CMBS4 forecasts for constraints on f_{NL} through μ distortion anisotropy
Abstract
Diffusion damping of the cosmic microwave background (CMB) power spectrum results from imperfect photonbaryon coupling in the prerecombination plasma. Energy release at redshifts 5 ×10^{4}<z <2 ×10^{6} can create μ type spectral distortions of the CMB. These μ distortions trace the underlying photon density fluctuations, probing the primordial power spectrum in shortwavelength modes k_{S} over the range 50 Mpc^{1}≲k ≲10^{4} Mpc^{1}. Smallscale power modulated by longwavelength modes k_{L} from squeezedlimit nonGaussianities introduces cross correlations between CMB temperature anisotropies and μ distortions. Under singlefield inflation models, μ ×T correlations measured from an observer in an inertial frame should vanish up to a factor of (k_{L}/k_{S})^{2}≪1 . Thus, any measurable correlation rules out singlefield inflation models. We forecast how well the nextgeneration groundbased CMB experiment CMBS4 will be able to constrain primordial squeezedlimit nonGaussianity, parametrized by f_{NL}, using measurements of C_{ℓμ}^{T} as well as C_{ℓμ}^{E} from CMB E modes. Using current experimental specifications and foreground modeling, we expect σ (f_{NL})≲1000 . This is roughly 4 times better than the current limit on f_{NL} using μ ×T and μ ×E correlations from Planck and is comparable to what is achievable with LiteBIRD, demonstrating the power of the CMBS4 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 largescale structure.
 Publication:

Physical Review D
 Pub Date:
 November 2023
 DOI:
 10.1103/PhysRevD.108.103536
 arXiv:
 arXiv:2303.00916
 Bibcode:
 2023PhRvD.108j3536Z
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 19 pages, 6 figures