![]() ![]() One example is related to the dissipation of small-scale perturbations (wavenumber k ≃ 10 2−10 4 Mpc −1) in the photon–baryon fluid in the presence of ultra-squeezed limit non-Gaussianity (Ganc & Komatsu 2012 Pajer & Zaldarriaga 2012). However, anisotropic heating caused by non-standard early-universe processes can in principle lead to observable distortion anisotropies (Chluba, Khatri & Sunyaev 2012b). Aside from the distortion signals imprinted at arcminute angular scales by clusters of galaxies through the Sunyaev–Zeldovich (SZ) effect (Zeldovich & Sunyaev 1969 Carlstrom, Holder & Reese 2002), anisotropies in the distortion to the CMB frequency spectrum are expected to be small. Measurements of cosmic microwave background (CMB) spectral distortions can teach us about the thermal history of the Universe (see Chluba & Sunyaev 2012 Sunyaev & Khatri 2013 Tashiro 2014 Chluba 2016, for recent overviews). Our formulation provides a systematic framework for computing higher order correlation functions of distortions with CMB temperature anisotropies and can be extended to describe correlations with polarization anisotropies.Ĭosmology: observations, cosmology: theory 1 INTRODUCTION We also include a simple description for the evolution of distortions through photon diffusion, showing that these corrections can usually be neglected. Absolute measurements are thus required to obtain model-independent distortion constraints on primordial non-Gaussianity. Our expressions highlight the fact that the amplitudes of the spectral-distortion fluctuations induced by non-Gaussianity depend also on the homogeneous value of those distortions. We provide a systematic formulation of the problem using Fourier-space window functions, clarifying and generalizing previous approximations. In this work, we derive approximations that allow describing the associated distortion field. For instance, the dissipation of small-scale acoustic modes does create distortion anisotropies, in particular for non-Gaussian primordial perturbations. Anisotropies in distortions to the frequency spectrum of the cosmic microwave background (CMB) can be created through spatially varying heating processes in the early Universe. ![]()
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