Formal completions of Néron models for algebraic tori
We calculate the formal group law which represents the completion of the Néron model of an algebraic torus over the rationals that splits in a tamely ramified abelian extension. As a tools in the proof, we define and give criterions to compute the Weil restriction of a formal group law and the analog of the fixed part of a formal group law with respect to the action of a (finite) group.
math.AG↗