Distinguishing Between Void Models and Dark Energy with Cosmic Parallax
  and Redshift Drift
  Two recently proposed techniques, involving the measurement of the cosmic
parallax and redshift drift, provide novel ways of directing probing (over a
time-span of several years) the background metric of the universe and therefore
shed light on the dark energy conundrum. The former makes use of upcoming
high-precision astrometry measurements to either observe or put tight
constraints on cosmological anisotropy for off-center observers, while the
latter employs high-precision spectroscopy to give an independent test of the
present acceleration of the universe. In this paper, we show that both methods
can break the degeneracy between LTB void models and more traditional dark
energy theories. Using the near-future observational missions Gaia and CODEX we
show that this distinction might be made with high confidence levels in the
course of a decade.
