Topological rigidity of maps in positive characteristic and anabelian geometry

We study pairs of non-constant maps between two integral schemes of finite type over two (possibly different) fields of positive characteristic. When the target is quasi-affine, Tamagawa showed that the two maps are equal up to a power of Frobenius if and only if they induce the same homomorphism on their étale fundamental groups. We extend Tamagawa’s result by adding a purely topological criterion for maps to agree up to a power of Frobenius.