Umeh, ObinnaMaartens, RoySantos, Mario G.2015-10-272015-10-272015http://hdl.handle.net/10566/1911Intensity mapping of the neutral hydrogen brightness temperature promises to provide a three-dimensional view of the universe on very large scales. Nonlinear effects are typically thought to alter only the small-scale power, but we show how they may bias the extraction of cosmological information contained in the power spectrum on ultra-large scales. For linear perturbations to remain valid on large scales, we need to renormalize perturbations at higher order. In the case of intensity mapping, the second-order contribution to clustering from weak lensing dominates the nonlinear contribution at high redshift. Renormalization modifies the mean brightness temperature and therefore the evolution bias. It also introduces a term that mimics white noise. These effects may influence forecasting analysis on ultra-large scales.enThis is the author version of an article that has been archived at http://arxiv.org/abs/1509.03786. A second version of this article has also been archived at http://arXiv:1509.03786v2.Nongalactic AstrophysicsCosmologyNeutral hydrogen (HI)non-GaussianityForecasting analysisArticle