Dark Matter and Baryon Asymmetry from Monopole-Axion Interactions

TL;DR

The paper tackles the axion overproduction problem in axiogenesis by introducing a dark monopole sector that dissipates the axion's kinetic energy through level-crossing dynamics, allowing the QCD axion to generate the baryon asymmetry without overproducing dark matter. The mechanism relies on a dark SU(2) sector broken to U(1) that yields monopoles which become dyons under the axion's Witten effect, with energy dissipated via dyon-level transitions and gradient fluctuations; the baryon asymmetry is produced through axiogenesis and the residual rotation becomes axion DM. The model yields a multi-component dark matter scenario consisting of axions, dark monopoles, and dark fermions, with viable parameter space favoring $f_a \lesssim 10^9$ GeV and characteristic self-interacting dark-matter phenomenology. This framework provides concrete predictions for axion searches and dark-sector signals, linking fundamental symmetry breaking, monopole physics, and cosmological relic abundances in a testable way.

Abstract

We introduce a novel mechanism where the kinetic energy of a rotating axion can be dissipated by the interactions with dark magnetic monopoles. This mechanism leads to a framework where the QCD axion and dark monopoles account for the dark matter density, and the observed baryon asymmetry is generated through the rotating QCD axion via axiogenesis. The monopoles acquire masses from a nonzero axion field, and they can transition between different quantized dyonic levels in the presence of a rotating axion field. The axion kinetic energy is dissipated by the transition, and thus the axion abundance is depleted to the observed dark matter abundance. We predict that the axion decay constant should be below $10^9$ GeV to explain the observed dark matter and baryon densities.

Figures (2)

• Figure 1: Cartoon for the axion kinetic energy dissipation process with $\theta$ the axion misalignment angle and $m_D$ the dyon mass. The dissipation is achieved through the climbing of the axion field over many cycles, which is only enabled with the level crossing effect. During the rotation of the axion field, the axion kinetic energy is converted to potential energy. During the level crossing, the axion kinetic energy is conserved, but the potential energy is converted to a pair of dark fermions that the dyon decays into.
• Figure 2: Parameter space for successful baryogenesis and dark matter with fixed $\alpha_D = 0.2$, $c_B = 0.3$, and $f_M = 0.5$. Pink: PR becomes effective before $T_{\rm di}$ so that the coherent zero mode is converted into fluctuations and cannot be dissipated. Green: with monopole accounting for $f_M=50\%$ of dark matter, dark matter is overproduced by the corresponding particle labeled along the boundary. We show contours of $m_W$ necessary to help account for 100% dark matter. Orange: axion rotation is washed out by the $SU(2)_D$ sphaleron process before EWPT, for $m_S = 10~\rm MeV$, so that axiogenesis is not achieved. Blue: excluded by astrophysical bounds assuming the KSVZ axion. Note that the astrophysical bound may be relaxed DiLuzio:2017ogqBjorkeroth:2019jtxBadziak:2023fsc.