Syndrome spectrums of error orbits in RS-codes

This article is devoted to the research of the properties of syndromes of errors in Reed-Solomon codes. RS-codes are built on non-binary alphabets. So, unlike BCH-codes, RS-codes contain an extremely large variety of correctable errors. To correct these errors, a systematic application of automorphisms of codes is proposed. Characteristic automorphisms of RS-codes are cyclic and affine substitutions forming cyclic groups Г and A whose orders coincide with the code length. Cyclic and affine substitutions commute with each other and generate a joint АГ group, what is the product of subgroups A and Г. These three groups act on the space of error vectors of RS-codes, breaking this space into three types of error orbits. As a rule, these orbits are complete and contain the maximum possible number of errors. Syndromes are the main indicator of the presence of errors in each message received by the information system, a means of accurately identifying these errors. The specificity of syndromes of double errors in RS-codes is investigated. Determined that syndrome spectrums of error orbits are also complete in most cases. Proved that the structure of the syndrome spectrums copies the structure of the orbits themselves, which in turn copy the structure of groups of code automorphisms. The results obtained are a significant contribution to the construction of the theory of syndrome norms for RS-codes.

Solvable groups whose character degree graphs generalize squares

Let G be a solvable group, and let {\Delta(G)} be the character degree graph of G. In this paper, we generalize the definition of a square graph to graphs that are block squares. We show that if G is a solvable group so that {\Delta(G)} is a block square, then G has at most two normal nonabelian Sylow subgroups. Furthermore, we show that when G is a solvable group that has two normal nonabelian Sylow subgroups and {\Delta(G)} is block square, then G is a direct product of subgroups having disconnected character degree graphs.

VAGUE GROUPS AND Ω-VAGUE GROUPS

Given a group G, we show how one can define a vague group structure on G via a chain of subgroups of G. We discuss how a group homomorphism f from a vague group X onto a group Y induces a vague group structure on Y with f satisfying the vague homomorphism property. The notion of Ω-vague groups is introduced, where Ω is a fuzzy subset. The direct product G1 × G2 of two vague groups and the internal vague direct product of subgroups of a vague group is introduced.

A note on the product of F-subgroups in a finite group

Saturated formations are closed under the product of subgroups which are connected by certain permutability properties.

A Generalization of Lyndon's Theorem on the Cohomology of One-Relator Groups

In this paper we generalize a theorem of Lyndon's [7], which states that a one-relator group G = F/(r) (F is free and r Ç F) has cohomological dimension cd (F/(r)) ≧ 2 if and only if the relator r is not a proper power in F. His proof relies on the Identity Theorem and recently he has shown [8] how a generalized version of this theorem and a generalized version of the Freiheitsatz can be simultaneously obtained by the methods of combinatorial geometry. These generalizations refer to a situation where the free group F is replaced by a free product of subgroups of the additive group of real numbers.

Wreath Products of Nonoverlapping Lattice Ordered Groups

One of the fundamental tools in the theory of totally ordered groups is Hahn’s Theorem (a detailed discussion may be found in Fuchs [3]), which asserts, roughly, that every abelian totally ordered group can be embedded in a lexicographically ordered (unrestricted) direct sum of copies of the ordered group of real numbers. Almost any general question regarding the structure of abelian totally ordered groups can be answered by reference to Hahn’s theorem. For the class of nonabelian totally ordered groups, a theorem which parallels Hahn’s Theorem is given in [5], and states that each totally ordered group can be o-embedded in an ordered wreath product of subgroups of the real numbers. In order to extend this theorem to include an “if and only if” statement, one must consider lattice ordered groups, as an ordered wreath product of subgroups of the real numbers is, in general, not totally-ordered, but lattice ordered.