Uniform gradient expansions

TL;DR

This paper discusses a uniform gradient expansion approach to analyze the evolution of spatial inhomogeneities during the transition to inflation, highlighting limitations of conventional initial condition arguments for homogeneous inflation onset.

Contribution

It introduces a uniform gradient expansion method applicable during the protoinflationary boundary, providing new insights into the evolution of inhomogeneities and initial conditions for inflation.

Findings

Gradient expansion describes curvature suppression during quasi-de Sitter phase

Conventional initial conditions are necessary but not sufficient for homogeneous inflation

Uniform expansion offers a new perspective on protoinflationary boundary dynamics

Abstract

Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.