Speaker
Description
We investigate the cosmological viability of quadratic scalar field dark matter (SFDM), also known as fuzzy, wave, or ultralight dark matter, where the dark matter sector is modeled as a single ultra-light scalar field with potential
[
V(\phi)=\frac{1}{2}m_\phi^2\phi^2 .
]
The scalar-field background evolution and linear perturbations are implemented in a modified version of the Boltzmann code CLASS, allowing predictions for the CMB temperature anisotropy spectrum and the linear matter power spectrum. We constrain the model using Planck 2018 CMB data, DESI DR2 BAO measurements, Pantheon+ supernovae, and the three-dimensional Lyman-(\alpha) forest matter power spectrum.
Our results show that the standard cosmological parameters remain close to their (\Lambda)CDM values, indicating no significant departure from the concordance cosmological model. The baseline dataset combination gives a broad and nearly unconstrained posterior for the scalar-field mass. However, adding Lyman-(\alpha) forest information introduces strong small-scale sensitivity and yields a one-sided 95% confidence lower bound of
[
\log_{10}(m_\phi/\mathrm{eV})>-22.15 .
]
These results suggest that quadratic SFDM remains compatible with current cosmological observations, while future small-scale structure probes will be essential for improving constraints on the ultra-light dark matter mass.