  The drift and diffusion coefficients of the inhomogeneous multi-mass
degenerate Landau equation are computed to describe the self-induced resonant
relaxation of a discrete self-gravitating quasi-Keplerian razor-thin
axisymmetric disc orbiting a massive black hole while relying on Gauss' method.
For a disc-like configuration in our Galactic centre, secular diffusion induces
an adiabatic distortion of orbits. When considering a disc composed of multiple
masses similarly distributed, the population of lighter stars will gain
eccentricity, driving it closer to the central black hole provided the
distribution function increases with angular momentum. The quenching of the
diffusion of a test star in the vicinity of the black hole due to the
divergence of the relativistic precessions (the "Schwarzschild barrier") is
correctly recovered by the kinetic equation. The dual stochastic Langevin
formulation yields consistent results and provides a versatile framework in
which to incorporate other stochastic processes.
