Circumventing the eta problem in building an inflationary model in
  string theory
  The eta problem is one of the most significant obstacles to building a
successful inflationary model in string theory. Planck mass suppressed
corrections to the inflaton potential generally lead to inflaton masses of
order the Hubble scale and generate contributions of order unity to the eta
slow roll parameter rendering prolonged slow roll inflation impossible. We
demonstrate the severity of this problem in the context of brane anti-brane
inflation in a warped throat of a Calabi-Yau flux compactification with all
phenomenologically dangerous moduli stabilized. Using exact numerical solutions
we show that the eta problem can be avoided in scenarios where the inflaton is
non-minimally coupled to gravity and has Dirac-Born-Infeld (DBI) kinetic term.
We show that the resulting cosmic microwave background (CMB) observables such
as measures of non-gaussianites can, in principle, serve as a probe of
scalar-gravity couplings.
