Embedding in a perfect code

Non-Binary Diameter Perfect Constant-Weight Codes

Diameter perfect codes form a natural generalization for perfect codes. They are based on the code-anticode bound which generalizes the sphere-packing bound. The code-anticode bound was proved by Delsarte for distance-regular graphs and it holds for some other metrics too. In this paper we prove the bound for non-binary constant-weight codes with the Hamming metric and characterize the diameter perfect codes and the maximum size anticodes for these codes. We distinguish between six families of non-binary diameter constant-weight codes and four families of maximum size non-binary constant-weigh…

There is exactly one Z2Z4-cyclic 1-perfect code

Let ${\cal C}$ be a ${\mathbb{Z}}_2{\mathbb{Z}}_4$-additive code of length $n > 3$. We prove that if the binary Gray image of ${\cal C}$, $C=Φ({\cal C})$, is a 1-perfect nonlinear code, then ${\cal C}$ cannot be a ${\mathbb{Z}}_2{\mathbb{Z}}_4$-cyclic code except for one case of length $n=15$. Moreover, we give a parity check matrix for this cyclic code. Adding an even parity check coordinate to a ${\mathbb{Z}}_2{\mathbb{Z}}_4$-additive 1-perfect code gives an extended 1-perfect code. We also prove that any such code cannot be ${\mathbb{Z}}_2{\mathbb{Z}}_4$-cyclic.

Metrics which turn tilings into binary perfect codes

In this work, we consider tilings of the Hamming cube and look for metrics which turn the tilings into a perfect code. We consider the family of metrics which are determined by a weight and are compatible with the support of vectors (TS-metrics). We determine which of the tilings with small tiles or high rank can be a perfect code for some TS-metric and we characterize all such metrics. Finally, we show some procedures to obtain new perfect codes (relatively to TS-metrics) out of existing ones.

On linear diameter perfect Lee codes with diameter 6

In 1968, Golomb and Welch conjectured that there is no perfect Lee codes with radius $r\ge2$ and dimension $n\ge3$. A diameter perfect code is a natural generalization of the perfect code. In 2011, Etzion (IEEE Trans. Inform. Theory, 57(11): 7473--7481, 2011) proposed the following problem: Are there diameter perfect Lee (DPL, for short) codes with diameter greater than four besides the $DPL(3,6)$ code? Later, Horak and AlBdaiwi (IEEE Trans. Inform. Theory, 58(8): 5490--5499, 2012) conjectured that there are no $DPL(n,d)$ codes for dimension $n\ge3$ and diameter $d>4$ except for $(n,d)=(3,6)$.…

Perfect codes in the lp metric

We investigate perfect codes in $\mathbb{Z}^n$ under the $\ell_p$ metric. Upper bounds for the packing radius $r$ of a linear perfect code, in terms of the metric parameter $p$ and the dimension $n$ are derived. For $p = 2$ and $n = 2, 3$, we determine all radii for which there are linear perfect codes. The non-existence results for codes in $\mathbb{Z}^n$ presented here imply non-existence results for codes over finite alphabets $\mathbb{Z}_q$, when the alphabet size is large enough, and has implications on some recent constructions of spherical codes.

On the binary codes with parameters of doubly-shortened 1-perfect codes

We show that any binary $(n=2^m-3, 2^{n-m}, 3)$ code $C_1$ is a part of an equitable partition (perfect coloring) $\{C_1,C_2,C_3,C_4\}$ of the $n$-cube with the parameters $((0,1,n-1,0)(1,0,n-1,0)(1,1,n-4,2)(0,0,n-1,1))$. Now the possibility to lengthen the code $C_1$ to a 1-perfect code of length $n+2$ is equivalent to the possibility to split the part $C_4$ into two distance-3 codes or, equivalently, to the biparticity of the graph of distances 1 and 2 of $C_4$. In any case, $C_1$ is uniquely embeddable in a twofold 1-perfect code of length $n+2$ with some structural restrictions, where by a…

关于半径1以外的近完备覆盖码

On Nearly-Perfect Covering Codes Beyond Radius One

本文研究二元近完备覆盖码，修正原Van Wee界以纳入最小距离，确定R=2、3的此类码等价于构造的码，且R≥3时此类码数量有限。

q-ary Propelinear Perfect Codes from the Regular Subgroups of the GA(r,q) and Their Ranks

We propose a new method of constructing q-ary propelinear perfect codes. The approach utilizes permutations of the fixed length q-ary vectors that arise from the automorphisms of the regular subgroups of the affine group. For any prime q it is shown that the new class contains an infinite series of q-ary propelinear perfect codes of varying ranks of growing length.

Obtaining binary perfect codes out of tilings

A tiling of the $n$-dimensional Hamming cube gives rise to a perfect code (according to a given metric) if the basic tile is a metric ball. We are concerned with metrics on the $n$-dimensional Hamming cube which are determined by a weight which respects support of vectors (TS-metrics). We consider the known tilings of the Hamming cube and first determine which of them give rise to a perfect code. In the sequence, for those tilings that satisfy this condition, we determine all the TS-metrics that turns it into a perfect code. We also propose the construction of new perfect codes obtained by the…

Diameter Perfect Lee Codes

Lee codes have been intensively studied for more than 40 years. Interest in these codes has been triggered by the Golomb-Welch conjecture on the existence of the perfect error-correcting Lee codes. In this paper we deal with the existence and enumeration of diameter perfect Lee codes. As main results we determine all $q$ for which there exists a linear diameter-4 perfect Lee code of word length $n$ over $Z_{q},$ and prove that for each $n\geq 3$ there are uncountable many diameter-4 perfect Lee codes of word length $n$ over $Z.$ This is in a strict contrast with perfect error-correcting Lee co…

Perfect codes in Doob graphs

We study $1$-perfect codes in Doob graphs $D(m,n)$. We show that such codes that are linear over $GR(4^2)$ exist if and only if $n=(4^{g+d}-1)/3$ and $m=(4^{g+2d}-4^{g+d})/6$ for some integers $g \ge 0$ and $d>0$. We also prove necessary conditions on $(m,n)$ for $1$-perfect codes that are linear over $Z_4$ (we call such codes additive) to exist in $D(m,n)$ graphs; for some of these parameters, we show the existence of codes. For every $m$ and $n$ satisfying $2m+n=(4^t-1)/3$ and $m \le (4^t-5\cdot 2^{t-1}+1)/9$, we prove the existence of $1$-perfect codes in $D(m,n)$, without the restriction t…

关于和秩度量下完美码不存在性的研究

On the non-existence of perfect codes in the sum-rank metric

本文研究和秩度量下线性完美码的存在性，通过分析度量球几何与体积界，给出两块空间的参数约束，并在多块空间中基于最小距离、整除性和码维数建立多类不存在性结果。

论完美对称秩距离码

On perfect symmetric rank-metric codes

本文研究对称秩距离码的覆盖性质，刻画了在类似球填充界中取等号的完美码及若干拟完美码族，并证明存在非平凡完美码。

On the binary codes with parameters of triply-shortened 1-perfect codes

We study properties of binary codes with parameters close to the parameters of 1-perfect codes. An arbitrary binary $(n=2^m-3, 2^{n-m-1}, 4)$ code $C$, i.e., a code with parameters of a triply-shortened extended Hamming code, is a cell of an equitable partition of the $n$-cube into six cells. An arbitrary binary $(n=2^m-4, 2^{n-m}, 3)$ code $D$, i.e., a code with parameters of a triply-shortened Hamming code, is a cell of an equitable family (but not a partition) from six cells. As a corollary, the codes $C$ and $D$ are completely semiregular; i.e., the weight distribution of such a code depen…

Perfect Codes for Uniform Chains Poset Metrics

The class of poset metrics is very large and contains some interesting families of metrics. A family of metrics, based on posets which are formed from disjoint chains which have the same size, is examined. A necessary and sufficient condition, for the existence of perfect single-error-correcting codes for such poset metrics, is proved.

Ranks of propelinear perfect binary codes

It is proven that for any numbers n=2^m-1, m >= 4 and r, such that n - log(n+1)<= r <= n excluding n = r = 63, n = 127, r in {126,127} and n = r = 2047 there exists a propelinear perfect binary code of length n and rank r.

Johnson 方案中完美码的最后七个开放半径

The Last Seven Open Radii for Perfect Codes in the Johnson Scheme

本文证明 Johnson 方案中七个特定半径下不存在非平凡完美码，补充先前工作，完整证明了 Delsarte 猜想。

A concatenation construction for propelinear perfect codes from regular subgroups of GA(r,2)

A code $C$ is called propelinear if there is a subgroup of $Aut(C)$ of order $|C|$ acting transitively on the codewords of $C$. In the paper new propelinear perfect binary codes of any admissible length more than $7$ are obtained by a particular case of the Solov'eva concatenation construction--1981 and the regular subgroups of the general affine group of the vector space over $GF(2)$.

Coordinate transitivity of extended perfect codes and their SQS

We continue the study of the class of binary extended perfect propelinear codes constructed in the previous paper and consider their permutation automorphism (symmetry) groups and Steiner quadruple systems. We show that the automorphism group of the SQS of any such code coincides with the permutation automorphism group of the code. In particular, the SQS of these codes are complete invariants for the isomorphism classes of these codes. We obtain a criterion for the point transitivity of the automorphism group of SQS of proposed codes in terms of GL-equivalence (similar to EA-type equivalence f…

多重1-完美码

Multifold 1-perfect codes

该研究针对q元Hamming图，刻画了多重1-完美码与加性多重1-完美码的全部参数，证明加性多重1-完美码与multispreads相关且对应参数的multispreads恒存在。

Reconstructing Extended Perfect Binary One-Error-Correcting Codes from Their Minimum Distance Graphs

The minimum distance graph of a code has the codewords as vertices and edges exactly when the Hamming distance between two codewords equals the minimum distance of the code. A constructive proof for reconstructibility of an extended perfect binary one-error-correcting code from its minimum distance graph is presented. Consequently, inequivalent such codes have nonisomorphic minimum distance graphs. Moreover, it is shown that the automorphism group of a minimum distance graph is isomorphic to that of the corresponding code.

关于扩展完全码

On extended perfect codes

该研究刻画了汉明图中扩展1-完全码存在的正整数n、r与素数p的全部情形，同时给出汉明图和约翰逊图中2-完全码存在性的新必要条件，推进了完全码存在性问题的研究。

On the Automorphism Groups of the Z2Z4-Linear 1-Perfect and Preparata-Like Codes

We consider the symmetry group of a $Z_2Z_4$-linear code with parameters of a $1$-perfect, extended $1$-perfect, or Preparata-like code. We show that, provided the code length is greater than $16$, this group consists only of symmetries that preserve the $Z_2Z_4$ structure. We find the orders of the symmetry groups of the $Z_2Z_4$-linear (extended) $1$-perfect codes. Keywords: additive codes, $Z_2Z_4$-linear codes, $1$-perfect codes, Preparata-like codes, automorphism group, symmetry group.

均匀加权阿兹特克钻石与塔图的完美t-嵌入

Perfect t-embeddings of uniformly weighted Aztec diamonds and tower graphs

本文通过构造均匀加权阿兹特克钻石的完美t-嵌入，首次证明存在满足arXiv:2109.06272主定理全部条件的模型，并利用塔图的完美t-嵌入将其高度涨落与阿兹特克钻石等同起来。

均匀加权广义塔图的完美t-嵌入

Perfect t-Embeddings of Uniformly Weighted Generalized Tower Graphs

本文研究均匀加权广义塔图的完美t-嵌入序列，证明其满足Berggren-Nicoletti-Russkikh刚性假设，并由此确认高度函数涨落梯度收敛于高斯自由场梯度。

SQS-graphs of extended 1-perfect codes

A binary extended 1-perfect code $\mathcal C$ folds over its kernel via the Steiner quadruple systems associated with its codewords. The resulting folding, proposed as a graph invariant for $\mathcal C$, distinguishes among the 361 nonlinear codes $\mathcal C$ of kernel dimension $κ$ with $9\geqκ\geq 5$ obtained via Solov'eva-Phelps doubling construction. Each of the 361 resulting graphs has most of its nonloop edges expressible in terms of the lexicographically disjoint quarters of the products of the components of two of the ten 1-perfect partitions of length 8 classified by Phelps, and loop…

完美t-嵌入与双周期阿兹特克钻石的八面体方程

Perfect t-embeddings and the octahedron equation of the two-periodic Aztec diamond

本文研究双周期阿兹特克钻石中完美t-嵌入与八面体方程的关系，证明t-嵌入和折纸映射的位置可由八面体方程在平坦初始条件下的解的密度函数之和表示。

Propelinear 1-perfect codes from quadratic functions

Perfect codes obtained by the Vasil'ev--Schönheim construction from a linear base code and quadratic switching functions are transitive and, moreover, propelinear. This gives at least $\exp(cN^2)$ propelinear $1$-perfect codes of length $N$ over an arbitrary finite field, while an upper bound on the number of transitive codes is $\exp(C(N\ln N)^2)$. Keywords: perfect code, propelinear code, transitive code, automorphism group, Boolean function.

Optimum Distance Flag Codes from Spreads via Perfect Matchings in Graphs

In this paper, we study flag codes on the vector space $\mathbb{F}_q^n$, being $q$ a prime power and $\mathbb{F}_q$ the finite field of $q$ elements. More precisely, we focus on flag codes that attain the maximum possible distance (optimum distance flag codes) and can be obtained from a spread of $\mathbb{F}_q^n$. We characterize the set of admissible type vectors for this family of flag codes and also provide a construction of them based on well-known results about perfect matchings in graphs. This construction attains both the maximum distance for its type vector and the largest possible car…

Perfect Codes for Generalized Deletions from Minuscule Elements of Weyl Groups

This paper discusses a connection between insertion/deletion (ID) codes and minuscule elements of Weyl groups.

论Niederreiter-Rosenbloom-Tsfasman度量下完美码的不存在性

On the non-existence of perfect codes in the Niederreiter-Rosenbloom-Tsfasman metric

该文研究NRT度量下完美码的存在性问题，给出完美码存在的参数必要条件，结合与背包问题的关联建立参数对应关系，证明了特定参数下非平凡完美码的不存在性。

The existence of perfect codes in Doob graphs

We solve the problem of existence of perfect codes in the Doob graph. It is shown that 1-perfect codes in the Doob graph D(m,n) exist if and only if 6m+3n+1 is a power of 2; that is, if the size of a 1-ball divides the number of vertices. Keywords: perfect codes, distance-regular graphs, Doob graphs, Eisenstein-Jacobi integers.

On the nonexistence of linear perfect Lee codes

In 1968, Golomb and Welch conjectured that there does not exist perfect Lee code in $\mathbb{Z}^{n}$ with radius $r\ge2$ and dimension $n\ge3$. Besides its own interest in coding theory and discrete geometry, this conjecture is also strongly related to the degree-diameter problems of abelian Cayley graphs. Although there are many papers on this topic, the Golomb-Welch conjecture is far from being solved. In this paper, we prove the nonexistence of linear perfect Lee codes by introducing some new algebraic methods. Using these new methods, we show the nonexistence of linear perfect Lee codes of…

Spectrum of Sizes for Perfect Deletion-Correcting Codes

One peculiarity with deletion-correcting codes is that perfect $t$-deletion-correcting codes of the same length over the same alphabet can have different numbers of codewords, because the balls of radius $t$ with respect to the Levenshte\uın distance may be of different sizes. There is interest, therefore, in determining all possible sizes of a perfect $t$-deletion-correcting code, given the length $n$ and the alphabet size~$q$. In this paper, we determine completely the spectrum of possible sizes for perfect $q$-ary 1-deletion-correcting codes of length three for all $q$, and perfect $q$-ary …

On lifting perfect codes

In this paper we consider completely regular codes, obtained from perfect (Hamming) codes by lifting the ground field. More exactly, for a given perfect code C of length n=(q^m-1)/(q-1) over F_q with a parity check matrix H_m, we define a new code C_{(m,r)} of length n over F_{q^r}, r > 1, with this parity check matrix H_m. The resulting code C_{(m,r)} is completely regular with covering radius R = min{r,m}. We compute the intersection numbers of such codes and, finally, we prove that Hamming codes are the only codes that, after lifting the ground field, result in completely regular codes.

关于完美旗秩度量码

On perfect flag-rank metric codes

本文研究旗秩度量码的组合几何，通过计算小半径球的大小，推导球包界并定义完美码，证明在低维和特定参数下非平凡完美码不存在。

一类完美单删除校正置换码的高效编码与解码算法

Efficient encoding and decoding algorithm for a class of perfect single-deletion-correcting permutation codes

针对删除信道中的完美单删除校正置换码，本文提出不依赖Varshamov-Tenengolts码的独立直接证明，并据此设计了可校正一次删除的高效编码与解码算法。

2-近完美Lee码与阿贝尔拉马努金图：一种新构造与关系

$2$-quasi-perfect Lee codes and abelian Ramanujan graphs: a new construction and relationship

本文提出一种新的无限族2-近完美p元Lee码，通过生成集H_q构造，并将其与已知的阿贝尔拉马努金图联系起来，提供统一的理论框架。

q元汉明空间中作为二次偏差精确极小化元的完备码

Perfect codes as exact minimizers of quadratic discrepancy in q-ary Hamming spaces

该研究证明q元汉明空间中，当固定长度和基数存在完备码时，完备码是二次偏差的精确极小化元，其存在性等价于显式变分目标的达成。

Linear and group perfect codes over skew fields and quasi skew fields

In this paper, we propose a general construction of linear perfect codes over infinite skew fields and quasi skew fields with right (left) unity. A complete classification of such codes over associative skew fields is given. Since the cardinality of the considered skew fields is infinite, the constructed codes have an infinite length. In the previous work, we considered codes over infinite countable fields, the length of which was also countable. We now remove this restriction and consider that the cardinality of the skew field and the length of the codes can be arbitrary (not necessarily coun…

Quasi-perfect Lee Codes of Radius 2 and Arbitrarily Large Dimension

A construction of 2-quasi-perfect Lee codes is given over the space $\mathbb Z_p^n$ for $p$ prime, $p\equiv \pm 5\pmod{12}$ and $n=2[\frac{p}{4}]$. It is known that there are infinitely many such primes. Golomb and Welch conjectured that perfect codes for the Lee-metric do not exist for dimension $n\geq 3$ and radius $r\geq 2$. This conjecture was proved to be true for large radii as well as for low dimensions. The codes found are very close to be perfect, which exhibits the hardness of the conjecture. A series of computations show that related graphs are Ramanujan, which could provide further…

On weight distributions of perfect colorings and completely regular codes

A vertex coloring of a graph is called "perfect" if for any two colors $a$ and $b$, the number of the color-$b$ neighbors of a color-$a$ vertex $x$ does not depend on the choice of $x$, that is, depends only on $a$ and $b$ (the corresponding partition of the vertex set is known as "equitable"). A set of vertices is called "completely regular" if the coloring according to the distance from this set is perfect. By the "weight distribution" of some coloring with respect to some set we mean the information about the number of vertices of every color at every distance from the set. We study the wei…

完美t-嵌入与菱形密铺

Perfect t-embeddings and Lozenge Tilings

本文首次为六角格正六边形构造完美t-嵌入，利用逆Kasteleyn矩阵与对称性推导精确公式，证明折纸映射收敛到Minkowski空间极大曲面，并给出高度涨落收敛到高斯自由场的新证明。

弱度量关联方案中的完美码

Perfect codes in weakly metric association schemes

本文结合Lloyd定理与Schwartz-Zippel引理，通过整数划分的渐近枚举，证明了Lee度量、NRT度量、混合Hamming度量和和秩距离中完美码的不存在性，并引入多项式弱度量关联方案的概念。

关于$q$元缩短$1$完美类码

On $q$-ary shortened-$1$-perfect-like codes

研究$q$元缩短Hamming码的最优性，推广了多重填充界，并证明了从$n=20$起存在无法由缩短$1$完美码获得的$4$元缩短$1$完美类码。

On homogeneous nontransitive binary perfect code

Studying binary perfect codes we show the existence of homogeneous nontransitive codes. Thus, as far as perfect codes are concerned, the propelinear codes are strictly contained in transitive codes, wheresas homogeneous codes form a strict subclass of transitive codes. In the work we deduce a necessary and sufficient condition for transitivity of perfect binary codes of rank one more than that of Hamming code. The paper is in Russian.

Embedding large subgraphs into dense graphs

What conditions ensure that a graph G contains some given spanning subgraph H? The most famous examples of results of this kind are probably Dirac's theorem on Hamilton cycles and Tutte's theorem on perfect matchings. Perfect matchings are generalized by perfect F-packings, where instead of covering all the vertices of G by disjoint edges, we want to cover G by disjoint copies of a (small) graph F. It is unlikely that there is a characterization of all graphs G which contain a perfect F-packing, so as in the case of Dirac's theorem it makes sense to study conditions on the minimum degree of G …

Characterizing subgroup perfect codes by 2-subgroups

A perfect code in a graph $Γ$ is a subset $C$ of $V(Γ)$ such that no two vertices in $C$ are adjacent and every vertex in $V(Γ)\setminus C$ is adjacent to exactly one vertex in $C$. Let $G$ be a finite group and $C$ a subset of $G$. Then $C$ is said to be a perfect code of $G$ if there exists a Cayley graph of $G$ admiting $C$ as a perfect code. It is proved that a subgroup $H$ of $G$ is a perfect code of $G$ if and only if a Sylow $2$-subgroup of $H$ is a perfect code of $G$. This result provides a way to simplify the study of subgroup perfect codes of general groups to the study of subgroup …

在广义彼得森图中对完美码和全完美码的分类

Classification of perfect and total perfect codes in generalized Petersen graphs

研究了广义彼得森图中完美码和全完美码的分类问题，通过分析图的结构特征，确定了这两种码的分类标准和性质。

对称群$S_n$在Cayley和图中的子群完美码

Subgroup perfect codes of $S_n$ in Cayley sum graphs

该研究证明对称群$S_n$不存在真子群完美码，并以此为基础给出了交错群$A_n$子群完美码的完整刻画，推进了Cayley和图中群论与编码理论交叉领域的研究。

A note on some embedding problems for oriented graphs

We conjecture that every oriented graph $G$ on $n$ vertices with $δ^+ (G) , δ^- (G) \geq 5n/12$ contains the square of a Hamilton cycle. We also give a conjectural bound on the minimum semidegree which ensures a perfect packing of transitive triangles in an oriented graph. A link between Ramsey numbers and perfect packings of transitive tournaments is also considered.

广义 Cayley 图与完美码

Generalized Cayley graphs and perfect code

该研究将以往关于 Cayley 图及 Cayley 和图中完美码的关注扩展到广义 Cayley 图，探讨其中完美码的存在与性质。

On the non-existence of extended perfect codes and some perfect colorings

In this paper we obtain the necessary condition for the existence of perfect $k$-colorings (equitable $k$-partitions) in Hamming graphs $H(n,q)$, where $q=2,3,4$ and Doob graphs $D(m,n)$. As an application, we prove the non-existence of extended perfect codes in $H(n,q)$, where $q=3,4$, $n>q+2$, and in $D(m,n)$, where $2m+n>6$.

Subgroup perfect codes in Cayley graphs

Let $Γ$ be a graph with vertex set $V(Γ)$. A subset $C$ of $V(Γ)$ is called a perfect code in $Γ$ if $C$ is an independent set of $Γ$ and every vertex in $V(Γ)\setminus C$ is adjacent to exactly one vertex in $C$. A subset $C$ of a group $G$ is called a perfect code of $G$ if there exists a Cayley graph of $G$ which admits $C$ as a perfect code. A group $G$ is said to be code-perfect if every proper subgroup of $G$ is a perfect code of $G$. In this paper we prove that a group is code-perfect if and only if it has no elements of order $4$. We also prove that a proper subgroup $H$ of an abelian …