Constraining Dark Matter Models with Gravity, Flavor and Cosmic Rays

Dark Matter (DM) is one of the most enduring mysteries in physics, with strong evidence across multiple cosmic scales, from galactic rotation curves to large scale structures. Despite its gravitational effects, its fundamental properties—mass, interactions, and production mechanisms—remain unknown. This thesis investigates three distinct DM candidates by combining theoretical models with several constraints. First, we explore Ultralight Dark Matter (ULDM), a bosonic field with a kiloparsec-scale de Broglie wavelength that forms solitonic cores. These solitons influence supermassive black hole binaries, modifying their gravitational wave emissions through dynamical friction. Using NANOGrav data, we derive new constraints on ULDM properties. Next, we study axion-like particles with flavor-violating interactions, which can be produced via freeze-in mechanisms and evade constraints by remaining stable over cosmological timescales. In this context , we derive constraints from X-ray searches, stellar cooling, and collider experiments, identifying a viable DM mass range in the keV–MeV range. Lastly, we examine Minimal Dark Matter, focusing on electroweak multiplets such as the fermionic 5-plet. By incorporating Sommerfeld enhancement and bound state formation, we compute photon fluxes from DM annihilation and compare them to the sensitivities of FERMI-LAT and CTA. This thesis provides new insights into DM's nature and its potential detection across several experimental frontiers.