Constraints on $\tau_\mathrm{NL}$ from Planck temperature and polarization

TL;DR

This paper uses Planck temperature and polarization data to set the most stringent constraints yet on the primordial trispectrum amplitude, specifically on the parameter NL, by analyzing spatial modulations of small-scale power.

Contribution

It introduces a systematic method to constrain NL using quadratic estimators and likelihood analysis on Planck data, improving previous limits.

Findings

NL < 1700 at 95% confidence level

Demonstrates effectiveness of quadratic estimator techniques

Provides the most stringent constraints to date

Abstract

We update constraints on the amplitude of the primordial trispectrum, using the final Planck mission temperature and polarization data. In the squeezed limit, a cosmological local trispectrum would be observed as a spatial modulation of small-scale power on the CMB sky. We reconstruct this signal as a source of statistical anisotropy via quadratic estimator techniques. We systematically demonstrate how the estimated power spectrum of a reconstructed modulation field can be translated into a constraint on $\tau_\mathrm{NL}$ via likelihood methods, demonstrating the procedures effectiveness by inferring known $\tau_\mathrm{NL}$ signal(s) from simulations. Our baseline results constrain $\tau_\mathrm{NL} < 1700$ at the 95\% confidence level, providing the most stringent constraints to date.