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arXiv 1701.07155math.COmath.MG
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七维Keller立方拼接猜想的求解

Towards Resolving Keller's Cube Tiling Conjecture in Dimension Seven

Andrzej P. Kisielewicz

摘要:

$\mathbb{R}^d$的立方体平铺是成对不相交立方体$[0,1)^d+T=\{[0,1)^d+t\colon t\in T\}$的族,使得$\bigcup_{t\in T}([0,1)^d+t)=\mathbb{R}^d$。两个立方体$[0,1)^d+t$、$[0,1)^d+s$被称为孪生对,如果对于某些$j\in [d]=\{1,\ldots, d\}$为$|t_j-s_j|=1$,而对于每个$i\in [d]\setminus \{j\}$为$t_i=s_i$。在$1930$中,Keller证明了在$\mathbb{R}^d$的每个立方体镶嵌中都有一个孪生对。Keller猜想对$d\leq 6$维成立,对所有$d\geq 8$维成立。对于$d=7$,猜想仍然是开放的。令$x\in \mathbb{R}^d$、$i\in [d]$和$L(T,x,i)$为矢量$t\in T$的所有$i$第一坐标$t_i$的集合,使得$([0,1)^d+t)\cap ([0,1]^d+x)\neq \emptyset$和$t_i\leq x_i$。设$r^-(T)=\min_{x\in \mathbb{R}^d}\; \max_{1\leq i\leq d}|L(T,x,i)|$和$r^+(T)=\max_{x\in \mathbb{R}^d}\; \max_{1\leq i\leq d}|L(T,x,i)|$。已知如果$r^-(T)\leq 2$或$r^+(T)\geq 5$,则Keller猜想对$d=7$成立.在本文中,我们表明,这也是真实的$d=7$,如果$r^+(T)=4$。因此,如果$[0,1)^7+T$是凯勒猜想的一个反例,那么$r^+(T)=3$,这是凯勒猜想的最后一个未解的例子。另外,给出了Keller猜想在$d\leq 6$维上的一个新的证明.

英文摘要:

A cube tiling of $\mathbb{R}^d$ is a family of pairwise disjoint cubes $[0,1)^d+T=\{[0,1)^d+t\colon t\in T\}$ such that $\bigcup_{t\in T}([0,1)^d+t)=\mathbb{R}^d$. Two cubes $[0,1)^d+t$, $[0,1)^d+s$ are called a twin pair if $|t_j-s_j|=1$ for some $j\in [d]=\{1,\ldots, d\}$ and $t_i=s_i$ for every $i\in [d]\setminus \{j\}$. In $1930$, Keller conjectured that in every cube tiling of $\mathbb{R}^d$ there is a twin pair. Keller's conjecture is true for dimensions $d\leq 6$ and false for all dimensions $d\geq 8$. For $d=7$ the conjecture is still open. Let $x\in \mathbb{R}^d$, $i\in [d]$, and let $L(T,x,i)$ be the set of all $i$th coordinates $t_i$ of vectors $t\in T$ such that $([0,1)^d+t)\cap ([0,1]^d+x)\neq \emptyset$ and $t_i\leq x_i$. Let $r^-(T)=\min_{x\in \mathbb{R}^d}\; \max_{1\leq i\leq d}|L(T,x,i)|$ and $r^+(T)=\max_{x\in \mathbb{R}^d}\; \max_{1\leq i\leq d}|L(T,x,i)|$. It is known that if $r^-(T)\leq 2$ or $r^+(T)\geq 5$, then Keller's conjecture is true for $d=7$. In the paper we show that it is also true for $d=7$ if $r^+(T)=4$. Thus, if $[0,1)^7+T$ is a counterexample to Keller's conjecture, then $r^+(T)=3$, which is the last unsolved case of Keller's conjecture. Additionally, a new proof of Keller's conjecture in dimensions $d\leq 6$ is given.

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