  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 $k_{\rm max}\simeq 0.4~h/{\rm Mpc}$ at $z=3$ for the best-fitting
Planck cosmology, without any free parameters. The method can accelerate the
forward modeling of the non-linear cosmological density field, an indispensable
probe of cosmic mysteries such as inflation, dark energy, and dark matter.
