标题： 相对论性双组分（超）流体中的不稳定性 显示英文标题

标题： Instabilities in relativistic two-component (super)fluids

摘要： 我们研究了具有非零流体速度的双流体系统，并计算了它们的声模式，这些声模式表明了各种不稳定性。对于两个零温超流体的情况，我们采用了一个微观场论模型，该模型描述了两个耦合的玻色场，包括内禀耦合和非内禀耦合。我们系统地分析了各种不稳定的起始条件，并指出动态双流不稳定性只能在朗道临界速度之外发生，即在已经能量上不稳定的区域。对于两个正常流体的情况，发现了一个定性的差异：如果流体之间存在内禀耦合，则某些横波模式会在能量上稳定的区域内经历双流不稳定性。由于我们在完全相对论框架下工作，我们的结果非常通用，可能对中子星中的（超）流体以及在我们的结果的非相对论极限情况下实验室中的流体具有潜在的相关性。 显示英文摘要

摘要： We study two-fluid systems with nonzero fluid velocities and compute their sound modes, which indicate various instabilities. For the case of two zero-temperature superfluids we employ a microscopic field-theoretical model of two coupled bosonic fields, including an entrainment coupling and a non-entrainment coupling. We analyse the onset of the various instabilities systematically and point out that the dynamical two-stream instability can only occur beyond Landau's critical velocity, i.e., in an already energetically unstable regime. A qualitative difference is found for the case of two normal fluids, where certain transverse modes suffer a two-stream instability in an energetically stable regime if there is entrainment between the fluids. Since we work in a fully relativistic setup, our results are very general and of potential relevance for (super)fluids in neutron stars and, in the non-relativistic limit of our results, in the laboratory.