Dynamical breaking of shift-symmetry in supergravity-based inflation

Abstract

Shift-symmetry is essential to protect the flatness of the potential, even beyond the super-Planckian vacuum expectation value (VEV) for an inflaton field. The breaking of the shift-symmetry can yield potentials suitable for super-Planckian excursion of the inflaton. The aim of this paper is to illustrate that it is indeed possible to break the shift-symmetry dynamically within 4 dimensional supergravity prior to a long phase of inflation. Thanks to the shift-symmetry, the leading contribu- tion to the inflaton potential is free from the dangerous exponential factor even after its breaking, which is the main obstacle to realizing the super-Planckian inflation in supergravity. But, in our simple model, the resulting inflaton potential is a cosine type potential rather than the power-law one and it is difficult to realize a super-Planckian breaking scale unfortunately.

8 pages, no figure; v2: minor revision, estimation of the inflaton potential is corrected; v3: minor revision, published version, title is changed

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• Gravity Waves From Non-Minimal Quadratic Inflation
• Inflation from Supergravity with Gauged R-symmetry in de Sitter Vacuum
• Natural Braneworld Inflation in Light of Recent Results from Planck and BICEP2
• From Hybrid to Quadratic Inflation With High-Scale Supersymmetry Breaking
• Bound on largest $r\lesssim 0.1$ from sub-Planckian excursions of inflaton