AI 中文总结
研究具有粒子数守恒的一阶相对论自旋流体动力学的因果性与稳定性，通过推导色散关系发现守恒电荷动力学影响声区并引入新非流体动力学模式，粒子数诱导模式违反因果性，且守恒电荷未消除固有不稳定性，揭示了自旋与电荷动力学相互作用并提供理论约束。
AI 中文摘要
我们研究了具有粒子数守恒的一阶相对论自旋流体动力学的因果性与稳定性。通过推导全局平衡附近线性微扰的完整色散关系，发现守恒电荷动力学改变了声区并引入了电荷中性理论中不存在的额外非流体动力学模式。自旋弛豫模式结构不变，但稳定性条件因电荷扩散和热力学磁化率有了新贡献。更重要的是，粒子数诱导模式在短波长极限下违反因果性条件。还证明了粒子数守恒并未消除一阶自旋流体动力学固有的不稳定性。这些结果揭示了自旋与守恒电荷动力学之间的重要相互作用，并为有限密度下的相对论自旋流体动力学理论提供了重要约束。
英文摘要
We study the causality and stability of first-order relativistic spin hydrodynamics with particle-number conservation. By deriving the complete dispersion relations of linear perturbations around global equilibrium, we find that conserved-charge dynamics modifies the sound sector and introduces additional non-hydrodynamic modes absent in the charge-neutral theory. While the structure of spin relaxation modes remains unchanged, the stability conditions acquire new contributions from charge diffusion and thermodynamic susceptibilities. More importantly, a particle-number-induced mode is shown to violate the causality condition in the short-wavelength limit. We further demonstrate that particle-number conservation does not remove the instability inherent in first-order spin hydrodynamics. These results reveal nontrivial interplay between spin and conserved-charge dynamics and provide important constraints on relativistic spin hydrodynamic theories at finite density.
Comments21 pages, 0 figure
Journal refUniverse 2026, 12, 231
