Benjamin Matschke, Francisco Santos, Christophe Weibel
Published 2012-02-21, updated 2013-05-06Version 2
Santos' construction of counter-examples to the Hirsch Conjecture (2012) is based on the existence of prismatoids of dimension d of width greater than d. Santos, Stephen and Thomas (2012) have shown that this cannot occur in $d \le 4$. Motivated by this we here study the width of 5-dimensional prismatoids, obtaining the following results: - There are 5-prismatoids of width six with only 25 vertices, versus the 48 vertices in Santos' original construction. This leads to non-Hirsch polytopes of dimension 20, rather than the original dimension 43. - There are 5-prismatoids with $n$ vertices and width $\Omega(\sqrt{n})$ for arbitrarily large $n$. Hence, the width of 5-prismatoids is unbounded.
Comments: 31 pages, 10 figures. Changes from v1: the introduction has been edited, and a minor correction made in the statement of Proposition 1.5
A counterexample to the Hirsch conjecture
Companion to "An update on the Hirsch conjecture"
An update on the Hirsch conjecture
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