Universes without the Weak Force: Astrophysical Processes with Stable Neutrons

TL;DR

This paper explores universes lacking weak interactions, examining how astrophysical processes like nucleosynthesis, star formation, and stellar evolution are altered, and finds such universes could still be habitable with different elemental pathways.

Contribution

It introduces a detailed analysis of astrophysical processes in universes without weak forces, highlighting the potential for habitability despite fundamental differences.

Findings

Neutrons do not decay and remain stable.

Deuterium formation occurs readily in the interstellar medium.

Stars can synthesize heavy elements through strong interactions.

Abstract

We investigate a class of universes in which the weak interaction is not in operation. We consider how astrophysical processes are altered in the absence of weak forces, including Big Bang Nucleosynthesis (BBN), galaxy formation, molecular cloud assembly, star formation, and stellar evolution. Without weak interactions, neutrons no longer decay, and the universe emerges from its early epochs with a mixture of protons, neutrons, deuterium, and helium. The baryon-to-photon ratio must be smaller than the canonical value in our universe to allow free nucleons to survive the BBN epoch without being incorporated into heavier nuclei. At later times, the free neutrons readily combine with protons to make deuterium in sufficiently dense parts of the interstellar medium, and provide a power source before they are incorporated into stars. Almost all of the neutrons are incorporated into deuterium nuclei before stars are formed. As a result, stellar evolution proceeds primarily through strong interactions, with deuterium first burning into helium, and then helium fusing into carbon. Low-mass deuterium-burning stars can be long-lived, and higher mass stars can synthesize the heavier elements necessary for life. Although somewhat different from our own, such universes remain potentially habitable.