The Trispectrum as a Diagnostic of Primordial Orthogonal non-Gaussianities

Abstract

In single-field inflationary models with a low sound speed, the orthogonal shape of the primordial bispectrum arises due to partial cancellations between equilateral-type shapes. This fact allows for a speed of sound c_s as low as about 0.01, which is actually weakly preferred by WMAP data. For such values, the trispectrum, scaling like 1/c_s^4, is of order 10^8 and is therefore comparable to, and greater than, the 1 sigma observational bound t_NL^eq=(-3.11 +- 7.5)*10^6. Hence, the trispectrum is already constraining inflationary mechanisms candidates for generating an orthogonal bispectrum at the level hinted in WMAP data. If this signal persists in imminent Planck data, most of the parameter space of the simplest effective field theory of inflation will be under observational pressure, while a dedicated analysis will be needed for the substantial fraction of parameter space where we show that a qualitatively new, orthogonal, trispectrum naturally arises.

22 pages, 10 figures. References added. Appendix B about trispectrum estimators added. Matches version published in JCAP

References in corpus (8)

• The Effective Field Theory of Inflation
• Observational Signatures and Non-Gaussianities of General Single Field Inflation
• Primordial Non-Gaussianities from Inflation Models
• The shape of primordial non-Gaussianity and the CMB bispectrum
• The Inflationary Trispectrum for Models with Large Non-Gaussianities
• CMB Constraints on Primordial non-Gaussianity from the Bispectrum (f_{NL}) and Trispectrum (g_{NL} and τ_{NL}) and a New Consistency Test of Single-Field Inflation
• Primordial non-Gaussianity and the CMB bispectrum
• Nongaussianity from Particle Production During Inflation

Cited by in corpus (5)

• DBI Galileon in the Effective Field Theory of Inflation: Orthogonal non-Gaussianities and constraints from the Trispectrum
• On the Trispectrum of Galileon Inflation
• The Trispectrum in the Effective Theory of Inflation with Galilean symmetry
• Halo/Galaxy Bispectrum with Equilateral-type Primordial Trispectrum
• Loops in inflation with strongly non-geodesic motion