Anthropic constraint on transient variations of fundamental constants

TL;DR

This paper uses the anthropic principle to place constraints on transient changes in fundamental constants, especially the fine-structure constant, over Earth's history, impacting habitability and dark matter models.

Contribution

It demonstrates that anthropic considerations can significantly constrain transient variations of fundamental constants and improve bounds on dark matter interactions.

Findings

Transient large variations of alpha would render Earth uninhabitable.

Extreme alpha variations truncate the periodic table and destabilize protons.

Anthropic constraints improve astrophysical bounds on dark matter couplings.

Abstract

The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants. Here we show that anthropic arguments can set powerful constraints on {\em transient} variations of the fine-structure constant $\alpha$ over the past 4 billion years since the appearance of lifeforms on Earth. We argue that the passage through Earth of a macroscopic dark matter clump with a value of $\alpha$ inside differing substantially from its nominal value would make Earth uninhabitable. We demonstrate that in the regime of extreme variation of $\alpha$, the periodic table of elements is truncated, water fails to serve as a universal solvent, and protons become unstable. Thereby, the anthropic principle constrains the likelihood of such encounters on a 4-billion-year timescale. This enables us to improve existing astrophysical bounds on certain dark matter model couplings by several orders of magnitude.