Year: 2022
Type: article
Abstract: Pairs of misalignment-produced axions with nearby masses can experience a nonlinear resonance that leads to enhanced direct and astrophysical signatures of axion dark matter. In much of the relevant parameter space, self-interactions cause axion fluctuations to become nonperturbative and to collapse in the early Universe. We investigate the observational consequences of such nonperturbative structure in this ``friendly axion'' scenario with $3+1$ dimensional simulations. Critically, in a substantial fraction of parameter space we find that nonlinear dynamics work to equilibrate the abundance of the two axions, making it easier than previously expected to experimentally confirm the existence of a resonant pair. We also compute the gravitational wave emission from friendly axion dark matter; while the resulting stochastic background is likely undetectable for axion masses above ${10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$, the polarization of the cosmic microwave background does constrain possible hyperlight, friendly subcomponents. Finally, we demonstrate that dense, self-interaction--bound oscillons formed during the period of strong nonlinearity are driven by the homogeneous axion background, enhancing their lifetime beyond the in-vacuum expectation.
Institutions: University of Washington, Stanford University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Funders: National Science Foundation, Gordon and Betty Moore Foundation, Stanford University, Purdue University, University of Washington, Achievement Rewards for College Scientists Foundation, Innovation, Science and Economic Development Canada, San Diego Supercomputer Center, Government of Canada, Ontario Ministry of Research, Innovation and Science, Institut Périmètre de physique théorique, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Division of Graduate Education
Awards: Theory For New Fundamental Physics Experiments, G3226045097, XSEDE 2.0: Integrating, Enabling and Enhancing National Cyberinfrastructure with Expanding Community Involvement, G5902304706, G5968306201, Research in Particle Theory, Cosmology, and Quantum Gravity, Category I: Bridges-2: Scalable Converged Computing, Data, and Analytics for Rapidly Evolving Science and Engineering Research
OpenAlex ID: W4302007909