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