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SUMMARY:From secular theory to the dynamics of distorted discs - Gordon Og
 ilvie (DAMTP Cambridge)
DTSTART:20250904T113000Z
DTEND:20250904T123000Z
UID:TALK235234@talks.cam.ac.uk
CONTACT:Mika Kontiainen
DESCRIPTION:"Distorted" gas discs in which the orbital motion is non-circu
 lar or non-planar are implicated in many astrophysical scenarios and lie a
 t the interface between celestial mechanics and fluid dynamics. Using a ve
 ctor approach to celestial mechanics developed originally by Milankovitch\
 , I will illustrate and interpret some aspects and applications of secular
  theory\, which describes how eccentricity and inclination are communicate
 d gravitationally between the members of a planetary system or multiple st
 ar system (for example) over very many orbits. This classical theory can b
 e extrapolated into an approach to understanding distorted discs as system
 s in which eccentricity and inclination are continuously distributed and a
 re communicated through pressure as well as gravity. Instead of solving th
 e equations of fluid dynamics\, we can include in the Hamiltonian the inte
 rnal energy of the gas and its response to the orbital geometry. Together 
 with a "columnar" view of the motion in a disc\, this approach reveals som
 e of the characteristic properties of warped and eccentric discs in linear
  and nonlinear regimes. I will describe progress towards a unified descrip
 tion of distorted discs\, also incorporating dissipative processes\, as we
 ll as some outstanding problems.
LOCATION:Institute of Astronomy 
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