The DESI Experiment, a whitepaper for Snowmass 2013
  The Dark Energy Spectroscopic Instrument (DESI) is a massively multiplexed
fiber-fed spectrograph that will make the next major advance in dark energy in
the timeframe 2018-2022. On the Mayall telescope, DESI will obtain spectra and
redshifts for at least 18 million emission-line galaxies, 4 million luminous
red galaxies and 3 million quasi-stellar objects, in order to: probe the
effects of dark energy on the expansion history using baryon acoustic
oscillations (BAO), measure the gravitational growth history through
redshift-space distortions, measure the sum of neutrino masses, and investigate
the signatures of primordial inflation. The resulting 3-D galaxy maps at z<2
and Lyman-alpha forest at z>2 will make 1%-level measurements of the distance
scale in 35 redshift bins, thus providing unprecedented constraints on
cosmological models.
