Dark energy from the motions of neutrinos
  We demonstrate that a scalar field is unable to reverse its direction of
motion while continuously exchanging energy with another fluid. If the rate of
transfer is modulated by the scalar's acceleration, the field can undergo a
rapid process of freezing, despite being displaced from the local minimum of
its potential. This enables dark energy to form from any potential, regardless
of its shape. The field's equation of state mimicks that of a cosmological
constant. We present a physically motivated realisation in the form of a
derivative neutrino-majoron coupling. Coherent motions, which form only once
the neutrinos become non-relativistic, could be responsible for instigating the
freezing process. This would provide a natural resolution to the dark energy
coincidence problem, while avoiding the dynamical instabilities associated with
mass-varying neutrino models. Finally we discuss possible means by which this
model could be experimentally verified.
