Scientists at the University of Michigan have described a new kind of universes that lack the weak nuclear force. Despite the fact that the existence of life is possible only for certain values of physical constants, the theoretical model predicts that weak interaction is not necessary for the emergence of living organisms. A preprint of the article has been published in the bioRxiv repository.
It is known that the fundamental physical constants describing the laws of nature and the properties of matter have arbitrary values that cannot be explained within the framework of modern physical theory. However, a number of physicists suggest that there are universes with different "settings" that may not be suitable for the existence of life. At the same time, a number of scientific works have demonstrated that if many constants are allowed to vary over a wide range, then potentially inhabited universes with a different value of constants may appear.
The Standard Model describes the electromagnetic, weak and strong interactions of all elementary particles. The weak nuclear force is responsible for the beta decays of atomic nuclei, when a neutron turns into a proton, while emitting an electron or positron. It determines the processes occurring in the bowels of not very massive stars, such as the Sun, and affects the probability of interaction of neutrinos with matter. If the level of weak nuclear interaction is too low, then the formation of long-lived stars is impossible in such a universe.
Helium can still be synthesized in the early stages of the universe, in the era of primordial nucleosynthesis. In more massive stars, helium atoms can fuse to form heavier elements, but the lack of interaction of neutrinos with matter makes it impossible for supernovae to form - the star simply shrinks, preventing the propagation of heavy atoms in space.
However, cosmologists have found that a universe where the weak interaction is completely absent, can still have life. During the era of primary nucleosynthesis, some of the protons and neutrons bypass the inclusion of atoms in heavy nuclei. In our universe, on the contrary, protons actively participated in the synthesis of elements up to lithium. Later, free protons and neutrons combine to form deuterium (heavy hydrogen). The latter becomes fuel for stars, whose evolution is due to strong interactions. They form carbon and other elements necessary for life.