A universe without weak interactions

Abstract

A universe without weak interactions is constructed that undergoes big-bang\nnucleosynthesis, matter domination, structure formation, and star formation.\nThe stars in this universe are able to burn for billions of years, synthesize\nelements up to iron, and undergo supernova explosions, dispersing heavy\nelements into the interstellar medium. These definitive claims are supported by\na detailed analysis where this hypothetical "Weakless Universe" is matched to\nour Universe by simultaneously adjusting Standard Model and cosmological\nparameters. For instance, chemistry and nuclear physics are essentially\nunchanged. The apparent habitability of the Weakless Universe suggests that the\nanthropic principle does not determine the scale of electroweak breaking, or\neven require that it be smaller than the Planck scale, so long as technically\nnatural parameters may be suitably adjusted. Whether the multi-parameter\nadjustment is realized or probable is dependent on the ultraviolet completion,\nsuch as the string landscape. Considering a similar analysis for the\ncosmological constant, however, we argue that no adjustments of other\nparameters are able to allow the cosmological constant to raise up even\nremotely close to the Planck scale while obtaining macroscopic structure. The\nfine-tuning problems associated with the electroweak breaking scale and the\ncosmological constant therefore appear to be qualitatively different from the\nperspective of obtaining a habitable universe.\n