Title: Opening up the QCD axion window

Abstract

We present a new mechanism to deplete the energy density of the QCD axion, making decay constants as high as f _a ≃ 10 ¹⁷ GeV viable for generic initial conditions. In our setup, the axion couples to a massless dark photon with a coupling that is moderately stronger than the axion coupling to gluons. Dark photons are produced copiously through a tachyonic instability when the axion field starts oscillating, and an exponential suppression of the axion density can be achieved. For a large part of the parameter space this dark radiation component of the universe can be observable in upcoming CMB experiments. Such dynamical depletion of the axion density ameliorates the isocurvature bound on the scale of inflation. The depletion also amplifies the power spectrum at scales that enter the horizon before particle production begins, potentially leading to axion miniclusters.

Authors:

Agrawal, Prateek ^[1]; Marques-Tavares, Gustavo ^[2]; Xue, Wei ^[3]

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+ Show Author Affiliations

1. Harvard Univ., Cambridge, MA (United States). Dept. of Physics
2. Stanford Univ., CA (United States). Stanford Institute for Theoretical Physics
3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics

Publication Date:

2018-03-08

Research Org.:

Stanford Univ., CA (United States); Massachusetts Inst. of Tech., Cambridge, MA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1499139

Grant/Contract Number:  

SC0012012; SC0012567; SC0015476

Resource Type:

Accepted Manuscript

Journal Name:

Journal of High Energy Physics (Online)

Additional Journal Information:

Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2018; Journal Issue: 3; Journal ID: ISSN 1029-8479

Publisher:

Springer Berlin

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS