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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250422T110000
DTEND;TZID=America/New_York:20250422T120000
DTSTAMP:20260426T045649
CREATED:20250128T213711Z
LAST-MODIFIED:20250418T204712Z
UID:10003704-1745319600-1745323200@cmsa.fas.harvard.edu
SUMMARY:Hyperbolic equations in a double null gauge
DESCRIPTION:General Relativity Seminar \nSpeaker: Christopher Stith\, University of Michigan \nTitle: Hyperbolic equations in a double null gauge \nAbstract: The hyperbolic nature of the Einstein equations is well-known and has been used in many different contexts. More recently\, the double null gauge has proven to be a powerful tool for quantitative analysis of the Einstein equations. It has the advantage of reducing the equations for many dynamical quantities to ODEs along null curves\, and the Bianchi equations to a first-order hyperbolic system. The double null gauge has been used extensively and to great effect in analyzing the structure of spacetime for many purposes\, including (for instance) stability problems and trapped surface formation. However\, the local existence problem for the Einstein equations in a double null gauge has never been treated in full in its own right. In this talk\, we discuss how to formulate a general procedure for solving the linearized problem\, namely\, the local existence theory for systems of first-order hyperbolic equations in a double null gauge.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-42225/
LOCATION:CMSA G102\, 20 Garden Street\, Cambridge\, MA\, 02138
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-4.22.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250415T110000
DTEND;TZID=America/New_York:20250415T120000
DTSTAMP:20260426T045649
CREATED:20250128T213613Z
LAST-MODIFIED:20250409T142345Z
UID:10003703-1744714800-1744718400@cmsa.fas.harvard.edu
SUMMARY:Positive mass theorem for ALE(AE) and ALF(AF) Toric 4-Manifolds
DESCRIPTION:General Relativity Seminar \nSpeaker: Aghil Alaee\, Clark University \nTitle: Positive mass theorem for ALE(AE) and ALF(AF) Toric 4-Manifolds \nAbstract: One of the fundamental conjectures in mathematical relativity is the positivity of total mass (if it is defined!) for complete non-compact Riemannian manifolds assuming appropriate lower bounds on scalar curvature. This conjecture has been proved for AE manifolds using several techniques\, starting with the celebrated results of Schoen-Yau and Witten. There are counter-examples to this conjecture in the AF\, ALF\, and ALE cases. In this talk\, we will refine this conjecture and prove it for toric 4-manifolds. The proof is robust and can be extended to higher dimensions if additional assumptions are added. This is a joint work with Marcus Khuri and Hari Kunduri.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-41525/
LOCATION:CMSA G102\, 20 Garden Street\, Cambridge\, MA\, 02138
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-4.15.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250401T110000
DTEND;TZID=America/New_York:20250401T120000
DTSTAMP:20260426T045649
CREATED:20250128T213541Z
LAST-MODIFIED:20250331T195936Z
UID:10003702-1743505200-1743508800@cmsa.fas.harvard.edu
SUMMARY:Low-regularity Local Well-posedness of the Elastic Wave System
DESCRIPTION:General Relativity Seminar \nSpeaker: Sifan Yu\, National University of Singapore \nTitle: Low-regularity Local Well-posedness of the Elastic Wave System \nAbstract: In this talk\, I will present a recent work on the elastic wave system in three spatial dimensions. For admissible harmonic elastic materials\, we prove a low-regularity local well-posedness result for the corresponding elastic wave equations. For such materials\, we can split the dynamics into the “divergence-part” and the “curl-part\,” and each part satisfies a distinct coupled quasilinear wave system with respect to different acoustical metrics. Our main result is that the Sobolev norm H^{3+} of the “divergence-part” (the “faster-wave part”) and the H^{4+} of the “curl-part” (the “slower-wave part”) can be controlled in terms of initial data for short times. We note that the Sobolev norm assumption H^{3+} is optimal for the “divergence-part.” This is a joint work with Xinliang An and Haoyang Chen.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-4125/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-4.1.2025.docx_11-am.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250325T160000
DTEND;TZID=America/New_York:20250325T170000
DTSTAMP:20260426T045649
CREATED:20250128T213506Z
LAST-MODIFIED:20250326T194012Z
UID:10003701-1742918400-1742922000@cmsa.fas.harvard.edu
SUMMARY:Unstable Fluids in Expanding Cosmologies
DESCRIPTION:General Relativity Seminar \nSpeaker: Elliot Marshal\, School of Mathematics at Monash University \nTitle: Unstable Fluids in Expanding Cosmologies \nAbstract: The FLRW solution is the simplest cosmological model in general relativity\, describing a fluid-filled\, spatially homogeneous universe. While there is extensive literature in the physics community on cosmological models with a linear equation of state \, rigorous stability results have\, until recently\, been limited to FLRW models with accelerated expansion and small sound speeds. In this talk\, I will discuss numerical work on two types of instabilities which can occur in non-linearly perturbed FLRW models outside of this regime. The first concerns a longstanding conjecture of Alan Rendall on FLRW models with positive cosmological constant and super-radiative (K>1/3) equations of state. Our numerical work\, in collaboration with F. Beyer and T.A. Oliynyk\, supports Rendall’s conjecture and highlights the underlying mechanism for the instability. In the second case\, I will discuss evidence that perturbations of slowly expanding (decelerated) FLRW models generically form shocks in finite time. This contrasts with known results for accelerated models where shock formation is suppressed for suitably small perturbations.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-32525/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-3.25.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250311T110000
DTEND;TZID=America/New_York:20250311T120000
DTSTAMP:20260426T045649
CREATED:20250128T213420Z
LAST-MODIFIED:20250312T191855Z
UID:10003700-1741690800-1741694400@cmsa.fas.harvard.edu
SUMMARY:Positive scalar curvature with point singularities
DESCRIPTION:General Relativity Seminar \nSpeaker: Rudolf Zeidler\, Mathematical Institute\, University of Münster \nTitle: Positive scalar curvature with point singularities \nAbstract: I will explain a certain topological construction of positive scalar curvature metrics with uniformly Euclidean ($L^\infty$) point singularities. This provides counterexamples to a conjecture of Schoen. It also shows that there are metrics with uniformly Euclidean point singularities which cannot be smoothed via a geometric flow while simultaneously preserving non-negativity of the scalar curvature. Based on recent joint work with Simone Cecchini and Georg Frenck.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-31125/
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-3.11.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250225T110000
DTEND;TZID=America/New_York:20250225T120000
DTSTAMP:20260426T045649
CREATED:20240903T183821Z
LAST-MODIFIED:20250228T212719Z
UID:10003420-1740481200-1740484800@cmsa.fas.harvard.edu
SUMMARY:BKL bounces outside homogeneity
DESCRIPTION:General Relativity Seminar \nSpeaker: Warren Li ( Princeton University) \nTitle: BKL bounces outside homogeneity \nAbstract: In work spanning the late 20th century\, physicists Belinski\, Khalatnikov and Lifshitz (BKL) proposed a general ansatz for solutions to the Einstein (vacuum) equations near singularities. They suggest that the spacetime dynamics at different spatial points on the singularity decouple and are well-approximated by a system of autonomous nonlinear ODEs\, whose orbits are governed by a chaotic cascade of “BKL bounces”. In this talk\, we present recent work verifying BKL’s heuristics in a large class of symmetric\, but spatially inhomogeneous\, spacetimes. In particular\, we prove decoupling even in the presence of (up to one) BKL bounce. The proof uses nonlinear ODE analysis coupled to hyperbolic energy estimates\, and one hopes our methods may be applied more generally.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-22525/
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/1740157873632-2128c0f1-4416-42e5-a58b-0475ecffb3852025-1_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250218T110000
DTEND;TZID=America/New_York:20250218T120000
DTSTAMP:20260426T045649
CREATED:20240903T191953Z
LAST-MODIFIED:20250219T144101Z
UID:10003426-1739876400-1739880000@cmsa.fas.harvard.edu
SUMMARY:General Relativity Seminar
DESCRIPTION:General Relativity Seminar \nSpeaker: Maximilian Ofner\, University of Vienna \nTitle: Stability and Instability of Relativistic Fluids in Slowly Expanding Spacetimes \nAbstract: Homogeneous and isotropic solutions to the relativistic Euler equations are known to be unstable on a Minkowski background. However\, for FLRW models with a fast expansion rate\, relativistic fluids stabilize. This scenario suggests a transition between stable and unstable behavior\, somewhere along a family of spacetimes parametrized by their expansion rate. In this talk we will discuss this phase transition for various equations of state\, focusing on the regime of linear and decelerated expansion. This is based on recent analytical results\, complemented by numerical analysis.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-21825/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-2.18.25.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250211T110000
DTEND;TZID=America/New_York:20250211T120000
DTSTAMP:20260426T045649
CREATED:20250128T211214Z
LAST-MODIFIED:20250210T141458Z
UID:10003698-1739271600-1739275200@cmsa.fas.harvard.edu
SUMMARY:On the past maximal development of near-FLRW data for the  Einstein scalar-field Vlasov system
DESCRIPTION:General Relativity Seminar \nSpeaker: Liam Urban (University of Vienna) \n\nTitle: On the past maximal development of near-FLRW data for the Einstein scalar-field Vlasov system \nAbstract: In recent years\, the formation of Big Bang singularities has been increasingly well understood in presence of scalar-field matter\, which suppresses the geometric oscillations that one generically expects otherwise. From a cosmological perspective\, however\, one would like to understand whether this feature persists when coupled to further models that more closely resemble the matter content in our universe. \nIn this talk\, I will discuss the past nonlinear stability of FLRW solutions to the Einstein scalar-field Vlasov system in three and four spacetime dimensions without symmetry assumptions. The latter is based on joint work with David Fajman. In both works\, near-FLRW solutions are\nshown to be asymptotically velocity term dominated toward the past\,  resulting in a quiescent Big Bang singularity with stable Kretschmann scalar blow-up. The Vlasov distribution\, however\, becomes highly anisotropic towards the Big Bang singularity\, concentrating in preferred momentum directions associated with eigendirections of the shear. To ensure that the scalar field sufficiently mitigates this behaviour\, one crucially exploits a scaling hierarchy between horizontal and vertical derivatives in the expansion normalized Vlasov equation. In four\nspacetime dimensions\, this analysis is paired with a Bel-Robinson energy formalism to control the spacetime and scalar field evolution\, while one finds a significantly more direct proof in three dimensions since the spatial Riemann curvature is pure trace. \nAs a corollary\, one also obtains that the Strong Cosmic Censorship conjecture holds for four-dimensional polarized $U(1)$-symmetric solutions to the Einstein vacuum equations with spatial topology $M\times\S^1$ and isotropic quotient.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-21125/
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/1738856087821-8bd46bd5-9d75-4777-80dd-59b2ca5dc8d52025_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250204T110000
DTEND;TZID=America/New_York:20250204T120000
DTSTAMP:20260426T045649
CREATED:20240903T192049Z
LAST-MODIFIED:20250130T190257Z
UID:10003428-1738666800-1738670400@cmsa.fas.harvard.edu
SUMMARY:The mass angular momentum inequality
DESCRIPTION:General Relativity Seminar \nSpeaker: Gilbert Weinstein\, Ariel University \nTitle: The mass angular momentum inequality \nAbstract: We show that either there is a counterexample to black hole uniqueness\, in the form of a regular axisymmetric stationary vacuum spacetime with an asymptotically flat end and multiple degenerate horizons which is ‘ADM stable’\, or the following statement holds. Complete\, simply connected\, maximal initial data sets for the Einstein equations with multiple ends that are either asymptotically flat or asymptotically cylindrical\, admit an ADM mass lower bound given by the square root of total angular momentum\, under the assumption of nonnegative energy density and axisymmetry. Moreover\, equality is achieved bound only for a constant time slice of an extreme Kerr spacetime. The proof is based on a novel flow of singular harmonic maps with hyperbolic plane target\, under which the renormalized harmonic energy is monotonically nonincreasing. Relevant properties of the flow are achieved through a refined asymptotic analysis of solutions to the linearized harmonic map equations.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-2425/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-2.4.25.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241210T110000
DTEND;TZID=America/New_York:20241210T120000
DTSTAMP:20260426T045649
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:20241203T110000
DTEND;TZID=America/New_York:20241203T120000
DTSTAMP:20260426T045649
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:20241119T110000
DTEND;TZID=America/New_York:20241119T120000
DTSTAMP:20260426T045649
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:20260426T045649
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:20241029T110000
DTEND;TZID=America/New_York:20241029T120000
DTSTAMP:20260426T045649
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:20241015T110000
DTEND;TZID=America/New_York:20241015T120000
DTSTAMP:20260426T045649
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:20260426T045649
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:20260426T045649
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:20260426T045649
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:20240516T150000
DTEND;TZID=America/New_York:20240516T160000
DTSTAMP:20260426T045649
CREATED:20240510T170616Z
LAST-MODIFIED:20240510T175234Z
UID:10003387-1715871600-1715875200@cmsa.fas.harvard.edu
SUMMARY:Geometry of Generalized Lienard Equations\, Contact Geometry and Metriplectic Structure
DESCRIPTION:Speaker: Partha Guha\, Khalifa University\, Abu Dhabi \nTitle: Geometry of Generalized Lienard Equations\, Contact Geometry and Metriplectic Structure \nAbstract: We start with a self-contained brief review of the construction of non-standard Lagrangian and Hamiltonian structures using the Jacobi Last Multiplier for the (generalized) reduced Lienard equations satisfying Chiellini integrability condition\, we then explore its connection with the contact Hamiltonian mechanics. We also explore Lienard equations\, of reaction-diffusion class and conformal (or contact) Hamiltonian Structures. Finally\, we present the geometric formulation of the generalized Lienard equations in terms of metriplectic structure. \nJoint work with Jose Carinena and Anindya Ghose Choudhury
URL:https://cmsa.fas.harvard.edu/event/geometry_51624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Special Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Geometry-and-Physics-Seminar-05.16.2024.docx-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240513T110000
DTEND;TZID=America/New_York:20240513T120000
DTSTAMP:20260426T045649
CREATED:20240411T181646Z
LAST-MODIFIED:20240514T142424Z
UID:10003354-1715598000-1715601600@cmsa.fas.harvard.edu
SUMMARY:An analogue of non-interacting quantum field theory in Riemannian signature
DESCRIPTION:General Relativity Seminar \nSpeaker: Mikhail Molodyk\, Stanford \nTitle: An analogue of non-interacting quantum field theory in Riemannian signature \nAbstract: Recent advances using microlocal tools have led to constructions\, for wave operators on various classes of spacetimes\, of four distinguished Fredholm inverses which have the singular behavior required of retarded\, advanced\, Feynman\, and anti-Feynman propagators in QFT. Vasy and Wrochna have used these to define a QFT on asymptotically Minkowski spacetimes\, for which they construct Hadamard states described by asymptotic data at infinity. I will describe an analogue of this construction on Riemannian manifolds with two asymptotically conic ends\, defining quantum fields satisfying the Helmholtz equation and using scattering data to construct states satisfying a wavefront mapping-property version of the Hadamard condition. The absence of a spacetime interpretation lends itself to a sharper focus on the theory’s analytic structure\, from whose perspective the Feynman propagators are no less natural than the advanced/retarded ones. I will also highlight some differences between Feynman propagators defined as distinguished inverses and as time-ordered expectations. Based on joint work with András Vasy.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-51324/
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-05.13.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240507T140000
DTEND;TZID=America/New_York:20240507T150000
DTSTAMP:20260426T045649
CREATED:20240411T181320Z
LAST-MODIFIED:20240819T151524Z
UID:10000835-1715090400-1715094000@cmsa.fas.harvard.edu
SUMMARY:Real-time observables in horizon thermodynamics
DESCRIPTION:General Relativity Seminar \nSpeaker: Albert Law\, Stanford \nTitle: Real-time observables in horizon thermodynamics \nAbstract: Euclidean black hole 1-loop determinants have recently been shown to compute a renormalized thermal canonical partition function for free fields in Lorentzian signature. A key ingredient is a ‘quasinormal mode (QNM) character’\, whose Fourier transform equals the renormalized spectral density of the single-particle Hamiltonian. Using a static patch in de Sitter space as an example\, in this talk\, I will offer new perspectives on the QNM character\, including its connection with the local density of states for the single-particle quantum mechanical problem associated with the Klein-Gordon equation\, and its direct relationships with (thermal) correlators of the free fields. I will discuss how these considerations might point toward a generalization to interacting theories.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-5724/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-05.7.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240423T100000
DTEND;TZID=America/New_York:20240423T110000
DTSTAMP:20260426T045649
CREATED:20240415T162430Z
LAST-MODIFIED:20240422T154105Z
UID:10000833-1713866400-1713870000@cmsa.fas.harvard.edu
SUMMARY:Quantum Energy Inequalities
DESCRIPTION:General Relativity Seminar \nSpeaker: Chris Fewster\, York University \nTitle: Quantum Energy Inequalities \nAbstract: Many theorems of mathematical relativity\, including singularity and positive mass theorems\, include the classical energy conditions among their hypotheses. However\, matter described by quantum field theory can violate the classical energy conditions and indeed there is no lower bound to the energy density at a given point as the quantum state is varied. Do the classical theorems apply to quantised matter? \nIn this talk I discuss Quantum Energy Inequalities\, lower bounds on averages of the energy density along timelike curves or over spacetime regions\, that have been proved in QFT and are the remnants of the classical energy conditions after quantisation. I will also discuss some of their consequences.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar_42324/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240416T110000
DTEND;TZID=America/New_York:20240416T120000
DTSTAMP:20260426T045649
CREATED:20240409T163938Z
LAST-MODIFIED:20240502T195940Z
UID:10000832-1713265200-1713268800@cmsa.fas.harvard.edu
SUMMARY:New Well-Posed Boundary Conditions for Semi-Classical Euclidean Gravity
DESCRIPTION:General Relativity Seminar \nSpeaker: Xiaoyi Liu\, UCSB \nTitle: New Well-Posed Boundary Conditions for Semi-Classical Euclidean Gravity \nAbstract: We consider four-dimensional Euclidean gravity in a finite cavity.  We point out that there exists a one-parameter family of boundary conditions\, parameterized by a real constant\, where a suitably Weyl-rescaled boundary metric is fixed\, and all give a well-posed elliptic system\, as opposed to the Dirichlet boundary condition. Focussing on static Euclidean solutions\, we derive a thermodynamic first law. Restricting to a spherical spatial boundary\, the infillings are flat space or the Schwarzschild solution and have similar thermodynamics to the Dirichlet case. We study the stability behavior of several geometries under these boundary conditions in both Euclidean and Lorentzian signatures and find two puzzles.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar_41624/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-04.16.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240402T110000
DTEND;TZID=America/New_York:20240402T120000
DTSTAMP:20260426T045649
CREATED:20240325T132956Z
LAST-MODIFIED:20240325T150323Z
UID:10000830-1712055600-1712059200@cmsa.fas.harvard.edu
SUMMARY:Linearised Second Law for Higher Curvature Gravity and Non-Minimally Coupled Vector Fields
DESCRIPTION:General Relativity Seminar \nSpeaker: Zihan Yan\, Cambridge University \n\n\n\nTitle: Linearised Second Law for Higher Curvature Gravity and Non-Minimally Coupled Vector Fields \n\n\n\nAbstract: Expanding the work of arXiv:1504.08040\, we show that black holes obey a second law for linear perturbations to bifurcate Killing horizons\, in any covariant higher curvature gravity coupled to scalar and vector fields. The vector fields do not need to be gauged\, and (like the scalars) can have arbitrary non-minimal couplings to the metric. The increasing entropy has a natural expression in covariant phase space language\, which makes it manifestly invariant under JKM ambiguities. An explicit entropy formula is given for f(Riemann) gravity coupled to vectors\, where at most one derivative acts on each vector. Besides the previously known curvature terms\, there are three extra terms involving differentiating the Lagrangian by the symmetric vector derivative (which therefore vanish for gauge fields).
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-3/
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-04.02.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240319T103000
DTEND;TZID=America/New_York:20240319T113000
DTSTAMP:20260426T045649
CREATED:20240318T134919Z
LAST-MODIFIED:20240318T135543Z
UID:10000828-1710844200-1710847800@cmsa.fas.harvard.edu
SUMMARY:Scattering Rigidity Problem
DESCRIPTION:General Relativity Seminar \nSpeaker: Jin Jia\, Hunan University \nTitle: Scattering Rigidity Problem \nAbstract: If the asymptotic behavior of a solution to a nonlinear equation is the same as that of a solution to its linearized equation\, it is called a scattering solution. Scattering phenomena are widely observed near steady-state solutions of various mathematical physics equations\, such as water wave equations\, Einstein equations\, MHD equations\, and Vlasov-Poisson equations. This report takes these equations as examples to provide the definition of scattering operator and its relation to radiation fields. It explains the concepts of scattering rigidity problem and scattering completeness problem\, and introduces the latest discoveries of the speaker in the general solution approach to scattering rigidity problem.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-31924/
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:20240305T110000
DTEND;TZID=America/New_York:20240305T120000
DTSTAMP:20260426T045649
CREATED:20240229T165205Z
LAST-MODIFIED:20240813T154631Z
UID:10000827-1709636400-1709640000@cmsa.fas.harvard.edu
SUMMARY:High order WENO finite difference scheme  for Einstein-Yang-Mills equations
DESCRIPTION:General Relativity Seminar \nSpeaker: Yuewen Chen\, Tsinghua University \nTitle: High order WENO finite difference scheme  for Einstein-Yang-Mills equations \nAbstract: In this talk\, we will show the convergence analysis of the first-order finite difference scheme for static spherically symmetric $SU(2)$ Einstein-Yang-Mills (EYM) equations. We also construct a new WENO scheme for EYM.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-3524/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-03.05.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240227T110000
DTEND;TZID=America/New_York:20240227T120000
DTSTAMP:20260426T045649
CREATED:20240226T152845Z
LAST-MODIFIED:20240227T193918Z
UID:10000826-1709031600-1709035200@cmsa.fas.harvard.edu
SUMMARY:On Axially Symmetric Perturbations of Kerr Black Hole Spacetimes
DESCRIPTION:General Relativity Seminar \nSpeaker: Nishanth Gudapati\, Clark University \nTitle: On Axially Symmetric Perturbations of Kerr Black Hole Spacetimes \nAbstract: The Kerr black hole stability problem is an important open problem in general relativity. In this talk\, I will focus on the role of energy methods in the axisymmetric stability of Kerr black hole spacetimes. In particular\, I will discuss the construction and the application of a positive Hamiltonian energy for axially symmetric Maxwell and Einstein perturbations of sub-extremal Kerr black hole spacetimes.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-22724/
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-02.27.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240220T093000
DTEND;TZID=America/New_York:20240220T103000
DTSTAMP:20260426T045649
CREATED:20240219T195817Z
LAST-MODIFIED:20240219T195829Z
UID:10000825-1708421400-1708425000@cmsa.fas.harvard.edu
SUMMARY:Asymptotic decay for defocusing semilinear wave equations on Schwarzschild spacetimes
DESCRIPTION:General Relativity Seminar \nSpeaker: He Mei\, Shenzhen University \nTitle: Asymptotic decay for defocusing semilinear wave equations on Schwarzschild spacetimes \nAbstract: In this talk\, I will present a work on the long time dynamics of solutions to the defocusing semilinear wave equations on the Schwarzschild black hole spacetimes. For sufficiently smooth and localized initial data\, we show that the solution decays in the domain of outer communication. The proof relies on a vector field method of Dafermos-Rodnianski together with Strichartz estimates for linear waves by Marzuola-Metcalfe-Tataru-Tohaneanu.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-22024/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240213T110000
DTEND;TZID=America/New_York:20240213T110000
DTSTAMP:20260426T045649
CREATED:20240212T161202Z
LAST-MODIFIED:20240212T181141Z
UID:10000824-1707822000-1707822000@cmsa.fas.harvard.edu
SUMMARY:Characteristic Initial Value Problem for the 3D Compressible Euler Equations
DESCRIPTION:General Relativity Seminar \nSpeaker: Sifan Yu\, NUS \nTitle: Characteristic Initial Value Problem for the 3D Compressible Euler Equations \nAbstract: We present the first result for the characteristic initial value problem of the compressible Euler equations in three space dimensions without any symmetry assumption. We allow presence of vorticity and consider any equation of state. Compared to the standard Cauchy problem\, where initial data can be freely prescribed on a constant-time hypersurface\, we formulate the problem by distinguishing between the “free-component” and the “constrained-component” of the initial data. The latter is to be solved by the “free-component” utilizing the properties of the compressible Euler equations on the initial null hypersurfaces. Then\, we establish a priori estimates\, followed by a local well-posedness and a continuation criterion argument. Moreover\, we prove a regularity theory in Sobolev norms. Our analysis critically relies on the vectorfield method due to the nature of the problem. This is a joint work with Jared Speck.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-21324/
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-02.13.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240206T100000
DTEND;TZID=America/New_York:20240206T110000
DTSTAMP:20260426T045649
CREATED:20240202T170516Z
LAST-MODIFIED:20240209T200944Z
UID:10000823-1707213600-1707217200@cmsa.fas.harvard.edu
SUMMARY:Noncompact n-dimensional Einstein spaces as attractors for the Einstein flow
DESCRIPTION:General Relativity Seminar \nSpeaker: Jinhua Wang\, Xiamen University \nTitle: Noncompact n-dimensional Einstein spaces as attractors for the Einstein flow \nAbstract: We prove that along with the Einstein flow\, any small perturbations of an $n$($n\geq4$)-dimensional\, non-compact negative Einstein space with some “non-positive Weyl tensor” lead to a unique and global solution\, and the solution will be attracted to a noncompact Einstein space that is close to the background one. The $n=3$ case has been addressed by Wang-Yuan\, while in dimension $n\geq 4$\, as we know\, negative Einstein metrics in general have non-trivial moduli spaces. This fact is reflected on the structure of Einstein equations\, which further indicates no decay for the spatial Weyl tensor. Furthermore\, it is suggested in the proof that the mechanic preventing the metric from flowing back to the original Einstein metric lies in the non-decaying character of spatial Weyl tensor. In contrary to the compact case considered in Andersson-Moncrief\, our proof is independent of the theory of infinitesimal Einstein deformations. Instead\, we take advantage of the inherent geometric structures of Einstein equations and develop an approach of energy estimates for a hyperbolic system of Maxwell type. \nReferences – arXiv: 2209.15244\, 2309.15152\, 2311.00868
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-2624/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-02.06.2024.png
END:VEVENT
END:VCALENDAR