If a GUT-scale phase transition occured after inflation, large domains in different vacuum states could be produced via the Kibble mechanism. The resulting network of scaling seeds supports horizon-scale density perturbations at all time (as shown in the below cartoon), stirring the baryon-photon plasma, which then generates CMB spectral distortions as the perturbations diffusively damp. […]
Acoustic waves generate CMB spectral distortions because the linear superposition of blackbodies seen by electrons as they rescatter CMB photons is not itself a blackbody (see right panel of above figure). Gravitational waves similarly produce CMB spectral distortions due to the induced quadrupole seen by electrons at the surface of last scattering (see left panel […]
Isocurvature perturbations are fluctuations in the relative number densities of particles at constant total density. Like adiabatic (or total density) fluctuations, primordial isocurvature perturbations will excite acoustic waves in the baryon-photon plasma. Jens Chluba and I computed the spectral distortions (deviations of the spatially averaged CMB from a perfect blackbody) generated when these acoustic waves […]
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