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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221024T090000
DTEND;TZID=America/New_York:20221024T103000
DTSTAMP:20260503T174143
CREATED:20240214T114116Z
LAST-MODIFIED:20240229T111301Z
UID:10002706-1666602000-1666607400@cmsa.fas.harvard.edu
SUMMARY:Insulating BECs and other surprises in dipole-conserving systems
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Ethan Lake (MIT) \nTitle: Insulating BECs and other surprises in dipole-conserving systems \nAbstract: I will discuss recent work on bosonic models whose dynamics conserves both total charge and total dipole moment\, a situation which can be engineered in strongly tilted optical lattices. Related models have received significant attention recently for their interesting out-of-equilibrium dynamics\, but analytic and numeric studies reveal that they also possess rather unusual ground states. I will focus in particular on a dipole-conserving variant of the Bose-Hubbard model\, which realizes an unusual phase of matter that possesses a Bose-Einstein condensate\, but which is nevertheless insulating\, and has zero superfluid weight. Time permitting\, I will also describe the physics of a regime in which these models spontaneously fracture into an exotic type of glassy state. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_102422/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Quantum-Matter-in-Mathematics-and-Physics-10.24.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221024T110000
DTEND;TZID=America/New_York:20221024T120000
DTSTAMP:20260503T174143
CREATED:20230730T183559Z
LAST-MODIFIED:20240110T045511Z
UID:10001153-1666609200-1666612800@cmsa.fas.harvard.edu
SUMMARY:Anomalies of Discrete Gauge Symmetries and their Cancellation in 6D F-theory
DESCRIPTION:Swampland Seminar \nSpeaker: Paul-Konstantin Oehlmann(Northeastern) \nTitle: Anomalies of Discrete Gauge Symmetries and their Cancellation in 6D F-theory \nAbstract: We consider 6D SUGRAs with a discrete gauge group G\, engineered via F-theory compactifications on genus-one fibered threefolds. We argue that group G suffers from Dai-Freed anomalies that can be canceled via a discrete Green-Schwarz mechanism. We comment on the ambiguity to assign this GS term in the 7D Anomaly theory which leads to choices that are not all compatible with F-theory. \nIn F-theory we then deduce this Anomaly coefficient explicitly by computing the elliptic genera of the non-critical strings that couple to the 6D two-form fields: Their 2D worldsheet theories inherits a G Flavor symmetries whose t’Hooft anomaly cancels the 6D Dai-Freed anomaly in the bulk via inflow. This talk is based on work in preparation together with Markus Dierigl and Thorsten Schimmanek.
URL:https://cmsa.fas.harvard.edu/event/swampland_102422/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221025T090000
DTEND;TZID=America/New_York:20221025T103000
DTSTAMP:20260503T174143
CREATED:20240215T102846Z
LAST-MODIFIED:20240229T092911Z
UID:10002741-1666688400-1666693800@cmsa.fas.harvard.edu
SUMMARY:Unorientable Quantum Field Theories: From crosscaps to holography
DESCRIPTION:Quantum Matter Seminar \nSpeaker: João Caetano (CERN) \nTitle: Unorientable Quantum Field Theories: From crosscaps to holography \nAbstract: In two dimensions\, one can study quantum field theories on unorientable manifolds by introducing crosscaps. This defines a class of states called crosscap states which share a few similarities with the notion of boundary states. In this talk\, I will show that integrable theories remain integrable in the presence of crosscaps\, and this allows to exactly determine the crosscap state. \n\n\nIn four dimensions\, the analog is to place the quantum field theory on the real projective space\, the simplest unorientable 4-manifold. I will show how to do this in the example of N=4 Supersymmetric Yang-Mills\, discuss its holographic description and present a new solvable setup of AdS/CFT.
URL:https://cmsa.fas.harvard.edu/event/qm_102522/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-10.25.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221026T090000
DTEND;TZID=America/New_York:20221026T100000
DTSTAMP:20260503T174143
CREATED:20230705T074050Z
LAST-MODIFIED:20240216T112155Z
UID:10001138-1666774800-1666778400@cmsa.fas.harvard.edu
SUMMARY:Kähler bands—Chern insulators\, holomorphicity and induced quantum geometry
DESCRIPTION:Topological Quantum Matter Seminar \n\n\nSpeaker: Bruno Mera\, Tohoku University\n\nTitle: Kähler bands—Chern insulators\, holomorphicity and induced quantum geometry\n\nAbstract: The notion of topological phases has dramatically changed our understanding of insulators. There is much to learn about a band insulator beyond the assertion that it has a gap separating the valence bands from the conduction bands. In the particular case of two dimensions\, the occupied bands may have a nontrivial topological twist determining what is called a Chern insulator. This topological twist is not just a mathematical observation\, it has observable consequences—the transverse Hall conductivity is quantized and proportional to the 1st Chern number of the vector bundle of occupied states over the Brillouin zone. Finer properties of band insulators refer not just to the topology\, but also to their geometry. Of particular interest is the momentum-space quantum metric and the Berry curvature. The latter is the curvature of a connection on the vector bundle of occupied states. The study of the geometry of band insulators can also be used to probe whether the material may host stable fractional topological phases. In particular\, for a Chern band to have an algebra of projected density operators which is isomorphic to the W∞ algebra found by Girvin\, MacDonald and Platzman—the GMP algebra—in the context of the fractional quantum Hall effect\, certain geometric constraints\, associated with the holomorphic character of the Bloch wave functions\, are naturally found and they enforce a compatibility relation between the quantum metric and the Berry curvature of the band. The Brillouin zone is then endowed with a Kähler structure which\, in this case\, is also translation-invariant (flat). Motivated by the above\, we will provide an overview of the geometry of Chern insulators from the perspective of Kähler geometry\, introducing the notion of a Kähler band which shares properties with the well-known ideal case of the lowest Landau level. Furthermore\, we will provide a prescription\, borrowing ideas from geometric quantization\, to generate a flat Kähler band in some appropriate asymptotic limit. Such flat Kähler bands are potential candidates to host and realize fractional Chern insulating phases. Using geometric quantization arguments\, we then provide a natural generalization of the theory to all even dimensions.\n\n\nReferences:\n[1] Tomoki Ozawa and Bruno Mera. Relations between topology and the quantum metric for Chern insulators. Phys. Rev. B\, 104:045103\, Jul 2021.\n[2] Bruno Mera and Tomoki Ozawa. Kähler geometry and Chern insulators: Relations between topology and the quantum metric. Phys. Rev. B\, 104:045104\, Jul 2021.\n[3] Bruno Mera and Tomoki Ozawa. Engineering geometrically flat Chern bands with Fubini-Study  Kähler structure. Phys. Rev. B\, 104:115160\, Sep 2021.
URL:https://cmsa.fas.harvard.edu/event/9062/
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-10.26.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221026T123000
DTEND;TZID=America/New_York:20221026T133000
DTSTAMP:20260503T174143
CREATED:20230817T174027Z
LAST-MODIFIED:20240121T174027Z
UID:10001269-1666787400-1666791000@cmsa.fas.harvard.edu
SUMMARY:Clique listing algorithms
DESCRIPTION:Speaker: Virginia Vassilevska Williams (MIT) \nTitle: Clique listing algorithms \nAbstract: A k-clique in a graph G is a subgraph of G on k vertices in which every pair of vertices is linked by an edge. Cliques are a natural notion of social network cohesiveness with a long history. \nA fundamental question\, with many applications\, is “How fast can one list all k-cliques in a given graph?”. \nEven just detecting whether an n-vertex graph contains a k-Clique has long been known to be NP-complete when k can depend on n (and hence no efficient algorithm is likely to exist for it). If k is a small constant\, such as 3 or 4 (independent of n)\, even the brute-force algorithm runs in polynomial time\, O(n^k)\, and can list all k-cliques in the graph; though O(n^k) time is far from practical. As the number of k-cliques in an n-vertex graph can be Omega(n^k)\, the brute-force algorithm is in some sense optimal\, but only if there are Omega(n^k) k-cliques. In this talk we will show how to list k-cliques faster when the input graph has few k-cliques\, with running times depending on the number of vertices n\, the number of edges m\, the number of k-cliques T and more. We will focus on the case when k=3\, but we will note some extensions. \n(Based on joint work with Andreas Bjorklund\, Rasmus Pagh\, Uri Zwick\, Mina Dalirrooyfard\, Surya Mathialagan and Yinzhan Xu)
URL:https://cmsa.fas.harvard.edu/event/collquium_102722/
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-10.26.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221026T140000
DTEND;TZID=America/New_York:20221026T150000
DTSTAMP:20260503T174143
CREATED:20230808T185319Z
LAST-MODIFIED:20240115T103149Z
UID:10001214-1666792800-1666796400@cmsa.fas.harvard.edu
SUMMARY:From Engine to Auto
DESCRIPTION:New Technologies in Mathematics Seminar \nSpeakers: João Araújo\, Mathematics Department\, Universidade Nova de Lisboa and Michael Kinyon\, Department of Mathematics\, University of Denver \n\nTitle: From Engine to Auto \n\n\nAbstract: Bill McCune produced the program EQP that deals with first order logic formulas and in 1996 managed to solve Robbins’ Conjecture. This very powerful tool reduces to triviality any result that can be obtained by encoding the assumptions and the goals. The next step was to turn the program into a genuine assistant for the working mathematician: find ways to help the prover with proofs; reduce the lengths of the automatic proofs to better crack them;  solve problems in higher order logic; devise tools that autonomously prove results of a given type\, etc.\n\nIn this talk we are going to show some of the tools and strategies we have been producing. There will be real illustrations of theorems obtained for groups\, loops\, semigroups\, logic algebras\, lattices and generalizations\, quandles\, and many more.
URL:https://cmsa.fas.harvard.edu/event/nt-102622/
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-10.26.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221027T103000
DTEND;TZID=America/New_York:20221027T113000
DTSTAMP:20260503T174143
CREATED:20230817T180439Z
LAST-MODIFIED:20240118T090238Z
UID:10001246-1666866600-1666870200@cmsa.fas.harvard.edu
SUMMARY:Gravitational Wave\, Angular Momentum\, and Supertranslation Ambiguity
DESCRIPTION:General Relativity Seminar \n\nSpeaker: Naqing Xie (Fudan University) \nTitle: Gravitational Wave\, Angular Momentum\, and Supertranslation Ambiguity\n\nAbstract: The supertranslation ambiguity of angular momentum is a long-standing and conceptually important issue in general relativity. Recently\, there appeared the first definition of angular momentum at null infinity that is supertranslation invariant. However\, in the compact binary coalescence community\, supertranslation ambiguity is often ignored. We have shown that\, in the linearised theory of gravitational wave\, the new angular momentum coincides with the classical definition at the quadrupole level. This talk is based on a recent joint work with Xiaokai He and Xiaoning Wu.
URL:https://cmsa.fas.harvard.edu/event/gr_102722/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221028T093000
DTEND;TZID=America/New_York:20221028T103000
DTSTAMP:20260503T174143
CREATED:20230825T084953Z
LAST-MODIFIED:20240215T092925Z
UID:10001301-1666949400-1666953000@cmsa.fas.harvard.edu
SUMMARY:2-Categories and the Massive 3d A-Model
DESCRIPTION:Algebraic Geometry in String Theory Seminar \nSpeaker: Ahsan Khan\, IAS \nTitle: 2-Categories and the Massive 3d A-Model \nAbstract: I will outline the construction of a 2-category associated to a hyperKahler moment map. The construction is based on partial differential equations in one\, two\, and three dimensions combined with a three-dimensional version of the Gaiotto-Moore-Witten web formalism. \n 
URL:https://cmsa.fas.harvard.edu/event/agst-102822/
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-10.28.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221028T110000
DTEND;TZID=America/New_York:20221028T120000
DTSTAMP:20260503T174143
CREATED:20230809T110603Z
LAST-MODIFIED:20240301T080243Z
UID:10001227-1666954800-1666958400@cmsa.fas.harvard.edu
SUMMARY:Some non-concave dynamic optimization problems in finance
DESCRIPTION:Member Seminar \nSpeaker: Shuaijie Qian (Harvard CMSA) \nTitle: Some non-concave dynamic optimization problems in finance \nAbstract: Non-concave dynamic optimization problems appear in many areas of finance and economics. Most of existing literature solves these problems using the concavification principle\, and derives equivalent\, concave optimization problems whose value functions are still concave. In this talk\, I will present our recent work on some non-concave dynamic optimization problems\, where the concavification principle may not hold and the resulting value function is indeed non-concave. \nThe first work is about the portfolio selection model with capital gains tax and a bitcoin mining model with exit options and technology innovation\, where the average tax basis and the average mining cost serves as an approximation\, respectively. This approximation results in a non-concave value function\, and the associated HJB equation problem turns out to admit infinitely many solutions. We show that the value function is the minimal (viscosity) solution of the HJB equation problem. Moreover\, the penalty method still works and converges to the value function. \nThe second work is about a non-concave utility maximization problem with portfolio constraints. We find that adding bounded portfolio constraints\, which makes the concavification principle invalid\, can significantly affect economic insights in the existing literature. As the resulting value function is likely discontinuous\, we introduce a new definition of viscosity solution\, prove the corresponding comparison principle\, and show that a monotone\, stable\, and consistent finite difference scheme converges to the solution of the utility maximization problem. \n 
URL:https://cmsa.fas.harvard.edu/event/member-seminar-title-tba-6/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221101T090000
DTEND;TZID=America/New_York:20221101T103000
DTSTAMP:20260503T174143
CREATED:20240214T113716Z
LAST-MODIFIED:20240229T100642Z
UID:10002703-1667293200-1667298600@cmsa.fas.harvard.edu
SUMMARY:Kardar-Parisi-Zhang dynamics in integrable quantum magnets
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Francisco Machado  (Berkeley/Harvard) \nTitle: Kardar-Parisi-Zhang dynamics in integrable quantum magnets \nAbstract: Although the equations of motion that govern quantum mechanics are well-known\, understanding the emergent macroscopic behavior that arises from a particular set of microscopic interactions remains remarkably challenging. One particularly important behavior is that of hydrodynamical transport; when a quantum system has a conserved quantity (i.e. total spin)\, the late-time\, coarse-grained dynamics of the conserved charge is expected to follow a simple\, classical hydrodynamical description. However the nature and properties of this hydrodynamical description can depend on many details of the underlying interactions. For example\, the presence of additional dynamical constraints can fundamentally alter the propagation of the conserved quantity and induce slower-than-diffusion propagation. At the same time\, the presence of an extensive number of conserved quantities in the form of integrability\, can imbue the system with stable quasi-particles that propagate ballistically through the system. \nIn this talk\, I will discuss another possibility that arises from the interplay of integrability and symmetry; in integrable one dimensional quantum magnets with complex symmetries\, spin transport is neither ballistic nor diffusive\, but rather superdiffusive. Using a novel method for the simulation of quantum dynamics (termed Density Matrix Truncation)\, I will present a detailed analysis of spin transport in a variety of integrable quantum magnets with various symmetries. Crucially\, our analysis is not restricted to capturing the dynamical exponent of the transport dynamics and enables us to fully characterize its universality class: for all superdiffusive models\, we find that transport falls under the celebrated Kardar-Parisi-Zhang (KPZ) universality class. \nFinally\, I will discuss how modern atomic\, molecular and optical platforms provide an important bridge to connect the microscopic interactions to the resulting hydrodynamical transport dynamics. To this end\, I will present recent experimental results\, where this KPZ universal behavior was observed using atoms confined to an optical lattice. \n[1] Universal Kardar-Parisi-Zhang dynamics in integrable quantum systems\nB Ye†\, FM*\, J Kemp*\, RB Hutson\, NY Yao\n(PRL in press) – arXiv:2205.02853 \n[2] Quantum gas microscopy of Kardar-Parisi-Zhang superdiffusion\nD Wei\, A Rubio-Abadal\, B Ye\, FM\, J Kemp\, K Srakaew\, S Hollerith\, J Rui\, S Gopalakrishnan\, NY Yao\, I Bloch\, J Zeiher\nScience (2022) — arXiv:2107.00038 \n 
URL:https://cmsa.fas.harvard.edu/event/qm_11122/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Quantum-Matter-in-Mathematics-and-Physics-11.01.22_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221102T090000
DTEND;TZID=America/New_York:20221102T100000
DTSTAMP:20260503T174143
CREATED:20230705T074816Z
LAST-MODIFIED:20240215T092523Z
UID:10001137-1667379600-1667383200@cmsa.fas.harvard.edu
SUMMARY:Optical axion electrodynamics
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Junyeong Ahn (Harvard) \nTitle: Optical axion electrodynamics \nAbstract: Electromagnetic fields in a magneto-electric medium behave in close analogy to photons coupled to the hypothetical elementary particle\, the axion. This emergent axion electrodynamics is expected to provide novel ways to detect and control material properties with electromagnetic fields. Despite having been studied intensively for over a decade\, its theoretical understanding remains mostly confined to the static limit. Formulating axion electrodynamics at general optical frequencies requires resolving the difficulty of calculating optical magneto-electric coupling in periodic systems and demands a proper generalization of the axion field. In this talk\, I will introduce a theory of optical axion electrodynamics that allows for a simple quantitative analysis. Then\, I will move on to discuss the issue of the Kerr effect in axion antiferromagnets\, refuting the conventional wisdom that the Kerr effect is a measure of the net magnetic moment. Finally\, I will apply our theory to a topological antiferromagnet MnBi2Te4. \nReferences:\n[1] Theory of Optical Axion Electrodynamics\, J. Ahn\, S.Y. Xu\, A.Vishwanath\, arXiv:2205.06843
URL:https://cmsa.fas.harvard.edu/event/tqms_1122/
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-11.2.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221102T124500
DTEND;TZID=America/New_York:20221102T134500
DTSTAMP:20260503T174143
CREATED:20230817T174336Z
LAST-MODIFIED:20240121T174258Z
UID:10001270-1667393100-1667396700@cmsa.fas.harvard.edu
SUMMARY:Doping and inverting Mott insulators on semiconductor moire superlattices
DESCRIPTION:Speaker: Liang Fu (MIT) \n\n\nTitle: Doping and inverting Mott insulators on semiconductor moire superlattices \nAbstract: Semiconductor bilayer heterostructures provide a remarkable platform for simulating Hubbard models on an emergent lattice defined by moire potential minima. As a hallmark of Hubbard model physics\, the Mott insulator state with local magnetic moments has been observed at half filling of moire band. In this talk\, I will describe new phases of matter that grow out of the canonical 120-degree antiferromagnetic Mott insulator on the triangular lattice. First\, in an intermediate range of magnetic fields\, doping this Mott insulator gives rise to a dilute gas of spin polarons\, which form a pseudogap metal. Second\, the application of an electric field between the two layers can invert the many-body gap of a charge-transfer Mott insulator\, resulting in a continuous phase transition to a quantum anomalous Hall insulator with a chiral spin structure. Experimental results will be discussed and compared with theoretical predictions.
URL:https://cmsa.fas.harvard.edu/event/collquium-11222/
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-11.02.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221103T103000
DTEND;TZID=America/New_York:20221103T113000
DTSTAMP:20260503T174143
CREATED:20230817T180818Z
LAST-MODIFIED:20240209T063325Z
UID:10001247-1667471400-1667475000@cmsa.fas.harvard.edu
SUMMARY:Asymptotic geometry of null hypersurface in Schwarzschild spacetime and null Penrose inequality
DESCRIPTION:General Relativity Seminar \n\nSpeaker: Pengyu Le (BIMSA) \nTitle: Asymptotic geometry of null hypersurface in Schwarzschild spacetime and null Penrose inequality \nAbstract: Null Penrose inequality is an important case of the well-known Penrose inequality on a null hypersurface. It conjectures the relation between the area of the outmost marginally trapped surface and the Bondi mass at null infinity. Following the proposal of Christodoulou and Sauter\, we employ the perturbation method to study the asymptotic geometry of null hypersurfaces at null infinity in a perturbed vacuum Schwarzshild spacetime. We explain how to apply this perturbation theory to prove null Penrose inequality on a nearly spherically symmetric null hypersurface in a perturbed vacuum Schwarzschild spacetime.
URL:https://cmsa.fas.harvard.edu/event/gr_11322/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221103T130000
DTEND;TZID=America/New_York:20221103T140000
DTSTAMP:20260503T174143
CREATED:20230824T175654Z
LAST-MODIFIED:20240215T094755Z
UID:10001314-1667480400-1667484000@cmsa.fas.harvard.edu
SUMMARY:Force transmission informs the collective behavior of active cell layers
DESCRIPTION:Active Matter Seminar \nSpeaker: Siavash Monfared\, Niels Bohr Institute\, Copenhagen \nTitle: Force transmission informs the collective behavior of active cell layers \nAbstract: Collective cell migration drives numerous physiological processes such as tissue morphogenesis\, wound healing\, tumor progression and cancer invasion. However\, how the interplay of mechanical interactions and the modes of collective self-organization among cells informs such processes is yet to be established. In this talk\, I will focus on the role of three-dimensional force transmission\, from a theoretical and computational perspective\, on two phenomena: (1) cell extrusion from a cellular monolayer and (2) density-independent solid-like to fluid-like transition of active cell layers. For the first topic\, I will focus on how increasing cell-cell adhesion relative to cell-substrate adhesion enables cells to collectively exploit distinct mechanical pathways – leveraging defects in nematic and hexatic phases associated with cellular arrangement – to eliminate an unwanted cell. For the second topic\, I will show how solid-like to fluid-like transition in active cell layers is linked to the percolation of isotropic stresses. This is achieved via two distinct and independent paths to model this transition by increasing (a) cell-cell adhesion and (b) active traction forces. Additionally\, using finite-size scaling analyses\, the phase transition associated with each path is mapped onto the 2D site percolation universality class. Our results highlight the importance of force transmission in informing the collective behavior of living cells and opens the door to new sets of questions for those interested in connecting the physics of cellular self-organization to the dynamics of biological systems. \n 
URL:https://cmsa.fas.harvard.edu/event/am-113022/
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-11.03.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221107T110000
DTEND;TZID=America/New_York:20221107T120000
DTSTAMP:20260503T174143
CREATED:20230730T183933Z
LAST-MODIFIED:20240228T112123Z
UID:10001154-1667818800-1667822400@cmsa.fas.harvard.edu
SUMMARY:EFT strings and emergence
DESCRIPTION:Swampland Seminar \nSpeaker: Fernando Marchesano (IFT Madrid) \nTitle: EFT strings and emergence \nAbstract: We revisit the Emergence Proposal in 4d N=2 vector multiplet sectors that arise from  type II string Calabi-Yau compactifications\, with emphasis on the role of axionic fundamental strings\, or EFT strings. We focus on large-volume type IIA compactifications\, where EFT strings arise from NS5-branes wrapping internal four-cycles\, and consider a set of infinite-distance moduli-space limits that can be classified in terms of a scaling weight w=1\,2\,3. It has been shown before how one-loop threshold effects of an infinite tower of BPS particles made up of D2/D0-branes generate the asymptotic behaviour of  the gauge kinetic functions along limits with $w=3$. We extend this result to w=2 limits\, by taking into account D2-brane multi-wrapping numbers. In w=1 limits the leading tower involves EFT string oscillations\, and one can reproduce the behaviour of both weakly and strongly-coupled U(1)’s independently on whether the EFT string is critical or not\, by assuming that charged modes dominate the light spectrum.
URL:https://cmsa.fas.harvard.edu/event/swampland_102422-2/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221108T113000
DTEND;TZID=America/New_York:20221108T130000
DTSTAMP:20260503T174143
CREATED:20240214T113153Z
LAST-MODIFIED:20240229T100241Z
UID:10002699-1667907000-1667912400@cmsa.fas.harvard.edu
SUMMARY:Topological symmetry in field theory
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Daniel S. Freed (U Texas) \nTitle: Topological symmetry in field theory \nAbstract: Recently there has been lots of activity surrounding generalized notions of symmetry in quantum field theory\, including “categorical symmetries\,” “higher symmetries\,” “noninvertible symmetries\,” etc. Inspired by definitions of abstract (finite) groups and algebras and their linear actions\, we introduce a framework for these symmetries in field theory and a calculus of topological defects based on techniques in topological field theory. This is joint work with Constantin Teleman and Greg Moore. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_11822/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-11.08.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221109T093000
DTEND;TZID=America/New_York:20221109T110000
DTSTAMP:20260503T174143
CREATED:20230705T045400Z
LAST-MODIFIED:20250328T200129Z
UID:10000060-1667986200-1667991600@cmsa.fas.harvard.edu
SUMMARY:CMSA/Tsinghua Math-Science Literature Lecture: Large cardinals and small sets: The AD+ Duality Program
DESCRIPTION:CMSA/Tsinghua Math-Science Literature Lecture \n \nProf. Hugh Woodin will present a lecture in the CMSA/Tsinghua Math-Science Literature Lecture Series. \nDate: Wednesday\, November 9\, 2022 \nTime: 9:30 – 11:00 am ET \nLocation: Via Zoom Webinar and Room G10\, CMSA\, 20 Garden Street\, Cambridge MA 02138 \n  \nTitle: Large cardinals and small sets: The AD+ Duality Program \nAbstract: The determinacy axiom\, AD\, was introduced by Mycielski and Steinhaus over 60 years ago as an alternative to the Axiom of Choice for the study of arbitrary sets of real numbers.  The modern view is that determinacy axioms concern generalizations of the borel sets\, and deep connections with large cardinal axioms have emerged. \nThe study of determinacy axioms has led to a specific technical refinement of AD\, this is the axiom AD+. The further connections with large axioms have in turn implicitly led to a duality program\, this is the AD+ Duality Program. \nThe main open problems here are intertwined with those of the Inner Model Program\, which is the central program in the study of large cardinal axioms. \nThis has now all been distilled into a series of specific conjectures. \n  \nTalk chair: Horng-Tzer Yau (Harvard Mathematics & CMSA) \nModerator: Alejandro Poveda Ruzafa (Harvard CMSA) \n  \nBeginning in Spring 2020\, the CMSA began hosting a lecture series on literature in the mathematical sciences\, with a focus on significant developments in mathematics that have influenced the discipline\, and the lifetime accomplishments of significant scholars. \n  \nCMSA COVID-19 Policies
URL:https://cmsa.fas.harvard.edu/event/math-science-literature-lecture/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Math Science Literature Lecture Series,Public Lecture,Special Lectures
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/Mathlit_WOODIN.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221109T153000
DTEND;TZID=America/New_York:20221109T163000
DTSTAMP:20260503T174143
CREATED:20230802T172421Z
LAST-MODIFIED:20240110T075312Z
UID:10001184-1668007800-1668011400@cmsa.fas.harvard.edu
SUMMARY:Liouville quantum gravity from random matrix dynamics
DESCRIPTION:Probability Seminar \nSpeaker: Hugo Falconet (Courant Institute\, NYU) \nTitle: Liouville quantum gravity from random matrix dynamics \nAbstract: The Liouville quantum gravity measure is a properly renormalized exponential of the 2d GFF. In this talk\, I will explain how it appears as a limit of natural random matrix dynamics: if (U_t) is a Brownian motion on the unitary group at equilibrium\, then the measures $|det(U_t – e^{i theta}|^gamma dt dtheta$ converge to the 2d LQG measure with parameter $gamma$\, in the limit of large dimension. This extends results from Webb\, Nikula and Saksman for fixed time. The proof relies on a new method for Fisher-Hartwig asymptotics of Toeplitz determinants with real symbols\, which extends to multi-time settings. I will explain this method and how to obtain multi-time loop equations by stochastic analysis on Lie groups. \nBased on a joint work with Paul Bourgade. \n 
URL:https://cmsa.fas.harvard.edu/event/probability-11922/
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-11.09.22-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221110T093000
DTEND;TZID=America/New_York:20221110T103000
DTSTAMP:20260503T174143
CREATED:20230817T181337Z
LAST-MODIFIED:20240118T090553Z
UID:10001248-1668072600-1668076200@cmsa.fas.harvard.edu
SUMMARY:Schwarzschild-like Topological Solitons in Gravity
DESCRIPTION:General Relativity Seminar \n\nSpeaker: Pierre Heidmann (Johns Hopkins) \nTitle: Schwarzschild-like Topological Solitons in Gravity \nAbstract: We present large classes of non-extremal solitons in gravity that are asymptotic to four-dimensional Minkowski spacetime plus extra compact dimensions. They correspond to smooth horizonless geometries induced by topology in spacetime and supported by electromagnetic flux\, which characterize coherent states of quantum gravity. We discuss a new approach to deal with Einstein-Maxwell equations in more than four dimensions\, such that they decompose into a set of Ernst equations. We generate the solitons by applying different techniques associated with the Ernst formalism. We focus on solitons with zero net charge yet supported by flux\, and compare them to Schwarzschild black holes. These are also ultra-compact geometries with very high redshift but differ in many aspects. At the end of the talk\, we discuss the stability properties of the solitons and their gravitational signatures.
URL:https://cmsa.fas.harvard.edu/event/gr_111022/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.10.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221111T110000
DTEND;TZID=America/New_York:20221111T120000
DTSTAMP:20260503T174143
CREATED:20230809T111328Z
LAST-MODIFIED:20240209T052938Z
UID:10001228-1668164400-1668168000@cmsa.fas.harvard.edu
SUMMARY:Quantum trace and length conjecture for hyperbolic knot
DESCRIPTION:Member Seminar \nSpeaker: Mauricio Romo \nTitle: Quantum trace and length conjecture for hyperbolic knot \nAbstract: I will define the quantum trace map for an ideally triangulated hyperbolic knot complement on S^3. This map assigns an operator to each element L of  the Kauffman Skein module of knot complement.  Motivated by an interpretation of this operator in the context of SL(2\,C) Chern-Simons theory\, one can formulate a ‘length conjecture’ for the hyperbolic length of L.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-111122/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221115T093000
DTEND;TZID=America/New_York:20221115T110000
DTSTAMP:20260503T174143
CREATED:20240229T095854Z
LAST-MODIFIED:20240229T095854Z
UID:10002884-1668504600-1668510000@cmsa.fas.harvard.edu
SUMMARY:Topology of the Fermi sea: Ordinary metals as topological materials
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Pok Man Tam (University of Pennsylvania) \nTitle: Topology of the Fermi sea: Ordinary metals as topological materials \nAbstract: It has long been known that the quantum ground state of a metal is characterized by an abstract manifold in momentum space called the Fermi sea. Fermi sea can be distinguished topologically in much the same way that a ball can be distinguished from a donut by counting the number of holes. The associated topological invariant\, i.e. the Euler characteristic (χ_F)\, serves to classify metals. Here I will survey two recent proposals relating χ_F  to experimental observables\, namely: (i) equal-time density/number correlations [1]\, and (ii) Andreev state transport along a planar Josephson junction [2]. Moreover\, from the perspective of quantum information\, I will explain how multipartite entanglement in real space probes the Fermi sea topology in momentum space [1]. Our works not only provide a new connection between topology and entanglement in gapless quantum matters\, but also suggest accessible experimental platforms to extract the topology in metals. \n[1] P. M. Tam\, M. Claassen\, C. L. Kane\, Phys. Rev. X 12\, 031022 (2022) \n[2] P. M. Tam and C. L. Kane\, arXiv:2210.08048 \n 
URL:https://cmsa.fas.harvard.edu/event/qm_tba-7/
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-11.15.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221115T110000
DTEND;TZID=America/New_York:20221115T120000
DTSTAMP:20260503T174143
CREATED:20230730T184327Z
LAST-MODIFIED:20240228T111805Z
UID:10001155-1668510000-1668513600@cmsa.fas.harvard.edu
SUMMARY:The Emergence Proposal in Quantum Gravity and the Species Scale
DESCRIPTION:Swampland Seminar \nSpeaker: Alvaro Herraez (Saclay) \nTitle: The Emergence Proposal in Quantum Gravity and the Species Scale \nAbstract: The Emergence Proposal claims that in Quantum Gravity the kinetic terms of the fields in the IR emerge from integrating out (infinite) towers of particles up to the QG cutoff. After introducing this proposal in the context of the Swampland Program\, I will explain why it is natural to identify this QG cutoff with the Species Scale\, motivating it by direct computation in the presence of the relevant towers. Then\, I will present evidence for this proposal by directly studying how it is realized in different string theory setups\, where the kinetic terms of scalars\, p-forms and even scalar potentials can be shown to emerge after integrating out such towers. \n  \n 
URL:https://cmsa.fas.harvard.edu/event/swampland_111522/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Swampland Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Swampland-Seminar-11.15.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221116T100000
DTEND;TZID=America/New_York:20221116T113000
DTSTAMP:20260503T174143
CREATED:20230705T075111Z
LAST-MODIFIED:20240216T092731Z
UID:10001136-1668592800-1668598200@cmsa.fas.harvard.edu
SUMMARY:Vacuum fluctuations in cavities: breakdown of the topological protection in the integer Quantum Hall effect
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Jérôme Faist  (ETH Zurich) \nTitle: Vacuum fluctuations in cavities: breakdown of the topological protection in the integer Quantum Hall effect \nAbstract: When a collection of electronic excitations are strongly coupled to a single mode cavity\, mixed light-matter excitations called polaritons are created. The situation is especially interesting when the strength of the light-matter coupling ΩR is such that the coupling energy becomes close to the one of the bare matter resonance ω0. For this value of parameters\, the system enters the so-called ultra-strong coupling regime\, in which a number of very interesting physical effects were predicted caused by the counter-rotating and diamagnetic terms of the Hamiltonian. \nIn a microcavity\, the strength of the electric field caused by the vacuum fluctuations\, to which the strength of the light-matter coupling ΩR is proportional\, scales inversely with the cavity volume. One very interesting feature of the circuit-based metamaterials is the fact that this volume can be scaled down to deep subwavelength values in all three dimension of space.1 Using metamaterial coupled to two-dimensional electron gases under a strong applied magnetic field\, we have now explored to which extend this volume can be scaled down and reached a regime where the stability of the polariton is limited by diffraction into a continuum of plasmon modes2. \nWe have also used transport to probe the ultra-strong light-matter coupling3\, and show now that the latter can induce a breakdown of the integer quantum Hall effect4. The phenomenon is explained in terms of cavity-assisted hopping\, an anti-resonant process where an electron can scatter from one edge of the sample to the other by “borrowing” a photon from the cavity5. We are also evaluating a proposal suggesting that the value of the quantization voltage can be renormalized by the cavity6. \n  \n\nScalari\, G. et al. Ultrastrong Coupling of the Cyclotron Transition of a 2D Electron Gas to a THz Metamaterial. Science 335\, 1323–1326 (2012).\nRajabali\, S. et al. Polaritonic Nonlocality in Light Matter Interaction. Nat Photon 15\, 690–695 (2021).\nParavicini-Bagliani\, G. L. et al. Magneto-Transport Controlled by Landau Polariton States. Nat. Phys. 15\, 186–190 (2019).\nAppugliese\, F. et al. Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect. Science 375\, 1030–1034 (2022).\nCiuti\, C. Cavity-mediated electron hopping in disordered quantum Hall systems. Phys. Rev. B 104\, 155307 (2021).\nRokaj\, V.\, Penz\, M.\, Sentef\, M. A.\, Ruggenthaler\, M. & Rubio\, A. Polaritonic Hofstadter butterfly and cavity control of the quantized Hall conductance. Phys. Rev. B 105\, 205424 (2022).\n\n 
URL:https://cmsa.fas.harvard.edu/event/tqms_111622/
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-11.16.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221116T123000
DTEND;TZID=America/New_York:20221116T133000
DTSTAMP:20260503T174143
CREATED:20230817T174642Z
LAST-MODIFIED:20240214T112838Z
UID:10001271-1668601800-1668605400@cmsa.fas.harvard.edu
SUMMARY:Noether’s Learning Dynamics: Role of Symmetry Breaking in Neural Networks
DESCRIPTION:Colloquium \nSpeaker: Hidenori Tanaka (NTT Research at Harvard) \nTitle: Noether’s Learning Dynamics: Role of Symmetry Breaking in Neural Networks \nAbstract: In nature\, symmetry governs regularities\, while symmetry breaking brings texture. In artificial neural networks\, symmetry has been a central design principle\, but the role of symmetry breaking is not well understood. Here\, we develop a Lagrangian formulation to study the geometry of learning dynamics in neural networks and reveal a key mechanism of explicit symmetry breaking behind the efficiency and stability of modern neural networks. Then\, we generalize Noether’s theorem known in physics to describe a unique symmetry breaking mechanism in learning and derive the resulting motion of the Noether charge: Noether’s Learning Dynamics (NLD). Finally\, we apply NLD to neural networks with normalization layers and discuss practical insights. Overall\, through the lens of Lagrangian mechanics\, we have established a theoretical foundation to discover geometric design principles for the learning dynamics of neural networks.
URL:https://cmsa.fas.harvard.edu/event/collquium-111622/
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-11.16.22-2.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221116T153000
DTEND;TZID=America/New_York:20221116T163000
DTSTAMP:20260503T174143
CREATED:20230802T172705Z
LAST-MODIFIED:20240110T084219Z
UID:10001185-1668612600-1668616200@cmsa.fas.harvard.edu
SUMMARY:Outlier-Robust Algorithms for Clustering Non-Spherical Mixtures
DESCRIPTION:Probability Seminar \n\nSpeaker: Ainesh Bakshi (MIT) \nTitle: Outlier-Robust Algorithms for Clustering Non-Spherical Mixtures \nAbstract: In this talk\, we describe the first polynomial time algorithm for robustly clustering a mixture of statistically-separated\, high-dimensional Gaussians. Prior to our work this question was open even in the special case of 2 components in the mixture. Our main conceptual contribution is distilling analytic properties of distributions\, namely hyper-contractivity of degree-two polynomials and anti-concentration of linear projections\, which are necessary and sufficient for clustering.
URL:https://cmsa.fas.harvard.edu/event/probability-111622/
CATEGORIES:Probability Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Probability-Seminar-11.16.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221117T093000
DTEND;TZID=America/New_York:20221117T103000
DTSTAMP:20260503T174143
CREATED:20230817T181725Z
LAST-MODIFIED:20240118T090857Z
UID:10001249-1668677400-1668681000@cmsa.fas.harvard.edu
SUMMARY:Ringdown and geometry of trapping for black holes
DESCRIPTION:General Relativity Seminar \n\nSpeaker: Semyon Dyatlov (MIT) \nTitle: Ringdown and geometry of trapping for black holes \nAbstract: Quasi-normal modes are complex exponential frequencies appearing in long time expansions of solutions to linear wave equations on black hole backgrounds. They appear in particular during the ringdown phase of a black hole merger when the dynamics is expected to be driven by linear effects. In this talk I give an overview of various results in pure mathematics which relate asymptotic behavior of quasi-normal modes at high frequency to the geometry of the set of trapped null geodesics\, such as the photon sphere in Schwarzschild (-de Sitter). These trapped geodesics have two kinds of behavior: the geodesic flow is hyperbolic in directions normal to the trapped set (a feature stable under perturbations) and it is completely integrable on the trapped set. It turns out that normal hyperbolicity gives information about the rate of decay of quasi-normal modes\, while complete integrability gives rise to a quantization condition.
URL:https://cmsa.fas.harvard.edu/event/gr_111722/
LOCATION:Hybrid
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.17.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221117T130000
DTEND;TZID=America/New_York:20221117T140000
DTSTAMP:20260503T174143
CREATED:20230824T175941Z
LAST-MODIFIED:20240122T172011Z
UID:10001315-1668690000-1668693600@cmsa.fas.harvard.edu
SUMMARY:Dynamic and multicolor electron microscopy
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Max Prigozhin (Harvard) \nTitle: Dynamic and multicolor electron microscopy \nAbstract: My lab is developing biophysical methods to achieve multicolor and dynamic biological imaging at the molecular scale. Our approach to capturing the dynamics of cellular processes involves cryo-vitrifying samples after known time delays following stimulation using custom cryo- plunging and high-pressure freezing instruments. To achieve multicolor electron imaging\, we are exploring the property of cathodoluminescence—optical emission induced by the electron beam. We are developing nanoprobes (“cathodophores”) that will be used as luminescent protein tags in electron microscopy. We are applying these new methods to study G-protein- coupled receptor signaling and to visualize the formation of biomolecular condensates.
URL:https://cmsa.fas.harvard.edu/event/am-111722/
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-11.17.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221118T110000
DTEND;TZID=America/New_York:20221118T120000
DTSTAMP:20260503T174143
CREATED:20230809T111725Z
LAST-MODIFIED:20240209T052933Z
UID:10001229-1668769200-1668772800@cmsa.fas.harvard.edu
SUMMARY:Light states in the interior of CY moduli spaces
DESCRIPTION:Member Seminar \nSpeaker: Damian van de Heisteeg \nTitle: Light states in the interior of CY moduli spaces \nAbstract: In string theory one finds that states become massless as one approaches boundaries in Calabi-Yau moduli spaces. In this talk we look in the opposite direction\, that is\, we search for points where the mass gap for these light states is maximized — the so-called desert. In explicit examples we identify these desert points\, and find that they correspond to special points in the moduli space of the CY\, such as orbifold points and rank two attractors.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-111822/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-11.18.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221122T093000
DTEND;TZID=America/New_York:20221122T110000
DTSTAMP:20260503T174143
CREATED:20240215T100358Z
LAST-MODIFIED:20240819T145840Z
UID:10002736-1669109400-1669114800@cmsa.fas.harvard.edu
SUMMARY:3D gravity and gravitational entanglement entropy
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Gabriel Wong (Harvard CMSA) \nTitle: 3D gravity and gravitational entanglement entropy \nAbstract: Recent progress in AdS/CFT has provided a good understanding of how the bulk spacetime is encoded in the entanglement structure of the boundary CFT. However\, little is known about how spacetime emerges directly from the bulk quantum theory. We address this question in an effective 3d quantum theory of pure gravity\, which describes the high temperature regime of a holographic CFT.  This theory can be viewed as a $q$-deformation and dimensional uplift of JT gravity. Using this model\, we show that the Bekenstein-Hawking entropy of a two-sided black hole equals the bulk entanglement entropy of gravitational edge modes. These edge modes transform under a quantum group\, which defines the data associated to an extended topological quantum field theory. Our calculation suggests an effective description of bulk microstates in terms of collective\, anyonic degrees of freedom whose entanglement leads to the emergence of the bulk spacetime. Finally\, we give a proposal for obtaining the Ryu Takayanagi formula using the same quantum group edge modes. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_112222/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-Seminar-11.22.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20221123T090000
DTEND;TZID=America/New_York:20221123T100000
DTSTAMP:20260503T174143
CREATED:20230705T075447Z
LAST-MODIFIED:20240216T092538Z
UID:10001135-1669194000-1669197600@cmsa.fas.harvard.edu
SUMMARY:Continuum field theory of graphene bilayer system
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Jian Kang\, School of Physical Science and Technology\, ShanghaiTech University\, Shanghai\, China \nTitle: Continuum field theory of graphene bilayer system \nAbstract: The Bistritzer-MacDonald (BM) model predicted the existence of the narrow bands in the magic-angle twisted bilayer graphene (MATBG)\, and nowadays is a starting point for most theoretical works. In this talk\, I will briefly review the BM model and then present a continuum field theory [1] for graphene bilayer system allowing any smooth lattice deformation including the small twist angle. With the gradient expansion to the second order\, the continuum theory for MATBG [2] produces the spectrum that almost perfectly matches the spectrum of the microscopic model\, suggesting the validity of this theory. In the presence of the lattice deformation\, the inclusion of the pseudo-vector potential does not destroy but shift the flat band chiral limit to a smaller twist angle. Furthermore\, the continuum theory contains another important interlayer tunneling term that was overlooked in all previous works. This term non-negligibly breaks the particle-hole symmetry of the narrow bands and may be related with the experimentally observed particle-hole asymmetry. \n1. O. Vafek and JK\, arXiv: 2208.05933.\n2. JK and O. Vafek\, arXiv: 2208.05953. \n 
URL:https://cmsa.fas.harvard.edu/event/tqms_112322/
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-11.23.22.png
END:VEVENT
END:VCALENDAR