Halo/Galaxy Bispectrum with Equilateral-type Primordial Trispectrum

TL;DR

This paper studies how equilateral-type primordial trispectra influence the halo/galaxy bispectrum, showing potential for future observations to constrain certain non-Gaussianity parameters independently of CMB data.

Contribution

It introduces a method to analyze the impact of specific primordial trispectra on the halo/galaxy bispectrum using integrated Perturbation Theory, highlighting the observational prospects.

Findings

Primordial trispectrum with $g_{ m NL} ^{ dots}$ mimics gravity-induced bispectrum.

Certain trispectra produce distinct scale-dependence on large scales.

Future galaxy surveys could constrain non-linearity parameters comparable to CMB constraints.

Abstract

We investigate the effect of equilateral-type primordial trispectrum on the halo/galaxy bispectrum. We consider three types of equilateral primordial trispectra which are generated by quartic operators naturally appeared in the effective field theory of inflation and can be characterized by three non-linearity parameters, $g_{\rm NL} ^{\dot{\sigma}^4}$, $g_{\rm NL} ^{\dot{\sigma}^2 (\partial \sigma)^2}$, and $g_{\rm NL} ^{(\partial \sigma)^4}$. Recently, constraints on these parameters have been investigated from CMB observations by using WMAP9 data. In order to consider the halo/galaxy bispectrum with the equilateral-type primordial trispectra, we adopt the integrated Perturbation Theory (iPT) in which the effects of primordial non-Gaussianity are wholly encapsulated in the linear primordial polyspectrum for the evaluation of the biased polyspectrum. We show the shapes of the halo/galaxy bispectrum with the equilateral-type primordial trispectra, and find that the primordial trispectrum characterized by $g_{\rm NL} ^{\dot{\sigma}^4}$ provides the same scale-dependence as the gravity-induced halo/galaxy bispectrum. Hence, it would be difficult to obtain the constraint on $g_{\rm NL} ^{\dot{\sigma}^4}$ from the observations of the halo/galaxy bispectrum. On the other hand, the primordial trispectra characterized by $g_{\rm NL} ^{\dot{\sigma}^2 (\partial \sigma)^2}$ and $g_{\rm NL} ^{(\partial \sigma)^4}$ provide the common scale-dependence which is different from that of the gravity-induced halo/galaxy bispectrum on large scales. Hence future observations of halo/galaxy bispectrum would give constraints on the non-linearity parameters, $g_{\rm NL} ^{\dot{\sigma}^2 (\partial \sigma)^2}$ and $g_{\rm NL} ^{(\partial \sigma)^4}$ independently from CMB observations and it is expected that these constraints can be comparable to ones obtained by CMB.