Non-Gaussianity in Island Cosmology

TL;DR

This paper calculates the non-Gaussianity of primordial curvature perturbations in island cosmology, finding levels that could be tested by future observations, thus linking cosmological measurements to the landscape hypothesis.

Contribution

It provides a detailed second-order perturbation calculation of non-Gaussianity in island universe models, connecting theoretical predictions with observational prospects.

Findings

Non-Gaussianity level $f_{NL}$ between 30 and 60 for $n_s\simeq 0.96$

Results are testable by upcoming cosmological observations

Implications for understanding our position in the landscape of possible universes

Abstract

In this paper we fully calculate the non-Gaussianity of primordial curvature perturbation of island universe by using the second order perturbation equation. We find that for the spectral index $n_s\simeq 0.96$, which is favored by current observations, the non-Gaussianity level $f_{NL}$ seen in island will generally lie between 30 $\sim$ 60, which may be tested by the coming observations. In the landscape, the island universe is one of anthropically acceptable cosmological histories. Thus the results obtained in some sense means the coming observations, especially the measurement of non-Gaussianity, will be significant to make clear how our position in the landscape is populated.