The Effective Field Theory of nonsingular cosmology

TL;DR

This paper uses the Effective Field Theory framework to analyze nonsingular cosmologies, addressing instabilities and proposing models that align with observations, overcoming previous theoretical limitations.

Contribution

It clarifies the origin of the no-go theorem in cubic Galileon models and introduces EFT-based methods to construct stable, observationally consistent nonsingular cosmological models.

Findings

Gradient instability can be eliminated using spatial derivative operators in EFT

A realistic nonsingular cosmological model is constructed within the EFT framework

Perturbation spectrum of the model is consistent with observational data

Abstract

In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory(EFT) of cosmological perturbations. Due to the recently proved no-go theorem, any nonsingular cosmological models based on the cubic Galileon suffer from pathologies. We show how the EFT could help us clarify the origin of the no-go theorem, and offer us solutions to break the no-go. Particularly, we point out that the gradient instability can be removed by using some spatial derivative operators in EFT. Based on the EFT description, we obtain a realistic healthy nonsingular cosmological model, and show the perturbation spectrum can be consistent with the observations.