M. Rapoport et M. Richartz, ON THE CLASSIFICATION AND SPECIALIZATION OF F-ISOCRYSTALS WITH ADDITIONAL STRUCTURE, Compositio mathematica, 103(2), 1996, pp. 153-181
We generalize Grothendieck's semicontinuity theorem for F-isocrystals
over a base scheme of characteristic p to F-isocrystals with G-structu
re, where G is a connected reductive algebraic group over Q(p).