All of the following, whether arising from our various data analyses or theoretical investigations, has its roots in the hard-line interpretation of Mach's Principle developed in the paper 2002GRG.
The discrete dynamical states phenomenology for spiral discs can be interpreted as the statement that, in bulge-subtracted discs (that is, discs as they would appear in the absence of the nucleus) the distribution of rotation velocities at 1kpc in spiral discs is multi-modal with four strong peaks being identified at approximately 49km/sec, 65km/sec, 112km/sec and 164km/sec.
The foregoing conclusion is based upon the analyses of four large samples of optical rotation curves totalling about 2800 ORCs in all. In the following, we give a non-technical description of the investigations which led to this conclusion and will show that the result can be qualitatively understood in a very simple way if we are prepared to accept that general circumstances which occur commonly in many models of the physical world also prevail within astrophysics.
This result has nothing to do with speculations such as "large-scale quantum effects" or similar.
The full technical details are given in 2002A&A and associated references.