Pub Date : 2024-09-17DOI: 10.1007/s00012-024-00867-3
Thomas Gobet, Baptiste Rognerud
We study two families of lattices whose number of elements are given by the numbers in even (respectively odd) positions in the Fibonacci sequence. The even Fibonacci lattice arises as the lattice of simple elements of a Garside monoid partially ordered by left-divisibility, and the odd Fibonacci lattice is an order ideal in the even one. We give a combinatorial proof of the lattice property, relying on a description of words for the Garside element in terms of Schröder trees, and on a recursive description of the even Fibonacci lattice. This yields an explicit formula to calculate meets and joins in the lattice. As a byproduct we also obtain that the number of words for the Garside element is given by a little Schröder number.
{"title":"Odd and even Fibonacci lattices arising from a Garside monoid","authors":"Thomas Gobet, Baptiste Rognerud","doi":"10.1007/s00012-024-00867-3","DOIUrl":"https://doi.org/10.1007/s00012-024-00867-3","url":null,"abstract":"<p>We study two families of lattices whose number of elements are given by the numbers in even (respectively odd) positions in the Fibonacci sequence. The even Fibonacci lattice arises as the lattice of simple elements of a Garside monoid partially ordered by left-divisibility, and the odd Fibonacci lattice is an order ideal in the even one. We give a combinatorial proof of the lattice property, relying on a description of words for the Garside element in terms of Schröder trees, and on a recursive description of the even Fibonacci lattice. This yields an explicit formula to calculate meets and joins in the lattice. As a byproduct we also obtain that the number of words for the Garside element is given by a little Schröder number.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-13DOI: 10.1007/s00012-024-00869-1
Richard Garner
In 1990, Johnstone gave a syntactic characterisation of the equational theories whose associated varieties are cartesian closed. Among such theories are all unary theories—whose models are sets equipped with an action by a monoid M—and all hyperaffine theories—whose models are sets with an action by a Boolean algebra B. We improve on Johnstone’s result by showing that an equational theory is cartesian closed just when its operations have a unique hyperaffine–unary decomposition. It follows that any non-degenerate cartesian closed variety is a variety of sets equipped with compatible actions by a monoid M and a Boolean algebra B; this is the classification theorem of the title.
1990 年,约翰斯通给出了等式理论的句法特征,这些等式理论的相关品种都是卡特西封闭的。在这些理论中,有所有一元理论(其模型是具有单元 M 作用的集合),也有所有超参数理论(其模型是具有布尔代数 B 作用的集合)。我们对约翰斯通的结果进行了改进,证明只有当等式理论的运算具有唯一的超参数一元分解时,该等式理论才是卡特封闭的。由此可知,任何非退化的卡方闭集都是由单元 M 和布尔代数 B 的相容运算组成的集合集合;这就是标题中的分类定理。
{"title":"Cartesian closed varieties I: the classification theorem","authors":"Richard Garner","doi":"10.1007/s00012-024-00869-1","DOIUrl":"https://doi.org/10.1007/s00012-024-00869-1","url":null,"abstract":"<p>In 1990, Johnstone gave a syntactic characterisation of the equational theories whose associated varieties are cartesian closed. Among such theories are all <i>unary</i> theories—whose models are sets equipped with an action by a monoid <i>M</i>—and all <i>hyperaffine</i> theories—whose models are sets with an action by a Boolean algebra <i>B</i>. We improve on Johnstone’s result by showing that an equational theory is cartesian closed just when its operations have a unique hyperaffine–unary decomposition. It follows that any non-degenerate cartesian closed variety is a variety of sets equipped with compatible actions by a monoid <i>M</i> and a Boolean algebra <i>B</i>; this is the classification theorem of the title.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1007/s00012-024-00868-2
Wolfgang Poiger
We provide a simple natural duality for the varieties generated by the negation- and implication-free reduct of a finite MV-chain. We study these varieties through the dual equivalences thus obtained. For example, we fully characterize their algebraically closed, existentially closed and injective members. We also explore the relationship between this natural duality and Priestley duality in terms of distributive skeletons and Priestley powers.
{"title":"Natural dualities for varieties generated by finite positive MV-chains","authors":"Wolfgang Poiger","doi":"10.1007/s00012-024-00868-2","DOIUrl":"https://doi.org/10.1007/s00012-024-00868-2","url":null,"abstract":"<p>We provide a simple natural duality for the varieties generated by the negation- and implication-free reduct of a finite MV-chain. We study these varieties through the dual equivalences thus obtained. For example, we fully characterize their algebraically closed, existentially closed and injective members. We also explore the relationship between this natural duality and Priestley duality in terms of distributive skeletons and Priestley powers.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-27DOI: 10.1007/s00012-024-00866-4
Anvar M. Nurakunov
A quasivariety (mathfrak N) is called relative congruence principal if, for every algebra (Ain mathfrak N), every compact (mathfrak N)-congruence on A is a principal (mathfrak N)-congruence. We characterize relative congruence principal quasivarieties in terms of one identity and two quasi-identities. We will use the characterization to show that there exists a continuum of relative congruence principal quasivarieties of algebras of a signature (sigma ), provided (sigma ) contains at least one operation of arity greater than 1. Several examples are provided.
{"title":"Quasivarieties of algebras whose compact relative congruences are principal","authors":"Anvar M. Nurakunov","doi":"10.1007/s00012-024-00866-4","DOIUrl":"https://doi.org/10.1007/s00012-024-00866-4","url":null,"abstract":"<p>A quasivariety <span>(mathfrak N)</span> is called <i>relative congruence principal</i> if, for every algebra <span>(Ain mathfrak N)</span>, every compact <span>(mathfrak N)</span>-congruence on <i>A</i> is a principal <span>(mathfrak N)</span>-congruence. We characterize relative congruence principal quasivarieties in terms of one identity and two quasi-identities. We will use the characterization to show that there exists a continuum of relative congruence principal quasivarieties of algebras of a signature <span>(sigma )</span>, provided <span>(sigma )</span> contains at least one operation of arity greater than 1. Several examples are provided.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-12DOI: 10.1007/s00012-024-00864-6
Tim Stokes
The override operation (sqcup ) is a natural one in computer science, and has connections with other areas of mathematics such as hyperplane arrangements. For arbitrary functions f and g, (fsqcup g) is the function with domain ({{,textrm{dom},}}(f)cup {{,textrm{dom},}}(g)) that agrees with f on ({{,textrm{dom},}}(f)) and with g on ({{,textrm{dom},}}(g) backslash {{,textrm{dom},}}(f)). Jackson and the author have shown that there is no finite axiomatisation of algebras of functions of signature ((sqcup )). But adding operations (such as update) to this minimal signature can lead to finite axiomatisations. For the functional signature ((sqcup ,backslash )) where (backslash ) is set-theoretic difference, Cirulis has given a finite equational axiomatisation as subtraction o-semilattices. Define (fcurlyvee g=(fsqcup g)cap (gsqcup f)) for all functions f and g; this is the largest domain restriction of the binary relation (fcup g) that gives a partial function. Now (fcap g=fbackslash (fbackslash g)) and (fsqcup g=fcurlyvee (fcurlyvee g)) for all functions f, g, so the signatures ((curlyvee )) and ((sqcup ,cap )) are both intermediate between ((sqcup )) and ((sqcup ,backslash )) in expressive power. We show that each is finitely axiomatised, with the former giving a proper quasivariety and the latter the variety of associative distributive o-semilattices in the sense of Cirulis.
{"title":"Override and restricted union for partial functions","authors":"Tim Stokes","doi":"10.1007/s00012-024-00864-6","DOIUrl":"https://doi.org/10.1007/s00012-024-00864-6","url":null,"abstract":"<p>The <i>override</i> operation <span>(sqcup )</span> is a natural one in computer science, and has connections with other areas of mathematics such as hyperplane arrangements. For arbitrary functions <i>f</i> and <i>g</i>, <span>(fsqcup g)</span> is the function with domain <span>({{,textrm{dom},}}(f)cup {{,textrm{dom},}}(g))</span> that agrees with <i>f</i> on <span>({{,textrm{dom},}}(f))</span> and with <i>g</i> on <span>({{,textrm{dom},}}(g) backslash {{,textrm{dom},}}(f))</span>. Jackson and the author have shown that there is no finite axiomatisation of algebras of functions of signature <span>((sqcup ))</span>. But adding operations (such as <i>update</i>) to this minimal signature can lead to finite axiomatisations. For the functional signature <span>((sqcup ,backslash ))</span> where <span>(backslash )</span> is set-theoretic difference, Cirulis has given a finite equational axiomatisation as subtraction o-semilattices. Define <span>(fcurlyvee g=(fsqcup g)cap (gsqcup f))</span> for all functions <i>f</i> and <i>g</i>; this is the largest domain restriction of the binary relation <span>(fcup g)</span> that gives a partial function. Now <span>(fcap g=fbackslash (fbackslash g))</span> and <span>(fsqcup g=fcurlyvee (fcurlyvee g))</span> for all functions <i>f</i>, <i>g</i>, so the signatures <span>((curlyvee ))</span> and <span>((sqcup ,cap ))</span> are both intermediate between <span>((sqcup ))</span> and <span>((sqcup ,backslash ))</span> in expressive power. We show that each is finitely axiomatised, with the former giving a proper quasivariety and the latter the variety of associative distributive o-semilattices in the sense of Cirulis.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1007/s00012-024-00863-7
Peter Jipsen, Erkko Lehtonen, Reinhard Pöschel
We consider S-operations(f :A^{n} rightarrow A) in which each argument is assigned a signum(s in S) representing a “property” such as being order-preserving or order-reversing with respect to a fixed partial order on A. The set S of such properties is assumed to have a monoid structure reflecting the behaviour of these properties under the composition of S-operations (e.g., order-reversing composed with order-reversing is order-preserving). The collection of all S-operations with prescribed properties for their signed arguments is not a clone (since it is not closed under arbitrary identification of arguments), but it is a preclone with special properties, which leads to the notion of S-preclone. We introduce S-relations(varrho = (varrho _{s})_{s in S}), S-relational clones, and a preservation property (), and we consider the induced Galois connection ({}^{S}{}textrm{Pol})–({}^{S}{}textrm{Inv}). The S-preclones and S-relational clones turn out to be exactly the closed sets of this Galois connection. We also establish some basic facts about the structure of the lattice of all S-preclones on A.
我们考虑 S 运算(f :A^{n} rightarrow A),其中每个参数都被赋予一个符号 (s in S) 代表一个 "属性",比如相对于 A 上的一个固定偏序而言是保序的或者是逆序的。所有对其有符号参数具有规定属性的 S 操作的集合不是克隆(因为它在参数的任意标识下不封闭),但它是具有特殊属性的前克隆,这就引出了 S 前克隆的概念。我们引入了 S 关系 (varrho = (varrho _{s})_{s in S})、S 关系克隆和保存属性(),并考虑了诱导伽罗瓦连接 ({}^{S}{}textrm{Pol})-({}^{S}{}textrm{Inv})。结果证明,S-前克隆和 S-关系克隆正是这种伽罗瓦连接的闭集。我们还建立了关于 A 上所有 S 前克隆的网格结构的一些基本事实。
{"title":"$$varvec{S}$$ -preclones and the Galois connection $$varvec{{}^{S}{}textrm{Pol}}$$ – $$varvec{{}^{S}{}textrm{Inv}}$$ , Part I","authors":"Peter Jipsen, Erkko Lehtonen, Reinhard Pöschel","doi":"10.1007/s00012-024-00863-7","DOIUrl":"https://doi.org/10.1007/s00012-024-00863-7","url":null,"abstract":"<p>We consider <i>S</i>-<i>operations</i> <span>(f :A^{n} rightarrow A)</span> in which each argument is assigned a <i>signum</i> <span>(s in S)</span> representing a “property” such as being order-preserving or order-reversing with respect to a fixed partial order on <i>A</i>. The set <i>S</i> of such properties is assumed to have a monoid structure reflecting the behaviour of these properties under the composition of <i>S</i>-operations (e.g., order-reversing composed with order-reversing is order-preserving). The collection of all <i>S</i>-operations with prescribed properties for their signed arguments is not a clone (since it is not closed under arbitrary identification of arguments), but it is a preclone with special properties, which leads to the notion of <i>S</i>-<i>preclone</i>. We introduce <i>S</i>-<i>relations</i> <span>(varrho = (varrho _{s})_{s in S})</span>, <i>S</i>-<i>relational clones</i>, and a preservation property (), and we consider the induced Galois connection <span>({}^{S}{}textrm{Pol})</span>–<span>({}^{S}{}textrm{Inv})</span>. The <i>S</i>-preclones and <i>S</i>-relational clones turn out to be exactly the closed sets of this Galois connection. We also establish some basic facts about the structure of the lattice of all <i>S</i>-preclones on <i>A</i>.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1007/s00012-024-00862-8
Tuğba Aslan, Mohamed Khaled, Gergely Székely
We define a special network that exhibits the large embeddings in any class of similar algebras. With the aid of this network, we introduce a notion of distance that conceivably counts the minimum number of dissimilarities, in a sense, between two given algebras in the class in hand; with the possibility that this distance may take the value (infty ). We display a number of inspirational examples from different areas of algebra, e.g., group theory and monounary algebras, to show that this research direction can be quite remarkable.
{"title":"On the networks of large embeddings","authors":"Tuğba Aslan, Mohamed Khaled, Gergely Székely","doi":"10.1007/s00012-024-00862-8","DOIUrl":"https://doi.org/10.1007/s00012-024-00862-8","url":null,"abstract":"<p>We define a special network that exhibits the large embeddings in any class of similar algebras. With the aid of this network, we introduce a notion of distance that conceivably counts the minimum number of dissimilarities, in a sense, between two given algebras in the class in hand; with the possibility that this distance may take the value <span>(infty )</span>. We display a number of inspirational examples from different areas of algebra, e.g., group theory and monounary algebras, to show that this research direction can be quite remarkable.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1007/s00012-024-00857-5
Simo Mthethwa, Gugulethu Nogwebela
The N-star compactifications of frames are the frame-theoretic counterpart of the N-point compactifications of locally compact Hausdorff spaces. A (pi )-compactification of a frame L is a compactification constructed using a special type of a basis called a (pi )-compact basis; the Freudenthal compactification is the largest (pi )-compactification of a rim-compact frame. As one of the main results, we show that the Freudenthal compactification of a regular continuous frame is the least upper bound for the set of all N-star compactifications. A compactification whose right adjoint preserves disjoint binary joins is called perfect. We establish a class of frames for which N-star compactifications are always perfect. For the class of zero-dimensional frames, we construct a compactification which is isomorphic to the Banaschewski compactification and the Freudenthal compactification; in some special case, this compactification is isomorphic to the Stone–Čech compactification.
框架的 N-star 压缩是局部紧凑 Hausdorff 空间的 N-point 压缩的框架理论对应物。框架 L 的 (pi )-紧凑化是使用一种叫做 (pi )-紧凑化基础的特殊类型的基础构造的紧凑化;弗罗伊登塔尔紧凑化是边缘紧凑框架的最大 (pi )-紧凑化。作为主要结果之一,我们证明了正则连续框的弗赖登塔尔紧凑化是所有 N 星紧凑化集合的最小上界。右邻接保留了不相交的二元连接的紧凑化被称为完美紧凑化。我们建立了一类 N 星压缩总是完美的框架。对于零维框架类,我们构造了一种与巴纳舍夫斯基(Banaschewski)紧凑化和弗赖登塔尔(Freudenthal)紧凑化同构的紧凑化;在某些特殊情况下,这种紧凑化与斯通切赫(Stone-Čech)紧凑化同构。
{"title":"The Freudenthal and other compactifications of continuous frames","authors":"Simo Mthethwa, Gugulethu Nogwebela","doi":"10.1007/s00012-024-00857-5","DOIUrl":"https://doi.org/10.1007/s00012-024-00857-5","url":null,"abstract":"<p>The <i>N</i>-star compactifications of frames are the frame-theoretic counterpart of the <i>N</i>-point compactifications of locally compact Hausdorff spaces. A <span>(pi )</span>-compactification of a frame <i>L</i> is a compactification constructed using a special type of a basis called a <span>(pi )</span>-compact basis; the Freudenthal compactification is the largest <span>(pi )</span>-compactification of a rim-compact frame. As one of the main results, we show that the Freudenthal compactification of a regular continuous frame is the least upper bound for the set of all <i>N</i>-star compactifications. A compactification whose right adjoint preserves disjoint binary joins is called perfect. We establish a class of frames for which <i>N</i>-star compactifications are always perfect. For the class of zero-dimensional frames, we construct a compactification which is isomorphic to the Banaschewski compactification and the Freudenthal compactification; in some special case, this compactification is isomorphic to the Stone–Čech compactification.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1007/s00012-024-00856-6
Nikolaos Galatos, Xiao Zhuang
We characterize all residuated lattices that have height equal to 3 and show that the variety they generate has continuum-many subvarieties. More generally, we study unilinear residuated lattices: their lattice is a union of disjoint incomparable chains, with bounds added. We we give two general constructions of unilinear residuated lattices, provide an axiomatization and a proof-theoretic calculus for the variety they generate, and prove the finite model property for various subvarieties.
{"title":"Unilinear residuated lattices: axiomatization, varieties and FEP","authors":"Nikolaos Galatos, Xiao Zhuang","doi":"10.1007/s00012-024-00856-6","DOIUrl":"https://doi.org/10.1007/s00012-024-00856-6","url":null,"abstract":"<p>We characterize all residuated lattices that have height equal to 3 and show that the variety they generate has continuum-many subvarieties. More generally, we study unilinear residuated lattices: their lattice is a union of disjoint incomparable chains, with bounds added. We we give two general constructions of unilinear residuated lattices, provide an axiomatization and a proof-theoretic calculus for the variety they generate, and prove the finite model property for various subvarieties.</p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1007/s00012-024-00858-4
Karim Boulabiar
Let X be an Archimedean vector lattice and (X_{+}) denote the positive cone of X. A unary operation (varpi ) on (X_{+}) is called a truncation on X if
$$begin{aligned} xwedge varpi left( yright) =varpi left( xright) wedge yquad text {for all }x,yin X_{+}. end{aligned}$$
Let (X^{u}) denote the universal completion of X with a distinguished weak element (e>0.) It is shown that a unary operation (varpi ) on (X_{+}) is a truncation on X if and only if there exists an element (uin X^{u}) and a component p of e such that
$$begin{aligned} pwedge u=0quad text {and}quad varpi left( xright) =px+uwedge x text {for all }xin X_{+}. end{aligned}$$
Here, px is the product of p and x with respect to the unique lattice-ordered multiplication in (X^{u}) having e as identity. As an example of illustration, if (varpi ) is a truncation on some (L_{p}left( {mu } right) )-space then there exists a measurable set A and a function (uin L_{0}left( {mu } right) ) vanishing on A such that (varpi left( xright) =1_{A}x+uwedge x) for all (xin L_{p}left( {mu } right) .)
让 X 是一个阿基米德向量网格,(X_{+}) 表示 X 的正锥。如果 $$begin{aligned} xwedge varpi left( yright) =varpi left( xright) wedge yquad text {for all }x,yin X_{+}, 那么在 (X_{+}) 上的一元操作 (varpi ) 称为 X 上的截断。end{aligned}$Let (X^{u}) denote the universal completion of X with a distinguished weak element (e>0.当且仅当存在一个元素 (uin X^{u}) 和一个 e 的分量 p,使得 $$$(X^{u}) 上的一元运算 (varpi ) 是 X 上的截断时,那么它就是 X 上的截断。分量 p,使得 $$begin{aligned} pwedge u=0quad text {and}quad varpi left( xright) =px+uwedge xtext {for all }xin X_{+}.end{aligned}$$这里,px 是 p 与 x 的乘积,与 (X^{u})中以 e 为特征的唯一格子有序乘法有关。举例说明如果 (varpi ) 是某个 (L_{p}left( {mu } right) )-空间上的一个截断空间,那么存在一个可测集合 A 和一个在 A 上消失的函数 (uin L_{0}left( {mu } right) ),使得 (varpi left( xright) =1_{A}x+uwedge x) for all (xin L_{p}left( {mu } right) .)
{"title":"A structure theorem for truncations on an Archimedean vector lattice","authors":"Karim Boulabiar","doi":"10.1007/s00012-024-00858-4","DOIUrl":"https://doi.org/10.1007/s00012-024-00858-4","url":null,"abstract":"<p>Let <i>X</i> be an Archimedean vector lattice and <span>(X_{+})</span> denote the positive cone of <i>X</i>. A unary operation <span>(varpi )</span> on <span>(X_{+})</span> is called a truncation on <i>X</i> if </p><span>$$begin{aligned} xwedge varpi left( yright) =varpi left( xright) wedge yquad text {for all }x,yin X_{+}. end{aligned}$$</span><p>Let <span>(X^{u})</span> denote the universal completion of <i>X</i> with a distinguished weak element <span>(e>0.)</span> It is shown that a unary operation <span>(varpi )</span> on <span>(X_{+})</span> is a truncation on <i>X</i> if and only if there exists an element <span>(uin X^{u})</span> and a component <i>p</i> of <i>e</i> such that </p><span>$$begin{aligned} pwedge u=0quad text {and}quad varpi left( xright) =px+uwedge x text {for all }xin X_{+}. end{aligned}$$</span><p>Here, <i>px</i> is the product of <i>p</i> and <i>x</i> with respect to the unique lattice-ordered multiplication in <span>(X^{u})</span> having <i>e</i> as identity. As an example of illustration, if <span>(varpi )</span> is a truncation on some <span>(L_{p}left( {mu } right) )</span>-space then there exists a measurable set <i>A</i> and a function <span>(uin L_{0}left( {mu } right) )</span> vanishing on <i>A</i> such that <span>(varpi left( xright) =1_{A}x+uwedge x)</span> for all <span>(xin L_{p}left( {mu } right) .)</span></p>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}