Non-Gaussianity from Symmetry

TL;DR

This paper introduces the concept of an 'ungaussiton', a light scalar field near a symmetry point that can produce significant non-Gaussianity in density fluctuations, with a unique consistency relation between bispectrum and trispectrum.

Contribution

It proposes a new mechanism involving ungaussitons for generating large non-Gaussianity and derives a distinctive consistency relation among higher-order correlation functions.

Findings

Derivation of a specific consistency relation: tau_NL = 10^3 f_NL^(4/3)

Identification of ungaussiton as a source of large non-Gaussianity

Potential observational test for the mechanism via future data

Abstract

We point out that a light scalar field fluctuating around a symmetry-enhaced point can generate large non-Gaussianity in density fluctuations. We name such a particle as an "ungaussiton", a scalar field dominantly produced by the quantum fluctuations,generating sizable non-Gaussianity in the density fluctuations. We derive a consistency relation between the bispectrum and the trispectrum, tau_NL = 10^3 f_NL^(4/3), which can be extended to arbitrary high order correlation functions. If such a relation is confirmed by future observations, it will strongly support this mechanism.