Title: A note on effective descent for overconvergent isocrystals,
Abstract: In this short note we explain the proof that proper surjective and faithfully
flat maps are morphisms of effective descent for overconvergent isocrystals. We
then show how to deduce the folklore theorem that for an arbitrary variety over
a perfect field of characteristic $p$, the Frobenius pull-back functor is an
equivalence on the overconvergent category.