Constraining single-field inflation with MegaMapper

We forecast the constraints on single-field inflation from bispectrum of future high-redshift surveys such as MegaMapper. Considering non-local primordial non-Gaussianity (NLPNG), we find that current methods will yield order σ(fNLeq)≈23, σ(fNLorth)≈12 in a joint power-spectrum and analysis, varying both nuisance parameters cosmology, including conservative range scales. Fixing cosmological quadratic bias parameter relations, limits tighten significantly to σ(fNLeq)≈17, σ(fNLorth)≈8. These compare favorably with forecasted bounds CMB-S4: σ(fNLeq)≈21, σ(fNLorth)≈9, combined constraint σ(fNLeq)≈14, σ(fNLorth)≈7; this weakens only slightly if one instead combines data Simons Observatory. additionally perform Fisher analyses for error, forecasting dependence marginalization, scale cuts, survey strategy. Lack knowledge counterterm is found limit information content; could be ameliorated by tight simulation-based priors parameters. The error-bars decrease number observed galaxies depth increased: expected, deep dense are most constraining, though it difficult reach σ(fNL)≈1 methods. NLPNG further improved theoretical models (incorporating higher-loop corrections understanding parameters), well inclusion additional higher-order statistics.