Galaxies as simple dynamical systems: observational data disfavor dark
  matter and stochastic star formation
  (Abridged) Galaxies are observed to be simple systems but the standard model
of cosmology (SMoC) implies a haphazard merger history driven by dynamical
friction on dark matter halos. The SMoC is tested here with the results that
the dual dwarf galaxy theorem is in contradiction to the data if the SMoC is
true, and the action of dynamical friction is not evident in the galaxy
population. A consistency test for this conclusion comes from the significantly
anisotropic distributions of satellite galaxies. Independently, the long
history of failures of the SMoC have the likelihood that it describes the
observed Universe to less than 10^-4 per cent. The implication for fundamental
physics is that exotic dark matter particles do not exist and that consequently
effective gravitational physics on the scales of galaxies and beyond ought to
be non-Newtonian/non-Einsteinian. The data imply that scale-invariant dynamics,
as discovered by Milgrom, is an excellent description of galaxies in the
weak-field regime. Observations of stellar populations in galaxies suggest the
galaxy-wide IMF, the IGIMF, to vary with star formation rate and that
stochastic descriptions of star formation are inconsistent with the data. A
consequence of this understanding of galactic astrophysics is that most dwarf
satellite galaxies are formed as tidal dwarf galaxies in galaxy-galaxy
encounters, that they follow the mass-metallicity relation, that galactic
mergers are rare, that galaxies immersed in external potentials are physically
larger than isolated galaxies and that star-forming galaxies form a main
sequence. Eight predictions are offered which will allow the concepts raised
here to be tested. A very conservative, cold- and warm-dark-matter-free
cosmological model may be emerging from these considerations.
