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 $k\leq 1 h$Mpc$^{-1}$, and on small scales, better than 10% for $k \leq
10 h$Mpc$^{-1}$, at $z \geq 0.35$, which improves over previous methods.
