Axion misalignment driven to the bottom

Journal Article · 27 May 2019 · Journal of High Energy Physics (Online)

DOI: https://doi.org/10.1007/JHEP05(2019)162 · OSTI ID:1596298

Co, Raymond T.  ^[1]; Gonzalez, Eric ^[2]; Harigaya, Keisuke ^[3]

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1. Univ. of Michigan, Ann Arbor, MI (United States). Leinweber Center for Theoretical Physics; Institute for Advanced Study
2. Univ. of Michigan, Ann Arbor, MI (United States). Leinweber Center for Theoretical Physics
3. Inst. for Advanced Study, Princeton, NJ (United States)

Several theoretical motivations point to ultralight QCD axions with large decay constants $$f_a \simeq \mathcal{O}(10^{16}-10^{17})$$ GeV, to which experimental proposals are dedicated. This regime is known to face the problem of overproduction of axion dark matter from the misalignment mechanism unless the misalignment angle $$\theta_{\rm mis}$$ is as small as $$\mathcal{O}(10^{-3}-10^{-4})$$, which is generally considered a fine-tuning problem. We investigate a dynamical explanation for a small $$\theta_{\rm mis}$$. The axion mass arises from strong dynamics and may be sufficiently enhanced by early dynamics so as to overcome Hubble friction and drive the field value to the bottom of the potential long before the QCD phase transition. Together with an approximate CP symmetry in the theory, this minimum is very closely related to today's value and thus $$\theta_{\rm mis}$$ can automatically be well under unity. Owing to such efficient relaxation, the isocurvature perturbations are essentially damped. As an existence proof, using supersymmetric theories we illustrate that the Higgs coupling with the inflaton energy can successfully achieve this axion damping in a consistent inflationary cosmology.

• Research Organization: Inst. for Advanced Study, Princeton, NJ (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0009988; SC0019225
• OSTI ID: 1596298
• Journal Information: Journal of High Energy Physics (Online), Journal Name: Journal of High Energy Physics (Online) Journal Issue: 5 Vol. 2019; ISSN 1029-8479
• Publisher: Springer BerlinCopyright Statement
• Country of Publication: United States
• Language: English