Probing the small-scale primordial power spectrum via relic neutrinos and acoustic reheating
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2026
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| _version_ | 1866911679178080256 |
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| author | Piccoli, Giovanni Vagnozzi, Sunny Silk, Joseph |
| author_facet | Piccoli, Giovanni Vagnozzi, Sunny Silk, Joseph |
| contents | We show that the dissipation of small-scale perturbations through diffusion damping after neutrino decoupling lowers the present-day neutrino temperature compared to the expected value of $1.96\,{\text{K}}$. This reduces the relic neutrino abundance by an amount controlled by the integral of the primordial curvature power spectrum $Δ_{\cal R}^2(k)$. We find that a relic neutrino detection by PTOLEMY can set limits $Δ_{\cal R}^2(k) \lesssim {\cal O}(0.1)$ on scales $k \lesssim 3 \times 10^5\,{\text{Mpc}^{-1}}$, complementary to limits from Big Bang Nucleosynthesis, spectral distortions, pulsar timing arrays, and future dark ages 21-cm observations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_11956 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing the small-scale primordial power spectrum via relic neutrinos and acoustic reheating Piccoli, Giovanni Vagnozzi, Sunny Silk, Joseph High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Theory We show that the dissipation of small-scale perturbations through diffusion damping after neutrino decoupling lowers the present-day neutrino temperature compared to the expected value of $1.96\,{\text{K}}$. This reduces the relic neutrino abundance by an amount controlled by the integral of the primordial curvature power spectrum $Δ_{\cal R}^2(k)$. We find that a relic neutrino detection by PTOLEMY can set limits $Δ_{\cal R}^2(k) \lesssim {\cal O}(0.1)$ on scales $k \lesssim 3 \times 10^5\,{\text{Mpc}^{-1}}$, complementary to limits from Big Bang Nucleosynthesis, spectral distortions, pulsar timing arrays, and future dark ages 21-cm observations. |
| title | Probing the small-scale primordial power spectrum via relic neutrinos and acoustic reheating |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2605.11956 |