Sledgehamr: Simulating scalar fields with adaptive mesh refinement

Sledgehamr (ScaLar fiEld Dynamics Getting solvEd witH Adaptive Mesh Refinement) is an AMReX-based code to simulate the dynamics of coupled scalar fields on a 3-dimensional mesh. Adaptive mesh refinement (AMR) can boost performance if spatially localized regions of the scalar field require high resolution. Compatible with both GPU and CPU clusters, sledgehamr offers a flexible and customizable framework. This framework enables various applications, such as the generation of gravitational wave spectra.

For a detailed description of the code please consult the accompanying paper: https://arxiv.org/abs/arXiv:2404.02950

For questions, comments, or bug reports please use the GitHub issues feature, or contact me via email: m.s.a.buschmann@uva.nl

Installation

Prerequisites

• AMReX (git clone https://github.com/AMReX-Codes/amrex)
• FFTW3

Running the minimal examples

The minimal examples can be run by following the instructions in the Jupyter notebooks notebooks/MinimalExample.ipynb and notebooks/NextToMinimalExample.ipynb.

Create a project

Sledgehamr comes with a few different physics scenarios already implemented such as axion strings and a first-order phase transition of a single scalar field + gravitational waves, as well as two example projects MinimalExample and NextToMinimalExample. The accompanying paper describes in detail how other scenarios can be implemented.

Code documentation

• https://msabuschmann.github.io/sledgehamr/
• https://arxiv.org/abs/2404.02950

How to cite

If you use sledgehamr, please cite its accompanying paper:

• Malte Buschmann, "Sledgehamr: Simulation Scalar Fields with Adaptive Mesh Refinement", Astrophys.J. 979 (2025) 2, 220, arXiv:2404.02950

BibTex:

@article{Buschmann:2024bfj,
    author = "Buschmann, Malte",
    title = "{Sledgehamr: Simulating Scalar Fields with Adaptive Mesh Refinement}",
    eprint = "2404.02950",
    archivePrefix = "arXiv",
    primaryClass = "hep-ph",
    doi = "10.3847/1538-4357/ad9ea2",
    journal = "Astrophys. J.",
    volume = "979",
    number = "2",
    pages = "220",
    year = "2025"
}

Publications using this code

2022

• "Dark matter from axion strings with adaptive mesh refinement", M. Buschmann et al., Nature Commun. 13 (2022) 1, 1049, https://arxiv.org/abs/2108.05368

2024

• "Signatures of primordial energy injection from axion strings", J. Benabou et al., Phys.Rev.D 109 (2024) 5, 055005, https://arxiv.org/abs/2308.01334

2025

• "Sledgehamr: Simulating Scalar Fields with Adaptive Mesh Refinement", M. Buschmann, Astrophys.J. 979 (2025) 2, 220, https://arxiv.org/abs/2404.02950
• "Axion mass prediction from adaptive mesh refinement cosmological lattice simulations", J. Benabou et al., Phys.Rev.Lett. 134 (2025) 24, 241003, https://arxiv.org/abs/2412.08699
• "Thick and Thin Wall Collisions with Adaptive Mesh Refinement", M. Buschmann et al., to appear