On Mitigation of the Uncertainty in Nonlinear Matter Clustering for
  Cosmic Shear Tomography
  We present a new method that deals with the uncertainty in matter-clustering
in cosmic shear power spectrum analysis that arises mainly due to poorly
understood nonlinear baryonic processes on small-scales. We show that the
majority of information about dark energy physics contained in the shear power
comes from these small-scales; removing these nonlinear scales from a cosmic
shear analysis results in a 50% cut in the accuracy of measurements of dark
energy parameters, marginalizing over all other parameters. In this paper we
propose a method to recover the information on small-scales by allowing cosmic
shear surveys to measure the nonlinear matter power spectrum themselves and
marginalize over all possible power spectra using path integrals. Information
is still recoverable in these nonlinear regimes from the geometric part of weak
lensing. In this self-calibration regime we find we recover 90% of the
information on dark energy. Including an informative prior, we find the
nonlinear matter power spectrum needs to be accurately known to 1% down to k=50
h/Mpc to recover 99% of the dark energy information. This presents a
significant theoretical challenge to understand baryonic effects on the scale
of galaxy haloes. However self-calibration from weak lensing may also provide
observational input to help constrain baryon physics.
