The cosmology of ultralight scalar dark matter coupled to right-handed neutrinos
Abstract
We consider ultralight scalar dark matter that couples to right-handed neutrinos. Due to the high density of neutrinos in the early universe, the background neutrino density dominates the dynamics of the scalar field, and qualitatively alters the field's cosmological evolution. This effect has not been included in previous literature, and changes the interpretation of cosmological data and its interplay with laboratory experiments. To illustrate these points a simplified model of a 1 + 1 setup with a single scalar field is analyzed. We find that: i) The scalar field experiences an asymmetric potential and its energy density redshifts differently than ordinary matter. ii) Neutrino mass measurements at the CMB and oscillation experiments performed today complement one another (i.e., they constrain different regions of parameter space). iii) There exists potentially interesting cosmologies with either O(1) variations in the dark matter density between the CMB and today, or O(1) oscillations of neutrino mass.
Copyright and License
© 2025 The Authors. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.
Article funded by SCOAP3.
Acknowledgement
We thank Mark Wise for collaboration during early stages of this work. We thank Dave McKeen, Linda Xu, Kim Berghaus, Matheus Hostert, Saurunas Verner, Yohei Ema, and especially Gordan Krnjaic Akshay Ghalsasi and Nashwan Sabti for helpful discussions. We are grateful to Mark Wise, Pedro Machado, Clara Murgui, Akshay Ghalsasi, Kim Berghaus, Leonardo Badurina, and the anonymous referee for feedback on of the manuscript.
Funding
RP is supported by the Neutrino Theory Network under Award Number DEAC02-07CH11359. RP and ST are supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011632, and by the Walter Burke Institute for Theoretical Physics.
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Additional details
- United States Department of Energy
- DE-AC02-07CH11359
- United States Department of Energy
- DE-SC0011632
- SCOAP3
- Accepted
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2025-05-27
- Available
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2025-07-01Published
- Caltech groups
- Walter Burke Institute for Theoretical Physics, Division of Physics, Mathematics and Astronomy (PMA)
- Publication Status
- Published