The Cosmic Emu produces predictions for the matter power spectrum based on eight cosmological parametersand redshift. These predictions, based on Gaussian process emulation, approximate the power spectra that would be obtained from large dark matter simulations. The details are provide in "The Mira-Titan Universe: Precision Predictions for Dark Energy Surveys" (https://arxiv.org/abs/1508.02654) and an upcoming paper.
The Cosmic Emu requires the GNU Scientific Library (GSL). The makefile for both spectrum emulators includes lines to point to your installation of the GSL. The Cosmic Emu can produce predictions for the dark matter spectrum (P_cb) and the dark matter plus neutrino spectrum (P_tot). For each spectrum emulator, there are two files in addition to the makefile: emu.c and params.h. Simply type "make" at the command line to compile. The resulting program, emu.exe, is intended to be a demonstration of how to use the emu() and emuInit() functions. This program looks for a file called "xstar.dat" which should have nine space-delimited numbers on each line:
omega_m omega_b sigma_8 h n_s w_0 w_a omega_nu z
Running "emu.exe" will produce a prediction, in its own file, for each line in xstar.dat (e.g. if xstar.dat has 10 lines of inputs, the code will produce 10 output files, each with a prediction for the corresponding line).
The ranges for the parameters are
| Lower | Parameter | Upper |
|---|---|---|
| 0.12 | omega_m | 0.155 |
| 0.0215 | omega_b | 0.0235 |
| 0.7 | sigma_8 | 0.9 |
| 0.55 | h | 0.85 |
| 0.85 | n_s | 1.05 |
| -1.3 | w_0 | -0.7 |
| 0.3 | -(w_0+w_a)^(1/4) | 1.29 |
| 0.0 | omega_nu | 0.01 |
| 0.0 | z | 2.02 |
The code will not produce a spectrum for parameters outside these ranges. Note that the range for w_a depends on w_0.
Los Alamos National Security, LLC owns the copyright for this code. Please see LICENSE for copyright details.