Anisotropy of the Cosmic Background Radiation implies the Violation of the Strong Energy Condition in Bianchi type I Universe

TL;DR

This paper demonstrates that in a Bianchi type I universe, the horizon problem cannot be resolved under the strong energy condition, highlighting the necessity of its violation during inflation.

Contribution

It shows the incompatibility of solving the horizon problem with the strong energy condition in anisotropic universes, emphasizing the role of inflation.

Findings

Horizon problem cannot be solved if strong energy condition holds

Violation of strong energy condition is necessary during inflation

Anisotropic universe models impose constraints on cosmological solutions

Abstract

We consider the horizon problem in a homogeneous but anisotropic universe (Bianchi type I). We show that the problem cannot be solved if (1) the matter obeys the strong energy condition with the positive energy density and (2) the Einstein equations hold. The strong energy condition is violated during cosmological inflation.