Metalinear structures and the substructural logic of quantum measurements

This paper presents three classes of metalinear structures that abstract some of the properties of Hilbert spaces. Those structures include a binary relation that expresses orthogonality between elements and enables the definition of an operation that generalizes the projection operation in Hilbert spaces. The logic defined by the most general class has a unitary connective and two dual binary connectives that are neither commutative nor associative. It is a substructural logic of sequents in which the Exchange rule is extremely limited and Weakening is also restricted. This provides a logic for quantum measurements whose proof theory is attractive. A completeness result is proved. An additional property of the binary relation ensures that the structure satisfies the MacLane-Steinitz exchange property and is some kind of matroid. Preliminary results on richer structures based on a sort of real inner product that generalizes the Born factor of Quantum Physics are also presented.