A Second Superconducting Transition in an Anisotropic Superconductor ---A Description of the Hydrodynamic Orderparameter Motion---
We show that an anisotropic superconductor can become unstable and undergo asecond superconducting transition provided that there exists extraattractive interaction which is close in magnitude to the one by which thefirst transition is brought about. In the present study we describe theinstability from a dynamical standpoint. To do so we have to investigate themotion of the orderparameter in the hydrodynamic limit. We then see that theinstability is represented as softening of the hydrodynamic collective modewhich corresponds to the fluctuation inducing the instability.