Institute for Advanced Study Informal Astrophysics Seminar - Note Start Time Change to 10:45

Astrophysical discs often deviate from the circular, planar forms assumed in classical accretion-disc theory. Gravitational interaction with orbital companions can cause discs to become elliptical, warped and tidally deformed. In this talk I will discuss some physical consequences of these situations and introduce some novel theoretical methods for studying them. Generalizations of the shearing-box model, incorporating the oscillatory geometry experienced by orbiting fluid elements, reveal hydrodynamic turbulence that results from the destabilization of internal waves. Many aspects of warped discs can be alternatively be studied using a standard shearing box that undergoes modulated vertical oscillations. The nonlinear secular hydrodynamics of eccentric discs can be discussed in a Hamiltonian framework that connects with methods of celestial mechanics. Finally, a new affine model of astrophysical discs augments the computationally convenient equations of 2D hydrodynamics with the additional degrees of freedom needed to describe several of these situations.