Sphaleron bound in some nonstandard cosmology scenarios

Abstract: In the first scenario, we revise the upper bound of the cutoff scale of the dimension-six potential Higgs operator required for a successful electroweak baryogenesis in the case of a modified expansion history caused by the existence of a non-interacting scalar field at the time phase transition happens. The upper bound 860 GeV of the cutoff scale in the conventional case can be improved to 1 TeV in the modified expansion case under certain conditions. In the second scenario, we consider the Randall-Sundrum type II model. We show that the lower bound of the five-dimensional Planck scale in this model, which is determined from the validity of Newtonian gravitational potential at small distance, turns out to be crucial in eliminating this model as a viable candidate to satisfy the sphaleron bound; however, again modifying the expansion history by including a non-interacting scalar field at the electroweak scale can then make this model satisfy the sphaleron bound with a certain parameter space.