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Phases of New Physics in the CMB

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arxiv 1508.06342 v3 pith:U33726SA submitted 2015-08-26 astro-ph.CO hep-phhep-th

classification astro-ph.COhep-phhep-th
keywords phaseshiftfluctuationsanalyticbackgroundcosmicdataforms
verification ladder T0 review T1 audit T2 compute T3 formal
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Fluctuations in the cosmic neutrino background are known to produce a phase shift in the acoustic peaks of the cosmic microwave background. It is through the sensitivity to this effect that the recent CMB data has provided a robust detection of free-streaming neutrinos. In this paper, we revisit the phase shift of the CMB anisotropy spectrum as a probe of new physics. The phase shift is particularly interesting because its physical origin is strongly constrained by the analytic properties of the Green's function of the gravitational potential. For adiabatic fluctuations, a phase shift requires modes that propagate faster than the speed of fluctuations in the photon-baryon plasma. This possibility is realized by free-streaming relativistic particles, such as neutrinos or other forms of dark radiation. Alternatively, a phase shift can arise from isocurvature fluctuations. We present simple models to illustrate each of these effects. We then provide observational constraints from the Planck temperature and polarization data on additional forms of radiation. We also forecast the capabilities of future CMB Stage IV experiments. Whenever possible, we give analytic interpretations of our results.

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Cited by 4 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The Rise and Fall of Acoustic Oscillations at Cosmic Dawn

    astro-ph.CO 2026-07 conditional novelty 7.0 of 10

    Ignoring the percent-level phase offset between BAO and VAO features in the cosmic-dawn 21-cm power spectrum biases H(z) by ~2%; joint BAO–VAO templates are required for standard-ruler inference.

  2. Tracing the Neutrino-Induced Phase Shift in the 21-cm Spectrum

    astro-ph.CO 2025-09 conditional novelty 6.0 of 10

    The neutrino-induced phase shift in the 21-cm power spectrum is a redshift- and scale-dependent weighted average of two distinct templates: the known BAO phase shift and a newly computed, larger VAO phase shift.

  3. Neutrinophilic $\mathbf{\Lambda}$CDM Extension for EMPRESS, DESI and Hubble Tension

    hep-ph 2025-01 conditional novelty 5.0 of 10

    A combined fit of EMPRESS, DESI BAO, and CMB data prefers a neutrino asymmetry xi_nu = 0.056 +/- 0.017 and extra radiation delta_Neff = 0.41 +/- 0.16 in a neutrinophilic LambdaCDM model.

  4. ALP production from light primordial black holes: The role of superradiance

    astro-ph.CO 2025-01 conditional novelty 4.0 of 10

    Superradiance from spinning light primordial black holes can boost moduli production by about ten orders of magnitude, and the resulting axion-like dark radiation tightens Planck-based limits on these black holes.

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