Pyflation is a Python package for calculating cosmological perturbations during an inflationary expansion of the universe.

## Introduction

Pyflation is a Python package for calculating cosmological perturbations during inflationary expansion of the universe.

Pyflation was created by Ian Huston (http://www.ianhuston.net) while at Queen Mary, University of London (http://www.qmul.ac.uk).

Once installed the modules in the pyflation package can be used to run simulations of different scalar field models of the early universe.

The main classes are contained in the cosmomodels module and include simulations of background fields and first order and second order perturbations. The sourceterm package contains modules required for the computation of the term required for the evolution of second order perturbations. The analysis package contains routines to calculate the first order First and Second order perturbations can be calculated for single field models but only first order perturbations can be evolved for multi-field models.

Alongside the Python package, the bin directory contains Python scripts which can run first and second order simulations. A helper script called “pyflation_qsubstart.py” sets up a full second order run (including background, first order and source calculations) to be used on queueing system which contains the “qsub” executable (e.g. a Rocks cluster).

Installation of the code is described in the INSTALL.txt file. The pyflation package can be installed as a normal Python package to the site-packages directory or each run of the code can be self-contained with code, results and logs all contained in a run directory.

The “pyflation_newrun.py” script creates a new run directory and populates it with the code and sub-directories which are required. In particular the file “provenence.log” in the “applogs” directory contains information about the version of the code and system libraries at the time of the creation of the run.

For copyright and license information please see the LICENSE.txt file. For installation information see the INSTALL.txt file. For usage information see the USAGE.txt file.

## Relevant Publications

Pyflation has been used to generate results for peer-reviewed publications including

• Ian Huston, Adam Christopherson, Calculating Non-adiabatic Pressure Perturbations during Multi-field Inflation, Physical Review D85, 063507 (2012), http://arXiv.org/abs/1111.6919
• Ian Huston, Karim A. Malik, Second Order Perturbations During Inflation Beyond Slow-roll, Journal of Cosmology and Astroparticle Physics 10(2011)029, http://arXiv.org/abs/1103.0912
• Ian Huston, Karim A. Malik, Numerical calculation of second order perturbations, Journal of Cosmology and Astroparticle Physics 09(2009)019, http://arXiv.org/abs/0907.2917

As a courtesy please cite one or more of these papers in any publication which uses Pyflation.

## Acknowledgements

This author of this software is supported by the Science & Technology Facilities Council under grants ST/G002150/1 and ST/J001546/1.

Thank you to Adam Christopherson, Karim Malik, David Mulryne and Jason Furtney for their discussions and contributions.

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