A solution to the problems of cusps and rotation curves in dark matter halos in the cosmological standard model

TL;DR

This paper presents an analytical method to understand dark matter halo structures, explaining how cosmological motions suppress cusps and form cores, aligning theory with observations and simulations.

Contribution

The authors develop an analytical approach linking initial density inhomogeneities and gravitational relaxation to dark matter halo profiles, addressing cusp-core and rotation curve discrepancies.

Findings

Cosmological motions heat dark matter particles, reducing cusps.

Analytical results align with improved N-body simulations.

Dark matter cores can naturally form in galaxy halos.

Abstract

We discuss various aspects of the inner structure formation in virialized dark matter (DM) halos that form as primordial density inhomogeneities evolve in the cosmological standard model. The main focus is on the study of central cusps/cores and of the profiles of DM halo rotation curves, problems that reveal disagreements among the theory, numerical simulations, and observations. A method that was developed by the authors to describe equilibrium DM systems is presented, which allows investigating these complex nonlinear structures analytically and relating density distribution profiles within a halo both to the parameters of the initial small-scale inhomogeneity field and to the nonlinear relaxation characteristics of gravitationally compressed matter. It is shown that cosmological random motions of matter `heat up' the DM particles in collapsing halos, suppressing cusp-like density profiles within developing halos, facilitating the formation of DM cores in galaxies, and providing an explanation for the difference between observed and simulated galactic rotation curves. The analytic conclusions obtained within this approach can be confirmed by the N-body model simulation once improved spatial resolution is achieved for central halo regions.