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arXiv · 2504.07838

Large anisotropies in the gravitational wave background from baryogenesis

Yan-Heng Yu·Sai Wang
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Abstract

Affleck-Dine (AD) baryogenesis can produce the baryon asymmetry of the Universe through the $CP$-violating dynamics of AD field. The field generally fragments into Q-balls, whose rapid decay induces enhanced gravitational waves. In this Letter, we investigate the anisotropies in this gravitational wave background as a new essential observable for AD baryogenesis. The evolution of AD field causes non-Gaussian baryonic isocurvature perturbations, and the non-Gaussianity modulates the spatial distribution of Q-balls on large scales, resulting in large-scale anisotropies in the Q-ball-induced gravitational wave background. We present that the anisotropies can be significantly large with a reduced angular power spectrum $\sim 10^{-2}$, and can be detected by future experiments like LISA. Moreover, these anisotropies universally reveal the $CP$-violating dynamics of AD field, opening a novel road to explore the longstanding baryon asymmetry puzzle.

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Yan-Heng Yu, Sai Wang. 2025-04-10. Large anisotropies in the gravitational wave background from baryogenesis. https://arxiv.org/abs/2504.07838

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