cosmoGW 0.0.7

code for cosmological gravitational wave backgrounds

CosmoGW

• Author: Alberto Roper Pol ([e-mail])
• Created: 20/02/2025 (moved from AlbertoRoper/cosmoGW created on 19/07/2023, which is an extension of AlbertoRoper/GW_turbulence from 01/11/2021)

CosmoGW (an extended update including GW_turbulence) is a project to produce results related to the production of COSMOlogical Gravitational Wave backgrounds (CosmoGW) from different sources in the early Universe (e.g., sound waves and MHD turbulence produced during cosmological phase transitions).

The project includes state-of-the-art GW models developed by the community, postprocessing calculations, numerical computations, plotting routines, and detector sensitivities.

If you use any of the cosmoGW results, please cite this repository and the relevant reference/s listed in the routines, corresponding to the original published work. I would also love to hear about your interest for this project and your work, so consider reaching me out on my email: [e-mail].

If you have any issues, comments, suggestions, or you are just interested in discussing any of the presented results, you are more than welcome to contact me by email.

Some of the routines use results from large-scale numerical simulations using the open-source Pencil Code; see [Pencil Code Collaboration], The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained, J. Open Source Softw. 6, 2807 (2021), arXiv:2009.08231, DOI:10.21105/joss.02807.

In particular, if you use any of the results that involve Pencil Code simulations, please cite the Pencil Code paper and the code.

Routines

The main routines of cosmoGW are:

• cosmoGW.py: functions relevant for cosmological stochastic gravitational wave backgrounds (SGWB).
• cosmology.py: functions relevant for cosmological calculations, including a Friedmann equations solver (see tutorial on Friedmann equations in cosmology.ipnyb) that can generate the solution files being read in some Pencil Code simulations (see tutorial cosmology_PC.ipnyb).
• cosmoMF.py: functions relevant for cosmological magnetic fields like bounds from different experiments, observations or projected sensitivities, and expectations from theory, among others.
• GW_analytical.py
• GW_fopt.py
• hydro_bubbles.py: functions to compute fluid perturbations induced by the expansion of bubbles in first-order phase transitions
• interferometry.py: functions to compute the response and sensitivity functions of interferometer space-based GW detectors (e.g., LISA and Taiji) to the detection of SGWBs (see tutorial on LISA interferometry in interferometry.ipynb) energy density and polarization, including the space-based network LISA-Taiji to detect polarization.
• modified_grav.py: functions relevant for GW production in the context of general theories of modified gravity.
• pta.py: functions used in the analysis of observations by pulsar timing array (PTA) collaborations: NANOGrav, PPTA, EPTA, and IPTA.
• reading.py: functions to read the output files of a specific set of runs (project) of the Pencil Code.
• run.py: contains the class run, used to store all the variables computed in the Pencil Code and in cosmoGW from the Pencil Code solitions. It includes functions to initialize and postprocess the results of a set of runs.
• spectra.py: contains description for specific spectral templates, postprocessing routines for numerical spectra, and other mathematical routines.

Some data files are available in cosmoGW that are useful in some of the projects:

• cosmology: includes files relevant for the cosmological evolution of the Universe and contains a tutorial on solving Friedmann equations.
• interferometry: includes files relevant for space-based GW interferometry calculations and contains a tutorial on computing the response functions, sensitivities and power law sensitivities to SGWB energy density and polarization.
• detector_sensitivity: includes the sensitivity of various detectors (ground-based, space-based, and pulsar timing arrays, among others), see the README file for info and references.

Projects

• GWs_from_PTs: contains tutorials related to the production of GWs (self-similar profiles calculation for now, but more coming soon!)

Publications

The work of the following publications can be reproduced using CosmoGW:

• Numerical Simulations of Gravitational Waves from Early-Universe Turbulence, A. Roper Pol, S. Mandal, A. Brandenburg, T. Kahaniashvili, A. Kosowsky, Phys. Rev. D 102 (2020) 8, 083512, arXiv:1903.08585. Datasets produced using Pencil Code are publicly available at doi:10.5281/zenodo.3692072. Direct access to Pencil Code files is also available in brandenb/projects/GW/.

• Polarization of gravitational waves from helical MHD turbulent sources, A. Roper Pol, S. Mandal, A. Brandenburg, T. Kahniashvili, J. Cosmol. Astropart. Phys. 04 (2022) 04, 019, arXiv:2107.05356. Datasets produced using Pencil Code are publicly available at doi:10.5281/zenodo.5525504.

• Gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band, A. Roper Pol, C. Caprini, A. Neronov, D. Semikoz, Phys. Rev. D 105 (2022) 12, 123502, arXiv:2201.05630. Datasets produced using Pencil Code are publicly available at doi:10.5281/zenodo.5782752.

• Modified propagation of gravitational waves from the early radiation era, Y. He, A. Roper Pol, A. Brandenburg, J. Cosmol. Astropart. Phys. 06 (2023) 025, arXiv:2212.06082. Datasets produced using Pencil Code are publicly available at doi:10.5281/zenodo.5525504. Direct access to Pencil Code files is also available in brandenb/projects/Horndeski/.

• LISA and γ-ray telescopes as multi-messenger probes of a first-order cosmological phase transition, A. Roper Pol, A. Neronov, C. Caprini, T. Boyer, D. Semikoz, submitted to Astron. Astrophys., arXiv:2307.10744.

• Characterization of the gravitational wave spectrum from sound waves within the sound shell model, A. Roper Pol, S. Procacci, C. Caprini, Phys. Rev. D 109 (2024) 6, 063531, arXiv:2308.12943.

• Gravitational waves from decaying sources in strong phase transitions, A. Roper Pol, I. Stomberg, C. Caprini, R. Jinno, T. Konstandin, H. Rubira, submitted to J. Cosmol. Astropart. Phys., arXiv:2409.03651.