Disk warp
= Disk warp
{title2=$W(R)=\beta(R)e^{i\gamma(R)}$}
A disk warp is a radial change of the orbital plane of successive disk annuli. In the small-tilt approximation, a complex tilt $W$ records its magnitude and azimuth. Pressure and internal torques communicate the tilt through <bending waves of a Keplerian disk> in the inviscid thin-disk regime. A flat tilted disk has constant $W$ even though its absolute orientation differs from the reference equatorial plane.