Weinberg bounds over nonspherical graphs
نویسندگان
چکیده
Let G Aut and E G denote the automorphism group and the edge set of a graph G, respectively. Weinberg’s Theorem states that 4 is a constant sharp upper bound on the ratio G E G Aut over planar (or spherical) 3-connected graphs G. We have obtained various analogues of this theorem for nonspherical graphs, introducing two Weinberg-type bounds for an arbitrary closed surface , namely: G E G W W G T P Aut sup and def , where supremum is taken over the polyhedral graphs G with respect to for WP and over the graphs G triangulating for WT . We have proved that Weinberg bounds are finite for any surface; in particular: WP WT 48 for the projective plane, and WT 240 for the torus. We have also proved that the original Weinberg bound of 4 holds over the graphs G triangulating the projective plane with at least 8 vertices and, in general, for the graphs of sufficiently large order triangulating a fixed closed surface .
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عنوان ژورنال:
- Journal of Graph Theory
دوره 33 شماره
صفحات -
تاریخ انتشار 2000