Abstract
We study a dark matter (DM) model offering a very natural explanation of two (naively unrelated) problems in cosmology: the observed relation $\Omega_{\rm DM}\sim\Omega_{\rm visible}$ and the observed asymmetry between matter and antimatter in the Universe, known as the "baryogenesis" problem. In this framework, both types of matter (dark and visible) have the same QCD origin, form at the same QCD epoch, and both proportional to one and the same dimensional parameter of the system, $\Lambda_{\rm QCD}$, which explains how these two, naively distinct, problems could be intimately related, and could be solved simultaneously within the same framework. More specifically, the DM in this model is composed by two different ingredients: the (well- studied) DM axions and (less-studied) the quark nuggets made of matter or antimatter. The focus of the present work is the quantitative analysis of the relation between these two distinct components contributing to the dark sector of the theory determined by $\Omega_{\rm DM}\equiv [\Omega_{\rm DM}(\rm nuggets)+ \Omega_{\rm DM}(\rm axion)]$. We argue that the nugget's DM component always traces the visible matter density, i.e. $\Omega_{\rm DM}(\rm nuggets)\sim\Omega_{\rm visible}$ and this feature is not sensitive to the parameters of the system such as the axion mass $m_a$ or the misalignment angle $\theta_0$. It should be contrasted with conventional axion production mechanism due to the misalignment when $\Omega_{\rm DM}(\rm axion)$ is highly sensitive to the axion mass $m_a$ and the initial misalignment angle $\theta_0$. We also discuss the constraints on this model related to the inflationary scale $H_I$, non-observation of the isocurvature perturbations, $r_T < 0.12$, and also, varies axions search experiments.
Highlights
AND MOTIVATIONThe idea that dark matter may take the form of composite objects of standard model quarks in a novel phase goes back to quark nuggets [1], strangelets [2], nuclearities [3], see review [4] with a large number of references on the original results
Our original comment here is that the axion contribution represented by Ωa in Eq (32) to the dark matter density ΩDM could be numerically quite small in the AXION QUARK NUGGET (AQN) model as the nuggets in most cases play the dominant role by saturating the dark matter density
It should be contrasted with our AQN model where the axions themselves with the same fa may contribute very little to ΩDM as the dominant contribution may come from the nuggets, which always satisfy the relation ΩDM ∼ Ωvisible according to (1) irrespective of fa or the initial misalignment angle θa;i
Summary
The idea that dark matter may take the form of composite objects of standard model quarks in a novel phase goes back to quark nuggets [1], strangelets [2], nuclearities [3], see review [4] with a large number of references on the original results. As an alternative to this scenario we advocate a model in which the baryogenesis is a charge separation process in which the global baryon number of the Universe remains zero In this model the unobserved antibaryons come to comprise the dark matter in the form of dense nuggets of quarks and antiquarks in the CS phase. This disparity between nuggets and antinuggets unambiguously implies that the total number of antibaryons will be less than the number of baryons in early Universe plasma This is precisely the reason why the resulting visible and dark matter densities must be the same order of magnitude (1) in this framework as they are both proportional to the same fundamental ΛQCD scale, and they both are originated at the same QCD epoch. In the analysis which follows we treat the window (3) as the solid constraint on the allowed magnitude of the nuggets’ baryon charge
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
