Shimura varieties are defined over complex numbers and generally have number fields as the field of definition. Motivated by an example constructed by Mumford, we find conditions which guarantee a curve in char. p lifts to a Shimura curve of Hodge type. The conditions are intrinsic in positive characteristics and thus they shed light on a definition of Shimura curves in positive characteristics. 

In this talk, I will start with modular curves, and discuss the moduli interpretation of Shimura curves. Then I will present such a condition in terms of isocrystals. Time permitting, I would show a deformation result on Barsotti-Tate groups, which serves as a key step in the proof.