Rejuvenating the Matter Power Spectrum: Restoring Information with a Logarithmic Density Mapping

We find that nonlinearities in the dark-matter power spectrum are dramatically smaller if the density field first undergoes a logarithmic mapping. In the Millennium simulation, this procedure produces a power spectrum with a shape hardly departing from the linear power spectrum for k . 1hMpc−1 at all redshifts. Also, this procedure unveils pristine Fisher information on a range of scales reaching a factor of 2-3 smaller than in the standard power spectrum, yielding a factor of 10 higher signal-to-noise at z = 0. Subject headings: cosmology: observations — large-scale structure of universe — methods: statistical