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DTSTART;TZID=America/New_York:20221202T110000
DTEND;TZID=America/New_York:20221202T120000
DTSTAMP:20260630T172053
CREATED:20230817T164654Z
LAST-MODIFIED:20240229T111029Z
UID:10001230-1669978800-1669982400@cmsa.fas.harvard.edu
SUMMARY:Compactness and Anticompactness Principles in Set Theory
DESCRIPTION:Member Seminar \nSpeaker: Alejandro Poveda \nTitle: Compactness and Anticompactness Principles in Set Theory \nAbstract: Several fundamental properties in Topology\, Algebra or Logic are expressed in terms of Compactness Principles.For instance\, a natural algebraic question is the following: Suppose that G is an Abelian group whose all small subgroups are free – Is the group G free? If the answer is affirmative one says that compactness holds; otherwise\, we say that compactness fails. Loosely speaking\, a compactness principle is anything that fits the following slogan: Suppose that M is a mathematical structure (a group\, a topological space\, etc) such that all of its small substructures N have certain property $\varphi$; then the ambient structure M has property $\varphi$\, as well. Oftentimes when these questions are posed for infinite sets the problem becomes purely set-theoretical and axiom-sensitive. In this talk I will survey the most paradigmatic instances of compactness and present some related results of mine. If time permits\, I will hint the proof of a recent result (joint with Rinot and Sinapova) showing that stationary reflection and the failure of the Singular Cardinal Hypothesis can co-exist. These are instances of two antagonist set-theoretic principles: the first is a compactness principle while the second is an anti-compactness one. This result solves a question by M. Magidor from 1982.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-12222/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221118T110000
DTEND;TZID=America/New_York:20221118T120000
DTSTAMP:20260630T172053
CREATED:20230809T111725Z
LAST-MODIFIED:20240209T052933Z
UID:10001229-1668769200-1668772800@cmsa.fas.harvard.edu
SUMMARY:Light states in the interior of CY moduli spaces
DESCRIPTION:Member Seminar \nSpeaker: Damian van de Heisteeg \nTitle: Light states in the interior of CY moduli spaces \nAbstract: In string theory one finds that states become massless as one approaches boundaries in Calabi-Yau moduli spaces. In this talk we look in the opposite direction\, that is\, we search for points where the mass gap for these light states is maximized — the so-called desert. In explicit examples we identify these desert points\, and find that they correspond to special points in the moduli space of the CY\, such as orbifold points and rank two attractors.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-111822/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-11.18.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221111T110000
DTEND;TZID=America/New_York:20221111T120000
DTSTAMP:20260630T172053
CREATED:20230809T111328Z
LAST-MODIFIED:20240209T052938Z
UID:10001228-1668164400-1668168000@cmsa.fas.harvard.edu
SUMMARY:Quantum trace and length conjecture for hyperbolic knot
DESCRIPTION:Member Seminar \nSpeaker: Mauricio Romo \nTitle: Quantum trace and length conjecture for hyperbolic knot \nAbstract: I will define the quantum trace map for an ideally triangulated hyperbolic knot complement on S^3. This map assigns an operator to each element L of  the Kauffman Skein module of knot complement.  Motivated by an interpretation of this operator in the context of SL(2\,C) Chern-Simons theory\, one can formulate a ‘length conjecture’ for the hyperbolic length of L.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-111122/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221028T110000
DTEND;TZID=America/New_York:20221028T120000
DTSTAMP:20260630T172053
CREATED:20230809T110603Z
LAST-MODIFIED:20240301T080243Z
UID:10001227-1666954800-1666958400@cmsa.fas.harvard.edu
SUMMARY:Some non-concave dynamic optimization problems in finance
DESCRIPTION:Member Seminar \nSpeaker: Shuaijie Qian (Harvard CMSA) \nTitle: Some non-concave dynamic optimization problems in finance \nAbstract: Non-concave dynamic optimization problems appear in many areas of finance and economics. Most of existing literature solves these problems using the concavification principle\, and derives equivalent\, concave optimization problems whose value functions are still concave. In this talk\, I will present our recent work on some non-concave dynamic optimization problems\, where the concavification principle may not hold and the resulting value function is indeed non-concave. \nThe first work is about the portfolio selection model with capital gains tax and a bitcoin mining model with exit options and technology innovation\, where the average tax basis and the average mining cost serves as an approximation\, respectively. This approximation results in a non-concave value function\, and the associated HJB equation problem turns out to admit infinitely many solutions. We show that the value function is the minimal (viscosity) solution of the HJB equation problem. Moreover\, the penalty method still works and converges to the value function. \nThe second work is about a non-concave utility maximization problem with portfolio constraints. We find that adding bounded portfolio constraints\, which makes the concavification principle invalid\, can significantly affect economic insights in the existing literature. As the resulting value function is likely discontinuous\, we introduce a new definition of viscosity solution\, prove the corresponding comparison principle\, and show that a monotone\, stable\, and consistent finite difference scheme converges to the solution of the utility maximization problem. \n 
URL:https://cmsa.fas.harvard.edu/event/member-seminar-title-tba-6/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221021T110000
DTEND;TZID=America/New_York:20221021T120000
DTSTAMP:20260630T172053
CREATED:20230809T110107Z
LAST-MODIFIED:20240301T080144Z
UID:10001226-1666350000-1666353600@cmsa.fas.harvard.edu
SUMMARY:Explicit Ramsey Graphs and Two Source Extractors
DESCRIPTION:Speaker: David Zuckerman\, Harvard CMSA/University of Texas at Austin \nTitle: Explicit Ramsey Graphs and Two Source Extractors \nAbstract: Ramsey showed that any graph on N nodes contains a clique or independent set of size (log N)/2.  Erdos showed that there exist graphs on N nodes with no clique or independent set of size 2 log N\, and asked for an explicit construction of such graphs.  This turns out to relate to the question of extracting high-quality randomness from two independent low-quality sources.  I’ll explain this connection and our recent exponential improvement in constructing two-source extractors.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-title-tba-5/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.21.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221014T110000
DTEND;TZID=America/New_York:20221014T120000
DTSTAMP:20260630T172053
CREATED:20240214T103536Z
LAST-MODIFIED:20240301T081027Z
UID:10002676-1665745200-1665748800@cmsa.fas.harvard.edu
SUMMARY:Quantum magnet chains and Kashiwara crystals
DESCRIPTION:Speaker: Leonid Rybnikov\, Harvard CMSA/National Research University Higher School of Economics \nTitle: Quantum magnet chains and Kashiwara crystals \nAbstract: Solutions of the algebraic Bethe ansatz for quantum magnet chains are\, generally\, multivalued functions of the parameters of the integrable system. I will explain how to compute some monodromies of solutions of Bethe ansatz for the Gaudin magnet chain. Namely\, the Bethe eigenvectors in the Gaudin model can be regarded as a covering of the Deligne-Mumford moduli space of stable rational curves\, which is unramified over the real locus of the Deligne-Mumford space. The monodromy action of the fundamental group of this space (called cactus group) on the eigenlines can be described very explicitly in purely combinatorial terms of Kashiwara crystals — i.e. combinatorial objects modeling the tensor category of finite-dimensional representations of a semisimple Lie algebra g. More specifically\, this monodromy action is naturally equivalent to the action of the same group by commutors (i.e. combinatorial analog of a braiding) on a tensor product of Kashiwara crystals. This is joint work with Iva Halacheva\, Joel Kamnitzer\, and Alex Weekes.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-101422/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.14.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221007T110000
DTEND;TZID=America/New_York:20221007T120000
DTSTAMP:20260630T172053
CREATED:20240214T105028Z
LAST-MODIFIED:20240301T081713Z
UID:10002681-1665140400-1665144000@cmsa.fas.harvard.edu
SUMMARY:Principal flow\, sub-manifold and boundary
DESCRIPTION:Member Seminar  \nSpeaker: Zhigang Yao \nTitle: Principal flow\, sub-manifold and boundary \nAbstract: While classical statistics has dealt with observations which are real numbers or elements of a real vector space\, nowadays many statistical problems of high interest in the sciences deal with the analysis of data which consist of more complex objects\, taking values in spaces which are naturally not (Euclidean) vector spaces but which still feature some geometric structure. I will discuss the problem of finding principal components to the multivariate datasets\, that lie on an embedded nonlinear Riemannian manifold within the higher-dimensional space. The aim is to extend the geometric interpretation of PCA\, while being able to capture the non-geodesic form of variation in the data. I will introduce the concept of a principal sub-manifold\, a manifold passing through the center of the data\, and at any point on the manifold extending in the direction of highest variation in the space spanned by the eigenvectors of the local tangent space PCA. We show the principal sub-manifold yields the usual principal components in Euclidean space. We illustrate how to find\, use and interpret the principal sub-manifold\, by which a principal boundary can be further defined for data sets on manifolds.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-10722/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220930T110000
DTEND;TZID=America/New_York:20220930T120000
DTSTAMP:20260630T172053
CREATED:20240214T105247Z
LAST-MODIFIED:20240301T081921Z
UID:10002683-1664535600-1664539200@cmsa.fas.harvard.edu
SUMMARY:Kahler geometry in twisted materials
DESCRIPTION:Member Seminar \nSpeaker: Jie Wang \nTitle: Kahler geometry in twisted materials \nAbstract: Flatbands are versatile platform for realizing exotic quantum phases due to the enhanced interactions. The canonical example is Landau level where fractional quantum Hall physics exists. Although interaction is strong\, the fractional quantum Hall effect is relatively well understood thanks to its model wavefunction\, exact parent Hamiltonian\, conformal field theory analogous and other exact aspects. In generic flatbands\, the interacting physics is controlled by the interplay between the interaction scale and intrinsic quantum geometries\, in particular the Berry curvature and the Fubini-Study metric\, which are in general spatially non-uniform. It is commonly believed that the non-uniform geometries destroy these exact properties of fractional quantum Hall physics\, making many-body states less stable in flatbands. \nIn this talk\, I will disprove this common belief by showing a large family of flatbands (ideal flatbands) where quantum geometries can be highly non-uniform\, but still exhibit exact properties such as model wavefunctions\, density algebra\, exact parent Hamiltonians. I will discuss both the theory of ideal flatband\, its experimental realization in Dirac materials as well as implications.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-93022/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220923T110000
DTEND;TZID=America/New_York:20220923T120000
DTSTAMP:20260630T172053
CREATED:20240214T105452Z
LAST-MODIFIED:20240301T083553Z
UID:10002685-1663930800-1663934400@cmsa.fas.harvard.edu
SUMMARY:Random determinants\, the elastic manifold\, and landscape complexity beyond invariance
DESCRIPTION:Member Seminar \nSpeaker: Ben McKenna \nTitle: Random determinants\, the elastic manifold\, and landscape complexity beyond invariance \nAbstract: The Kac-Rice formula allows one to study the complexity of high-dimensional Gaussian random functions (meaning asymptotic counts of critical points) via the determinants of large random matrices. We present new results on determinant asymptotics for non-invariant random matrices\, and use them to compute the (annealed) complexity for several types of landscapes. We focus especially on the elastic manifold\, a classical disordered elastic system studied for example by Fisher (1986) in fixed dimension and by Mézard and Parisi (1992) in the high-dimensional limit. We confirm recent formulas of Fyodorov and Le Doussal (2020) on the model in the Mézard-Parisi setting\, identifying the boundary between simple and glassy phases. Joint work with Gérard Ben Arous and Paul Bourgade.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-title-tba/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220916T110000
DTEND;TZID=America/New_York:20220916T120000
DTSTAMP:20260630T172053
CREATED:20240214T105636Z
LAST-MODIFIED:20240301T084243Z
UID:10002686-1663326000-1663329600@cmsa.fas.harvard.edu
SUMMARY:Derivation of AdS/CFT for Vector Models
DESCRIPTION:Member Seminar\n\nSpeaker: Shai Chester\n\nTitle: Derivation of AdS/CFT for Vector Models\nAbstract: We derive an explicit map at finite N between the singlet sector of the free and critical O(N) and U(N) vector models in any spacetime dimension above two\, and a bulk higher spin theory in anti-de Sitter space in one higher dimension. For the boundary theory\, we use the bilocal formalism of Jevicki et al to restrict to the singlet sector of the vector model. The bulk theory is defined from the boundary theory via our mapping\, and is a consistent quantum higher spin theory with a well defined action. Our mapping relates bilocal operators in the boundary theory to higher spin fields in the bulk\, while single trace local operators in the boundary theory are related to boundary values of higher spin fields. We also discuss generalizations of the map to gauge theories\, and at finite temperature.
URL:https://cmsa.fas.harvard.edu/event/derivation-of-ads-cft-for-vector-models/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220909T120000
DTEND;TZID=America/New_York:20220909T130000
DTSTAMP:20260630T172053
CREATED:20240301T084734Z
LAST-MODIFIED:20240301T084734Z
UID:10002889-1662724800-1662728400@cmsa.fas.harvard.edu
SUMMARY:Duality in Einstein’s Gravity
DESCRIPTION:Title: Duality in Einstein’s Gravity \nAbstract: Electric-Magnetic duality has been a key feature behind our understanding of Quantum Field Theory for over a century. In this talk I will describe a similar property in Einstein’s gravity. The gravitational duality reveals\, in turn\, a wide range of new IR phenomena\, including aspects of the double copy for scattering amplitudes\, asymptotic symmetries and more.
URL:https://cmsa.fas.harvard.edu/event/duality-in-einsteins-gravity/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220513T093000
DTEND;TZID=America/New_York:20220513T110000
DTSTAMP:20260630T172053
CREATED:20240214T084053Z
LAST-MODIFIED:20240301T105004Z
UID:10002593-1652434200-1652439600@cmsa.fas.harvard.edu
SUMMARY:Cobordism and Deformation Class of the Standard Model and Beyond: Proton Stability and Neutrino Mass
DESCRIPTION:Member Seminar \nSpeaker: Juven Wang \nTitle: Cobordism and Deformation Class of the Standard Model and Beyond: Proton Stability and Neutrino Mass \nAbstract: ‘t Hooft anomalies of quantum field theories (QFTs) with an invertible global symmetry G (including spacetime and internal symmetries) in a d-dim spacetime are known to be classified by a d+1-dim cobordism group TPd+1(G)\, whose group generator is a d+1-dim cobordism invariant written as a d+1-dim invertible topological field theory. Deformation class of QFT is recently proposed to be specified by its symmetry G and a d+1-dim invertible topological field theory. Seemly different QFTs of the same deformation class can be deformed to each other via quantum phase transitions. We ask which deformation class controls the 4d ungauged or gauged (SU(3)×SU(2)×U(1))/Zq Standard Model (SM) for q=1\,2\,3\,6 with a continuous or discrete (B−L) symmetry and with also a compatible discrete baryon plus lepton Z_{2Nf} B+L symmetry. (The Z_{2Nf} B+L is discrete due to the ABJ anomaly under the BPST instanton.) We explore a systematic classification of candidate perturbative local and nonperturbative global anomalies of the 4d SM\, including all these gauge and gravitational backgrounds\, via a cobordism theory\, which controls the SM’s deformation class. While many Grand Unified Theories violating the discrete B+L symmetry suffer from the proton decay\, the SM and some versions of Ultra Unification (constrained by Z_{16} class global anomaly that replaces sterile neutrinos with new exotic gapped/gapless topological or conformal sectors) can have a stable proton. Dictated by a Z_2 class global mixed gauge-gravitational anomaly\, there can be a gapless deconfined quantum critical region between Georgi-Glashow and Pati-Salam models — the Standard Model and beyond occur as neighbor phases. We will also comment on a new mechanism to give the neutrino mass via topological field theories and topological defects. Work based on arXiv:2112.14765\, arXiv:2204.08393\, arXiv:2202.13498 and references therein.
URL:https://cmsa.fas.harvard.edu/event/5-13-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220429T093000
DTEND;TZID=America/New_York:20220429T110000
DTSTAMP:20260630T172053
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:20220408T084500
DTEND;TZID=America/New_York:20220408T101500
DTSTAMP:20260630T172053
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:20220401T090000
DTEND;TZID=America/New_York:20220401T103000
DTSTAMP:20260630T172053
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
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220325T093000
DTEND;TZID=America/New_York:20220325T103000
DTSTAMP:20260630T172053
CREATED:20240214T084728Z
LAST-MODIFIED:20240301T110538Z
UID:10002597-1648200600-1648204200@cmsa.fas.harvard.edu
SUMMARY:Periods for singular CY families and Riemann–Hilbert correspondence
DESCRIPTION:Member Seminar \nSpeaker: Tsung-Ju Lee \nTitle: Periods for singular CY families and Riemann–Hilbert correspondence \nAbstract: A GKZ system\, introduced by Gelfand\, Kapranov\, and Zelevinsky\, is a system of partial differential equations generalizing the hypergeometric structure studied by Euler and Gauss. The solutions to GKZ systems have been found applications in various branches of mathematics including number theory\, algebraic geometry and mirror symmetry. In this talk\, I will explain the details and demonstrate how to find the Riemann–Hilbert partner of the GKZ system with a fractional parameter which arises from the B model of singular CY varieties. This is a joint work with Dingxin Zhang.
URL:https://cmsa.fas.harvard.edu/event/3-25-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220318T093000
DTEND;TZID=America/New_York:20220318T103000
DTSTAMP:20260630T172053
CREATED:20240214T084936Z
LAST-MODIFIED:20240301T111106Z
UID:10002599-1647595800-1647599400@cmsa.fas.harvard.edu
SUMMARY:Moduli Space of Metric SUSY Graphs
DESCRIPTION:Member Seminar \nSpeaker: Yingying Wu \nTitle: Moduli Space of Metric SUSY Graphs \nAbstract: SUSY curves are algebraic curves with additional supersymmetric or supergeometric structures. In this talk\, I will present the construction of dual graphs of SUSY curves with Neveu–Schwarz and Ramond punctures. Then\, I will introduce the concept of the metrized SUSY graph and the moduli space of the metric SUSY graphs. I will outline its geometric and topological properties\, followed by a discussion on the connection with the classical case.
URL:https://cmsa.fas.harvard.edu/event/3-18-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220304T093000
DTEND;TZID=America/New_York:20220304T103000
DTSTAMP:20260630T172053
CREATED:20240214T085309Z
LAST-MODIFIED:20240301T111217Z
UID:10002600-1646386200-1646389800@cmsa.fas.harvard.edu
SUMMARY:Positive Mass\, Density\, and Scalar Curvature on Noncompact Manifolds
DESCRIPTION:Member Seminar \nSpeaker: Martin Lesourd \nTitle: Positive Mass\, Density\, and Scalar Curvature on Noncompact Manifolds \nAbstract: I’ll describe some recent work spanning a couple of different papers on the topics mentioned in the title: Positive Mass\, Density\, and Scalar Curvature on Noncompact Manifolds. Two of these are with R. Unger\, Prof. S-T. Yau\, and two others are with R. Unger\, and Prof. D. A. Lee.
URL:https://cmsa.fas.harvard.edu/event/3-4-2022-member-seminar/
LOCATION:Hybrid – G10
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220218T093000
DTEND;TZID=America/New_York:20220218T103000
DTSTAMP:20260630T172053
CREATED:20240301T111555Z
LAST-MODIFIED:20240301T111555Z
UID:10002895-1645176600-1645180200@cmsa.fas.harvard.edu
SUMMARY:Quadratic reciprocity from a family of adelic conformal field theories
DESCRIPTION:Member Seminar \nSpeaker:An Huang \nTitle: Quadratic reciprocity from a family of adelic conformal field theories \nAbstract: This talk aims to provide a physics framework to understand quadratic reciprocity. Specifically\, we consider a deformation of the two-dimensional free scalar field theory by raising the Laplacian to a positive real power. It turns out that the resulting non-local generalized free action is invariant under two commuting actions of the global conformal symmetry algebra\, although it is no longer invariant under the full Witt algebra. The deformation is also closely related to dimensional regularization. Furthermore\, there is an adelic version of this family of conformal field theories\, parameterized by the choice of a number field\, together with a Hecke character. Tate’s thesis gives the Green’s functions of these theories\, and ensures that these Green’s functions satisfy an adelic product formula. In particular\, the local L-factors contribute to the prefactors of these Green’s functions. Quadratic reciprocity turns out to be a consequence of an adelic version of a holomorphic factorization property of this family of theories on a quadratic extension of Q. At the Archimedean place\, the desired holomorphic factorization follows from the global conformal symmetry.
URL:https://cmsa.fas.harvard.edu/event/2-18-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220211T093000
DTEND;TZID=America/New_York:20220211T103000
DTSTAMP:20260630T172053
CREATED:20240214T085713Z
LAST-MODIFIED:20240301T111928Z
UID:10002602-1644571800-1644575400@cmsa.fas.harvard.edu
SUMMARY:Amplituhedra\, Scattering Amplitudes and Triangulations
DESCRIPTION:Member Seminar \nSpeaker: Matteo Parisi \nTitle: 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/2-11-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220204T093000
DTEND;TZID=America/New_York:20220204T103000
DTSTAMP:20260630T172053
CREATED:20240214T090103Z
LAST-MODIFIED:20240301T112029Z
UID:10002603-1643967000-1643970600@cmsa.fas.harvard.edu
SUMMARY:Survey on stability of the positive mass theorem
DESCRIPTION:Member Seminar \nSpeaker: Dan Lee \nTitle: Survey on stability of the positive mass theorem \nAbstract: The Riemannian positive mass theorem states that a complete asymptotically flat manifold with nonnegative scalar curvature must have nonnegative ADM mass. This inequality comes with a rigidity statement that says that if the mass is zero\, then the manifold must be Euclidean space. This naturally leads to the question of stability. In this talk\, I will discuss various results related to this question.
URL:https://cmsa.fas.harvard.edu/event/2-4-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220128T093000
DTEND;TZID=America/New_York:20220128T103000
DTSTAMP:20260630T172053
CREATED:20240214T090436Z
LAST-MODIFIED:20240301T112154Z
UID:10002605-1643362200-1643365800@cmsa.fas.harvard.edu
SUMMARY:Singular Calabi-Yau mirror symmetry
DESCRIPTION:Speaker: Bong Lian \nTitle: Singular Calabi-Yau mirror symmetry \nAbstract: We will consider a class of Calabi-Yau varieties given by cyclic branched covers of a fixed semi Fano manifold. The first prototype example goes back to Euler\, Gauss and Legendre\, who considered 2-fold covers of P1 branched over 4 points. Two-fold covers of P2 branched over 6 lines have been studied more recently by many authors\, including Matsumoto\, Sasaki\, Yoshida and others\, mainly from the viewpoint of their moduli spaces and their comparisons.  I will outline a higher dimensional generalization from the viewpoint of mirror symmetry. We will introduce a new compactification of the moduli space cyclic covers\, using the idea of ‘abelian gauge fixing’ and ‘fractional complete intersections’. This produces a moduli problem that is amenable to tools in toric geometry\, particularly those that we have developed jointly in the mid-90’s with S. Hosono and S.-T. Yau in our study of toric Calabi-Yau complete intersections. In dimension 2\, this construction gives rise to new and interesting identities of modular forms and mirror maps associated to certain K3 surfaces. We also present an essentially complete mirror theory in dimension 3\, and discuss generalization to higher dimensions. The lecture is based on joint work with Shinobu Hosono\, Tsung-Ju Lee\, Hiromichi Takagi\, Shing-Tung Yau.
URL:https://cmsa.fas.harvard.edu/event/1-28-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220121T093000
DTEND;TZID=America/New_York:20220121T103000
DTSTAMP:20260630T172053
CREATED:20240214T090725Z
LAST-MODIFIED:20240301T112306Z
UID:10002607-1642757400-1642761000@cmsa.fas.harvard.edu
SUMMARY:AdS with Scale Separation
DESCRIPTION:Member Seminar \nSpeaker: Daniel Junghans\n\nTitle: AdS with Scale Separation \nAbstract: I will talk about Anti-de Sitter solutions in string theory with a parametric separation between the AdS curvature scale and the Kaluza-Klein scale. In particular\, I will discuss recent progress on computing backreaction corrections in such solutions\, and I will explain how to construct solutions without Romans mass that can be lifted to M-theory.
URL:https://cmsa.fas.harvard.edu/event/1-21-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220114T093000
DTEND;TZID=America/New_York:20220114T103000
DTSTAMP:20260630T172053
CREATED:20240214T090947Z
LAST-MODIFIED:20240301T112406Z
UID:10002609-1642152600-1642156200@cmsa.fas.harvard.edu
SUMMARY:Light strings\, strong coupling\, and the Swampland
DESCRIPTION:Member Seminar \nSpeaker: Max Wiesner\n\nTitle: Light strings\, strong coupling\, and the Swampland \nAbstract: In this talk\, I will start by reviewing central ideas of the so-called Swampland Program. The Swampland Program aims to identify criteria that distinguish low-energy effective field theories\, that can be consistently coupled to quantum gravity\, from those theories that become inconsistent in the presence of quantum gravity. \nIn my talk I will specialize to four-dimensional effective field theories with N=2 and N=1 supersymmetry. In weakly-coupled regions of the scalar field space of such theories\, it has been shown that light strings are crucial to realize certain Swampland criteria. Complementary to that\, the focus of this talk will be on the role of such light strings away from these weak-coupling regimes. In this context\, I will first discuss a relation between light perturbative strings and strong coupling singularities in the Kähler moduli space of 4d N=1 compactifications of F-theory. More precisely\, in regions of moduli space\, in which a critical string classically becomes light\, I will show that non-perturbative corrections yield to strong coupling singularities for D7-brane gauge theories which obstruct weak-coupling limits. Moreover\, I will demonstrate that in the vicinity of this strong coupling singularity\, the critical\, light string in fact leaves the spectrum of BPS strings thereby providing an explanation for the obstruction of the weak coupling limit. \nI will then move on and discuss the backreaction of perturbative strings in 4d EFTs. Away from the string core\, the backreaction of such strings necessarily leads to strong coupling regions where naively the energy stored in the backreaction diverges. I will show how the introduction of additional non-critical strings can regulate this backreaction and how this can be used to study the spectrum of BPS strings and their tensions even beyond weak coupling regions. In this context\, I will demonstrate how the requirement\, that the total string tension should not exceed the Planck scale\, constrains the possible BPS string charges.
URL:https://cmsa.fas.harvard.edu/event/1-14-2022-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211210T093000
DTEND;TZID=America/New_York:20211210T103000
DTSTAMP:20260630T172053
CREATED:20240214T072023Z
LAST-MODIFIED:20240301T110742Z
UID:10002556-1639128600-1639132200@cmsa.fas.harvard.edu
SUMMARY:On the solution space of the Ising perceptron model
DESCRIPTION:Member Seminar  \nSpeaker: Changji Xu \nTitle: On the solution space of the Ising perceptron model \nAbstract:  Consider the discrete cube $\{-1\,1\}^N$ and a random collection of half spaces which includes each half space $H(x) := \{y \in \{-1\,1\}^N: x \cdot y \geq \kappa \sqrt{N}\}$ for $x \in \{-1\,1\}^N$ independently with probability $p$. The solution space is the intersection of these half spaces. In this talk\, we will talk about its sharp threshold phenomenon\, the frozen structure of the solution space\, and the Gardner formula.
URL:https://cmsa.fas.harvard.edu/event/12-10-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211203T093000
DTEND;TZID=America/New_York:20211203T103000
DTSTAMP:20260630T172053
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:20211119T093000
DTEND;TZID=America/New_York:20211119T103000
DTSTAMP:20260630T172053
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:20211112T093000
DTEND;TZID=America/New_York:20211112T103000
DTSTAMP:20260630T172053
CREATED:20240214T072852Z
LAST-MODIFIED:20240301T111040Z
UID:10002561-1636709400-1636713000@cmsa.fas.harvard.edu
SUMMARY:Universal relations between entanglement\, symmetries\, and entropy
DESCRIPTION:Member Seminar \nSpeaker: Gabriel Wong  \nTitle: Universal relations between entanglement\, symmetries\, and entropy \nAbstract: Entanglement is an essential property of quantum systems that distinguishes them from classical ones.   It is responsible for the nonlocal character of quantum information and provides a resource for quantum teleportation and quantum computation. In this talk I will provide an introduction to quantum entanglement and explain the essential role it plays in two seemingly unrelated subjects: implementation of measurement-based quantum computation and microstate counting of black holes in quantum gravity.   Time permitting\, I will also discuss attempts to characterize entanglement in string theory. A unifying theme that illuminates the entanglement structure of these diverse systems is the role of surface symmetries and (entanglement) edge modes. We will explain how these universal aspects of entanglement are captured in the framework of extended topological quantum field theory.
URL:https://cmsa.fas.harvard.edu/event/11-12-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211105T093000
DTEND;TZID=America/New_York:20211105T113000
DTSTAMP:20260630T172053
CREATED:20240214T073106Z
LAST-MODIFIED:20240301T111130Z
UID:10002562-1636104600-1636111800@cmsa.fas.harvard.edu
SUMMARY:The Greene-Plesser Construction Revisited
DESCRIPTION:Member Seminar  \nSpeaker: Chuck Doran \nTitle: The Greene-Plesser Construction Revisited \nAbstract: The first known construction of mirror pairs of Calabi-Yau manifolds was the Greene-Plesser “quotient and resolve” procedure which applies to pencils of hypersurfaces in projective space. We’ll review this approach\, uncover the hints it gives for some more general mirror constructions\, and describe a brand-new variant that applies to pencils of hypersurfaces in Grassmannians. This last is joint work with Tom Coates and Elana Kalashnikov (arXiv:2110.0727).
URL:https://cmsa.fas.harvard.edu/event/11-5-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211029T093000
DTEND;TZID=America/New_York:20211029T103000
DTSTAMP:20260630T172053
CREATED:20240214T073521Z
LAST-MODIFIED:20240301T111455Z
UID:10002563-1635499800-1635503400@cmsa.fas.harvard.edu
SUMMARY:The complex Monge-Ampere equation in K\”ahler geometry
DESCRIPTION:Speaker: Freid Tong \nTitle: The complex Monge-Ampere equation in Kahler geometry \nAbstract: The complex Monge-Ampere equations occupies an central role in K\”ahler geometry\, beginning with Yau’s famous solutions of the Calabi conjecture. Later developments has led to many interesting geometric applications and opening of new fields. In this talk\, I will introduce the complex Monge-Ampere equation and discuss the interplay between their analysis and geometry\, with a particular focus on the a priori C^0 estimates and their various applications. In the end\, I will also try to discuss some recent work with B. Guo and D.H. Phong on a new approach for proving sharp C^0 estimates for complex Monge-Ampere equations\, this new approach avoids the machinery of pluripotential theory that was previously necessary and has the advantage of generalizing to a large class of fully nonlinear equations.
URL:https://cmsa.fas.harvard.edu/event/10-29-2021-member-seminar/
CATEGORIES:Member Seminar
END:VEVENT
END:VCALENDAR