Axion misalignment driven to the bottom

Co, Raymond T.; González, E.; Harigaya, Keisuke

doi:10.1007/jhep05(2019)162

Cited by 47 publications

(35 citation statements)

References 70 publications

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“…The easiest way to understand why the suppression at small scales is even stronger than at CMB scales is by replacing k CMB by the much larger k in Eq. (54). All this means that the discussion in Sec.…”

Section: Energy Density In Fluctuationsmentioning

confidence: 95%

See 1 more Smart Citation

Misalignment & Co.: (pseudo-)scalar and vector dark matter with curvature couplings

Alonso-Álvarez

Hügle

Jaeckel

2020

J. Cosmol. Astropart. Phys.

106

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Section: Energy Density In Fluctuationsmentioning

confidence: 95%

“…Additional contributions may arise from production via inflationary fluctuations [42][43][44][45][46][47] as well as from decays of precursor particles [48][49][50][51][52][53]. Modifications to the usual misalignment mechanism have been for example explored in [54,55].…”

Section: Introductionmentioning

confidence: 99%

Misalignment & Co.: (pseudo-)scalar and vector dark matter with curvature couplings

Alonso-Álvarez

Hügle

Jaeckel

2020

J. Cosmol. Astropart. Phys.

106

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“…Even when one requires that this explicit breaking not spoil the solution to the Strong CP problem in the present universe, the rotation can still be induced from such interactions in the early universe as we will describe. Another example is a larger QCD scale in the early universe [30][31][32][33], which can initiate the axion oscillation and, once the QCD scale becomes small enough, the axion begins to rotate.A fast rotation of the axion corresponds to a large PQ charge asymmetry. The PQ asymmetry is converted into chiral asymmetries of SM quarks via QCD sphaleron transitions.…”

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confidence: 99%

Axiogenesis

2020

Self Cite

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We propose a mechanism called axiogenesis where the cosmological excess of baryons over antibaryons is generated from the rotation of the QCD axion. The Peccei-Quinn (PQ) symmetry may be explicitly broken in the early universe, inducing the rotation of a PQ charged scalar field. The rotation corresponds to the asymmetry of the PQ charge, which is converted into the baryon asymmetry via QCD and electroweak sphaleron transitions. In the concrete model we explore, interesting phenomenology arises due to the prediction of a small decay constant and the connections with new physics at the LHC and future colliders and with axion dark matter.Introduction.-One of the goals of fundamental physics is to understand the origin of the Universe. For this purpose, the Standard Model (SM) of particle physics needs an extension to explain the cosmological excess of matter over antimatter. Mechanisms to generate the baryon asymmetry have been intensively studied in the literature under the name of baryogenesis [1][2][3][4][5][6][7][8].The SM also needs an extension to explain the smallness of CP violation in QCD [9] which on theoretical grounds is expected to be large [10]. This is known as the strong CP problem and can be elegantly solved by the Peccei-Quinn (PQ) mechanism [11,12]. The so-called the PQ symmetry is spontaneously broken to yield a pseudo Nambu-Goldstone boson, the axion [13,14]. The PQ symmetry is explicitly broken by the quantum effects of QCD of the Adler-Bell-Jeckiw type [15,16]. The quantum effects give a potential to the axion and drive the axion field value to the point where CP symmetry is restored, solving the strong CP problem. The axion is also a dark matter candidate [17][18][19], which makes the PQ mechanism even more attractive.We discover that when the PQ mechanism is introduced into the SM, the baryon (B) and lepton (L) asymmetries are generated in a wide class of models. We call the following baryogenesis scheme as axiogenesis, which in general includes two main ingredients: 1) an asymmetry of the PQ charge is generated in the early universe as a coherent rotation in the axion direction and 2) the PQ asymmetry is later transferred to the B + L asymmetry via the QCD and electroweak sphaleron transitions. We contrast axiogenesis with other existing baryogenesis models after we introduce a concrete example. (We may convert the B + L asymmetry into the B − L asymmetry by some B − L breaking interaction. The investigation of such a scenario will be considered in a future work [20].)The PQ symmetry is an approximate global symmetry which is explicitly broken by the QCD anomaly. Given that the symmetry is not exact, it is conceivable that the PQ symmetry is significantly broken in the early universe, and the rotation of the axion is induced. In fact, it is expected that quantum gravity does not allow for a global symmetry [21][22][23][24][25] and the PQ symmetry is at best understood as an accidental symmetry explicitly broken by higher dimensional operators [26][27][28][29]. Even when one requires that t...

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“…Yet recently Ref. [24] revisited this possibility and showed that if the Hubble induced Higgs mass squared parameter is negative and the Higgs field takes a large value along the flat direction in the supersymmetric scenario, one could make QCD strong enough to raise the axion mass to about or above the inflationary Hubble scale. One major challenge in this scenario is whether the minima of the potentials during and after inflation are sufficiently close to each other.…”

Section: Introductionmentioning

confidence: 99%

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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Axion misalignment driven to the bottom

Cited by 47 publications

References 70 publications

Misalignment & Co.: (pseudo-)scalar and vector dark matter with curvature couplings

Misalignment & Co.: (pseudo-)scalar and vector dark matter with curvature couplings

Axiogenesis

Dynamical axion misalignment with small instantons

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