The Locality Axiom in Quantum Field Theory and Tensor Products of   $C^*$-algebras
  The prototype of mutually independent systems are systems which are localized in spacelike separated regions. In the framework of locally covariant quantum field theory we show that the commutativity of observables in spacelike separated regions can be encoded in the tensorial structure of the functor which associates unital $C^*$-algebras (the local observable algebras) to globally hyperbolic spacetimes. This holds under the assumption that the local algebras satisfy the split property and involves the minimal tensor product of $C^*$-algebras. 
Romeo Brunetti, Klaus Fredenhagen, Paniz Imani, Katarzyna Rejzner
math-ph gr-qc math.MP math.OA