Axion cosmology revisited

By Olivier Wantz, E. Shellard. 2009

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The misalignment mechanism for axion production depends on the temperature-dependent axion mass. The latter has recently been determined within the interacting instanton liquid model, and provides for the first time a well-motivated axion mass for all temperatures. We reexamine the constraints placed on the axion parameter space in the light of this new mass function. Taking this mass at face value, we find an accurate and updated constraint f{sub a{ =}}21({+-}2) {mu}eV from the misalignment mechanism in the classic axion window (thermal scenario). However, this is superseded by axion string radiation which leads to f{sub a} or approx. 0.20{sub -0.1}{sup +0.2} meV. In this analysis, we take care to precisely compute the effective degrees of freedom and, to fill a gap in the literature, we present accurate fitting formulas. We solve the evolution equations exactly, and find that analytic results used to date generally underestimate the full numerical solution by a factor 2-3. In the inflationary scenario, axions induce isocurvature fluctuations and constrain the allowed inflationary scale H{sub I}. Taking anharmonic effects into account, we show that these bounds are actually weaker than previouslymore » computed. Considering the fine-tuning issue of the misalignment angle in the whole of the anthropic window, we derive new bounds which open up the inflationary window near {theta}{sub a{yields}{pi}}. In particular, we find that inflationary dark matter axions can have masses as high as 0.01-1 meV, covering the whole thermal axion range, with values of H{sub I} up to 10{sup 9} GeV. Quantum fluctuations during inflation exclude dominant dark matter axions with masses above m{sub a} < or approx. 1 meV.« less

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/050af618860b287b8a26afed3f270c0e43fdf8e1

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Citations in the corpus

Towards a new generation axion helioscope (2011, background): “other hand, the unusual properties of axions allow them to be produced in the early universe as coherent field oscillations and as such to provide all or part of the cold dark matter [8, 9].”
Standard Model—axion—seesaw—Higgs portal inflation. Five problems of particle physics and cosmology solved in one stroke (2016, methodology): “These results for the topological susceptibility agree well with previous analytical calculations [35,172] at low temperature, where they lie between the predictions of IILM and the DIGA of [171], and follow the DIGA slope at high temperatures (as observed for quenched QCD in [171]).”
Cosmological bounds on pseudo Nambu-Goldstone bosons (2011, result): “The T dependences of gq and g∗ are taken from the recent analysis of [16].”
Using the Full Power of the Cosmic Microwave Background to Probe Axion Dark Matter (2017, background): “For the well-known case of QCD axion isocurvature (see e.g. Steinhardt & Turner 1983; Turner 1986; Turner & Wilczek 1991; Komatsu et al. 2009; Wantz & Shellard 2010; Visinelli & Gondolo 2010; Bennett et al. 2013), taking the DM to be entirely composed of the QCD axion, and assuming standard…”
Dark radiation constraints on minicharged particles in models with a hidden photon (2013, methodology): “Before the QCD phase transition (ΛQCD ∼ 180 MeV [100, 101]) we include all contributions from elementary particles with masses smaller than the W -bosons.”
The landscape of QCD axion models (2020, methodology): “29 To tackle this problem different techniques have been used, as for example a semi-analytical approach based on the interacting instanton liquid model [149, 150] or non-perturbative QCD lattice methods.”
Galaxy UV-luminosity function and reionization constraints on axion dark matter (2014, background): “For reviews of axion physics see Raffelt (2002); Wantz & Shellard (2010).”
Exploring the Role of Axions and Other WISPs in the Dark Universe (2012, background): “These extend the region where axions may provide cold dark matter to larger values of ma ∼ 10 eV [84, 85, 86].”
Cosmological Relaxation of the Electroweak Scale. (2015, background): “[22]), then φ remains in its original vacuum, though it can be displaced from its minimum.”