Warm Dark Matter meets Cold Dark Matter Isocurvature
Fuente:
arXiv
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Preprint |
| Published: |
2025
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866909723984396288 |
|---|---|
| author | Tadepalli, Sai Chaitanya Takahashi, Tomo |
| author_facet | Tadepalli, Sai Chaitanya Takahashi, Tomo |
| contents | Isocurvature fluctuations can be generated in various scenarios in the early Universe. In particular, some specific models predict those with a blue-tilted spectrum, which is consistent with the constraints from cosmic microwave background such as Planck, although isocurvature fluctuations with an almost scale-invariant spectrum are severely constrained. We argue that cold dark matter (CDM) isocurvature fluctuations with blue-tilted spectrum are not only consistent with current cosmological data, but also can loosen the bound on the masses of warm dark matter (WDM), which suppresses small-scale power. In pure thermal WDM models with the adiabatic initial condition, a combination of the data from Lyman-$α$, gravitational lensing, and Milky Way satellites gives a lower bound on the WDM mass as $6~{\rm keV}$ at $95\%$ C.L. while mixed WDM+CDM models loosen these bounds to $m_{\rm WDM}\sim1$ keV for a warm-fraction $f_{\rm WDM}\lesssim0.14$ and $m_{\rm WDM}\sim600$ eV for $f_{\rm WDM}\lesssim0.08$. On the other hand, as we demonstrate, WDM scenarios with a blue-tilted CDM isocurvature power spectrum, even with only $1\%$ CDM contribution ($f_{\rm WDM}\sim0.99$), can allow WDM masses as low as $600$ eV. We further assess the implications of this ``warm + cold-isocurvature'' extension for the small-scale structure by performing $N$-body simulations, particularly focusing on nonlinear matter power spectrum and halo mass function. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_03805 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Warm Dark Matter meets Cold Dark Matter Isocurvature Tadepalli, Sai Chaitanya Takahashi, Tomo Cosmology and Nongalactic Astrophysics Isocurvature fluctuations can be generated in various scenarios in the early Universe. In particular, some specific models predict those with a blue-tilted spectrum, which is consistent with the constraints from cosmic microwave background such as Planck, although isocurvature fluctuations with an almost scale-invariant spectrum are severely constrained. We argue that cold dark matter (CDM) isocurvature fluctuations with blue-tilted spectrum are not only consistent with current cosmological data, but also can loosen the bound on the masses of warm dark matter (WDM), which suppresses small-scale power. In pure thermal WDM models with the adiabatic initial condition, a combination of the data from Lyman-$α$, gravitational lensing, and Milky Way satellites gives a lower bound on the WDM mass as $6~{\rm keV}$ at $95\%$ C.L. while mixed WDM+CDM models loosen these bounds to $m_{\rm WDM}\sim1$ keV for a warm-fraction $f_{\rm WDM}\lesssim0.14$ and $m_{\rm WDM}\sim600$ eV for $f_{\rm WDM}\lesssim0.08$. On the other hand, as we demonstrate, WDM scenarios with a blue-tilted CDM isocurvature power spectrum, even with only $1\%$ CDM contribution ($f_{\rm WDM}\sim0.99$), can allow WDM masses as low as $600$ eV. We further assess the implications of this ``warm + cold-isocurvature'' extension for the small-scale structure by performing $N$-body simulations, particularly focusing on nonlinear matter power spectrum and halo mass function. |
| title | Warm Dark Matter meets Cold Dark Matter Isocurvature |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2508.03805 |