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 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. We identify three sources of systematic error-evolution of intrinsic scatter, baryon contributions to lensing, and non-Gaussianity of lensing-which will make this measurement difficult.