On the Binary Self-Dual Codes with an Automorphism of Order 2

Methods to design binary self-dual codes with an automorphism of order two without fixed points are presented. New extremal self-dual [40,20,8], [42,21,8],[44,22,8] and [64,32,12] codes with previously not known weight enumerators are constructed.     

Self-Dual [24, 12, 8] Quaternary Codes with a Nontrivial Automorphism of Order 3

All (Hermitian) self-dual [24, 12, 8] quaternary codes which have a non-trivial automorphism of order 3 are obtained up to equivalence. There exist exactly 205 inequivalent such codes. The codes under consideration are optimal, self-dual, and have the highest possible minimum distance for this length.     

New optimal [52, 26, 10] self-dual codes

We classify up to equivalence all optimal binary self-dual [52, 26, 10] codes having an automorphism of order 3 with 10 fixed points. We achieve this using a method for constructing self-dual codes via an automorphism of odd prime order. We study also codes with an automorphism of order 3 with 4 fixed points. Some of the constructed codes have new values β = 8, 9, and 12 for the parameter in their weight enumerator.     

Extremal Self-Dual [50, 25, 10] Codes with Automorphisms of Order 3 and Quasi-Symmetric 2-(49, 9,6) Designs

Five non-isomorphic quasi-symmetric 2-(49, 9, 6) designs are known. They arise from extremal self-dual [50, 25, 10] codes with a certain weight enumerator. Four of them have an automorphism of order 3 fixing two points. In this paper, it is shown that there are exactly 48 inequivalent extremal self-dual [50, 25, 10] code with this weight enumerator and an automorphism of order 3 fixing two points. 44 new quasi-symmetric 2-(49, 9, 6) designs with an automorphism of order 3 are constructed from these codes.     

An Enumeration of Binary Self-Dual Codes of Length 32

A binary self-dual code of length 2k is a (2k, k) binary linear code C with the property that every pair of codewords in C are orthogonal. Two self-dual codes, C ₁ and C ₂, are equivalent if and only if there is a permutation of the coordinates of C ₁ that takes C ₁ into C ₂. The automorphism group of a binary code C is the set of all permutations of the coordinates of C that takes C into itself.The main topic of this paper is the enumeration of inequivalent binary self-dual codes. We have developed algorithms that will take lists of inequivalent small codes and produce lists of larger codes where each inequivalent code occurs only a few times. We have defined a canonical form for codes that allowed us to eliminate the overenumeration. So we have lists of inequivalent binary self-dual codes of length up to 32. The enumeration of the length 32 codes is new. Our algorithm also finds the size of the automorphism group so that we can compute the number of distinct binary self-dual codes for a specific length. This number can also be found by counting and matches our total.     

Structure Theorems for Group Ring Codes with an Application to Self-Dual Codes

Using ideas from the cohomology of finite groups, an isomorphism is established between a group ring and the direct sum of twisted group rings. This gives a decomposition of a group ring code into twisted group ring codes. In the abelian case the twisted group ring codes are (multi-dimensional) constacyclic codes. We use the decomposition to prove that, with respect to the Euclidean inner product, there are no self-dual group ring codes when the group is the direct product of a 2-group and a group of odd order, and the ring is a field of odd characteristic or a certain modular ring. In particular, there are no self-dual abelian codes over the rings indicated. Extensions of these results to non-Euclidean inner products are briefly discussed.     

Groups Admitting an Automorphism of Prime Order with Finite Centralizer

We consider a group G with an automorphism of finite, usually prime, order. If G has finite Hirsch number, and also if G satisfies various stronger rank restrictions, we study the consequences and equivalent hypotheses of having only finitely many fixed-points. In particular we prove that if a group G with finite Hirsch number ${\mathfrak{h}}$ admits an automorphism ${\varphi}$ of prime order p such that ${\vert C_{G}(\varphi) \vert = n < \infty,}$ then G has a subgroup of finite index bounded in terms of p, n and ${\mathfrak{h}}$ that is nilpotent of p-bounded class.     

On Solvability of Lie Rings with an Automorphism of Finite Order

A new criterion for a Lie ring with a semisimple automorphism of finite order to be solvable is proved. It generalizes the effective version of Winter's criterion obtained earlier by Khukhro and Shumyatsky and by Bergen and Grzeszczuk in replacing the ideal generated by a certain set by the subring generated by this set. The proof is inspired by the original theorem of Kreknin on solvability of Lie rings with regular automorphisms of finite order and is conducted mostly in terms of Lie rings graded by a finite cyclic group.     

有一个稳定子群是F-群的素数阶自同构的有限π-群

本文引入了 ｃ－自同构的概念,在［１］和 ［２］的基础上得到了 Ｔｈｏｍｐｓｏｎ定理的三个推广．     

On the Automorphisms of Order 2 with Fixed Points for the Extremal Self-Dual Codes of Length 24"m

It is shown that an extremal self-dual code of length 24">m may have an automorphism of order 2 with fixed points only for ">m = 1,3, or 5. We prove that no self-dual [72, 36, 16] code has such an automorphism in its automorphism group.     

The Nonexistence of Ternary [38, 6, 23] Codes

It has been shown by Bogdanova and Boukliev [1] that there exist a ternary [38,5,24] code and a ternary [37,5,23] code. But it is unknown whether or not there exist a ternary [39,6,24] code and a ternary [38,6,23] code. The purpose of this paper is to prove that (1) there is no ternary [39,6,24] code and (2) there is no ternary [38,6,23] code using the nonexistence of ternary [39,6,24] codes. Since it is known (cf. Brouwer and Sloane [2] and Hamada and Watamori [14]) that (i) n₃(6,23) = 38> or 39 and d₃(38,6) = 22 or 23 and (ii) n₃(6,24) = 39 or 40 and d₃(39,6) = 23 or 24, this implies that n₃(6,23) = 39, d₃(38,6) = 22, n₃(6,24) = 40 and d₃(39,6) = 23, where n3<>(k,d) and d<>3(n,k) denote the smallest value of n and the largest value of d, respectively, for which there exists an [n,k,d] code over the Galois field GF(3).     

The Nonexistence of Ternary [50,5,32] Codes

It is unknown (cf. Hill and Newton [8] or Hamada [3]) whether or not there exists a ternary [50,5,32] code meeting the Griesmer bound. The purpose of this paper is to prove the nonexistence of ternary [50,5,32] codes. Since there exists a ternary [51,5,32] code, this implies that n3(5,32) = 51, where n3(k,d) denotes the smallest value of n for which there exists a ternary [n,k,d] code.     

含p^n—2阶元的P^n阶p—群的自同构群

一个有限p-群G称为一个LA-群,如果当G是非循环的且|G|>p~2时有|G|/|Aut(G)|,本文证明了一个含有p~(n-2)阶元的p~n阶p-群是一LA-群。     

The Automorphism Groups of BCH Codes and of Some Affine-Invariant Codes Over Extension Fields

Affine-invariant codes are extended cyclic codes of length p ^m invariant under the affine-group acting on . This class of codes includes codes of great interest such as extended narrow-sense BCH codes. In recent papers, we classified the automorphism groups of affine-invariant codes berg, bech1. We derive here new results, especially when the alphabet field is an extension field, by expanding our previous tools. In particular we complete our results on BCH codes, giving the automorphism groups of extended narrow-sense BCH codes defined over any extension field.     

Finite Groups of Bounded Rank with an Almost Regular Automorphism of Prime Order

We prove that if a finite group G of rank r admits an automorphism of prime order having exactly m fixed points, then G has a -invariant subgroup of (r,m)-bounded index which is nilpotent of r-bounded class (Theorem 1). Thus, for automorphisms of prime order the previous results of Shalev, Khukhro, and Jaikin-Zapirain are strengthened. The proof rests, in particular, on a result about regular automorphisms of Lie rings (Theorem 3). The general case reduces modulo available results to the case of finite p-groups. For reduction to Lie rings powerful p-groups are also used. For them a useful fact is proved which allows us to glue together nilpotency classes of factors of certain normal series (Theorem 2).     

某些家族p6阶群的自同构群的阶

本文确定了p6阶群的Φ27,Φ2s,Φ29,Φ30四个家族的所有群的自同构群的阶,这里p是奇素数.     

2pq阶群的自同构群

继续「１～２」等的工作,给出了２ｐｑ阶群Ｇ的自同构群ＡｕｔＧ的准确构造。     

具有4pq阶自同构群的有限群

本文讨论了自同构群阶为4pq(p,q为不同奇素数)的有限群,得出了它们的构造.     

The Asymptotic Number of Inequivalent Binary Codes and Nonisomorphic Binary Matroids

The asymptotic value as n→∞ of the number b(n) of inequivalent binary n-codes is determined. It was long known that b(n) also gives the number of nonisomorphic binary n-matroids.     

Finitely Generated Torsion-free Nilp otent Groups Admitting an Automorphism of Prime Order

Let G be a finitely generated torsion-free nilpotent group and α an automorphism of prime order p of G. If the map φ : G-→ G defined by gφ= [g, α]is surjective, then the nilpotent class of G is at most h(p), where h(p) is a function depending only on p. In particular, if α3= 1, then the nilpotent class of G is at most2.