Simulation Codes

Our project is built around two major cosmological simulation codes, HACC and Nyx.

HACC (Hardware/Hybrid Accelerated Cosmology Code) is an extreme-scale cosmological simulation code for large-scale gravity-only and hydrodynamical simulations. HACC is a particle-based code and has achieved excellent performance on a wide range of supercomputing architectures. For the SciDAC-5 project, HACC will be used to carry out high-resolution, large volume simulations to aid the creation of synthetic sky catalogs for e.g. LSST DESC and to investigate the impact of baryonic effects on cosmological observables.

Nyx is a parallel, adaptive mesh code that solves the equations of compressible hydrodynamics describing the evolution of baryonic gas coupled with an N-body treatment of the dark matter in an expanding universe. For the SciDAC-5 project, Nyx will be used to carry out simulations relevant to the measurements of the Lyman-α forest. The simulations will be used by the DESI collaboration to analyze observations. Nyx is a publicly available code hosted on a GitHub repository.

Simulation Outputs

Our simulations can serve a large range of science projects. We therefore built a simulation portal to publicly serve some of the HACC simulation data. During this SciDAC-5 project, we will continue to add new results to the portal. The portal allows easy access to the simulations via Globus.


A focus of this SciDAC and previous SciDAC projects is the creation of cosmic emulators. These emulators provide accurate predictions for a range of cosmological statistics, such as power spectra, mass functions and concentration-mass relations. A summary of currently available emulators can be found here