Numerical Relativity as a New Tool for Fundamental Cosmology

TL;DR

This paper introduces numerical relativity as a new computational approach in fundamental cosmology, demonstrating its ability to explore early universe scenarios and challenge existing theories about the universe's large-scale uniformity.

Contribution

It presents the application of numerical relativity to cosmology, revealing new non-linear smoothing mechanisms that impact understanding of the universe's initial conditions.

Findings

Numerical relativity shows robustness of slow contraction and inflation.

Discovery of a non-linear ultralocal smoothing mechanism.

Challenges conventional views on universe homogeneity.

Abstract

Advances in our understanding of the origin, evolution and structure of the universe have long been driven by cosmological perturbation theory, model building and effective field theory. In this review, we introduce numerical relativity as a powerful new complementary tool for fundamental cosmology. To illustrate its power, we discuss applications of numerical relativity to studying the robustness of slow contraction and inflation in homogenizing, isotropizing and flattening the universe beginning from generic unsmooth initial conditions. In particular, we describe how recent numerical relativity studies of slow contraction have revealed a novel, non-linear smoothing mechanism based on ultralocality that challenges the conventional view on what is required to explain the large-scale homogeneity and isotropy of the observable universe.