Neutrino mass without cosmic variance
  Measuring the absolute scale of the neutrino masses is one of the most
exciting opportunities available with near-term cosmological datasets. Two
quantities that are sensitive to neutrino mass, scale-dependent halo bias
$b(k)$ and the linear growth parameter $f(k)$ inferred from redshift-space
distortions, can be measured without cosmic variance. Unlike the amplitude of
the matter power spectrum, which always has a finite error, the error on $b(k)$
and $f(k)$ continues to decrease as the number density of tracers increases.
This paper presents forecasts for statistics of galaxy and lensing fields that
are sensitive to neutrino mass via $b(k)$ and $f(k)$. The constraints on
neutrino mass from the auto- and cross-power spectra of spectroscopic and
photometric galaxy samples are weakened by scale-dependent bias unless a very
high density of tracers is available. In the high density limit, using multiple
tracers allows cosmic-variance to be beaten and the forecasted errors on
neutrino mass shrink dramatically. In practice, beating the cosmic variance
errors on neutrino mass with $b(k)$ will be a challenge, but this signal is
nevertheless a new probe of neutrino effects on structure formation that is
interesting in its own right.
