2023/03/02 by David Zegeye, Zegeye, David, F. Bianchini +31
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Radio Astronomy Observations and Technology #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.2303.00916
openalex publication_date 2023/03/02 · openalex created_date 2023/03/05 · openalex updated_date 2026/07/28
Diffusion damping of the cosmic microwave background (CMB) power spectrum results from imperfect photon-baryon coupling in the pre-recombination plasma. At redshift 5 × 104 < z < 2 × 106, the plasma acquires an effective chemical potential, and energy injections from acoustic damping in this era create μ-type spectral distortions of the CMB. These μ distortions trace the underlying photon density fluctuations, probing the primordial power spectrum in short-wavelength modes kS over the range 50 Mpc-1 \lesssim k \lesssim 104 Mpc-1. Small-scale power modulated by long-wavelength modes kL from squeezed-limit non-Gaussianities introduces cross-correlations between CMB temperature anisotropies and μ distortions. Under single-field inflation models, μ× T correlations measured from an observer in an inertial frame should vanish up to a factor of (kL/kS)2 ≪ 1. Thus, any measurable correlation rules out single-field inflation models. We forecast how well the next-generation ground-based CMB experiment CMB-S4 will be able to constrain primordial squeezed-limit non-Gaussianity, parameterized by fNL, using measurements of CℓμT as well as CℓμE from CMB E modes. Using current experimental specifications and foreground modeling, we expect σ(fNL) \lesssim 1000. This is roughly four times better than the current limit on fNL using μ× T and μ× E correlations from Planck and is comparable to what is achievable with LiteBIRD, demonstrating the power of the CMB-S4 experiment. This measurement is at an effective scale of k ≃ 740 Mpc-1 and is thus highly complementary to measurements at larger scales from primary CMB and large-scale structure.