CMB Spectral $\mu$-Distortion of Multiple Inflation Scenario

TL;DR

This paper investigates how a multiple inflation scenario with an intermediate matter-dominated phase affects the CMB spectral distortions, especially the $mbda$-distortion, providing potential observational signatures of such models.

Contribution

It introduces a model with two inflations and an intermediate phase, analyzing its impact on CMB spectral distortions and constraining the power spectrum enhancement.

Findings

$mbda$-distortion can be ten times larger than standard predictions for certain scales.

$y$-distortion remains largely unaffected by the power spectrum enhancement.

The model constrains the scale $k_b$ to be greater than 10 Mpc$^{-1}$ for consistency with observations.

Abstract

In multiple inflation scenario having two inflations with an intermediate matter-dominated phase, the power spectrum is estimated to be enhanced on scales smaller than the horizon size at the beginning of the second inflation, $k > k_{\rm b}$. We require $k_{\rm b} > 10 {\rm Mpc}^{-1}$ to make sure that the enhanced power spectrum is consistent with large scale observation of cosmic microwave background (CMB). We consider the CMB spectral distortions generated by the dissipation of acoustic waves to constrain the power spectrum. The $\mu$-distortion value can be $10$ times larger than the expectation of the standard $\Lambda$CDM model ($\mu_{\Lambda\mathrm{CDM}} \simeq 2 \times 10^{-8}$) for $ k_{\rm b} \lesssim 10^3 {\rm Mpc}^{-1}$, while the $y$-distortion is hardly affected by the enhancement of the power spectrum.