The Cayley distance between two permutations $\pi, \sigma \in S_n$ is the minimum number of \textit{transpositions} required to obtain the permutation $\sigma$ from $\pi$. When we only allow adjacent transpositions, the minimum number of such transpositions to obtain $\sigma$ from $\pi$ is referred to the Kendall $\tau$-distance. A set $C$ of permutation words of length $n$ is called a $t$-Cayley permutation code if every pair of distinct permutations in $C$ has Cayley distance greater than $t$. A $t$-Kendall permutation code is defined similarly. Let $C(n,t)$ and $K(n,t)$ be the maximum size of a $t$-Cayley and a $t$-Kendall permutation code of length $n$, respectively. In this paper, we improve the Gilbert-Varshamov bound asymptotically by a factor $\log(n)$, namely \[ C(n,t) \geq \Omega_t\left(\frac{n!\log n}{n^{2t}}\right) \text{ and } K(n,t) \geq \Omega_t\left(\frac{n! \log n}{n^t}\right).\] Our proof is based on graph theory techniques.

翻译：两个排列π, σ ∈ S_n之间的Cayley距离是指从π变换到σ所需的最少对换（transpositions）次数。当仅允许相邻对换时，从π变换到σ所需的最少相邻对换次数称为Kendall τ距离。若长度为n的置换词集合C中任意两个不同置换间的Cayley距离均大于t，则称C为t-Cayley置换码。类似可定义t-Kendall置换码。设C(n,t)和K(n,t)分别表示长度为n的t-Cayley与t-Kendall置换码的最大基数。本文将Gilbert-Varshamov界渐近提升一个因子log(n)，即\[ C(n,t) \geq \Omega_t\left(\frac{n!\log n}{n^{2t}}\right) \text{ 且 } K(n,t) \geq \Omega_t\left(\frac{n! \log n}{n^t}\right).\] 我们的证明基于图论方法。