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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20251027T163000
DTEND;TZID=America/New_York:20251027T173000
DTSTAMP:20260518T232410
CREATED:20250911T192619Z
LAST-MODIFIED:20250911T193132Z
UID:10003793-1761582600-1761586200@cmsa.fas.harvard.edu
SUMMARY:Rigidity\, expansion and polytopes
DESCRIPTION:Colloquium \nSpeaker: Eran Nevo (Hebrew University of Jerusalem) \nTitle: Rigidity\, expansion and polytopes \nAbstract: Given a graph G and an embedding of its vertices in R^d\, what continuous motions of the vertices preserve all edge lengths? Clearly all motions induced by an isometry of R^d do\, these are the trivial motions; are there any others? If the answer is NO for all (equivalently\, for one) generic embedding\, G is called d-rigid. \nWhat are the d-rigid graphs? \nThis problem has been extensively studied since the 70s\, and is still widely open for d≥3. It is studied mainly from algebraic geometry and combinatorial points of view. Variants of it\, especially in dimensions 2 and 3\, are of importance also beyond mathematics\, e.g. in structural engineering\, computational biology and more. \nI will focus on a quantitative version of rigidity via spectral analysis of the related stiffness matrix\, including the construction of “rigidity expanders”\, generalizing expander graphs. Higher dimensional notions of rigidity and of stiffness matrices\, and their relation to the study of polytopes\, will be addressed too.
URL:https://cmsa.fas.harvard.edu/event/colloquium_102725/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-10.27.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20251006T163000
DTEND;TZID=America/New_York:20251006T173000
DTSTAMP:20260518T232410
CREATED:20250914T165359Z
LAST-MODIFIED:20250914T165941Z
UID:10003794-1759768200-1759771800@cmsa.fas.harvard.edu
SUMMARY:Geometry of dimer models
DESCRIPTION:Colloquium \nSpeaker: Alexei Borodin\, MIT \nTitle: Geometry of dimer models \nAbstract: Random dimer coverings of large planar graphs are known to exhibit unusual and visually apparent asymptotic phenomena that include formation of frozen regions and various phases in the unfrozen ones. For a specific family of subgraphs of the (periodically weighted) square lattice known as the Aztec diamonds\, the asymptotic behavior of dimers admits a precise description in terms of geometry of underlying Riemann surfaces. The goal of the talk is to explain how the surface structure manifests itself through the statistics of dimers. Based on joint works with T. Berggren and M. Duits. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium_10625/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-10.6.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250922T163000
DTEND;TZID=America/New_York:20250922T173000
DTSTAMP:20260518T232410
CREATED:20250826T191126Z
LAST-MODIFIED:20250914T170550Z
UID:10003732-1758558600-1758562200@cmsa.fas.harvard.edu
SUMMARY:Turbulent Mixing and Antagonistic Microorganisms
DESCRIPTION:Colloquium \nSpeaker: David Nelson\, Harvard \nTitle: Turbulent Mixing and Antagonistic Microorganisms \nAbstract: Unlike coffee and cream that homogenize when stirred\, growing micro-organisms (e.g.\, bacteria and baker’s yeast) can actively kill each other and avoid mixing.  How do such antagonistic interactions impact the growth and survival of competing strains\, while being spatially advected by turbulent flows?  By using analytic arguments and numerical simulations of a continuum model\, we describe the dynamics of two antagonistic strains that are dispersed by both compressible and incompressible turbulent flows in two spatial dimensions.  A key parameter is the ratio of the fluid transport time to that of biological reproduction\, which determines the winning organism that ultimately takes over the whole population from an initial heterogeneous state\, a process known as fixation.  By quantifying the probability and mean time for fixation\, we discuss how turbulence raises the threshold for biological nucleation and antagonism suppresses flow-induced mixing by depleting the population at interfaces. We highlight the unusual biological consequences of the interplay of turbulent fluid flows with antagonistic population dynamics\, with potential implications for marine microbial ecology and origins of biological chirality.
URL:https://cmsa.fas.harvard.edu/event/colloquium_92225/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-9.22.2025-scaled.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250915T163000
DTEND;TZID=America/New_York:20250915T173000
DTSTAMP:20260518T232410
CREATED:20250904T152315Z
LAST-MODIFIED:20250904T152759Z
UID:10003776-1757953800-1757957400@cmsa.fas.harvard.edu
SUMMARY:Topological Manifolds – The First 100 Years
DESCRIPTION:Colloquium \nSpeaker: Michael Freedman (Harvard CMSA and Logical Intelligence) \nTitle: Topological Manifolds – The First 100 Years \nAbstract: I’ll review manifold topology in the topological category from its start with work of Rado (1925) and Kneser (1926) to the present. Work of Moise\, Mazur\, Kirby\, Siebenmann\, Sullivan\, Kruskal\, and the speaker will be discussed. In my view there is one pressing open question (the A-B slice problem). I will end with some thoughts on putting an AI to work on it. \n  \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-91525/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-9.15.2025-scaled.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250512T163000
DTEND;TZID=America/New_York:20250512T173000
DTSTAMP:20260518T232410
CREATED:20250407T140851Z
LAST-MODIFIED:20250506T191033Z
UID:10003734-1747067400-1747071000@cmsa.fas.harvard.edu
SUMMARY:Factorizations for data analysis
DESCRIPTION:Colloquium \nSpeaker: Anna Seigal\, Harvard University \nTitle: Factorizations for data analysis \nAbstract: We can find structure in data by factoring it into building blocks\, which should be interpretable for the context at hand. A classical example is principal component analysis (PCA)\, which uses the eigendecomposition of the covariance matrix to find axes of variation in a dataset. Starting from PCA\, I will discuss matrix and tensor factorizations for data analysis\, and the linear and multilinear algebra that underpins their theoretical properties. We will see examples from causal inference\, independent component analysis\, and dimensionality reduction.
URL:https://cmsa.fas.harvard.edu/event/colloquium-51225/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-5.12.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250505T163000
DTEND;TZID=America/New_York:20250505T173000
DTSTAMP:20260518T232410
CREATED:20250407T140808Z
LAST-MODIFIED:20250501T134436Z
UID:10003733-1746462600-1746466200@cmsa.fas.harvard.edu
SUMMARY:Thinking Outside the Ballot Box
DESCRIPTION:Colloquium \nSpeaker: Ariel Procaccia\, Harvard University \nTitle: Thinking Outside the Ballot Box \nAbstract: How should one design unprecedented democratic processes capable of handling enormous sets of alternatives like all possible policies\, bills\, or statements? I argue that this challenge can be addressed through a framework called generative social choice\, which fuses the rigor of social choice theory with the flexibility and power of large language models. I then explore an application of generative social choice to the problem of identifying a proportionally representative slate of opinion statements. This includes a discussion of desired properties\, an algorithm that provably achieves them\, an implementation using GPT\, and insights from an end-to-end pilot. By providing guarantees\, generative social choice could alleviate concerns about AI-driven democratic innovation and help unlock its potential.
URL:https://cmsa.fas.harvard.edu/event/colloquium-5525/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-5.5.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250428T163000
DTEND;TZID=America/New_York:20250428T173000
DTSTAMP:20260518T232410
CREATED:20241209T171137Z
LAST-MODIFIED:20250423T174326Z
UID:10003637-1745857800-1745861400@cmsa.fas.harvard.edu
SUMMARY:Bass-Note Spectra of locally uniform geometries
DESCRIPTION:Colloquium \nSpeaker: Peter Sarnak\, IAS & Princeton University \nTitle: Bass-Note Spectra of locally uniform geometries \nAbstract: We formulate and report on the problem of the Bass-Note Spectrum of an invariant operator as one varies over locally uniform geometries. In the Euclidean setting this recasts classical problems of Mahler from the geometry of numbers in a new light. For certain operators homogeneous dynamics can be used decisively. In the non-Euclidean setting of hyperbolic manifolds we review some recent developments using the conformal bootstrap method and of random covers to study the Bass-Note spectra. We highlight the theme and impact of rigidity.
URL:https://cmsa.fas.harvard.edu/event/colloquium-42825/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-4.28.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250421T163000
DTEND;TZID=America/New_York:20250421T173000
DTSTAMP:20260518T232410
CREATED:20241209T163847Z
LAST-MODIFIED:20250418T142045Z
UID:10003636-1745253000-1745256600@cmsa.fas.harvard.edu
SUMMARY:Modeling the emergence of complex cortical structure from simple precursors in the brain: maps\, hierarchies\, and modules
DESCRIPTION:Colloquium \nSpeaker: Ila Fiete\, MIT \nTitle: Modeling the emergence of complex cortical structure from simple precursors in the brain: maps\, hierarchies\, and modules \nAbstract: Modular and hierarchical structures are ubiquitous in the brain. Two distinct hypotheses for such morphogenesis involve genetic specification (the positional information hypothesis) or spontaneous structure emergence from symmetry breaking (the pattern formation hypothesis). Indeed\, there is rich evidence supporting both hypotheses in different systems\, and more recently evidence that both systems might interact\, for instance with genetic specification providing an initial but relatively low-information scaffold of positional guidance and pattern formation constructing sharper structures by bootstrapping from this guidance. In this talk\, I will consider the emergence of two systems in the brain: the visual processing hierarchy with topographic structure\, and a modular cognitive circuit consisting of functionally independent grid cell networks that compute spatial location from velocity cues as animals move and navigate the world. I will describe how simple activity-driven growth and competition rules can lead to the emergence of topographically ordered sensory processing hierarchies\, and how genetically specified smooth gradients with purely local recurrent interactions on two scales can lead to global module emergence. In sum\, simple growth rules\, local interactions and smooth gradients can interact to produce rich emergent order on multiple scales in the form of maps\, modules\, and hierarchies\, with predictions that bridge scales from genes to connectivity to function.
URL:https://cmsa.fas.harvard.edu/event/colloquium-42125/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-4.21.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250414T163000
DTEND;TZID=America/New_York:20250414T173000
DTSTAMP:20260518T232410
CREATED:20241209T163821Z
LAST-MODIFIED:20250410T204704Z
UID:10003635-1744648200-1744651800@cmsa.fas.harvard.edu
SUMMARY:Quantum K-theory at roots of unity
DESCRIPTION:Colloquium \nSpeaker: Andrey Smirnov\, University of North Carolina at Chapel Hill \nTitle: Quantum K-theory at roots of unity \nAbstract: In this talk\, I will discuss a version of quantum K-theory introduced by A.Okounkov\, which can be defined through quasimap counts. In this framework\, the quantum K-theory ring is obtained as a specialization of the equivariant quasimap count at $q=1$\, where $q$ is the equivariant parameter associated with the torus action on the source of the quasimaps. A related\, but less explored\, structure emerges when $q$ is specialized at the roots of unity. I will outline the key ideas behind this construction and its implications. As an application\, I’ll also describe the spectrum of $p$-curvature for the quantum connection\, which offers a new proof of a recent result by P.Etingof and A.Varchenko. This talk is based on joint work with P. Koroteev.
URL:https://cmsa.fas.harvard.edu/event/colloquium-41425/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-4.14.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250407T163000
DTEND;TZID=America/New_York:20250407T173000
DTSTAMP:20260518T232410
CREATED:20241209T163727Z
LAST-MODIFIED:20250401T191454Z
UID:10003634-1744043400-1744047000@cmsa.fas.harvard.edu
SUMMARY:3-d Mirror Symmetry
DESCRIPTION:Colloquium \nSpeaker: Ben Webster\, University of Waterloo & Perimeter Institute \nTitle: 3-d Mirror Symmetry \nAbstract: I’ll give an introduction (or update\, for those who’ve been introduced) to 3d mirror symmetry from the perspective of a mathematician. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-4725/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-4.7.2025.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250324T163000
DTEND;TZID=America/New_York:20250324T173000
DTSTAMP:20260518T232410
CREATED:20241209T163216Z
LAST-MODIFIED:20250321T163829Z
UID:10003631-1742833800-1742837400@cmsa.fas.harvard.edu
SUMMARY:The Toda Lattice as a Soliton Gas
DESCRIPTION:Colloquium \nSpeaker: Amol Aggarwal\, Columbia University \nTitle: The Toda Lattice as a Soliton Gas \nAbstract: A basic tenet of integrable systems is that\, under sufficiently irregular initial data\, they can be thought of as dense collections of many solitons\, or “soliton gases.” In this talk we focus on the Toda lattice\, which is an archetypal example of an integrable Hamiltonian dynamical system. We explain how the system\, under certain random initial data\, can be interpreted through solitons\, and provide a framework for studying how these solitons asymptotically evolve in time. The arguments use ideas from random matrix theory\, particularly the analysis of Lyapunov exponents governing the decay rates of eigenvectors of random tridiagonal matrices.
URL:https://cmsa.fas.harvard.edu/event/colloquium-32425/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-3.24.2025.docx.final_.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250303T163000
DTEND;TZID=America/New_York:20250303T173000
DTSTAMP:20260518T232410
CREATED:20241209T163145Z
LAST-MODIFIED:20250218T153212Z
UID:10003630-1741019400-1741023000@cmsa.fas.harvard.edu
SUMMARY:Large value estimates in number theory and computer science
DESCRIPTION:Colloquium \nSpeaker: Larry Guth\, MIT \nTitle: Large value estimates in number theory and computer science \nAbstract: A large value estimate for a matrix M is a simple type of estimate in quantitative linear algebra. Estimates of this type appear in many parts of math\, both pure and applied. One example is the large value problem for Dirichlet polynomials from analytic number theory\, which is related to estimates about the zeroes of the Riemann zeta function. We will also give some examples from computer science. Many large value problems are difficult. On the pure math side\, the sharp conjecture about large values of Dirichlet polynomials has been open for a long time and is out of reach of current methods. On the computer science side\, we don’t know any efficient algorithm to approximately solve the large value problem for a given matrix M. Many experts think that such an algorithm does not exist. In this talk we will survey how large value estimates come up\, the known methods for working on them\, and some of the obstacles to fully understanding them. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-3325/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-3.3.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250210T163000
DTEND;TZID=America/New_York:20250210T173000
DTSTAMP:20260518T232410
CREATED:20240903T195201Z
LAST-MODIFIED:20250130T165640Z
UID:10003438-1739205000-1739208600@cmsa.fas.harvard.edu
SUMMARY:AI in math and theoretical physics: Status and prospects
DESCRIPTION:Colloquium \nSpeaker: Michael Douglas\, Harvard CMSA \nTitle: AI in math and theoretical physics: status and prospects \nAbstract: AI is making great progress and has the potential to change how we work in unprecedented ways. In this talk I will survey a few recent works which illustrate the state of the art\, some from my own research\, some developed at the CMSA’s recent program on Mathematics and Machine Learning. I will then report on current developments in AI and speculate on how they will affect our work in the next few years. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-21025/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-2.10.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250203T163000
DTEND;TZID=America/New_York:20250203T173000
DTSTAMP:20260518T232410
CREATED:20240903T194951Z
LAST-MODIFIED:20250130T165403Z
UID:10003434-1738600200-1738603800@cmsa.fas.harvard.edu
SUMMARY:Rational approximation and the AAA algorithm
DESCRIPTION:Colloquium \nSpeaker: Nick Trefethen\, Harvard University \nTitle: Rational approximation and the AAA algorithm \nApproximation by rational functions used to be mainly a theoretical subject\, but with the introduction of the AAA algorithm in 2018\, it became computationally practical and indeed easy. The implications for what we can do numerically are enormous. This talk will outline the algorithm and demonstrate its application to a collection of problems. We can also use it to demonstrate the potential theory that underlies the theory of rational approximation\, a topic that goes back to Joseph Walsh here at Harvard a century ago.
URL:https://cmsa.fas.harvard.edu/event/colloquium-2325/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-2.3.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241202T163000
DTEND;TZID=America/New_York:20241202T173000
DTSTAMP:20260518T232410
CREATED:20240903T195308Z
LAST-MODIFIED:20241126T142827Z
UID:10003440-1733157000-1733160600@cmsa.fas.harvard.edu
SUMMARY:Computability on $\mathbb R$ and other continuum-size structures
DESCRIPTION:Colloquium \nSpeaker: Russell Miller\, CUNY \nTitle: Computability on $\mathbb R$ and other continuum-size structures \nAbstract: We begin by recalling the notion of a computable function on the real numbers $\mathbb R$\, developed independently by Gregorczyk and Lacombe over sixty years ago. Using this notion\, we note that the real numbers that are themselves computable form a countable subfield of $\mathbb R$ with exactly the same first-order properties as $\mathbb R$ itself. (Logicians would therefore call it an \emph{elementary subfield}.) So\, in a first-order sense\, everything that happens in $\mathbb R$ is already exemplified in this much nicer subfield. However\, even when one knows that an existential statement holds for all parameters\, it may be impossible (both in $\mathbb R$ and in the subfield) to give a computable procedure for producing witnesses. Similar results hold in $\mathbb C$. \nWe will then turn to a different continuum-sized structure: the absolute Galois group $\operatorname{Gal}(\mathbb Q)$ of the rational numbers. Once again the computable elements of this group form a subgroup\, but now it is an open problem whether the group and the subgroup have the same first-order theory\, let alone whether this is an elementary subgroup. (If they do have the same theory\, this would put nice upper bounds on the complexity of the theory of $\operatorname{Gal}(\mathbb Q)$.) However\, using joint work with Kundu\, we can show that once again there is no computable procedure for producing witnesses to the truth of (true) existential statements\, either in the full group or in the subgroup.
URL:https://cmsa.fas.harvard.edu/event/colloquium-12224/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-12.2.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241125T163000
DTEND;TZID=America/New_York:20241125T173000
DTSTAMP:20260518T232410
CREATED:20240903T195237Z
LAST-MODIFIED:20241119T192853Z
UID:10003439-1732552200-1732555800@cmsa.fas.harvard.edu
SUMMARY:Mathematical Structures of Scattering Amplitudes
DESCRIPTION:Colloquium \nSpeaker: Anastasia Volovich\, Brown University \nTitle: Mathematical Structures of Scattering Amplitudes \nAbstract: Planar N=4 Yang-Mills scattering amplitudes have been computed to very high loop order. They have many remarkable properties that have sparked interest from mathematicians working on combinatorics\, algebraic geometry\, and number theory. At the same time\, several methods that have been developed for N=4 Yang-Mills can often be applied to more general quantum field theories\, including QCD. I will overview some of these exciting developments.
URL:https://cmsa.fas.harvard.edu/event/colloquium-112524/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.25.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241104T163000
DTEND;TZID=America/New_York:20241104T173000
DTSTAMP:20260518T232410
CREATED:20240903T195045Z
LAST-MODIFIED:20241016T202352Z
UID:10003436-1730737800-1730741400@cmsa.fas.harvard.edu
SUMMARY:The mathematics of evolution
DESCRIPTION:Colloquium \nSpeaker: Martin Nowak (Harvard) \nTitle: The mathematics of evolution \nAbstract: All living systems are guided by evolutionary dynamics. Evolution is a search process which occurs in populations of reproducing individuals. The three fundamental forces of evolution are mutation\, selection and cooperation. I will present basic ideas in the mathematical description of evolutionary dynamics\, including quasi-species theory\, evolutionary game theory\, and evolutionary graph theory. I will discuss specific problems such as origin of life\, emergence of complexity\, mechanisms of cooperation\, evolution of cancer and how to overcome resistance to targeted therapy. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-11424/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.4.2024.docx.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241021T163000
DTEND;TZID=America/New_York:20241021T173000
DTSTAMP:20260518T232410
CREATED:20240903T195022Z
LAST-MODIFIED:20241016T144838Z
UID:10003435-1729528200-1729531800@cmsa.fas.harvard.edu
SUMMARY:Higher Vapnik–Chervonenkis theory
DESCRIPTION:Colloquium \nSpeaker: Artem Chernikov\, University of Maryland \nTitle: Higher Vapnik–Chervonenkis theory \nAbstract: Finite VC-dimension\, a combinatorial property of families of sets\, was discovered simultaneously by Vapnik and Chervonenkis in probabilistic learning theory\, and by Shelah in model theory (where it is called NIP). It plays an important role in several areas including machine learning\, combinatorics\, mathematical logic\, functional analysis and topological dynamics. We develop aspects of higher-order VC-theory\, in particular establishing a generalization of the epsilon-net theorem for families of sets (and functions) on n-fold product spaces with bounded VC_n-dimension (i.e. there is a bound on the sizes of n-dimensional boxes that can be shattered). We obtain some applications in combinatorics and in model theory\, including a strong version of Szemerdi’s regularity lemma for hypergraphs omitting a fixed finite n-partite n-hypergraph. Joint work with Henry Towsner.
URL:https://cmsa.fas.harvard.edu/event/colloquium-102124/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-10.21.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241007T163000
DTEND;TZID=America/New_York:20241007T173000
DTSTAMP:20260518T232410
CREATED:20240903T194924Z
LAST-MODIFIED:20241003T160128Z
UID:10003433-1728318600-1728322200@cmsa.fas.harvard.edu
SUMMARY:Local complexity measures in modern parameterized function classes for supervised learning
DESCRIPTION:Colloquium \nSpeaker: Elisenda Grigsby\, Boston College \nTitle: Local complexity measures in modern parameterized function classes for supervised learning \nAbstract: The parameter space for any fixed architecture of neural networks serves as a proxy during training for the associated class of functions – but how faithful is this representation? For any fixed feedforward ReLU network architecture\, it is well-known that many different parameter settings can determine the same function. It is less well-known that the degree of this redundancy is inhomogeneous across parameter space. I’ll discuss two locally-applicable complexity measures for ReLU network classes and what we know about the relationship between them: (1) the local functional dimension\, and (2) a local version of VC dimension called persistent pseudodimension. The former is easy to compute on finite batches of points\, the latter should give local bounds on the generalization gap. I’ll speculate about how this circle of ideas might help guide our understanding of the double descent phenomenon. All of the work described in this talk is joint with Kathryn Lindsey. Some portions are also joint with Rob Meyerhoff\, David Rolnick\, and Chenxi Wu.
URL:https://cmsa.fas.harvard.edu/event/colloquium-10724/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=application/pdf:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-10.7.2024.docx.pdf
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240923T163000
DTEND;TZID=America/New_York:20240923T173000
DTSTAMP:20260518T232410
CREATED:20240903T194207Z
LAST-MODIFIED:20240918T190927Z
UID:10003431-1727109000-1727112600@cmsa.fas.harvard.edu
SUMMARY:Symmetry groups in infinite dimensions
DESCRIPTION:Colloquium \nSpeaker: Lisa Carbone\, Rutgers University \nTitle: Symmetry groups in infinite dimensions \nAbstract: The study of many physical theories requires an understanding of symmetries of infinite dimensional Lie algebras. The construction of groups of automorphisms for infinite dimensional Lie algebras is challenging\, but there is well established theory for the class of Kac-Moody algebras. A generalization of Kac-Moody algebras known as Borcherds algebras arise in string theory models\, but the methods for constructing Kac-Moody groups break down for this more general class. We discuss the challenges that arise and describe several approaches to constructing groups for Borcherds algebras. Our main example is the Monster Lie algebra which plays an important role in the solution of Monstrous Moonshine and which is a symmetry algebra of a model of the compactified Heterotic String.
URL:https://cmsa.fas.harvard.edu/event/colloquium-92324/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-09.23.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240916T163000
DTEND;TZID=America/New_York:20240916T173000
DTSTAMP:20260518T232410
CREATED:20240903T193540Z
LAST-MODIFIED:20240916T163127Z
UID:10003430-1726504200-1726507800@cmsa.fas.harvard.edu
SUMMARY:Periodic pencils of flat connections and their p-curvature
DESCRIPTION:Colloquium \nSpeaker: Pavel Etingof (MIT) \nTitle: Periodic pencils of flat connections and their p-curvature \n A periodic pencil of flat connections on a smooth algebraic variety  is a linear family of flat connections  \, where  are local coordinates on  and  are matrix-valued regular functions. A pencil is periodic if it is generically invariant under the shifts  up to isomorphism. I will explain that periodic pencils have many remarkable properties\, and there are many interesting examples of them\, e.g. Knizhnik-Zamolodchikov\, Dunkl\, Casimir connections and equivariant quantum connections for conical symplectic resolutions with finitely many torus fixed points. I will also explain that in characteristic \, the -curvature operators  of a periodic pencil  are isospectral to the commuting endomorphisms \, where  is the Frobenius twist of . This allows us to compute the eigenvalues of the -curvature for the above examples\, and also to show that a periodic pencil of connections always has regular singularites. This is joint work with Alexander Varchenko. \n(Abstract link (pdf)
URL:https://cmsa.fas.harvard.edu/event/colloquium_91624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-09.16.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240909T163000
DTEND;TZID=America/New_York:20240909T173000
DTSTAMP:20260518T232410
CREATED:20240827T200454Z
LAST-MODIFIED:20240903T152309Z
UID:10003406-1725899400-1725903000@cmsa.fas.harvard.edu
SUMMARY:Combinatorics and geometry of the amplituhedron
DESCRIPTION:Colloquium \nSpeaker: Lauren Williams\, Harvard University \nTitle: Combinatorics and geometry of the amplituhedron \nAbstract: The amplituhedron is a geometric object introduced by Arkani-Hamed and Trnka to compute scattering amplitudes in N=4 super Yang Mills theory. It generalizes interesting objects such as cyclic polytopes and the positive Grassmannian. It has connections to tropical geometry\, cluster algebras\, and combinatorics (plane partitions\, Catalan numbers). I’ll give a gentle introduction to the amplituhedron\, then survey some recent progress on some of the main conjectures about the amplituhedron: the Magic Number Conjecture\, the BCFW tiling conjecture\, and the Cluster Adjacency conjecture.  Based on joint works withEvan-Zohar\, Lakrec\, Parisi\, Sherman-Bennett\, and Tessler.
URL:https://cmsa.fas.harvard.edu/event/colloquium_9924/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-09.09.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240513T163000
DTEND;TZID=America/New_York:20240513T173000
DTSTAMP:20260518T232410
CREATED:20240130T151206Z
LAST-MODIFIED:20240508T203329Z
UID:10000814-1715617800-1715621400@cmsa.fas.harvard.edu
SUMMARY:Errors and Correction in Cumulative Knowledge
DESCRIPTION:Colloquium \nSpeaker: Madhu Sudan\, Harvard University \nTitle: Errors and Correction in Cumulative Knowledge \nAbstract: Societal accumulation of knowledge is a complex\, and arguably error-prone\, process. The correctness of new units of knowledge depends not only on the correctness of the new reasoning\, but also on the correctness of old units that the new one builds on. If left unchecked\, errors could completely ruin the validity of most of this knowledge so there must some error-correcting going on. What are the error-corrections processes employed in nature and how effective are they? In this talk\, we describe our attempts to model such phenomena using probablistic models – we describe models for growth of cumulative knowledge\, emergence of errors and methods to check for errors and eliminate them. We then analyze in this compound model\, when effects of errors may survive\, and when they are totally eliminated. \nThe central discovery in our work is the following optimistic statement: If we do checking correctly (most of the time) investing just a constant factor (<1) of our effort in checking (and saving the remaining constant factor towards deriving new units of knowledge)\, then effects of errors can be kept in check. Notably the amount of effort expended on checking does not scale with the volume of total knowledge or the depth of dependencies in the new units of knowledge\, either of which would be overwhelming. \nBased on the papers: \nIs this correct? Let’s check!\nOmri Ben-Eliezer\, Dan Mikulincer\, Elchanan Mossel\, Madhu Sudan\narXiv:2211.12301 \nErrors are Robustly Tamed in Cumulative Knowledge Processes\nAnna Brandenberger\, Cassandra Marcussen\, Elchanan Mossel\, Madhu Sudan\narXiv:2309.05638
URL:https://cmsa.fas.harvard.edu/event/colloquium-4124/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-05.13.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240506T163000
DTEND;TZID=America/New_York:20240506T173000
DTSTAMP:20260518T232410
CREATED:20240319T201629Z
LAST-MODIFIED:20240507T201738Z
UID:10000819-1715013000-1715016600@cmsa.fas.harvard.edu
SUMMARY:Liouville Theory and Weil-Petersson Geometry
DESCRIPTION:Colloquium \nSpeaker: Sarah Harrison (Northeastern University) \nTitle: Liouville Theory and Weil-Petersson Geometry \nAbstract: Two-dimensional conformal field theory is a powerful tool to understand the geometry of surfaces. Liouville conformal field theory in the classical (large central charge) limit encodes the geometry of the moduli space of Riemann surfaces. I describe an efficient algorithm to compute the Weil–Petersson metric to arbitrary accuracy using Zamolodchikov’s recursion relation for conformal blocks\, focusing on examples of a sphere with four punctures and generalizations to other one-complex-dimensional moduli spaces. Comparison with analytic results for volumes and geodesic lengths finds excellent agreement. In the case of M_{0\,4}\, I discuss numerical results for eigenvalues of the Weil-Petersson Laplacian and connections with random matrix theory. \nBased on work with K. Coleville\, A. Maloney\, K. Namjou\, and T. Numasawa.
URL:https://cmsa.fas.harvard.edu/event/colloquium-5624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-05.06.2024.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240429T163000
DTEND;TZID=America/New_York:20240429T173000
DTSTAMP:20260518T232410
CREATED:20240207T190153Z
LAST-MODIFIED:20240424T142108Z
UID:10000818-1714408200-1714411800@cmsa.fas.harvard.edu
SUMMARY:The DNA of Particle Scattering
DESCRIPTION:Colloquium \nSpeaker: Lance Dixon (SLAC\, Stanford University) \nTitle: The DNA of Particle Scattering \nAbstract: At the Large Hadron Collider\, the copious scattering of quarks and gluons in quantum chromodynamics (QCD) produces Higgs bosons and many backgrounds to searches for new physics.  At short distances\, scattering in QCD can be evaluated in perturbation theory and leads to highly intricate\, multivariate mathematical functions such as generalized polylogarithms.  To gain further insight\, one can study a cousin of QCD called planar N=4 super-Yang-Mills theory.  Some processes in this theory can be computed to eighth order in perturbation theory\, versus second or third order in QCD.  The computation and analysis of these results rely on a Hopf algebra coaction on polylogarithms.  Its maximal iteration is called the ‘symbol’\, which serves as a ‘genetic code’ for amplitudes.  The symbol is a linear combination of words\, sequences of letters analogous to sequences of DNA base pairs.  Understanding the alphabet\, and then reading the code\, exposes the physics and mathematics of quantum scattering\, including bizarre new symmetries.  For example\, the two scattering amplitudes that are known to the highest orders in perturbation theory (8 loops) are related to each other by an ‘antipodal duality’\, which involves reading the code backwards as well as forwards. A third scattering amplitude\, which contains the other two as limits\, has an antipodal self-duality which ‘explains’ the other duality.  However\, we still don’t know ‘who ordered’ this property\, or what it really means. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-42924/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-04.29.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240318T163000
DTEND;TZID=America/New_York:20240318T173000
DTSTAMP:20260518T232410
CREATED:20240130T151005Z
LAST-MODIFIED:20240308T200603Z
UID:10000812-1710779400-1710783000@cmsa.fas.harvard.edu
SUMMARY:Koszul duality & twisted holography for asymptotically flat spacetimes
DESCRIPTION:Colloquium \nSpeaker: Natalie Paquette\, University of Washington \nTitle: Koszul duality & twisted holography for asymptotically flat spacetimes \nAbstract: Koszul duality has been understood in recent years to characterize order-type defects in twists of supersymmetric field theories. This notion has been generalized\, from a physical point of view\, by studying couplings between D-branes and closed string theories in the topological string. Computing the D-brane backreaction\, and studying the resulting open/closed string duality\, is the purview of the twisted holography program. Twisted holography seeks to study supersymmetric sectors of the AdS/CFT correspondence using these methods\, and leverage the appropriate generalization of Koszul duality to elucidate the bulk/boundary map. When applying these methods to a topological string configuration on twistor space\, one can construct an instance of twisted holography in which a 2d chiral algebra\, supported on the “celestial sphere”\, is dual to a 4d theory in an asymptotically flat spacetime. This is the first such top-down example of holography in a 4d asymptotically flat spacetime. This talk describes joint work done\, variously\, with Kevin Costello\, Brian Williams\, and Atul Sharma.
URL:https://cmsa.fas.harvard.edu/event/colloquium-31824/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-03.18.2024.docx-2_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240304T163000
DTEND;TZID=America/New_York:20240304T173000
DTSTAMP:20260518T232410
CREATED:20240130T150912Z
LAST-MODIFIED:20240228T213450Z
UID:10000810-1709569800-1709573400@cmsa.fas.harvard.edu
SUMMARY:Strong bounds for arithmetic progressions
DESCRIPTION:Colloquium \nSpeaker: Raghu Meka (UCLA) \nTitle: Strong bounds for arithmetic progressions \nAbstract: Suppose you have a set S of integers from {1\,2\,…\,N} that contains at least N / C elements. Then for large enough N\, must S contain three equally spaced numbers (i.e.\, a 3-term arithmetic progression)? \nIn 1953\, Roth showed this is the case when C is roughly (log log N). Behrend in 1946 showed that C can be at most exp(sqrt(log N)). Since then\, the problem has been a cornerstone of the area of additive combinatorics. Following a series of remarkable results\, a celebrated paper from 2020 due to Bloom and Sisask improved the lower bound on C to C = (log N)^(1+c) for some constant c > 0. \nThis talk will describe a new work showing that C can be much closer to Behrend’s construction. Based on joint work with Zander Kelley.
URL:https://cmsa.fas.harvard.edu/event/colloquium-3424/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-03.04.2024-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240226T163000
DTEND;TZID=America/New_York:20240226T173000
DTSTAMP:20260518T232410
CREATED:20240130T150524Z
LAST-MODIFIED:20240220T171315Z
UID:10000809-1708965000-1708968600@cmsa.fas.harvard.edu
SUMMARY:Factorization algebras in quite a lot of generality
DESCRIPTION:Colloquium \nSpeaker: Clark Barwick\, University of Edinburgh \nTitle: Factorization algebras in quite a lot of generality \nAbstract: The objects of arithmetic geometry are not manifolds. Some concepts from differential geometry admit analogues in arithmetic\, but they are not straightforward. How then can we hope to make precise sense of quantum field theories on these objects? I will propose the beginnings of a mathematical framework via a general theory of factorization algebras. A new feature is a subtle piece of additional structure on our objects – what I call a world-structure – that is ordinarily left implicit.
URL:https://cmsa.fas.harvard.edu/event/colloquium-22624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-02.26.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240212T163000
DTEND;TZID=America/New_York:20240212T173000
DTSTAMP:20260518T232410
CREATED:20240201T145702Z
LAST-MODIFIED:20240209T210827Z
UID:10000807-1707755400-1707759000@cmsa.fas.harvard.edu
SUMMARY:Machine Learning and Scientific Computing: There is plenty of room in the middle
DESCRIPTION:Colloquium \nSpeaker: Petros Koumoutsakos\, Harvard SEAS \nTitle: Machine Learning and Scientific Computing: There is plenty of room in the middle \nAbstract: Over the last thirty years we have experienced more than a billion-fold increase in hardware capabilities and a dizzying pace of acquiring and transmitting massive amounts of data. Scientific Computing and\, more lately\, Artificial Intelligence (AI) has been key beneficiaries of these advances. In this talk I would outline the need for bridging the decades long advances in Scientific Computing with those of AI. I will use examples from fluid mechanics to argue for forming alloys of AI and simulations for their prediction and control. I will present novel algorithms for learning the Effective Dynamics (LED) of complex systems and a fusion of multi- agent reinforcement learning and scientific computing (SciMARL) for modeling and control of turbulent flows. I will also show our recent work on Optimizing a Discrete Loss (ODIL) that outperforms popular techniques such as PINNs by several orders of magnitude. \nI will juxtapose successes and failures and argue that the proper fusion of scientific computing and AI expertise are essential to advance scientific frontiers. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-21224/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-02.12.2024_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231211T163000
DTEND;TZID=America/New_York:20231211T173000
DTSTAMP:20260518T232410
CREATED:20240223T074431Z
LAST-MODIFIED:20240223T074431Z
UID:10002828-1702312200-1702315800@cmsa.fas.harvard.edu
SUMMARY:Homology\, higher derived limits\, and set theory
DESCRIPTION:Colloquium \nSpeaker: Justin Moore (Cornell University) \nTitle: Homology\, higher derived limits\, and set theory \nAbstract: Singular homology has a number of well-known defects when used to study spaces such as the Hawaiian earring and solenoids. It may not reflect the “shape” of the space and can give counterintuitive information about its dimension. One remedy of this is to develop a homology theory based on approximating spaces by polyhedra\, computing their homologies\, and then taking a limit. This is the approach taken by Steenrod-Sitnikov homology and Lisica and Mardesic’s strong homology. Even within the class of locally compact second countable spaces though\, the properties of these homology theories — and the higher derived limits which underly them — are dependent on axioms of set theory beyond ZFC. Recently it was shown that it is consistent with (and therefore independent of) ZFC that strong homology and Steenrod Sitnikov homology coincide in the class of locally compact second countable spaces — and therefore each of these homology theories enjoys the desirable properties of the other. These results also point to how we might develop variants of these homology theories which enjoy their desirable properties\, but which are less sensitive to set theory. This is joint work with Nathaniel Bannister\, Jeff Bergfalk\, and Stevo Todorcevic.
URL:https://cmsa.fas.harvard.edu/event/colloquium-121123/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-12.11.2023.png
END:VEVENT
END:VCALENDAR