Russian Doll Renormalization Group and Superconductivity
  We show that an extension of the standard BCS Hamiltonian leads to an infinite number of condensates with different energy gaps and self-similar properties, described by a cyclic RG flow of the BCS coupling constant which returns to its original value after a finite RG time. 
Andre LeClair, Jose Maria Roman, German Sierra (IFT, CSIC-UAM, SPAIN)