Multiversality

TL;DR

The paper explores the concept of multiversality, discussing its philosophical background, recent scientific theories like inflationary axion cosmology, and their implications for understanding the universe's fundamental nature.

Contribution

It provides a comprehensive review of multiverse ideas, emphasizing the testable aspects of inflationary axion cosmology as a concrete example.

Findings

Inflationary axion cosmology predicts a mini-multiverse with testable consequences.

Multiverse theories challenge traditional physics by suggesting a vastly larger reality.

The paper highlights the importance of empirical approaches to multiverse hypotheses.

Abstract

Valid ideas that physical reality is vastly larger than human perception of it, and that the perceived part may not be representative of the whole, exist on many levels and have a long history. After a brief general inventory of those ideas and their implications, I consider the cosmological "multiverse" much discussed in recent scientific literature. I review its theoretical and (broadly) empirical motivations, and its disruptive implications for the traditional program of fundamental physics. I discuss the inflationary axion cosmology, which provides an example where firmly rooted, plausible ideas from microphysics lead to a well-characterized "mini-multiverse" scenario, with testable phenomenological consequences.