Zhen-Meng Xu | Searcharxiv

arXiv2025

Chaos dynamics of charged particles near Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes

The Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) dilatonic black hole, a key solution in low-energy string theory, exhibits previously unexplored chaotic dynamics for charged test particles under electromagnetic influence. While characterizing such chaos necessitates high-precision numerical solutions, our prior research confirms the explicit symplectic algorithm as the optimal numerical integration tool for strongly curved gravitational celestial systems. Leveraging the Hamiltonian formulation of the GMGHS black hole, we develop an optimized fourth-order symplectic algorithm $PR{K_6}4$. This algorithm enables a systematic investigation of the chaotic motion employing four distinct chaos indicators: Shannon entropy, Poincare sections, the maximum Lyapunov exponents, and the Fast Lyapunov indicators. Our results demonstrate a critical dependence of chaos on both electric charge ($Q$, characterized by the Coulomb parameter $Q^*$) and magnetic charge ($Q_m$). Specifically, in electrically charged backgrounds, order-to-chaos transitions arise with increasing $Q$ or decreasing $Q^*$. Conversely, in magnetically charged backgrounds, chaos emerges as $Q_m$ increases. These findings validate Shannon entropy as a robust chaos indicator within relativistic frameworks and provide novel insights on the dynamics of string-theoretic black holes.

hep-th↗

arXiv2025

Chaotic motion of the charged test particle in a Kerr-MOG black hole with explicit symplectic algorithms

The Kerr-MOG black hole has recently attracted significant research attention and has been extensively applied in various fields. To accurately characterize the long-term dynamical evolution of charged particles around Kerr-MOG black hole, it is essential to utilize numerical algorithms that are high-precision, stable, and capable of preserving the inherent physical structural properties. In this study, we employ explicit symplectic algorithms combined with the Hamiltonian splitting technique to numerically solve the equations of motion for charged particles. Initially, by decomposing the Hamiltonian into five integrable components, three distinct explicit symplectic algorithms ($S2$, $S4$, and $PR{K_6}4$) are constructed. Numerical experiments reveal that the $PR{K_6}4$ algorithm achieves superior accuracy. Subsequently, we utilize Poincaré sections and the Fast Lyapunov Indicator (FLI) to investigate the dynamic evolution of the particle. Our numerical results demonstrate that the energy $E$, angular momentum $L$, magnetic field parameter $β$, black hole spin parameter $a$, and MOG parameter $α$ all significantly influence the particle's motion. Specifically, the chaotic region expands with increases in $E$, $β$, or $α$, but contracts with increases in $a$ or $L$. Furthermore, when any two of these five parameters are varied simultaneously, it becomes evident that $a$ and $L$ predominantly dictate the system's behavior. This study not only offers novel insights into the chaotic dynamics associated with Kerr-MOG black holes but also extends the application of symplectic algorithms in strong gravitational field.

gr-qc↗