Combinatorial Belyi Cuspidalization and Arithmetic Subquotients of the Grothendieck–Teichmüller Group

Abstract

In this paper, we develop a certain combinatorial version of the theory of Belyi cuspidalization developed by Mochizuki. Write Q ⊆ C for the subfield of algebraic numbers ∈ C. We then apply this theory of combinatorial Belyi cuspidalization to certain natural closed subgroups of the Grothendieck-Teichmüller group associated to the field of p-adic numbers [where p is a prime number] and to stably ×μ-indivisible subfields of Q, i.e., subfields for which every finite field extension satisfies the property that every nonzero divisible element in the field extension is a root of unity. 2010 Mathematics Subject Classification: Primary 14H30.