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Construction of graphs with given circular flow numbers
Authors:Zhishi Pan  Xuding Zhu
Abstract:Suppose r ≥ 2 is a real number. A proper r‐flow of a directed multi‐graph equation image is a mapping equation image such that (i) for every edge equation image , equation image ; (ii) for every vertex equation image , equation image . The circular flow number of a graph G is the least r for which an orientation of G admits a proper r‐flow. The well‐known 5‐flow conjecture is equivalent to the statement that every bridgeless graph has circular flow number at most 5. In this paper, we prove that for any rational number r between 2 and 5, there exists a graph G with circular flow number r. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 304–318, 2003
Keywords:graph  flow  circular flow number  rooted‐flow  series join  parallel join  two‐terminal graph
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