Isocurvature constraints and anharmonic effects on QCD axion dark matter

Kobayashi, T.; Kurematsu, Ryosuke; Takahashi, Fuminobu

doi:10.1088/1475-7516/2013/09/032

Cited by 74 publications

(85 citation statements)

References 69 publications

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“…However we should also remark that the discussions are modified if the initial angle is as large as |θ | > 1; then the expansion (3.21) breaks down and the axion potential can no longer be approximated by a quadratic. The non-quadratic nature of the axion potential would lead to (i) an increase in the final axion DM density due to a delayed onset of the scalar oscillation [48,49], and (ii) a significant enhancement of the axion isocurvature due to a nonuniform onset of the oscillation, giving much stronger bounds on the inflation scale [50,51,52]. We also note that, besides such anharmonic initial conditions, a time-dependent m (e.g.…”

Section: Comments On Axion-like Fieldsmentioning

confidence: 86%

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

et al. 2017

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We investigate constraints on scalar dark matter (DM) by analyzing the Lyman-α forest, which probes structure formation at medium and small scales, and also by studying its cosmological consequences at high and low redshift. For scalar DM that constitutes more than 30% of the total DM density, we obtain a lower limit m 10 −21 eV for the mass of scalar DM. This implies an upper limit on the initial field displacement (or the decay constant for an axion-like field) of φ 10 16 GeV. We also derive limits on the energy scale of cosmic inflation and establish an upper bound on the tensor-to-scalar ratio of r < 10 −3 in the presence of scalar DM. Furthermore, we show that there is very little room for ultralight scalar DM to solve the "small-scale crisis" of cold DM without spoiling the Lyman-α forest results. The constraints presented in this paper can be used for testing generic theories that contain light scalar fields.

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Section: Comments On Axion-like Fieldsmentioning

confidence: 86%

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

et al. 2017

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“…The constraint becomes much more * email: ksjeong@tuhep.phys.tohoku.ac.jp † email: fumi@tuhep.phys.tohoku.ac.jp stringent for a smaller value of f a due to anharmonic effects [6,7]. Clearly, a chaotic inflation model [8][9][10][11] is in tension with the axion CDM.…”

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confidence: 99%

“…This constraint can be interpreted as an upper bound on the inflation scale in the axion CDM scenario [3], H inf < 0.87 × 10 7 GeV f a 10 11 GeV 0.408 , (2) at 95% CL, where f a is the axion decay constant [4,5]. The constraint becomes much more * email: ksjeong@tuhep.phys.tohoku.ac.jp † email: fumi@tuhep.phys.tohoku.ac.jp stringent for a smaller value of f a due to anharmonic effects [6,7]. Clearly, a chaotic inflation model [8][9][10][11] is in tension with the axion CDM.…”

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confidence: 99%

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Suppressing isocurvature perturbations of QCD axion dark matter

Jeong

Takahashi

2013

Physics Letters B

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We propose a novel mechanism to suppress the isocurvature perturbations of the QCD axion. The point is that the QCD interactions become strong at an intermediate or high energy scale in the very early Universe, if the Higgs field has a sufficiently large expectation value. The effective QCD scale can be even higher in the presence of extra colored particles. We show that the QCD axion then becomes so heavy during inflation that its isocurvature perturbations are significantly suppressed, thereby relaxing the constraint on the inflation scale.The axion a is a Nambu-Goldstone boson associated with the spontaneous breakdown of the Peccei-Quinn (PQ) symmetry introduced to solve the strong CP problem in quantum chromodynamics (QCD) [1,2]. The axion acquires a tiny but non-zero mass from the QCD instanton effects, and it is stabilized at the CP conserving vacuum. The dynamical relaxation of the CP phase necessarily induces coherent oscillations of the axion, which contribute to cold dark matter (CDM) as the axion is stable in a cosmological time scale.If the axion is present during inflation, it is subject to quantum fluctuations,where H inf denotes the Hubble parameter during inflation. The quantum fluctuations lead to an almost scale-invariant CDM isocurvature density fluctuation, which leaves a distinctive imprint on the cosmic microwave background (CMB) spectrum. The observed CMB spectrum can be well fitted by a nearly scale-invariant adiabatic density perturbation, and a mixture of the isocurvature perturbation is tightly constrained. This constraint can be interpreted as an upper bound on the inflation scale in the axion CDM scenario [3],at 95% CL, where f a is the axion decay constant [4,5]. The constraint becomes much more * email: ksjeong@tuhep.phys.tohoku.ac.jp † email: fumi@tuhep.phys.tohoku.ac.jp stringent for a smaller value of f a due to anharmonic effects [6,7]. Clearly, a chaotic inflation model [8][9][10][11] is in tension with the axion CDM. There are several known ways to avoid the constraint. First, if the PQ symmetry is restored during inflation, the axion does not exist, and so there is no isocurvature perturbation [12,13]. The axion appears when the PQ symmetry is spontaneous broken after inflation. In such case, however, topological defects such as cosmic strings and domain walls are generated, and in particular the domain wall number must be unity to avoid the overclosure of the Universe. Secondly, if the coefficient of the axion kinetic term was larger during inflation than at present, the size of δa can be suppressed. This can be realized if the radial component of the PQ scalar has a flat potential and takes a larger value during inflation [12,14]. Alternatively, a similar effect is possible if there is a non-minimal coupling to gravity [15].In this letter we propose another way to relax the isocurvature constraint on the inflation scale in the axion CDM scenario. The point is that, if the Higgs field has a sufficiently large expectation value during inflation, the QCD confines at an interm...

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“…Before going further, let us discuss anharmonic effects, which have been neglected so far. The axion abundance produced from the coherent oscillation is enhanced if the initial axion position is close to the hilltop [69][70][71][72][73], where the axion potential is not approximated by a quadratic potential. Such effects can be included by taking 16) in the relation for the axion density (3.8), with F given by [72] 17) for 0 ≤ z < π 2 .…”

Section: Jhep07(2014)092mentioning

confidence: 99%

String theoretic QCD axions in the light of PLANCK and BICEP2

Choi

Jeong

Seo

2014

J. High Energ. Phys.

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The QCD axion solving the strong CP problem may originate from antisymmetric tensor gauge fields in compactified string theory, with a decay constant around the GUT scale. Such possibility appears to be ruled out now by the detection of tensor modes by BICEP2 and the PLANCK constraints on isocurvature density perturbations. A more interesting and still viable possibility is that the string theoretic QCD axion is charged under an anomalous U(1) A gauge symmetry. In such case, the axion decay constant can be much lower than the GUT scale if moduli are stabilized near the point of vanishing Fayet-Illiopoulos term, and U(1) A -charged matter fields get a vacuum value v ∼ (m SUSY M n P l ) 1/(n+1) (n ≥ 0) induced by a tachyonic SUSY breaking mass m SUSY . We examine the symmetry breaking pattern of such models during the inflationary epoch with H I ≃ 10 14 GeV, and identify the range of the QCD axion decay constant, as well as the corresponding relic axion abundance, consistent with known cosmological constraints. In addition to the case that the PQ symmetry is restored during inflation, i.e. v(t I ) = 0, there are other viable scenarios, including that the PQ symmetry is broken during inflation with v(t I ) ∼ (4πH I M n P l ) 1/(n+1) ∼ 10 16 -10 17 GeV due to the Hubble-induced D-termGeV in the present universe, where v(t 0 ) above 10 12 GeV requires a fine-tuning of the axion misalignment angle. We also discuss the implications of our results for the size of SUSY breaking soft masses.

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Isocurvature constraints and anharmonic effects on QCD axion dark matter

Cited by 74 publications

References 69 publications

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

Suppressing isocurvature perturbations of QCD axion dark matter

String theoretic QCD axions in the light of PLANCK and BICEP2

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