Pre-Inflationary Relics in the CMB?
  String Theory and Supergravity allow, in principle, to follow the transition
of the inflaton from pre-inflationary fast roll to slow roll. This introduces
an infrared depression in the primordial power spectrum that might have left an
imprint in the CMB anisotropy, if it occurred at accessible wavelengths. We
model the effect extending $\Lambda$CDM with a scale $\Delta$ related to the
infrared depression and explore the constraints allowed by {\sc Planck} data,
employing also more conservative, wider Galactic masks in the low resolution
CMB likelihood. In an extended mask with $f_{sky}=39\%$, we thus find $\Delta =
(0.351 \pm 0.114) \times 10^{-3} \, \mbox{Mpc}^{-1}$, at $99.4\%$ confidence
level, to be compared with a nearby value at $88.5\%$ with the standard
$f_{sky}=94\%$ mask. With about 64 $e$--folds of inflation, these values for
$\Delta$ would translate into primordial energy scales ${\cal O}(10^{14})$ GeV.
