Analytic Approximations for Non-Cold Dark Matter Perturbations During Radiation Domination

What happens to the universe if one of its key components, dark matter, doesn’t behave as we assume? Dark matter makes up 27% of the universe; six times the abundance of ordinary matter. In most cosmological models, dark matter is simply treated as an entirely cold substance with zero inherent velocity. However, there is reason to believe that this might not be the case, and if dark matter isn’t cold, then it completely changes how structure evolves in the universe. While standard computational tools can compute these values in principle, they fail when we push them to the small cosmic scales that we are interested in. These tools are also often a black box from which it is very hard to derive real intuition for how our parameters directly affect the resulting structure. This research aims to develop a robust analytical model that directly maps the momentum distribution of dark matter particles to observable measurements of structure. The model I have developed and implemented computationally yields results that agree within 1% of those obtained using standard tools. The model achieves this accuracy while simultaneously providing much stronger intuition for the underlying physics than standard tools and not suffering from the same scale-related limitations. After continued refinement and optimization of code for efficient computation, my implementation will serve as a valuable tool for identifying observable signatures of non-thermal, non-cold dark matter within cosmic structure.