New Results on Tripod Packings

Patric R.J. Östergård*, Antti Pöllänen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Consider an n× n× n cube Q consisting of n 3 unit cubes. A tripod of order n is obtained by taking the 3 n- 2 unit cubes along three mutually adjacent edges of Q. The unit cube corresponding to the vertex of Q where the edges meet is called the center cube of the tripod. The function f(n) is defined as the largest number of integral translates of such a tripod that have disjoint interiors and whose center cubes coincide with unit cubes of Q. The value of f(n) has earlier been determined for n≤ 9. The function f(n) is here studied in the framework of the maximum clique problem, and the values f(10) = 32 and f(11) = 38 are obtained computationally. Moreover, by prescribing symmetries, constructive lower bounds on f(n) are obtained for n≤ 26. A conjecture that f(n) is always attained by a packing with a symmetry of order 3 that rotates Q around the axis through two opposite vertices is disproved.

Original languageEnglish
Pages (from-to)271–284
Number of pages14
JournalDiscrete and Computational Geometry
Volume61
Issue number2
Early online date18 Jun 2018
DOIs
Publication statusPublished - 15 Mar 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Clique
  • Monotonic matrix
  • Packing
  • Semicross
  • Stein corner
  • Tripod
  • 52C17

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    Construction and Classification of Discrete Mathematic Structures

    Kokkala, J., Laaksonen, A., Heinlein, D., Ganzhinov, M., Östergård, P. & Szollosi, F.

    01/09/201524/09/2019

    Project: Academy of Finland: Other research funding

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