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DTSTART;TZID=America/New_York:20240402T110000
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DTSTAMP:20260418T151612
CREATED:20240325T132956Z
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UID:10000830-1712055600-1712059200@cmsa.fas.harvard.edu
SUMMARY:Linearised Second Law for Higher Curvature Gravity and Non-Minimally Coupled Vector Fields
DESCRIPTION:General Relativity Seminar \nSpeaker: Zihan Yan\, Cambridge University \n\n\n\nTitle: Linearised Second Law for Higher Curvature Gravity and Non-Minimally Coupled Vector Fields \n\n\n\nAbstract: Expanding the work of arXiv:1504.08040\, we show that black holes obey a second law for linear perturbations to bifurcate Killing horizons\, in any covariant higher curvature gravity coupled to scalar and vector fields. The vector fields do not need to be gauged\, and (like the scalars) can have arbitrary non-minimal couplings to the metric. The increasing entropy has a natural expression in covariant phase space language\, which makes it manifestly invariant under JKM ambiguities. An explicit entropy formula is given for f(Riemann) gravity coupled to vectors\, where at most one derivative acts on each vector. Besides the previously known curvature terms\, there are three extra terms involving differentiating the Lagrangian by the symmetric vector derivative (which therefore vanish for gauge fields).
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar-3/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-04.02.2024.png
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240416T110000
DTEND;TZID=America/New_York:20240416T120000
DTSTAMP:20260418T151612
CREATED:20240409T163938Z
LAST-MODIFIED:20240502T195940Z
UID:10000832-1713265200-1713268800@cmsa.fas.harvard.edu
SUMMARY:New Well-Posed Boundary Conditions for Semi-Classical Euclidean Gravity
DESCRIPTION:General Relativity Seminar \nSpeaker: Xiaoyi Liu\, UCSB \nTitle: New Well-Posed Boundary Conditions for Semi-Classical Euclidean Gravity \nAbstract: We consider four-dimensional Euclidean gravity in a finite cavity.  We point out that there exists a one-parameter family of boundary conditions\, parameterized by a real constant\, where a suitably Weyl-rescaled boundary metric is fixed\, and all give a well-posed elliptic system\, as opposed to the Dirichlet boundary condition. Focussing on static Euclidean solutions\, we derive a thermodynamic first law. Restricting to a spherical spatial boundary\, the infillings are flat space or the Schwarzschild solution and have similar thermodynamics to the Dirichlet case. We study the stability behavior of several geometries under these boundary conditions in both Euclidean and Lorentzian signatures and find two puzzles.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar_41624/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-04.16.2024.png
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240423T100000
DTEND;TZID=America/New_York:20240423T110000
DTSTAMP:20260418T151612
CREATED:20240415T162430Z
LAST-MODIFIED:20240422T154105Z
UID:10000833-1713866400-1713870000@cmsa.fas.harvard.edu
SUMMARY:Quantum Energy Inequalities
DESCRIPTION:General Relativity Seminar \nSpeaker: Chris Fewster\, York University \nTitle: Quantum Energy Inequalities \nAbstract: Many theorems of mathematical relativity\, including singularity and positive mass theorems\, include the classical energy conditions among their hypotheses. However\, matter described by quantum field theory can violate the classical energy conditions and indeed there is no lower bound to the energy density at a given point as the quantum state is varied. Do the classical theorems apply to quantised matter? \nIn this talk I discuss Quantum Energy Inequalities\, lower bounds on averages of the energy density along timelike curves or over spacetime regions\, that have been proved in QFT and are the remnants of the classical energy conditions after quantisation. I will also discuss some of their consequences.
URL:https://cmsa.fas.harvard.edu/event/general-relativity-seminar_42324/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
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