The Yamada polynomial of lens spatial graphs

Abstract

Let [Formula: see text] be a spatial graph in the 3-sphere which covers a graph in the lens space. We introduce a combinatorial representation of [Formula: see text] which reflects the symmetry of the spatial graph. This representation involves a ribbon n-graph and the generator of the center of the n-braid group. We apply this result to study the Yamada polynomial of a class of lens spatial graphs.