Is brane cosmology predictable?

TL;DR

This paper examines the predictability of brane cosmology within 5D gravity frameworks, highlighting the ambiguity in universe creation due to boundary condition choices and proposing the need for a fundamental principle to ensure unique 4D geometry.

Contribution

It demonstrates the ambiguity in brane universe creation caused by arbitrary boundary conditions and suggests a fundamental principle is needed for unique 4D geometry determination.

Findings

Universe creation is ambiguous due to arbitrary boundary functions.

A fundamental principle may be required to fix the 4D geometry.

Boundary conditions influence the predictability of brane cosmology.

Abstract

The creation of the inflationary brane universe in 5d bulk Einstein and Einstein-Gauss-Bonnet gravity is considered. We demonstrate that emerging universe is ambigious due to arbitrary function dependence of the junction conditions (or freedom in the choice of boundary terms). We argue that some fundamental physical principle (which may be related with AdS/CFT correspondence) is necessary in order to fix the 4d geometry in unique way.