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DTSTART;TZID=America/New_York:20230906T160000
DTEND;TZID=America/New_York:20230906T170000
DTSTAMP:20260503T233053
CREATED:20240223T110729Z
LAST-MODIFIED:20240223T110729Z
UID:10002857-1694016000-1694019600@cmsa.fas.harvard.edu
SUMMARY:Light cones for open quantum systems
DESCRIPTION:Probability Seminar \nSpeaker: Marius Lemm\, University of Tuebingen \nTitle: Light cones for open quantum systems\n\nAbstract: We consider non-relativistic Markovian open quantum dynamics in continuous space. We show that\, up to small probability tails\, the supports of quantum states propagate with finite speed in any finite-energy subspace. More precisely\, if the initial quantum state is localized in space\, then any finite-energy part of the solution of the von Neumann-Lindblad equation is approximately localized inside an energy-dependent light cone. We also obtain an explicit upper bound on the slope of this light cone (i.e.\, on the maximal speed). The general method can be used to derive propagation bounds for a variety of other quantum systems including Lieb-Robinson bounds for lattice bosons. Based on joint works with S. Breteaux\, J. Faupin\, D.H. Ou Yang\, I.M. Sigal\, and J. Zhang.\n
URL:https://cmsa.fas.harvard.edu/event/probability-9623/
LOCATION:Science Center 232\, Harvard Science Center\, 1 Oxford Street\, Cambridge MA 02138
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Probability-Seminar-09.06.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230907T133000
DTEND;TZID=America/New_York:20230907T143000
DTSTAMP:20260503T233053
CREATED:20240223T110205Z
LAST-MODIFIED:20240223T110205Z
UID:10002855-1694093400-1694097000@cmsa.fas.harvard.edu
SUMMARY:Correlation decay for finite lattice gauge theories
DESCRIPTION:Probability Seminar \nSpeaker: Arka Adhikari (Stanford) \nTitle: Correlation decay for finite lattice gauge theories \nAbstract: In the setting of lattice gauge theories with finite (possibly non-Abelian) gauge groups at weak coupling\, we prove exponential decay of correlations for a wide class of gauge invariant functions\, which in particular includes arbitrary functions of Wilson loop observables. Based on joint work with Sky Cao. \n
URL:https://cmsa.fas.harvard.edu/event/probability-9723/
LOCATION:Science Center 232\, Harvard Science Center\, 1 Oxford Street\, Cambridge MA 02138
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Probability-Seminar-09.07.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230908T100000
DTEND;TZID=America/New_York:20230908T113000
DTSTAMP:20260503T233053
CREATED:20230904T055802Z
LAST-MODIFIED:20240116T070515Z
UID:10001125-1694167200-1694172600@cmsa.fas.harvard.edu
SUMMARY:A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Xiao-Gang Wen (MIT) \nTitle: A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry \nAbstract: Emergent symmetry can be generalized symmetry beyond (higher) group description and/or can be anomalous. I will describe a unified theory for generalized symmetry based on symmetry/topological-order correspondence. I will also discuss some applications of emergent generalized symmetry.
URL:https://cmsa.fas.harvard.edu/event/qm_9823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.08.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230912T110000
DTEND;TZID=America/New_York:20230912T120000
DTSTAMP:20260503T233053
CREATED:20240223T102522Z
LAST-MODIFIED:20240223T102522Z
UID:10002847-1694516400-1694520000@cmsa.fas.harvard.edu
SUMMARY:Pole skipping\, quasinormal modes\, shockwaves and their connection to chaos
DESCRIPTION:General Relativity Seminar \nSpeaker: Diandian Wang(Harvard University) \nTitle: Pole skipping\, quasinormal modes\, shockwaves and their connection to chaos \nAbstract: A chaotic quantum system can be studied using the out-of-time-order correlator (OTOC). I will tell you about pole skipping — a recently discovered feature of the retarded Green’s function — that seems to also know things: things like the Lyapunov exponent and the butterfly velocity\, which are important quantifiers of the OTOC. Then I will talk about a systematic way of deriving pole-skipping conditions for general holographic CFTs dual to classical bulk theories and how to use this framework to derive a few interesting statements including: (1) theories with higher spins generally violate the chaos bound; (2) the butterfly velocity calculated using pole skipping agrees with that calculated using shockwaves for arbitrary higher-derivative gravity coupled to ordinary matter; (3) shockwaves are related to a special type of quasinormal modes. As we will see\, the techniques are entirely classically gravitational\, which I will go through with a certain level of details.
URL:https://cmsa.fas.harvard.edu/event/gr_91223/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.12.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230912T160000
DTEND;TZID=America/New_York:20230912T170000
DTSTAMP:20260503T233053
CREATED:20240223T104300Z
LAST-MODIFIED:20240223T104300Z
UID:10002849-1694534400-1694538000@cmsa.fas.harvard.edu
SUMMARY:Homotopy classes of loops of Clifford unitaries
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Roman Geiko\, UCLA \nTitle: Homotopy classes of loops of Clifford unitaries \nAbstract: We study Clifford locality-preserving unitaries and stabilizer Hamiltonians by means of Hermitian K-theory. We demonstrate how the notion of algebraic homotopy of modules over Laurent polynomial rings translates into the connectedness of two short-range entangled stabilizer Hamiltonians by a shallow Clifford circuit. We apply this observation to a classification of homotopy classes of loops of Clifford unitaries. The talk is based on a work in collaboration with Yichen Hu. https://arxiv.org/abs/2306.09903.
URL:https://cmsa.fas.harvard.edu/event/tqms_91223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-09.12.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230913T103000
DTEND;TZID=America/New_York:20230913T113000
DTSTAMP:20260503T233053
CREATED:20230904T061048Z
LAST-MODIFIED:20240223T113738Z
UID:10001122-1694601000-1694604600@cmsa.fas.harvard.edu
SUMMARY:Phase transitions out of quantum Hall states in moire TMD bilayers
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Xueyang Song (MIT) \nTitle: Phase transitions out of quantum Hall states in moire TMD bilayers \nAbstract: Motivated by the recent experimental breakthroughs in observing Fractional Quantum Anomalous Hall (FQAH) states in moir\’e Transition Metal Dichalcogenide (TMD) bilayers\, we propose and study various unconventional phase transitions between quantum Hall phases and Fermi liquids or charge ordered phases upon tuning the bandwidth. At filling -2/3\, we describe a direct transition between the FQAH state and a Charge Density Wave (CDW) insulator. The critical theory resembles that of the familiar deconfined quantum critical point (DQCP) but with an additional Chern-Simons term. At filling -1/2\, we study the possibility of a continuous transition between the composite Fermi liquid (CFL) and the Fermi liquid (FL) building on and refining previous work by Barkeshli and McGreevy. Crucially we show that translation symmetry alone is enough to enable a second order CFL-FL transition. We argue that there must be critical CDW fluctuations though neither phase has long range CDW order. A striking signature is a universal jump of resistivities at the critical point. With disorder\, we argue that the CDW order gets pinned and the CFL-FL evolution happens through an intermediate electrically insulating phase with mobile neutral fermions. A clean analog of this insulating phase with long range CDW order and a neutral fermi surface can potentially also exist. We also present a critical theory for the CFL to FL transition at filling -3/4. Our work opens up a new avenue to realize deconfined criticality and fractionalized phases beyond familiar Landau level physics in the moire Chern band system.
URL:https://cmsa.fas.harvard.edu/event/tqms_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-09.12.23.docx-2.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230913T163000
DTEND;TZID=America/New_York:20230913T180000
DTSTAMP:20260503T233053
CREATED:20240223T111403Z
LAST-MODIFIED:20240223T111403Z
UID:10002859-1694622600-1694628000@cmsa.fas.harvard.edu
SUMMARY:Anomalies of Non-Invertible Symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Clay Córdova (U Chicago) \nTitle: Anomalies of Non-Invertible Symmetries
URL:https://cmsa.fas.harvard.edu/event/qm_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230914T130000
DTEND;TZID=America/New_York:20230914T140000
DTSTAMP:20260503T233053
CREATED:20240223T111752Z
LAST-MODIFIED:20240223T111752Z
UID:10002860-1694696400-1694700000@cmsa.fas.harvard.edu
SUMMARY:Frustration-free states of cell fate networks: the case of the epithelial-mesenchymal transition
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Herbert Levine (Northeastern)\n\nTitle: Frustration-free states of cell fate networks: the case of the epithelial-mesenchymal transition\n\nAbstract: Cell fate decisions are made by allowing external signals to govern the steady-state pattern adopted by networks of interacting regulatory factors governing transcription and translation. One of these decisions\, of importance for both developmental processes and for cancer metastasis\, is the epithelial-mesenchymal transition (EMT). In this talk\, we will argue that these biological networks have highly non-generic interaction structures such that they allow for phenotypic states with very low frustration\, i.e. where most interactions are satisfied. This property has important consequences for the allowed dynamics of these systems.
URL:https://cmsa.fas.harvard.edu/event/am-91423/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230915T120000
DTEND;TZID=America/New_York:20230915T130000
DTSTAMP:20260503T233053
CREATED:20240223T112851Z
LAST-MODIFIED:20240223T112851Z
UID:10002864-1694779200-1694782800@cmsa.fas.harvard.edu
SUMMARY:Quantum UV-IR map and curve counts in skeins
DESCRIPTION:Member Seminar \nSpeaker: Sunghyuk Park \nTitle: Quantum UV-IR map and curve counts in skeins \nAbstract: Quantum UV-IR map (a.k.a. q-nonabelianization map)\, introduced by Neitzke and Yan\, is a map from UV line defects in a 4d N=2 theory of class S to those of the IR. Mathematically\, it can be described as a map between skein modules and is a close cousin of quantum trace map of Bonahon and Wong. \nIn this talk\, I will discuss how quantum UV-IR map can be generalized to a map between HOMFLYPT skein modules\, using skein-valued curve counts of Ekholm and Shende.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-91523/
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:20230919T110000
DTEND;TZID=America/New_York:20230919T120000
DTSTAMP:20260503T233053
CREATED:20240223T101246Z
LAST-MODIFIED:20240223T101246Z
UID:10002846-1695121200-1695124800@cmsa.fas.harvard.edu
SUMMARY:Quantization of causal diamonds in 2+1 dimensional gravity
DESCRIPTION:General Relativity Seminar \nSpeaker: Rodrigo Silva\, University of Maryland \nTitle: Quantization of causal diamonds in 2+1 dimensional gravity \nAbstract: We develop the reduced phase space quantization of causal diamonds in $2+1$ dimensional gravity with a nonpositive cosmological constant. The system is defined as the domain of dependence of a spacelike topological disk with a fixed boundary metric. By solving the constraints in a constant-mean-curvature time gauge and removing all the spatial gauge redundancy\, we find that the phase space is the cotangent bundle of $Diff^+(S^1)/PSL(2\, \mathbb{R})$\, i.e.\, the group of orientation-preserving diffeomorphisms of the circle modulo the projective special linear subgroup. Classically\, the states correspond to causal diamonds embedded in $AdS_3$ (or $Mink_3$ if $\Lambda = 0$)\, with a fixed corner length\, that has the topological disk as a Cauchy surface. Because this phase space does not admit a global system of coordinates\, a generalization of the standard canonical (coordinate) quantization is required — in particular\, since the configuration space is a homogeneous space for a Lie group\, we apply Isham’s group-theoretic quantization scheme. The Hilbert space of the associated quantum theory carries an irreducible unitary representation of the $BMS_3$ group and can be realized by wavefunctions on a coadjoint orbit of Virasoro with labels in irreducible unitary representations of the corresponding little group. A surprising result is that the twist of the diamond boundary loop is quantized in terms of the ratio of the Planck length to the corner length. \n
URL:https://cmsa.fas.harvard.edu/event/gr_91923/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.19.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230919T123000
DTEND;TZID=America/New_York:20230919T133000
DTSTAMP:20260503T233053
CREATED:20240223T080443Z
LAST-MODIFIED:20240223T080443Z
UID:10002832-1695126600-1695130200@cmsa.fas.harvard.edu
SUMMARY:CMSA Q and A Seminar 9/19/2023
DESCRIPTION:Speakers: Dan Freed (Harvard Math and CMSA)\, Denis Auroux (Harvard Math)
URL:https://cmsa.fas.harvard.edu/event/cmsaqa_91923/
LOCATION:Common Room\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:CMSA Q&A Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230920T103000
DTEND;TZID=America/New_York:20230920T113000
DTSTAMP:20260503T233054
CREATED:20240223T104903Z
LAST-MODIFIED:20240223T104903Z
UID:10002851-1695205800-1695209400@cmsa.fas.harvard.edu
SUMMARY:Exact Results in Flat Band Hubbard Models
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Jonah Herzog-Arbeitman\, Princeton University \nTitle: Exact Results in Flat Band Hubbard Models \nAbstract: Flat bands\, like those in the kagome lattice or twisted bilayer graphene\, are a natural setting for studying strongly coupled physics since the interaction strength is the only energy scale in the problem. They can exhibit unconventional behavior in the multi-orbital case: the mean-field theory of flat band attractive Hubbard models shows the possibility of superconductivity even though the Fermi velocity of the bands is strictly zero. However\, it is not necessary to resort to this approximation. We demonstrate that the groundstates and low-energy excitations of a large class of attractive Hubbard models are exactly solvable\, offering a rare\, microscopic view of their physics. The solution reveals the importance of quantum geometry in escaping (some of) BCS phenomenology within a tractable and nontrivial strong coupling theory.
URL:https://cmsa.fas.harvard.edu/event/tqms_92023/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-09.20.23.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230920T140000
DTEND;TZID=America/New_York:20230920T150000
DTSTAMP:20260503T233054
CREATED:20240227T083355Z
LAST-MODIFIED:20240227T083355Z
UID:10002873-1695218400-1695222000@cmsa.fas.harvard.edu
SUMMARY:The TinyStories Dataset: How Small Can Language Models Be And Still Speak Coherent
DESCRIPTION:New Technologies in Mathematics Seminar \nSpeaker: Ronen Eldan\, Microsoft Research \nTitle: The TinyStories Dataset: How Small Can Language Models Be And Still Speak Coherent \nAbstract: While generative language models exhibit powerful capabilities at large scale\, when either the model or the number of training steps is too small\, they struggle to produce coherent and fluent text: Existing models whose size is below a few billion parameters often do not generate coherent text beyond a few sentences. Hypothesizing that one of the main reasons for the strong reliance on size is the vast breadth and abundance of patterns in the datasets used to train those models\, this motivates the following question: Can we design a dataset that preserves the essential elements of natural language\, such as grammar\, vocabulary\, facts\, and reasoning\, but that is much smaller and more refined in terms of its breadth and diversity? \nIn this talk\, we introduce TinyStories\, a synthetic dataset of short stories that only contain words that 3 to 4-year-olds typically understand\, generated by GPT-3.5/4. We show that TinyStories can be used to train and analyze language models that are much smaller than the state-of-the-art models (below 10 million parameters)\, or have much simpler architectures (with only one transformer block)\, yet still produce fluent and consistent stories with several paragraphs that are diverse and have almost perfect grammar\, and demonstrate certain reasoning capabilities. We also show that the trained models are substantially more interpretable than larger ones\, as we can visualize and analyze the attention and activation patterns of the models\, and show how they relate to the generation process and the story content. We hope that TinyStories can facilitate the development\, analysis and research of language models\, especially for low-resource or specialized domains\, and shed light on the emergence of language capabilities in LMs. \n
URL:https://cmsa.fas.harvard.edu/event/nt-92023/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-NTM-Seminar-09.20.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230922T100000
DTEND;TZID=America/New_York:20230922T113000
DTSTAMP:20260503T233054
CREATED:20240223T095601Z
LAST-MODIFIED:20240223T095601Z
UID:10002845-1695376800-1695382200@cmsa.fas.harvard.edu
SUMMARY:Floquet codes\, automorphisms\, and quantum computation
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Margarita Davydova (MIT) \nTitle: Floquet codes\, automorphisms\, and quantum computation \nAbstract: In this talk\, I will introduce a new kind of measurement-based quantum computation inspired by Floquet codes. In this model\, the quantum logical gates are implemented by short sequences of low-weight measurements which simultaneously encode logical information and enable error correction. We introduce a new class of quantum error-correcting codes generalizing Floquet codes that achieve this\, which we call dynamic automorphism (DA) codes. \nAs in Floquet codes\, the instantaneous codespace of a DA code at any fixed point in time is that of a topological code. In this case\, the quantum computation can be viewed as a sequence of time-like domain walls implementing automorphisms of the topological order\, which can be understood in terms of reversible anyon condensation paths in a particular parent model. This talk will introduce all of these concepts as well as provide a new perspective for thinking about Floquet codes. \nThe explicit examples that we construct\, which we call DA color codes\, can implement the full Clifford group of logical gates in 2+1d by two- and\, rarely three-body measurements. Using adaptive two-body measurements\, we can achieve a non-Clifford gate in 3+1d\, making the first step towards universal quantum computation in this model. \nThe talk is based on recent work with Nathanan Tantivasadakarn\, Shankar Balasubramanian\, and David Aasen [arxiv: 2307.10353].
URL:https://cmsa.fas.harvard.edu/event/qm_92223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.22.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230922T120000
DTEND;TZID=America/New_York:20230922T130000
DTSTAMP:20260503T233054
CREATED:20240223T112106Z
LAST-MODIFIED:20240223T112106Z
UID:10002861-1695384000-1695387600@cmsa.fas.harvard.edu
SUMMARY:Modularity of Landau-Ginzburg Models
DESCRIPTION:Member Seminar \nSpeaker: Chuck Doran \nTitle: Modularity of Landau-Ginzburg Models \nAbstract: Fano varieties are the basic building blocks of algebraic varieties. Smooth Fano varieties have been classified in dimensions one (the projective line)\, two (del Pezzo surfaces)\, and three (Mori-Mukai classification). What does Mirror Symmetry have to say about such classifications? By studying the Landau-Ginzburg models mirror to smooth Fano threefolds we can transform the Mori-Mukai classification into an effective uniruledness result for moduli spaces of certain K3 and abelian surfaces. This is joint work with Andrew Harder\, Ludmil Katzarkov\, Mikhail Ovcharenko\, and Victor Przjalkowski (arXiv:2307.15607). \n \n
URL:https://cmsa.fas.harvard.edu/event/member-seminar-92223/
LOCATION:Common Room\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230922T160000
DTEND;TZID=America/New_York:20230922T180000
DTSTAMP:20260503T233054
CREATED:20230904T063853Z
LAST-MODIFIED:20240710T192912Z
UID:10001124-1695398400-1695405600@cmsa.fas.harvard.edu
SUMMARY:CMSA/Math Fall Gathering
DESCRIPTION:Friday\, Sep 22\, 2023\n\n4:00 pm\n\nAll CMSA and Math affiliates are invited.
URL:https://cmsa.fas.harvard.edu/event/fallgathering2023/
LOCATION:Common Room\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Event
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230925T100000
DTEND;TZID=America/New_York:20230925T113000
DTSTAMP:20260503T233054
CREATED:20240222T090151Z
LAST-MODIFIED:20240222T090151Z
UID:10002792-1695636000-1695641400@cmsa.fas.harvard.edu
SUMMARY:Species Scale across String Moduli Spaces
DESCRIPTION:Algebraic Geometry in String Theory Seminar \n\nPre-talk Speaker: David Wu (Harvard Physics): 10:00-10:30 am \nSpeaker: Damian van de Heisteeg\, CMSA \n\nTitle: Species Scale across String Moduli Spaces \nAbstract: String theories feature a wide array of moduli spaces. We propose that the energy cutoff scale of these theories – the so-called species scale – can be determined through higher-curvature corrections. This species scale varies with the moduli; we use it both asymptotically to bound the diameter of the field space\, as well as in the interior to determine a “desert point” where it is maximized.
URL:https://cmsa.fas.harvard.edu/event/agst-92523/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230926T110000
DTEND;TZID=America/New_York:20230926T120000
DTSTAMP:20260503T233054
CREATED:20240223T104632Z
LAST-MODIFIED:20240813T160129Z
UID:10002850-1695726000-1695729600@cmsa.fas.harvard.edu
SUMMARY:Geometry at Strong coupling for amplitudes/Wilson loops
DESCRIPTION:General Relativity Seminar \nSpeaker: Lionel Mason (Oxford) \nTitle: Geometry at Strong coupling for amplitudes/Wilson loops \nAbstract: The amplitude/Wilson loop correspondence identifies planar N=4 super-Yang-Mills amplitudes with certain null polygonal Wilson loops at all the values of the coupling. At strong coupling this equates the amplitude/Wilson loop computed by Alday & Maldacena in terms of the area of a minimal surface in AdS_5. To do so they developed a `Y-system’ for computing the amplitude. This talk re-interprets their construction as providing the underlying twistor space for a hyperKahler structure on the corresponding space of kinematic data. In particular\, the area is given by a Kahler scalar for the pseudo-hyperkahler structure and satisfies a version of the Plebanski equations\, a well-known completely integrable system. This geometry encodes the properties of the space of kinematic data on which the amplitude depends as a cluster variety tying into its positive geometry and cluster variety structure. Similar constructures are possible for other cluster varieties corresponding to form factors and beyond.
URL:https://cmsa.fas.harvard.edu/event/gr_92623/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.26.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230926T123000
DTEND;TZID=America/New_York:20230926T133000
DTSTAMP:20260503T233054
CREATED:20240223T081626Z
LAST-MODIFIED:20240223T081646Z
UID:10002835-1695731400-1695735000@cmsa.fas.harvard.edu
SUMMARY:CMSA Q and A Seminar 9/26/2023
DESCRIPTION:CMSA Q and A Seminar \nSpeakers: Michael Douglas (CMSA) and Mayuko Yamashita (Kyoto University) \nTopics: \nMichael Douglas: “What is non-commutative field theory?”\n\nMayuko Yamashita: “What is differential cohomology?”
URL:https://cmsa.fas.harvard.edu/event/cmsaqa_92623/
LOCATION:Common Room\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:CMSA Q&A Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230927T140000
DTEND;TZID=America/New_York:20230927T150000
DTSTAMP:20260503T233054
CREATED:20240227T082824Z
LAST-MODIFIED:20240227T082824Z
UID:10002872-1695823200-1695826800@cmsa.fas.harvard.edu
SUMMARY:Transformers for maths\, and maths for transformers
DESCRIPTION:New Technologies in Mathematics Seminar \nSpeaker: François Charton\, Meta AI \nTitle: Transformers for maths\, and maths for transformers \nAbstract: Transformers can be trained to solve problems of mathematics. I present two recent applications\, in mathematics and physics: predicting integer sequences\, and discovering the properties of scattering amplitudes in a close relative of Quantum ChromoDynamics. \nProblems of mathematics can also help understand transformers. Using two examples from linear algebra and integer arithmetic\, I show that model predictions can be explained\, that trained models do not confabulate\, and that carefully choosing the training distributions can help achieve better\, and more robust\, performance. \n \n \n
URL:https://cmsa.fas.harvard.edu/event/nt-92723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-NTM-Seminar-09.27.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230927T153000
DTEND;TZID=America/New_York:20230927T163000
DTSTAMP:20260503T233054
CREATED:20240223T112514Z
LAST-MODIFIED:20240223T112647Z
UID:10002862-1695828600-1695832200@cmsa.fas.harvard.edu
SUMMARY:Large deviations for the 3D dimer model
DESCRIPTION:Probability Seminar \nSpeaker: Catherine Wolfram (MIT) \nTitle: Large deviations for the 3D dimer model \nAbstract: A dimer tiling of Z^d is a collection of edges such that every vertex is covered exactly once. In 2000\, Cohn\, Kenyon\, and Propp showed that 2D dimer tilings satisfy a large deviations principle. In joint work with Nishant Chandgotia and Scott Sheffield\, we prove an analogous large deviations principle for dimers in 3D. A lot of the results for dimers in two dimensions use tools and exact formulas (e.g. the height function representation of a tiling or the Kasteleyn determinant formula) that are specific to dimension 2. In this talk\, I will try to give some intuition for why three dimensions is different from two\, explain how to formulate the large deviations principle in 3D\, show simulations\, and explain some of the ways that we use a smaller set of tools (e.g. Hall’s matching theorem or a double dimer swapping operation) in our arguments. \n
URL:https://cmsa.fas.harvard.edu/event/probability-92723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Probability-Seminar-09.27.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230928T130000
DTEND;TZID=America/New_York:20230928T140000
DTSTAMP:20260503T233054
CREATED:20240223T072654Z
LAST-MODIFIED:20240223T072654Z
UID:10002827-1695906000-1695909600@cmsa.fas.harvard.edu
SUMMARY:Strongly driven mixtures and membranes: Out of equilibrium surprises
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Max Lavrentovich\, Worcester State University \nTitle: Strongly driven mixtures and membranes: Out of equilibrium surprises \nAbstract: The more prosaic cousin of active matter\, driven inactive matter\, is still full of unexpected phenomena. I will discuss two projects involving two seemingly mundane systems\, a phase-separating colloidal mixture and a lipid membrane\, which demonstrate counterintuitive properties when driven out of equilibrium. We will see that the phase separating mixture\, when driven by a uniform force\, develops (in simulations) an intriguing pattern with a characteristic length scale set by the magnitude of the drive. We will look at some theoretical approaches to understanding the pattern formation and possible experimental realizations. The membrane\, when driven by an oscillatory electric field\, develops (in experiments) a long-lived metastable state with a decreased capacitance and increased dissipation. This state may have implications for neuronal processing and memory formation.
URL:https://cmsa.fas.harvard.edu/event/am-92823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-09.28.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230928T163000
DTEND;TZID=America/New_York:20230928T180000
DTSTAMP:20260503T233054
CREATED:20240221T112307Z
LAST-MODIFIED:20240813T161833Z
UID:10002780-1695918600-1695924000@cmsa.fas.harvard.edu
SUMMARY:Quantum field theory approach to quantum information
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Cenke Xu (UCSB) \nTitle: Quantum field theory approach to quantum information \nAbstract: We apply the formalism of quantum field theory and Euclidean space-time path integral to investigate a class of quantum information problems. In particular\, we investigate quantum many-body systems under weak-measurement and decoherence. The Euclidean space-time path integral allows us to map this problem to a quantum field theory with (temporal) boundary or defects. We therefore investigate two types of quantum many-body systems with nontrivial boundary physics: quantum critical points\, and states with nontrivial topology\, such as Chern insulator and symmetry protected topological states. For example\, we demonstrate that a Wilson-Fisher quantum critical point can be driven into an “extraordinary-log” phase after weak-measurement. Another example is that\, we argue that a system with higher form symmetry may be driven to a self-dual phase transition under weak measurement.
URL:https://cmsa.fas.harvard.edu/event/qm_92823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.28.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230929T120000
DTEND;TZID=America/New_York:20230929T130000
DTSTAMP:20260503T233054
CREATED:20240223T112516Z
LAST-MODIFIED:20240223T112516Z
UID:10002863-1695988800-1695992400@cmsa.fas.harvard.edu
SUMMARY:Moduli of vector bundles on curve and semiorthogonal decomposition
DESCRIPTION:Member Seminar \nSpeaker: Kai Xu (CMSA) \nTitle: Moduli of vector bundles on curve and semiorthogonal decomposition \nAbstract: In this talk we construct semiorthogonal decompositions of moduli of vector bundles on a curve into its symmetric powers. The essential ingredients in the proof include Borel-Weil-Bott theory for loop groups\, derived Schur-Weyl duality for current groups and derived Θ-stratification. \n
URL:https://cmsa.fas.harvard.edu/event/member-seminar-92923/
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:20230929T140000
DTEND;TZID=America/New_York:20230929T150000
DTSTAMP:20260503T233054
CREATED:20240223T103610Z
LAST-MODIFIED:20240223T103610Z
UID:10002848-1695996000-1695999600@cmsa.fas.harvard.edu
SUMMARY:Topological modular forms and heretoric string theory
DESCRIPTION:Special Seminar\n\n\n\n\n\nSpeaker: Mayuko Yamashita\, Kyoto University \n\nTitle: Topological modular forms and heretoric string theory \nAbstract: In this talk I will explain my works with Y. Tachikawa to study anomaly in heterotic string theory via homotopy theory\, especially the theory of Topological Modular Forms (TMF). TMF is an E-infinity ring spectrum which is conjectured by Stolz-Teichner to classify two-dimensional supersymmetric quantum field theories in physics. In the previous work (https://arxiv.org/abs/2108.13542)\, we proved the vanishing of anomalies in heterotic string theory mathematically by using TMF. \nFurthermore\, we have a recent update (https://arxiv.org/abs/2305.06196) on the previous work. Because of the vanishing result\, we can consider a secondary transformation of spectra\, which is shown to coincide with the Anderson self-duality morphism of TMF. This allows us to detect subtle torsion phenomena in TMF by differential-geometric ways\, and leads us to new conjectures on the relation between VOAs and TMF. \n\n
URL:https://cmsa.fas.harvard.edu/event/ss_92923/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Special-Seminar-09.29.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231002T103000
DTEND;TZID=America/New_York:20231002T113000
DTSTAMP:20260503T233054
CREATED:20240222T084421Z
LAST-MODIFIED:20240222T084421Z
UID:10002791-1696242600-1696246200@cmsa.fas.harvard.edu
SUMMARY:Motivic decomposition of moduli space from brane dynamics
DESCRIPTION:Algebraic Geometry in String Theory Seminar \n\n\nPre-talk Speaker: Kai Xu (CMSA): 10:00-10:30 am \n\nSpeaker: Kai Xu (CMSA) \nTitle: Motivic decomposition of moduli space from brane dynamics \nAbstract: Supersymmetric gauge theories encode deep structures in algebraic geometry\, and geometric engineering gives a powerful way to understand the underlying structures by string/M theory. In this talk we will see how the dynamics of M5 branes tell us about the motivic and semiorthogonal decompositions of moduli of bundles on curves.
URL:https://cmsa.fas.harvard.edu/event/agst-10223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-10.02.2023.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231002T163000
DTEND;TZID=America/New_York:20231002T173000
DTSTAMP:20260503T233054
CREATED:20240227T095159Z
LAST-MODIFIED:20240227T095159Z
UID:10002874-1696264200-1696267800@cmsa.fas.harvard.edu
SUMMARY:Gravitational Instantons
DESCRIPTION:Speaker: Yu-Shen Lin (Boston University) \nTitle: Gravitational Instantons \nAbstract: Gravitational instantons were introduced by Hawking as building blocks of his Euclidean quantum gravity theory back in the 1970s. These are non-compact Calabi-Yau surfaces with L2 curvature and thus can be viewed as the non-compact analogue of K3 surfaces. K3 surfaces are 2-dimensional Calabi-Yau manifolds and are usually the testing stone before conquering the general Calabi-Yau problems. The moduli space of K3 surfaces and its compactification on their own form important problems in various branches in geometry. In this talk\, we will discuss the Torelli theorem of gravitational instantons\, how the cohomological invariants of a gravitational instanton determine them. As a consequence\, this leads to a description of the moduli space of gravitational instantons.
URL:https://cmsa.fas.harvard.edu/event/colloquium-10223/
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-10.02.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231003T110000
DTEND;TZID=America/New_York:20231003T120000
DTSTAMP:20260503T233054
CREATED:20240223T054715Z
LAST-MODIFIED:20240223T054715Z
UID:10002820-1696330800-1696334400@cmsa.fas.harvard.edu
SUMMARY:A Smooth Horizon without a Smooth Horizon
DESCRIPTION:General Relativity Seminar \nSpeaker: Chethan Krishnan (IISc Bangalore) \nTitle: A Smooth Horizon without a Smooth Horizon \nAbstract: I will talk about some work that is about to appear\, where we note one precise way in which the stretched horizon can simulate a smooth horizon. I will also make an effort to put things in some perspective (brickwalls\, fuzzballs\, Type I algebras\,…)
URL:https://cmsa.fas.harvard.edu/event/gr_10323/
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231003T123000
DTEND;TZID=America/New_York:20231003T133000
DTSTAMP:20260503T233054
CREATED:20240223T082622Z
LAST-MODIFIED:20240223T082622Z
UID:10002836-1696336200-1696339800@cmsa.fas.harvard.edu
SUMMARY:CMSA Q and A Seminar 10/3/2023
DESCRIPTION:CMSA Q and A Seminar \nSpeakers: Dan Freed (Harvard Math & CMSA) and Dan Berwick-Evans (University of Illinois at Urbana-Champaign)\n\nTopics:\nDan Freed: What is framing anomaly? How is it different from other anomalies?\nDan Berwick-Evans: What is Atiyah-Singer index theorem?
URL:https://cmsa.fas.harvard.edu/event/cmsaqa_10323/
LOCATION:Common Room\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:CMSA Q&A Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231004T103000
DTEND;TZID=America/New_York:20231004T113000
DTSTAMP:20260503T233054
CREATED:20240221T111722Z
LAST-MODIFIED:20240221T111849Z
UID:10002779-1696415400-1696419000@cmsa.fas.harvard.edu
SUMMARY:Dipolar and modulated symmetry protected topological phases
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Ho Tat Lam\, MIT \nTitle: Dipolar and modulated symmetry protected topological phases \nAbstract: Modulated symmetries are symmetries whose symmetry generators exhibit spatial modulations. We will discuss one-dimensional symmetry protected topological (SPT) phases protected by modulated symmetries. We will present a simple recipe for constructing modulated SPT models by generalizing the concept of decorated domain walls. We will then focus on the simplest modulated SPT protected by dipolar symmetries\, classify them using matrix product states and construct their response field theories using twisted finite tensor gauge theories.
URL:https://cmsa.fas.harvard.edu/event/tqms_10423/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-10.04.23.png
END:VEVENT
END:VCALENDAR