To observe, or not to observe, quantum-coherent dark matter in the Milky Way, that is a question

In recent years, Bose-Einstein-condensed dark matter (BEC-DM) has become a popular alternative to standard, collisionless cold dark matter (CDM). This BEC-DM - also called scalar field dark matter (SFDM) - can suppress structure formation and thereby resolve the small-scale crisis of CDM for a range of boson masses. However, these same boson masses also entail implications for BEC-DM substructure within galaxies, especially within our own Milky Way. Observational signature effects of BEC-DM substructure depend upon its unique quantum-mechanical features and have the potential to reveal its presence. Ongoing efforts to determine the dark matter substructure in our Milky Way will continue and expand considerably over the next years. In this contribution, we will discuss some of the existing constraints and potentially new ones with respect to the impact of BEC-DM onto baryonic tracers. Studying dark matter substructure in our Milky Way will soon resolve the question, whether dark matter behaves classical or quantum on scales of $\lesssim 1$ kpc.Comment: 23 pages; post-proof version, minor revisions (some more discussion on cosmological bounds and microlensing; substantially expanded list of references); invited article to Frontiers in Astronomy and Space Sciences, within the Research Topic "When Planck, Einstein and Vera Rubin meet. Dark Matter: What is it? Where is it?

Enabling Electroweak Baryogenesis through Dark Matter

We study the impact on electroweak baryogenesis from a swifter cosmological expansion induced by dark matter. We detail the experimental bounds that one can place on models that realize it, and we investigate the modifications of these bounds that result from a non-standard cosmological history. The modifications can be sizeable if the expansion rate of the Universe increases by several orders of magnitude. We illustrate the impact through the example of scalar field dark matter, which can alter the cosmological history enough to enable a strong-enough first-order phase transition in the Standard Model when it is supplemented by a dimension six operator directly modifying the Higgs boson potential. We show that due to the modified cosmological history, electroweak baryogenesis can be realized, while keeping deviations of the triple Higgs coupling below HL-LHC sensitivies. The required scale of new physics to effectuate a strong-enough first order phase transition can change by as much as twenty percent as the expansion rate increases by six orders of magnitude

Dark Stars: Improved Models and First Pulsation Results

We use the stellar evolution code MESA to study dark stars. Dark stars (DSs), which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the Universe. We compute stellar models for accreting DSs with masses up to 10^6 M_{sun}. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 10^4 -10^5 M_{sun}, our DSs are hotter by a factor of 1.5 than those in Freese et al.(2010), are smaller in radius by a factor of 0.6, denser by a factor of 3 - 4, and more luminous by a factor of 2. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n=3)-polytropes. We also perform a first study of dark star pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ~ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.Comment: 17 pages; 11 figures; revised version; accepted by Ap