Q+ Hangout: Tobias Fritz (Perimeter Institute) скачать в хорошем качестве

Q+ Hangout: Tobias Fritz (Perimeter Institute)

We'd like to announce the next Q+ hangout.  As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment on the event page.  Everyone else can watch on the livestream. Title: A Combinatorial Approach to Nonlocality and Contextuality Abstract: Most work on contextuality so far has focused on specific examples and concrete proofs of the Kochen-Specker theorem, while general definitions and theorems about contextuality are sparse. For example, it is commonly believed that nonlocality is a special case of contextuality, but what exactly does this mean? After a brief discussion of previous work, I will introduce our "device-independent" approach to contextuality based on the mathematics of test spaces and explain how nonlocality is indeed a special case of contextuality. This work builds on the graph-theoretic approach of Cabello, Severini and Winter by improving on several of its shortcomings and merging it with the work of Foulis and Randall on test spaces. Our results include: (1) various relationships to graph invariants, similar to CSW; (2) a proof that our set of quantum models cannot be characterized by a graph invariant; (3) a proof that the set of all models satisfying the Consistent Exclusivity principle at any number of copies is not convex; (4) new results on the Shannon capacity of graphs; (5) an "inverse sandwich conjecture" with ramifications for C*-algebra theory and quantum logic. This talk is based on http://arXiv.org/abs/1212.4084