Abstract

Astrophysical discs tend to become warped whenever there is misalignment between the plane of the disc and that of an inner or outer binary, or the spin axis of the central object. Evidence of misalignments and warps has increased recently through observations of discs of dusty gas around young stars. The discovery of polar discs in eccentric binaries and Lidov-Kozai oscillations in fluid discs motivate the study of warped discs for large tilt angles. In this informal talk I will discuss some recent investigations and open questions regarding the nonlinear dynamics of warped discs, with an emphasis on ideal gas dynamics. Making use of the affine model in which the disc is represented as a set of fluid columns, I will discuss the importance of apsidal precession and a nonlinear resonance of the oscillation modes. I will also mention different types of instability that can occur in warped discs.