A step in understanding the 𝑆₈ tension
Files
Accepted manuscript
Date
2023-07-21
Authors
Joseph, Melissa
Aloni, Daniel
Schmaltz, Martin
Sivarajan, Eashwar N.
Weiner, Neal
Version
Accepted manuscript
OA Version
Citation
M. Joseph, D. Aloni, M. Schmaltz, E.N. Sivarajan, N. Weiner. "A Step in understanding the 𝑆₈ tension" Physical Review D, Volume 108, Issue 2. https://doi.org/10.1103/physrevd.108.023520
Abstract
Models of dark sectors with a mass threshold can have important cosmological signatures. If, in the era prior to recombination, a relativistic species becomes nonrelativistic and is then depopulated in equilibrium, there can be measurable impacts on the cosmic microwave background as the entropy is transferred to lighter relativistic particles. In particular, if this “step” occurs near z∼20, 000, the model can naturally accommodate larger values of H₀. If this stepped radiation is additionally coupled to dark matter, there can be a meaningful impact on the matter power spectrum as dark matter can be coupled via a species that becomes nonrelativistic and depleted. This can naturally lead to suppressed power at scales inside the sound horizon before the step, while leaving conventional cold dark matter signatures for power outside the sound horizon. We study these effects and show such models can naturally provide lower values of 𝑆₈ than scenarios without a step. This suggests these models may provide an interesting framework to address the 𝑆₈ tension, both in concert with the H₀ tension and without.
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This article is distributed under the terms of the Creative Commons Attribution 4.0 International.