The status of the KSS bound and its possible violations (How perfect can   a fluid be?)
  In this work we briefly review the Kovtun-Son-Starinet (KSS) computation of the ratio eta/s for quantum field theories with gravitational dual and the related conjecture that it is bound from below by 1/(4 pi). We discuss the validity of the bound and the nature of its possible violations, its relevance for RHIC, its connection with phase transitions and other related issues. 
Antonio Dobado, Felipe J. Llanes-Estrada and Juan Miguel Torres Rincon