Let be a complete discrete valuation field of characteristic , with valuation ring and perfect residue field of positive characteristic . We prove that a proper and smooth curve over , admitting a semistable model over , has good reduction if and only if its unipotent -adic étale fundamental group is crystalline.
"A -adic nonabelian criterion for good reduction of curves." Duke Math. J. 164 (13) 2597 - 2642, 1 October 2015. https://doi.org/10.1215/00127094-3146817