The simplest single-field inflation models predict a nearly Gaussian distribution of primordial density perturbations. However, the non-Gaussianity of the primordial density field serves as a powerful probe into the physics of the early universe, especially when considering more complex inflation models. The Cosmic Microwave Background (CMB) bispectrum has provided the tightest constraint on the local type non-Gaussianity parameter, f_NL, to the order of 1. Upcoming large-scale structure(LSS) surveys, such as DESI, Euclid, and SKA, are anticipated to offer better constraints in principle, due to their access to three-dimensional information.
In this talk, I will first introduce the basic concepts of primordial non-Gaussianity(PNG), its possible origin, and its parameterization. Then I will review the detection of PNG by CMB and LSS surveys, and finally discuss our recent work on forecasting f_NL constraints through HI intensity mapping surveys.
