In this talk, we will introduce the relative logarithmic de Rham-Witt sheaves on a semistable scheme X over a local ring of postive characteristic p, and study duality theorems. As an application, we will define a filtration on the abelianized /'etale fundamental group of open complement of a simple normal crossing divisior on X. In a special case, this filtration coincides with higher ramification groups in local class field theory.

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