The Level I Multiverse is not the same as the Level III Multiverse

TL;DR

This paper argues that the Level I and Level III Multiverses are fundamentally different, showing that our bubble universe's quantum state prevents the Level III multiverse's orthogonal states from existing within it.

Contribution

It demonstrates that the quantum state of our bubble universe precludes the equivalence of Level I and Level III Multiverses, clarifying their distinct natures.

Findings

Our bubble universe is in a single quantum eigenstate.

Regions receding faster than light are in the same eigenstate.

Quantum uncertainty arises from multiple isolated bubble universes.

Abstract

Anthony Aguirre and Max Tegmark have famously speculated that the Level I Multiverse is the same as the Level III Multiverse. By this, they mean that the parallel universes of the Level III Multiverse can be regarded as similar or identical copies of our own Hubble volume distributed throughout the whole of our (possibly infinite) bubble universe. However, we show that our bubble universe is in a single quantum eigenstate that extends to regions of space that are receding from each other at superluminal velocities because of general relativistic expansion. Such a bubble universe cannot accommodate Hubble volumes in the different orthogonal eigenstates required by the Level III Multiverse. Instead, quantum uncertainty arises from large numbers of alternative bubble universes in Hilbert space, isolated from each other. The conclusion of the paper is that the Level I Multiverse is not the same as the Level III Multiverse.