http://arxiv.org/abs/2212.05812
Bose-Einstein-condensed dark matter (BEC-DM), also called scalar field dark matter (SFDM), has become a popular alternative to the standard, collisionless cold dark matter (CDM) model, due to its long-held potential to resolve the small-scale crisis of CDM. Halos made of BEC-DM have been modelled using the Gross-Pitaevskii (GP) equation coupled to the Poisson equation; the so-called GPP equations of motion. These equations are based on fundamental microphysical conditions that need to be fulfilled in order for the equations to be valid in the first place, related to the diluteness of the DM gas and the nature of the scattering model. We use these conditions in order to derive the implications for the BEC-DM particle parameters, notably the self-interaction coupling strength $g$. We compare the bounds with the constraint that results from the assumption of virial equilibrium of the central cores of halos, deriving a relationship that connects the BEC-DM parameters $g$ and particle mass $m$. We find that the GPP conditions are greatly fulfilled, for BEC-DM particle masses of interest, if such models also obey the virial condition that turns out to be the strongest constraint. We also derive the implications for the elastic scattering cross section (per particle mass) in BEC-DM halos, based on the scattering model of GPP, and find a huge range of possible values, depending on the strength of self-interaction. We put our results into context to recent literature which predicts sub-kpc core size.
T. Rindler-Daller
Tue, 13 Dec 22
43/105
Comments: 22 pages; 3 figures; subm. to Front. Astron. Space Sci
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