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CATEGORIES:IoA Dynamics Lunch
SUMMARY:From secular theory to the dynamics of distorted d
 iscs - Gordon Ogilvie (DAMTP Cambridge)
DTSTART;TZID=Europe/London:20250904T123000
DTEND;TZID=Europe/London:20250904T133000
UID:TALK235234AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/235234
DESCRIPTION:"Distorted" gas discs in which the orbital motion 
 is non-circular or non-planar are implicated in ma
 ny astrophysical scenarios and lie at the interfac
 e between celestial mechanics and fluid dynamics. 
 Using a vector approach to celestial mechanics dev
 eloped originally by Milankovitch\, I will illustr
 ate and interpret some aspects and applications of
  secular theory\, which describes how eccentricity
  and inclination are communicated gravitationally 
 between the members of a planetary system or multi
 ple star system (for example) over very many orbit
 s. This classical theory can be extrapolated into 
 an approach to understanding distorted discs as sy
 stems in which eccentricity and inclination are co
 ntinuously distributed and are communicated throug
 h pressure as well as gravity. Instead of solving 
 the equations of fluid dynamics\, we can include i
 n the Hamiltonian the internal energy of the gas a
 nd its response to the orbital geometry. Together 
 with a "columnar" view of the motion in a disc\, t
 his approach reveals some of the characteristic pr
 operties of warped and eccentric discs in linear a
 nd nonlinear regimes. I will describe progress tow
 ards a unified description of distorted discs\, al
 so incorporating dissipative processes\, as well a
 s some outstanding problems.
LOCATION:Institute of Astronomy 
CONTACT:Mika Kontiainen
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