Cosmic microwave anisotropies in an inhomogeneous compact flat universe

TL;DR

This paper investigates how a finite, inhomogeneous compact flat universe model, specifically the half-turn space, can better explain observed large-scale cosmic microwave background anisotropies than the standard infinite universe model.

Contribution

It demonstrates that the half-turn space model provides a superior fit to large-scale CMB anisotropies compared to the conventional infinite universe model.

Findings

Half-turn space matches observed CMB anisotropies better than the concordance model.

The model's statistical properties depend on observer position within the fundamental cell.

Most observer positions yield a temperature correlation function slightly better than the 3-torus topology.

Abstract

The anisotropies of the cosmic microwave background (CMB) are computed for the half-turn space E_2 which represents a compact flat model of the Universe, i.e. one with finite volume. This model is inhomogeneous in the sense that the statistical properties of the CMB depend on the position of the observer within the fundamental cell. It is shown that the half-turn space describes the observed CMB anisotropies on large scales better than the concordance model with infinite volume. For most observer positions it matches the temperature correlation function even slightly better than the well studied 3-torus topology.