Mixed Axion/Axino Dark Matter in mSUGRA and Yukawa-unified SUSY

Abstract

Axion/axino dark matter (DM) is explored in the minimal supergravity (mSUGRA) and Yukawa-unified supersymmetric grand-unified theory (SUSY GUT) models with surprising results. For this type of scenario, relic DM abundance has three components: {\it i}.) cold axions, {\it ii.}) warm axinos from neutralino decay, and {\it iii.}) cold or warm thermally produced axinos. Reheat temperatures $T_R$ exceeding $10^6$ GeV are required in order to solve the gravitino/Big Bang Nucleosynthesis (BBN) problem while also allowing for baryogensis via non-thermal leptogenesis. In order to attain high enough reheat temperatures, we also need high values of the Peccei-Quinn (PQ) breaking scale $f_a$ on the order $10^{11}$-$10^{12}$ GeV.