An observable effects a schematization of the Quantum event structure by correlating Boolean algebras picked by measurements with the Borel algebra of the real line. In a well-defined sense Boolean observables play the role of coordinatizing objects in the Quantum world, by picking Boolean figures and subsequently opening Boolean windows for the perception of the latter, interpreted as local me...

We offer a sufficient condition for a closed subset in an association scheme to be maximal. The result generalizes naturally the well-known (group-theoretical) fact that the one-point-stabilizer of a flag transitive automorphism group of a 2-design with *=1 must be a maximal subgroup. In finite group theory, there exist a lot of (important) sufficient conditions for a subgroup to be maximal. In...

Group signature scheme could be applied to the valid members to represent the group. The validity of the signature could be verified by the receiver. On the other hand, the member who signs the message could not be found. However, the group manager could reveal and identify the signer if it is necessary. Concerning with a high performance on security, a new group signature scheme based on a dis...