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Probe new physics through CMB spectral distortions

The excellent agreement between the microwave sky emission and a perfect blackbody observed by the COBE FIRAS instrument is rightfully highlighted as a crucial confirmation of Big Bang cosmology. However, theory predicts that at higher sensitivity this agreement breaks down. Some of the predicted deviations are nearly sure bets, and others provide powerful probes of possible new physics. The PRISM absolute spectrometer will measure the spectrum more than three orders of magnitude better than FIRAS. y-distortions from the re-ionized gas as well as from hot clusters constitute a certain detection. However, μ-distortions and more general spectral distortions have the potential to uncover decaying dark matter and to probe the primordial power spectrum on very small scales that cannot be measured by other means, being contaminated by the nonlinearity of gravitational clustering at late times. These are but a few of the highlights of the rich and diverse physics and astrophysics that PRISM will be able to carry out.

Fig 6a
Spectral distortions for different scenarios. Thick lines denote positive, and thinner lines negative signal. The 1σ sensitivities of PRISM for different designs are also indicated.

Fig 6b
Projected constraints on different metal ions.