
URL:https://cmsa.fas.harvard.edu/event/iss_81022/
LOCATION:Virtual
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220707T103000
DTEND;TZID=America/New_York:20220707T123000
DTSTAMP:20260630T103425
CREATED:20240215T100432Z
LAST-MODIFIED:20240229T091815Z
UID:10002737-1657189800-1657197000@cmsa.fas.harvard.edu
SUMMARY:Anomalies\, dynamics and phases in strongly-coupled chiral gauge theories: Recent developments
DESCRIPTION:Speaker: Kenichi Konishi (UNIPI.IT) \nTitle: Anomalies\, dynamics and phases in strongly-coupled chiral gauge theories: Recent developments \nAbstract: After many years of efforts\, still very little is known today about the physics of strongly-coupled chiral gauge theories in four dimensions\, in spite of an important role they might play in the physics of fundamental interactions beyond the standard SU(3)xSU(2)xU(1) model. This is in stark contrast with the vectorlike gauge theories for which we have many solid results\, thanks to some exact theorems\, to the lattice simulation studies\, to the Seiberg-Witten exact solution of N=2 supersymmetric gauge theories\, and last\, but not the least\, to the real-world strong-interaction phenomenology and experimental tests of Quantum Chromodynamics. \nThe purpose of this seminar is to discuss the results of our recent efforts to improve the understanding of the strongly-coupled chiral gauge theories. Among the main tools of analysis are the consideration of anomalies. We use both the conventional ’t Hooft anomaly-matching ideas\, and new\, more stringent constraints coming from the generalized anomalies involving some higher-form symmetries. Also\, the so-called strong anomalies\, little considered in the context of chiral gage theories\, are found to carry significant implications. \nAs the playground we study several classes of SU(N) gauge theories\, the so-called Bars-Yankielowicz models\, the generalized Georgi-Glashow models\, as well as a few other simple theories with the fermions in complex\, anomaly-free representations of the color SU(N). \nColor-flavor-locked dynamical Higgs phase and dynamical Abelianization\, emerge\, among others\, as two particularly interesting possible phases the system can flow into in the infrared\, depending on the matter fermion content of the model.
URL:https://cmsa.fas.harvard.edu/event/qm_7722/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220521T090000
DTEND;TZID=America/New_York:20220612T170000
DTSTAMP:20260630T103425
CREATED:20230706T182609Z
LAST-MODIFIED:20240229T094452Z
UID:10000147-1653123600-1655053200@cmsa.fas.harvard.edu
SUMMARY:2022 Summer Introduction to Mathematical Research
DESCRIPTION:The Math Department and Harvard’s Center of Mathematical Sciences and Applications (CMSA) will be running a math program/course for mathematically minded undergraduates this summer. The course will be run by Dr. Yingying Wu from CMSA. Here is a description: \nSummer Introduction to Mathematical Research (sponsored by CMSA and the Harvard Math Department) \nIn this course\, we will start with an introduction to computer programming\, algorithms\, and scientific computing. Then we will discuss topics in topology\, classical geometry\, projective geometry\, and differential geometry\, and see how they can be applied to machine learning. We will go on to discuss fundamental concepts of deep learning\, different deep neural network models\, and mathematical interpretations of why deep neural networks are effective from a calculus viewpoint. We will conclude the course with a gentle introduction to cryptography\, introducing some of the iconic topics: Yao’s Millionaires’ problem\, zero-knowledge proof\, the multi-party computation algorithm\, and its proof. \nThe program hopes to provide several research mentors from various disciplines who will give some of the course lectures. Students will have the opportunity to work with one of the research mentors offered by the program. \nPrerequisites: Basic coding ability in some programming language (C/Python/Matlab or CS50 experience). Some background in calculus and linear algebra is needed too. If you wish to work with a research mentor on differential geometry\, more background in geometry such as from Math 132 or 136 will be useful. If you wish to work with a research mentor on computer science\, coding experience mentioned above will be very useful. If you wish to work with a medical scientist\, some background in life science or basic organic chemistry is recommended. \nThe course will meet 3 hours per week for 7 weeks via Zoom on days and times that will be scheduled for the convenience of the participants. There may be other times to be arranged for special events. \nThis program is only open to current Harvard undergraduates; both Mathematics concentrators and non-math concentrators are invited to apply. People already enrolled in a Math Department summer tutorial are welcome to partake in this program also. As with the summer tutorials\, there is no association with the Harvard Summer School; and neither Math concentration credit nor Harvard College credit will be given for completing this course. This course has no official Harvard status and enrollment does not qualify you for any Harvard-related perks (such as a place to live if you are in Boston over the summer.) \nHowever: As with the summer tutorials\, those enrolled are eligible* to receive a stipend of $700\, and if you are a Mathematics concentrator\, any written paper for the course can be submitted to fulfill the Math Concentration third-year paper requirement. (*The stipend is not available for people already receiving a stipend via the Math Department’s summer tutorial program\, nor is it available for PRISE participants or participants in the Herchel Smith program.) \nIf you wish to join this program\, please email Cliff Taubes (chtaubes@math.harvard.edu). The enrollment is limited\, so don’t wait too long to apply.
URL:https://cmsa.fas.harvard.edu/event/2022-summer-introduction-to-mathematical-research/
LOCATION:Virtual
CATEGORIES:Event,Programs
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-2-600x338-1-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220518T160000
DTEND;TZID=America/New_York:20220518T173000
DTSTAMP:20260630T103425
CREATED:20240215T101105Z
LAST-MODIFIED:20240813T162341Z
UID:10002739-1652889600-1652895000@cmsa.fas.harvard.edu
SUMMARY:Boundary conditions and LSM anomalies of conformal field theories in 1+1 dimensions
DESCRIPTION:Speaker: Linhao Li (ISSP\, U Tokyo) \nTitle: Boundary conditions and LSM anomalies of conformal field theories in 1+1 dimensions \nAbstract: In this talk\, we will study a relationship between conformally invariant boundary conditions and anomalies of conformal field theories (CFTs) in 1+1 dimensions. For a given CFT with a global symmetry\, we consider symmetric gapping potentials which are relevant perturbations to the CFT. If a gapping potential is introduced only in a subregion of the system\, it provides a certain boundary condition to the CFT. From this equivalence\, if there exists a Cardy boundary state which is invariant under a symmetry\, then the CFT can be gapped with a unique ground state by adding the corresponding gapping potential. This means that the symmetry of the CFT is anomaly free. Using this approach\, we will systematically deduce the anomaly-free conditions for various types of CFTs with several different symmetries. When the symmetry of the CFT is anomalous\, it implies a Lieb-Schultz-Mattis type ingappability of the system. Our results are consistent with\, where available\, known results in the literature. Moreover\, we extend the discussion to other symmetries including spin groups and generalized time-reversal symmetries. As an application\, we propose 1d LSM theorem involving magnetic space group symmetries on the lattice. The extended LSM theorems apply to systems with a broader class of spin interactions\, such as Dzyaloshinskii-Moriya interactions and chiral three-spin interactions.
URL:https://cmsa.fas.harvard.edu/event/5-18-2022-quantum-matter-in-mathematics-and-physics-2/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-05.18.22-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220518T160000
DTEND;TZID=America/New_York:20220518T173000
DTSTAMP:20260630T103425
CREATED:20240214T095418Z
LAST-MODIFIED:20240813T163304Z
UID:10002651-1652889600-1652895000@cmsa.fas.harvard.edu
SUMMARY:The Generalized Landau Paradigm (a review of generalized symmetries in condensed matter)
DESCRIPTION:Abstract: Recent advances in our understanding of symmetry in quantum many-body systems offer the possibility of a generalized Landau paradigm that encompasses all equilibrium phases of matter. This talk will be an elementary review of some of these developments\, based on: https://arxiv.org/abs/2204.03045
URL:https://cmsa.fas.harvard.edu/event/5-18-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-05.18.22-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220509T130000
DTEND;TZID=America/New_York:20220509T140000
DTSTAMP:20260630T103425
CREATED:20230730T181939Z
LAST-MODIFIED:20240214T102113Z
UID:10001150-1652101200-1652104800@cmsa.fas.harvard.edu
SUMMARY:Inflation and light Dark Matter constraints from the Swampland
DESCRIPTION:Abstract: I will explore the interplay between Swampland conjectures and models of inflation and light Dark Matter. To that end\, I will briefly review the weak gravity conjecture (WGC) and the related Festina Lente (FL) bound. These have implications for light darkly and milli-charged particles and can disfavor a large portion of parameter space. The FL bound also implies strong restrictions on the field content of our universe during inflation and presents an opportunity for inflationary model building. At the same time\, it rules out some popular models like chromo-natural inflation and gauge-flation. Finally\, I will review  another Swampland conjecture related to Stückelberg photon masses and discuss its implications for astro-particle physics.
URL:https://cmsa.fas.harvard.edu/event/5-9-2022-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220429T093000
DTEND;TZID=America/New_York:20220429T110000
DTSTAMP:20260630T103425
CREATED:20240215T100221Z
LAST-MODIFIED:20240229T090935Z
UID:10002735-1651224600-1651230000@cmsa.fas.harvard.edu
SUMMARY:Machine Learning the Gravity Equation for International Trade
DESCRIPTION:Member Seminar \nSpeaker: Sergiy Verstyuk \nTitle: Machine Learning the Gravity Equation for International Trade \nAbstract: We will go through modern deep learning methods and existing approaches to their interpretation. Next\, I will describe a graph neural network framework. You will also be introduced to an economic analog of gravity. Finally\, we will see how these tools can help understand observed trade flows between 181 countries over 68 years. [Joint work with Michael R. Douglas.]
URL:https://cmsa.fas.harvard.edu/event/4-29-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220428T130000
DTEND;TZID=America/New_York:20220428T143000
DTSTAMP:20260630T103425
CREATED:20230824T174429Z
LAST-MODIFIED:20240304T081149Z
UID:10001813-1651150800-1651156200@cmsa.fas.harvard.edu
SUMMARY:Building active nematic and active polar liquids out of biological machines
DESCRIPTION:Speaker: Guillaume Duclos (Brandeis)\n\n\nTitle: Building active nematic and active polar liquids out of biological machines\nAbstract: Active matter describes out-of-equilibrium materials composed of motile building blocks that convert free energy into mechanical work. The continuous input of energy at the particle scale liberates these systems from the constraints of thermodynamic equilibrium\, leading to emergent collective behaviors not found in passive materials. In this talk\, I will describe our recent efforts to build simple active systems composed of purified proteins and identify generic emergent behaviors in active systems. I will first discuss two distinct activity-driven instabilities in suspensions of microtubules and molecular motors. Second\, I will describe a new model system for polar fluid whose collective dynamics are driven by the non-equilibrium turnover of actin filaments. Our results illustrate how biomimetic materials can serve as a platform for studying non-equilibrium statistical mechanics\, as well as shine light on the physical mechanisms that regulate self-organization in living matter. \n  \nVideo (Youtube)
URL:https://cmsa.fas.harvard.edu/event/building-active-nematic-and-active-polar-liquids-out-of-biological-machines/
LOCATION:Virtual
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-04.28.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220428T103000
DTEND;TZID=America/New_York:20220428T120000
DTSTAMP:20260630T103425
CREATED:20240214T101152Z
LAST-MODIFIED:20240229T112257Z
UID:10002661-1651141800-1651147200@cmsa.fas.harvard.edu
SUMMARY:Aspects of 4d supersymmetric dynamics and geometry
DESCRIPTION:Abstract: We will overview the program of geometrically engineering four dimensional supersymmetric QFTs as compactifications of six dimensional SCFTs. In particular we will discuss how strong coupling phenomena in four dimensions\, such as duality and emergence of symmetry\, can be better understood in such geometric constructions.
URL:https://cmsa.fas.harvard.edu/event/4-28-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-04.28.22-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220426T093000
DTEND;TZID=America/New_York:20220426T103000
DTSTAMP:20260630T103425
CREATED:20230825T080553Z
LAST-MODIFIED:20240304T061555Z
UID:10001296-1650965400-1650969000@cmsa.fas.harvard.edu
SUMMARY:Modularity of mirror families of log Calabi–Yau surfaces
DESCRIPTION:Abstract:   In “Mirror symmetry for log Calabi–Yau surfaces I\,” given a smooth log Calabi–Yau surface pair (Y\,D)\, Gross–Hacking–Keel constructed its mirror family as the spectrum of an explicit algebra whose structure coefficients are determined by the enumerative geometry of (Y\,D). As a follow-up of the work of Gross–Hacking–Keel\, when (Y\,D) is positive\, we prove the modularity of the mirror family as the universal family of log Calabi-Yau surface pairs deformation equivalent to (Y\,D) with at worst du Val singularities. As a corollary\, we show that the ring of regular functions of a smooth affine log Calabi–Yau surface has a canonical basis of theta functions. The key step towards the proof of the main theorem is the application of the tropical construction of singular cycles and explicit formulas of period integrals given in the work of Helge–Siebert. This is joint work with Jonathan Lai.
URL:https://cmsa.fas.harvard.edu/event/modularity-of-mirror-families-of-log-calabi-yau-surfaces/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-04.26.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220422T093000
DTEND;TZID=America/New_York:20220422T230000
DTSTAMP:20260630T103425
CREATED:20230706T180541Z
LAST-MODIFIED:20250328T200643Z
UID:10000096-1650619800-1650668400@cmsa.fas.harvard.edu
SUMMARY:CMSA/Tsinghua Math-Science Literature Lecture: Three Introductory Lectures on Game Theory for Mathematicians: Auction Theory
DESCRIPTION:Eric Maskin (Harvard University) Three Introductory Lectures on Game Theory for Mathematicians \nApril 22\, 2022 | 9:30 – 11:00 am ET \nTitle: Auction Theory \nAbstract: Equivalences among four standard auctions: the high-bid auction (the high bidder wins and pays her bid); the second-bid auction (the high bidder wins and pays the second-highest bid); the Dutch auction (the auctioneer lowers the price successively until some bidder is willing to pay); and the English auction (bidders raise their bids successively until no one wants to bid higher). \nTalk chairs: Scott Kominers\, Sergiy Verstyuk \nSLIDES | VIDEO Answers to Questions from Talks 2 and 3
URL:https://cmsa.fas.harvard.edu/event/maskin_gametheory2022_3/
LOCATION:Virtual
CATEGORIES:Math Science Literature Lecture Series,Public Lecture,Special Lectures
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/Mathlit_MASKIN-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220420T093000
DTEND;TZID=America/New_York:20220420T110000
DTSTAMP:20260630T103425
CREATED:20230706T180319Z
LAST-MODIFIED:20250328T200302Z
UID:10000095-1650447000-1650452400@cmsa.fas.harvard.edu
SUMMARY:CMSA/Tsinghua Math-Science Literature Lecture: Three Introductory Lectures on Game Theory for Mathematicians: Mechanism Design
DESCRIPTION:Eric Maskin (Harvard University) Three Introductory Lectures on Game Theory for Mathematicians \nApril 20\, 2022 | 9:30 – 11:00 am ET \nTitle: Mechanism Design \nAbstract: Given a social goal\, under what circumstances can we design a game to achieve that goal? \nTalk chairs: Scott Kominers\, Sergiy Verstyuk \nSLIDES | VIDEO
URL:https://cmsa.fas.harvard.edu/event/maskin_gametheory2022_2/
LOCATION:Virtual
CATEGORIES:Event,Math Science Literature Lecture Series,Public Lecture,Special Lectures
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/Mathlit_MASKIN-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220419T093000
DTEND;TZID=America/New_York:20220419T103000
DTSTAMP:20260630T103426
CREATED:20230825T080357Z
LAST-MODIFIED:20240304T061057Z
UID:10001295-1650360600-1650364200@cmsa.fas.harvard.edu
SUMMARY:Equivariant Verlinde algebra and quantum K-theory of the moduli space of vortices
DESCRIPTION:Abstract:  In studying complex Chern-Simons theory on a Seifert manifold\, Gukov-Pei proposed an equivariant Verlinde formula\, a one-parameter deformation of the celebrated Verlinde formula. It computes\, among many things\, the graded dimension of the space of holomorphic sections of (powers of) a natural determinant line bundle over the Hitchin moduli space. Gukov-Pei conjectured that the equivariant Verlinde numbers are equal to the equivariant quantum K-invariants of a non-compact (Kahler) quotient space studied by Hanany-Tong. \nIn this talk\, I will explain the setup of this conjecture and its proof via wall-crossing of moduli spaces of (parabolic) Bradlow-Higgs triples. It is based on work in progress with Wei Gu and Du Pei.
URL:https://cmsa.fas.harvard.edu/event/equivariant-verlinde-algebra-and-quantum-k-theory-of-the-moduli-space-of-vortices/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-04.19.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220418T130000
DTEND;TZID=America/New_York:20220418T140000
DTSTAMP:20260630T103426
CREATED:20230730T181614Z
LAST-MODIFIED:20240301T072639Z
UID:10001149-1650286800-1650290400@cmsa.fas.harvard.edu
SUMMARY:4/18/2022 Swampland Seminar
DESCRIPTION:Open mic Swampland Discussion \nTopic: Cobordism
URL:https://cmsa.fas.harvard.edu/event/4-18-2022-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220418T093000
DTEND;TZID=America/New_York:20220418T110000
DTSTAMP:20260630T103426
CREATED:20230706T180022Z
LAST-MODIFIED:20250328T200252Z
UID:10000094-1650274200-1650279600@cmsa.fas.harvard.edu
SUMMARY:CMSA/Tsinghua Math-Science Literature Lecture: Three Introductory Lectures on Game Theory for Mathematicians: Game Theory Basics and Classical Existence Theorems
DESCRIPTION:Eric Maskin (Harvard University) Three Introductory Lectures on Game Theory for Mathematicians \nApril 18\, 2022 | 9:30 – 11:00 am ET \nTitle: Game Theory Basics and Classical Existence Theorems \nAbstract: Games in extensive and normal form. Equilibrium existence theorems by Nash\, von Neumann\, and Zermelo \nTalk chairs: Scott Kominers\, Sergiy Verstyuk \nSLIDES | VIDEO \n 
URL:https://cmsa.fas.harvard.edu/event/maskin_gametheory2022_1/
LOCATION:Virtual
CATEGORIES:Event,Math Science Literature Lecture Series,Public Lecture,Special Lectures
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/Mathlit_MASKIN-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220414T093000
DTEND;TZID=America/New_York:20220414T110000
DTSTAMP:20260630T103426
CREATED:20240214T102053Z
LAST-MODIFIED:20240813T162915Z
UID:10002666-1649928600-1649934000@cmsa.fas.harvard.edu
SUMMARY:Cancellation of the vacuum energy and Weyl anomaly in the standard model\, and a two-sheeted\, CPT-symmetric universe
DESCRIPTION:Youtube video \n  \n\n\nAbstract: I will explain a mechanism to cancel the vacuum energy and both terms in the Weyl anomaly in the standard model of particle physics\, using conformally-coupled dimension-zero scalar fields.  Remarkably\, given the standard model gauge group SU(3)xSU(2)xU(1)\, the cancellation requires precisely 48 Weyl spinors — i.e. three generations of standard model fermions\, including right-handed neutrinos.  Moreover\, the scalars possess a scale-invariant power spectrum\, suggesting a new explanation for the observed primordial density perturbations in cosmology (without the need for inflation). \nAs context\, I will also introduce a related cosmological picture in which this cancellation mechanism plays an essential role.  Our universe seems to be dominated by radiation at early times\, and positive vacuum energy at late times.  Taking the symmetry and analyticity properties of such a universe seriously suggests a picture in which spacetime has two sheets\, related by a symmetry that\, in turn\, selects a preferred (CPT-symmetric) vacuum state for the quantum fields that live on the spacetime.  This line of thought suggests new explanations for a number of observed properties of the universe\, including: its homogeneity\, isotropy and flatness; the arrow of time; several properties of the primordial perturbations; and the nature of dark matter (which\, in this picture\, is a right-handed neutrino\, radiated from the early universe like Hawking radiation from a black hole).  It also makes a number of testable predictions. \n(Based on recent\, and ongoing\, work with Neil Turok: arXiv:1803.08928\, arXiv:2109.06204\, arXiv:2110.06258\, arXiv:2201.07279.)
URL:https://cmsa.fas.harvard.edu/event/4-14-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-04.14.22-1583x2048-1-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220414T093000
DTEND;TZID=America/New_York:20220414T103000
DTSTAMP:20260630T103426
CREATED:20240214T083016Z
LAST-MODIFIED:20240301T112943Z
UID:10002589-1649928600-1649932200@cmsa.fas.harvard.edu
SUMMARY:Global existence and stability of de Sitter-like solutions to the Einstein-Yang-Mills equations in spacetime dimensions n≥4
DESCRIPTION:Abstract: In this talk\, we briefly introduce our recent work on establishing the global existence and stability to the future of non-linear perturbation of de Sitter-like solutions to the Einstein-Yang-Mills system in n≥4 spacetime dimension. This generalizes Friedrich’s (1991) Einstein-Yang-Mills stability results in dimension n=4 to all higher dimensions. This is a joint work with Todd A. Oliynyk and Jinhua Wang.
URL:https://cmsa.fas.harvard.edu/event/4-14-2022-general-relativity-seminar/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220413T203000
DTEND;TZID=America/New_York:20220413T220000
DTSTAMP:20260630T103426
CREATED:20240214T102340Z
LAST-MODIFIED:20240301T063645Z
UID:10002668-1649881800-1649887200@cmsa.fas.harvard.edu
SUMMARY:Why is the mission impossible? Decoupling the mirror Ginsparg-Wilson fermions in the lattice models for two-dimensional abelian chiral gauge theories
DESCRIPTION:Youtube Video \nAbstract: It has been known that the four-dimensional abelian chiral gauge theories of an anomaly-free set of Wely fermions can be formulated on the lattice preserving the exact gauge invariance and the required locality property in the framework of the Ginsparg- Wilson relation. This holds true in two dimensions. However\, in the related formulation including the mirror Ginsparg-Wilson fermions\, it has been argued that the mirror fermions do not decouple: in the 3450 model with Dirac- and Majorana-Yukawa couplings to XY-spin field\, the two- point vertex function of the (external) gauge field in the mirror sector shows a singular non-local behavior in the so-called ParaMagnetic Strong-coupling(PMS) phase. \nWe re-examine why the attempt seems a “Mission: Impossible” in the 3450 model. We point out that the effective operators to break the fermion number symmetries (’t Hooft operators plus others) in the mirror sector do not have sufficiently strong couplings even in the limit of large Majorana-Yukawa couplings. We also observe that the type of Majorana-Yukawa term considered there is singular in the large limit due to the nature of the chiral projection of the Ginsparg-Wilson fermions\, but a slight modification without such singularity is allowed by virtue of the very nature. \nWe then consider a simpler four-flavor axial gauge model\, the 14(-1)4 model\, in which the U(1)A gauge and Spin(6)( SU(4)) global symmetries prohibit the bilinear terms\, but allow the quartic terms to break all the other continuous mirror-fermion symmetries. This model in the weak gauge-coupling limit is related to the eight-flavor Majorana Chain with a reduced SO(6)xSO(2) symmetry in Euclidean path-integral formulation. We formulate the model so that it is well-behaved and simplified in the strong-coupling limit of the quartic operators. Through Monte-Carlo simulations in the weak gauge-coupling limit\, we show a numerical evidence that the two-point vertex function of the gauge field in the mirror sector shows a regular local behavior. \nFinally\, by gauging a U(1) subgroup of the U(1)A× Spin(6)(SU(4)) of the previous model\, we formulate the 21(−1)3 chiral gauge model and argue that the induced effective action in the mirror sector satisfies the required locality property. This gives us “A New Hope” for the mission to be accomplished.
URL:https://cmsa.fas.harvard.edu/event/4-13-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-04.13.22-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220412T115800
DTEND;TZID=America/New_York:20220412T125800
DTSTAMP:20260630T103426
CREATED:20230825T080118Z
LAST-MODIFIED:20240304T061648Z
UID:10001294-1649764680-1649768280@cmsa.fas.harvard.edu
SUMMARY:Applications of Higher Determinant Map
DESCRIPTION:Abstract: In this talk I will explain the construction of a determinant map for Tate objects and two applications: (i) to construct central extensions of iterated loop groups and (ii) to produce a determinant theory on certain ind-schemes. For that I will introduce some aspects of the theory of Tate objects in a couple of contexts.
URL:https://cmsa.fas.harvard.edu/event/applications-of-higher-determinant-map/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220411T100000
DTEND;TZID=America/New_York:20220411T110000
DTSTAMP:20260630T103426
CREATED:20230730T181035Z
LAST-MODIFIED:20240301T072853Z
UID:10001148-1649671200-1649674800@cmsa.fas.harvard.edu
SUMMARY:Type IIB flux compactifications with $h^{1\,1}=0$
DESCRIPTION:Abstract: We revisit type IIB flux compactification that are mirror dual to type IIA on rigid Calabi-Yau manifolds. We find a variety of interesting new solutions\, like fully stabilized Minkowski vacua and infinite families of AdS$_4$ solutions with arbitrarily large numbers of spacetime filling D3 branes. We discuss how these solutions fit into the web of swampland conjectures.
URL:https://cmsa.fas.harvard.edu/event/4-11-2021-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220408T084500
DTEND;TZID=America/New_York:20220408T101500
DTSTAMP:20260630T103426
CREATED:20240214T084325Z
LAST-MODIFIED:20240301T105121Z
UID:10002595-1649407500-1649412900@cmsa.fas.harvard.edu
SUMMARY:Synthetic Regression Discontinuity: Estimating Treatment Effects using Machine Learning
DESCRIPTION:Speaker: Jörn Boehnke \nTitle: Synthetic Regression Discontinuity: Estimating Treatment Effects using Machine Learning \nAbstract:  In the standard regression discontinuity setting\, treatment assignment is based on whether a unit’s observable score (running variable) crosses a known threshold.  We propose a two-stage method to estimate the treatment effect when the score is unobservable to the econometrician while the treatment status is known for all units.  In the first stage\, we use a statistical model to predict a unit’s treatment status based on a continuous synthetic score.  In the second stage\, we apply a regression discontinuity design using the predicted synthetic score as the running variable to estimate the treatment effect on an outcome of interest.  We establish conditions under which the method identifies the local treatment effect for a unit at the threshold of the unobservable score\, the same parameter that a standard regression discontinuity design with known score would identify. We also examine the properties of the estimator using simulations\, and propose the use machine learning algorithms to achieve high prediction accuracy.  Finally\, we apply the method to measure the effect of an investment grade rating on corporate bond prices by any of the three largest credit ratings agencies.  We find an average 1% increase in the prices of corporate bonds that received an investment grade as opposed to a non-investment grade rating.
URL:https://cmsa.fas.harvard.edu/event/4-8-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220407T093000
DTEND;TZID=America/New_York:20220407T110000
DTSTAMP:20260630T103426
CREATED:20240214T102601Z
LAST-MODIFIED:20240301T063834Z
UID:10002669-1649323800-1649329200@cmsa.fas.harvard.edu
SUMMARY:Lattice Gauge Theory View of Toric Codes\, X-cube\, and More
DESCRIPTION:Youtube Video \n  \nAbstract: Exactly solvable spin models such as toric codes and X-cube model have heightened our understanding of spin liquids and topological matter in two and three dimensions. Their exact solvability\, it turns out\, is rooted in the existence of commuting generators in their parent lattice gauge theory (LGT). We can understand the toric codes as Higgsed descendants of the rank-1 U(1) LGT in two and three dimensions\, and the X-cube model as that of rank-2 U(1) LGT in three dimensions. Furthermore\, the transformation properties of the gauge fields in the respective LGT is responsible for\, and nearly determines the structure of the effective field theory (EFT) of the accompanying matter fields. We show how to construct the EFT of e and m particles in the toric codes and of fractons and lineons in the X-cube model by following such an idea. Recently we proposed some stabilizer Hamiltonians termed rank-2 toric code (R2TC) and F3 model (3D). We will explain what they are\, and construct their EFTs using the gauge principle as guidance. The resulting field theory of the matter fields are usually highly interacting and exhibit unusual conservation laws. Especially for the R2TC\, we demonstrate the existence of what we call the “dipolar braiding statistics” and outline the accompanying field theory which differs from the usual BF field theory of anyon braiding. \nReferences:\n[1] “Model for fractions\, fluxons\, and free verte excitations”\, JT Kim\, JH Han\, Phys. Rev. B 104\, 115128 (2021)\n[1] “Rank-2 toric code in two dimensions”\, YT Oh\, JT Kim\, EG Moon\, JH Han\, Phys. Rev. B 105\, 045128 (2022)\n[2] “Effective field theory for the exactly solvable stabilizer spin models”\, JT Kim\, YT Oh\, JH Han\, in preparation.\n[3] “Effective field theory of dipolar braiding statistics in two dimensions”\, YT Oh\, JT Kim\, JH Han\, in preparation.
URL:https://cmsa.fas.harvard.edu/event/4-7-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.07.2022-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220406T213000
DTEND;TZID=America/New_York:20220406T223000
DTSTAMP:20260630T103426
CREATED:20240214T080706Z
LAST-MODIFIED:20240301T112919Z
UID:10002581-1649280600-1649284200@cmsa.fas.harvard.edu
SUMMARY:Gopakumar-Vafa type invariants of holomorphic symplectic 4-folds
DESCRIPTION:Abstract: Gromov-Witten invariants of holomorphic symplectic 4-folds vanish and one can consider the corresponding reduced theory. In this talk\, we will explain a definition of Gopakumar-Vafa type invariants for such a reduced theory. These invariants are conjectured to be integers and have alternative interpretations using sheaf theoretic moduli spaces. Our conjecture is proved for the product of two K3 surfaces\, which naturally leads to a closed formula of Fujiki constants of Chern classes of tangent bundles of Hilbert schemes of points on K3 surfaces. On a very general holomorphic symplectic 4-folds of K3^[2] type\, our conjecture provides a Yau-Zaslow type formula for the number of isolated genus 2 curves of minimal degree. Based on joint works with Georg Oberdieck and Yukinobu Toda.
URL:https://cmsa.fas.harvard.edu/event/4-5-2022-joint-harvard-cuhk-ymsc-differential-geometry-seminar/
LOCATION:Virtual
CATEGORIES:Joint Harvard-CUHK-YMSC Differential Geometry
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/20220406_Yalong-CAO_poster.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220406T103000
DTEND;TZID=America/New_York:20220406T120000
DTSTAMP:20260630T103426
CREATED:20240214T102826Z
LAST-MODIFIED:20240301T064048Z
UID:10002671-1649241000-1649246400@cmsa.fas.harvard.edu
SUMMARY:Late time von Neumann entropy and measurement-induced phase transition
DESCRIPTION:Youtube Video \n  \nAbstract: Characterizing many-body entanglement is one of the most important problems in quantum physics. We present our studies on the steady state von Neumann entropy and its transition in Brownian SYK models. For unitary evolution\, we show that the correlations between different replicas account for the Page curve at late time\, and a permutation group structure emerges in the large-N calculation. In the presence of measurements\, we find a transition of von Neumann entropy from volume-law to area-law by increasing the measurement rate. We show that a proper replica limit can be taken\, which shows that the transition occurs at the point of replica symmetry breaking.
URL:https://cmsa.fas.harvard.edu/event/4-6-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.06.2022-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220405T093000
DTEND;TZID=America/New_York:20220405T103000
DTSTAMP:20260630T103426
CREATED:20230825T075918Z
LAST-MODIFIED:20240304T082856Z
UID:10001293-1649151000-1649154600@cmsa.fas.harvard.edu
SUMMARY:Regularized integrals on Riemann surfaces and correlations functions in 2d chiral CFTs
DESCRIPTION:Abstract: I will report a recent approach of regularizing divergent integrals on configuration spaces of Riemann surfaces\, introduced by Si Li and myself in arXiv:2008.07503\, with an emphasis on genus one cases where modular forms arise naturally. I will then talk about some applications in studying correlation functions in 2d chiral CFTs\, holomorphic anomaly equations\, etc. If time permits\, I will also mention a more algebraic formulation of this notion of regularized integrals in terms of mixed Hodge structures. \nThe talk is partially based on joint works with Si Li.
URL:https://cmsa.fas.harvard.edu/event/regularized-integrals-on-riemann-surfaces-and-correlations-functions-in-2d-chiral-cfts/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-04.05.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220404T100000
DTEND;TZID=America/New_York:20220404T230000
DTSTAMP:20260630T103426
CREATED:20230730T180720Z
LAST-MODIFIED:20240301T073634Z
UID:10001147-1649066400-1649113200@cmsa.fas.harvard.edu
SUMMARY:Causality constraints on corrections to Einstein gravity
DESCRIPTION:Swampland Seminar \nSpeakers: Simon Caron-Huot (McGill University) and Julio Parra (Caltech) \n\n\nTitle: Causality constraints on corrections to Einstein gravity \n\nAbstract: We study constraints from causality and unitarity on 2→2 graviton scattering in four-dimensional weakly-coupled effective field theories. Together\, causality and unitarity imply dispersion relations that connect low-energy observables to high-energy data. Using such dispersion relations\, we derive two-sided bounds on gravitational Wilson coefficients in terms of the mass M of new higher-spin states. Our bounds imply that gravitational interactions must shut off uniformly in the limit G→0\, and prove the scaling with M expected from dimensional analysis (up to an infrared logarithm). We speculate that causality\, together with the non-observation of gravitationally-coupled higher-spin states at colliders\, severely restricts modifications to Einstein gravity that could be probed by experiments in the near future.
URL:https://cmsa.fas.harvard.edu/event/4-5-2022-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220401T090000
DTEND;TZID=America/New_York:20220401T103000
DTSTAMP:20260630T103426
CREATED:20240214T084536Z
LAST-MODIFIED:20240301T110938Z
UID:10002596-1648803600-1648809000@cmsa.fas.harvard.edu
SUMMARY:Diffusive growth sourced by topological defects
DESCRIPTION:Member Seminar \nSpeaker: Farzan Vafa \nTitle: Diffusive growth sourced by topological defects \nAbstract: In this talk\, we develop a minimal model of morphogenesis of a surface where the dynamics of the intrinsic geometry is diffusive growth sourced by topological defects. We show that a positive (negative) defect can dynamically generate a cone (hyperbolic cone). We analytically explain features of the growth profile as a function of position and time\, and predict that in the presence of a positive defect\, a bump forms with height profile h(t) ~ t^(1/2) for early times t. To incorporate the effect of the mean curvature\, we exploit the fact that for axisymmetric surfaces\, the extrinsic geometry can be deduced entirely by the intrinsic geometry. We find that the resulting stationary geometry\, for polar order and small bending modulus\, is a deformed football.\nWe apply our framework to various biological systems. In an ex-vivo setting of cultured murine neural progenitor cells\, we show that our framework is consistent with the observed cell accumulation at positive defects and depletion at negative defects. In an in-vivo setting\, we show that the defect configuration consisting of a bound +1 defect state\, which is stabilized by activity\, surrounded by two -1/2 defects can create a stationary ring configuration of tentacles\, consistent with observations of a basal marine invertebrate Hydra
URL:https://cmsa.fas.harvard.edu/event/4-1-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
END:VCALENDAR