Role of trans-Planckian modes in cosmology
  Motivated by the old trans-Planckian (TP) problem of inflationary cosmology,
it has been conjectured that any consistent effective field theory should keep
TP modes `hidden' behind the Hubble horizon, so as to prevent them from turning
classical and thereby affecting macroscopic observations. In this paper we
present two arguments against the Hubble horizon being a scale of singular
significance as has been put forward in the TP Censorship Conjecture (TCC).
First, refinements of TCC are presented that allow for the TP modes to grow
beyond the horizon while still keeping the de-Sitter conjecture valid. Second,
we show that TP modes can turn classical even well within the Hubble horizon,
which, as such, negates this rationale behind keeping them from crossing it.
The role of TP modes is known to be less of a problem in warm inflation,
because fluctuations start out usually as classical. This allows warm inflation
to be more resilient to the TP problem compared to cold inflation. To
understand how robust this is, we identity limits where quantum modes can
affect the primordial power spectrum in one specific case.
