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DTSTART;TZID=America/New_York:20250731T110000
DTEND;TZID=America/New_York:20250731T120000
DTSTAMP:20260419T215748
CREATED:20250730T163542Z
LAST-MODIFIED:20250730T182012Z
UID:10003759-1753959600-1753963200@cmsa.fas.harvard.edu
SUMMARY:Joint BHI/CMSA Foundation Seminar: The semiclassical energy outflux emerging from a collapsing shell
DESCRIPTION:Joint BHI/CMSA Foundation Seminar \nLocation: BHI seminar room \nSpeaker: Noa Zilberman (Princeton University) \nTitle: The semiclassical energy outflux emerging from a collapsing shell \nAbstract: When a compact object collapses to form a black hole\, quantum field theory predicts the emission of an energy outflux to future null infinity\, which later relaxes to Hawking radiation. Within the semiclassical framework\, we derive a simple\, closed form\, analytical expression for the energy outflux emitted from a spherical thin null shell collapsing to form a black hole. In particular\, this energy outflux vanishes (quadratically in r-2M) as the shell approaches the horizon. This result refutes claims that the Hawking energy outflux originates from the collapsing body\, showing instead that it develops in a broad strong-field region. Additionally\, this vanishing implies that semiclassical backreaction cannot prevent or significantly affect the classical process of gravitational collapse and horizon formation (as sometimes claimed). \n 
URL:https://cmsa.fas.harvard.edu/event/joint-bhi-cmsa-foundation-seminar-the-semiclassical-energy-outflux-emerging-from-a-collapsing-shell/
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/CMSA-BHI-Joint-Foundations-Seminar-07.31.25-scaled.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250422T110000
DTEND;TZID=America/New_York:20250422T120000
DTSTAMP:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20250210T093000
DTEND;TZID=America/New_York:20250210T103000
DTSTAMP:20260419T215748
CREATED:20250123T204528Z
LAST-MODIFIED:20250127T204354Z
UID:10003667-1739179800-1739183400@cmsa.fas.harvard.edu
SUMMARY:Joint BHI/CMSA Foundation Seminar: Quantum Effects Inside Black Holes
DESCRIPTION:Joint BHI/CMSA Foundation Seminar \nLocation: BHI seminar room \nSpeaker: Noa Zilberman (Princeton University) \nTitle: Quantum Effects Inside Black Holes \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. \n 
URL:https://cmsa.fas.harvard.edu/event/foundation_21025-2/
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/CMSA-BHI-Joint-Foundations-Seminar-2.10.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20250204T110000
DTEND;TZID=America/New_York:20250204T120000
DTSTAMP:20260419T215748
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:20250127T093000
DTEND;TZID=America/New_York:20250127T103000
DTSTAMP:20260419T215748
CREATED:20250123T201747Z
LAST-MODIFIED:20250127T204324Z
UID:10003668-1737970200-1737973800@cmsa.fas.harvard.edu
SUMMARY:Joint BHI/CMSA Foundation Seminar: Quantum Criticality in Black Hole Dynamics
DESCRIPTION:Joint BHI/CMSA Foundation Seminar \nLocation: BHI Seminar Room \nSpeaker: Uri Kol\, Harvard CMSA \n\nTitle: Quantum Criticality in Black Hole Dynamics \nAbstract: Black hole perturbation theory captures a few important effects in the dynamics of binary mergers\, such as tidal deformations and the decay of ringdown modes\, as well as the physics of the photon ring. However\, deriving qualitative results that lead to robust predictions in this theory remains a challenging problem\, despite a rich scientific history.\nMotivated by the immense experimental progress made in the field over the past decade\, in this talk I will describe a new critical phenomenon emerging in the theory of perturbations around Kerr black holes. A critical point is identified at zero black hole temperature\, giving rise to a wide regime at finite temperatures which is dominated by critical perturbations. As in quantum many-body systems\, the physics in the critical regime is described exclusively by a set of critical exponents\, therefore leading to robust predictions that are unique to the Kerr metric.
URL:https://cmsa.fas.harvard.edu/event/foundation_12725/
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/CMSA-BHI-Joint-Foundations-Seminar-1.27.2025.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241210T110000
DTEND;TZID=America/New_York:20241210T120000
DTSTAMP:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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:20260419T215748
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
END:VCALENDAR