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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240319T103000
DTEND;TZID=America/New_York:20240319T113000
DTSTAMP:20260501T113113
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:20260501T113113
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:20260501T113113
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:20260501T113113
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:20260501T113113
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:20260501T113113
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
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240130T110000
DTEND;TZID=America/New_York:20240130T120000
DTSTAMP:20260501T113113
CREATED:20240126T184234Z
LAST-MODIFIED:20240813T154857Z
UID:10000822-1706612400-1706616000@cmsa.fas.harvard.edu
SUMMARY:A quasi-local mass in general relativity
DESCRIPTION:General Relativity Seminar \nSpeaker: Aghil Alaee\, Clark University \nTitle: A quasi-local mass in general relativity \nAbstract: In this talk\, we define a new gauge-independent quasi-local mass and energy with respect to the Minkowski spacetime. In contrast to other quasi-local masses\, this new quasi-local mass/energy has a quasi-local proof of positivity. This positivity property is for spacelike surfaces with any topology.  Moreover\, we show that it has desired asymptotic behaviors at null and spatial infinity of asymptotically flat spacetimes. Rigidity is also established in that vanishing energy implies that the 2-surface arises from an embedding into Minkowski space\, and conversely\, the mass vanishes for any such surface. This is joint work with M. Khuri and S.T. Yau. \n 
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-13024/
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-01.30.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231205T110000
DTEND;TZID=America/New_York:20231205T120000
DTSTAMP:20260501T113113
CREATED:20240226T112803Z
LAST-MODIFIED:20240813T160712Z
UID:10002870-1701774000-1701777600@cmsa.fas.harvard.edu
SUMMARY:The Feynman propagator and self-adjointness
DESCRIPTION:General Relativity Seminar \nSpeaker: Andras Vasy (Stanford) \nTitle: The Feynman propagator and self-adjointness \nAbstract: In this talk I will discuss the Feynman and anti-Feynman inverses for wave operators on certain Lorentzian manifolds; these are two inverses which from a microlocal analysis perspective are more natural than the standard causal (advanced/retarded) ones. For instance\, for the spectral family of the wave operator\, these are the natural inverses when the spectral parameter is non-real. Indeed\, I will explain that these connect to the self-adjointness of the wave operator\, and the positivity properties that follow. \n 
URL:https://cmsa.fas.harvard.edu/event/gr_12523/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-12.05.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231128T110000
DTEND;TZID=America/New_York:20231128T120000
DTSTAMP:20260501T113113
CREATED:20240223T051146Z
LAST-MODIFIED:20240223T051146Z
UID:10002813-1701169200-1701172800@cmsa.fas.harvard.edu
SUMMARY:Remarkable symmetries of rotating black holes
DESCRIPTION:General Relativity Seminar \nSpeaker: David Kubiznak (Charles University) \nTitle: Remarkable symmetries of rotating black holes \nAbstract: It is well known that the Kerr geometry admits a non-trivial Killing tensor and its ‘square root’ known as the Killing-Yano tensor. These two objects stand behind Carter’s constant of geodesic motion as well as allow for separability of test field equations in this background. The situation is even more remarkable in higher dimensions\, where a single object — the principal Killing-Yano tensor — generates a tower of explicit and hidden symmetries responsible for integrability of geodesics and separability of test fields around higher-dimensional rotating black holes. Interestingly\, similar yet different structure is already present for the slowly rotating black holes described by the `magic square’ version of the Lense-Thirring solution\, giving rise to a geometrically preferred spacetime that can be cast in the Painleve-Gullstrand form and admits a tower of exact rank-2 and higher rank Killing tensors whose number rapidly grows with the number of spacetime dimensions.
URL:https://cmsa.fas.harvard.edu/event/gr_112823/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.28.23_Page_1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231114T110000
DTEND;TZID=America/New_York:20231114T120000
DTSTAMP:20260501T113113
CREATED:20240223T052212Z
LAST-MODIFIED:20240223T052212Z
UID:10002814-1699959600-1699963200@cmsa.fas.harvard.edu
SUMMARY:Quasi-Local Mass in a Binary Black Hole Merger
DESCRIPTION:General Relativity Seminar \nSpeaker: Daniel Kolb (Max Planck Institute) \nTitle: Quasi-Local Mass in a Binary Black Hole Merger \nAbstract: One of the major open problems in classical general relativity is how one should define the mass of a finite region of space. In this talk\, we will investigate a promising definition proposed by Wang and Yau in 2009. A closed 2-surface bounding the region of interest is embedded isometrically into Minkowski space. The mass is then calculated by comparing the extrinsic geometries. The Wang-Yau mass has many desirable properties\, but it has previously not been calculated for surfaces in dynamical spacetimes. To remedy this\, we will discuss how the Wang-Yau mass can be computed in practice and extend the definition to surfaces important in black hole dynamics: their quasi-local horizons. Finally\, we look at how this mass behaves in a merger of black holes.
URL:https://cmsa.fas.harvard.edu/event/gr_111423/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231107T110000
DTEND;TZID=America/New_York:20231107T120000
DTSTAMP:20260501T113113
CREATED:20240223T052707Z
LAST-MODIFIED:20240223T052707Z
UID:10002816-1699354800-1699358400@cmsa.fas.harvard.edu
SUMMARY:Fluid stabilization in slowly expanding cosmological spacetime
DESCRIPTION:General Relativity Seminar \nSpeaker: David Fajman (Vienna) \nTitle: Fluid stabilization in slowly expanding cosmological spacetime \nAbstract: Relativistic fluids are known to form shocks during their evolution from near-homogeneous initial data. In expanding spacetimes\, shock formation is suppressed\, if the expansion is sufficiently strong. We refer to this effect as fluid stabilization. The occurrence of this phenomenon depends on features of the fluid and has implications for our understanding of structure formation and cosmological evolution. While the effect is well studied in the regime of accelerated expansion\, in recent years it has been shown that fluid stabilization occurs as well in spacetimes with slower expansion rates. In this talk we present different recent results on fluid stabilization in slowly expanding spacetimes and aspects of the methods involved in the respective proofs. \n  \nTalk via Zoom\, broadcast in G10 \n 
URL:https://cmsa.fas.harvard.edu/event/gr_11723/
LOCATION:Hybrid – G10
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-11.07.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231024T110000
DTEND;TZID=America/New_York:20231024T120000
DTSTAMP:20260501T113113
CREATED:20240223T053357Z
LAST-MODIFIED:20240223T053357Z
UID:10002817-1698145200-1698148800@cmsa.fas.harvard.edu
SUMMARY:Resolving memory in numerical relativity\, and fixing BMS frames for modeling
DESCRIPTION:General Relativity Seminar \nSpeaker: Leo Stein (Mississippi) \nTitle: Resolving memory in numerical relativity\, and fixing BMS frames for modeling \nAbstract: Numerical relativity waveforms serve as ground truth for detection and parameter estimation of binary black hole mergers. Most NR waveforms to date miss memory effects\, as they were extracted from simulations using an approximation called extrapolation. I will report on the SXS collaboration’s capacity to resolve memory effects in production NR simulations using Cauchy-characteristic evolution (CCE)\, and in the future with Cauchy-characteristic matching (CCM). I will further report on how BH perturbation and post-Newtonian theory furnish natural BMS frames. With these BMS frames\, we can extract well-defined remnant quantities\, perform precision ringdown modeling\, and build complete surrogate waveform models that capture memory effects.
URL:https://cmsa.fas.harvard.edu/event/gr_102423/
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231010T110000
DTEND;TZID=America/New_York:20231010T120000
DTSTAMP:20260501T113113
CREATED:20240223T054233Z
LAST-MODIFIED:20240223T054233Z
UID:10002819-1696935600-1696939200@cmsa.fas.harvard.edu
SUMMARY:Tidal Squeezing of Black Holes
DESCRIPTION:General Relativity Seminar \nSpeaker: Maria Rodriguez (Utah) \nTitle: Tidal Squeezing of Black Holes \nAbstract: Recent developments indicate that Kerr black holes do not deform when perturbed by a static external gravitational field. Relying on hidden symmetries\, compelling progress has been achieved to explain that Love numbers for Kerr black holes vanish. How does the phenomenon of tidal squeezing manifest in broader contexts? An elementary presentation of dynamical tidal squeezing of Kerr black holes will be given.
URL:https://cmsa.fas.harvard.edu/event/gr_101023/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-10.10.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231003T110000
DTEND;TZID=America/New_York:20231003T120000
DTSTAMP:20260501T113113
CREATED:20240223T054715Z
LAST-MODIFIED:20240223T054715Z
UID:10002820-1696330800-1696334400@cmsa.fas.harvard.edu
SUMMARY:A Smooth Horizon without a Smooth Horizon
DESCRIPTION:General Relativity Seminar \nSpeaker: Chethan Krishnan (IISc Bangalore) \nTitle: A Smooth Horizon without a Smooth Horizon \nAbstract: I will talk about some work that is about to appear\, where we note one precise way in which the stretched horizon can simulate a smooth horizon. I will also make an effort to put things in some perspective (brickwalls\, fuzzballs\, Type I algebras\,…)
URL:https://cmsa.fas.harvard.edu/event/gr_10323/
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230926T110000
DTEND;TZID=America/New_York:20230926T120000
DTSTAMP:20260501T113113
CREATED:20240223T104632Z
LAST-MODIFIED:20240813T160129Z
UID:10002850-1695726000-1695729600@cmsa.fas.harvard.edu
SUMMARY:Geometry at Strong coupling for amplitudes/Wilson loops
DESCRIPTION:General Relativity Seminar \nSpeaker: Lionel Mason (Oxford) \nTitle: Geometry at Strong coupling for amplitudes/Wilson loops \nAbstract: The amplitude/Wilson loop correspondence identifies planar N=4 super-Yang-Mills amplitudes with certain null polygonal Wilson loops at all the values of the coupling. At strong coupling this equates the amplitude/Wilson loop computed by Alday & Maldacena in terms of the area of a minimal surface in AdS_5. To do so they developed a `Y-system’ for computing the amplitude. This talk re-interprets their construction as providing the underlying twistor space for a hyperKahler structure on the corresponding space of kinematic data. In particular\, the area is given by a Kahler scalar for the pseudo-hyperkahler structure and satisfies a version of the Plebanski equations\, a well-known completely integrable system. This geometry encodes the properties of the space of kinematic data on which the amplitude depends as a cluster variety tying into its positive geometry and cluster variety structure. Similar constructures are possible for other cluster varieties corresponding to form factors and beyond.
URL:https://cmsa.fas.harvard.edu/event/gr_92623/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.26.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230919T110000
DTEND;TZID=America/New_York:20230919T120000
DTSTAMP:20260501T113113
CREATED:20240223T101246Z
LAST-MODIFIED:20240223T101246Z
UID:10002846-1695121200-1695124800@cmsa.fas.harvard.edu
SUMMARY:Quantization of causal diamonds in 2+1 dimensional gravity
DESCRIPTION:General Relativity Seminar \nSpeaker: Rodrigo Silva\, University of Maryland \nTitle: Quantization of causal diamonds in 2+1 dimensional gravity \nAbstract: We develop the reduced phase space quantization of causal diamonds in $2+1$ dimensional gravity with a nonpositive cosmological constant. The system is defined as the domain of dependence of a spacelike topological disk with a fixed boundary metric. By solving the constraints in a constant-mean-curvature time gauge and removing all the spatial gauge redundancy\, we find that the phase space is the cotangent bundle of $Diff^+(S^1)/PSL(2\, \mathbb{R})$\, i.e.\, the group of orientation-preserving diffeomorphisms of the circle modulo the projective special linear subgroup. Classically\, the states correspond to causal diamonds embedded in $AdS_3$ (or $Mink_3$ if $\Lambda = 0$)\, with a fixed corner length\, that has the topological disk as a Cauchy surface. Because this phase space does not admit a global system of coordinates\, a generalization of the standard canonical (coordinate) quantization is required — in particular\, since the configuration space is a homogeneous space for a Lie group\, we apply Isham’s group-theoretic quantization scheme. The Hilbert space of the associated quantum theory carries an irreducible unitary representation of the $BMS_3$ group and can be realized by wavefunctions on a coadjoint orbit of Virasoro with labels in irreducible unitary representations of the corresponding little group. A surprising result is that the twist of the diamond boundary loop is quantized in terms of the ratio of the Planck length to the corner length. \n 
URL:https://cmsa.fas.harvard.edu/event/gr_91923/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.19.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230912T110000
DTEND;TZID=America/New_York:20230912T120000
DTSTAMP:20260501T113113
CREATED:20240223T102522Z
LAST-MODIFIED:20240223T102522Z
UID:10002847-1694516400-1694520000@cmsa.fas.harvard.edu
SUMMARY:Pole skipping\, quasinormal modes\, shockwaves and their connection to chaos
DESCRIPTION:General Relativity Seminar \nSpeaker: Diandian Wang(Harvard University) \nTitle: Pole skipping\, quasinormal modes\, shockwaves and their connection to chaos \nAbstract: A chaotic quantum system can be studied using the out-of-time-order correlator (OTOC). I will tell you about pole skipping — a recently discovered feature of the retarded Green’s function — that seems to also know things: things like the Lyapunov exponent and the butterfly velocity\, which are important quantifiers of the OTOC. Then I will talk about a systematic way of deriving pole-skipping conditions for general holographic CFTs dual to classical bulk theories and how to use this framework to derive a few interesting statements including: (1) theories with higher spins generally violate the chaos bound; (2) the butterfly velocity calculated using pole skipping agrees with that calculated using shockwaves for arbitrary higher-derivative gravity coupled to ordinary matter; (3) shockwaves are related to a special type of quasinormal modes. As we will see\, the techniques are entirely classically gravitational\, which I will go through with a certain level of details.
URL:https://cmsa.fas.harvard.edu/event/gr_91223/
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-09.12.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230705T140000
DTEND;TZID=America/New_York:20230705T150000
DTSTAMP:20260501T113113
CREATED:20230818T045528Z
LAST-MODIFIED:20240215T112411Z
UID:10001127-1688565600-1688569200@cmsa.fas.harvard.edu
SUMMARY:Grey Galaxy’ as the endpoint of the Kerr-AdS super radiant blackhole
DESCRIPTION:General Relativity Seminar \nSpeaker: Suman Kundu (Weizmann Institute) \nTitle: ‘Grey Galaxy’ as the endpoint of the Kerr-AdS super radiant blackhole \nAbstract: Kerr AdS$_{d+1}$ black holes for $d\geq 3$ suffer from classical superradiant instabilities over a range of masses near extremality. We conjecture that these instabilities settle down into Grey Galaxies (GG)s – a new class of solutions to Einstein’s equations which we construct for $d=3$. Grey Galaxies consist of an $\omega=1$ black hole in the `centre’ of $AdS$\, surrounded by a uniformly thick and very large disk of thermal bulk matter that revolves around the centre of AdS at the speed of light. The parametrically low energy density and parametrically large radius of the gas disk are inversely related; as a consequence\, the gas carries a finite fraction of the total energy. Grey Galaxy saddles exist at masses that extend all the way down to the unitarity bound. Their thermodynamics is that of a weakly interacting mix of Kerr AdS black holes and the gas. In addition to a smooth piece\, the boundary stress tensor of these solutions includes a contribution from a delta function localized at the `equator’ of the boundary sphere\, a term which may be used as an order parameter that sharply distinguishes GG solutions from ordinary Kerr-Black hole saddles. We also construct `Revolving Black Hole (RBH) saddles’\,  macroscopically charged $SO(d\,2)$ descendants of AdS-Kerr solutions\, that describe black holes revolving around the centre of $AdS$\, at the fixed radial location but in a quantum wave function in the angular directions. RBH saddles turn out to be (marginally) entropically subdominant to GG saddles. We argue that supersymmetric versions of RBH saddles exist and have interesting consequences for the spectrum of SUSY states in\, e.g.  ${\cal N}=4$ Yang-Mills theory.
URL:https://cmsa.fas.harvard.edu/event/gr_7523/
LOCATION:Jefferson 453\, 17 Oxford St\, Cambridge\, MA 02138\, MA
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230511T133000
DTEND;TZID=America/New_York:20230511T143000
DTSTAMP:20260501T113113
CREATED:20230818T045112Z
LAST-MODIFIED:20240215T111322Z
UID:10001264-1683811800-1683815400@cmsa.fas.harvard.edu
SUMMARY:Positivity of Static quasi-local Mass in general relativity
DESCRIPTION:General Relativity Seminar \nSpeaker: Aghil Alaee\, Clark University \nTitle: Positivity of Static quasi-local Mass in general relativity \nAbstract: In this talk\, we review results on the PMT of quasi-local masses and prove the positivity of static quasi-local masses with respect to the AdS and AdS Schwarzschild spacetimes.
URL:https://cmsa.fas.harvard.edu/event/gr_51123/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-05.11.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230504T093000
DTEND;TZID=America/New_York:20230504T103000
DTSTAMP:20260501T113113
CREATED:20230818T044217Z
LAST-MODIFIED:20240228T073615Z
UID:10001263-1683192600-1683196200@cmsa.fas.harvard.edu
SUMMARY:Testing GR with GWs
DESCRIPTION:General Relativity Seminar \nSpeaker: Vitor Cardoso\, IST\, Lisbon and The Niels Bohr Institute\, Copenhagen \nTitle: Testing GR with GWs \nAbstract: One of the most remarkable possibilities of General Relativity concerns gravitational collapse to black holes\, leaving behind a geometry with light rings\, ergoregions and horizons. These peculiarities are responsible for uniqueness properties and energy extraction mechanisms that turn black holes into ideal laboratories of strong gravity\, of particle physics (yes!) and of possible quantum-gravity effects. I will discuss some of the latest progress in tests of General Relativity with black holes.
URL:https://cmsa.fas.harvard.edu/event/gr_5423/
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-05.04.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230427T103000
DTEND;TZID=America/New_York:20230427T113000
DTSTAMP:20260501T113113
CREATED:20230818T043803Z
LAST-MODIFIED:20240119T052918Z
UID:10001262-1682591400-1682595000@cmsa.fas.harvard.edu
SUMMARY:The localized seed-to-solution method for the Einstein constraints
DESCRIPTION:General Relativity Seminar \nSpeaker: Philippe G. LeFloch\, Sorbonne University and CNRS \nTitle: The localized seed-to-solution method for the Einstein constraints \nAbstract: I will discuss advances on asymptotically Euclidian initial data sets and the variational method introduced by J. Corvino and R. Schoen. This talk is based on joint papers with The-Cang Nguyen (Montpellier) and Bruno Le Floch (Sorbonne Univ. and CNRS). In the vicinity of any given reference data set\, we define a “localized seed-to-solution” map\, which allows us to parametrize the initial data sets satisfying the Einstein constraints (possibly with matter fields). The parametrization is defined over classes of data sets understood modulo the image of the dual linearized constraints. Our main contribution concerns the sharp behavior of solutions at infinity\, which we can arbitrarily localize in asymptotic cones in the sense of A. Carlotto and R. Schoen. Most importantly\, as we prove it\, the solutions enjoy sharp decay estimates at the harmonic and super-harmonic levels. In the course of this analysis\, we discover the notion of ‘asymptotic modulators’\, as we call them\, or “correctors” to the standard ADM invariants.
URL:https://cmsa.fas.harvard.edu/event/gr_42723/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-04.27.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230424T133000
DTEND;TZID=America/New_York:20230424T143000
DTSTAMP:20260501T113113
CREATED:20230818T043218Z
LAST-MODIFIED:20240119T052608Z
UID:10001261-1682343000-1682346600@cmsa.fas.harvard.edu
SUMMARY:Recent advances in scalar curvature and positive mass theorems
DESCRIPTION:General Relativity Seminar \nSpeaker: Tin Yau Tsang\, University of California Irvine \nTitle: Recent advances in scalar curvature and positive mass theorems\n\nAbstract:  First\, we have a review of classical tools for studying scalar curvature and positive mass theorem. Then we are going to discuss some advances and new perspectives on these tools which lead to a deeper understanding of geometry and initial data sets.
URL:https://cmsa.fas.harvard.edu/event/gr_42423/
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-04.24.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230413T093000
DTEND;TZID=America/New_York:20230413T103000
DTSTAMP:20260501T113113
CREATED:20230818T042744Z
LAST-MODIFIED:20240228T081413Z
UID:10001260-1681378200-1681381800@cmsa.fas.harvard.edu
SUMMARY:Resolving the photon ring
DESCRIPTION:General Relativity Seminar \nSpeaker: Shahar Hadar (University of Haifa) \nTitle: Resolving the photon ring \nAbstract: In the past few years\, the Event Horizon Telescope has released the first close-up interferometric images of two supermassive black holes\, M87* and SgrA*. It is believed that within these images is embedded a fine\, yet-unresolved brightness enhancement called the photon ring. The ring is a universal consequence of strong lensing by the black hole and thereby conveys information on its spacetime geometry\, potentially providing a new independent avenue for tests of general relativity in the strong-field regime. In the talk I will briefly review the theory of the photon ring and its corresponding spacetime region\, the photon shell\, which governs the universal lensing structure. I will then describe some current efforts and future prospects for resolving the ring\, which include both the construction of transformative new instruments and the development of novel analysis methods. Focusing on the latter\, I will present an upcoming proposal to use spectro-temporal autocorrelations in signals emitted from black hole environs as a probe of strong lensing effects.
URL:https://cmsa.fas.harvard.edu/event/gr_41323/
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-04.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230406T093000
DTEND;TZID=America/New_York:20230406T103000
DTSTAMP:20260501T113113
CREATED:20230818T042449Z
LAST-MODIFIED:20240119T051939Z
UID:10001259-1680773400-1680777000@cmsa.fas.harvard.edu
SUMMARY:Rough solutions of the relativistic Euler equations
DESCRIPTION:General Relativity Seminar \nSpeaker: Sifan Yu\, Vanderbilt University \nTitle: Rough solutions of the relativistic Euler equations \nAbstract: I will discuss recent works on the relativistic Euler equations with dynamic vorticity and entropy. We use a new formulation of the equations\, which has geo-analytic structures. In this geometric formulation\, we decompose the flow into geometric “sound-wave part” and “transport-div-curl part”. This allows us to derive sharp results about the dynamics\, including the existence of low-regularity solutions. Then\, I will discuss the results of rough solutions of the relativistic Euler equations and the role that nonlinear geometric optics plays in the framework. Our main result is that the Sobolev norm $H^{2+}$ of the variables in the “wave-part” and the H\”older norm $C^{0\,0+}$ of the variables in the “transport-part” can be controlled in terms of initial data for short times. We note that the Sobolev norm assumption $H^{2+}$ is the optimal result for the variables in the “wave-part.” This talk will include the main ideas of the proof\, as well as a comparison of the relativistic and non-relativistic scenarios.
URL:https://cmsa.fas.harvard.edu/event/gr_4623/
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:20230330T093000
DTEND;TZID=America/New_York:20230330T223000
DTSTAMP:20260501T113113
CREATED:20230818T042141Z
LAST-MODIFIED:20240118T101402Z
UID:10001258-1680168600-1680215400@cmsa.fas.harvard.edu
SUMMARY:Gravitational perturbations near to extreme Kerr
DESCRIPTION:General Relativity Seminar \nSpeaker: Alejandra Castro (University of Cambridge) \nTitle: Gravitational perturbations near to extreme Kerr \nAbstract: Gravitational perturbations of a black hole illustrate the invaluable synergy between theory\, experiment\, and numerical simulations in general relativity. A recent development in the theory side has been the identification of the relevant degrees of freedom describing the low energy physics driving a black hole away from extremality.  For simple cases\, this low energy sector determines important aspects of the gravitational backreaction\, and several properties that are key to our microscopic (quantum) understanding of black hole physics.\n\nIn this talk I will discuss these developments in the context of the (near-)extreme Kerr black hole. In particular\, I will revisit the spectrum of linear axisymmetric gravitational perturbations of this black hole. The aim is to characterise those perturbations that are responsible for the deviations away from extremality\, and to contrast them with the linearized perturbations treated in the Newman-Penrose formalism. I will show that for Kerr the low-lying mode sector is subtle and intricate—features that their charged spherical symmetric cousins do not display. This unveils new clues on how to decode a microscopic\, and holographic\, understanding of the Kerr black hole.
URL:https://cmsa.fas.harvard.edu/event/gr_33023/
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-03.30.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230323T133000
DTEND;TZID=America/New_York:20230323T143000
DTSTAMP:20260501T113113
CREATED:20230818T041454Z
LAST-MODIFIED:20240118T100327Z
UID:10001257-1679578200-1679581800@cmsa.fas.harvard.edu
SUMMARY:New Phases of N=4 SYM
DESCRIPTION:General Relativity Seminar \nSpeaker: Prahar Mitra (University of Cambridge) \nTitle: New Phases of N=4 SYM \nAbstract: We construct new static solutions to gauged supergravity that\, via the AdS/CFT correspondence\, are dual to thermal phases in N=4 SYM at finite chemical potential. These solutions dominate the micro-canonical ensemble and are required to ultimately reproduce the microscopic entropy of AdS black holes. These are constructed in two distinct truncations of gauged supergravity and can be uplifted to solutions of type IIB supergravity. Together with the known phases of the truncation with three equal charges\, our findings permit a good understanding of the full phase space of SYM thermal states with three arbitrary chemical potentials. We will also discuss the status of hairy supersymmetric black hole solutions in this theory. \nBased on: https://arxiv.org/pdf/2207.07134.pdf [hep-th]
URL:https://cmsa.fas.harvard.edu/event/gr_32323/
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-03.23.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230309T093000
DTEND;TZID=America/New_York:20230309T103000
DTSTAMP:20260501T113113
CREATED:20230817T185018Z
LAST-MODIFIED:20240228T091310Z
UID:10001256-1678354200-1678357800@cmsa.fas.harvard.edu
SUMMARY:Pseudospectrum and black hole quasinormal mode instability: An ultraviolet universality conjecture
DESCRIPTION:General Relativity Seminar \nSpeaker: Jose Luis Jaramillo (Bourgogne U.) \nTitle: Pseudospectrum and black hole quasinormal mode instability: an ultraviolet universality conjecture \nAbstract: Can we measure the ‘effective regularity’ of spacetime from the perturbation of quasi-normal mode (QNM) overtones? Black hole (BH) QNMs encode the resonant response of black holes under linear perturbations\, their associated complex frequencies providing an invariant probe into the background spacetime geometry. In the late nineties\, Nollert and Price found evidence of a BH QNM instability phenomenon\, according to which perturbed QNMs of Schwarzschild spacetime migrate to new perturbed branches of different qualitative behaviour and asymptotics. Here we revisit this BH QNM instability issue by adopting a pseudospectrum approach. Specifically\, we cast the QNM problem as an eigenvalue problem for a non-selfadjoint operator by adopting a hyperboloidal formulation of spacetime. Non-selfadjoint (more generally non-normal) operators suffer potentially of spectral instabilities\, the notion of pseudospectrum providing a tool suitable for their study. We find evidence that perturbed Nollert & Price BH QNMs track the pseudospectrum contour lines\, therefore probing the analytic structure of the resolvent\, showing the following (in)stability behaviour: i) the slowest decaying (fundamental) mode is stable\, whereas ii) (all) QNM overtones are ultraviolet unstable (for sufficiently high frequency). Building on recent work characterizing Burnett’s conjecture as a low-regularity problem in general relativity\, we conjecture that (in the infinite-frequency limit) generic ultraviolet spacetime perturbations make BH QNMs migrate to ‘Regge QNM branches’ with a precise universal logarithmic pattern. This is a classical general relativity (effective) low-regularity phenomenon\, agnostic to possible detailed (quantum) descriptions of gravity at higher-energies and potentially observationally accessible.
URL:https://cmsa.fas.harvard.edu/event/gr_3923/
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-03.09.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230223T093000
DTEND;TZID=America/New_York:20230223T103000
DTSTAMP:20260501T113113
CREATED:20230817T184650Z
LAST-MODIFIED:20240118T093227Z
UID:10001255-1677144600-1677148200@cmsa.fas.harvard.edu
SUMMARY:Formation of trapped surfaces in the Einstein-Yang-Mills system
DESCRIPTION:General Relativity Seminar \nSpeaker: Nikolaos Athanasiou (University of Crete\, Greece) \nTitle: Formation of trapped surfaces in the Einstein-Yang-Mills system \nAbstract: The purpose of this talk is to give an overview of a semi-global existence result and a trapped surface formation results in the context of the Einstein-Yang-Mills system. Adopting a “signature for decay rates” approach first introduced by An\, we develop a novel gauge (and scale) invariant hierarchy of non-linear estimates for the Yang-Mills curvature which\, together with the estimates for the gravitational degrees of freedom\, yield the desired semi-global existence result. Once semi-global existence has been established\, we will explain how the formation of a trapped surface follows from a standard ODE argument. This is joint work with Puskar Mondal and Shing-Tung Yau.
URL:https://cmsa.fas.harvard.edu/event/gr_22323/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-02.23.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230216T133000
DTEND;TZID=America/New_York:20230216T143000
DTSTAMP:20260501T113113
CREATED:20230817T183826Z
LAST-MODIFIED:20240118T092821Z
UID:10001254-1676554200-1676557800@cmsa.fas.harvard.edu
SUMMARY:Quasinormal Modes from Penrose Limits
DESCRIPTION:General Relativity Seminar \nSpeaker: Kwinten Fransen (UC Santa Barbara) \nTitle: Quasinormal Modes from Penrose Limits \nAbstract: In this talk\, I will explain how to describe quasinormal modes with large real frequencies using Penrose limits. To do so\, I first recall relevant aspects of the Penrose limit\, and its resulting plane wave spacetimes\, as well as quasinormal modes to subsequently tie these together. Having established the main principle\, I will illustrate the usefulness of this point of view with the geometric realization of the emergent symmetry algebra underlying the quasinormal modes in the large real frequency limit and present its application to the astrophysically important example of Kerr black holes. Based on arXiv:2301.06999.
URL:https://cmsa.fas.harvard.edu/event/gr_21623/
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-02.16.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230209T133000
DTEND;TZID=America/New_York:20230209T143000
DTSTAMP:20260501T113113
CREATED:20230817T183342Z
LAST-MODIFIED:20240215T100720Z
UID:10001253-1675949400-1675953000@cmsa.fas.harvard.edu
SUMMARY:Quasinormal modes and Ruelle resonances: mathematician's perspective
DESCRIPTION:General Relativity Seminar \nSpeaker: Maciej Zworski\, UC Berkeley \nTitle: Quasinormal modes and Ruelle resonances: mathematician’s perspective \nAbstract: Quasinormal modes of gravitational waves and Ruelle resonances in hyperbolic classical dynamics share many general properties and can be considered “scattering resonances”: they appear in expansions of correlations\, as poles of Green functions and are associated to trapping of trajectories (and are both notoriously hard to observe in nature\, unlike\, say\, quantum resonances in chemistry or scattering poles in acoustical scattering). I will present a mathematical perspective that also includes zeros of the Riemann zeta function (scattering resonances for the Hamiltonian given by the Laplacian on the modular surface) and stresses the importance of different kinds of trapping phenomena\, resulting\, for instance\, in fractal counting laws for resonances.
URL:https://cmsa.fas.harvard.edu/event/gr_2023/
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-02.09.23.png
END:VEVENT
END:VCALENDAR