[Zurück]

A. Schmitt, S. Stetina, A. Haber:
"Instabilities in relativistic two-component (super)fluids";
Physical Review D, 93 (2016), 025011.

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 nonentrainment coupling. We analyze the onset of the various instabilities systematically and point out that the dynamical two-stream instability can occur only 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 are of potential relevance for (super)fluids in neutron stars and, in the nonrelativistic limit of our results, in the laboratory.

http://dx.doi.org/10.1103/PhysRevD.93.025011