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SUMMARY:Disc Instability is Dead\, Long Live Disc Instability - Duncan For
 gan (St Andrews)
DTSTART:20160504T143000Z
DTEND:20160504T151500Z
UID:TALK65609@talks.cam.ac.uk
CONTACT:Dr B.-O. Demory
DESCRIPTION:Disc Instability theory proposes that self-gravitating discs f
 ragment\ninto bound objects with masses around the giant planet/brown dwar
 f\nboundary\, which is attractive for explaining planetary systems with\nl
 arge bodies at large semimajor axis.  In its most recent incarnation\,\nTi
 dal Downsizing\, the disc fragments may obtain solid cores through\nsedime
 ntation\, migrate inwards and be tidally stripped\, forming\nobjects with 
 a range of masses and properties.\n\nI will present several investigations
  of disc fragmentation and tidal\ndownsizing\, which include high resoluti
 on radiation hydrodynamic\nsimulations and state-of-the-art semi-analytic 
 population synthesis\nmodels. The combined evidence is clear that disc fra
 gments have a high\nmortality rate. The survivors (bound and free floating
 ) are well\nwithin the means of current direct imaging surveys\, as we dem
 onstrate\nthrough synthetic observations\, placing strong constraints on h
 ow\nfrequently discs fragment.\n\nHowever\, even if fragments don't surviv
 e\, the fragmentation process\nirrevocably alters the disc chemistry. I wi
 ll show preliminary work\ndemonstrating that while disc instability might 
 not be the principal\nformation mechanism for giant planets and brown dwar
 fs\, it sets the\ninitial dynamical and compositional conditions for plane
 t formation by\ncore accretion.\n
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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