The Speciality Index as invariant indicator in the BKL Mixmaster   Dynamics
  The speciality index, which has been mainly used in Numerical Relativity for studying gravitational waves phenomena as an indicator of the special or non-special Petrov type character of a spacetime, is applied here in the context of Mixmaster cosmology, using the Belinski-Khalatnikov-Lifshitz map. Possible applications for the associated chaotic dynamics are discussed. 
Christian Cherubini, Donato Bini, Marco Bruni, Zoltan Perjes