Quasi-states on $C\sp{\ast} $-algebras
Johan F. Aarnes · Transactions of the American Mathematical Society · 1970
if it exists, is called the expectation of the observable x in the state a.It is easily seen that the function pa defined on R}.Moreover, if xu x2e<3 are given, there exists at most one x3 e 6 satisfying pa(x3) = P«(xi) + pa(x2) for all a e y (assuming y to contain sufficiently many elements).If such an x3