Natural Inflation with Natural Trans-Planckian Axion Decay Constant from Anomalous $U(1)_X$

Understand

We propose a natural inflation model driven by an imaginary or axionic component of a K\"ahler modulus in string-inspired supergravity.

• The shift symmetry of the axion is gauged under an anomalous $U(1)_X$ symmetry, which leads to a modulus-dependent Fayet-Iliopoulos (FI) term.
• The matter fields are stabilized by F-terms, and the real component of the modulus is stabilized by the $U(1)_X$ D-term, while its axion remains light.
• Therefore, the masses of real and imaginary components of the modulus are separated at different scales.