Parity Breaking Medium and Squeeze Operators
  The transition between a Minkowski space region and a parity breaking medium domain is thoroughly discussed. The requirement of continuity of the field operator content across the separating boundary of the two domains leads to Bogolyubov transformations, squeezed pairs states and squeeze operators that turn out to generate a functional SU(2) algebra. According to this algebraic approach, the reflection and transmission probability amplitude across the separating boundary are computed. The probability rate of the emission or absorption of squeezed pairs out of the vacuum (generalization of the Sauter-Schwinger-Nikishov formula) is obtained. 
A. A. Andrianov, S. S. Kolevatov and R. Soldati
hep-th astro-ph.HE hep-ph nucl-th