Two-valued states on Baer $^*$-semigroups
  In this paper we develop an algebraic framework that allows us to extend families of two-valued states on orthomodular lattices to Baer $^*$-semigroups. We apply this general approach to study the full class of two-valued states and the subclass of Jauch-Piron two-valued states on Baer $^*$-semigroups. 
Hector Freytes, Graciela Domenech and Christian de Ronde
quant-ph math.RA