BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CMSA - ECPv6.15.18//NONSGML v1.0//EN CALSCALE:GREGORIAN METHOD:PUBLISH X-ORIGINAL-URL:https://cmsa.fas.harvard.edu X-WR-CALDESC:Events for CMSA REFRESH-INTERVAL;VALUE=DURATION:PT1H X-Robots-Tag:noindex X-PUBLISHED-TTL:PT1H BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20220313T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20221106T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20230312T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20231105T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20240310T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20241103T060000 END:STANDARD END:VTIMEZONE BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20220313T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20221106T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20230312T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20231105T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20240310T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20241103T060000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTART;TZID=America/New_York:20231201T120000 DTEND;TZID=America/New_York:20231201T130000 DTSTAMP:20260501T200520 CREATED:20240227T112716Z LAST-MODIFIED:20240227T112731Z UID:10002878-1701432000-1701435600@cmsa.fas.harvard.edu SUMMARY:An introduction to mixture of experts in deep learning DESCRIPTION:Member Seminar \nSpeaker: Samy Jelassi \nTitle: An introduction to mixture of experts in deep learning \nAbstract: Scale has opened new frontiers in natural language processing – but at a high cost. Mixture-of-Experts (MoE) have been proposed as a path to even larger and more capable language models. They select different parameters for each incoming example. By doing so\, the parameter count is decoupled from the compute per example leading to very large\, but efficient models. In this talk\, I will review the concept of mixture of experts\, provide a basic description of the Switch Transformers model\, characterize some of their behaviors and conclude by highlighting some open problems in the field. This talk is mainly based on the following papers: https://arxiv.org/pdf/2101.03961.pdf\, https://arxiv.org/pdf/2209.01667.pdf . URL:https://cmsa.fas.harvard.edu/event/member-seminar-12123/ 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:20231201T163000 DTEND;TZID=America/New_York:20231201T173000 DTSTAMP:20260501T200520 CREATED:20230802T170029Z LAST-MODIFIED:20240813T162053Z UID:10001173-1701448200-1701451800@cmsa.fas.harvard.edu SUMMARY:A Plane Defect in the 3d O(N) Model DESCRIPTION:Quantum Matter Seminar \nSpeaker: Abijith Krishnan (MIT) \nTitle: A Plane Defect in the 3d O(N) Model \nAbstract: It was recently found that the classical 3d O(N) model in the semi-infinite geometry can exhibit an “extraordinary-log” boundary universality class\, where the spin-spin correlation function on the boundary falls off as (log x)^(-q). This universality class exists for a range 2≤N3. In this talk\, I’ll extend this result to the 3d O(N) model in an infinite geometry with a plane defect. I’ll explain using the renormalization group (RG) that the extraordinary-log universality class is present for any finite N≥2\, and that a line of defect fixed points is present at N=∞. This line of defect fixed points is lifted to the ordinary\, special (no defect) and extraordinary-log universality classes by 1/N corrections. I’ll show that the line of defect fixed points and the 1/N corrections agree with an a-theorem by Jensen and O’Bannon for 3d CFTs with a boundary. Finally\, I’ll conclude by noting some physical systems where the extraordinary-log universality class can be observed. \n  URL:https://cmsa.fas.harvard.edu/event/qm_33123/ LOCATION:Hybrid CATEGORIES:Quantum Matter ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-12.01.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231201T163000 DTEND;TZID=America/New_York:20231201T173000 DTSTAMP:20260501T200520 CREATED:20240222T101228Z LAST-MODIFIED:20240222T103010Z UID:10002799-1701448200-1701451800@cmsa.fas.harvard.edu SUMMARY:Quantum information: the interplay of mathematics and physics DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Kaifeng Bu (Harvard University) \nTitle: Quantum information: the interplay of mathematics and physics \nAbstract: I will provide an introduction to quantum information\, which points to a new connection with experiment on the one hand\, and a potential new area of mathematical analysis on the other. I will introduce two recent results about the application of this new area in quantum information: (1) a novel Quantum Central Limit Theorem (QCLT)\, and (2) a physically realizable protocol for testing and measuring quantum advantage. This talk is based on a collaboration with Arthur Jaffe\, and Weichen Gu (PNAS120(25)2023\, arXiv: 2302.08423\, arXiv:2306.09292). \n  URL:https://cmsa.fas.harvard.edu/event/tqms_12123/ 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-12.01.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231204T103000 DTEND;TZID=America/New_York:20231204T113000 DTSTAMP:20260501T200520 CREATED:20240222T065433Z LAST-MODIFIED:20240222T152910Z UID:10002786-1701685800-1701689400@cmsa.fas.harvard.edu SUMMARY:CM-minimizers and standard models of Fano fibrations over curves DESCRIPTION:Algebraic Geometry in String Theory Seminar \n\nSpeaker: Maksym Fedorchuk (Boston College) \nTitle: CM-minimizers and standard models of Fano fibrations over curves \nAbstract: A recent achievement in K-stability of Fano varieties is an algebro-geometric construction of a projective moduli space of K-polystable Fanos. The ample line bundle on this moduli space is the CM line bundle of Tian. One of the consequences of the general theory is that given a family of K-stable Fanos over a punctured curve\, the polystable filling is the one that minimizes the degree of the CM line bundle after every finite base change. A natural question is to ask what are the CM-minimizers without base change. In answering this question\, we arrive at a theory of Koll\’ar stability for fibrations over one-dimensional bases\, and standard models of Fano fibrations. I will explain the joint work with Hamid Abban and Igor Krylov in which we show that the CM-minimizers for del Pezzo fibrations are Corti’s standard models and related work in progress on quartic threefold hypersurfaces. \n\n  URL:https://cmsa.fas.harvard.edu/event/agst-12423/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Algebraic Geometry in String Theory Seminar ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-AGIST-12.04.23-scaled.jpg END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231204T140000 DTEND;TZID=America/New_York:20231204T150000 DTSTAMP:20260501T200520 CREATED:20240226T112024Z LAST-MODIFIED:20240226T112046Z UID:10002869-1701698400-1701702000@cmsa.fas.harvard.edu SUMMARY:The Fractional Quantum Hall Effect at ν=5/2: Past\, Recent\, and Future DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker:  Ken K. W. Ma (Northeastern University) \nTitle: The Fractional Quantum Hall Effect at ν=5/2: Past\, Recent\, and Future \nAbstract: The discovery of fractional quantum Hall (FQH) states started a new chapter in modern physics. Nowadays\, more than 70 FQH states at different filling factors have been observed. Among them\, the FQH state at the filling factor ν=5/2 in GaAs (or the 5/2 state) remains one of the most special and attractive states. Since its discovery in 1987\, different possible topological orders have been proposed to describe the 5/2 state. Some of them can host an exotic type of particles\, known as non-Abelian anyons. Recent experiments have provided more insights into the understanding of the 5/2 state\, but its underlying nature is still under debate. \nIn this talk\, I will review the basics of the 5/2 state [1] and a more unified theoretical description of different possible topological orders of the 5/2 state that we have recently proposed [2]. I will also review the groundbreaking thermal Hall conductance experiment [3] and the follow-up quantum Hall interface experiments by the Weizmann Institute group [4\, 5]\, and discuss what possible lessons that we can learn from the experimental results. Lastly\, I will talk about some possible directions and related topics for future investigations. \nReferences: \n[1] K. K. W. Ma\, M. R. Peterson\, V. W. Scarola\, and K. Yang\, “Fractional quantum Hall effect at the filling factor ν = 5/2” in Encyclopedia of Condensed Matter Physics (Second Edition)\, edited by T. Chakraborty\, Academic Press (2024).\n[2] K. K. W. Ma and D. E. Feldman\, “The sixteenfold way and the quantum Hall effect at half-integer filling factors”\, Phys. Rev. B 100\, 035302 (2019).\n[3] M. Banerjee\, M. Heiblum\, V. Umansky\, D. E. Feldman\, Y. Oreg\, and A. Stern\, “Observation of half-integer thermal Hall conductance”\, Nature (London) 559\, 205 (2018).\n[4] B. Dutta\, W. Yang\, R. Melcer\, H. K. Kundu\, M. Heiblum\, V. Umansky\, Y. Oreg\, A. Stern\, D. Mross\, “Distinguishing between non-Abelian topological orders in a quantum Hall system”\, Science 375\, 193 (2021).\n[5] B. Dutta\, V. Umansky\, M. Banerjee\, and M. Heiblum\, “Isolated ballistic non-Abelian interface channel”\, Science 377\, 1198 (2022). \n  URL:https://cmsa.fas.harvard.edu/event/tqms_12423/ 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-12.04.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231204T163000 DTEND;TZID=America/New_York:20231204T173000 DTSTAMP:20260501T200520 CREATED:20240223T075301Z LAST-MODIFIED:20240223T075301Z UID:10002830-1701707400-1701711000@cmsa.fas.harvard.edu SUMMARY:Analysis of ALH* gravitational instantons DESCRIPTION:Speaker: Xuwen Zhu (Northeastern) \nTitle: Analysis of ALH* gravitational instantons \nAbstract: Gravitational instantons are non-compact Calabi-Yau metrics with L^2 bounded curvature and are categorized into six types. We will discuss one such type called ALH* metrics which has a non-compact end modelled by the Calabi ansatz with inhomogeneous collapsing near infinity. Such metrics appeared recently in the works on SYZ conjecture\, as well as the scaling bubble limits for codimension-3 collapsing of K3 surfaces\, where the study of its Laplacian played a central role. In this talk I will talk about the Fredholm mapping property and L^2 cohomology of such metrics. This is ongoing work joint with Rafe Mazzeo. URL:https://cmsa.fas.harvard.edu/event/colloquium-12423/ 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-12.04.2023.docx-1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231205T110000 DTEND;TZID=America/New_York:20231205T120000 DTSTAMP:20260501T200520 CREATED:20240226T112803Z LAST-MODIFIED:20240813T160712Z UID:10002870-1701774000-1701777600@cmsa.fas.harvard.edu SUMMARY:The Feynman propagator and self-adjointness DESCRIPTION:General Relativity Seminar \nSpeaker: Andras Vasy (Stanford) \nTitle: The Feynman propagator and self-adjointness \nAbstract: In this talk I will discuss the Feynman and anti-Feynman inverses for wave operators on certain Lorentzian manifolds; these are two inverses which from a microlocal analysis perspective are more natural than the standard causal (advanced/retarded) ones. For instance\, for the spectral family of the wave operator\, these are the natural inverses when the spectral parameter is non-real. Indeed\, I will explain that these connect to the self-adjointness of the wave operator\, and the positivity properties that follow. \n  URL:https://cmsa.fas.harvard.edu/event/gr_12523/ LOCATION:Virtual CATEGORIES:General Relativity Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-12.05.2023.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231205T123000 DTEND;TZID=America/New_York:20231205T133000 DTSTAMP:20260501T200520 CREATED:20240223T084615Z LAST-MODIFIED:20240223T084615Z UID:10002841-1701779400-1701783000@cmsa.fas.harvard.edu SUMMARY:CMSA Q and A Seminar 12/5/2023 DESCRIPTION:CMSA Q and A Seminar \nSpeakers: Mike Douglas (Harvard CMSA) and Anurag Anshu (Harvard Computer Science) \nTopics: \nMike Douglas: What are scaling laws in deep learning? \nAnurag Anshu: What’s the difference between classical information theory and quantum information theory (or classical computation vs quantum computation)? \n  URL:https://cmsa.fas.harvard.edu/event/cmsaqa_12523/ 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:20231207T130000 DTEND;TZID=America/New_York:20231207T140000 DTSTAMP:20260501T200520 CREATED:20240223T055715Z LAST-MODIFIED:20240223T055715Z UID:10002823-1701954000-1701957600@cmsa.fas.harvard.edu SUMMARY:Active structures and flows in living cells DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Michael Shelley (Flatiron) \nTitle: Active structures and flows in living cells \nAbstract: Flows in the fluidic interior of living cells can serve biological function or act as signatures of how intracellular forces are exerted. I’ll discuss examples of each. One is understanding the emergence of cell-spanning vortical flows in large developing egg cells\, while the other arises in studying the nature of force transduction in single cell embryos moving towards their first cell division. Both involve the cytoskeleton\, that set of polymers\, cross-linkers\, and molecular motors that underlie much of the active mechanics within cells\, and has led to the development of new coarse-grained active matter models and novel instabilities. URL:https://cmsa.fas.harvard.edu/event/am-12723/ 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-12.07.23.docx-1.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231208T120000 DTEND;TZID=America/New_York:20231208T130000 DTSTAMP:20260501T200520 CREATED:20240227T112413Z LAST-MODIFIED:20240227T112426Z UID:10002877-1702036800-1702040400@cmsa.fas.harvard.edu SUMMARY:Open Problems in Physics and Novel Solutions from Math DESCRIPTION:Member Seminar \nSpeaker: Juven Wang \nTitle: Open Problems in Physics and Novel Solutions from Math \n  \nAbstract: (1) How do neutrinos obtain tiny mass and oscillate between e\, \mu\, \tau three flavors? What consists of Dark Matter? What causes leptogenesis and baryogenesis? \n(2) Why the Parity Symmetry is violated in the weak interaction? How do we quantum mechanically regularize and numerically simulate the Standard Model (chiral fermion/gauge theory) on the lattice in 3+1 spacetime dimensions? \n(3) Strong CP problem: Why is the neutron electric dipole moment nearly zero and QCD respects the CP = T symmetry? \n(4) Family/Generation problem: Why are there three families/generations of quarks and leptons? \nIn my talk\, I will sketch and propose novel solutions to these challenging open problems in physics based on my own work (available on arXiv\, some jointly with my collaborators). \nI will show that the eclectic cross-disciplinary fertilization of ideas between the Math-Physics geometry and topology\, Quantum Condensed Matter\, and High-Energy Physics (theory\, pheno\, lattice) can help solving these big problems. \nThe (1) answer relates to Ultra Unification: a Z_{16} class Atiyah-Patodi-Singer eta invariant (Baryon – Lepton)-protected topological superconductor and a symmetry-extended anomalous topological quantum field theory. \nThe (2) and (3) answers relate to a trivial cobordism class and Symmetric Mass Generation\, and disordering and removing the Pecci-Quinn axions. \nThe (4) answer has to do with the Hirzebruch signature and Atiyah-Singer index theorem\, gravitational Chern-Simons theory\, and 3 E8 quantum Hall states. \n  URL:https://cmsa.fas.harvard.edu/event/member-seminar-12823/ 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:20231208T143000 DTEND;TZID=America/New_York:20231208T160000 DTSTAMP:20260501T200520 CREATED:20240221T100009Z LAST-MODIFIED:20240221T100109Z UID:10002772-1702045800-1702051200@cmsa.fas.harvard.edu SUMMARY:Fermi surface symmetric mass generation and its application in nickelate superconductor DESCRIPTION:Joint Quantum Matter in Mathematics and Physics & Topological Quantum Matter Seminar \nSpeaker: Da-Chuan Lu (UCSD) \nTitle: Fermi surface symmetric mass generation and its application in nickelate superconductor \nAbstract: Symmetric mass generation (SMG) is a novel interaction-driven mechanism that generates fermion mass without breaking symmetry\, unlike the standard Anderson-Higgs mechanism. SMG can occur in the fermion system without quantum anomalies. In this talk\, I will focus on the SMG for the systems with finite fermion density\, i.e.\, the Fermi surface. I will discuss the Fermi surface anomaly and Fermi surface SMG. Lastly\, I will talk about its application in the newly found nickelate superconductors\, where the superconductivity emerges without a nearby spontaneous symmetry-breaking phase. URL:https://cmsa.fas.harvard.edu/event/qm_12823/ 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-Quantum-Matter_String-Seminar-12.08.2023.docx-2.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231211T103000 DTEND;TZID=America/New_York:20231211T113000 DTSTAMP:20260501T200520 CREATED:20240221T112820Z LAST-MODIFIED:20240221T112900Z UID:10002782-1702290600-1702294200@cmsa.fas.harvard.edu SUMMARY:M-theory on nodal Calabi-Yau 3-folds and torsion refined GV-invariants DESCRIPTION:Algebraic Geometry in String Theory Seminar \nSpeaker: Thorsten Schimannek (Utrecht University) \n\nTitle: M-theory on nodal Calabi-Yau 3-folds and torsion refined GV-invariants \nAbstract: The physics of M-theory and Type IIA strings on a projective nodal CY 3-folds is determined by the geometry of a small resolution\, even if the latter is not Kähler. We will demonstrate this explicitly in the context of a family of Calabi-Yau double covers of P^3. Using conifold transitions\, we prove that the exceptional curves in any small resolution are torsion while M-theory develops a discrete gauge symmetry.This leads to a torsion refinement of the ordinary Gopakumar-Vafa invariants\, that is associated to the singular Calabi-Yau and captures the enumerative geometry of the non-Kähler resolutions. We further argue that twisted circle compactifications of the 5d theory are dual to IIA compactifications on the nodal CY 3-fold with a flat but topologically non-trivial B-field. As a result\, the torsion refined invariants are encoded in the topological string partition functions with different choices for the global topology of a flat B-field. \nThe talk is based on 2108.09311\, 2212.08655 (with S. Katz\, A. Klemm\, and E. Sharpe) and 2307.00047 (with S. Katz). URL:https://cmsa.fas.harvard.edu/event/agst-121123/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Algebraic Geometry in String Theory Seminar ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-12.11.2023-scaled.jpg END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231211T163000 DTEND;TZID=America/New_York:20231211T173000 DTSTAMP:20260501T200520 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 BEGIN:VEVENT DTSTART;TZID=America/New_York:20231214T143000 DTEND;TZID=America/New_York:20231214T160000 DTSTAMP:20260501T200520 CREATED:20240109T001602Z LAST-MODIFIED:20240109T001934Z UID:10001133-1702564200-1702569600@cmsa.fas.harvard.edu SUMMARY:When does a three-dimensions Chern-Simons theory have a time reversal symmetry? DESCRIPTION:Speaker: Roman Geiko (UCLA) \nTitle: When does a three-dimensions Chern-Simons theory have a time reversal symmetry? \nIn this talk\, I will discuss the time reversal invariance of (spin-) Chern-Simons theory in 3 dimensions at both classical and quantum levels. I will show how to obtain a complete classification of Abelian anyons with the time reversal symmetry expressed in terms of the higher Gauss sums. Then\, I will comment on the time reversal symmetry of Chern-Simons in the non-Abelian case. URL:https://cmsa.fas.harvard.edu/event/qm_121423/ LOCATION:Virtual CATEGORIES:Quantum Matter ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-12.14.2023.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231215T100000 DTEND;TZID=America/New_York:20231215T113000 DTSTAMP:20260501T200520 CREATED:20240222T093357Z LAST-MODIFIED:20240222T093357Z UID:10002796-1702634400-1702639800@cmsa.fas.harvard.edu SUMMARY:Exact lattice chiral symmetry in 2d gauge theory DESCRIPTION:Quantum Matter Seminar \nSpeaker: Aleksey Cherman (UMN) \nTitle: Exact lattice chiral symmetry in 2d gauge theory \nAbstract: Preserving the symmetries of massless fermions is a well-known challenge in lattice field theory.  I’ll discuss symmetry-preserving lattice regularizations of 2d QED with one and two flavors of Dirac fermions\, as well as the `3450′ chiral gauge theory. The construction leverages bosonization and recently-proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum\, the anomalies are reproduced at finite lattice spacing\, and in each case we’ve found a sign-problem-free dual formulation. URL:https://cmsa.fas.harvard.edu/event/qm_121523/ LOCATION:Virtual CATEGORIES:Quantum Matter ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-12.15.23.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20231215T120000 DTEND;TZID=America/New_York:20231215T130000 DTSTAMP:20260501T200520 CREATED:20240227T111152Z LAST-MODIFIED:20240227T111152Z UID:10002876-1702641600-1702645200@cmsa.fas.harvard.edu SUMMARY:On compactness phenomena DESCRIPTION:Member Seminar \nSpeaker: Alejandro Poveda \nTitle: On compactness phenomena \nAbstract: In this presentation I shall be preoccupied with compactness phenomena in set theory. Compactness is the phenomenon by which the local properties of a mathematical structure determine its global behavior. This phenomenon is intrinsic to the very architecture of the mathematical universe and manifests to us in a cornucopia of forms. Over the past fifty years\, the study of compactness phenomena has been a cornerstone of research in set theory. This talk will present recent discoveries regarding compactness principles\, spanning classical themes like the tree property and stationary reflection\, while also forging novel connections with other topics\, such as Woodin’s HOD Conjecture. URL:https://cmsa.fas.harvard.edu/event/member-seminar-121523/ LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States CATEGORIES:Member Seminar END:VEVENT END:VCALENDAR