Apsidal precession, disc breaking and viscosity in warped discs

Understand

We demonstrate the importance of general relativistic apsidal precession in warped black hole accretion discs by comparing three - dimensional smoothed particle hydrodynamic simulations in which this effect is first neglected, and then included.

• If apsidal precession is neglected, we confirm the results of an earlier magnetohydrodynamic simulation which made this assumption, showing that at least in this case the $\alpha$ viscosity model produces very similar results to those of simulations where angular momentum transport is due to the magnetorotational instability.
• Including apsidal precession significantly changes the predicted disc evolution.
• For moderately inclined discs thick enough that tilt is transported by bending waves, we find a disc tilt which is nonzero at the inner disc edge and oscillates with radius, consistent with published analytic results.