Aligned Natural Inflation and Moduli Stabilization from Anomalous $U(1)$
  Gauge Symmetries
  To obtain natural inflation with large tensor-to-scalar ratio in string
framework, we need a special moduli stabilization mechanism which can separate
the masses of real and imaginary components of K\"ahler moduli at different
scales, and achieve a trans-Planckian axion decay constant from sub-Planckian
axion decay constants. In this work, we stabilize the matter fields by F-terms
and the real components of K\"ahler moduli by D-terms of two anomalous
$U(1)_X\times U(1)_A$ symmetries strongly at high scales, while the
corresponding axions remain light due to their independence on the
Fayet-Iliopoulos (FI) term in moduli stabilization. The racetrack-type axion
superpotential is obtained from gaugino condensations of the hidden gauge
symmetries $SU(n)\times SU(m)$ with massive matter fields in the bi-fundamental
respresentations. The axion alignment via Kim-Nilles-Pelroso (KNP) mechanism
corresponds to an approximate $S_2$ exchange symmetry of two K\"ahler moduli in
our model, and a slightly $S_2$ symmetry breaking leads to the natural
inflation with super-Planckian decay constant.
