Efficient implementation of the Time Renormalization Group
  The Time Renormalization Group (TRG) is an effective method for accurate
calculations of the matter power spectrum at the scale of the first baryonic
acoustic oscillations. By using a particular variable transformation in the TRG
formalism, we can reduce the 2D integral in the source term of the equations of
motion for the power spectrum into a series of 1D integrals. The shape of the
integrand allows us to pre-compute only thirteen antiderivatives numerically,
which can then be reused when evaluating the outer integral. While this
introduces a few challenges to keep numerical noise under control, we find that
the computation time for nonlinear corrections to the matter power spectrum
decreases by a factor of 50. This opens up the possibility to use of TRG for
mass production as in Markov Chain Monte Carlo methods. A Fortran code
demonstrating this new algorithm has been made publicly available.
