The automorphism group of the semigroup of finite complexes of a rank one torsion free abelian group

1982 ◽  
Vol 39 (5) ◽  
pp. 385-393
Author(s):  
Richard D. Byrd ◽  
Justin T. Lloyd ◽  
James W. Stepp
Keyword(s):  
Abelian Group ◽  
Automorphism Group ◽  
Free Abelian Group ◽  
Torsion Free Abelian Group ◽  
Rank One ◽  
Torsion Free

On Finite Essential Extensions of Torsion Free Abelian Groups

1996 ◽  
Vol 48 (5) ◽  
pp. 918-929 ◽  
Author(s):  
K. Benabdallah ◽  
M. A. Ouldbeddi
Keyword(s):  
Abelian Group ◽  
Finite Index ◽  
Free Abelian Group ◽  
Torsion Free Abelian Group ◽  
Direct Sum ◽  
Rank One ◽  
Free Abelian Groups ◽  
Decomposable Groups ◽  
Essential Extensions ◽  
Torsion Free

AbstractLet A be a torsion free abelian group. We say that a group K is a finite essential extension of A if K contains an essential subgroup of finite index which is isomorphic to A. Such K admits a representation as (A ℤ xkx)/ℤky where y = Nx + a for some k x k matrix N over Z and α ∈ Ak satisfying certain conditions of relative primeness and ℤk = {(α1,..., αk) : αi, ∈ ℤ}. The concept of absolute width of an f.e.e. K of A is defined and it is shown to be strictly smaller than the rank of A. A kind of basis substitution with respect to Smith diagonal matrices is shown to hold for homogeneous completely decomposable groups. This result together with general properties of our representations are used to provide a self contained proof that acd groups with two critical types are direct sum of groups of rank one and two.

A Theorem on Pure Submodules

1960 ◽  
Vol 12 ◽  
pp. 483-487
Author(s):  
George Kolettis
Keyword(s):  
Free Abelian Group ◽  
Chain Condition ◽  
Affirmative Answer ◽  
Principal Ideal Ring ◽  
Torsion Free Abelian Group ◽  
Direct Sum ◽  
Rank One ◽  
Pure Submodules ◽  
Torsion Free ◽  
Countable Case

In (1) Baer studied the following problem: If a torsion-free abelian group G is a direct sum of groups of rank one, is every direct summand of G also a direct sum of groups of rank one? For groups satisfying a certain chain condition, Baer gave a solution. Kulikov, in (3), supplied an affirmative answer, assuming only that G is countable. In a recent paper (2), Kaplansky settles the issue by reducing the general case to the countable case where Kulikov's solution is applicable. As usual, the result extends to modules over a principal ideal ring R (commutative with unit, no divisors of zero, every ideal principal).The object of this paper is to carry out a similar investigation for pure submodules, a somewhat larger class of submodules than the class of direct summands. We ask: if the torsion-free i?-module M is a direct sum of modules of rank one, is every pure submodule N of M also a direct sum of modules of rank one? Unlike the situation for direct summands, here the answer depends heavily on the ring R.

scholarly journals Neutrosophic Triplets in Neutrosophic Rings

Mathematics ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 563 ◽  
Author(s):  
Vasantha Kandasamy W. B. ◽  
Ilanthenral Kandasamy ◽  
Florentin Smarandache
Keyword(s):  
Abelian Group ◽  
Free Abelian Group ◽  
Torsion Free Abelian Group ◽  
Ring Of Integers ◽  
Torsion Free

The neutrosophic triplets in neutrosophic rings ⟨ Q ∪ I ⟩ and ⟨ R ∪ I ⟩ are investigated in this paper. However, non-trivial neutrosophic triplets are not found in ⟨ Z ∪ I ⟩ . In the neutrosophic ring of integers Z ∖ { 0 , 1 } , no element has inverse in Z. It is proved that these rings can contain only three types of neutrosophic triplets, these collections are distinct, and these collections form a torsion free abelian group as triplets under component wise product. However, these collections are not even closed under component wise addition.

scholarly journals Type radicals and quasi-decompositions of torsion-free abelian groups

1992 ◽  
Vol 52 (2) ◽  
pp. 219-236 ◽  
Author(s):  
Oteo Mutzbauer
Keyword(s):  
Abelian Group ◽  
Finite Rank ◽  
Free Abelian Group ◽  
Abelian Groups ◽  
Torsion Free Abelian Group ◽  
Direct Sum ◽  
Free Abelian Groups ◽  
Torsion Free

AbstractA composition sequence for a torsion-free abelian group A is an increasing sequenceof pure subgroups with rank 1 quotients and union A. Properties of A can be described by the sequence of types of these quotients. For example, if A is uniform, that is all the types in some sequence are equal, then A is complete decomposable if it is homogeneous. If A has finite rank and all permutations ofone of its type sequences can be realized, then A is quasi-isomorphic to a direct sum of uniform groups.

A THEOREM ON MATRIX GROUPS

2008 ◽  
Vol 18 (01) ◽  
pp. 165-180
Author(s):  
A. I. PAPISTAS
Keyword(s):  
Abelian Group ◽  
Finite Subset ◽  
Free Abelian Group ◽  
Principal Ideal Domain ◽  
Matrix Groups ◽  
Generating Set ◽  
Torsion Free Abelian Group ◽  
Group Of Units ◽  
Multiplicative Monoid ◽  
Torsion Free

Let K be a principal ideal domain, and An, with n ≥ 3, be a finitely generated torsion-free abelian group of rank n. Let Ω be a finite subset of KAn\{0} and U(KAn) the group of units of KAn. For a multiplicative monoid P generated by U(KAn) and Ω, we prove that any generating set for [Formula: see text] contains infinitely many elements not in [Formula: see text]. Furthermore, we present a way of constructing elements of [Formula: see text] not in [Formula: see text] for n ≥ 3. In the case where K is not a field the aforementioned results hold for n ≥ 2.

Torsion-free abelian groups with optimal Scott families

2018 ◽  
Vol 18 (01) ◽  
pp. 1850002
Author(s):  
Alexander G. Melnikov
Keyword(s):  
Abelian Group ◽  
Free Abelian Group ◽  
Abelian Groups ◽  
Symbolic Logic ◽  
Technical Result ◽  
Torsion Free Abelian Group ◽  
Scott Family ◽  
Free Abelian Groups ◽  
Torsion Free ◽  
Labeled Tree

We prove that for any computable successor ordinal of the form [Formula: see text] [Formula: see text] limit and [Formula: see text] there exists computable torsion-free abelian group [Formula: see text]TFAG[Formula: see text] that is relatively [Formula: see text] -categorical and not [Formula: see text] -categorical. Equivalently, for any such [Formula: see text] there exists a computable TFAG whose initial segments are uniformly described by [Formula: see text] infinitary computable formulae up to automorphism (i.e. it has a c.e. uniformly [Formula: see text]-Scott family), and there is no syntactically simpler (c.e.) family of formulae that would capture these orbits. As far as we know, the problem of finding such optimal examples of (relatively) [Formula: see text]-categorical TFAGs for arbitrarily large [Formula: see text] was first raised by Goncharov at least 10 years ago, but it has resisted solution (see e.g. Problem 7.1 in survey [Computable abelian groups, Bull. Symbolic Logic 20(3) (2014) 315–356]). As a byproduct of the proof, we introduce an effective functor that transforms a [Formula: see text]-computable worthy labeled tree (to be defined) into a computable TFAG. We expect that this technical result will find further applications not necessarily related to categoricity questions.

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