Oblique dark solitons in supersonic flow of a Bose-Einstein condensate
  In the framework of the Gross-Pitaevskii mean field approach it is shown that the supersonic flow of a Bose-Einstein condensate can support a new type of pattern--an oblique dark soliton. The corresponding exact solution of the Gross-Pitaevskii equation is obtained. It is demonstrated by numerical simulations that oblique solitons can be generated by an obstacle inserted into the flow. 
G.A. El, A. Gammal, A.M. Kamchatnov