Geometrical destabilisation of ultra-light axions in string inflation

Cicoli, Michele; Guidetti, Veronica; Pedro, Francisco G.

doi:10.1088/1475-7516/2019/05/046

Cited by 31 publications

(47 citation statements)

References 58 publications

(99 reference statements)

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“…e.g. [34,35]), and the possibility of tackling the η-problem, these models are very attractive, and it is important to understand their observational viability.…”

Section: Introductionmentioning

confidence: 99%

Mild non-Gaussianities under perturbative control from rapid-turn inflation models

Bjorkmo

Ferreira

Marsh

2019

J. Cosmol. Astropart. Phys.

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Inflation can be supported in very steep potentials if it is generated by rapidly turning fields, which can be natural in negatively curved field spaces. The curvature perturbation, ζ, of these models undergoes an exponential, transient amplification around the time of horizon crossing, but can still be compatible with observations at the level of the power spectrum. However, a recent analysis (based on a proposed single-field effective theory with an imaginary speed of sound) found that the trispectrum and other higher-order, non-Gaussian correlators also undergo similar exponential enhancements. This arguably leads to 'hyper-large' non-Gaussianities in stark conflict with observations, and even to the loss of perturbative control of the calculations. In this paper, we provide the first analytic solution of the growth of the perturbations in two-field rapid-turn models, and find it in good agreement with previous numerical and single-field EFT estimates. We also show that the nested structure of commutators of the in-in formalism has subtle and crucial consequences: accounting for these commutators, we show analytically that the naively leading-order piece (which indeed is exponentially large) cancels exactly in all relevant correlators. The remaining non-Gaussianities of these models are modest, and there is no problem with perturbative control from the exponential enhancement of ζ. Thus, rapidturn inflation with negatively curved field spaces remains a viable and interesting class of candidate theories of the early universe.

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“…e.g. [34,35]), and the possibility of tackling the η-problem, these models are very attractive, and it is important to understand their observational viability.…”

Section: Introductionmentioning

confidence: 99%

Mild non-Gaussianities under perturbative control from rapid-turn inflation models

Bjorkmo

Ferreira

Marsh

2019

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

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“…For situations where this effect can endanger inflation due to the existence of light moduli see e.g. [16][17][18][19].…”

Section: Effective Masses From Kinetic Mixingsmentioning

confidence: 99%

“…If the scalar A is very light this will lead to a destabilization [16][17][18][19], but if there is already another positive supersymmetric mass (or not supersymmetric) then there is no issue. Note also that the mass is exactly of the same order as the supersymmetry breaking sourced by the quintessence sector, that is H 2 .…”

Section: Kähler Moduli Inspired Examplementioning

confidence: 99%

“…which may give a considerable negative contribution to the moduli masses and completely ruin quintessence, as happens with the geometrical destabilization [16][17][18][19]. Note however that once canonical normalization is taken into account we will have a mass of the form (3.10) which seems less dangerous.…”

Section: Kähler Moduli Inspired Examplementioning

confidence: 99%

“…We also see why such mechanism (which is intrinsic in supergravity embeddings) may instead pose a catastrophic threat to otherwise healthy quintessence models, depending on the kinetic mixings. This effect is already studied within the context of inflationary cosmology, because it can ruin inflation, and therefore is dubbed "geometrical destabilization" [16][17][18][19]. In the fourth section we turn to the gaugini masses which are of course also influenced by the F-term problem.…”

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

On the F-term problem and quintessence supersymmetry breaking

Farakos

2021

Eur. Phys. J. C

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Inspired by the stringy quintessence F-term problem we highlight a generic contribution to the effective moduli masses that arises due to kinetic mixings between the moduli and the quintessence sector. We then proceed to discuss few supergravity toy models that accommodate such effect, and point out possible shortcomings. Interestingly, in the standard 2-derivative supergravity action there is no term to mediate the supersymmetry breaking from the kinetic quintessence sector to the gaugini and generate Majorana masses. Therefore we also propose a 2-derivative supersymmetric invariant that plays exactly this role.

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Revisiting non-Gaussianity in multifield inflation with curved field space

2020

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Recent studies of inflation with multiple scalar fields have highlighted the importance of non-canonical kinetic terms in novel types of inflationary solutions. This motivates a thorough analysis of non-Gaussianities in this context, which we revisit here by studying the primordial bispectrum in a general two-field model. Our main result is the complete cubic action for inflationary fluctuations written in comoving gauge, i.e. in terms of the curvature perturbation and the entropic mode. Although full expressions for the cubic action have already been derived in terms of fields fluctuations in the flat gauge, their applicability is mostly restricted to numerical evaluations. Our form of the action is instead amenable to several analytical approximations, as our calculation in terms of the directly observable quantity makes manifest the scaling of every operator in terms of the slow-roll parameters, what is essentially a generalization of Maldacena's single-field result to non-canonical two-field models. As an important application we derive the single-field effective field theory that is valid when the entropic mode is heavy and may be integrated out, underlining the observable effects that derive from a curved field space.

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Geometrical destabilisation of ultra-light axions in string inflation

Cited by 31 publications

References 58 publications

Mild non-Gaussianities under perturbative control from rapid-turn inflation models

Mild non-Gaussianities under perturbative control from rapid-turn inflation models

On the F-term problem and quintessence supersymmetry breaking

Revisiting non-Gaussianity in multifield inflation with curved field space

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