Semigroup ForumPub Date : 2024-02-07DOI: 10.1007/s00233-024-10410-4
Emil Daniel Schwab
{"title":"Broken Möbius categories of $$Q_{3}$$ -type and their split inverse semigroups","authors":"Emil Daniel Schwab","doi":"10.1007/s00233-024-10410-4","DOIUrl":"https://doi.org/10.1007/s00233-024-10410-4","url":null,"abstract":"<p>A class of Möbius monoids leads us to Möbius categories of <span>(Q_{3})</span>-type via a particular breaking process, where <span>(Q_{3})</span> is a quiver with three arrows (atoms). In this paper we show that a quasi-commutativity regarding composable atoms uniquely determines (via a certain local congruence) a half-factorial broken Möbius category of <span>(Q_{3})</span>-type as a quotient category of the path category of <span>(Q_{3})</span>. Some examples shed light on the development of the topic under discussion. On the other hand, the Möbius breaking process can be extended for inverse semigroups as well. The Leech inverse semigroups of the two broken Möbius categories (the path category of <span>(Q_{3})</span> and its quotient category) are split inverse semigroups in the sense that both are unions of two proper inverse subsemigroups, that is, both are with covering numbers 2. The connections on the two planes (broken Möbius categories and split inverse semigroups) are made on one hand by a local congruence <span>(varrho ^{+})</span> of the path category of <span>(Q_{3})</span>, and on the other hand by a normal inverse subsemigroup <span>(G^{+})</span> namely a gauge inverse subsemigroup. This gauge inverse semigroup is a full inverse subsemigroup of the almost Cartesian product <span>(Btimes _{0}B_{{mathbb {N}}})</span> of the bicyciclic semigroup <i>B</i> and the Brandt semigroup <span>(B_{{mathbb {N}}})</span>. Special properties of this almost Cartesian product are examined by comparison with the well known polycyclic monoid.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139752402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2024-02-02DOI: 10.1007/s00233-024-10409-x
G. H. Esslamzadeh, M. A. Faraji, B. Tabatabaie Shourijeh
{"title":"Orderability of the prefix expansion of an ordered inverse semigroup","authors":"G. H. Esslamzadeh, M. A. Faraji, B. Tabatabaie Shourijeh","doi":"10.1007/s00233-024-10409-x","DOIUrl":"https://doi.org/10.1007/s00233-024-10409-x","url":null,"abstract":"<p>We answer two orderability questions about the prefix expansion semigroup <b>Pr</b>(<i>G</i>) of an inverse semigroup <i>G</i>. We show that if <i>G</i> is a left ordered inverse semigroup, then <b>Pr</b>(<i>G</i>) is a left ordered inverse semigroup if and only if it is an ordered inverse semigroup, if and only if <i>G</i> is a semilattice. We also prove that when <i>G</i> and <b>Pr</b>(<i>G</i>) are left ordered, <b>Pr</b>(<i>G</i>) is proper if and only if <i>G</i> is proper. Positivity of the canonical map from <i>G</i> into <b>Pr</b>(<i>G</i>) is also proved. At the end we correct an existing result in the literature by showing that for two arbitrary inverse semigroups <i>G</i> and <i>H</i> the map <b>Pr</b>(<span>(pi )</span>): <b>Pr</b>(<i>G</i>) <span>(longrightarrow )</span> <b>Pr</b>(<i>H</i>) induced by the partial homomorphism <span>(pi )</span>: <i>G</i> <span>(longrightarrow )</span> <i>H</i> is not necessarily a homomorphism, but is a partial homomorphism.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139678844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2024-02-02DOI: 10.1007/s00233-024-10408-y
Sergio R. López-Permouth, Aaron Nicely, Majed Zailaee
{"title":"Semigroup collaborations between elementary operations","authors":"Sergio R. López-Permouth, Aaron Nicely, Majed Zailaee","doi":"10.1007/s00233-024-10408-y","DOIUrl":"https://doi.org/10.1007/s00233-024-10408-y","url":null,"abstract":"<p>Given two operations <span>(*)</span> and <span>(circ )</span> on a set <i>S</i>, an operation <span>(star )</span> on <i>S</i> is said to be a <i>collaboration</i> between <span>(*)</span> and <span>(circ )</span> if for all <span>(a,b in S)</span>, <span>(a star b)</span> <span>(in {a *b, acirc b })</span>. Another term for collaborations is two-option operations. We are interested in learning what associative collaborations of two given operations <span>(*)</span> and <span>(circ )</span> there may be. We do not require that <span>(*)</span> and <span>(circ )</span> themselves be associative. For this project, as an initial experiment, we consider <i>Plus-Minus</i> operations (i.e. collaborations between addition and subtraction on an abelian group) and <i>Plus-Times</i> operations (i.e. collaborations between the addition and multiplication operations on a semiring.) Our study of Plus-Minus operations focuses on the additive integers but extends to ordered groups. For Plus Times operations, we make some headway in the case of the semiring of natural numbers. We produce an exhaustive list of associative collaborations between the usual addition and multiplication on the natural numbers <span>({mathbb {N}})</span>. The Plus-Times operations we found are all examples of a type of construction which we define here and that we call <i>augmentations by multidentities</i>. An augmentation by multidentities combines two separate magmas <i>A</i> and <i>B</i> to create another, <i>A</i>(<i>B</i>), having <span>(A sqcup B)</span> as underlying set, and in such a way that the elements of <i>B</i> act as identities over those of <i>A</i>. Hence, <i>B</i> consists of a sort of multiple identities (explaining the moniker multidentities.) When <i>A</i> and <i>B</i> are both semigroups then so is <i>A</i>(<i>B</i>). Understanding the connection between certain collaborations and augmentation by multidenties removes, in several cases, the need for cumbersome computations to verify associativity. A final section discusses connections between group collaborations and skew braces.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139665242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2024-01-29DOI: 10.1007/s00233-023-10403-9
Alex Feiner, Zion Hefty
{"title":"The Frobenius problem over number fields with a real embedding","authors":"Alex Feiner, Zion Hefty","doi":"10.1007/s00233-023-10403-9","DOIUrl":"https://doi.org/10.1007/s00233-023-10403-9","url":null,"abstract":"<p>Given a number field <i>K</i> with at least one real embedding, we generalize the notion of the classical Frobenius problem to the ring of integers <span>({mathfrak {O}}_K)</span> of <i>K</i> by describing certain Frobenius semigroups, <span>(textrm{Frob}(alpha _1,ldots ,alpha _n))</span>, for appropriate elements <span>(alpha _1,ldots ,alpha _nin {mathfrak {O}}_K)</span>. We construct a partial ordering on <span>(textrm{Frob}(alpha _1,ldots ,alpha _n))</span>, and show that this set is completely described by the maximal elements with respect to this ordering. We also show that <span>(textrm{Frob}(alpha _1,ldots ,alpha _n))</span> will always have finitely many such maximal elements, but in general, the number of maximal elements can grow without bound as <i>n</i> is fixed and <span>(alpha _1,ldots ,alpha _nin {mathfrak {O}}_K)</span> vary. Explicit examples of the Frobenius semigroups are also calculated for certain cases in real quadratic number fields.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139647283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2024-01-24DOI: 10.1007/s00233-023-10405-7
Om Prakash Bhardwaj, Indranath Sengupta
{"title":"Affine semigroups of maximal projective dimension-II","authors":"Om Prakash Bhardwaj, Indranath Sengupta","doi":"10.1007/s00233-023-10405-7","DOIUrl":"https://doi.org/10.1007/s00233-023-10405-7","url":null,"abstract":"<p>If the Krull dimension of the semigroup ring is greater than one, then affine semigroups of maximal projective dimension (<span>(textrm{MPD})</span>) are not Cohen–Macaulay, but they may be Buchsbaum. We give a necessary and sufficient condition for simplicial <span>(textrm{MPD})</span>-semigroups to be Buchsbaum in terms of pseudo-Frobenius elements. We give certain characterizations of <span>(prec )</span>-almost symmetric <span>({mathcal {C}})</span>-semigroups. When the cone is full, we prove the irreducible <span>({mathcal {C}})</span>-semigroups, and <span>(prec )</span>-almost symmetric <span>({mathcal {C}})</span>-semigroups with Betti-type three satisfy the extended Wilf conjecture. For <span>(e ge 4)</span>, we give a class of MPD-semigroups in <span>({mathbb {N}}^2)</span> such that there is no upper bound on the Betti-type in terms of embedding dimension <i>e</i>. Thus, the Betti-type may not be a bounded function of the embedding dimension. We further explore the submonoids of <span>({mathbb {N}}^d)</span>, which satisfy the Arf property, and prove that Arf submonoids containing multiplicity are <span>(textrm{PI})</span>-monoids.\u0000</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139561357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2023-12-19DOI: 10.1007/s00233-023-10402-w
Shuang Li, Xia Zhang
{"title":"Completions of posemigroups by cuts and beyond","authors":"Shuang Li, Xia Zhang","doi":"10.1007/s00233-023-10402-w","DOIUrl":"https://doi.org/10.1007/s00233-023-10402-w","url":null,"abstract":"<p>This work is devoted to describing the completion of a posemigroup by cuts. We introduce cut-stable morphisms between posemigroups and obtain that the category <span>({mathsf {RQuant_{wedge }}})</span> of quantales with meet and residuals preserving morphisms is a full reflective subcategory of the category <span>({textsf{CSPoSgr}})</span> of posemigroups with cut-stable morphisms. As an application, we also characterize other kinds of completions for posemigroups by means of lower cuts.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138819726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2023-12-11DOI: 10.1007/s00233-023-10401-x
Żywilla Fechner, Eszter Gselmann, László Székelyhidi
{"title":"Moment functions of higher rank on some types of hypergroups","authors":"Żywilla Fechner, Eszter Gselmann, László Székelyhidi","doi":"10.1007/s00233-023-10401-x","DOIUrl":"https://doi.org/10.1007/s00233-023-10401-x","url":null,"abstract":"<p>We consider moment functions of higher order. In our earlier paper, we have already investigated the moment functions of higher order on groups. The main purpose of this work is to prove characterization theorems for moment functions on the multivariate polynomial hypergroups and on the Sturm–Liouville hypergroups. In the first case, the moment generating functions of higher rank are partial derivatives (taken at zero) of the composition of generating polynomials of the hypergroup and functions whose coordinates are given by the formal power series. On Sturm–Liouville hypergroups the moment functions of higher rank are restrictions of even smooth functions that also satisfy certain boundary value problems. The second characterization of moment functions of higher rank on Sturm–Liouville hypergroups is given by means of an exponential family. In this case, the moment functions of higher rank are partial derivatives of an appropriately modified exponential family again taken at zero.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138572633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2023-12-04DOI: 10.1007/s00233-023-10400-y
Alexander V. Osipov, Konstantin Kazachenko
{"title":"Joint continuity in semitopological monoids and semilattices","authors":"Alexander V. Osipov, Konstantin Kazachenko","doi":"10.1007/s00233-023-10400-y","DOIUrl":"https://doi.org/10.1007/s00233-023-10400-y","url":null,"abstract":"<p>We study the separately continuous actions of semitopological monoids on pseudocompact spaces. The main aim of this paper is to generalize Lawson’s results to some class of pseudocompact spaces. Also, we introduce the concept of a weak <span>(q_D)</span>-space and prove that a pseudocompact space and a weak <span>(q_D)</span>-space form a Grothendieck pair. As an application of the main result, we investigate the continuity of multiplication and taking inverses in subgroups of semitopological semigroups. In particular, we get that if <span>((S, bullet ))</span> is a Tychonoff pseudocompact semitopological monoid with a quasicontinuous multiplication <span>(bullet )</span> and <i>G</i> is a subgroup of <i>S</i>, then <i>G</i> is a topological group. Also, we study the continuity of operations in semitopological semilattices.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138493886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2023-12-04DOI: 10.1007/s00233-023-10399-2
Olga B. Sapir
{"title":"Limit varieties generated by finite non-J-trivial aperiodic monoids","authors":"Olga B. Sapir","doi":"10.1007/s00233-023-10399-2","DOIUrl":"https://doi.org/10.1007/s00233-023-10399-2","url":null,"abstract":"<p>Jackson and Lee proved that certain six-element monoid generates a hereditarily finitely based variety <span>({{mathbb {E}}}^1)</span> whose lattice of subvarieties contains an infinite ascending chain. We identify syntactic monoids which generate finitely generated subvarieties of <span>({{mathbb {E}}}^1)</span> and show that one of these finite monoids together with certain seven-element monoid generates a new limit variety.</p>","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138493887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semigroup ForumPub Date : 2023-11-08DOI: 10.1007/s00233-023-10394-7
Xavier Mary
{"title":"On the structure of semigroups whose regular elements are completely regular","authors":"Xavier Mary","doi":"10.1007/s00233-023-10394-7","DOIUrl":"https://doi.org/10.1007/s00233-023-10394-7","url":null,"abstract":"","PeriodicalId":49549,"journal":{"name":"Semigroup Forum","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135340352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}