Cosmology and Structure Formation of Scalarfield Dark Matter

The nature of dark matter (DM) remains one of the most profound open problems in cosmology and physics. While cosmological observations have determined the present cosmic energy density in DM with high precision, its particle nature is still unknown. Standard DM candidates are weakly-interacting massive particles from extensions to the standard model of particle physics, which give rise to what has become the standard collisionless cold dark matter (CDM) model. While the CDM model has proved successful on large scales, its predictions on smaller galactic scales have not been confirmed by observations: CDM predicts an overabundance of satellite galaxies around hosts of Milky-Way size, in contrast to what is observed in the Local Group and beyond. CDM simulations predict a universal density run for DM halos, which has a central cusp. In contrast, DM-dominated galaxies have been observed to follow flat cores out to around 1 kpc. All this evidence against collisionless CDM models have spurred activity in the community to study alternatives for the DM to solve these problems. In this Elise Richter application, we propose to continue our study of the cosmology and structure formation of one of these alternatives, namely scalar-field dark matter (SFDM). SFDM is made up of ultralight bosons, which also arise in extensions to the particle standard model. Promising SFDM candidates to solve the above problems possess a large enough "Jeans scale", below which DM clustering is suppressed. We will perform a coherent analysis of the growth of structure in a universe with SFDM throughout its entire evolution. Especially, we will expand upon the existing literature by considering more general SFDM models, in which the scalar field can be complex (not only real), and in which boson self-interactions are included. In such models, the expansion history can be different from the standard cosmological model with CDM, and we will study its impact on structure and galaxy formation. To this end, we will accomplish analytic calculations, as well as numerical simulations during this project. Multiple observables will be used to compare data with the predictions of SFDM models in order to determine whether SFDM as the dark matter can reproduce observations of galactic and cosmological scales self-consistently.

No additional funding sources recorded.