The Different Regimes of Axion Gauge Field Inflation

We study gravitational wave production from gauge preheating in a variety of inflationary models, detailing its dependence on both the energy scale and the shape of the potential. We show that gauge preheating generically leads to a large gravitational wave background that contributes significantly to the effective number of relativistic degrees of freedom in the early Universe, N eff . We demonstrate that the efficiency of gravitational wave production is correlated with the tensor-to-scalar ratio, r.In particular, we show that efficient gauge preheating in models whose tensor-to-scalar ratio would be detected by next-generation cosmic microwave background experiments (r 10 −3 ) will either be detected through its contribution to N eff or ruled out. Furthermore, we show that bounds on N eff provide the most sensitive probe of the possible axial coupling of the inflaton to gauge fields regardless of the potential.

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“…Conversely, the extension to non-Abelian gauge groups is non-trivial. See for example [74][75][76][77][78][79].…”

Section: A Models Of Inflationmentioning

confidence: 99%

Constraining axion inflation with gravitational waves from preheating

et al. 2020

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“…8 As in the rest of this paper, we focus on Abelian gauge fields here. Non-Abelian gauge field configurations can also be sourced by a non-vanishing axion velocity [26][27][28][29], however due to the self-interactions of the non-Abelian gauge fields, the fermion backreaction originating from the induced fermion current is less relevant in this case [30]. Moreover, for a discussion of the gravitational production of neutral fermions in axion inflation, see ref.…”

Section: Implications For Axion Cosmologymentioning

confidence: 99%

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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“…(3.39), indicates that for suitable values of θ, the induced 8 As in the rest of this paper, we focus on Abelian gauge fields here. Non-Abelian gauge field configurations can also be sourced by a non-vanishing axion velocity [26][27][28][29], however due to the self-interactions of the non-Abelian gauge fields, the fermion backreaction originating from the induced fermion current is less relevant in this case [30]. Moreover, for a discussion of the gravitational production of neutral fermions in axion inflation, see Ref.…”

Section: Implications For Axion Cosmologymentioning

confidence: 99%

Axion assisted Schwinger effect

Domcke,

Ema,

Mukaida

2021

Preprint

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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(−π(m 2 +p 2 T )/E ), with m and p T 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(−πm 2 /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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The Different Regimes of Axion Gauge Field Inflation

Cited by 9 publications

References 113 publications

Constraining axion inflation with gravitational waves from preheating

Constraining axion inflation with gravitational waves from preheating

Axion assisted Schwinger effect

Axion assisted Schwinger effect

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