Illuminating the dark universe with a very high density galaxy redshift
  survey over a wide area
  The nature of dark energy remains a profound mystery 20 years after the
discovery of cosmic acceleration. A very high number density galaxy redshift
survey over a wide area (HD GRS Wide) spanning the redshift range of 0.5<z<4
using the same tracer, carried out using massively parallel wide field
multi-object slit spectroscopy from space, will provide definitive dark energy
measurements with minimal observational systematics by design. The HD GRS Wide
will illuminate the nature of dark energy, and lead to revolutionary advances
in particle physics and cosmology. It will also trace the cosmic web of dark
matter and provide key insight into large-scale structure in the Universe. The
required observational facility can be established as part of the probe
portfolio by NASA within the next decade.
