Super-Sample Covariance in Simulations
  Using separate universe simulations, we accurately quantify super-sample
covariance (SSC), the typically dominant sampling error for matter power
spectrum estimators in a finite volume, which arises from the presence of super
survey modes. By quantifying the power spectrum response to a background mode,
this approach automatically captures the separate effects of beat coupling in
the quasilinear regime, halo sample variance in the nonlinear regime and a new
dilation effect which changes scales in the power spectrum coherently across
the survey volume, including the baryon acoustic oscillation scale. It models
these effects at typically the few percent level or better with a handful of
small volume simulations for any survey geometry compared with directly using
many thousands of survey volumes in a suite of large volume simulations. The
stochasticity of the response is sufficiently small that in the quasilinear
regime, SSC can be alternately included by fitting the mean density in the
volume with these fixed templates in parameter estimation. We also test the
halo model prescription and find agreement typically at better than the 10%
level for the response.
