Cosmological strangeness abundance

We investigate the strange particle composition of the expanding early Universe in the hadron epoch T_h≈150≥T≥10 MeV. We study strangeness yield in thermal and chemical equilibrium constrained by prescribed conserved entropy per baryon in a charge neutral and strangeness neutral 〈s−s¯〉 Universe. Turning to kinetic processes in a Hubble expanding Universe, we determine the conditions at which at decreasing temperature T individual strangeness producing reactions fall out of detailed balance between decay and back-reaction strangeness production rates: This is done by comparing the relevant reaction rates to the Hubble expansion rate. We allow for weak, electromagnetic, and strong interaction processes. The weak interaction μ^±+ν_μ→K^± freezeout is at T_f^K±=33.8 MeV; the electromagnetic process l⁻+l⁺→ϕ freezeout is at T_f^ϕ=23∼25 MeV; and the hadronic reaction π+π→K freezeout is at T_f^K=19.8 MeV.