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.
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