Kavli Affiliate: Misao Sasaki
| First 5 Authors: Mohammad Ali Gorji, Misao Sasaki, Teruaki Suyama, ,
| Summary:
We explore a scenario in which dark matter is a massive bosonic field,
arising solely from quantum fluctuations generated during inflation. In this
framework, dark matter exhibits primordial isocurvature perturbations with an
amplitude of ${cal O}(1)$ at small scales that are beyond the reach of current
observations such as those from the CMB and large-scale structure. We derive an
exact transfer function for the dark matter field perturbations during the
radiation dominated era. Based on this result, we also derive approximate
expressions of the transfer function in some limiting cases where we confirm
that the exact transfer function reproduces known behaviors. Assuming a
monochromatic initial power spectrum, we use the transfer function to identify
the viable parameter space defined by the dark matter mass and the length scale
of perturbations. A key prediction of this scenario is copious formation of
subsolar mass dark matter halos at high redshifts. Observational confirmation
of a large population of such low-mass halos will support for the hypothesis
that dark matter originated purely from inflationary quantum fluctuations.
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