Trans-Planckian Issues for Inflationary Cosmology
  The accelerated expansion of space during the period of cosmological
inflation leads to trans-Planckian issues which need to be addressed. Most
importantly, the physical wavelength of fluctuations which are studied at the
present time by means of cosmological observations may well originate with a
wavelength smaller than the Planck length at the beginning of the inflationary
phase. Thus, questions arise as to whether the usual predictions of
inflationary cosmology are robust considering our ignorance of physics on
trans-Planckian scales, and whether the imprints of Planck-scale physics are at
the present time observable. These and other related questions are reviewed in
this article.
