Old Dark Energy
  Dark energy dynamics in the recent universe is influenced by its evolution
through the long, matter dominated expansion history. A particular dynamical
property, the flow variable, remains constant in several classes of scalar
field models as long as matter dominates; the dark energy is only free to
diverge in behavior at recent times. This gives natural initial conditions for
Monte Carlo studies of dark energy dynamics. We propose a parametrization for
the later evolution that covers a wide range of possible behaviors, is
tractable in making predictions, and can be constrained by observations. We
compare the approach to directly parametrizing the potential, which does not
take into account the maturity of the dark energy dynamics.
