Definition of Shimura curves in positive characteristics -- Jie Xia, March 14, 2014

Classical Shimura varieties are defined over the complex field and generally have number fields as the field of definition. Motivated by an example constructed by Mumford, we find conditions which guarantee that a curve in char. p lifts to a Shimura curve of Hodge type. The conditions are intrinsic in positive characteristics. So we can take them as the definition of Shimura curves in char. p. In this talk, I will first discuss Mumford's example, and then present such conditions in terms of Dieudonne crystals, crystalline Hodge cycles and l-adic monodromy. One of the key ingredients in the proofs is a deformation result on versally deformed Barsotti-Tate groups.