Matter power spectrum from a Lagrangian-space regularization of perturbation theory

We present a new approach to computing the matter density power spectrum, from large linear scales to small, highly nonlinear scales. Instead of explicitly computing a partial series of high-order diagrams, as in perturbative resummation schemes, we embed the standard perturbation theory within a realistic nonlinear Lagrangian-space ansatz. We also point out that an adhesion-like regularization of the shell-crossing regime is more realistic than a Zel'dovich-like behavior, where particles freely escape to infinity. This provides a cosmic web power spectrum with good small-scale properties that provide a good matching with a halo model on mildly nonlinear scales. We obtain a good agreement with numerical simulations on large scales, better than 3% for k <= 1h Mpc(-1), and on small scales, better than 10% for k <= 10h Mpc(-1), at z >= 0.35, which improves over previous methods. DOI: 10.1103/PhysRevD.87.083522