In this talk I will highlight some general aspects of an extension to the classic Ultra Light Dark Matter (ULDM) paradigm with a second light scalar particle. As experimental data is beginning to put more stringent constraints on single field ULDM, it is an interesting to explore what happens when more light particles are added to the picture. Having more light degrees of freedom present in our Universe might even be easier to reconcile with many UV completions of the Standard Model, where many scalars seem to be the norm and not the exception. 

I will review some properties of standard ULDM, and how it is able to reproduce some of the features that are observed in galactic rotation curves. In particular, thanks to the wave nature of the light particle, there is a suppression of structure formation on small scales matching observations better than cold dark matter.

Following the introduction of an ULDM model with multiple scalars, I will show that many of these features transfer to this more generic model. The only real difference can be found at the center of galaxies, in the galactic core, where the density profile can be understood as a gravitational soliton, a ground state of a BEC. I will conclude by examining  these solitons in detail and discuss their cosmological implications as they offer an interesting avenue for distinguishing and constraining different Dark Matter models.

 

Host: Evangelos Sfakianakis