On Teh's construction of orders in Abelian groups

1972 ◽  
Vol 71 (3) ◽  
pp. 433-436
Author(s):  
Donald P. Minassian
Keyword(s):  
Direct Product ◽  
Abelian Groups ◽  
Rational Numbers ◽  
Embedding Theorem

AbstractA claim of H. H. Teh on Archimedean full orders ((2), ‘only if’ of Theorem 2, p. 480) fails. His statement (p. 478, line 5) that the direct product of n copies of the additive rational numbers admits no full order of Archimedean rank more than n is proved without Hahn's embedding theorem. A few other remarks are made.

RATIONAL RINGS RELATED TO WEAKLY TRANSITIVE TORSION-FREE ABELIAN GROUPS

2009 ◽  
Vol 08 (05) ◽  
pp. 723-732 ◽  
Author(s):  
CHRIS MEEHAN ◽  
LUTZ STRÜNGMANN
Keyword(s):  
Abelian Groups ◽  
Rational Numbers ◽  
Rational Group ◽  
Free Abelian Groups ◽  
Torsion Free

We study subgroups R of the rational numbers ℚ having the property that for every pair of integers m, n such that gcd(m, n) = 1 and gcd(m, p) = gcd(n, p) = 1 whenever p is in the spectrum of R there is a unit u of R and an element r ∈ R such that un + rm = 1. These rings are closely related to weakly transitive separable groups. We prove that the property is dependent on the spectrum of the rational group in question and that the spectrum may be very complicated.

On 2-Groups as Galois Groups

1995 ◽  
Vol 47 (6) ◽  
pp. 1253-1273 ◽  
Author(s):  
Arne Ledet
Keyword(s):  
Galois Group ◽  
Direct Product ◽  
Galois Extension ◽  
Quaternion Algebra ◽  
Abelian Groups ◽  
Galois Groups ◽  
Embedding Problem ◽  
Brauer Group ◽  
Characteristic 2 ◽  
Cyclic Kernel

AbstractLet L/K be a finite Galois extension in characteristic ≠ 2, and consider a non-split Galois theoretical embedding problem over L/K with cyclic kernel of order 2. In this paper, we prove that if the Galois group of L/K is the direct product of two subgroups, the obstruction to solving the embedding problem can be expressed as the product of the obstructions to related embedding problems over the corresponding subextensions of L/K and certain quaternion algebra factors in the Brauer group of K. In connection with this, the obstructions to realising non-abelian groups of order 8 and 16 as Galois groups over fields of characteristic ≠ 2 are calculated, and these obstructions are used to consider automatic realisations between groups of order 4, 8 and 16.

Abelian Groups with a Vanishing Homology Group

1969 ◽  
Vol 21 ◽  
pp. 406-409 ◽  
Author(s):  
James A. Schafer
Keyword(s):  
Homology Group ◽  
Abelian Groups ◽  
Additive Group ◽  
Rational Numbers ◽  
Complete Characterization ◽  
Integral Homology ◽  
Positive Dimension ◽  
Homology Groups

In this paper, we wish to characterize those abelian groups whose integral homology groups vanish in some positive dimension. We obtain a complete characterization provided the dimension in which the homology vanishes is odd; in fact, we prove that the only abelian groups which possess a vanishing homology group in an odd dimension are, up to isomorphism, subgroups of Qn, where Q denotes the additive group of rational numbers. The case of vanishing in an even dimension is much more complicated. We exhibit a class of groups whose homology vanishes in even dimensions and is otherwise very nice, namely the subgroups of Q/Z, and then show that unless we impose further restrictions, there exist abelian groups which possess the homology of subgroups of Q/Z without being isomorphic to a subgroup of Q/Z.

scholarly journals Lattice embeddings of abelian prime power groups

1997 ◽  
Vol 62 (2) ◽  
pp. 259-278 ◽  
Author(s):  
Roland Schmidt
Keyword(s):  
Direct Product ◽  
Prime Power ◽  
Abelian Groups ◽  
Subgroup Lattice ◽  
Prime Power Order

AbstractWe solve the following problem which was posed by Barnes in 1962. For which abelian groups G and H of the same prime power order is it possible to embed the subgroup lattice of G in that of H? It follows from Barnes' results and a theorem of Herrmann and Huhn that if there exists such an embedding and G contains three independent elements of order p2, then G and H are isomorphic. This reduces the problem to the case that G is the direct product of cyclic p-groups only two of which have order larger than p. We determine all groups H for which the desired embedding exists.

Theories of modules closed under direct products

1992 ◽  
Vol 57 (2) ◽  
pp. 515-521
Author(s):  
Roger Villemaire
Keyword(s):  
Direct Product ◽  
Abelian Groups ◽  
Complete Theory ◽  
Direct Products ◽  
Horn Theory

AbstractWe generalize to theories of modules (complete or not) a result of U. Felgner stating that a complete theory of abelian groups is a Horn theory if and only if it is closed under products. To prove this we show that a reduced product of modules ΠFMi (i ϵ I) is elementarily equivalent to a direct product of ultraproducts of the modules Mi(i ϵ I).

scholarly journals On commuting elements and embeddings of graph groups and monoids

2009 ◽  
Vol 52 (1) ◽  
pp. 155-170 ◽  
Author(s):  
Mark Kambites
Keyword(s):  
Direct Product ◽  
Abelian Groups ◽  
Artin Groups ◽  
Right Angled Artin Groups ◽  
Graph Groups

AbstractWe study commutation properties of subsets of right-angled Artin groups and trace monoids. We show that if Γ is any graph not containing a four-cycle without chords, then the group G(Γ) does not contain four elements whose commutation graph is a four-cycle; a consequence is that G(Γ) does not have a subgroup isomorphic to a direct product of non-abelian groups. We also obtain corresponding and more general results in the monoid case.

scholarly journals The Hahn Embedding Theorem for a Class of Residuated Semigroups

Studia Logica ◽  
2020 ◽  
Vol 108 (6) ◽  
pp. 1161-1206
Author(s):  
Sándor Jenei
Keyword(s):  
Representation Theorem ◽  
Abelian Groups ◽  
Embedding Theorem ◽  
Residuated Lattices ◽  
Lexicographic Product ◽  
Product Construction

AbstractHahn’s embedding theorem asserts that linearly ordered abelian groups embed in some lexicographic product of real groups. Hahn’s theorem is generalized to a class of residuated semigroups in this paper, namely, to odd involutive commutative residuated chains which possess only finitely many idempotent elements. To this end, the partial lexicographic product construction is introduced to construct new odd involutive commutative residuated lattices from a pair of odd involutive commutative residuated lattices, and a representation theorem for odd involutive commutative residuated chains which possess only finitely many idempotent elements, by means of linearly ordered abelian groups and the partial lexicographic product construction is presented.

scholarly journals Regulating hulls of almost completely decomposable groups

1993 ◽  
Vol 54 (2) ◽  
pp. 143-155 ◽  
Author(s):  
A. Mader ◽  
C. Vinsonhaler
Keyword(s):  
Finite Index ◽  
Finite Rank ◽  
Abelian Groups ◽  
Additive Group ◽  
Rational Numbers ◽  
Direct Sum ◽  
Free Abelian Groups ◽  
Decomposable Groups ◽  
The Relationship ◽  
Torsion Free

AbstractThis note investigates torsion-free abelian groups G of finite rank which embed, as subgroups of finite index, in a finite direct sum C of subgroups of the additive group of rational numbers. Specifically, we examine the relationship between G and C when the index of G in C is minimal. Some properties of Warfield duality are developed and used (in the case that G is locally free) to relate our results to earlier ones by Burkhardt and Lady.

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