Emu is an open-source particle-in-cell code for solving the neutrino quantum kinetic equations in 1, 2, or 3 spatial dimensions with arbitrary angular resolution. It is part of the AMReX-Astro suite of astrophysical simulation codes.
Emu represents the neutrino distribution function as a set of particles, each of which represent a collection of neutrinos and antineutrinos with unique position and momentum. Each particle carries two density matrices to define the flavor state of the neutrinos and antineutrinos it represents. Emu includes the vacuum, matter, and neutrino self-interaction potentials. We calculate the self-interaction potential using PIC deposition and interpolation algorithms that efficiently compute the local number density and flux at particle locations.
Emu is implemented in C++ and is based on the AMReX library for high-performance, block-structured adaptive mesh refinement. Emu is parallelized with MPI + OpenMP for CPUs and MPI + CUDA for GPUs.
To quickly try Emu out using your browser, you can open an interactive Emu workspace in Gitpod!
Emu's prebuilt Gitpod workspace tracks the current release branch, and you can find pre-compiled examples in the Examples directory.
For example, to run and visualize the MSW setup:
cd Examples/2-Flavors/msw
./main3d.gnu.TPROF.MPI.ex inputs_msw_test
python plot_first_particle.py
And then open the plot through the file browser on the left of the screen.
If you would like to run Emu on your own machine, first clone Emu with the AMReX submodule:
git clone --recurse-submodules https://github.com/AMReX-Astro/Emu.git
Then change directories to Emu/Exec.
Before each compilation, you must symbolically generate Emu source code for the number of neutrino flavors you wish to use. Do this like:
make generate NUM_FLAVORS=2
Then compile Emu with make, e.g.:
make NUM_FLAVORS=2
Emu parameters are set in an input file, and we provide a series of sample
input files for various simulation setups in Emu/sample_inputs.
You can run the MSW setup in Emu by doing:
./main3d.gnu.TPROF.MPI.ex inputs_msw_test
Emu is an open-source code under active development, and we welcome any interested users to create issues to report bugs or ask for help. We also welcome pull requests from any users interested in contributing to Emu.
If you run into any unforeseen issues while running Emu, we especially encourage you to review the active issues on the Emu GitHub and submit a new issue if needed so we are aware.