Total precession frequencies in action space in the neighbourhood of the razor-thin quasi-Keplerian disc introduced in Sect. 2.2. The disc being typically 0.4 pc away from the central BH, the precession frequencies are dominated by the mass precession frequencies . These mass precession frequencies are retrograde, so that Ω^s(J) < 0. The contours in this plot are spaced linearly between 95% and 5% of the minimum precession frequency satisfying . Because the degenerate Landau Eq. (19)does not involve any resonance vectors, the contours levels of Ω^s also correspond to the critical resonant lines γ(ω) introduced in Eq. (39).