Development of axion perturbations in an axion dominated universe

Axenides, Minos; Brandenberger, Robert H.; Turner, Michael S.

doi:10.1016/0370-2693(83)90586-5

Cited by 143 publications

(144 citation statements)

References 22 publications

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“…[27]). Along with the QCD axion we will also consider constraints on other axions coming from a measurement of r. Just as the graviton is massless during inflation, leading to the production of the tensor modes, if the axion is massless during inflation (and the PQ symmetry is broken) it acquires isocurvature perturbations [28,29] …”

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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Section: Introductionmentioning

confidence: 99%

Tensor Interpretation of BICEP2 Results Severely Constrains Axion Dark Matter

et al. 2014

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“…Another example is the generation of axion fluctuations (see e.g. [4]). Recently, the super-Hubble range effects of entropy fluctuations have been widely studied in the context of inflationary reheating (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Super-Hubble nonlinear perturbations during inflation

Afshordi

Brandenberger

2001

Phys. Rev. D

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We show that the non-linear evolution of long-wavelength perturbations may be important in a wide class of inflationary scenarios. We develop a solution for the evolution of such nonlinear perturbations which is exact to first order in a gradient expansion. As a first application, we demonstrate that in single field models of inflation there can be no parametric amplification of super-Hubble modes during reheating. We consider the implications of the solution for recent discussions of the backreaction effect of long wavelength perturbations on the background geometry, give a new derivation of the equation of motion of stochastic inflation, and demonstrate that if the (generalized) slowrolling condition is not satisfied, then inevitably long wavelength vector modes for gravitational fluctuations will be generated.

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“…This latter effect was studied [12] in the context of axion perturbations, and [13] in the context of the baryon isocurvature model [14]. This effect is also responsible for the growth of super-Hubble adiabatic perturbations during preheating [15].…”

Section: Introductionmentioning

confidence: 99%

“…This effect is also responsible for the growth of super-Hubble adiabatic perturbations during preheating [15]. Considering axions as Cold Dark Matter (CDM) [12], an isocurvature perturbation due to the angle misalignment produced during inflation induces an adiabatic component of comparable amplitude at the moment of reentry of the perturbation inside the Hubble radius. This is due to the fact that the CDM component is going to dominate about the time of decoupling, and thus the integrated effect is almost completed by the time that mode reenters inside the Hubble radius.…”

Section: Introductionmentioning

confidence: 99%