Q-ball formation in the gravity-mediated SUSY breaking scenario

TL;DR

The paper demonstrates, via full nonlinear lattice simulations, that Q-balls form from Affleck-Dine condensates in gravity-mediated SUSY breaking, with the Q-ball size dictated by the most amplified linear mode and the charge scaling linearly with the initialAD charge. Almost all of the initial charge becomes confined within Q-balls, leaving only a small relic AD field, and the dynamics include moving Q-balls and potential one-dimensional collisions. The results connect Q-ball properties to MSSM parameters and cosmological constraints, notably deriving bounds on neutralino mass from the baryon-dark-matter relationship. Overall, the work extends the understanding of Q-ball formation and dynamics in gravity mediation, highlighting implications for baryogenesis and dark matter phenomenology.

Abstract

We study the formation of Q-balls which are made of flat directions that appear in the supersymmetric extension of the standard model in the context of gravity-mediated supersymmetry breaking. The full non-linear calculations for the dynamics of the complex scalar field are made. Since the scalar potential in this model is flatter than φ^2, we have found that fluctuations develop and go non-linear to form non-topological solitons, Q-balls. The size of a Q-ball is determined by the most amplified mode, which is completely determined by the model parameters. On the other hand, the charge of Q-balls depends linearly on the initial charge density of the Affleck-Dine (AD) field. Almost all the charges are absorbed into Q-balls, and only a tiny fraction of the charges is carried by a relic AD field. It may lead to some constraints on the baryogenesis and/or parameters in the particle theory. The peculiarity of gravity-mediation is the moving Q-balls. This results in collisions between Q-balls. It may increase the charge of Q-balls, and change its fate.

Figures (11)

• Figure 1: Configuration of Q-balls on three-dimensional lattice. More than 40 Q-balls are formed, and the largest one has the charge with $Q\simeq 5.16\times 10^{16}$
• Figure 2: Configuration of Q-balls on three-dimensional lattice. In each direction, the box size is half of that in Fig. \ref{['3D-large']}. More than 10 Q-balls are formed, and the largest one has the charge with $Q\simeq 1.74\times 10^{16}$
• Figure 3: Amplitude of the AD field after formation of Q-balls. This configuration is the slice at $z=6.3$. The amplitude of relic field outside the Q-balls is two or three orders smaller than that of the center of the Q-balls.
• Figure 4: Fraction of the charge outside the Q-balls.The solid and dotted lines denote the results from the simulations shown in Figs. \ref{['3D-large']} and \ref{['3D-small']}, respectively.
• Figure 5: Dependence of the energy of the Q-ball on its charge calculated on three-dimensional lattices. This confirms the analytical estimate: $E\simeq mQ$ (the dotted line).