A universe without weak interactions

A universe without weak interactions is constructed that undergoes big-bangnucleosynthesis, matter domination, structure formation, and star formation.The stars in this universe are able to burn for billions of years, synthesizeelements up to iron, and undergo supernova explosions, dispersing heavyelements into the interstellar medium. These definitive claims are supported bya detailed analysis where this hypothetical "Weakless Universe" is matched toour Universe by simultaneously adjusting Standard Model and cosmologicalparameters. For instance, chemistry and nuclear physics are essentiallyunchanged. The apparent habitability of the Weakless Universe suggests that theanthropic principle does not determine the scale of electroweak breaking, oreven require that it be smaller than the Planck scale, so long as technicallynatural parameters may be suitably adjusted. Whether the multi-parameteradjustment is realized or probable is dependent on the ultraviolet completion,such as the string landscape. Considering a similar analysis for thecosmological constant, however, we argue that no adjustments of otherparameters are able to allow the cosmological constant to raise up evenremotely close to the Planck scale while obtaining macroscopic structure. Thefine-tuning problems associated with the electroweak breaking scale and thecosmological constant therefore appear to be qualitatively different from theperspective of obtaining a habitable universe.Comment: 27 pages; 4 figure