Speaker
Description
In this talk, I will show that although ultralight dark matter (ULDM) is often modeled as a scalar field with Gaussian fluctuations, its density perturbations are intrinsically non-Gaussian. I will explain the origin of this non-Gaussianity and discuss the resulting bispectrum, highlighting its universal power-law behavior for white-noise density perturbations with a characteristic scale set by the ULDM momentum. I will then present existing constraints on the ULDM abundance from Planck measurements of primordial non-Gaussianity and forecast the sensitivity of future large-scale structure (LSS) surveys. Finally, I will apply these results to two scenarios: ULDM with a Gaussian phase-space distribution and axions produced by cosmic string decay. The results show that future measurements of LSS non-Gaussianity could probe ULDM abundances beyond the reach of existing dark matter isocurvature constraints.