中国物理B ›› 2025, Vol. 34 ›› Issue (11): 110501-110501.doi: 10.1088/1674-1056/addccf
Qiang Zhang(张强), Haojie Luo(罗浩杰), Bingling Cen(岑炳玲), and Yu Xue(薛郁)†
Qiang Zhang(张强), Haojie Luo(罗浩杰), Bingling Cen(岑炳玲), and Yu Xue(薛郁)†
摘要: A Hamiltonian mean-field model with long-range four-body interactions is proposed. The model describes a long-range mean-field system in which $N$ unit-mass particles move on a unit circle. Each particle $\theta_{i}$ interacts with any three other particles through an infinite-range cosine potential with an attractive interaction ($\varepsilon > 0$). By applying a method that remaps the average phase of global particle pairs onto a new unit circle, and using the saddle-point technique, the partition function is solved analytically after introducing four-body interactions, yielding expressions for the free energy $f$ and the energy per particle $U$. These results were further validated through numerical simulations. The results show that the system undergoes a second-order phase transition at the critical energy $U_{\rm c}$. Specifically, the critical energy corresponds to $U_{\rm c}=0.32$ when the coupling constant $\varepsilon =5$, and $U_{\rm c}=0.63$ when $\varepsilon =10$. Finally, we calculated the system's largest Lyapunov exponent $\lambda $ and kinetic energy fluctuations $\varSigma $ through numerical simulations. It is found that the peak of the largest Lyapunov exponent $\lambda $ occurs slightly below the critical energy $U_{\rm c}$, which is consistent with the point of maximum kinetic energy fluctuations $\varSigma $. And there is a scaling law of $\varSigma /N^{1/2}\propto \lambda $ between them.
中图分类号: (Classical statistical mechanics)