Kaon superfluidity in the early Universe

Abstract

Previously, it was found that pion superfluidity could be realized in the quantum chromodynamics (QCD) epoch of the early Universe, when lepton flavor asymmetry |le+lμ| is large enough to generate a charge chemical potential |μQ| larger than vacuum pion mass. By following the same logic, kaon superfluidity might also be possible when |le+lμ| is so large that |μQ| becomes larger than vacuum kaon mass. Such a possibility is checked by adopting Ginzburg-Landau approximation within the three-flavor Polyakov–Nambu–Jona-Lasinio model. Consider the case with full chemical balance, though kaon superfluidity could be stable compared to the chiral phases with only σ condensations, it would get killed by the more favored homogeneous pion superfluidity. If we introduce mismatch between s and d quarks, kaon superfluidity would require so large s quark density that such a state is impossible in the early Universe. Published by the American Physical Society 2024