Resonant backreaction in axion inflation

Domcke, Valerie; Guidetti, Veronica; Welling, Yvette; Westphal, Alexander

doi:10.1088/1475-7516/2020/09/009

Cited by 64 publications

(82 citation statements)

References 62 publications

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“…[31]. 9 For very strong gauge field backgrounds with correspondingly strong backreaction effects on the axion equation of motion, this approximation becomes invalid due to resonance effects in the coupled axion gauge field system [32][33][34][35]. However, in the presence of light fermions, the gauge field production is inhibited, and hence the resonance effects are expected to be less relevant.…”

Section: Implications For Axion Cosmologymentioning

confidence: 99%

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Axion assisted Schwinger effect

Domcke

Ema

Mukaida

2021

J. High Energ. Phys.

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We point out an enhancement of the pair production rate of charged fermions in a strong electric field in the presence of time dependent classical axion-like background field, which we call axion assisted Schwinger effect. While the standard Schwinger production rate is proportional to $$ \exp \left(-\pi \left({m}^2+{p}_T^2\right)/E\right) $$ exp − π m 2 + p T 2 / E , with m and pT denoting the fermion mass and its momentum transverse to the electric field E, the axion assisted Schwinger effect can be enhanced at large momenta to exp(−πm2/E). The origin of this enhancement is a coupling between the fermion spin and its momentum, induced by the axion velocity. As a non-trivial validation of our result, we show its invariance under field redefinitions associated with a chiral rotation and successfully reproduce the chiral anomaly equation in the presence of helical electric and magnetic fields. We comment on implications of this result for axion cosmology, focussing on axion inflation and axion dark matter detection.

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Section: Implications For Axion Cosmologymentioning

confidence: 99%

“…Qualitatively, resonance effects similar to refs. [32][33][34][35] may occur, leading to characteristic 'spikes' in the spectra of scalar and tensor perturbations. We leave a thorough investigation to future work.…”

Section: Jhep05(2021)001mentioning

confidence: 99%

Axion assisted Schwinger effect

Domcke

Ema

Mukaida

2021

J. High Energ. Phys.

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“…Since a rolling axion triggers the tachyonic instability of one circular polarization of the gauge field [69], whose exponential production both backreacts on the inflaton and produces scalar and tensor perturbations [67,68]. Details of the backreaction were examined in [70,71], and a very comprehensive analysis of these effects was provided recently in [72], with the results of the non-perturbative treatment recently cross-verified in [73] using a completely different gradient expansion formalism down to numerically identical predictions of the GW signal including resonance-induced peaked fine structure. The details of the dynamics are given in [1,72] and we will not repeat them here.…”

Section: Variations For Bicep3mentioning

confidence: 99%

Very Hairy Inflation

D'Amico,

Kaloper,

Westphal

2021

Preprint

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We revisit the rollercoaster cosmology based on multiple stages of monodromy inflation. Working within the framework of effective flux monodromy field theory, we include the full range of strong coupling corrections to the inflaton sector. We find that flattened potentials V ∼ φ p + . . . with p < ∼ 1/2, limited to N < ∼ 25 − 40 efolds in the first stage of inflation, continue to fit the CMB. They yield 0.96 < ∼ n s < ∼ 0.97, and produce relic gravity waves with 0.006 < ∼ r < ∼ 0.035, in full agreement with the most recent bounds from BICEP/Keck. The nonlinear derivative corrections generated by strong dynamics in EFT also lead to equilateral non-Gaussianity f eq N L O(1) − O(10), close to the current observational bounds. Finally, in multi-stage rollercoaster, an inflaton-hidden sector U (1) coupling can produce a tachyonic chiral vector background, which converts rapidly into tensors during the short interruption by matter domination. The produced stochastic gravity waves are chiral, and so they may be clearly identifiable by gravity wave instruments like LISA, Big Bang Observatory, Einstein Telescope, NANOgrav or SKA, depending on the precise model realization. We also point out that the current attempts to resolve the H 0 tension using early dark energy generically raise n s . This may significantly alter the impact of BICEP/Keck data on models of inflation.

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“…The production of hypercharge gauge fields during axion inflation is subject to several nonlinear effects, which highly complicates the theoretical analysis. These effects include (i) the backreaction of the produced gauge fields on the evolution of the inflation field [44,48,56,59] as well as (ii) the Schwinger pair production of hypercharged matter degrees of freedom [60][61][62]. The produced pairs of particles and antiparticles quickly form an ultrarelativistic plasma, which efficiently screens the electric field.…”

Section: Introductionmentioning

confidence: 99%

Hypermagnetogenesis from axion inflation: Model-independent estimates

Gorbar,

Schmitz,

Sobol

et al. 2021

Preprint

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Axion inflation coupled to the Standard Model (SM) hypercharge gauge sector represents an attractive scenario for the generation of primordial hypermagnetic fields. The description of this scenario is, however, complicated by the Schwinger effect, which gives rise to highly nonlinear dynamics. Hypermagnetogenesis during axion inflation in the absence of nonlinear effects is well studied and known to result in a hypermagnetic energy density that scales like e 2πξ /ξ 5 H 4 , where ξ is proportional to the time derivative of the axion-vector coupling in units of the Hubble rate H. In this paper, we generalize this result to the full SM case by consistently taking into account the Schwinger pair production of all SM fermions. To this end, we employ the novel gradient expansion formalism that we recently developed in Ref. [1] and which is based on a set of vacuum expectation values for bilinear hyperelectromagnetic functions in position space. We parametrize the numerical output of our formalism in terms of three parameters (ξ, H, and ∆, where the latter accounts for the damping of subhorizon gauge-field modes because of the finite conductivity of the medium) and work out semianalytical fit functions that describe our numerical results with high accuracy. Finally, we validate our results by comparing them to existing estimates in the literature as well as to the explicit numerical results in a specific inflationary model, which leads to good overall agreement. We conclude that the systematic uncertainties in the description of hypermagnetogenesis during axion inflation, which previously spanned up to several orders of magnitude, are now reduced to typically less than one order of magnitude, which paves the way for further phenomenological studies.

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Resonant backreaction in axion inflation

Cited by 64 publications

References 62 publications

Axion assisted Schwinger effect

Axion assisted Schwinger effect

Very Hairy Inflation

Hypermagnetogenesis from axion inflation: Model-independent estimates

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