$n$立方体的$q$类似物的复杂性

A q-analog of the adjacency matrix of the n-cube

We define a q-analog of the adjacency matrix of the n-cube, determine its eigenvalues and write down a canonical eigenbasis. We give a weighted count of the number of rooted spanning trees in the q-analog of the n-cube. Remarks on the previous version: The q-analog of the Kac matrix appears in Terwilliger's classification of Leonard pairs and as such its eigenvalues and eigenvectors were known. Reference added to Terwilliger's papers and also to a paper of Johnson. Title changed to reflect this.

The largest projective cube-free subsets of $\mathbb{Z}_{2^n}$

In the Boolean lattice, Sperner's, Erdős's, Kleitman's and Samotij's theorems state that families that do not contain many chains must have a very specific layered structure. We show that if instead of $\mathbb{Z}_2^n$ we work in $\mathbb{Z}_{2^n}$, several analogous statements hold if one replaces the word $k$-chain by projective cube of dimension $2^{k-1}$. We say that $B_d$ is a projective cube of dimension $d$ if there are numbers $a_1, a_2, \ldots, a_d$ such that $$B_d = \left\{\sum_{i\in I} a_i \bigg\rvert \emptyset \neq I\subseteq [d]\right\}.$$ As an analog of Sperner's and Erdős's the…

Linear orderings of combinatorial cubes

We show that, for every linear ordering of $[2]^n$, there is a large subcube on which the ordering is lexicographic. We use this to deduce that every long sequence contains a long monotone subsequence supported on an affine cube. More generally, we prove an analogous result for linear orderings of $[k]^n$. We show that, for every such ordering, there is a large subcube on which the ordering agrees with one of approximately $\frac{(k-1)!}{2(\ln 2)^k}$ orderings.

立方体中间层上布尔函数的查询复杂度

Query complexity of Boolean functions on the middle slice of the cube

本文研究布尔函数在中间层切片上的查询复杂度，证明存在一个函数即使已知输入中0和1数量相同，仍需查询除7位外的所有输入位，回答了Byramji的问题，并给出候选函数及与差异类型问题的联系。

On Algorithms for Solving the Rubik's Cube

In this paper, we present a novel algorithm and its three variations for solving the Rubik's cube more efficiently. This algorithm can be used to solve the complete $n \times n \times n$ cube in $O(\frac{n^2}{\log n})$ moves. This algorithm can also be useful in certain cases for speedcubers. We will prove that our algorithm always works and then perform a basic analysis on the algorithm to determine its algorithmic complexity of $O(n^2)$. Finally, we further optimize this complexity to $O(\frac{n^2}{\log n})$.

On Vanishing Properties of Polynomials on Symmetric Sets of the Boolean Cube, in Positive Characteristic

The finite-degree Zariski (Z-) closure is a classical algebraic object, that has found a key place in several applications of the polynomial method in combinatorics. In this work, we characterize the finite-degree Z-closures of a subclass of symmetric sets (subsets that are invariant under permutations of coordinates) of the Boolean cube, in positive characteristic. Our results subsume multiple statements on finite-degree Z-closures that have found applications in extremal combinatorial problems, for instance, pertaining to set systems (Hegedűs, Stud. Sci. Math. Hung. 2010; Hegedűs, arXiv 2021…