Lyman-alpha Forest Forward Modeling Delivers First 30% Upper Limit on Dark Acoustic Oscillations at k<50 h Mpc^{-1}
The study supplies the first quantitative DAO bound from small-scale structure, tightening early-universe physics parameter space beyond CMB reach. Complex covariance between DAO amplitude and nuisance parameters is handled via emulation rather than analytic marginalization. Future wide-field spectroscopic surveys can push the limit below 10% within five years if systematics remain controlled.
The analysis forward-models the three-dimensional flux power spectrum while marginalizing over IGM thermal history, reionization, and noise. A deep kernel learning emulator trained on 10,000+ hydro runs captures the imprint of linear DAO wiggles at wavenumbers 25 times smaller than CMB scales, breaking degeneracies that previously limited constraints from galaxy clustering alone. No statistically significant oscillatory feature is detected, yielding the reported 30% limit on the DAO fraction of dark matter. This directly excludes broad classes of dark-sector interaction models that predict velocity-dependent scattering or late kinetic decoupling at masses below a few keV.
DESI: DAO fraction upper limit falls below 15% at k=40 h Mpc^{-1} within 36 months of final data release.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2606.28482)
- [2]Supporting Source(https://arxiv.org/abs/2112.08382)