Spontaneous Cogensis by QCD axion in Type I Seesaw

TL;DR

This work addresses how the baryon asymmetry and the dark matter abundance can arise simultaneously from axion dynamics in a DFSZ-type model linked to a Type-I seesaw. The authors develop a kinetic misalignment framework in which a Hubble-induced PQ-breaking mass and higher-dimensional PQ-violating operators generate an axion velocity $\dot{\theta}$, which seeds spontaneous leptogenesis and then contributes to dark matter via the axion abundance $n_a \sim \dot{\theta} v_a^2$. They derive the baryon yield $Y_B = \kappa(K) |c_B| (\dot{\theta} T^2 /(6s))|_{T=m_N}$, constrain the right-handed neutrino mass to $m_N \sim \mathcal{O}(10-100)\left(\frac{f_a}{10^9\,\text{GeV}}\right)^{1/2}$ TeV, and show viability across $f_a \in [2.5\times 10^8,10^{12}]$ GeV with axion isocurvature limits. The analysis demonstrates that kinetic axion misalignment is a robust, inflation-microphysics-independent mechanism for axion cogenesis within a PQ–seesaw framework, and it can be extended to KSVZ and other seesaw implementations, linking the strong CP problem to neutrino masses and dark matter in a unified scenario.

Abstract

We propose a generic axion--driven cogenesis scenario in which both the baryon asymmetry and dark matter abundance originate from the kinetic misalignment. The framework unifies the Peccei--Quinn (PQ) mechanism with a Type--I seesaw sector, where Hubble--induced masses and higher-dimensional PQ--violating operators drive early--time axion rotation. Working within the DFSZ axion model augmented by heavy neutrinos, we identify the parametric window of right-handed neutrino masses, determined by its decay rate, and the range of Hubble scales compatible with successful cogenesis, while maintaining the axion solution to the strong CP problem and satisfying current limits on axion isocurvature perturbations. Our results establish kinetic axion misalignment as a robust and predictive mechanism for axion cogenesis, independent of the inflationary microphysics.

Figures (3)

• Figure 1: The required right-handed neutrino mass $m_N$ as a function of the decay parameter $K$ for two distinct initial conditions: $Y_N(0)=0$ (vanishing initial abundance) and $Y_N(0)=Y_N^{\rm eq}$ (thermal initial abundance). For this analysis, we have adopted the benchmark values $N_{DW}=6$, $|c_B|=2.3$, and $f_a=10^9$ GeV.
• Figure 2: Evolution of the friction, potential term and $\dot\theta$ in terms of the time $t$ with arbitrary initial conditions and normalization setting $t_c=0.01$.
• Figure 3: Cogenesis contours are shown for various choices of $(n,f_a)$. For each value of $f_a$, the dimensionality $n$ of the PQV operator is selected to preserve axion quality, while the upper bound on $H_c$ is determined by constraints from axion isocurvature perturbations. The figure corresponds to $T_R=10^9$ GeV, although the results are not significantly sensitive to this choice.