Brauer-Kuroda relations for ramified graph covers

Abstract

We establish graph-theoretic analogues of the Brauer-Kuroda relations for ramified Galois covers of finite graphs with arbitrary finite Galois groups. These formulas relate the numbers of spanning trees of intermediate quotient graphs and recover the corresponding formulas for unramified covers. Our proofs use $h$-functions defined on multiplicity spaces of complex representations of the Galois group.

arXiv comment29 pages, 4 figures