Abstract
TheMonotone Upper Bound Problem (Klee, 1965) asks if the maximal numberM(d,n) of vertices in a monotone path along edges of ad-dimensional polytope withn facets can be as large as conceivably possible: IsM(d,n)=M ubt (d,n), the maximal number of vertices that ad-polytope withn facets can have according to the Upper Bound Theorem?
We show that in dimensiond=4, the answer is “yes”, despite the fact that it is “no” if we restrict ourselves to the dual-to-cyclic polytopes. For eachn≥5, we exhibit a realization of a polar-to-neighborly 4-dimensional polytope withn facets and a Hamilton path through its vertices that is monotone with respect to a linear objective function.
This constrasts an earlier result, by which no polar-to-neighborly 6-dimensional polytope with 9 facets admits a monotone Hamilton path.
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The author was financed in part by the DFG GraduiertenkollegCombinatorics, Geometry, and Computation (GRK 588-2), the GIF projectCombinatorics of Polytopes in Euclidean Spaces (I-624-35.6/1999), and post-doctoral fellowships from MSRI and Institut de Matemàtica de la Universitat de Barcelona.
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Pfeifle, J. Long monotone paths on simple 4-polytopes. Isr. J. Math. 150, 333–355 (2005). https://doi.org/10.1007/BF02762386
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DOI: https://doi.org/10.1007/BF02762386