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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241210T110000
DTEND;TZID=America/New_York:20241210T120000
DTSTAMP:20260414T090704
CREATED:20240903T181118Z
LAST-MODIFIED:20241210T202435Z
UID:10003419-1733828400-1733832000@cmsa.fas.harvard.edu
SUMMARY:The Einstein-Vlasov system in a large data regime
DESCRIPTION:General Relativity Seminar \nSpeaker: Nikolaos Athanasiou\, University of Crete\, Greece \nTitle: The Einstein-Vlasov system in a large data regime \nAbstract: In this talk\, our object of study is the Einstein-Vlasov system with a massless Vlasov matter field. Complementing various important works obtaining the stability of Minkowski spacetime as a solution to this system\, we look at the large data regime\, motivated in turn by the signature for decay rates of various Ricci\, curvature and matter components\, first introduced by X. An. Our work provides a semi-global existence result and a trapped surface formation result for the Einstein-Vlasov system in the absence of spherical symmetry. Our proof is based on a double null gauge. Interestingly\, we give a new way of obtaining estimates for the Vlasov matter\, purely by commuting with various vector fields and without the need to use Jacobi fields.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-121024/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-12.10.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241210T093000
DTEND;TZID=America/New_York:20241210T110000
DTSTAMP:20260414T090704
CREATED:20250123T201841Z
LAST-MODIFIED:20250123T202831Z
UID:10003669-1733823000-1733828400@cmsa.fas.harvard.edu
SUMMARY:Quantum Effects Inside Black Holes
DESCRIPTION:Joint CMSA/BHI Foundation Seminar \nLocation: BHI seminar room \n\nSpeaker: Noa Zilberman\, Princeton \nTitle: Quantum Effects Inside Black Holes \n\n\nAbstract: Astrophysical black holes are known to be rotating. Within classical General Relativity\, the simplest spacetime solution (the Kerr solution) describing a rotating black hole reveals a traversable passage through an inner horizon – which in turn may lead to another external universe. But does this remain the case when taking quantum effects into account? \nAnswering this question\, along others\, requires one to understand the manner in which quantum energy fluxes affect the internal geometry of a black hole. It has been widely anticipated\, yet inconclusive (till this work)\, that such effects would diverge at the inner horizon of a spinning black hole. This divergence\, if indeed takes place\, may drastically affect the internal black hole geometry\, potentially preventing the inner horizon traversability. Clarifying this issue requires the computation of the quantum energy fluxes in black hole interiors. However\, this has been a serious challenge for decades. \nUsing a combination of old and new methods\, we have managed to compute the quantum energy fluxes at the inner horizon of a spinning black hole\, in a vacuum state corresponding to an evaporating black hole. We found that these fluxes are either positive or negative\, depending on the black hole spin (and polar angle). The sign of these fluxes may be crucial to the nature of their backreaction on the geometry (as should be dictated by the semiclassical Einstein equation). \nIn this seminar\, we shall briefly describe the basic framework of semiclassical general relativity and the renormalization procedure\, and then present our novel results for the quantum fluxes at the inner horizon of a rotating black hole\, briefly mentioning possible implications for the inner horizon traversability.
URL:https://cmsa.fas.harvard.edu/event/foundation_21025/
LOCATION:Black Hole Initiative\, 20 Garden Street\, Cambridge MA\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241203T110000
DTEND;TZID=America/New_York:20241203T120000
DTSTAMP:20260414T090704
CREATED:20240903T192215Z
LAST-MODIFIED:20241125T194606Z
UID:10003429-1733223600-1733227200@cmsa.fas.harvard.edu
SUMMARY:Mass for the large and for the small
DESCRIPTION:General Relativity Seminar \nSpeaker: Tin Yau Tsang\, Courant Institute\, New York University \nTitle: Mass for the large and for the small\n\nAbstract: Seeking a meaningful geometric (physical) invariant to describe a spacetime has sparked research in both mathematics and physics. In this talk\, we will first see the fundamental progress made by Schoen-Yau and Witten on ADM (Arnowitt-Deser-Misner) mass. Then\, we will see the progress on quasilocal masses in recent years. In particular\, we would discuss the Hamiltonian formulation and the behaviour of quasilocal masses with the presence of apparent horizons.\n  \n 
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-12324/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-12.3.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241125T093000
DTEND;TZID=America/New_York:20241125T110000
DTSTAMP:20260414T090704
CREATED:20241017T184932Z
LAST-MODIFIED:20241122T152145Z
UID:10003615-1732527000-1732532400@cmsa.fas.harvard.edu
SUMMARY:Foundation Seminar
DESCRIPTION:Foundation Seminar (Joint Seminar with BHI) \n\nTitle: Searching for Dark Matter in the Sky \nAbstract: Astrophysical and cosmological observations have allowed us to measure the abundance of dark matter and have provided important information on its properties. I will discuss past\, present and future efforts to map the gravitational footprint of dark matter throughout the cosmos\, and what such studies can (and cannot) tell us about dark matter’s fundamental nature. I will also review how even tiny non-gravitational interactions of dark and visible matter could lead to a range of “indirect detection” signals\, and outline the status and prospects of searches for such signals\, with a focus on the next decade or so.
URL:https://cmsa.fas.harvard.edu/event/foundation-seminar_112524/
LOCATION:Black Hole Initiative\, 20 Garden Street\, Cambridge MA\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/11.25.24_Tracy-Slatyer_Joint-CMSA-Template-Real-Estate-Flyer-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241119T110000
DTEND;TZID=America/New_York:20241119T120000
DTSTAMP:20260414T090704
CREATED:20240903T181051Z
LAST-MODIFIED:20241115T150935Z
UID:10003418-1732014000-1732017600@cmsa.fas.harvard.edu
SUMMARY:The Einstein-Euler system with a physical vacuum boundary in spherical symmetry
DESCRIPTION:General Relativity Seminar \nSpeaker: Marcelo Disconzi\, Vanderbilt University \nTitle: The Einstein-Euler system with a physical vacuum boundary in spherical symmetry \nAbstract: We establish local well-posedness for the Einstein-Euler system with a physical vacuum boundary in spherical symmetry. Our proof relies on a new way of thinking about Einstein’s equations in spherical symmetry that is well-adapted to the fluid’s characteristics on the free boundary. We also exploit the Einstein constraint equations in spherical symmetry in a new way\, as a tool to understand the evolution problem. This is joint work with Jared Speck.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-111924/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.19.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241112T110000
DTEND;TZID=America/New_York:20241112T120000
DTSTAMP:20260414T090704
CREATED:20240903T192017Z
LAST-MODIFIED:20241107T211753Z
UID:10003427-1731409200-1731412800@cmsa.fas.harvard.edu
SUMMARY:pp Waves: Quasinormal Modes & Hidden Symmetries of Black Holes
DESCRIPTION:General Relativity Seminar \nSpeaker: Ahmed Seta\, Harvard University \nTitle: pp Waves: Quasinormal Modes & Hidden Symmetries of Black Holes \nAbstract: The spectrum of quasinormal modes of 4D flat space black holes is not analytically tractable\, but there are two asymptotic limits where the QNM spectrum is under control: weak damping and strong damping. In this talk\, I will explain how these asymptotic QNMs are controlled by dynamical symmetries of the wave equation in certain kinematic limits.  These two asymptotic limits are\, in turn\, captured by the two classes of bound null geodesics in the black hole geometry: the photon ring and the horizon. I will also discuss the Penrose limit: a scaling limit into the geometry experienced by these geodesics\, which results in a plane-wave spacetime where the dynamical symmetries get enhanced into isometries.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-111224/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.12.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241104T093000
DTEND;TZID=America/New_York:20241104T103000
DTSTAMP:20260414T090704
CREATED:20240918T132254Z
LAST-MODIFIED:20241104T150620Z
UID:10003519-1730712600-1730716200@cmsa.fas.harvard.edu
SUMMARY:Foundation Seminar
DESCRIPTION:Foundation Seminar (Joint Seminar with BHI) \nLocation: BHI\n\nSpeaker: Christoph Kehle (MIT)\n\nTitle: On the cosmic censorship conjectures\nAbstract: I will present the modern formulations of the weak and strong cosmic censorship conjectures and discuss some recent developments in the context of gravitational collapse.
URL:https://cmsa.fas.harvard.edu/event/foundation-seminar_11424/
LOCATION:Black Hole Initiative\, 20 Garden Street\, Cambridge MA\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241029T110000
DTEND;TZID=America/New_York:20241029T120000
DTSTAMP:20260414T090704
CREATED:20240903T183326Z
LAST-MODIFIED:20241026T192248Z
UID:10003425-1730199600-1730203200@cmsa.fas.harvard.edu
SUMMARY:Formation of Trapped Surfaces in Geodesic Foliation
DESCRIPTION:General Relativity Seminar \nSpeaker: Xuantao Chen\, Johns Hopkins University \nTitle: Formation of Trapped Surfaces in Geodesic Foliation \nAbstract: We reprove the formation of trapped surfaces for the Einstein vacuum equation using the incoming geodesic foliation. All previous results\, starting with the seminal work of Christodoulou\, make use of the double null foliation. In the new proof\, all Ricci coefficients are estimated by transport equations in the incoming null direction\, and the incoming initial data is only used in the curvature (energy) estimates. The result is based on a version of the non-integrable PT frame\, which was introduced in the proof of Kerr stability with small angular momentum. \n 
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-102224/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-10.29.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241028T093000
DTEND;TZID=America/New_York:20241028T103000
DTSTAMP:20260414T090704
CREATED:20240918T132207Z
LAST-MODIFIED:20241018T172052Z
UID:10003518-1730107800-1730111400@cmsa.fas.harvard.edu
SUMMARY:Foundation Seminar: Singularity Theorems\, Part II
DESCRIPTION:Foundation Seminar (Joint Seminar with BHI) \nLocation: BHI \nTitle: Singularity Theorems\, Part II \nJournal Club Discussion
URL:https://cmsa.fas.harvard.edu/event/foundation-seminar_102824/
LOCATION:20 Garden Street\, Cambridge\, MA 02138\, MA\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241021T093000
DTEND;TZID=America/New_York:20241021T103000
DTSTAMP:20260414T090704
CREATED:20240907T155707Z
LAST-MODIFIED:20241018T171738Z
UID:10003446-1729503000-1729506600@cmsa.fas.harvard.edu
SUMMARY:Foundation Seminar: Singularity Theorems\, Part I
DESCRIPTION:Foundation Seminar (Joint Seminar with BHI) \nLocation: BHI \nTitle: Singularity Theorems\, Part I \nJournal Club Discussion
URL:https://cmsa.fas.harvard.edu/event/foundation-seminar_102124/
LOCATION:Black Hole Initiative\, 20 Garden Street\, Cambridge MA\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/10.28.24_Singularity-Theorems-Part-II-4.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241015T110000
DTEND;TZID=America/New_York:20241015T120000
DTSTAMP:20260414T090704
CREATED:20240903T183238Z
LAST-MODIFIED:20241010T180340Z
UID:10003424-1728990000-1728993600@cmsa.fas.harvard.edu
SUMMARY:Gravitational collapse to extremal Reissner-Nordström and the third law of black hole thermodynamics
DESCRIPTION:General Relativity Seminar \nSpeaker: Christoph Kehle\, MIT \nTitle: Gravitational collapse to extremal Reissner-Nordström and the third law of black hole thermodynamics \nAbstract: In this talk\, I will present a proof that extremal Reissner-Nordström black holes can form in finite time in gravitational collapse of charged matter. In particular\, this construction provides a definitive disproof of the “third law” of black hole thermodynamics. I will also discuss recent works showing that extremal black holes take on a central role in gravitational collapse\, giving rise to a new conjectural picture of “extremal critical collapse.” This is joint work with Ryan Unger (Stanford).
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-101524/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-10.15.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241008T110000
DTEND;TZID=America/New_York:20241008T120000
DTSTAMP:20260414T090704
CREATED:20240903T181702Z
LAST-MODIFIED:20241004T144050Z
UID:10003423-1728385200-1728388800@cmsa.fas.harvard.edu
SUMMARY:Continuation of solutions of Einstein's equations
DESCRIPTION:General Relativity Seminar \nSpeaker: Oswaldo Vazquez\, Northeastern University \nTitle: Continuation of solutions of Einstein’s equations \nAbstract: Klainerman-Rodnianski improved the continuation criterion for the solutions of Einstein’s equations proved by Michael Anderson using Kirchoff-Sobolev type parametrix and geometric Littlewood-Paley theory. Using their technique but a new parametrix we prove a continuation condition in the context of 3+1 dimensional vacuum Einstein gravity in Constant Mean extrinsic Curvature (CMC) gauge. More precisely\, we obtain quantitative criteria under which the physical spacetime can be extended indefinitely in the future as a solution to the Cauchy problem of the Einstein equations given regular initial data. In particular\, we show that a gauge-invariant H^2 Sobolev norm of the spacetime Riemann curvature remains bounded in the future time direction provided the so-called deformation tensor of the unit timelike vector field normal to the chosen CMC hypersurfaces verifies a spacetime L^{\infty} bound.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-10824/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-10.8.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241001T110000
DTEND;TZID=America/New_York:20241001T120000
DTSTAMP:20260414T090704
CREATED:20240903T181544Z
LAST-MODIFIED:20240926T185818Z
UID:10003422-1727780400-1727784000@cmsa.fas.harvard.edu
SUMMARY:Quasinormal Corrections to Near-Extremal Black Hole Thermodynamics
DESCRIPTION:General Relativity Seminar \nSpeaker: Daniel Kapec\, Harvard \nTitle: Quasinormal Corrections to Near-Extremal Black Hole Thermodynamics \nAbstract: Recent work on the quantum mechanics of near-extremal non-supersymmetric black holes has identified a characteristic  scaling of the low temperature black hole partition function. This result has only been derived using the path integral in the near-horizon region and relies on many assumptions. We discuss how to derive the  scaling for the near-extremal rotating BTZ black hole from a calculation in the full black hole background using the Denef-Hartnoll-Sachdev (DHS) formula\, which expresses the 1-loop determinant of a thermal geometry in terms of a product over the quasinormal mode spectrum. We also derive the spectral measure for fields of any spin in Euclidean BTZ and use it to provide a new proof of the DHS formula and a new\, direct derivation of the BTZ heat kernel. The computations suggest a path to proving the  scaling for the asymptotically flat 4d Kerr black hole.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-10124/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-10.1.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240924T110000
DTEND;TZID=America/New_York:20240924T120000
DTSTAMP:20260414T090704
CREATED:20240903T181518Z
LAST-MODIFIED:20240917T155135Z
UID:10003421-1727175600-1727179200@cmsa.fas.harvard.edu
SUMMARY:New Energy Inequality in AdS
DESCRIPTION:General Relativity Seminar \nSpeaker: Diandian Wang\, Harvard University \nTitle: New Energy Inequality in AdS \nAbstract: I will describe evidence for a new energy inequality in asymptotically AdS spacetimes whose conformal boundary contains a spatial circle. It is in some sense analogous but crucially different to the Penrose inequality. In the AdS4 case\, this generalizes the Horowitz-Myers conjecture. I will show how static solutions play an interesting role in determining the shape of the function that bounds the gravitational energy.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-92417/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.24.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240916T093000
DTEND;TZID=America/New_York:20240916T103000
DTSTAMP:20260414T090704
CREATED:20240907T170536Z
LAST-MODIFIED:20240912T174105Z
UID:10003445-1726479000-1726482600@cmsa.fas.harvard.edu
SUMMARY:Ringdown in the SYK model
DESCRIPTION:Joint BHI/CMSA Foundation Seminar \nSpeaker: Matthew Dodelson (Harvard) \nTitle: Ringdown in the SYK model \nAbstract: Thermal correlators in large N systems equilibrate at late times\, but the precise late-time behavior is unknown away from holographic and free field limits. In this talk I will analyze this problem in the case of the SYK model away from the low-temperature limit. The basic technique is a resummation of perturbation theory which is reminiscent of the double cone construction. We will also discuss the interpretation of the result in terms of a dual stringy black hole.
URL:https://cmsa.fas.harvard.edu/event/foundation_91624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Foundation Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-BHI-Joint-Foundations-Seminar-09.16.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240513T163000
DTEND;TZID=America/New_York:20240513T173000
DTSTAMP:20260414T090704
CREATED:20240130T151206Z
LAST-MODIFIED:20240508T203329Z
UID:10000814-1715617800-1715621400@cmsa.fas.harvard.edu
SUMMARY:Errors and Correction in Cumulative Knowledge
DESCRIPTION:Colloquium \nSpeaker: Madhu Sudan\, Harvard University \nTitle: Errors and Correction in Cumulative Knowledge \nAbstract: Societal accumulation of knowledge is a complex\, and arguably error-prone\, process. The correctness of new units of knowledge depends not only on the correctness of the new reasoning\, but also on the correctness of old units that the new one builds on. If left unchecked\, errors could completely ruin the validity of most of this knowledge so there must some error-correcting going on. What are the error-corrections processes employed in nature and how effective are they? In this talk\, we describe our attempts to model such phenomena using probablistic models – we describe models for growth of cumulative knowledge\, emergence of errors and methods to check for errors and eliminate them. We then analyze in this compound model\, when effects of errors may survive\, and when they are totally eliminated. \nThe central discovery in our work is the following optimistic statement: If we do checking correctly (most of the time) investing just a constant factor (<1) of our effort in checking (and saving the remaining constant factor towards deriving new units of knowledge)\, then effects of errors can be kept in check. Notably the amount of effort expended on checking does not scale with the volume of total knowledge or the depth of dependencies in the new units of knowledge\, either of which would be overwhelming. \nBased on the papers: \nIs this correct? Let’s check!\nOmri Ben-Eliezer\, Dan Mikulincer\, Elchanan Mossel\, Madhu Sudan\narXiv:2211.12301 \nErrors are Robustly Tamed in Cumulative Knowledge Processes\nAnna Brandenberger\, Cassandra Marcussen\, Elchanan Mossel\, Madhu Sudan\narXiv:2309.05638
URL:https://cmsa.fas.harvard.edu/event/colloquium-4124/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-05.13.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240506T163000
DTEND;TZID=America/New_York:20240506T173000
DTSTAMP:20260414T090704
CREATED:20240319T201629Z
LAST-MODIFIED:20240507T201738Z
UID:10000819-1715013000-1715016600@cmsa.fas.harvard.edu
SUMMARY:Liouville Theory and Weil-Petersson Geometry
DESCRIPTION:Colloquium \nSpeaker: Sarah Harrison (Northeastern University) \nTitle: Liouville Theory and Weil-Petersson Geometry \nAbstract: Two-dimensional conformal field theory is a powerful tool to understand the geometry of surfaces. Liouville conformal field theory in the classical (large central charge) limit encodes the geometry of the moduli space of Riemann surfaces. I describe an efficient algorithm to compute the Weil–Petersson metric to arbitrary accuracy using Zamolodchikov’s recursion relation for conformal blocks\, focusing on examples of a sphere with four punctures and generalizations to other one-complex-dimensional moduli spaces. Comparison with analytic results for volumes and geodesic lengths finds excellent agreement. In the case of M_{0\,4}\, I discuss numerical results for eigenvalues of the Weil-Petersson Laplacian and connections with random matrix theory. \nBased on work with K. Coleville\, A. Maloney\, K. Namjou\, and T. Numasawa.
URL:https://cmsa.fas.harvard.edu/event/colloquium-5624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-05.06.2024.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240429T163000
DTEND;TZID=America/New_York:20240429T173000
DTSTAMP:20260414T090704
CREATED:20240207T190153Z
LAST-MODIFIED:20240424T142108Z
UID:10000818-1714408200-1714411800@cmsa.fas.harvard.edu
SUMMARY:The DNA of Particle Scattering
DESCRIPTION:Colloquium \nSpeaker: Lance Dixon (SLAC\, Stanford University) \nTitle: The DNA of Particle Scattering \nAbstract: At the Large Hadron Collider\, the copious scattering of quarks and gluons in quantum chromodynamics (QCD) produces Higgs bosons and many backgrounds to searches for new physics.  At short distances\, scattering in QCD can be evaluated in perturbation theory and leads to highly intricate\, multivariate mathematical functions such as generalized polylogarithms.  To gain further insight\, one can study a cousin of QCD called planar N=4 super-Yang-Mills theory.  Some processes in this theory can be computed to eighth order in perturbation theory\, versus second or third order in QCD.  The computation and analysis of these results rely on a Hopf algebra coaction on polylogarithms.  Its maximal iteration is called the ‘symbol’\, which serves as a ‘genetic code’ for amplitudes.  The symbol is a linear combination of words\, sequences of letters analogous to sequences of DNA base pairs.  Understanding the alphabet\, and then reading the code\, exposes the physics and mathematics of quantum scattering\, including bizarre new symmetries.  For example\, the two scattering amplitudes that are known to the highest orders in perturbation theory (8 loops) are related to each other by an ‘antipodal duality’\, which involves reading the code backwards as well as forwards. A third scattering amplitude\, which contains the other two as limits\, has an antipodal self-duality which ‘explains’ the other duality.  However\, we still don’t know ‘who ordered’ this property\, or what it really means. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-42924/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-04.29.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240318T163000
DTEND;TZID=America/New_York:20240318T173000
DTSTAMP:20260414T090704
CREATED:20240130T151005Z
LAST-MODIFIED:20240308T200603Z
UID:10000812-1710779400-1710783000@cmsa.fas.harvard.edu
SUMMARY:Koszul duality & twisted holography for asymptotically flat spacetimes
DESCRIPTION:Colloquium \nSpeaker: Natalie Paquette\, University of Washington \nTitle: Koszul duality & twisted holography for asymptotically flat spacetimes \nAbstract: Koszul duality has been understood in recent years to characterize order-type defects in twists of supersymmetric field theories. This notion has been generalized\, from a physical point of view\, by studying couplings between D-branes and closed string theories in the topological string. Computing the D-brane backreaction\, and studying the resulting open/closed string duality\, is the purview of the twisted holography program. Twisted holography seeks to study supersymmetric sectors of the AdS/CFT correspondence using these methods\, and leverage the appropriate generalization of Koszul duality to elucidate the bulk/boundary map. When applying these methods to a topological string configuration on twistor space\, one can construct an instance of twisted holography in which a 2d chiral algebra\, supported on the “celestial sphere”\, is dual to a 4d theory in an asymptotically flat spacetime. This is the first such top-down example of holography in a 4d asymptotically flat spacetime. This talk describes joint work done\, variously\, with Kevin Costello\, Brian Williams\, and Atul Sharma.
URL:https://cmsa.fas.harvard.edu/event/colloquium-31824/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-03.18.2024.docx-2_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240304T163000
DTEND;TZID=America/New_York:20240304T173000
DTSTAMP:20260414T090704
CREATED:20240130T150912Z
LAST-MODIFIED:20240228T213450Z
UID:10000810-1709569800-1709573400@cmsa.fas.harvard.edu
SUMMARY:Strong bounds for arithmetic progressions
DESCRIPTION:Colloquium \nSpeaker: Raghu Meka (UCLA) \nTitle: Strong bounds for arithmetic progressions \nAbstract: Suppose you have a set S of integers from {1\,2\,…\,N} that contains at least N / C elements. Then for large enough N\, must S contain three equally spaced numbers (i.e.\, a 3-term arithmetic progression)? \nIn 1953\, Roth showed this is the case when C is roughly (log log N). Behrend in 1946 showed that C can be at most exp(sqrt(log N)). Since then\, the problem has been a cornerstone of the area of additive combinatorics. Following a series of remarkable results\, a celebrated paper from 2020 due to Bloom and Sisask improved the lower bound on C to C = (log N)^(1+c) for some constant c > 0. \nThis talk will describe a new work showing that C can be much closer to Behrend’s construction. Based on joint work with Zander Kelley.
URL:https://cmsa.fas.harvard.edu/event/colloquium-3424/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-03.04.2024-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240226T163000
DTEND;TZID=America/New_York:20240226T173000
DTSTAMP:20260414T090704
CREATED:20240130T150524Z
LAST-MODIFIED:20240220T171315Z
UID:10000809-1708965000-1708968600@cmsa.fas.harvard.edu
SUMMARY:Factorization algebras in quite a lot of generality
DESCRIPTION:Colloquium \nSpeaker: Clark Barwick\, University of Edinburgh \nTitle: Factorization algebras in quite a lot of generality \nAbstract: The objects of arithmetic geometry are not manifolds. Some concepts from differential geometry admit analogues in arithmetic\, but they are not straightforward. How then can we hope to make precise sense of quantum field theories on these objects? I will propose the beginnings of a mathematical framework via a general theory of factorization algebras. A new feature is a subtle piece of additional structure on our objects – what I call a world-structure – that is ordinarily left implicit.
URL:https://cmsa.fas.harvard.edu/event/colloquium-22624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-02.26.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240212T163000
DTEND;TZID=America/New_York:20240212T173000
DTSTAMP:20260414T090704
CREATED:20240201T145702Z
LAST-MODIFIED:20240209T210827Z
UID:10000807-1707755400-1707759000@cmsa.fas.harvard.edu
SUMMARY:Machine Learning and Scientific Computing: There is plenty of room in the middle
DESCRIPTION:Colloquium \nSpeaker: Petros Koumoutsakos\, Harvard SEAS \nTitle: Machine Learning and Scientific Computing: There is plenty of room in the middle \nAbstract: Over the last thirty years we have experienced more than a billion-fold increase in hardware capabilities and a dizzying pace of acquiring and transmitting massive amounts of data. Scientific Computing and\, more lately\, Artificial Intelligence (AI) has been key beneficiaries of these advances. In this talk I would outline the need for bridging the decades long advances in Scientific Computing with those of AI. I will use examples from fluid mechanics to argue for forming alloys of AI and simulations for their prediction and control. I will present novel algorithms for learning the Effective Dynamics (LED) of complex systems and a fusion of multi- agent reinforcement learning and scientific computing (SciMARL) for modeling and control of turbulent flows. I will also show our recent work on Optimizing a Discrete Loss (ODIL) that outperforms popular techniques such as PINNs by several orders of magnitude. \nI will juxtapose successes and failures and argue that the proper fusion of scientific computing and AI expertise are essential to advance scientific frontiers. \n 
URL:https://cmsa.fas.harvard.edu/event/colloquium-21224/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-02.12.2024_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230412T123000
DTEND;TZID=America/New_York:20230412T133000
DTSTAMP:20260414T090704
CREATED:20230817T182227Z
LAST-MODIFIED:20240215T103145Z
UID:10001281-1681302600-1681306200@cmsa.fas.harvard.edu
SUMMARY:Unexpected Uses of Neural Networks: Field Theory and Metric Flows  
DESCRIPTION:Speaker: James Halverson (Northeastern University)\n \nTitle: Unexpected Uses of Neural Networks: Field Theory and Metric Flows\nAbstract:  We are now quite used to the idea that deep neural networks may be trained in a variety of ways to tackle cutting-edge problems in physics and mathematics\, sometimes leading to rigorous results. In this talk\, however\, I will argue that breakthroughs in deep learning theory are also useful for making progress\, focusing on applications to field theory and metric flows. Specifically\, I will introduce a neural network approach to field theory with a different statistical origin\, that exhibits generalized free field behavior at infinite width and interactions at finite width\, and that allows for the study of symmetries via the study of correlation functions in a different duality frame. Then\, I will review recent progress in approximating Calabi-Yau metrics as neural networks and cast that story into the language of neural tangent kernel theory\, yielding a theoretical understanding of neural network metric flows induced by gradient descent and recovering famous metric flows\, such as Perelman’s formulation of Ricci flow\, in particular limits.
URL:https://cmsa.fas.harvard.edu/event/colloquium12523/
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/02CMSA-Colloquium-04.12.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230202T123000
DTEND;TZID=America/New_York:20230202T133000
DTSTAMP:20260414T090704
CREATED:20230817T175011Z
LAST-MODIFIED:20240121T174936Z
UID:10001272-1675341000-1675344600@cmsa.fas.harvard.edu
SUMMARY:Neural Optimal Stopping Boundary
DESCRIPTION:Speaker: Max Reppen (Boston University) \nTitle: Neural Optimal Stopping Boundary \nAbstract:  A method based on deep artificial neural networks and empirical risk minimization is developed to calculate the boundary separating the stopping and continuation regions in optimal stopping. The algorithm parameterizes the stopping boundary as the graph of a function and introduces relaxed stopping rules based on fuzzy boundaries to facilitate efficient optimization. Several financial instruments\, some in high dimensions\, are analyzed through this method\, demonstrating its effectiveness. The existence of the stopping boundary is also proved under natural structural assumptions.
URL:https://cmsa.fas.harvard.edu/event/colloquium_2223/
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/02CMSA-Colloquium-02.02.2023.png
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END:VCALENDAR