Perturbation theory remixed: Improved nonlinearity modeling beyond standard perturbation theory
May 2023 • 2023PhRvD.107j3534W
Abstract • We present a novel n EPT (n th-order Eulerian perturbation theory) scheme to model the nonlinear density field by the summation up to n th-order density fields in perturbation theory. The obtained analytical power spectrum shows excellent agreement with the results from all 20 Dark-Quest suites of N -body simulations spreading over a broad range of cosmologies. The agreement is much better than the conventional two-loop standard perturbation theory and would reach out to kmax≃0.4 h /Mpc at z =3 for the best-fitting Planck cosmology, without any free parameters. We find that the n EPT results, particularly for n >4 , depend sensitively on the grid size, but that can be removed by employing an effective field theory-type fitting function. The method can accelerate the forward modeling of the nonlinear cosmological density field, an indispensable probe of cosmic mysteries such as inflation, dark energy, and dark matter.
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