Constraining Single-Field Inflation with MegaMapper by Giovanni Cabass et al. on Tuesday 29 November

We forecast the constraints on single-field inflation from the bispectrum of

future high-redshift surveys such as MegaMapper. Considering non-local

primordial non-Gaussianity (NLPNG), we find that current methods will yield

constraints of order $\sigma(f_{\rm NL}^{\rm eq})\approx 23$, $\sigma(f_{\rm

NL}^{\rm orth})\approx 12$ in a joint power-spectrum and bispectrum analysis,

varying both nuisance parameters and cosmology, including a conservative range

of scales. Fixing cosmological parameters and quadratic bias parameter

relations, the limits tighten significantly to $\sigma(f_{\rm NL}^{\rm

eq})\approx 17$, $\sigma(f_{\rm NL}^{\rm orth})\approx 8$. These compare

favorably with the forecasted bounds from CMB-S4: $\sigma(f_{\rm NL}^{\rm

eq})\approx 21$, $\sigma(f_{\rm NL}^{\rm orth})\approx 9$, with a combined

constraint of $\sigma(f_{\rm NL}^{\rm eq})\approx 14$, $\sigma(f_{\rm NL}^{\rm

orth})\approx 7$; this weakens only slightly if one instead combines with data

from the Simons Observatory. We additionally perform a range of Fisher analyses

for the error, forecasting the dependence on nuisance parameter

marginalization, scale cuts, and survey strategy. Lack of knowledge of bias and

counterterm parameters is found to significantly limit the information content;

this could be ameliorated by tight simulation-based priors on the nuisance

parameters. The error-bars decrease significantly as the number of observed

galaxies and survey depth is increased: as expected, deep dense surveys are the

most constraining, though it will be difficult to reach $\sigma(f_{\rm

NL})\approx 1$ with current methods. The NLPNG constraints will tighten further

with improved theoretical models (incorporating higher-loop corrections), as

well as the inclusion of additional higher-order statistics.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14899v1