Axion dark matter and Planck favor non-minimal couplings to gravity

Folkerts, Sarah; Germani, Cristiano; Redondo, Javier

doi:10.1016/j.physletb.2013.12.026

Cited by 43 publications

(41 citation statements)

References 82 publications

(113 reference statements)

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“…In the case where the ALP is subdominant the non-Gaussianity could be visible even before one detects the isocurvature modes themselves [12]. However, note that the isocurvature perturbations are suppressed in some particular models [13].…”

Section: A Simple Alp Explanationmentioning

confidence: 99%

3.55 keV hint for decaying axionlike particle dark matter

Jaeckel¹,

2014

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Recently, indications for an emission line at 3.55 keV have been found in the combined spectra of a large number of galaxy clusters and also in Andromeda. This line could not be identified with any known spectral line. It is tempting to speculate that it has its origin in the decay of a particle contributing all or part of the dark matter. In this paper we want to point out that axionlike particles being all or part of the dark matter are an ideal candidate to produce such a feature. More importantly the parameter values necessary are quite feasible in extensions of the Standard Model based on string theory and could be linked up to a variety of other intriguing phenomena, which also potentially allow for new tests of this speculation.

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Section: A Simple Alp Explanationmentioning

confidence: 99%

3.55 keV hint for decaying axionlike particle dark matter

Jaeckel¹,

2014

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“…[35,36] for the case where the PQ breaking scale, and therefore the coefficient of the kinetic term for the axion, significantly evolves after inflation, which would suppress/enhance the axion quantum fluctuations. A similar effect is possible if there is a non-minimal coupling to gravity [37]. It is also possible to make the axion so heavy during inflation that its quantum fluctuations are suppressed if the QCD becomes strong at an intermediate or high energy scale [5].…”

Section: Axion Dark Mattermentioning

confidence: 99%

Isocurvature constraints and anharmonic effects on QCD axion dark matter

Kobayashi

Kurematsu

Takahashi

2013

J. Cosmol. Astropart. Phys.

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We revisit the isocurvature density perturbations induced by quantum fluctuations of the axion field by extending a recently developed analytic method and approximations to a time-dependent scalar potential, which enables us to follow the evolution of the axion until it starts to oscillate. We find that, as the initial misalignment angle approaches the hilltop of the potential, the isocurvature perturbations become significantly enhanced, while the non-Gaussianity parameter increases slowly but surely. As a result, the isocurvature constraint on the inflation scale is tightened as H inf O(100) GeV for the axion decay constant f a 10 10 GeV, near the smaller end of the axion dark matter window. We also derive useful formulae for the power spectrum and non-Gaussianity of the isocurvature perturbations.

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“…Fourthly, non-trivial axion dynamics during inflation suppressing isocurvature are possible e.g. via non-minimal coupling to gravity [58] or coupling the inflation directly to the sector providing non-perturbative effects, e.g. the QCD coupling [59,60].…”

Section: Introductionmentioning

confidence: 99%

Tensor Interpretation of BICEP2 Results Severely Constrains Axion Dark Matter

et al. 2014

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The recent detection of B-modes by BICEP2 has non-trivial implications for axion dark matter implied by combining the tensor interpretation with isocurvature constraints from Planck. In this paper the measurement is taken as fact, and its implications considered, though further experimental verification is required. In the simplest inflation models r = 0.2 implies HI = 1.1 × 10 14 GeV. If the axion decay constant fa < HI /2π constraints on the dark matter (DM) abundance alone rule out the QCD axion as DM for ma 52χ 6/7 µeV (where χ > 1 accounts for theoretical uncertainty). If fa > HI /2π then vacuum fluctuations of the axion field place conflicting demands on axion DM: isocurvature constraints require a DM abundance which is too small to be reached when the back reaction of fluctuations is included. High fa QCD axions are thus ruled out. Constraints on axionlike particles, as a function of their mass and DM fraction, are also considered. For heavy axions with ma 10 −22 eV we find Ωa/Ω d 10 −3 , with stronger constraints on heavier axions. Lighter axions, however, are allowed and (inflationary) model-independent constraints from the CMB temperature power spectrum and large scale structure are stronger than those implied by tensor modes. −0.05 has profound implications for our understanding of the initial conditions of the universe [2], and points to an inflationary origin for the primordial fluctuations [3][4][5]. The inflaton also drives fluctuations in any other fields present in the primordial epoch and so the measurement of r, which fixes the inflationary energy scale, can powerfully constrain diverse physics. In this work we will discuss the implications for axion dark matter (DM) in the case that the tensor modes are generated during single-field slow-roll inflation (from now on we simply refer to this as 'inflation') by zero-point fluctuations of the graviton. In this work we assume that the measured value of r both holds up to closer scrutiny experimentally, and is taken to be of primordial origin. We relax these assumptions in our closing discussion. We stress that our conclusions are one consequence of taking this measurement at face value, but also that they apply to any detection of r.The scalar amplitude of perturbations generated during inflation is given by [7]

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Axion dark matter and Planck favor non-minimal couplings to gravity

Cited by 43 publications

References 82 publications

3.55 keV hint for decaying axionlike particle dark matter

3.55 keV hint for decaying axionlike particle dark matter

Isocurvature constraints and anharmonic effects on QCD axion dark matter

Tensor Interpretation of BICEP2 Results Severely Constrains Axion Dark Matter

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