# AbacusSummit

## What is AbacusSummit?

AbacusSummit is a suite of large, high-accuracy cosmological N-body simulations. These simulations were designed to meet (and exceed!) the Cosmological Simulation Requirements of the Dark Energy Spectroscopic Instrument (DESI) survey. AbacusSummit was run on the Summit supercomputer at the Oak Ridge Leadership Computing Facility under a time allocation from the Department of Energy’s ALCC program.

Most of the simulations in AbacusSummit are 69123 = 330 billion particles in 2 Gpc/h volume, yielding a particle mass of about $$2\times 10^9\ \mathrm{M}_\odot/h$$.

AbacusSummit consists of over 140 of these simulations, plus other larger and smaller simulations, totaling about 60 trillion particles. Detailed specifications of the Simulations and Cosmologies are available on other pages.

Key portions of the suite are:

• A primary Planck2018 LCDM cosmology with 25 base simulations (330 billion particles in 2 Gpc/h).

• Four secondary cosmologies with 6 base simulations, phase matched to the first 6 of the primary boxes.

• A grid of 79 other cosmologies, each with 1 phase-matched base simulation, to support interpolation in an 8-dimensional parameter space, including $$w_0$$, $$w_a$$, $$N_\mathrm{eff}$$, and running of the spectral index.

• A suite of 1800 small boxes at the base mass resolution to support covariance estimation

• Other base simulations to match the cosmology of external flagship simulations and to explore the effects of our neutrino approximation.

• A 6x higher mass resolution simulation of the primary cosmology to allow study of group finding, and a large-volume 27x lower mass resolution simulation of the primary cosmology to provide full-sky light cone to z>2.

• Specialty simulations including those with fixed-amplitude white noise and scale-free simulations.

• Extensive data products including particle subsamples, halo catalogs, merger trees, kernel density estimates, and light cones.