Abstract:

Because the inflaton has to account both for the amplitude and index of
the primordial spectrum, its potential has to satisfy quite stringent
constraints.  In particular, only a stage of de Sitter inflation
can produce a scale invariant spectrum, and only a very flat potential
can support such an inflationary stage. In this talk, I describe a
scenario that renders the properties of the primordial spectrum independent
from the inflaton potential, and thus liberates the inflaton from those
stringent constraints. The main ingredient of this scenario is the
time-varying mass of a spectator scalar present during inflation. I
explain how density perturbations are seeded during any inflationary stage
and how a time-varying mass can mimic a stage of nearly de Sitter 
inflation.
If time  permits, I will also discuss why the scenario I propose fails if
the universe does not inflate.