Probing the scale dependence of nonGaussianity with spectral distortions of the cosmic microwave background
Abstract
Many inflation models predict that primordial density perturbations have a nonzero threepoint correlation function, or bispectrum in Fourier space. Of the several possibilities for this bispectrum, the most common is the localmodel bispectrum, which can be described as a spatial modulation of the smallscale (largewavenumber) power spectrum by longwavelength density fluctuations. While the local model predicts this spatial modulation to be scale independent, many variants have some scale dependence. Here we note that this scale dependence can be probed with measurements of frequencyspectrum distortions in the cosmic microwave background (CMB), in particular, highlighting Comptony distortions. Dissipation of primordial perturbations with wavenumbers 50 Mpc^{1}≲k ≲10^{4} Mpc^{1} gives rise to chemicalpotential (μ ) distortions, while dissipation of those with wavenumbers 1 Mpc^{1}≲k ≲50 Mpc^{1} gives rise to Comptony distortions. With localmodel nonGaussianity, the distortions induced by this dissipation can be distinguished from those due to other sources via their cross correlation with the CMB temperature T . We show that the relative strengths of the μ T and y T correlations thus probe the scale dependence of nonGaussianity and estimate the magnitude of possible signals relative to the sensitivities of future experiments. We discuss the complementarity of these measurements with other probes of squeezedlimit nonGaussianity.
 Publication:

Physical Review D
 Pub Date:
 June 2015
 DOI:
 10.1103/PhysRevD.91.123531
 arXiv:
 arXiv:1504.00675
 Bibcode:
 2015PhRvD..91l3531E
 Keywords:

 98.80.Es;
 98.65.Dx;
 98.70.Vc;
 Observational cosmology;
 Superclusters;
 largescale structure of the Universe;
 Background radiations;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 5 pages, 1 figure