SLOPE FILTRATION OF QUASI-UNIPOTENT OVERCONVERGENT F-ISOCRYSTALS

We study local properties of quasi-unipotent overconvergent F-isocryst als on a curve over a perfect field of positive characteristic p. For a phi-delta-module over the Robba ring R, we define the slope filtrati on for Frobenius structures. We prove that an overconvergent F-isocrys tal is quasi-unipotent if and only if it has the slope filtration for Frobenius structures locally at every point on the complement of the c urve.