Complex Structure of the Four-Dimensional Kerr Geometry: Stringy System,   Kerr Theorem, and Calabi-Yau Twofold
  The 4d Kerr geometry displays many wonderful relations with quantum world and, in particular, with superstring theory. The lightlike structure of fields near the Kerr singular ring is similar to the structure of Sen solution for a closed heterotic string. Another string, open and complex, appears in the complex representation of the Kerr geometry initiated by Lind and Newman . Combination of these strings forms a membrane source of the Kerr geometry which is parallel to the string/M-theory unification. In this paper we give one more evidence of this relationship, emergence of the Calabi-Yau twofold (K3 surface) in twistorial structure of the Kerr geometry as a consequence of the Kerr theorem. Finally, we indicate that the Kerr stringy system may correspond to a complex embedding of the critical N=2 superstring. 
Alexander Burinskii
hep-th gr-qc