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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211203T093000
DTEND;TZID=America/New_York:20211203T103000
DTSTAMP:20260513T012813
CREATED:20240214T072504Z
LAST-MODIFIED:20240301T110847Z
UID:10002558-1638523800-1638527400@cmsa.fas.harvard.edu
SUMMARY:Black Holes\, 2D Gravity\, and Random Matrices
DESCRIPTION:Member Seminar \nSpeaker: Dan Kapec \nTitle: Black Holes\, 2D Gravity\, and Random Matrices \nAbstract: I will discuss old and new connections between black hole physics\, 2D quantum gravity\, and random matrix theory. Black holes are believed to be very complicated\, strongly interacting quantum mechanical systems\, and certain aspects of their Hamiltonians should be well approximated by random matrix theory. The near-horizon effective dynamics of near-extremal black holes is two-dimensional\, and many theories of 2D quantum gravity are known to have random matrix descriptions. All of these expectations were recently borne out in surprising detail with the solution of the Jackiw-Teitelboim (JT) model\, but this result raises more questions than it answers. If time permits\, I will discuss some extensions of these results and possible future directions.
URL:https://cmsa.fas.harvard.edu/event/12-3-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T142800
DTEND;TZID=America/New_York:20211202T152800
DTSTAMP:20260513T012813
CREATED:20240215T094151Z
LAST-MODIFIED:20240301T110349Z
UID:10002725-1638455280-1638458880@cmsa.fas.harvard.edu
SUMMARY:12/2/2021 Interdisciplinary Science Seminar
DESCRIPTION:Title: Polyhomogeneous expansions and Z/2-harmonic spinors branching along graphs \nAbstract: In this talk\, we will first reformulate the linearization of the moduli space of Z/2-harmonic spinorsv branching along a knot. This formula tells us that the kernel and cokernel of the linearization are isomorphic to the kernel and cokernel of the Dirac equation with a polyhomogeneous boundary condition. In the second part of this talk\, I will describe the polyhomogenous expansions for the Z/2-harmonic spinors branching along graphs and formulate the Dirac equation with a suitable boundary condition that can describe the perturbation of graphs with some restrictions. This is joint work with Andriy Haydys and Rafe Mazzeo.
URL:https://cmsa.fas.harvard.edu/event/12-2-2021-interdisciplinary-science-seminar/
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T131500
DTEND;TZID=America/New_York:20211202T143000
DTSTAMP:20260513T012813
CREATED:20240213T113157Z
LAST-MODIFIED:20240304T084850Z
UID:10002504-1638450900-1638455400@cmsa.fas.harvard.edu
SUMMARY:Hydrodynamics and multi-scale order in confluent epithelia
DESCRIPTION:Abstract: In this talk I will review our ongoing theoretical and experimental efforts toward deciphering the hydrodynamic behavior of confluent epithelia. The ability of epithelial cells to collectively flow lies at the heart of a myriad of processes that are instrumental for life\, such as embryonic morphogenesis and wound healing\, but also of life-threatening conditions\, such as metastatic cancer. Understanding the physical origin of these mechanisms requires going beyond the current hydrodynamic theories of complex fluids and introducing a new theoretical framework\, able to account for biomechanical activity as well as for scale-dependent liquid crystalline order.
URL:https://cmsa.fas.harvard.edu/event/hydrodynamics-and-multi-scale-order-in-confluent-epithelia/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T130000
DTEND;TZID=America/New_York:20211202T140000
DTSTAMP:20260513T012813
CREATED:20240214T075408Z
LAST-MODIFIED:20240304T053731Z
UID:10002571-1638450000-1638453600@cmsa.fas.harvard.edu
SUMMARY:Kerr Geodesics and Self-consistent match between Inspiral and Transition-to-merger
DESCRIPTION:Abstract: The two-body motion in General Relativity can be solved perturbatively in the small mass ratio expansion. Kerr geodesics describe the leading order motion. After a short summary of the classification of polar and radial Kerr geodesic motion\, I will consider the inspiral motion of a point particle around the Kerr black hole subjected to the self-force. I will describe its quasi-circular inspiral motion in the radiation timescale expansion. I will describe in parallel the transition-to-merger motion around the last stable circular orbit and prove that it is controlled by the Painlevé transcendental equation of the first kind. I will then prove that one can consistently match the two motions using the method of asymptotically matched expansions.
URL:https://cmsa.fas.harvard.edu/event/12-2-2021-general-relativity-seminar/
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T103000
DTEND;TZID=America/New_York:20211202T120000
DTSTAMP:20260513T012813
CREATED:20240301T083755Z
LAST-MODIFIED:20240301T083839Z
UID:10002887-1638441000-1638446400@cmsa.fas.harvard.edu
SUMMARY:Symmetry in quantum field theory and quantum gravity 2
DESCRIPTION:Speaker: Daniel Harlow (MIT) \nTitle: Symmetry in quantum field theory and quantum gravity 2 \nAbstract: In this talk I will give an overview of semi-recent work with Hirosi Ooguri arguing that three old conjectures about symmetry in quantum gravity are true in the AdS/CFT correspondence.  These conjectures are 1) that there are no global symmetries in quantum gravity\, 2) that dynamical objects transforming in all irreducible representations of any gauge symmetry must exist\, and 3) all internal gauge symmetries must be compact.  Along the way I will need to carefully define what we mean by gauge and global symmetries in quantum field theory and quantum gravity\, which leads to interesting applications in various related fields.  These definitions will be the focus of the first talk\, while the second will apply them to AdS/CFT to prove conjectures 1-3).
URL:https://cmsa.fas.harvard.edu/event/12-2-2021-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-12.02.21-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T103000
DTEND;TZID=America/New_York:20211202T120000
DTSTAMP:20260513T012813
CREATED:20240213T070448Z
LAST-MODIFIED:20240213T070448Z
UID:10002156-1638441000-1638446400@cmsa.fas.harvard.edu
SUMMARY:12/2/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/12-2-21-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211201T160000
DTEND;TZID=America/New_York:20211201T170000
DTSTAMP:20260513T012813
CREATED:20240214T080447Z
LAST-MODIFIED:20240301T112740Z
UID:10002578-1638374400-1638378000@cmsa.fas.harvard.edu
SUMMARY:Lagrangians and mirror symmetry in the Higgs bundle moduli space
DESCRIPTION:Abstract: The talk concerns recent work with Tamas Hausel in asking how SYZ mirror symmetry works for the moduli space of Higgs bundles. Focusing on C^*-invariant Lagrangian submanifolds\, we use the notion of virtual multiplicity as a tool firstly to examine if the Lagrangian is closed\, but  also to open up new features involving finite-dimensional algebras which are deformations of cohomology algebras. Answering some of the questions raised  requires revisiting basic constructions of stable bundles on curves.
URL:https://cmsa.fas.harvard.edu/event/2-1-2021-joint-harvard-cuhk-ymsc-differential-geometry-seminar/
CATEGORIES:Joint Harvard-CUHK-YMSC Differential Geometry
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211201T140000
DTEND;TZID=America/New_York:20211201T143000
DTSTAMP:20260513T012813
CREATED:20230808T175251Z
LAST-MODIFIED:20240515T203641Z
UID:10001200-1638367200-1638369000@cmsa.fas.harvard.edu
SUMMARY:The Principles of Deep Learning Theory
DESCRIPTION:Speaker: Dan Roberts\, MIT & Salesforce \nTitle: The Principles of Deep Learning Theory \nAbstract: Deep learning is an exciting approach to modern artificial intelligence based on artificial neural networks. The goal of this talk is to provide a blueprint — using tools from physics — for theoretically analyzing deep neural networks of practical relevance. This task will encompass both understanding the statistics of initialized deep networks and determining the training dynamics of such an ensemble when learning from data. \nIn terms of their “microscopic” definition\, deep neural networks are a flexible set of functions built out of many basic computational blocks called neurons\, with many neurons in parallel organized into sequential layers. Borrowing from the effective theory framework\, we will develop a perturbative 1/n expansion around the limit of an infinite number of neurons per layer and systematically integrate out the parameters of the network. We will explain how the network simplifies at large width and how the propagation of signals from layer to layer can be understood in terms of a Wilsonian renormalization group flow. This will make manifest that deep networks have a tuning problem\, analogous to criticality\, that needs to be solved in order to make them useful. Ultimately we will find a “macroscopic” description for wide and deep networks in terms of weakly-interacting statistical models\, with the strength of the interactions between the neurons growing with depth-to-width aspect ratio of the network. Time permitting\, we will explain how the interactions induce representation learning. \nThis talk is based on a book\, The Principles of Deep Learning Theory\, co-authored with Sho Yaida and based on research also in collaboration with Boris Hanin. It will be published next year by Cambridge University Press.
URL:https://cmsa.fas.harvard.edu/event/12-1-21-new-technologies-in-mathematics-seminar-series/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-NTM-Seminar-12.01.21.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211201T100000
DTEND;TZID=America/New_York:20211201T113000
DTSTAMP:20260513T012813
CREATED:20240213T070149Z
LAST-MODIFIED:20240213T070149Z
UID:10002153-1638352800-1638358200@cmsa.fas.harvard.edu
SUMMARY:12/1/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/12-1-21-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211201T093000
DTEND;TZID=America/New_York:20211201T103000
DTSTAMP:20260513T012813
CREATED:20240212T104729Z
LAST-MODIFIED:20240502T154527Z
UID:10002012-1638351000-1638354600@cmsa.fas.harvard.edu
SUMMARY:The Hitchin connection for parabolic G-bundles
DESCRIPTION:Speaker: Richard Wentworth\, University of Maryland \nTitle: The Hitchin connection for parabolic G-bundles \nAbstract: For a simple and simply connected complex group G\, I will discuss some elements of the proof of the existence of a flat projective connection on the bundle of nonabelian theta functions on the moduli space of semistable parabolic G-bundles over families of smooth projective curves with marked points. Under the isomorphism with the bundle of conformal blocks\, this connection is equivalent to the one constructed by conformal field theory. This is joint work with Indranil Biswas and Swarnava Mukhopadhyay.
URL:https://cmsa.fas.harvard.edu/event/the-hitchin-connection-for-parabolic-g-bundles/
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-12.01.21-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211130T093000
DTEND;TZID=America/New_York:20211130T103000
DTSTAMP:20260513T012813
CREATED:20240213T065738Z
LAST-MODIFIED:20240213T065738Z
UID:10002146-1638264600-1638268200@cmsa.fas.harvard.edu
SUMMARY:Resistance curvature – a new discrete curvature on graphs
DESCRIPTION:Abstract: The last few decades have seen a surge of interest in building towards a theory of discrete curvature that attempts to translate the key properties of curvature in differential geometry to the setting of discrete objects and spaces. In the case of graphs there have been several successful proposals\, for instance by Lin-Lu-Yau\, Forman and Ollivier\, that replicate important curvature theorems and have inspired applications in a variety of practical settings.\nIn this talk\, I will introduce a new notion of discrete curvature on graphs\, which we call the resistance curvature\, and discuss some of its basic properties. The resistance curvature is defined based on the concept of effective resistance which is a metric between the vertices of a graph and has many other properties such as a close relation to random spanning trees. The rich theory of these effective resistances allows to study the resistance curvature in great detail; I will for instance show that “Lin-Lu-Yau >= resistance >= Forman curvature” in a specific sense\, show strong evidence that the resistance curvature converges to zero in expectation for Euclidean random graphs\, and give a connectivity theorem for positively curved graphs. The resistance curvature also has a naturally associated discrete Ricci flow which is a gradient flow and has a closed-form solution in the case of vertex-transitive and path graphs.\nFinally\, if time permits I will draw a connection with the geometry of hyperacute simplices\, following the work of Miroslav Fiedler.\nThis work was done in collaboration with Renaud Lambiotte.
URL:https://cmsa.fas.harvard.edu/event/resistance-curvature-a-new-discrete-curvature-on-graphs/
CATEGORIES:Combinatorics Physics and Probability
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Combinatorics-Physics-and-Probability-Seminar-11.30.2021-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211130T093000
DTEND;TZID=America/New_York:20211130T103000
DTSTAMP:20260513T012813
CREATED:20230818T050118Z
LAST-MODIFIED:20240122T053703Z
UID:10001285-1638264600-1638268200@cmsa.fas.harvard.edu
SUMMARY:K_2 and Quantum Curves
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/k_2-and-quantum-curves/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211129T130000
DTEND;TZID=America/New_York:20211129T140000
DTSTAMP:20260513T012813
CREATED:20240214T112454Z
LAST-MODIFIED:20240301T075047Z
UID:10002697-1638190800-1638194400@cmsa.fas.harvard.edu
SUMMARY:Scale separated AdS vacua?
DESCRIPTION:Abstract: In this talk I will review massive type IIA flux compactifications that seem to give rise to infinite families of supersymmetric 4d AdS vacua. These vacua provide an interesting testing ground for the swampland program. After reviewing potential shortcomings of this setup\, I will discuss recent progress on overcoming them and getting a better understanding of these solutions.
URL:https://cmsa.fas.harvard.edu/event/11-29-2021-swampland-seminar/
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211124T160000
DTEND;TZID=America/New_York:20211124T170000
DTSTAMP:20260513T012813
CREATED:20240213T065022Z
LAST-MODIFIED:20240226T111010Z
UID:10002133-1637769600-1637773200@cmsa.fas.harvard.edu
SUMMARY:Quantum cohomology as a deformation of symplectic cohomology
DESCRIPTION:Abstract: Let X be a compact symplectic manifold\, and D a normal crossings symplectic divisor in X. We give a criterion under which the quantum cohomology of X is the cohomology of a natural deformation of the symplectic cochain complex of X \ D. The criterion can be thought of in terms of the Kodaira dimension of X (which should be non-positive)\, and the log Kodaira dimension of X \ D (which should be non-negative). We will discuss applications to mirror symmetry. This is joint work with Strom Borman and Umut Varolgunes.
URL:https://cmsa.fas.harvard.edu/event/11-24-21-joint-harvard-cuhk-ymsc-differential-geometry-seminar/
CATEGORIES:Joint Harvard-CUHK-YMSC Differential Geometry
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/20211124_Nick-Sheridan_RESCHEDULED_poster.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211124T103000
DTEND;TZID=America/New_York:20211124T120000
DTSTAMP:20260513T012813
CREATED:20240214T100439Z
LAST-MODIFIED:20240301T084626Z
UID:10002655-1637749800-1637755200@cmsa.fas.harvard.edu
SUMMARY:Multipartitioning topological phases and quantum entanglement
DESCRIPTION:Speaker: Shinsei Ryu (Princeton University) \nTitle: Multipartitioning topological phases and quantum entanglement \nAbstract: We discuss multipartitions of the gapped ground states of (2+1)-dimensional topological liquids into three (or more) spatial regions that are adjacent to each other and meet at points. By considering the reduced density matrix obtained by tracing over a subset of the regions\, we compute various correlation measures\, such as entanglement negativity\, reflected entropy\, and associated spectra. We utilize the bulk-boundary correspondence to achieve such multipartitions and construct the reduced density matrix near the entangling boundaries. We find the fingerprints of topological liquid in these quantities\, such as (universal pieces in) the scaling of the entanglement negativity\, and a non-trivial distribution of the spectrum of the partially transposed density matrix.
URL:https://cmsa.fas.harvard.edu/event/11-24-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-11.24.21-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211124T103000
DTEND;TZID=America/New_York:20211124T120000
DTSTAMP:20260513T012813
CREATED:20240213T065517Z
LAST-MODIFIED:20240213T065517Z
UID:10002141-1637749800-1637755200@cmsa.fas.harvard.edu
SUMMARY:11/24/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-24-21-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211123T093000
DTEND;TZID=America/New_York:20211123T103000
DTSTAMP:20260513T012813
CREATED:20240213T065330Z
LAST-MODIFIED:20240226T111143Z
UID:10002138-1637659800-1637663400@cmsa.fas.harvard.edu
SUMMARY:Prague dimension of random graphs
DESCRIPTION:Abstract: The Prague dimension of graphs was introduced by Nesetril\, Pultr and Rodl in the 1970s: as a combinatorial measure of complexity\, it is closely related to clique edges coverings and partitions. Proving a conjecture of Furedi and Kantor\, we show that the Prague dimension of the binomial random graph is typically of order n/(log n) for constant edge-probabilities. The main new proof ingredient is a Pippenger-Spencer type edge-coloring result for random hypergraphs with large uniformities\, i.e.\, edges of size O(log n).
URL:https://cmsa.fas.harvard.edu/event/11-23-21-combinatorics-physics-and-probability-seminar/
CATEGORIES:Combinatorics Physics and Probability
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Combinatorics-Physics-and-Probability-Seminar-11.23.21-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211123T093000
DTEND;TZID=America/New_York:20211123T103000
DTSTAMP:20260513T012813
CREATED:20240213T064610Z
LAST-MODIFIED:20240213T064610Z
UID:10002127-1637659800-1637663400@cmsa.fas.harvard.edu
SUMMARY:Wall crossing for moduli of stable log varieties
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/wall-crossing-for-moduli-of-stable-log-varieties/
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211122T130000
DTEND;TZID=America/New_York:20211122T140000
DTSTAMP:20260513T012813
CREATED:20240214T091807Z
LAST-MODIFIED:20240301T075427Z
UID:10002616-1637586000-1637589600@cmsa.fas.harvard.edu
SUMMARY:Taming the Landscape
DESCRIPTION:Abstract: In this talk I will introduce a generalized notion of finiteness that provides a structural principle for the set of effective theories that can be consistently coupled to quantum gravity. More concretely\, I will propose a ‘tameness conjecture’ that states that all scalar field spaces and coupling functions that appear in such an effective theory must be definable in an o-minimal structure. The fascinating field of tame geometry has seen much recent progress and I will argue that the results can be used to support the above swampland conjecture. The strongest evidence arises from a new finiteness theorem for the flux landscape which is shown using the tameness of the period map.
URL:https://cmsa.fas.harvard.edu/event/11-22-2021-swampland-seminar/
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211119T130000
DTEND;TZID=America/New_York:20211119T140000
DTSTAMP:20260513T012813
CREATED:20240214T074604Z
LAST-MODIFIED:20240304T053957Z
UID:10002570-1637326800-1637330400@cmsa.fas.harvard.edu
SUMMARY:On Curvature Propagation and ‘Breakdown’ of the Einstein Equations on U(1) Symmetric Spacetimes
DESCRIPTION:strong>Abstract: The analysis of global structure of the Einstein equations for general relativity\, in the context of the initial value problem\, is a difficult and intricate mathematical subject. Any additional structure in their formulation is welcome\, in order to alleviate the problem.  It is expected that the initial value problem of the Einstein equations on spacetimes admitting a translational\, fixed-point free\, spatial U(1) isometry group are globally well-posed. In our previous works\, we discussed the special structure provided by the dimensional reduction of 3+1 dimensional U(1) symmetric Einstein equations to 2+1 Einstein-wave map system and demonstrated global existence in the equivariant case for large data.  In this talk\, after discussing some preliminaries and background\, we shall discuss about yet another structure of the U(1) symmetric Einstein equations\, namely the analogy with Yang-Mills theory via the Cartan formalism and reconcile with the dimensionally reduced field equations. We shall also discuss implications for ‘breakdown’ criteria of U(1) symmetric Einstein equations.
URL:https://cmsa.fas.harvard.edu/event/11-19-2021-general-relativity-seminar/
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211119T093000
DTEND;TZID=America/New_York:20211119T103000
DTSTAMP:20260513T012813
CREATED:20240214T072706Z
LAST-MODIFIED:20240301T110941Z
UID:10002560-1637314200-1637317800@cmsa.fas.harvard.edu
SUMMARY:China’s financial regulatory reform\, financial opening-up\, and Central Bank Digital Currency (CBDC)
DESCRIPTION:Member Seminar \nSpeaker: Kan Lin \nTitle: China’s financial regulatory reform\, financial opening-up\, and Central Bank Digital Currency (CBDC) \nAbstract: In this talk\, I will explain the overall situation of China’s financial industry and review the development of China’s financial regulatory system reform from 1949 to 2021. Then\, I will explain the policies of the 3 stages of financial opening-up\, 2001–08\, 2008–18\, 2018≠present. In particular\, the latest round of opening-up from 2018 has brought great opportunities for foreign institutions. China has the world’s largest banking industry with assets totaling $53 trillion\, and accounts for 1/3 of the growth in global insurance premiums over the next 10 years. I will also introduce the progress of research & development of China’s Central Bank Digital Currency (CBDC\, or E-CNY). By October 2021\, 140 million people had opened E-CNY wallets\, and 1.6 million merchants could accept payments using eCNY wallets\, including utilities\, catering services\, transportation\, retail\, and government services.
URL:https://cmsa.fas.harvard.edu/event/11-19-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T175200
DTEND;TZID=America/New_York:20211118T185200
DTSTAMP:20260513T012813
CREATED:20230801T181638Z
LAST-MODIFIED:20240304T065227Z
UID:10002545-1637257920-1637261520@cmsa.fas.harvard.edu
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://cmsa.fas.harvard.edu/event/macroscopic-properties-of-buyer-seller-networks-in-online-marketplaces/
CATEGORIES:Special Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T143000
DTEND;TZID=America/New_York:20211118T160000
DTSTAMP:20260513T012813
CREATED:20240214T100731Z
LAST-MODIFIED:20240301T090528Z
UID:10002657-1637245800-1637251200@cmsa.fas.harvard.edu
SUMMARY:Exact Eigenstates in Non-Integrable Systems: A violation of the ETH
DESCRIPTION:Speaker: B. Andrei Bernevig (Princeton University) \nTitle: Exact Eigenstates in Non-Integrable Systems: A violation of the ETH \nAbstract: We find that several non-integrable systems exhibit some exact eigenstates that span the energy spectrum from lowest to the highest state. In the AKLT Hamiltonian and in several others “special” non-integrable models\, we are able to obtain the analytic expression of states exactly and to compute their entanglement spectrum and entropy to show that they violate the eigenstate thermalization hypothesis. This represented the first example of ETH violation in a non-integrable system; these types of states have gained notoriety since then as quantum Scars in the context of Rydberg atoms experiments. We furthermore show that the structure of these states\, in most models where they are found is that of an almost spectrum generating algebra which we call Restricted Spectrum Generating Algebra. This includes the (extended) Hubbard model\, as well as some thin-torus limits of Fractional Quantum Hall states. Yet in other examples\, such as the recently found chiral non-linear Luttinger liquid\, their structure is more complicated and not understood.
URL:https://cmsa.fas.harvard.edu/event/11-18-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Quantum-Matter-in-Mathematics-and-Physics-11.18.21-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T143000
DTEND;TZID=America/New_York:20211118T160000
DTSTAMP:20260513T012813
CREATED:20240213T064124Z
LAST-MODIFIED:20240213T064401Z
UID:10002122-1637245800-1637251200@cmsa.fas.harvard.edu
SUMMARY:11/18/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-18-21-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T142500
DTEND;TZID=America/New_York:20211118T152500
DTSTAMP:20260513T012813
CREATED:20240214T075510Z
LAST-MODIFIED:20240301T103505Z
UID:10002572-1637245500-1637249100@cmsa.fas.harvard.edu
SUMMARY:11/18/2021 Interdisciplinary Science Seminar
DESCRIPTION:Title: Amplituhedra\, Scattering Amplitudes and Triangulations \nAbstract: In this talk I will discuss about Amplituhedra – generalizations of polytopes inside the Grassmannian – recently introduced by physicists as new geometric constructions encoding interactions of elementary particles in certain Quantum Field Theories. In particular\, I will explain how the problem of finding triangulations of Amplituhedra is connected to computing scattering amplitudes of N=4 super Yang-Mills theory. Triangulations of polygons are encoded in the associahedron studied by Stasheff in the sixties; in the case of polytopes\, triangulations are captured by secondary polytopes constructed by Gelfand et al. in the nineties. Whereas a “secondary” geometry describing triangulations of Amplituhedra is still not known\, and we pave the way for such studies. We will discuss how the combinatorics of triangulations interplays with T-duality from String Theory\, in connection with a dual object we define – the Momentum Amplituhedron. A generalization of T-duality led us to discover a striking duality between triangulations of Amplituhedra of “m=2” type and the ones of a seemingly unrelated object – the Hypersimplex. The latter is a polytope which has been central in many contexts\, such as matroid theory\, torus orbits in the Grassmannian\, and tropical geometry. Based on joint works with Lauren Williams\, Melissa Sherman-Bennett\, Tomasz Lukowski [arXiv:2104.08254\, arXiv:2002.06164].
URL:https://cmsa.fas.harvard.edu/event/11-18-2021-interdisciplinary-science-seminar/
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211117T093000
DTEND;TZID=America/New_York:20211117T103000
DTSTAMP:20260513T012813
CREATED:20240212T104547Z
LAST-MODIFIED:20240502T154225Z
UID:10002009-1637141400-1637145000@cmsa.fas.harvard.edu
SUMMARY:Curve counting on surfaces and topological strings
DESCRIPTION:Speaker: Andrea Brini\, U Sheffield \nTitle: Curve counting on surfaces and topological strings \nAbstract: Enumerative geometry is a venerable subfield of Mathematics\, with roots dating back to Greek Antiquity and a present inextricably linked with developments in other domains. Since the early 90s\, in particular\, the interaction with String Theory has sent shockwaves through the subject\, giving both unexpected new perspectives and a remarkably powerful\, physics-motivated toolkit to tackle several traditionally hard questions in the field.\nI will survey some recent developments in this vein for the case of enumerative invariants associated to a pair (X\, D)\, with X a complex algebraic surface and D a singular anticanonical divisor in it. I will describe a surprising web of correspondences linking together several a priori distant classes of enumerative invariants associated to (X\, D)\, including the log Gromov-Witten invariants of the pair\, the Gromov-Witten invariants of an associated higher dimensional Calabi-Yau variety\, the open Gromov-Witten invariants of certain special Lagrangians in toric Calabi–Yau threefolds\, the Donaldson–Thomas theory of a class of symmetric quivers\, and certain open and closed Gopakumar-Vafa-type invariants. I will also discuss how these correspondences can be effectively used to provide a complete closed-form solution to the calculation of all these invariants.
URL:https://cmsa.fas.harvard.edu/event/curve-counting-on-surfaces-and-topological-strings/
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.17.21-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T150000
DTEND;TZID=America/New_York:20211116T163000
DTSTAMP:20260513T012813
CREATED:20240214T101038Z
LAST-MODIFIED:20240301T090706Z
UID:10002660-1637074800-1637080200@cmsa.fas.harvard.edu
SUMMARY:Quantum Geometric Aspects of Chiral Twisted Graphene Models
DESCRIPTION:Speaker: Jie Wang (Simons Foundation) \nTitle: Quantum Geometric Aspects of Chiral Twisted Graphene Models \nAbstract: “Moire” materials produced by stacking monolayers with small relative twist angles are of intense current interest for the range of correlated electron phenomena they exhibit. The quench of the kinetic energy means that the interacting physics is controlled by the interplay between the interaction scale and intrinsic quantum geometries of the flat band states\, in particular the Berry curvature and the Fubini-Study metric\, which are in general spatially non-uniform. We show that the analytical solution of the twisted bilayer graphene wavefunction in the chiral limit has a special band geometry\, endowing the Brillouin zone with a complex structure. This talk focus on the origin of the momentum space complex structure\, concrete models that realize it\, and its implications to electron-electron interactions. We first show the momentum space complex structure in Chern number C=1 flatbands implies the Bloch wavefunction to exhibit an exact correspondence to the lowest Landau level in the dual momentum space [2]. We present a generalization of the Haldane pseudopotential concept to deal with interacting problems in these bands and discuss experimental implications [2]. We also present an analytically solvable multi-layer generalized chiral graphene model\, which exhibits arbitrarily high Chern number and ideal quantum geometries [3]. Numerical studies of interacting particles indicate model fractional Chern insulators without Landau level analogues\, characterized by exact degeneracies and infinite particle entanglement spectra gaps [3]. References: \n[1] Jie Wang\, Yunqin Zheng\, Andrew J. Millis\, Jennifer Cano (Phys. Rev. Research 3\, 023155)\n[2] Jie Wang\, Jennifer Cano\, Andrew J. Millis\, Zhao Liu\, Bo Yang (arXiv: 2105.07491\, to appear in PRL)\n[3] Jie Wang\, Zhao Liu (arXiv: 2109.10325)
URL:https://cmsa.fas.harvard.edu/event/11-16-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T150000
DTEND;TZID=America/New_York:20211116T163000
DTSTAMP:20260513T012813
CREATED:20240213T064804Z
LAST-MODIFIED:20240213T064804Z
UID:10002130-1637074800-1637080200@cmsa.fas.harvard.edu
SUMMARY:11/16/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-16-21-quantum-matter-in-mathematics-and-physics/
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T093000
DTEND;TZID=America/New_York:20211116T103000
DTSTAMP:20260513T012813
CREATED:20240214T051424Z
LAST-MODIFIED:20240304T061932Z
UID:10002537-1637055000-1637058600@cmsa.fas.harvard.edu
SUMMARY:Gromov-Witten theory of complete intersections
DESCRIPTION:Abstract: I will describe an inductive algorithm computing Gromov-Witten invariants in all genera with arbitrary insertions of all smooth complete intersections in projective space. The main idea is to show that invariants with insertions of primitive cohomology classes are controlled by their monodromy and by invariants defined without primitive insertions but with imposed nodes in the domain curve. To compute these nodal Gromov-Witten invariants\, we introduce the new notion of nodal relative Gromov-Witten invariants. This is joint work with Hülya Argüz\, Rahul Pandharipande\, and Dimitri Zvonkine (arxiv:2109.13323).
URL:https://cmsa.fas.harvard.edu/event/gromov-witten-theory-of-complete-intersections/
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-Seminar-11.16.21-1-1-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T093000
DTEND;TZID=America/New_York:20211116T103000
DTSTAMP:20260513T012813
CREATED:20240213T063545Z
LAST-MODIFIED:20240223T111731Z
UID:10002118-1637055000-1637058600@cmsa.fas.harvard.edu
SUMMARY:11/16/21 Algebraic Geometry in String Theory
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-16-21-algebraic-geometry-in-string-theory/
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
END:VCALENDAR