Searching for features of a string-inspired inflationary model with
  cosmological observations
  The latest Planck results show a power deficit in the temperature
anisotropies near $\ell \approx 20$ in the cosmic microwave background (CMB).
This observation can hardly be explained within the standard inflationary
$\Lambda$-cold-dark-matter ($\Lambda$CDM) scenario. In this paper we consider a
string theory inspired inflationary model (axion monodromy inflation) with a
step-like modulation in the potential which gives rise to observable signatures
in the primordial perturbations. One interesting phenomenon is that the
primordial scalar modes experience a sudden suppression at a critical scale
when the modulation occurs. By fitting to the CMB data, we find that the model
can nicely explain the $\ell \approx 20$ power deficit anomaly as well as
predict specific patterns in the temperature-polarization correlation and
polarization autocorrelation spectra. Though the significance of the result is
not sufficient to claim a detection, our analysis reveals that fundamental
physics at extremely high energy scales, namely, some effects inspired by
string theory, may be observationally testable in forthcoming cosmological
experiments.
