Backreacted axion field ranges in string theory

By F. Baume, Eran Palti. 2016

149 citations recorded by the source corpus.

A bstractString theory axions are interesting candidates for fields whose potential might be controllable over super-Planckian field ranges and therefore as possible candidates for inflatons in large field inflation. Axion monodromy scenarios are setups where the axion shift symmetry is broken by some effect such that the axion can traverse a large number of periods potentially leading to super-Planckian excursions. We study such scenarios in type IIA string theory where the axion shift symmetry is broken by background fluxes. In particular we calculate the backreaction of the energy density induced by the axion vacuum expectation value on its own field space metric. We find universal behaviour for all the compactifications studied where up to a certain critical axion value there is only a small backreaction effect. Beyond the critical value the backreaction is strong and implies that the proper field distance as measured by the backreacted metric increases at best logarithmically with the axion vev, thereby placing strong limitations on extending the field distance any further. The critical axion value can be made arbitrarily large by the choice of fluxes. However the backreaction of these fluxes on the axion field space metric ensures a precise cancellation such that the proper field distance up to the critical axion value is flux independent and remains sub-Planckian. We also study an axion alignment scenario for type IIA compactifications on a twisted torus with four fundamental axions mixing to leave an axion with an effective decay constant which is flux dependent. There is a choice of fluxes for which the alignment parameter controlling the effective decay constant is unconstrained by tadpoles and can in principle lead to an arbitrarily large effective decay constant. However we show that these fluxes backreact on the fundamental decay constants so as to precisely cancel any enhancement leaving a sub-Planckian effective decay constant.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ba88ba62e6d66986b5b04ea38dbccd8108353bf9

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Citations in the corpus

The Weak Gravity Conjecture in three dimensions (2016, methodology): “In particular, it has been recently applied to large-field inflationary models and relaxions [2–22].”
Evidence for a sublattice weak gravity conjecture (2016, background): “From a phenomenological perspective, the WGC is especially interesting due to its ability to constrain models of large-field axion inflation [6–25].”
Lectures on the Swampland Program in String Compactifications (2021, background): “This backreaction issue was first introduced in [79] and further checked in [80–82].”
The weak gravity conjecture and scalar fields (2017, methodology): “Another conjecture, termed the Refined Swampland Conjecture (RSC) [25, 26], states that once a scalar field varies over a super-Planckian distance ∆φ ≥Mp there is an infinite tower of states, with mass scale m, whose mass decreases exponentially fast as a function of the scalar field variation m (φ+”
The Swampland: Introduction and Review (2019, background): “The second part was implicit in the analysis of [9, 154], since it applied to fields with potentials, but was not stated explicitly.”
The Swampland Conjectures: A Bridge from Quantum Gravity to Particle Physics (2021, background): “It has also been proposed, that the exponential behaviour cannot be delayed by more than order one distances (in Planck units) and that the Swampland Distance Conjecture should also be satisfied in the presence of a scalar potential (as long as it does not obstruct the infinite distance points) [69,”