  We explain flat rotation curves and the baryonic Tully-Fisher relation by a
combination of three hypotheses. The first is a formulation of the equivalence
principle for gravitationally bound quantum $N$ body systems, while the second
is a second order phase transition hypothesized to arise from a competition
between the effects of Unruh and deSitter radiation experienced by a static
observer in a galaxy. The third is a light dark matter particle, coupled to a
dark photon.
  The phase transition is triggered in a ring where the Unruh temperature of a
static observer falls below the deSitter temperature, thus explaining the
apparent coincidence that Milgrom's $a_0 \approx a_\Lambda = c^2
\sqrt{\frac{\Lambda}{3}}$
  This phase transition drives the dark matter particles to a regime
characterized by a broken $U(1)$ invariance and an approximate scale
invariance. In this regime, the dark matter condenses to a super-current
characterized by a differentially rotating ring with a flat rotation curve,
coupled to a dark magnetic field. The baryonic Tully Fisher relation is a
direct consequence of the approximate scale invariance.
