Abstract
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. The scalar potential for natural inflation is realized by the superpotential from the non-perturbative effects. The trans-Planckian axion decay constant, which is needed to fit with BICEP2 observations, can be obtained naturally in this model.
Highlights
JHEP07(2014)052 f should be trans-Planckian f ∼ O(10) in the Planck units [5]
We have proposed a natural infaltion model based on string inspired SUGRA with gauged shift symmetry U(1)X
Once the matter fields obtain non-zero vacuum expectation values (VEV), the real component of modulus T is fixed by the D-term flatness
Summary
The U(1)X transformation of matter field φ11/n → φ11/neiq/n cancels the phase factor e−ibδ from shift of the modulus T → T + iǫδ under U(1)X Such kind of non-perturbative superpotential can be obtained from the gaugino condensation with massive chiral superfields, which form representation of the condensation group, such as SU(n) and can be integrated out in effective field theory. Effects of the gauge invariant non-perturbative term on moduli stabilization and inflation have been studied in [30,31,32,33,34,35]. In this form the matter field φ1 has positive exponent, and gives an analytic coefficient for the non-perturbative term, which makes the anomalous.
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