QCD Axion Kinetic Misalignment without Prejudice

Barman, Basabendu; Bernal, Nicolás; Ramberg, Nicklas; Visinelli, Luca

doi:10.48550/arxiv.2111.03677

Cited by 7 publications

(8 citation statements)

References 116 publications

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“…Our work is based on the kinetic misalignment scenario [47][48][49], but should easily also apply to other models such as trapped misalignment [50,51]. Kinetically misaligned axions are attractive for model building and phenomenology [52,53], since they can explain the baryon asymmetry [47,[54][55][56][57] and modify the spectrum of long lasting primordial GW sources [58][59][60]. Furthermore, in combination with dark photons, GWs are produced along with vector dark matter.…”

Section: Introductionmentioning

confidence: 99%

Audible axions with a booster: Stochastic gravitational waves from rotating ALPs

et al. 2022

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Gravitational waves provide a novel way to probe axions or axion-like particles coupled to a dark photon field, even in the absence of couplings to Standard Model particles. In the conventional misalignment mechanism, the generation of an observable stochastic gravitational wave background, however, requires large axion decay constants. We here investigate the gravitational wave signal generated within the kinetic misalignment scenario, where the axion is assumed to have a large initial velocity. Its kinetic energy then provides a sufficiently high energy budget to generate a detectable gravitational wave signal also at lower values of the decay constant. We obtain an analytic estimate as well as perform numerical simulations of the corresponding gravitational wave signal, and evaluate its detectability at current and future gravitational wave observatories. We further present the corresponding projected constraints on the parameter space of the model, along with the parameter regions in which the dark photon or axion constitute dark matter, or in which the baryon asymmetry of the Universe is generated via the axiogenesis mechanism. Finally, we compute the GW production from the fragmentation of rotating axions, which is however difficult to observe experimentally.

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Section: Introductionmentioning

confidence: 99%

Audible axions with a booster: Stochastic gravitational waves from rotating ALPs

et al. 2022

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“…Let us now describe in brief the kinetic axion mechanism in order to better understand the new quantitative effects that the R 2 term brings along in the theory. For details on the kinetic axion mechanism see for example [14][15][16]. In the context of the kinetic axion mechanism, the axion primordially has an unbroken U (1) Peccei-Quinn symmetry, which is broken during the inflationary era.…”

Section: The R 2 -Corrected Kinetic Misalignment Axion Model and Its ...mentioning

confidence: 99%

“…In the recent literature, the terminology axion refers to an axion like particle, but not to the QCD axion. The axion scalar has a primordial pre-inflationary U (1) Peccei-Quinn symmetry, which is broken during inflation in the most popular axion models, which are the canonical misalignment axion [10] and the kinetic misalignment axion [14][15][16]. In both the models the U (1) Peccei-Quinn symmetry is broken during the inflationary era, and the axion obtains a large vacuum expectation and rolls to its vacuum expectation value which is the minimum of the potential The major difference between the two models is that in the case of the canonical misalignment axion model, the axion has zero kinetic energy initially, so when the axion reaches the minimum of the potential, which is its vacuum expectation value, the axion commences oscillations and thereafter redshifts as cold dark matter.…”

Section: Introductionmentioning

confidence: 99%

$R^2$ Gravity Effects on the Kinetic Axion Phase Space

Oikonomou¹

2022

Preprint

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In this work we consider the effect of an R 2 term on the kinetic misalignment axion theory. By using the slow-roll assumptions during inflation and the field equations, we construct an autonomous dynamical system for the kinetic axion, including the effects of the R 2 term and we solve numerically the dynamical system. As we demonstrate, the pure kinetic axion attractor is transposed to the right in the field phase space, and it is no longer (φ, φ) = ( φ , 0), but it is (φ, φ) = ( φ , 0), with φ = 0 some non-zero value of the scalar field with φ > φ . This feature indicates that the kinetic axion mechanism is enhanced, and the axion oscillations are further delayed, compared with the pure kinetic axion case. The phenomenological implications on the duration of the inflationary era, on the commencing of the reheating era and the reheating temperature, are also discussed.

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“…To our opinion, the axion is the last resort of particle dark matter, but the predicted mass is too tiny to be measured at present day. We shall consider two mainstream axion models, the canonical misalignment model [60] and the recently developed kinetic axion model [66][67][68]. Chern-Simons theories are possible candidate theories toward describing the primordial era of our Universe, see Refs.…”

Section: Introductionmentioning

confidence: 99%

Chirality of Gravitational Waves in Chern-Simons $f(R)$ Gravity Cosmology

Odintsov,

Oikonomou

2022

Preprint

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In this paper we shall consider an axionic Chern-Simons corrected f (R) gravity theoretical framework, and we shall study the chirality of the generated primordial gravitational waves. Particularly, we shall consider two main axion models, the canonical misalignment axion model and the kinetic axion model, both of which provide an interesting particle phenomenology, in the presence of R 2 terms in the inflationary Lagrangian. The axion does not affect significantly the background evolution during the inflationary era, which is solely controlled by R 2 gravity. However, the due to the presence of the Chern-Simons term, the tensor perturbations are directly affected, and our aim is to reveal the extent of effects of the Chern-Simons term on the gravitational waves modes, for both the axion models. We aim to produce analytical descriptions of the primordial tensor modes behavior, and thus we solve analytically the evolution equations of the tensor modes, for a nearly de Sitter primordial evolution controlled by the R 2 gravity. We focus the analytical study on superhorizon and subhorizon modes. For the misalignment model, we were able to produce analytic solutions for both the subhorizon and superhorizon modes, in which case we found the behavior of the circular polarization function. Our results indicate that the produced tensor spectrum is strongly chiral. For the kinetic axion model though, analytic solutions are obtained only for the superhorizon modes. In order to have a grasp of the behavior of the chirality of the tensor modes, we studied the chirality of the superhorizon modes, however a more complete study is needed, which is impossible to do analytically though.

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QCD Axion Kinetic Misalignment without Prejudice

Cited by 7 publications

References 116 publications

Audible axions with a booster: Stochastic gravitational waves from rotating ALPs

Audible axions with a booster: Stochastic gravitational waves from rotating ALPs

$R^2$ Gravity Effects on the Kinetic Axion Phase Space

Chirality of Gravitational Waves in Chern-Simons $f(R)$ Gravity Cosmology

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