Constraints on Single-Field Inflation from the BOSS Galaxy Survey

TL;DR

This paper presents the first constraints on non-local primordial non-Gaussianity from galaxy survey data, providing new limits on inflationary models and inflaton sound speed.

Contribution

It offers the first independent constraints on non-local primordial non-Gaussianity using galaxy data, including nonlinear corrections and a comprehensive parameter analysis.

Findings

Constraints on equilateral and orthogonal non-Gaussianity parameters.

Lower bound on inflaton sound speed, c_s ≥ 0.013 at 95% CL.

Tighter constraints achieved with fixed bias and cosmology.

Abstract

Non-local primordial non-Gaussianity (NLPNG) is a smoking gun of interactions in single-field inflationary models, and can be written as a combination of the equilateral and orthogonal templates. We present the first constraints on these from the redshift-space galaxy power spectra and bispectra of the Baryon Oscillation Spectroscopic Survey (BOSS) data. These are the first such measurements independent of the cosmic microwave background fluctuations. We perform a consistent analysis that includes all necessary nonlinear corrections generated by NLPNG, and vary all relevant cosmological and nuisance parameters in a global fit to the data. Our conservative analysis yields joint limits on the amplitudes of the equilateral and orthogonal shapes, $f_{\rm NL}^{\rm equil}=940\pm 600$, $f_{\rm NL}^{\rm ortho}= -170\pm 170$ (both at 68\% CL). These can be used to derive constraints on coefficients of the effective single-field inflationary Lagrangian; in particular, we find that the sound speed of inflaton fluctuations has the bound $c_s\geq 0.013$ at 95\% CL. Fixing the quadratic galaxy bias and cosmological parameters, the constraints can be tightened to $f_{\rm NL}^{\rm equil}=260\pm 300$, $f_{\rm NL}^{\rm ortho}= -23\pm 120$ (68\% CL).