Abstract
Behzad, Chartrand and Wall proposed the conjecture that any regular digraph of degreer and girthg has ordern ≥ r(g − 1) + 1. The conjecture was proved in [3] for vertex transitive graphs. For Loop Networks the conjecture is equivalent to a theorem of Shepherdson in additive number theory. We show that, except for graphs of a particular structure, Loop Networks, and in general Abelian Cayley graphs, verify the stronger inequalityn ≥ (r + 1)(g − 1) − 1. This bound is best possible.
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Supported by the Spanish Research Council (CICYT) under project TIC 90-0712 and Acción Integrada Hispanofrancesa, TIC 79B.
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Hamidoune, Y.O., Llado, A.S. & Serra, O. Minimum order of loop networks of given degree and girth. Graphs and Combinatorics 11, 131–138 (1995). https://doi.org/10.1007/BF01929482
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DOI: https://doi.org/10.1007/BF01929482