Hypermagnetogenesis from axion inflation: Model-independent estimates

Gorbar, E. V.; Schmitz, K.; Sobol, O. O.; Vilchinskii, S. I.

doi:10.48550/arxiv.2111.04712

Cited by 4 publications

(19 citation statements)

References 49 publications

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“…Also, we can work in the Coulomb gauge as we had done in the nonhelical case. In such a case, it is found that the second term in the above action amplifies the electromagnetic modes associated with one of the polarizations when compared to the other, thereby violating parity or, equivalently, inducing helicity [39][40][41]44,45].…”

Section: B the Helical Casementioning

confidence: 99%

“…Eqs. ( 42), (45), and (48)] do not exactly mimic the behavior of J ∝ a n but contain small departures from it. As a result of these deviations, we find that the spectral indices depend on the parameters describing the potential apart from the slow roll parameters.…”

Section: Coupling Function In Slow Roll Inflationary Modelsmentioning

confidence: 99%

“…III, we had constructed coupling functions JðϕÞ [as given by Eqs. ( 42), (45), and (48)] in the three slow roll models (40), (43), and ( 46) so that they lead to nearly scale invariant spectra for the magnetic field when n ¼ 2. Even after the introduction of the step, we have chosen to work with the above-mentioned coupling functions JðϕÞ that we had constructed in the slow roll approximation.…”

Section: A In Potentials With a Stepmentioning

confidence: 99%

“…2, we find that the spectrum of the magnetic field is red in the case of the quadratic potential (40), but is mildly blue in the cases of the small field model (43) and the first Starobinsky model (46), which lead to slow roll inflation. This can be attributed to the fact that the coupling functions (42), (45), and (48) do not exactly mimic the coupling function J ¼ ½aðηÞ=aðη e Þ n . In the case of the quadratic potential, for the choice of the coupling function (42), we find that the quantity J 00 =J can be expressed as…”

Section: Appendix: the Electromagnetic Spectral Indices In Slow Roll ...mentioning

confidence: 99%

“…Often, this is achieved by coupling the electromagnetic field to either the scalar field that drives inflation [27,29,[34][35][36] or to the Ricci scalar describing the background [28,30,32,33]. In fact, it has also been discovered that the addition of a parity violating term in the electromagnetic action can significantly enhance the amplitude of magnetic fields generated during inflation [37][38][39][40][41][42][43][44][45]. It can be shown that, for certain choices of the coupling function, the spectrum of magnetic fields generated can be nearly scale invariant consistent with the current constraints over a wide range of scales (see, for instance, Refs.…”

Section: Introductionmentioning

confidence: 99%

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Challenges in the choice of the nonconformal coupling function in inflationary magnetogenesis

et al. 2022

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Primordial magnetic fields are generated during inflation by considering actions that break the conformal invariance of the electromagnetic field. To break the conformal invariance, the electromagnetic fields are coupled either to the inflaton or to the scalar curvature. Also, a parity violating term is often added to the action in order to enhance the amplitudes of the primordial electromagnetic fields. In this work, we examine the effects of deviations from slow roll inflation on the spectra of nonhelical as well as helical electromagnetic fields. We find that, in the case of the coupling to the scalar curvature, there arise certain challenges in generating electromagnetic fields of the desired shapes and strengths even in slow roll inflation. When the field is coupled to the inflaton, it is possible to construct model-dependent coupling functions that lead to nearly scale invariant magnetic fields in slow roll inflation. However, we show that sharp features in the scalar power spectrum generated due to departures from slow roll inflation inevitably lead to strong features in the power spectra of the electromagnetic fields. Moreover, we find that such effects can also considerably suppress the strengths of the generated electromagnetic fields over the scales of cosmological interest. We illustrate these aspects with the aid of inflationary models that have been considered to produce specific features in the scalar power spectrum. Further, we find that, in such situations, if the strong features in the electromagnetic power spectra are to be undone, the choice of the coupling function requires considerable fine tuning. We discuss wider implications of the results we obtain.

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Section: B the Helical Casementioning

confidence: 99%

Section: Coupling Function In Slow Roll Inflationary Modelsmentioning

confidence: 99%

Section: A In Potentials With a Stepmentioning

confidence: 99%

Section: Appendix: the Electromagnetic Spectral Indices In Slow Roll ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Challenges in the choice of the nonconformal coupling function in inflationary magnetogenesis

et al. 2022

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On sphaleron heating in the presence of fermions

Drewes,

Zell

2024

J. Cosmol. Astropart. Phys.

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Axion-like particles with a coupling to non-Abelian gauge fields at finite temperature can experience dissipation due to sphaleron heating. This could play an important role for warm inflation or dynamical dark energy. We investigate to what degree the efficiency of this non-perturbative mechanism depends on the details of the underlying particle physics model. For a wide range of scenarios and energy scales, we find that a previously discussed suppression of sphaleron heating by light fermions can be alleviated. As an outlook, we point out that fermionic effects may provide a new mechanism for ending warm inflation.

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Fate of first-order chiral phase transition in QCD: Implications to dark QCD

Wang¹,

Kawaguchi²,

Matsuzaki³

et al. 2022

Preprint

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The first-order nature of the chiral phase transition in QCD-like theories can play crucial roles to address a dark side of the Universe, where the created out-of equilibrium is essential to serve as cosmological and astrophysical probes such as gravitational wave productions, which have extensively been explored. This interdisciplinary physics is built based on a widely-accepted conjecture that the thermal chiral phase transition in QCDlike theories with massless (light) three flavors is of first order. We find that such a first order feature may not hold, when ordinary or dark quarks are externally coupled to a weak enough background field of photon or dark photon (which we collectively call a "magnetic" field). We assume that a weak "magnetic" background field could be originated from some "magnetogenesis" in the early Universe. We work on a low-energy effective model which can describe the chiral phase transition in a wide class of QCD-like theories. We show that in the case with massless (light) three flavors, the first-order feature goes away when 2f 2 π eB( (4πf π ) 2 ), where eB is the "magnetic" field strength and f π the pion decay constant at the vacuum. This disappearance is the generic consequence of the presence of the "magnetically" induced scale anomaly and the "magnetic" catalysis for the chiral symmetry breaking, and would impact or constrain modeling dark QCD coupled to an external "magnetic" field.

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Hypermagnetogenesis from axion inflation: Model-independent estimates

Cited by 4 publications

References 49 publications

Challenges in the choice of the nonconformal coupling function in inflationary magnetogenesis

Challenges in the choice of the nonconformal coupling function in inflationary magnetogenesis

On sphaleron heating in the presence of fermions

Fate of first-order chiral phase transition in QCD: Implications to dark QCD

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