Some Recent Results and Open Problems on Sets of Lengths of Krull MonoidsMonoid Krull monoid with Finite Class Group

2016 ◽  
pp. 323-352 ◽  
Author(s):  
W. A. Schmid
Keyword(s):  
Class Group ◽  
Open Problems ◽  
Sets Of Lengths ◽  
Krull Monoid

scholarly journals Factorizations in Bounded Hereditary Noetherian Prime Rings

2018 ◽  
Vol 62 (2) ◽  
pp. 395-442 ◽  
Author(s):  
Daniel Smertnig
Keyword(s):  
Class Group ◽  
Structure Theory ◽  
Projective Modules ◽  
Ideal Class ◽  
Ideal Class Group ◽  
Prime Rings ◽  
Sets Of Lengths ◽  
Irreducible Elements ◽  
Transfer Homomorphism ◽  
Zero Sum

AbstractIf H is a monoid and a = u1 ··· uk ∈ H with atoms (irreducible elements) u1, … , uk, then k is a length of a, the set of lengths of a is denoted by Ⅼ(a), and ℒ(H) = {Ⅼ(a) | a ∈ H} is the system of sets of lengths of H. Let R be a hereditary Noetherian prime (HNP) ring. Then every element of the monoid of non-zero-divisors R• can be written as a product of atoms. We show that if R is bounded and every stably free right R-ideal is free, then there exists a transfer homomorphism from R• to the monoid B of zero-sum sequences over a subset Gmax(R) of the ideal class group G(R). This implies that the systems of sets of lengths, together with further arithmetical invariants, of the monoids R• and B coincide. It is well known that commutative Dedekind domains allow transfer homomorphisms to monoids of zero-sum sequences, and the arithmetic of the latter has been the object of much research. Our approach is based on the structure theory of finitely generated projective modules over HNP rings, as established in the recent monograph by Levy and Robson. We complement our results by giving an example of a non-bounded HNP ring in which every stably free right R-ideal is free but which does not allow a transfer homomorphism to a monoid of zero-sum sequences over any subset of its ideal class group.

HIGHER-ORDER CLASS GROUPS AND BLOCK MONOIDS OF KRULL MONOIDS WITH TORSION CLASS GROUP

2010 ◽  
Vol 09 (03) ◽  
pp. 433-464 ◽  
Author(s):  
WOLFGANG A. SCHMID
Keyword(s):  
Class Group ◽  
Point Of View ◽  
Torsion Class ◽  
Class Groups ◽  
Detailed Understanding ◽  
Krull Monoids ◽  
Krull Monoid ◽  
Zero Sum ◽  
Block Monoids ◽  
Block Monoid

Extensions of the notion of a class group and a block monoid associated to a Krull monoid with torsion class group are introduced and investigated. Instead of assigning to a Krull monoid only one abelian group (the class group) and one monoid of zero-sum sequences (the block monoid), we assign to it a recursively defined family of abelian groups, the first being the class group, and do alike for the block monoid. These investigations are motivated by the aim of gaining a more detailed understanding of the arithmetic of Krull monoids, including Dedekind and Krull domains, both from a technical and conceptual point of view. To illustrate our method, some first arithmetical applications are presented.

Mapping Class Groups

2017 ◽  
Author(s):  
Leah Childers ◽  
Dan Margalit
Keyword(s):  
Mapping Class Group ◽  
Class Group ◽  
Orientable Surface ◽  
Mapping Class ◽  
Class Groups ◽  
Open Problems ◽  
Dehn Twists ◽  
Group Of Homeomorphisms ◽  
Compact Orientable Surface ◽  
Group Of Symmetries

This chapter considers the mapping class group, the group of symmetries of a surface, and some of its basic properties. It first provides an overview of surfaces and the concept of homeomorphism before giving examples of homeomorphisms and defining the mapping class group as a certain quotient of the group of homeomorphisms of a surface. It then looks at Dehn twists and describes some of the relations they satisfy. It also presents a theorem stating that the mapping class group of a compact orientable surface is generated by Dehn twists and proves it. It concludes with some projects and open problems. The discussion also includes various exercises.

A NEW CHARACTERIZATION OF HALF-FACTORIAL KRULL MONOIDS

2010 ◽  
Vol 09 (05) ◽  
pp. 825-837 ◽  
Author(s):  
PAUL BAGINSKI ◽  
ROSS KRAVITZ
Keyword(s):  
Class Group ◽  
Finite Product ◽  
Krull Monoids ◽  
Irreducible Elements ◽  
Krull Monoid ◽  
Free Rank ◽  
Torsion Free Rank ◽  
Torsion Free

Let M be a Krull monoid. Then every element of M may be written as a finite product of irreducible elements. If for every a ∈ M, each two factorizations of a have the same number of irreducible elements, then M is called half-factorial. Using a property of element exponentiation, we provide a new characterization of half-factoriality, valid for all Krull monoids whose class group has torsion-free rank at most one.

scholarly journals THE CATENARY DEGREE OF KRULL MONOIDS II

2014 ◽  
Vol 98 (3) ◽  
pp. 324-354 ◽  
Author(s):  
ALFRED GEROLDINGER ◽  
QINGHAI ZHONG
Keyword(s):  
Class Group ◽  
Algebraic Function ◽  
Algebraic Number Field ◽  
Class Groups ◽  
Davenport Constant ◽  
Algebraic Function Field ◽  
Krull Monoids ◽  
Krull Monoid ◽  
Catenary Degree

Let$H$be a Krull monoid with finite class group$G$such that every class contains a prime divisor (for example, a ring of integers in an algebraic number field or a holomorphy ring in an algebraic function field). The catenary degree$\mathsf{c}(H)$of$H$is the smallest integer$N$with the following property: for each$a\in H$and each pair of factorizations$z,z^{\prime }$of$a$, there exist factorizations$z=z_{0},\dots ,z_{k}=z^{\prime }$of$a$such that, for each$i\in [1,k]$,$z_{i}$arises from$z_{i-1}$by replacing at most$N$atoms from$z_{i-1}$by at most$N$new atoms. To exclude trivial cases, suppose that$|G|\geq 3$. Then the catenary degree depends only on the class group$G$and we have$\mathsf{c}(H)\in [3,\mathsf{D}(G)]$, where$\mathsf{D}(G)$denotes the Davenport constant of$G$. The cases when$\mathsf{c}(H)\in \{3,4,\mathsf{D}(G)\}$have been previously characterized (see Theorem A). Based on a characterization of the catenary degree determined in the paper by Geroldingeret al.[‘The catenary degree of Krull monoids I’,J. Théor. Nombres Bordeaux23(2011), 137–169], we determine the class groups satisfying$\mathsf{c}(H)=\mathsf{D}(G)-1$. Apart from the extremal cases mentioned, the precise value of$\mathsf{c}(H)$is known for no further class groups.

scholarly journals On transfer homomorphisms of Krull monoids

2021 ◽  
Author(s):  
Alfred Geroldinger ◽  
Florian Kainrath
Keyword(s):  
Class Group ◽  
Finitely Generated ◽  
Krull Monoids ◽  
Krull Monoid ◽  
Transfer Homomorphism ◽  
Zero Sum

AbstractEvery Krull monoid has a transfer homomorphism onto a monoid of zero-sum sequences over a subset of its class group. This transfer homomorphism is a crucial tool for studying the arithmetic of Krull monoids. In the present paper, we strengthen and refine this tool for Krull monoids with finitely generated class group.

scholarly journals On The Asymptotic Values of Length Functions In Krull And Finitely Generated commutative Monoids

2003 ◽  
Vol 74 (3) ◽  
pp. 421-436 ◽  
Author(s):  
S. T. Chapman ◽  
J. C. Rosales
Keyword(s):  
Class Group ◽  
Finitely Generated ◽  
Divisor Class Group ◽  
Commutative Monoids ◽  
Divisor Class ◽  
Length Functions ◽  
Asymptotic Values ◽  
Nonidentity Element ◽  
Krull Monoid

AbstractLet M be a commutative cancellative atomic monoid. We consider the behaviour of the asymptotic length functions and on M. If M is finitely generated and reduced, then we present an algorithm for the computation of both and where x is a nonidentity element of M. We also explore the values that the functions and can attain when M is a Krull monoid with torsion divisor class group, and extend a well-known result of Zaks and Skula by showing how these values can be used to characterize when M is half-factorial.

scholarly journals Long Sets of Lengths With Maximal Elasticity

2018 ◽  
Vol 70 (6) ◽  
pp. 1284-1318 ◽  
Author(s):  
Alfred Geroldinger ◽  
Qinghai Zhong
Keyword(s):  
Finite Type ◽  
Algebraic Number ◽  
Class Group ◽  
Number Fields ◽  
Additive Combinatorics ◽  
Algebraic Number Fields ◽  
Krull Monoids ◽  
Sets Of Lengths ◽  
Positive Integers ◽  
Krull Domains

AbstractWe introduce a newinvariant describing the structure of sets of lengths in atomicmonoids and domains. For an atomic monoid H, let Δρ(H) be the set of all positive integers d that occur as differences of arbitrarily long arithmetical progressions contained in sets of lengths havingmaximal elasticity ρ(H). We study Δρ(H) for transfer Krull monoids of finite type (including commutative Krull domains with finite class group) with methods from additive combinatorics, and also for a class of weakly Krull domains (including orders in algebraic number fields) for which we use ideal theoretic methods.

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