Axions: Theory and Cosmological Role

Kawasaki, Masahiro; Nakayama, Kazunori

doi:10.1146/annurev-nucl-102212-170536

Cited by 256 publications

(291 citation statements)

References 217 publications

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“…In addition to these constraints, we have also investigated constraints coming from the Cosmic Microwave Background (CMB), reionization and the effective number of neutrinos along the lines of [61][62][63] 5 (see [64] for a review). But since these constraints are relatively weak and covered by the BBN and the diffuse γ-ray background, we do not exhibit them here.…”

Section: Jhep01(2014)049 4 Cosmological Constraintsmentioning

confidence: 99%

Discrete gauge symmetry and Aharonov-Bohm radiation in string theory

Ookouchi

2014

J. High Energ. Phys.

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Section: Jhep01(2014)049 4 Cosmological Constraintsmentioning

confidence: 99%

Discrete gauge symmetry and Aharonov-Bohm radiation in string theory

Ookouchi

2014

J. High Energ. Phys.

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“…refs. [11][12][13][14][15][16] for reviews on the QCD axion and the related topics. Axions are also known to appear in string theory in association with compactification of the extra dimension, and some of them may be so light that they play an important role in cosmology [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Topological defects and nano-Hz gravitational waves in aligned axion models

Higaki

Jeong

Kitajima

et al. 2016

J. High Energ. Phys.

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We study the formation and evolution of topological defects in an aligned axion model with multiple Peccei-Quinn scalars, where the QCD axion is realized by a certain combination of the axions with decay constants much smaller than the conventional PecceiQuinn breaking scale. When the underlying U(1) symmetries are spontaneously broken, the aligned structure in the axion field space exhibits itself as a complicated string-wall network in the real space. We find that the string-wall network likely survives until the QCD phase transition if the number of the Peccei-Quinn scalars is greater than two. The stringwall system collapses during the QCD phase transition, producing a significant amount of gravitational waves in the nano-Hz range at present. The typical decay constant is constrained to be below O(100) TeV by the pulsar timing observations, and the constraint will be improved by a factor of 2 in the future SKA observations.

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“…Unlike the previous case, universe does not settle into the same minimum when the axion acquires its mass at the QCD scale and ends up forming topological defects [76]. Now, 43 the misalignment axion cold dark matter energy density is given by [77] Ω a,mis h 2 = 2.07 f a 10 12 GeV 7 /6 (45) while Ω a h 2 = 2.07(1 + α dec ) f a 10 12 GeV 7 /6 (46) where α dec = 0.164 corresponds to the factor introduced due to the decay of topological defects like axionic strings [77].…”

Section: Pq-symmetry Breaking After Inflationmentioning

confidence: 82%

A minimal non-supersymmetric S O(10) model: Gauge coupling unification, proton decay and fermion masses

Khan

2016

AIP Conference Proceedings

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We present a minimal renormalizable non-supersymmetric SO(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54 H + 126 H + 10 H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 10 35 yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of τ p 1.29 × 10 34 yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, M I ≈ (10 13 − 10 14 ) GeV which is also the B − L scale, is of the right order for the righthanded neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p → e + π 0 and p → νπ + . Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario. *

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Axions: Theory and Cosmological Role

Abstract: We review recent developments on axion cosmology. Topics include : axion cold dark matter, axions from topological defects, axion isocurvature perturbation and its non-Gaussianity and axino/saxion cosmology in supersymmetric axion model.

Cited by 256 publications

References 217 publications

Discrete gauge symmetry and Aharonov-Bohm radiation in string theory

Discrete gauge symmetry and Aharonov-Bohm radiation in string theory

Topological defects and nano-Hz gravitational waves in aligned axion models

A minimal non-supersymmetric S O(10) model: Gauge coupling unification, proton decay and fermion masses

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