Decoherence and Ontology, or: How I Learned To Stop Worrying And Love FAPP

TL;DR

The paper argues that the universe's structure according to unitary quantum theory naturally forms a many-worlds framework through decoherence, viewing worlds as emergent patterns rather than fundamental entities, aligning with scientific ontologies.

Contribution

It demonstrates that many-worlds can be understood as emergent structures within standard quantum theory without modifying its formalism.

Findings

Decoherence leads to emergent branching structures in quantum universe.

Many-worlds are patterns, not fundamental entities, consistent with scientific ontology.

Unitary quantum theory inherently contains multiple worlds as emergent phenomena.

Abstract

I make the case that the Universe according to unitary (no-collapse) quantum theory has a branching structure, and so can literally be regarded as a "many-worlds" theory. These worlds are not part of the fundamental ontology of quantum theory - instead, they are to be understood as structures, or patterns, emergent from the underlying theory, through the dynamical process of decoherence. That they are structures in this sense does not mean that they are in any way unreal: indeed, pretty much all higher-level ontology in science, from tables to phonons to tigers, is likewise emergent. Unitary quantum theory is therefore a "many-worlds" theory without any modification of the mathematical structure of the theory: the Everett interpretation does not consist in adding worlds to the formalism, but in realising that they are there already. Our grounds for accepting the reality of those worlds is no more, but no less, than our grounds for accepting any other not-directly observable consequence of an empirically very successful theory.