Extending the Gravitational Growth Framework
  The gravitational growth index formalism provides a model independent way to
look for deviations from general relativity by testing dark energy physics
distinct from its effects on the cosmic expansion history. Here we extend the
approach to incorporate an early time parameter g_star in addition to the
growth index in describing the growth of large scale structure. We illustrate
its utility for models with modified gravity at high redshift, early
acceleration, or early dark energy. Future data will have the capability to
constrain the dark energy equation of state, the growth index gamma, and g_star
simultaneously, with no degradation in the equation of state determination.
