BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Sharmila Gunasekaran (Memorial University of Newfoundland) DTSTART:20200729T160000Z DTEND:20200729T163000Z DTSTAMP:20260422T225722Z UID:general-relativity/1 DESCRIPTION:Title: Slow decay of waves in gravitational solitons\nby Sharmila Gunasekaran (Memorial University of Newfoundland) as part of Atlantic Gene ral Relativity 2020 Online Postdoc/Student Seminar Series\n\n\nAbstract\nG ravitational solitons are globally stationary horizonless asymptotically f lat spacetimes. In this talk\, I will describe the methodology used to pro ve that massless scalar waves in a particular family of soliton spacetimes decay very slowly. The proof involves the construction of quasimodes whic h are approximate solutions to the wave equation. This slow decay can be a ttributed to the stable trapping of null geodesics and is suggestive of in stability at the nonlinear level. This is joint work with Hari Kunduri.\n LOCATION:https://researchseminars.org/talk/general-relativity/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert Santacruz (University of New Brunswick) DTSTART:20200729T163000Z DTEND:20200729T170000Z DTSTAMP:20260422T225722Z UID:general-relativity/2 DESCRIPTION:Title: Quantizing gravity is not that hard if you know how: An undergr aduate guide to black holes\nby Robert Santacruz (University of New Br unswick) as part of Atlantic General Relativity 2020 Online Postdoc/Studen t Seminar Series\n\n\nAbstract\nIt is expected that singularities appearin g in GR are to be resolved in a theory of Quantum Gravity. In the context of Loop Quantum Gravity\, the Big Bang singularity is replaced by a bounce and so one would assume that this can be translated into Black Holes. In this talk I will explain you how to find an effective model for Schwarzsch ild black hole by using Loop Quantum Cosmology techniques and\, the best p art is\, you only need Hamiltonian Mechanics!!\n LOCATION:https://researchseminars.org/talk/general-relativity/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Sharmin Akhter (Memorial University of Newfoundland) DTSTART:20200826T163000Z DTEND:20200826T170000Z DTSTAMP:20260422T225722Z UID:general-relativity/3 DESCRIPTION:Title: Rigidity of Marginally Outer Trapped Surfaces in RNdS Spacetime \nby Sharmin Akhter (Memorial University of Newfoundland) as part of A tlantic General Relativity 2020 Online Postdoc/Student Seminar Series\n\n\ nAbstract\nWe investigate the rigidity of MOTS in four dimensional Reissne r-Nordstrom-de Sitter spacetime. This is connected to the study of the fir st order derivative of stability operator (and hence the second derivative of outgoing null expansion). Since the stability operator has a zero eige nvalue in our case\, we use the Lyapunov-Schmidt reduction to establish ri gidity. This is joint work with Dr. Ivan Booth and Dr. Graham Cox.\n LOCATION:https://researchseminars.org/talk/general-relativity/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Kam To Billy Chan (Memorial University of Newfoundland) DTSTART:20200930T160000Z DTEND:20200930T163000Z DTSTAMP:20260422T225722Z UID:general-relativity/4 DESCRIPTION:Title: The Reissner-Nordstrom Near Horizon Geometry is a Tangent Space time\nby Kam To Billy Chan (Memorial University of Newfoundland) as pa rt of Atlantic General Relativity 2020 Online Postdoc/Student Seminar Seri es\n\n\nAbstract\nThe near horizon geometry (NHG) of an extremal Reissner- Nordstrom black hole is obtained in conventional global AdS coordinates an d in the coordinates of the parent spacetime. Geometrical objects\, specif ically Killing vectors and spacetime points\, are mapped from the boundary and horizon of the NHG into the parent spacetime coordinates. The outcome is that the NHG is a tangent spacetime to the extremal Reissner-Nordstrom black hole’s degenerate horizon and that the degenerate horizon does no t bifurcate. A generalization is made for N-dimensional Reissner-Nordstrom black holes. This work is an extension of Sean Stotyn’s A Tale of Two H orizons.\n LOCATION:https://researchseminars.org/talk/general-relativity/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Turkuler Durgut (Memorial University of Newfoundland) DTSTART:20201028T160000Z DTEND:20201028T163000Z DTSTAMP:20260422T225722Z UID:general-relativity/5 DESCRIPTION:Title: Asymptotically Anti-de Sitter Gravitational Solitons\nby Tu rkuler Durgut (Memorial University of Newfoundland) as part of Atlantic Ge neral Relativity 2020 Online Postdoc/Student Seminar Series\n\n\nAbstract\ nIn this talk\, I will consider the stability of asymptotically anti-de Si tter gravitational solitons. These are globally stationary\, asymptoticall y (globally) AdS spacetimes with positive energy but without horizons. I w ill introduce my ongoing project investigating solutions of the linear wav e equation in this class of backgrounds. I will provide analytical express ions for the behavior of the scalar field near the soliton bubble and at s patial infinity. The special BPS (supersymmetric) case will then be examin ed as an example of a solution where stable trapping occurs. This project is joint work with Dr. Hari K. Kunduri and Dr. Robie A. Hennigar.\n LOCATION:https://researchseminars.org/talk/general-relativity/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Jinzhao Wang (Institute of Theoretical Physics\, ETH Zurich) DTSTART:20201125T160000Z DTEND:20201125T163000Z DTSTAMP:20260422T225722Z UID:general-relativity/6 DESCRIPTION:Title: Outer entropy equals Bartnik-Bray inner mass\, and the gravitat ional ant conjecture\nby Jinzhao Wang (Institute of Theoretical Physic s\, ETH Zurich) as part of Atlantic General Relativity 2020 Online Postdoc /Student Seminar Series\n\n\nAbstract\nEntropy and energy are found to be closely tied on our quest for quantum gravity. We point out an interesting connection between the recently proposed outer entropy\, a coarse-grained entropy defined for a compact spacetime domain motivated by the holograph ic duality\, and the Bartnik-Bray quasilocal mass long known in the mathem atics community. In both scenarios\, one seeks an optimal spacetime fill-i n of a given closed\, connected\, spacelike\, codimension-two boundary. We show that for an outer-minimizing mean-convex surface\, the Bartnik-Bray inner mass matches exactly with the irreducible mass corresponding to the outer entropy. The equivalence implies that the area laws derived from the outer entropy are mathematically equivalent as the monotonicity property of the quasilocal mass. It also gives rise to new bounds between entropy a nd the gravitational energy\, which naturally gives the gravitational coun terpart to Wall's ant conjecture. We also observe that the equality can be achieved in a conformal flow of metrics\, which is structurally similar t o the Ceyhan-Faulkner proof of the ant conjecture. We compute the small sp here limit of the outer entropy and it is proportional to the bulk stress tensor as one would expect for a quasilocal mass.\n LOCATION:https://researchseminars.org/talk/general-relativity/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Saikat Mondal (Memorial University of Newfoundland) DTSTART:20201125T163000Z DTEND:20201125T170000Z DTSTAMP:20260422T225722Z UID:general-relativity/7 DESCRIPTION:Title: Marginally outer trapped (open) surfaces in Schwarzschild geome try and extreme mass ratio merger\nby Saikat Mondal (Memorial Universi ty of Newfoundland) as part of Atlantic General Relativity 2020 Online Pos tdoc/Student Seminar Series\n\n\nAbstract\nBlack holes are one of the comm on objects in astrophysics. Some are formed from a dying star\, called a s tellar black hole. There are also supermassive black holes consisting of m ass millions or even billions times that of the sun. Such black holes are thought to lie at the center of almost every galaxy. In this talk we will explore the evolution of horizons of black hole mergers in a special limit called the " extreme mass ratio" limit. For example\, a supermassive blac k hole merges with a stellar black hole to become a single black hole. In this limit\, the merging horizons can be studied with the help of simple n umerics. We will discuss mainly about marginally outer trapped surfaces (M OTS). Interestingly\, the MOTSs we find in our numerical analysis have an arbitrary number of self-intersections.\n LOCATION:https://researchseminars.org/talk/general-relativity/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Sarah Mime MacDonald Muth (Memorial University of Newfoundland) DTSTART:20210224T160000Z DTEND:20210224T170000Z DTSTAMP:20260422T225722Z UID:general-relativity/8 DESCRIPTION:Title: Marginally Outer Trapped (Open) Surfaces in 4+1 Dimensional Sch warzschild\nby Sarah Mime MacDonald Muth (Memorial University of Newfo undland) as part of Atlantic General Relativity 2020 Online Postdoc/Studen t Seminar Series\n\n\nAbstract\nIn the case of binary black hole mergers\, the surface of most obvious interest\, the Event Horizon\, is often compu tationally difficult to locate. Instead\, it is useful to turn to quasi-l ocal characterizations of black hole boundaries\, such as Marginally Outer Trapped Surfaces (MOTS)\, which are defined for a single time slice of th e spacetime\, and the outer-most of which is the apparent horizon. In thi s talk\, I will describe ongoing work focused on understanding MOTS in the interior of a five-dimensional Schwarzschild black hole. Similar to the f our-dimensional case previously studied\, we find examples of self-interse cting MOTS with an arbitrary number of self-intersections. This provides f urther support that self-intersecting behavior is rather generic. I will also briefly discuss the next stage of our research\, which involves furth er examples of these self-intersecting MOTS\, this time in the full Kruska l extension of Schwarzschild.\n LOCATION:https://researchseminars.org/talk/general-relativity/8/ END:VEVENT END:VCALENDAR