论文部分内容阅读
It is well-known that each nonnegative integral flow of a directed graph can be decomposed into a sum of nonnegative graph circuit flows, which cannot be further decomposed into nonnegative integral sub-flows.This is equivalent to saying that indecomposable flows of graphs are those graph circuit flows.Turning from graphs to signed graphs, the indecomposable flows are much richer than that of ordinary unsigned graphs.The present paper is to give a complete description of indecomposable flows of signed graphs from the viewpoint of resolution of singularities by introducing covering graphs.