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DTSTART;TZID=America/New_York:20190912T143000
DTEND;TZID=America/New_York:20190912T160000
DTSTAMP:20240212T095136Z
CREATED:20240212T095136Z
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UID:10001937-1568298600-1568304000@cmsa.fas.harvard.edu
SUMMARY:9/12/2019 Spacetime Seminar
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/9-12-2019-spacetime-seminar/
LOCATION:MA
CATEGORIES:Colloquia & Seminar,Seminars
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DTSTART;TZID=America/New_York:20190912T173800
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DTSTAMP:20240213T102851Z
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UID:10002429-1568309880-1568309880@cmsa.fas.harvard.edu
SUMMARY:Spacetime and Quantum Mechanics Seminar
DESCRIPTION:As part of the program on Spacetime and Quantum Mechanics\, the CMSA will be hosting a weekly seminar on Thursdays at 2:30pm in room G10. \n\n\n\nDate\nSpeaker\nTitle/Abstract\n\n\n9/12/2019\nPasha Pylyavskyy (University of Minnesota)\nTitle: Vector-relation configurations and plabic graphs\n\n\n19/18/2019 \n2:00pm \nG02\nFrancis Brown (University of Oxford)\nTitle: Amplitudes\, Polylogs and Moduli Spaces\n\n\n9/19/2019\nChuck Doran (University of Alberta)\nTitle: Calabi-Yau geometry of the N-loop sunset Feynman integrals \nAbstract: I will present an overview of the algebraic and transcendental features of the computation of N-loop sunset Feynman integrals. \nStarting from the realization of arbitrary Feynman graph hypersurfaces as (generalized) determinantal varieties\, we describe the Calabi-Yau subvarieties of permutohedral varieties that arise from the N-loop sunset Feynman graphs and some key features of their geometry and moduli. \nThese include: (1) an iterated fibration structure which allows one to “bootstrap” both periods and Picard-Fuchs equations from lower N cases; (2) specialization to and interpretation of coincident mass loci (“jump loci”) in moduli; (3) a significant generalization of the Griffiths-Dwork algorithm via “creative telescoping”; and (4) the realization of Calabi-Yau pencils as Landau-Ginzburg models mirror to weak Fano varieties. \nDetails of each of these will be discussed in later lectures this semester. This is joint work with Pierre Vanhove and Andrey Novoseltsev.\n\n\n9/26/2019\nTomasz Taylor (Northeastern)\nTitle: Celestial Amplitudes\n\n\n10/3/2019\nSimon Caron-Huot (McGill)\nTitle: Poincare Duals of Feynman Integrals\n\n\n10/10/2019 \n3:30pm\nYutin Huang (National Taiwan University)\nTitle: Dualities of Planar Ising Networks and the Positive Orthogonal Grassmannian\n\n\n10/15/2019 \nTuesday \n3:30pm\n  \nSergey Fomin (Univ. of Michigan) \n \nTitle: “Morsifications and mutations” (joint work with P. Pylyavskyy\, E. Shustin\, and D. Thurston). \n\n\n10/18/2019 \nFriday  \nG02\nSebastian Franco (The City College of New York)\nTitle: Graded quivers\, generalized dimer models\, and topic geometry\n\n\n10/31/2019\nJunjie Rao (Albert Einstein Institute)\nTitle: All-loop Mondrian Reduction of 4-particle Amplituhedron at Positive Infinity\n\n\n11/1/2019 \nSC 232 \n1:30pm\nGeorge Lusztig (MIT)\nTitle: Total positivity in Springer fibres\n\n\n11/12/2019 \nTuesday \nG02 \n3:30pm\n  \nPierpaolo Mastrolia (University of Padova)\nTitle: Feynman Integrals and Intersection Theory\n\n\n11/14/2019 \nG02\nPierpaolo Mastrolia (University of Padova)\nTitle: Feynman Integrals and Intersection Theory Pt. II\n\n\n11/21/2019\nCristian Vergu (Niels Bohr Institute)\nTitle: The Octagonal Alphabet\n\n\n11/26/2019\nStephan Stieberger (IAS)\nTitle: Strings on the Celestial Sphere\n\n\n12/4/2019\nHadleigh Frost (Oxford)\nTitle: BCJ numerators\, $\mathcal{M}_{0\,n}$\, and ABHY \nAbstract: We relate the BCJ numerator Jacobi property to the classical fact that the top homology group of $\mathcal{M}_{0\,n}$ is isomorphic to a component of the free Lie algebra. We describe ways to get BCJ numerators\, and caution that the BCJ Jacobi property doesn’t imply the existence of what has been called a ‘kinematic algebra.’\n\n\n 12/5/2019\nDavid Kosower (IAS)\nTitle: From scattering amplitudes to classical observables\n\n\n12/10/2019\nRamis Movassagh (MIT)\nTitle: Highly entangled quantum spin chains: Exactly solvable counter-examples to the area law \nAbstract: In recent years\, there has been a surge of activities in proposing “exactly solvable” quantum spin chains with surprising high amount of ground state entanglement–exponentially more than the critical systems that have $\log(n)$ von Neumann entropy. We discuss these models from first principles. For a spin chain of length $n$\, we prove that the ground state entanglement entropy scales as $\sqrt(n)$ and in some cases even extensive (i.e.\, as $n$) despite the underlying Hamiltonian being: (1) Local (2) Having a unique ground state and (3) Translationally invariant in the bulk. These models have rich connections with combinatorics\, random walks\, Markov chains\, and universality of Brownian excursions. Lastly\, we develop techniques for proving the gap. As a consequence\, the gap of Motzkin and Fredkin spin chains are proved to vanish as 1/n^c with c>2; this rules out the possibility of these models to be relativistic conformal field theories in the continuum limit. Time permitting we will discuss more recent developments in this direction and ‘generic’ aspects of local spin chains.
URL:https://cmsa.fas.harvard.edu/event/spacetime-and-quantum-mechanics-seminar/
LOCATION:MA
CATEGORIES:Seminars
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