intensitytools/evogrowthpy

Code for fast calculation of growth

evogrowthpy (version 1.0.0)

This repository contains the source code of evogrowthpy, a python wrapper for a fast code to compute the scale-independent growth factor for wACDM models of interacting dark energy and for the nDGP model of modified gravity. The main computations are performed in C++ using a code based on part of ReACT.

Authors: Pedro Carrilho, Ben Bose
Date of last update: December 2022

Contact information: If you have any questions, contact Pedro Carrilho (pedromgcarrilhoATgmail.com) or post an issue on this page.

Quick start

Prerequisites

In any case you need:

• C++11 or later
• GNU Scientific Library version 2.5 or higher (GSL; see https://www.gnu.org/software/gsl/)
• g++ version 4.9.1 or higher

For the python wrapper, you need python with the following packages:

• cython, numpy, scipy (essential)
• jupyter, matplotlib (for plotting in the example notebook)

Building and installation

The current version of evogrowthpy is meant to be used only via the python wrapper.

To install it, clone this repo, cd into the evogrowthpy directory and execute

pip install .

To check if the installation was successful, just open python and do

import evogrowthpy

A python notebook (test_evogrowthpy.ipynb) is also included, which includes an example for running the code in the most general setup. If it runs correctly, the installation was successful.

Usage

To run the python wrapper, first import the package via

import evogrowthpy as evgr

and use the function get_growth_wrap

D, f = evgr.get_growth_wrap(Omm, hubble, [z, w0, wa, xi, Omega_rc], accuracy=1e-3, om_cb=0)

where Omm is the total matter density parameter, hubble is the Hubble constant divided by 100, z is the redshift, w0 is the EOS parameter of dark energy and wa is its derivative w.r.t. a. xi is the interaction parameter of the dark scattering model and Omega_rc is the parameter of nDGP. The accuracy is set to 1e-3 which should be sufficient in most cases. The parameter om_cb is set to 0 by default and should only be non-zero when massive neutrinos are present (i.e. when Om_cb != Om_m) and the user wishes to calculate the growth rate on small scales.

The output of this function is always composed of the growth factor D and the growth rate f, with D normalised to be equal to the scale factor a at early times.

The code does not yet allow for a full calculation of the scale-dependent growth of massive neutrinos, but is sufficient to compute the growth in two limits. For the large-scale limit, the user should use the default om_cb=0, while for the small scale limit, the user should use instead om_cb = Omm - Om_nu

See the python notebook (test_evogrowthpy.ipynb) for an example of a full run and more details.

License

evogrowthpy is free software, distributed under the GNU General Public License. This implies that you may freely distribute and copy the software. You may also modify it as you wish, and distribute these modified versions. You must always indicate prominently any changes you made in the original code and leave the copyright notices, and the no-warranty notice intact. Please read the General Public License for more details.