The ALP miracle revisited

Daido, Ryuji; Takahashi, Fuminobu; Yin, Wen

doi:10.1007/jhep02(2018)104

Cited by 97 publications

(115 citation statements)

References 131 publications

(221 reference statements)

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“…We will not attempt it in this article and just want to point out that there exist constructions based on the inflaton as an axion-like particle in Refs. [51,52] with Hubble scale around or below eV. In addition, there are two coincidences in energy scales.…”

Section: Other Possibility and Challengesmentioning

confidence: 95%

Dynamical axion misalignment with small instantons

Buen-Abad

Fan

2019

J. High Energ. Phys.

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We present a new mechanism to relax the initial misalignment angle of the QCD axion and raise the cosmological bound on the axion decay constant. The QCD axion receives a contribution from small UV instantons during inflation, which raises its mass to the inflationary Hubble scale. This makes the axion start rolling down its potential early on. In the scenario, the standard model Yukawa couplings of quarks are dynamical, being of order one during the inflationary era and reducing to their standard model values once it ends. This means that after inflation the contribution of the small instantons is suppressed, and the axion potential reduces to the standard one from the usual IR instantons. As a result, when the axion starts to oscillate again after inflation, the initial misalignment angle is suppressed due to the dynamics during inflation. While the general idea of dynamical axion misalignment has been discussed in the literature before, we present in detail the major bottleneck on the mismatching between the minima of the axion potentials during and after inflation, and how it is circumvented in our scenario via the Froggatt-Nielsen mechanism. Taking into account of all the constraints, we find that the axion decay constant could be raised to the GUT scale, 10 15 GeV, in our scenario.

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Section: Other Possibility and Challengesmentioning

confidence: 95%

Dynamical axion misalignment with small instantons

Buen-Abad

Fan

2019

J. High Energ. Phys.

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“…This is the case especially if φ has a coupling to the top quark, and the reheating temperature can be as high as T R = O(10 7−8 ) GeV for m φ = O(10 5−6 ) GeV [2,40]. Note that the PQ symmetry is not restored after inflation for the parameters of our interest, because the H inf is bounded above, H inf 1 GeV, for the QCD axion to acquire its potential during inflation.…”

Section: ∆N Effmentioning

confidence: 99%

“…(42)) due to the upside-down symmetry. Also, the inflaton mass m φ is related with the curvature at the potential maximum, which is bounded as |V inf (φ inf )| H 2 inf to satisfy the slow-roll condition [1,40]. In the figure we vary it in the following range,…”

Section: Axion Isocurvature Perturbationsmentioning

confidence: 99%

“…If the mass is sufficiently small, however, the inflaton becomes stable on a cosmological time scale. Even if the inflaton mass is small, the reheating proceeds through a combination of the perturbative decay and dissipation effects, and the inflaton condensate can completely evaporate [40]. In this case the inflaton particles are also thermalized in the plasma, contributing to hot DM (or dark radiation).…”

Section: Axion Isocurvature Perturbationsmentioning

confidence: 99%

“…In this case the inflaton particles are also thermalized in the plasma, contributing to hot DM (or dark radiation). The inflaton mass is constrained by the structure formation as [40,106]…”

Section: Axion Isocurvature Perturbationsmentioning

confidence: 99%

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QCD axion on hilltop by a phase shift of π.

Takahashi

Yin

2019

J. High Energ. Phys.

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We show that the initial misalignment angle of the QCD axion (or axion-like particles) can be set very close to π, if the QCD axion has a mixing with another heavy axion which induces the phase shift ≈ π after inflation. In the simplest case, the heavy axion plays the role of the inflaton, and we call such inflation as "πnflation." The basic idea was first proposed by Daido and the present authors in Ref.[1] in 2017 and more recently discussed in Ref. [2]. We show that the QCD axion with a decay constant f a 3 × 10 9 GeV can explain dark matter by the πnflation mechanism. A large fraction of the parameter region has an overlap with the projected sensitivity of ORGAN, MADMAX, TOORAD and IAXO. We also study implications for the effective neutrino species and isocurvature perturbations. The πnflation can provide an initial condition for the hilltop inflation in the axion landscape, and in a certain set-up, a chain of the hilltop inflation may take place. 1 arXiv:1908.06071v2 [hep-ph] 3 Oct 2019 5 The mass and kinetic mixings between the QCD axion and another axion were discussed in e.g. Refs. [41][42][43][44][45], where the level crossing between the two axions can reduce the axion abundance. The mixing can also induce the DM decay [1,46,47]. Also the mixing between axions plays an important role in inflation model building [48][49][50][51][52][53] 6 The axion isocurvature perturbations can be suppressed in this case [58]. See e.g. Refs. [14,26,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] for other scenarios to suppress the axion isocurvature.

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Solar Production of Ultralight Bosons

Vogel

Irastorza

2022

The Search for Ultralight Bosonic Dark Matter

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This chapter will spotlight axions produced in the core of the Sun. A first focus will be put on the production mechanism for axions in the solar interior through coupling of axions to photons via the Primakoff effect as well as their interactions with electrons. In addition to the axion production, the axion-to-photon conversion probability is a crucial quantity for solar axion searches (also referred to as helioscopes) and determines the expected number of photons from solar axion conversion that are detectable in a ground-based search. After these basic considerations, the helioscope concept will be detailed, and past, current, and future experimental realizations of axion helioscopes will be discussed. This includes the analysis used to aim at axion detection and upper limit calculations in case no signal above background is detected in experimental data. For completeness, alternative approaches other than traditional helioscopes to search for solar axions are discussed.

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The ALP miracle revisited

Cited by 97 publications

References 131 publications

Dynamical axion misalignment with small instantons

Dynamical axion misalignment with small instantons

QCD axion on hilltop by a phase shift of π.

Solar Production of Ultralight Bosons

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