21-cm Background Anisotropies Can Discern Primordial Non-Gaussianity

The non-Gaussianity of initial perturbations provides information on the mechanism that generated primordial density fluctuations. We find that 21-cm background anisotropies due to inhomogeneous neutral hydrogen distribution prior to reionization captures information on primordial non-Gaussianity better than a high-resolution cosmic microwave background anisotropy map. An all-sky 21-cm experiment over the frequency range from 14 to 40 MHz with angular information out to a multipole of ${10}^5$ can limit the primordial non-Gaussianity parameter $f_{\mathrm{NL}}\lesssim 0.01$.