The Powers of Monodromy

Liam McAllister; Eva Silverstein; Alexander Westphal; Timm Wrase

doi:10.1007/JHEP09(2014)123

paper

The Powers of Monodromy

arXiv:1405.3652 · doi:10.1007/JHEP09(2014)123

Abstract

Flux couplings to string theory axions yield super-Planckian field ranges along which the axion potential energy grows. At the same time, other aspects of the physics remain essentially unchanged along these large displacements, respecting a discrete shift symmetry with a sub-Planckian period. After a general overview of this monodromy effect and its application to large-field inflation, we present new classes of specific models of monodromy inflation, with monomial potentials $μ^{4 - p} ϕ^{p}$ . A key simplification in these models is that the inflaton potential energy plays a leading role in moduli stabilization during inflation. The resulting inflaton-dependent shifts in the moduli fields lead to an effective flattening of the inflaton potential, i.e. a reduction of the exponent from a fiducial value $p_{0}$ to $p < p_{0}$ . We focus on examples arising in compactifications of type IIB string theory on products of tori or Riemann surfaces, where the inflaton descends from the NS-NS two-form potential $B_{2}$ , with monodromy induced by a coupling to the R-R field strength $F_{1}$ . In this setting we exhibit models with $p = 2/3, 4/3, 2,$ and $3$ , corresponding to predictions for the tensor-to-scalar ratio of $r \approx 0.04, 0.09, 0.13,$ and $0.2$ , respectively. Using mirror symmetry, we also motivate a second class of examples with the role of the axions played by the real parts of complex structure moduli, with fluxes inducing monodromy.

36 pages; v2: fixed typos, added references

The Powers of Monodromy

Abstract

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