Dark Matter with N-Body Numerical Simulations

Abstract

The development of numerical N -body simulations have allowed to study formation process and evolution of galaxies at different scales. This paper presents the fundamental concepts of N -body systems applied to the cosmological evolution of the Λ-Cold Dark Matter (ΛCDM) model. In order to perform structure formation in the Universe, we provide an introduction to the basic equations and their implementation on the GADGET-2 software. We also present a simple guide to modify this code. First, we briefly describe the dark matter in the Universe as well as the theoretical and experimental basis of the ΛCDM model. Then, we focus on the simulation codes and provide the equations that govern most of the N -body simulations to model the dark matter. We describe the Smoothed Particle Hydrodynamics method used for simulating the gas, star dynamics and structure formation in these simulations. Then, cautiously, we guide the reader to the installation of GADGET-2 on a Linux-based computer, as well as to carry out a couple of examples to operate the code. Finally, by using a computational cluster, we show several results of a large structure simulation, analyse the outputs to display the matter power spectrum, and compare the outcome with theoretical predictions.

Classification algorithms applied to structure formation simulations

“…After having carried out a series of simulations for various configurations [for more details see (Chacón, J.; Vázquez, J. A.; Gabbasov, R. 2020, [27])] we obtain a one-to-one relationship of dark matter halos formed at time z = 0 with the initial conditions. This allows us to identify the dark matter halos, called "parents" or hosts and in turn we are able to determine substructures or subhalos of the same host.…”

“…The advantage is that an evaluation can be carried out on an independent set of initial conditions and the prediction effectiveness can be tested. For this purpose, four new sets of initial conditions were created, very similar to those listed in tables II and III in the reference [27]. In three of them the initial seed was changed, which is essentially a pseudo-random creator of numbers that are transmitted to the positions of the particles into the initial conditions.…”