Abstract
As-yet undiscovered light bosons may constitute all or part of the dark matter (DM) of our Universe, and are expected to have (weak) self-interactions. We show that the quartic self-interactions generically induce the capture of dark matter from the surrounding halo by external gravitational potentials such as those of stars, including the Sun. This leads to the subsequent formation of dark matter bound states supported by such external potentials, resembling gravitational atoms (e.g. a solar halo around our own Sun). Their growth is governed by the ratio ξ foc ≡ λdB/R ⋆ between the de Broglie wavelength of the incoming DM waves, λdB, and the radius of the ground state R ⋆. For ξ foc ≲ 1, the gravitational atom grows to an (underdense) steady state that balances the capture of particles and the inverse (stripping) process. For ξ foc ≳ 1, a significant gravitational-focusing effect leads to exponential accumulation of mass from the galactic DM halo into the gravitational atom. For instance, a dark matter axion with mass of the order of 10-14 eV and decay constant between 107 and 108 GeV would form a dense halo around the Sun on a timescale comparable to the lifetime of the Solar System, leading to a local DM density at the position of the Earth O(104) times larger than that expected in the standard halo model. For attractive self-interactions, after its formation, the gravitational atom is destabilized at a large density, which leads to its collapse; this is likely to be accompanied by emission of relativistic bosons (a `Bosenova').
Original language | English |
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Article number | 021 |
Number of pages | 67 |
Journal | Journal of Cosmology and Astroparticle Physics |
Volume | 2023 |
Issue number | 12 |
DOIs | |
Publication status | Published - Dec 2023 |
Funding
The authors are grateful to Hyungjin Kim and Christopher McKee for crucial contributions in the early stages of this work. The authors thank Kfir Blum, Elisa Ferreira, Ricardo Ferreira, Ed Hardy, Oleksii Matsedonskyi, Mehrdad Mirbabayi, Wolfram Ratzinger, Giovanni Villadoro, and Wei Xue for valuable discussions. The authors also thank Kfir Blum, Yifan Chen, Ed Hardy, David J.E. Marsh and Wei Xue for insightful feedbacks on a draft. MG is grateful to Ed Hardy for substantial contributions to the Schrödinger-Poisson code used for the numerical results of this paper. The work of DB was supported in part by the Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA+ EXC 2118/1) and the German-Israeli Foundation (GIF). The work of JE was supported by the World Premier International Research Center Initiative (WPI), MEXT, Japan and by the JSPS KAKENHI Grant Numbers 21H05451 and 21K20366. The work of MJ is supported by a research grant from the Musk Foundation. The work of GP is supported by grants from BSF-NSF, Friedrich Wilhelm Bessel research award of the Alexander von Humboldt Foundation, GIF, ISF, Minerva, SABRA — Yeda-Sela — WRC Program, the Estate of Emile Mimran, and the Maurice and Vivienne Wohl Endowment.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics