Speaker
Description
Structure formation is a central topic for cosmology. The density perturbation power spectrum, i.e., Gaussian information, has already been constrained by data, but not much is known for the density perturbation bispectrum, the first cumulant beyond pure Gauss. For large-scales, conventional analytical methods based on hydrodynamic approximations provide accurate results, but for smaller distances they become quickly inaccurate. Kinetic Field Theory is able to give expressions for the density bispectrum valid even in the small-scale, non-linear regime as the theory naturally avoids stream crossing problems. For a restriction to the free Zel'dovich evolution of initially correlated particles, it is possible to derive analytic expressions for the bispectrum in the asymptotic small-scale regime. This is confirmed by numerical evaluations of the analytical integral expressions, showing that the validity of the description starts around k=1-10 h/Mpc. Universally for initial power spectra, a -5.5 power law exponent is found to leading order. This is due to a degeneracy in the Hessian of the exponent, which can only be found using asymptotic techniques. In contrast, large-scale expansions and hydrodynamics erroneously predict a -6 exponent for the power law at leading order.
