Towards Axion Monodromy Inflation with Warped KK-Modes
  We present a particularly simple model of axion monodromy: Our axion is the
lowest-lying KK-mode of the RR-2-form-potential $C_2$ in the standard
Klebanov-Strassler throat. One can think of this inflaton candidate as being
defined by the integral of $C_2$ over the $S^2$ cycle of the throat. It obtains
an exponentially small mass from the IR-region in which the $S^2$ shrinks to
zero size both with respect to the Planck scale and the mass scale of local
modes of the throat. Crucially, the $S^2$ cycle has to be shared between two
throats, such that the second locus where the $S^2$ shrinks is also in a warped
region. Well-known problems like the potentially dangerous back-reaction of
brane/antibrane pairs and explicit supersymmetry breaking are not present in
our scenario. However, the inflaton back-reaction starts to deform the geometry
strongly once the field excursion approaches the Planck scale. We derive the
system of differential equations required to treat this effect quantitatively.
Numerical work is required to decide whether back-reaction makes the model
suitable for realistic inflation. While we have to leave this crucial issue to
future studies, we find it interesting that such a simple and explicit stringy
monodromy model allows an originally sub-Planckian axion to go through many
periods with full quantitative control before back-reaction becomes strong.
Also, the mere existence of our ultra-light throat mode (with double
exponentially suppressed mass) is noteworthy.
