BRAUER-KURODA RELATIONS FOR HIGHER CLASS NUMBERS

Abstract

<p>Arising from permutation representations of finite groups, Brauer-Kuroda relations are relations between Dedekind zeta functions of certain intermediate fields of a Galois extension of number fields. Let E be a totally real number field and let n ≥ 2 be an even integer. Taking s = 1 − n in the Brauer-Kuroda relations then gives a correspondence between orders of certain motivic and Galois cohomology groups. Following the works of Voevodsky and Wiles (cf. [33], [36]), we show that these relations give a direct relation on the motivic cohomology groups, allowing one to easily compute the higher class numbers, the orders of these motivic cohomology groups, of fields of high degree over Q from the corresponding values of its subfields. This simplifies the process by restricting the computations to those of fields of much smaller degree, which we are able to compute through Sage ([30]). We illustrate this with several extensive examples.</p>