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DTSTART:20191103T020000
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UID:calendar.1228581.field_date.0@bhi.fas.harvard.edu
DTSTAMP:20200803T153402Z
DESCRIPTION:\n Pengyu Le (U. of Michigan)\n\n\n\n Title: \;On the Penrose
inequality\n\n\n\n \;\n\n\n\n Abstract: \;The Penrose inequality i
s a far reaching inequality in GR proposed by Penrose in 1973. It conjectu
res a simple relation between the total mass of the spacetime and the mass
of any black hole inside it. The original reasoning supporting this inequ
ality by Penrose relates it to some of the most important and difficult pr
oblems in GR\, i.e. the final state of evolution of black holes and naked
singularity (the weak cosmic censorship conjecture). A major breakthrough
was achieved independently by Huisken\, Ilmanen and by Bray. They proved a
very general case of the inequality\, i.e. the Riemannian Penrose inequal
ity. The Riemannian Penrose inequality is of course not the end of the sto
ry. There are versions of the inequality on general initial data sets and
on null hypersurfaces\, and also stronger versions involving electric char
ge and angular momentum\, which are still widely open. The speaker will pr
esent his recent work confirming the Penrose inequality on null hypersurfa
ces in a perturbed Schwarzschild spacetime.\n\n\n\n \;\n\n\n\n Jim Braa
tz (NRAO)\n\n\n\n Title: Measuring Black Hole Masses and the Hubble Constan
t with H2O Megamasers\n\n\n\n Abstract: Water vapor maser emission is detec
ted in the circumnuclear\, edge-on accretiondisks of about 30 nearby activ
e galaxies. \;These masers orbit within a parsec of the central super
massive black hole and reveal Keplerian rotation profiles. \;They prov
ide the only means of directly mapping the sub-parsec accretion disks in A
GNs\, and give gold-standard masses for the supermassive black holes. &nbs
p\;In a few cases\, they can be used to determine angular size distances t
o the host galaxies\, allowing a geometric measurement of the Hubble Const
ant. \;In this talk\, I will describe progress in discovering and map
ping these maser systems\, highlight the significance of determining the H
ubble constant using a geometric\, one-step measurement\, and discuss pros
pects for using ALMA and the ngVLA to expand on studies of megamasers.\n\n
\n\n Alfredo Guevara (Perimeter Institute)\n\n\n\n Title: Classical Spinning
Black Holes and Quantum Field Theory AmplitudesAbstract: Following the ad
vent of LIGO measurements\, it has been observed that Quantum Field Theory
amplitudes can be used to derive physical observables appearing in a clas
sical scattering of two black holes\, or even more general compact objects
. Such observables can be computed to high orders in perturbation theory a
nd can be nicely mapped to the Post-Newtonian or Post-Minkowskian treatmen
t of the binary inspiral problem. In this talk we will outline recent prog
ress in this direction focusing on the case of two spinning black holes. F
or this we first show how amplitudes unveil new structures inside the Kerr
solution\, which simplify aspects such as the multipole expansion or grav
itational radiation.\n\n
DTSTART;TZID=America/New_York:20191112T133000
DTEND;TZID=America/New_York:20191112T143000
LAST-MODIFIED:20191029T205651Z
LOCATION:BHI Meeting Room
SUMMARY:BHI Colloquium
URL;TYPE=URI:https://bhi.fas.harvard.edu/event/bhi-colloquium-8
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