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研究生: 王昕芸
Wang, Sin-Yun
論文名稱: Exact hyperplane covers for subsets of bricks
Exact hyperplane covers for subsets of bricks
指導教授: 林延輯
Lin, Yen-Chi
口試委員: 林延輯
Lin, Yen-Chi
俞韋亘
Yu, Wei-Hsuan
戴尚年
Shagnik Das
口試日期: 2023/06/28
學位類別: 碩士
Master
系所名稱: 數學系
Department of Mathematics
論文出版年: 2024
畢業學年度: 112
語文別: 英文
論文頁數: 28
英文關鍵詞: hypercube, bricks, hyperplanes, exact covers
DOI URL: http://doi.org/10.6345/NTNU202400601
論文種類: 學術論文
相關次數: 點閱:93下載:2
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  • Let h_1, h_2, ..., h_n be n positive integers, and V=V(h_1, h_2, ..., h_n) be a set of lattice points (y_1, y_2, ..., y_n) such that 0≤ y_i≤ h_i. Given S⊆V=V(h_1, h_2, ..., h_n), the exact cover of VS is a collection of hyperplanes whose union intersects V(h_1, h_2, ..., h_n) exactly in VS. That is, the points from S are not covered. The exact cover number of VS, denoted by ec(VS), is the minimum size of an exact cover of VS. Alon and Füredi (1993) proved that ec({0, 1}^n{0})=n and if S⊆V=V(h_1, h_2, ..., h_n) with |S|=1, then ec(VS)= Σ(from i=1 to n)h_i. Aaronson et al. (2021) showed that if |S|=2, 3, then ec({0, 1}^nS)=n-1. If |S|=4, then ec({0, 1}^nS)=n-1 if there is a hyperplane Q with |Q∩S|=3, and ec({0, 1}^nS)=n-2 otherwise.

    In this paper, we combine the problems mentioned above, and study the problem of covering V(h_1, h_2, ..., h_n) while missing two, three, or four points. Let S be a subset of V=V(h_1, h_2, ..., h_n) with |S|=2,3,4. Our main results are as follows. If |S|=2, then ec(VS)= Σ(from i=1 to n)h_i-1. If |S|=3 and the dimension n=2, then ec(VS)=h_1+h_2-2 if the three points in S are coaxial, and ec(VS)=h_1+h_2-1 otherwise. If |S|=3 and the three points in S are not collinear, then ec(VS)= Σ(from i=1 to n)h_i-1. If |S|=3 and the three points in S are coaxial, then ec(VS)= Σ(from i=1 to n)h_i-2. For the case of missing three collinear points and missing four points, we have partial results. Some cases have matching upper and lower bounds, but some still have gaps.

    1 Introduction 1 2 Covering all but two points 3 2.1 Lower bound 3 2.2 Upper bound construction 4 3 Covering all but three points 5 3.1 The case of dimension n=2 5 3.2 Lower bound 9 3.3 Upper bound construction for covering all but three non-collinear points 9 3.4 Upper bound construction for covering all but three collinear points 18 4 Covering all but four points in R^2 22 5 Conclusion and discussion 26 References 28

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