Towards Axion Monodromy Inflation with Warped KK-Modes

Abstract

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.

28 pages, 3 figures; v2: references added; v3: Corrected an underestimate of supergravity back-reaction in Eq. (36); results changed accordingly; added section 6 which develops the methodology for the 10d non-linear back-reaction; added references

References in corpus (15)

• Monodromy in the CMB: Gravity Waves and String Inflation
• A Natural Framework for Chaotic Inflation
• A Clockwork Axion
• The Powers of Monodromy
• Natural Inflation and Quantum Gravity
• D7-Brane Chaotic Inflation
• Towards Universal Axion Inflation and Reheating in String Theory
• Inflation and String Theory
• Geometrically Induced Metastability and Holography
• Relaxion Monodromy and the Weak Gravity Conjecture
• Axion Monodromy and the Weak Gravity Conjecture
• Towards Axionic Starobinsky-like Inflation in String Theory
• Axion Monodromy Inflation on Warped Throats
• Large Field Inflation and Gravitational Entropy
• D-brane scattering and annihilation

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