The dynamics of twisted accretion disc around a Kerr black hole

We derive the system of equations describing the time dependent twisted accretion disc around a Kerr black hole (twist equations), The post-Newtonian corrections to the equations of motion and effects of the gravitomagnetic force are taken into account. We show that introduction of appropriate coordinate system greatly simplifies the derivation of equations and allows to consider sufficiently large but smoothly changing with distance and time inclination angles. The twist equations obtained by different authors in previous works are limiting cases of our general system.