The Dark Matter Puzzle

The problem of the missing mass in the Universe—at the scale of galaxies, large-scale structures, and the overall cosmic energy budget—remains a multifaceted enigma. In the cold dark matter scenario, one of the main candidates for a non-baryonic particle is the neutralino, the lightest and most stable supersymmetric particle. However, supersymmetry has not appeared as expected in experiments at the Large Hadron Collider (LHC) at CERN. In recent years, many alternative models have been proposed. In this talk, we will discuss several of these possibilities, including axions, sterile neutrinos, and modified gravity as potential explanations for the dark matter problem.