Local symmetries are primarily defined in the case of spacetime, but several authors have them outside this context, sometimes with help groupoids. We show that, many cases, local can be as global symmetries. also that groups used, rather than groupoids, to handle Examples given for graphs and networks, color symmetry tilings. The definition physics is discussed.

We generalise the Margolis-Meakin graph expansion of a group to a construction for ordered groupoids, and show that the graph expansion of an ordered groupoid enjoys structural properties analogous to those for graph expansions of groups. We also use the Cayley graph of an ordered groupoid to prove a version of McAlister’s P–theorem for incompressible ordered groupoids. AMS 2000 Mathematics sub...

We study isomorphism classes of symplectic dual pairs P ← S → P , where P is an integrable Poisson manifold, S is symplectic, and the two maps are complete, surjective Poisson submersions with connected and simply-connected fibres. For fixed P , these Morita self-equivalences of P form a group Pic(P ) under a natural “tensor product” operation. Variants of this construction are also studied, fo...

We introduce the notion of Hopf algebroids, in which neither the total algebras nor the base algebras are required to be commutative. We give a class of Hopf algebroids associated to module algebras of the Drinfeld doubles of Hopf algebras when the Rmatrices act properly. When this construction is applied to quantum groups, we get examples of quantum groupoids, which are semi-classical limits o...

Oblivious polynomial evaluation is a protocol involving two parties, a sender whose input is a polynomial P , and a receiver whose input is a value α. At the end of the protocol the receiver learns P (α) and the sender learns nothing. We describe efficient constructions for this protocol, which are based on new intractability assumptions that are closely related to noisy polynomial reconstructi...

Delegating the computation of a polynomial to a server in a verifiable way is challenging. An even more challenging problem is ensuring that this polynomial remains hidden to clients who are able to query such a server. In this paper, we formally define the notion of Private Polynomial Evaluation (PPE). Our main contribution is to design a rigorous security model along with relations between th...

Alternative titles of this paper would have been “Index theory without index” or “The Baum–Connes conjecture without Baum.” In 1989, Rieffel introduced an analytic version of deformation quantization based on the use of continuous fields ofC∗-algebras. We review how a wide variety of examples of such quantizations can be understood on the basis of a single lemma involving amenable groupoids. Th...