How does the Hubble Sphere limit our view of the Universe?

TL;DR

This paper clarifies that the Hubble Sphere is not a universal limit to our observable universe, showing that its role varies across different cosmological models, especially those with phantom energy.

Contribution

It demonstrates through cosmological models that the Hubble Sphere does not serve as a fundamental horizon, challenging recent claims about its limiting role.

Findings

In standard cosmologies, light can cross the Hubble Sphere multiple times.

In phantom energy models, the proper distance to the Hubble Sphere decreases over time.

The Hubble Sphere is not a universal horizon, contrary to recent claims.

Abstract

It has recently been claimed that the Hubble Sphere represents a previously unknown limit to our view of the universe, with light we detect today coming from a proper distance less than this "Cosmic Horizon" at the present time. By considering the paths of light rays in several cosmologies, we show that this claim is not generally true. In particular, in cosmologies dominated by phantom energy (with an equation of state of \omega < -1) the proper distance to the Hubble Sphere decreases, and light rays can cross it more than once in both directions; such behaviour further diminishes the claim that the Hubble Sphere is a fundamental, but unrecognised, horizon in the universe.