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X-WR-CALDESC:Events for CMSA
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DTSTART;TZID=America/New_York:20211118T175200
DTEND;TZID=America/New_York:20211118T185200
DTSTAMP:20240304T065227Z
CREATED:20230801T181638Z
LAST-MODIFIED:20240304T065227Z
UID:10002545-1637257920-1637261520@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Macroscopic properties of buyer-seller networks in online marketplaces
DESCRIPTION:Abstract:  Online marketplaces are the main engines of legal and illegal e-commerce\, yet the aggregate properties of buyer-seller networks behind them are poorly understood. We analyse two datasets containing 245M transactions (16B USD)  between 2010 and 2021 involving online marketplaces: 28 dark web marketplaces (DWM)\, unregulated markets whose main currency is Bitcoin\, and 144 product markets of one regulated e-commerce platform. We show how transactions in online marketplaces exhibit strikingly similar patterns of aggregate behavior despite significant differences in language\, products\, time\, regulation\, oversight\, and technology. We find remarkable regularities in the distributions of (i) transaction amounts\, (ii) number of transactions\, (iii) inter-event times\, (iv) time between first and last transactions. We then show how buyer behavior is affected by the memory of past interactions\, and draw on these observations to propose a model of network formation able to reproduce the main stylised facts of the data. Our findings have important implications for understanding market power on online marketplaces as well as inter-marketplace competition.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/macroscopic-properties-of-buyer-seller-networks-in-online-marketplaces/
LOCATION:MA
CATEGORIES:Special Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220406T133000
DTEND;TZID=America/New_York:20220406T143000
DTSTAMP:20240228T114223Z
CREATED:20230801T182005Z
LAST-MODIFIED:20240228T114223Z
UID:10001163-1649251800-1649255400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:On the wave turbulence theory for a stochastic KdV type equation
DESCRIPTION:Random Matrix & Probability Theory Seminar\n\nSpeaker: Minh-Binh TRAN (SMU & MIT)\n\n\n\n\n\nLocation: CMSA\, Room G02 \nTitle: On the wave turbulence theory for a stochastic KdV type equation \nAbstract: We report recent progress\, in collaboration with Gigliola Staffilani (MIT)\, on the problem of deriving kinetic equations from dispersive equations. To be more precise\, starting from the stochastic  Zakharov-Kuznetsov equation\, a multidimensional KdV type equation on a hypercubic lattice\, we provide a derivation of the 3-wave kinetic equation. We show that the two point correlation function can be asymptotically expressed as the solution of the 3-wave  kinetic equation at the kinetic limit under very general assumptions: the initial condition is out of equilibrium\, the dimension is  $d\ge 2$\, the smallness of the nonlinearity $\lambda$ is allowed to be independent of the size of the lattice\, the weak noise is chosen not to compete with the weak nonlinearity and not to inject energy into the equation.  Unlike the cubic nonlinear Schrodinger equation\, for which such a general result is commonly expected without the noise\, the kinetic description of the deterministic lattice ZK equation is unlikely to happen. One of the key reasons is that the dispersion relation of the lattice ZK equation leads to a singular manifold\, on which not only 3-wave interactions but also all m-wave interactions are allowed to happen. This phenomenon has been first observed by Lukkarinen  as a counterexample for which one of the main tools to derive kinetic equations from wave equations (the suppression of crossings) fails to hold true.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/random_4622/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230929T140000
DTEND;TZID=America/New_York:20230929T150000
DTSTAMP:20240223T103610Z
CREATED:20240223T103610Z
LAST-MODIFIED:20240223T103610Z
UID:10002848-1695996000-1695999600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Topological modular forms and heretoric string theory
DESCRIPTION:Special Seminar\n\n\n\n\n\nSpeaker: Mayuko Yamashita\, Kyoto University \n\nTitle: Topological modular forms and heretoric string theory \nAbstract: In this talk I will explain my works with Y. Tachikawa to study anomaly in heterotic string theory via homotopy theory\, especially the theory of Topological Modular Forms (TMF). TMF is an E-infinity ring spectrum which is conjectured by Stolz-Teichner to classify two-dimensional supersymmetric quantum field theories in physics. In the previous work (https://arxiv.org/abs/2108.13542)\, we proved the vanishing of anomalies in heterotic string theory mathematically by using TMF. \nFurthermore\, we have a recent update (https://arxiv.org/abs/2305.06196) on the previous work. Because of the vanishing result\, we can consider a secondary transformation of spectra\, which is shown to coincide with the Anderson self-duality morphism of TMF. This allows us to detect subtle torsion phenomena in TMF by differential-geometric ways\, and leads us to new conjectures on the relation between VOAs and TMF. \n\n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/ss_92923/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Special-Seminar-09.29.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240516T150000
DTEND;TZID=America/New_York:20240516T160000
DTSTAMP:20240510T175234Z
CREATED:20240510T170616Z
LAST-MODIFIED:20240510T175234Z
UID:10003387-1715871600-1715875200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Geometry of Generalized Lienard Equations\, Contact Geometry and Metriplectic Structure
DESCRIPTION:Speaker: Partha Guha\, Khalifa University\, Abu Dhabi \nTitle: Geometry of Generalized Lienard Equations\, Contact Geometry and Metriplectic Structure \nAbstract: We start with a self-contained brief review of the construction of non-standard Lagrangian and Hamiltonian structures using the Jacobi Last Multiplier for the (generalized) reduced Lienard equations satisfying Chiellini integrability condition\, we then explore its connection with the contact Hamiltonian mechanics. We also explore Lienard equations\, of reaction-diffusion class and conformal (or contact) Hamiltonian Structures. Finally\, we present the geometric formulation of the generalized Lienard equations in terms of metriplectic structure. \nJoint work with Jose Carinena and Anindya Ghose Choudhury
URL:https://live-hu-cmsa-222.pantheonsite.io/event/geometry_51624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Geometry-and-Physics-Seminar-05.16.2024.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240604T140000
DTEND;TZID=America/New_York:20240604T150000
DTSTAMP:20240813T164205Z
CREATED:20240523T135748Z
LAST-MODIFIED:20240813T164205Z
UID:10003391-1717509600-1717513200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Corks for exotic diffeomorphisms
DESCRIPTION:Speaker: Slava Krushkal\, University of Virginia \nTitle: Corks for exotic diffeomorphisms \nAbstract: Exotic smooth structures on simply-connected 4-manifolds are known to be related by cork twists: cutting out and re-gluing certain smooth contractible submanifolds. Work in progress\, joint with A. Mukherjee\, M. Powell\, and T. Warren\, provides a localization result for exotic diffeomorphisms of 4-manifolds. I will also discuss applications to known examples of exotic diffeomorphisms. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/corks-for-exotic-diffeomorphisms/
LOCATION:CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/LowDimTop.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240604T160000
DTEND;TZID=America/New_York:20240604T170000
DTSTAMP:20240813T164318Z
CREATED:20240523T135549Z
LAST-MODIFIED:20240813T164318Z
UID:10003390-1717516800-1717520400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Can embedding problems be used to distinguish S^4 from other (possible) homotopy 4-spheres?
DESCRIPTION:Speaker: Michael Freedman\, Harvard CMSA \nTitle: Can embedding problems be used to distinguish S^4 from other (possible) homotopy 4-spheres? \nAbstract: There are approaches in the literature (using Khovanov homology) to detecting a homotopy 4-sphere\, via the 4-ball genus of knots. I’d like to suggest moving from surfaces to 3-manifolds\, that is approaching the problem by considering the which closed 3-manifolds embed.  Embedding in the actual S^4 implies a curious condition on the possible Heegaard diagrams for the 3-manifold. I’ll explain this condition and speculate on how it might be exploited.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/can-embedding-problems-be-used-to-distinguish-s4-from-other-possible-homotopy-4-spheres/
LOCATION:CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/LowDimTop.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241205T103000
DTEND;TZID=America/New_York:20241205T120000
DTSTAMP:20241119T150954Z
CREATED:20241119T141605Z
LAST-MODIFIED:20241119T150954Z
UID:10003621-1733394600-1733400000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Quantum Cellular Automata
DESCRIPTION:Special Seminar \nSpeaker: Jeongwan Haah\, Stanford University \nTitle: Quantum Cellular Automata \nAbstract: A discrete time evolution on lattice systems that has a notion of lightcone is called a quantum cellular automaton. Lattice translation in 1D is a well-known example of QCA that is nontrivial in the sense that it is not a local Hamiltonian evolution. In higher dimensions\, more subtle QCA are found in relation to certain topological phases of matter\, but the scope of all QCA is far from being fully determined. I will report the status of our understanding on this subject\, emphasizing the role of locally generated simple subalgebras.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/seminar_12524/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Special-Seminar-12.5.2024.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20260911T143000
DTEND;TZID=America/New_York:20260911T153000
DTSTAMP:20260914T223220Z
CREATED:20260909T172459Z
LAST-MODIFIED:20260914T223220Z
UID:10004042-1789137000-1789140600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:CMSA Special Lecture: New Math + AI Developments in Fluid Mechanics
DESCRIPTION:CMSA Special Lecture\nTime: 2:30 pm ET\nDate: Friday\, Sep. 11\, 2026\nLocation: Harvard Science Center Hall A & via Zoom Webinar \n  \nLecture Video \n \n  \nWith the announcement this week that AI has finished off a solution to one of the Millennium Prize Problems\, the Harvard CMSA will host this special lecture to review recent developments on the existence and smoothness of solutions to the Navier–Stokes equation. \n  \nSpeaker: Javier Gomez-Serrano\, Brown University \nTitle: New Math + AI Developments in Fluid Mechanics \nAbstract: In this talk I will discuss recent progress on finite-time singularity formation for several fluid equations\, from model problems to the Navier–Stokes and Euler systems themselves. I will put this progress in context and close with the recently announced resolution of the Navier–Stokes existence and smoothness problem\, via an explicit construction exhibiting finite-time blow-up from smooth data alongside closely related\, independently obtained blow-up results for forced Euler. Both rely on an AI-assisted proof search\, marking a new mode of mathematical discovery for problems of this depth. \n  \nThis lecture will be given in person in Science Center Lecture Hall A\, 1 Oxford Street\, Cambridge MA & via Zoom Webinar (registration required). \nZoom Webinar Registration
URL:https://live-hu-cmsa-222.pantheonsite.io/event/navierstokes/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquia & Seminar,Special Lectures,Special Seminar
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/9.11.26_special-lecture.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20260922T140000
DTEND;TZID=America/New_York:20260922T150000
DTSTAMP:20260728T155040Z
CREATED:20260630T154021Z
LAST-MODIFIED:20260728T155040Z
UID:10003954-1790085600-1790089200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:CMSA Special Seminar: Deformations to the Complex Plane\, Novel Asymptotic Techniques\, and the Large t- Asymptotics of the Riemann Zeta Function
DESCRIPTION:CMSA Special Seminar \n \nSpeaker: Thanasis Fokas\, University of Cambridge \nTitle: Deformations to the Complex Plane\, Novel Asymptotic Techniques\, and the Large t-\nAsymptotics of the Riemann Zeta Function \nAbstract: The Unified Transform (also known as the Fokas method) is a powerful new method for\nsolving boundary value problems for linear and for integrable nonlinear PDEs. For linear\nPDEs\, the relevant transform is based on appropriate deformations of certain integrals from\nthe real line to the complex plane. After briefly reviewing this transform\, it will be shown\nthat combining this idea with novel asymptotic techniques has recently led to unexpected\nand exciting results regarding the large t-asymptotic analysis of the celebrated Riemann zeta\nfunction. The following two results will be discussed. First\, a simple formula will be\npresented for the difference of the functions defining the error terms in two historic\nproblems: in Atkinson’s formula and in the formula for the Dirichlet divisor problem; it will\nbe shown that this difference equals π/ 2 plus a function which is simply related to the\nsquare of the Riemann zeta function. Second\, a remarkable integral identity satisfied by the\nRiemann zeta function will be presented; this identity is obtained from an earlier identity\nderived by the speaker via contour deformation in the complex plane. Making crucial use of\nnovel asymptotic techniques obtained jointly with Jonatan Lenells\, the asymptotic analysis\nof this integral equation gives rise to an interesting identity satisfied\, for large t\, by a sum\ngeneralizing the Dirichlet divisor sum. Also\, and more importantly\, it gives rise to a specific\nintegral transform suitable for the large t-asymptotic analysis of the Riemann zeta function. \n 
URL:https://live-hu-cmsa-222.pantheonsite.io/event/fokas/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquia & Seminar,Special Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Special-Seminar-9.22.26.docx-scaled.png
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