Probing baryogenesis with gravitational waves

TL;DR

This work shows that Affleck-Dine baryogenesis can be realized with a non-supersymmetric, GeV-scale complex scalar, whose post-inflation dynamics generate a baryon asymmetry and a stochastic gravitational wave background. The AD condensate undergoes parametric resonance during its oscillations, producing GWs with a peak in the tens-to-hundreds of Hz range, making them accessible to upcoming GW detectors such as CE and ET. The analysis identifies a viable parameter space with $m_\Phi$ in ${\cal O}(0.1-10)$ GeV and initial field values near the Planck scale, while the GW peak frequency remains in LIGO-frequency bands; a low-frequency tail offers potential multi-band detection with DECIGO/BBO. The study also outlines UV-complete, testable ways to transfer the AD asymmetry to the SM (via leptogenesis or direct baryogenesis), highlighting a complementary interplay between GW observations and laboratory searches across energy and intensity frontiers. Overall, the work provides a concrete, testable link between early Universe baryogenesis and a stochastic gravitational-wave signal detectable in the near future.

Abstract

Affleck-Dine (AD) baryogenesis is compelling yet challenging to probe because of the high-energy physics involved. We demonstrate that this mechanism can be generically realized with low-energy new physics, without supersymmetry, while producing detectable gravitational waves (GWs) sourced by the parametric resonance of a light scalar field. In viable models, the scalar has a mass of $\mathcal{O}(0.1-10)$ GeV, yielding GWs with peak frequencies of $\mathcal{O}(10-100)$ Hz. This study further reveals a new complementarity between upcoming LIGO-frequency GW detectors and laboratory searches across frontiers of particle physics.

Figures (4)

• Figure 1: We show the GW spectrum originating from the AD model considered here for three benchmark masses of $\Phi$. The potential parameters $\lambda_\Phi\sim 10^{10}m_\Phi^2/M_{\rm {Pl}}^2$, $A=0$ are chosen to ensure efficient parametric resonance (see the main text for details). The fraction of initial scalar field energy density over the total energy density of the Universe is $\alpha=30\%$. The dashed lines at lower frequencies are extrapolated according to the causal superhorizon $k^3$ scaling.
• Figure S1: The maximum baryon-to-photon ratio $\left . {n_B / s}\right|_{\rm {max}} = {n_\Phi/s}$ (neglecting possible washout and the sphaleron factor) for three different masses of the scalar field, as in Fig. (1) of the main text, as a function of the temperature $T_d$ of the $\Phi$ decay. The solid and dashed lines correspond to $\epsilon_{\Phi} = 10^{-20}$ and $\epsilon_{\Phi} = 10^{-6}$ respectively. The maximum temperature (denoted as the dots) for each line corresponds to the case of instantaneous decay of the scalar at $t=t_{\ast}$. The horizontal dot-dashed line corresponds to the observed value of the baryon asymmetry.
• Figure S2: The spectra of the scalar field fluctuations along (left) and perpendicular (right) to the direction of the background trajectory in the case when the potential has a rotation symmetry with $A=0$, $\lambda_\Phi = 5\times 10^{-35}$ and $m_\Phi = 0.1$ GeV.
• Figure S3: The resulting GW spectra for different values of the asymmetry parameter $A$ (color-coded according to the legend) and initial angle $\theta\equiv \arctan(\phi_I/\phi_R)|_{\rm{init}} = \pi/6, \pi/4, \pi/3$ (solid, dashed and dotted respectively).