The principal result of this paper is an explicit description of the structure of ramification subgroups of the Galois group of 2-dimensional local field modulo its subgroup of commutators of order . This result plays a clue role in the author’s proof of an analogue of the Grothendieck Conjecture for higher dimensional local fields, cf. Proc. Steklov Math. Institute, vol. 241, 2003, pp. 2-34.
A local analogue of the Grothendieck Conjecture is an equivalence between the category of complete discrete valuation fields with finite residue fields of characteristic and the category of absolute Galois groups of fields together with their ramification filtrations. The case of characteristic 0 fields was studied by Mochizuki several years ago. Then the author of this paper proved it by a different method in the case (but with no restrictions on the characteristic of ). In this paper...
The field-of-norms functor is applied to deduce an explicit formula for the Hilbert symbol in the mixed characteristic case from the explicit formula for the Witt symbol in characteristic in the context of higher local fields. Is is shown that a “very special case” of this construction gives Vostokov’s explicit formula.
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