Cosmological CP odd axion field as the coherent Berry's phase of the Universe

摘要

We consider a dark matter (DM) model offering a very natural explanation ofthe observed relation, $\Omega_{\rm dark} \sim \Omega_{\rm visible}$. Thisgeneric consequence of the model is a result of the common origin of both typesof matter (DM and visible) which are formed during the same QCD transition. Themasses of both types of matter in this framework are proportional to one andthe same dimensional parameter of the system, $\Lambda_{\rm QCD}$. The focus ofthe present work is the detail study of the dynamics of the $\cal{CP}$-oddcoherent axion field $a(x)$ just before the QCD transition. We argue that thebaryon charge separation effect on the largest possible scales inevitablyoccurs as a result of merely existence of the coherent axion field in earlyUniverse. It leads to preferential formation of one species of nuggets on thescales of the visible Universe where the axion field $a(x)$ is coherent. Anatural outcome of this preferential evolution is that only one type of thevisible baryons remains in the system after the nuggets complete theirformation. This represents a specific mechanism on how the baryon chargeseparation mechanism (when the Universe is neutral, but visible part of matterconsists the baryons only) replaces the conventional "baryogenesis" scenarios.