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We investigate a class of universes in which the weak interaction is not inoperation. We consider how astrophysical processes are altered in the absenceof weak forces, including Big Bang Nucleosynthesis (BBN), galaxy formation,molecular cloud assembly, star formation, and stellar evolution. Without weakinteractions, neutrons no longer decay, and the universe emerges from its earlyepochs with a mixture of protons, neutrons, deuterium, and helium. Thebaryon-to-photon ratio must be smaller than the canonical value in our universeto allow free nucleons to survive the BBN epoch without being incorporated intoheavier nuclei. At later times, the free neutrons readily combine with protonsto make deuterium in sufficiently dense parts of the interstellar medium, andprovide a power source before they are incorporated into stars. Almost all ofthe neutrons are incorporated into deuterium nuclei before stars are formed. Asa 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 cansynthesize the heavier elements necessary for life. Although somewhat differentfrom our own, such universes remain potentially habitable.

Universes without the Weak Force: Astrophysical Processes with Stable Neutrons