A generiC fRamework fOr Photodisintegration Of LIght elementS

# ACROPOLIS

A generiC fRamework fOr Photodisintegration Of LIght elementS

• ACROPOLIS: A generiC fRamework fOr Photodisintegration Of LIght elementS
Paul Frederik Depta, Marco Hufnagel, Kai Schmidt-Hoberg
https://arxiv.org/abs/2011.06518
• Updated BBN constraints on electromagnetic decays of MeV-scale particles
Paul Frederik Depta, Marco Hufnagel, Kai Schmidt-Hoberg
https://arxiv.org/abs/2011.06519
• BBN constraints on MeV-scale dark sectors. Part II. Electromagnetic decays
Marco Hufnagel, Kai Schmidt-Hoberg, Sebastian Wild
https://arxiv.org/abs/1808.09324

The most recent version of the manual can always be found on GitHub in the manual/ folder. The respective publication on arXiv might be out-of-date, especially when new versions of the code become available.

# Abstract

The remarkable agreement between observations of the primordial light element abundances and the corresponding theoretical predictions within the standard cosmological history provides a powerful method to constrain physics beyond the standard model of particle physics (BSM). For a given BSM model these primordial element abundances are generally determined by (i) Big Bang Nucleosynthesis and (ii) possible subsequent disintegration processes. The latter potentially change the abundance values due to late-time high-energy injections which may be present in these scenarios. While there are a number of public codes for the first part, no such code is currently available for the second. Here we close this gap and present ACROPOLIS, A generiC fRamework fOr Photodisintegration Of LIght elementS. The widely discussed cases of decays as well as annihilations can be run without prior coding knowledge within example programs. Furthermore, due to its modular structure, ACROPOLIS can easily be extended also to other scenarios.

# Changelog

v1.2.1
(February 16, 2021)

• Fixed a bug in DecayModel. Results that have been obtained with older versions can be corrected by multiplying the parameter n0a with an additional factor 2.7012. All results of our papers remain unchanged.
• Updated the set of initial abundances to the most recent values returned by AlterBBN v2.2 (explcitly, we used failsafe=12)

v1.2
(January 15, 2021)

• Speed improvements when running non-thermal nucleosynthesis (by a factor 7)
• Modified the directory structure by moving ./data to ./acropolis/data to transform ACROPOLIS into a proper package, which can be installed via python3 setup.py install --user (also putting the executables decay and annihilation into your PATH)
• Added the decay of neutrons and tritium to the calculation
• For AnnihilationModel, it is now possible to freely choose the dark-matter density parameter (default is 0.12)

v1.1
(December 1, 2020)

• For the source terms it is now possible to specify arbitrary monochromatic and continuous contributions, meaning that the latter one is no longer limited to only final-state radiation of photons
• By including additional JIT compilation steps, the runtime without database files was drastically increased (by approximately a factor 15)
• The previously mentioned performance improvements also allowed to drop the large database files alltogether, which results in a better user experience (all database files are now part of the git repo and no additional download is required) and a significantly reduced RAM usage (∼900MB → ∼20MB)
• Fixed a bug, which could lead to NaNs when calculating heavily suppressed spectra with E0 ≫ me2/(22T)
• Added a unified way to print the final abundances in order to declutter the wrapper scripts. This makes it easier to focus on the actual important parts when learning how to use ACROPOLIS
• Moved from bytecode to simple text files for the remaining database file, as the former leads to unexpected behaviour on some machines

v1.0
(November 12, 2020)

• Initial release

# Installation from PyPI

This is the recommended way to install ACROPOLIS. To do so, make sure that pip is installed and afterwards simply execute the command

python3 -m pip install ACROPOLIS --user


After the installation is completed, the different modules of ACROPOLIS can be directly imported into our own Python code (just like e.g. numpy). Using this procedure also ensures that the executable decay and annihilation are copied into your PATH and that all dependencies are fulfilled.

# Installation from GitHub

To install ACROPOLIS from source, first clone the respective git repository by executing the command

git clone https://github.com/skumblex/acropolis.git


Afterward, switch into the main directory and run

python3 -m pip install . --user


# Usage without installation

If you just want to use ACROPOLIS without any additional installation steps, you have to at least make sure that all dependencies are fulfilled. As specified in setup.py, ACROPOLIS depends on the following packages (older versions might work, but have not been thoroughly tested)

• NumPy (> 1.19.1)
• SciPy (>1.5.2)
• Numba (> 0.51.1)

The most recent versions of these packages can be collectively installed at user-level, i.e. without the need for root access, by executing the command

python3 -m pip install numpy, scipy, numba --user


If these dependencies conflict with those for other programs in your work environment, it is strongly advised to utilise the capabilities of Python's virtual environments.

# Using the example models

ACROPOLIS ships with two executables, decay and annihilation, which wrap the scenarios discussed in section 4.1 and section 4.2 from the manual, respectively. Both of these files need to be called with six command-line arguments each, a list of which can be obtained by running the command of choice without any arguments at all. As an esxample, the following command runs the process of photodisintegration for an unstable mediator with a mass of 10MeV and a lifetime of 1e5s that decays exclusively into photons and has an abundance of 1e-10 relative to photons at a reference temperature of 10MeV (if you did not install ACROPOLIS via pip, you have to run this command from within the main directory and make sure to append an additional ./ to the beginning of the commands)

decay 10 1e5 10 1e-10 0 1


On a similar note, the following command runs the process of photodisintegration for residual s-wave annihilations of a dark-matter particle with a mass of 10MeV and a cross-section of 10e-25 cm³/s that annihilates exclusively into photons

annihilation 10 1e-25 0 0 0 1


# Supported platforms

ACROPOLIS should work on any platform with a working Python3 installation.

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