29 research outputs found
Shedding light on the small-scale crisis with CMB spectral distortions
The small-scale crisis, discrepancies between observations and N-body
simulations, may imply suppressed matter fluctuations on subgalactic distance
scales. Such a suppression could be caused by some early-universe mechanism
(e.g., broken scale invariance during inflation), leading to a modification of
the primordial power spectrum at the onset of the radiation-domination era.
Alternatively, it may be due to nontrivial dark-matter properties (e.g., new
dark-matter interactions or warm dark matter) that affect the matter power
spectrum at late times, during radiation domination, after the perturbations
re-enter the horizon. We show that early- and late-time suppression mechanisms
can be distinguished by measurement of the distortion to the frequency
spectrum of the cosmic microwave background. This is because the
distortion is suppressed, if the power suppression is primordial, relative to
the value expected from the dissipation of standard nearly scale-invariant
fluctuations. We emphasize that the standard prediction of the distortion
remains unchanged in late-time scenarios even if the dark-matter effects occur
before or during the era (redshifts ) at which distortions are generated.Comment: 4 pages, 2 figures, PRD Rapid Communication, Featured in Physics,
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