Ultraviolet Freeze-in and Non-Standard Cosmologies

摘要: A notable feature of UV freeze-in is that the relic density strongly dependent on highest temperatures thermal bath, and a common assumption relevant 'highest temperature' should be reheating temperature after inflation $T_\text{RH}$. However, bath can significantly higher in certain scenarios, reaching value denoted T max , fact which only apparent away from instantaneous decay approximation. Interestingly, it has been shown if operators are sufficiently high mass dimension then dark matter abundance enhanced by 'boost factor' depending ($T_\text{max}/T_\text{RH}$) relative to naive estimates assuming reheating. We highlight here non-standard cosmological histories critical operator above at approximation breaks down, exponent boost factor, depend equation state $\omega$ prior four examples receives significant enhancement context gravitino matter, moduli portal, Higgs spin-2 portal (as might arise bimetric gravity models). comment transition kination domination radiation as motivated example cosmologies.