Learning from the Scatter in Type Ia Supernovae
  Type Ia Supernovae are standard candles so their mean apparent magnitude has been exploited to learn about the redshift-distance relationship. Besides intrinsic scatter in this standard candle, additional source of scatter is caused by gravitational magnification by large scale structure. Here we probe the dependence of this dispersion on cosmological parameters and show that information about the amplitude of clustering, \sigma_8, is contained in the scatter. In principle, it will be possible to constrain \sigma_8 to within 5% with observations of 2000 Type Ia Supernovae. However, extracting this information requires subtlety as the distribution of magnifications is far from Gaussian. If one incorrectly assumes a Gaussian distribution, the estimate of the clustering amplitude will be biased three-\sigma away from the true value. 
Scott Dodelson (1 and 2) and Alberto Vallinotto (1 and 2) ((1)   Fermilab, (2) University of Chicago)