BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CMSA - ECPv6.15.20//NONSGML v1.0//EN CALSCALE:GREGORIAN METHOD:PUBLISH X-ORIGINAL-URL:https://cmsa.fas.harvard.edu X-WR-CALDESC:Events for CMSA REFRESH-INTERVAL;VALUE=DURATION:PT1H X-Robots-Tag:noindex X-PUBLISHED-TTL:PT1H BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20210314T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20211107T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20220313T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20221106T060000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20230312T070000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20231105T060000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTART;TZID=America/New_York:20220310T130000 DTEND;TZID=America/New_York:20220310T140000 DTSTAMP:20260601T060753 CREATED:20240214T080539Z LAST-MODIFIED:20240813T160832Z UID:10002579-1646917200-1646920800@cmsa.fas.harvard.edu SUMMARY:The Einstein-flow on manifolds of negative curvature DESCRIPTION:Abstract: We consider the Cauchy problem for the Einstein equations for cosmological spacetimes\, i.e. spacetimes with compact spatial hypersurfaces. Various classes of those dynamical spacetimes have been constructed and analyzed using CMC foliations or equivalently the CMC-Einstein flow. We will briefly review the Andersson-Moncrief stability result of negative Einstein metrics under the vacuum Einstein flow and then present various recent generalizations to the nonvacuum case. We will emphasize what difficulties arise in those generalizations\, how they can be handled depending on the matter model at hand\, and what implications we can draw from these results for cosmology. We then turn to a scenario where the CMC Einstein flow leads to a large data result in 2+1-dimensions. URL:https://cmsa.fas.harvard.edu/event/3-10-2022-general-relativity-seminar/ LOCATION:MA CATEGORIES:General Relativity Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-03.10.22.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20220321T130000 DTEND;TZID=America/New_York:20220321T140000 DTSTAMP:20260601T060753 CREATED:20240214T081657Z LAST-MODIFIED:20240813T160939Z UID:10002584-1647867600-1647871200@cmsa.fas.harvard.edu SUMMARY:Bulk-boundary correspondence for vacuum asymptotically Anti-de Sitter spacetimes DESCRIPTION:Abstract: The AdS/CFT conjecture in physics posits the existence of a correspondence between gravitational theories in asymptotically Anti-de Sitter (aAdS) spacetimes and field theories on their conformal boundary. In this presentation\, we prove rigorous mathematical statements toward this conjecture. \nIn particular\, we show there is a one-to-one correspondence between aAdS solutions of the Einstein-vacuum equations and a suitable space of data on the conformal boundary (consisting of the boundary metric and the boundary stress-energy tensor). We also discuss consequences of this result\, as well as the main ingredient behind its proof: a unique continuation property for wave equations on aAdS spacetimes. \nThis is joint work with Gustav Holzegel (and makes use of joint works with Alex McGill and Athanasios Chatzikaleas). URL:https://cmsa.fas.harvard.edu/event/3-21-2022-general-relativity-seminar/ LOCATION:MA CATEGORIES:General Relativity Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-03.21.22.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20220324T093000 DTEND;TZID=America/New_York:20220324T103000 DTSTAMP:20260601T060753 CREATED:20240214T082228Z LAST-MODIFIED:20240301T113314Z UID:10002585-1648114200-1648117800@cmsa.fas.harvard.edu SUMMARY:Rough solutions of the $3$-D compressible Euler equations DESCRIPTION:Abstract: I will talk about my work on the compressible Euler equations. We prove the local-in-time existence the solution of the compressible Euler equations in $3$-D\, for the Cauchy data of the velocity\, density and vorticity $(v\,\varrho\, \omega) \in H^s\times H^s\times H^{s’}$\, $22$. At the opposite extreme\, in the incompressible case\, i.e. with a constant density\,  the result is known to hold for $\omega\in H^s$\, $s>3/2$ and fails for $s\le 3/2$\, see the work of Bourgain-Li. It is thus natural to conjecture that the optimal result should be  $(v\,\varrho\, \omega) \in H^s\times H^s\times H^{s’}$\, $s>2\, \\, s’>\frac{3}{2}$. We view our work as an important step in proving the conjecture. The main difficulty in establishing sharp well-posedness results for general compressible Euler flow is due to the highly nontrivial interaction between the sound waves\, governed by quasilinear wave equations\, and vorticity which is transported by the flow. To overcome this difficulty\, we separate the dispersive part of a sound wave from the transported part and gain regularity significantly by exploiting the nonlinear structure of the system and the geometric structures of the acoustic spacetime. URL:https://cmsa.fas.harvard.edu/event/3-24-2022-general-relativity-seminar/ LOCATION:MA CATEGORIES:General Relativity Seminar ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-GR-Seminar-03.24.22-2.png END:VEVENT BEGIN:VEVENT DTSTART;TZID=America/New_York:20220328T130000 DTEND;TZID=America/New_York:20220328T140000 DTSTAMP:20260601T060753 CREATED:20240214T082503Z LAST-MODIFIED:20240301T113123Z UID:10002586-1648472400-1648476000@cmsa.fas.harvard.edu SUMMARY:Black Hole Spectroscopy DESCRIPTION:Abstract: According to general relativity\, the remnant of a binary black hole merger should be a perturbed Kerr black hole. Perturbed Kerr black holes emit “ringdown” radiation which is well described by a superposition of quasinormal modes\, with frequencies and damping times that depend only on the mass and spin of the remnant. Therefore the observation of gravitational radiation emitted by black hole mergers might finally provide direct evidence of black holes with the same certainty as\, say\, the 21 cm line identifies interstellar hydrogen. I will review the current status of this “black hole spectroscopy” program. I will focus on two important open issues: (1) When is the waveform well described by linear black hole perturbation theory? (2) What is the current observational status of black hole spectroscopy? URL:https://cmsa.fas.harvard.edu/event/3-28-2022-general-relativity-seminar/ LOCATION:MA CATEGORIES:General Relativity Seminar END:VEVENT END:VCALENDAR