Holographic superfluid flows with a localized repulsive potential
  We investigate a holographic model of superfluid flows with an external repulsive potential. When the strength of the potential is sufficiently weak, we analytically construct two steady superfluid flow solutions. As the strength of the potential is increased, the two solutions merge into a single critical solution at a critical strength, and then disappear above the critical value, as predicted by a saddle-node bifurcation theory. We also analyze the spectral function of fluctuations around the solutions under a certain decoupling approximation. 
Akihiro Ishibashi, Kengo Maeda, Takashi Okamura
hep-th cond-mat.str-el gr-qc