Exploring Novel Dark Matter Interactions and Their Implications on Cosmological Models

Abstract: The standard ΛCDM model assumes that dark matter interacts only gravitationally, yet growing evidence suggests the possibility of novel interactions beyond gravity. This paper explores alternative dark matter interaction models, including self-interacting dark matter (SIDM), dark matter–baryon couplings, and hidden sector interactions, and examines their impact on cosmological structure formation, cosmic microwave background (CMB) anisotropies, and large-scale dynamics. Using effective field theory (EFT), N-body simulations, and gravitational lensing constraints, we investigate how these interactions influence galactic rotation curves, cosmic void distributions, and early-universe physics. Additionally, we assess whether deviations in gravitational wave propagation, relic density estimates, and cosmic acceleration trends could serve as observational signatures of these exotic dark matter properties. Key Highlights: Analysis of alternative dark matter interactions, including self-interactions and hidden-sector couplings. Impacts on cosmic evolution, structure formation, and baryon–dark matter interactions. Possible deviations from standard ΛCDM predictions in CMB and large-scale structure surveys. Observational constraints from gravitational lensing, weak interactions, and relic abundance calculations. Predictions for future astrophysical and laboratory experiments to test novel dark matter models. By integrating particle physics, cosmology, and astrophysical observations, this paper provides a comprehensive framework for understanding how dark matter interactions might reshape modern cosmological models, offering potentially testable predictions in upcoming gravitational wave, galaxy clustering, and direct detection experiments. Keywords: Dark matter interactions, self-interacting dark matter, cosmology, structure formation, ΛCDM alternatives, hidden sector physics, cosmic microwave background, gravitational lensing, modified gravity, baryon–dark matter coupling.