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MATHEMATICS (742 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 538 Journals sorted alphabetically
Abakós     Open Access   (Followers: 4)
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg     Hybrid Journal   (Followers: 4)
Academic Voices : A Multidisciplinary Journal     Open Access   (Followers: 2)
Accounting Perspectives     Full-text available via subscription   (Followers: 7)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 15)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Mathematical Software (TOMS)     Hybrid Journal   (Followers: 6)
ACS Applied Materials & Interfaces     Hybrid Journal   (Followers: 33)
Acta Applicandae Mathematicae     Hybrid Journal   (Followers: 1)
Acta Mathematica     Hybrid Journal   (Followers: 12)
Acta Mathematica Hungarica     Hybrid Journal   (Followers: 2)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5)
Acta Mathematica Sinica, English Series     Hybrid Journal   (Followers: 6)
Acta Mathematica Vietnamica     Hybrid Journal  
Acta Mathematicae Applicatae Sinica, English Series     Hybrid Journal  
Advanced Science Letters     Full-text available via subscription   (Followers: 11)
Advances in Applied Clifford Algebras     Hybrid Journal   (Followers: 4)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 4)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 9)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 19)
Advances in Decision Sciences     Open Access   (Followers: 3)
Advances in Difference Equations     Open Access   (Followers: 3)
Advances in Fixed Point Theory     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 14)
Advances in Linear Algebra & Matrix Theory     Open Access   (Followers: 3)
Advances in Materials Science     Open Access   (Followers: 14)
Advances in Mathematical Physics     Open Access   (Followers: 4)
Advances in Mathematics     Full-text available via subscription   (Followers: 11)
Advances in Nonlinear Analysis     Hybrid Journal  
Advances in Numerical Analysis     Open Access   (Followers: 5)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Pure and Applied Mathematics     Hybrid Journal   (Followers: 6)
Advances in Pure Mathematics     Open Access   (Followers: 6)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aequationes Mathematicae     Hybrid Journal   (Followers: 2)
African Journal of Educational Studies in Mathematics and Sciences     Full-text available via subscription   (Followers: 5)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Afrika Matematika     Hybrid Journal   (Followers: 1)
Air, Soil & Water Research     Open Access   (Followers: 13)
AKSIOMA Journal of Mathematics Education     Open Access   (Followers: 1)
Al-Jabar : Jurnal Pendidikan Matematika     Open Access   (Followers: 1)
Algebra and Logic     Hybrid Journal   (Followers: 6)
Algebra Colloquium     Hybrid Journal   (Followers: 4)
Algebra Universalis     Hybrid Journal   (Followers: 2)
Algorithmic Operations Research     Full-text available via subscription   (Followers: 5)
Algorithms     Open Access   (Followers: 11)
Algorithms Research     Open Access   (Followers: 1)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Mathematical Analysis     Open Access  
American Journal of Mathematics     Full-text available via subscription   (Followers: 6)
American Journal of Operations Research     Open Access   (Followers: 5)
An International Journal of Optimization and Control: Theories & Applications     Open Access   (Followers: 10)
Anadol University Journal of Science and Technology B : Theoritical Sciences     Open Access  
Analele Universitatii Ovidius Constanta - Seria Matematica     Open Access   (Followers: 1)
Analysis and Applications     Hybrid Journal   (Followers: 1)
Analysis and Mathematical Physics     Hybrid Journal   (Followers: 5)
Analysis Mathematica     Full-text available via subscription  
Analysis. International mathematical journal of analysis and its applications     Hybrid Journal   (Followers: 2)
Annales Mathematicae Silesianae     Open Access  
Annales mathématiques du Québec     Hybrid Journal   (Followers: 4)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica     Open Access  
Annali di Matematica Pura ed Applicata     Hybrid Journal   (Followers: 1)
Annals of Combinatorics     Hybrid Journal   (Followers: 4)
Annals of Data Science     Hybrid Journal   (Followers: 12)
Annals of Discrete Mathematics     Full-text available via subscription   (Followers: 6)
Annals of Mathematics     Full-text available via subscription   (Followers: 1)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 3)
Annals of the Alexandru Ioan Cuza University - Mathematics     Open Access  
Annals of the Institute of Statistical Mathematics     Hybrid Journal   (Followers: 1)
Annals of West University of Timisoara - Mathematics     Open Access  
Annals of West University of Timisoara - Mathematics and Computer Science     Open Access  
Annuaire du Collège de France     Open Access   (Followers: 6)
ANZIAM Journal     Open Access   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applications of Mathematics     Hybrid Journal   (Followers: 2)
Applied Categorical Structures     Hybrid Journal   (Followers: 3)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 14)
Applied Mathematics     Open Access   (Followers: 3)
Applied Mathematics     Open Access   (Followers: 7)
Applied Mathematics & Optimization     Hybrid Journal   (Followers: 8)
Applied Mathematics - A Journal of Chinese Universities     Hybrid Journal  
Applied Mathematics Letters     Full-text available via subscription   (Followers: 2)
Applied Mathematics Research eXpress     Hybrid Journal   (Followers: 1)
Applied Network Science     Open Access   (Followers: 3)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 6)
Arab Journal of Mathematical Sciences     Open Access   (Followers: 3)
Arabian Journal of Mathematics     Open Access   (Followers: 2)
Archive for Mathematical Logic     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
Armenian Journal of Mathematics     Open Access  
Arnold Mathematical Journal     Hybrid Journal   (Followers: 1)
Artificial Satellites     Open Access   (Followers: 21)
Asia-Pacific Journal of Operational Research     Hybrid Journal   (Followers: 3)
Asian Journal of Algebra     Open Access   (Followers: 1)
Asian-European Journal of Mathematics     Hybrid Journal   (Followers: 2)
Australian Mathematics Teacher, The     Full-text available via subscription   (Followers: 6)
Australian Primary Mathematics Classroom     Full-text available via subscription   (Followers: 4)
Australian Senior Mathematics Journal     Full-text available via subscription   (Followers: 1)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Axioms     Open Access   (Followers: 1)
Baltic International Yearbook of Cognition, Logic and Communication     Open Access   (Followers: 1)
Basin Research     Hybrid Journal   (Followers: 5)
BIBECHANA     Open Access   (Followers: 2)
Biomath     Open Access  
BIT Numerical Mathematics     Hybrid Journal  
Boletim Cearense de Educação e História da Matemática     Open Access  
Boletim de Educação Matemática     Open Access  
Boletín de la Sociedad Matemática Mexicana     Hybrid Journal  
Bollettino dell'Unione Matematica Italiana     Full-text available via subscription   (Followers: 1)
British Journal of Mathematical and Statistical Psychology     Full-text available via subscription   (Followers: 20)
Bruno Pini Mathematical Analysis Seminar     Open Access  
Buletinul Academiei de Stiinte a Republicii Moldova. Matematica     Open Access   (Followers: 12)
Bulletin des Sciences Mathamatiques     Full-text available via subscription   (Followers: 4)
Bulletin of Dnipropetrovsk University. Series : Communications in Mathematical Modeling and Differential Equations Theory     Open Access   (Followers: 2)
Bulletin of Mathematical Sciences     Open Access   (Followers: 1)
Bulletin of Symbolic Logic     Full-text available via subscription   (Followers: 2)
Bulletin of the Australian Mathematical Society     Full-text available via subscription   (Followers: 1)
Bulletin of the Brazilian Mathematical Society, New Series     Hybrid Journal  
Bulletin of the London Mathematical Society     Hybrid Journal   (Followers: 4)
Bulletin of the Malaysian Mathematical Sciences Society     Hybrid Journal  
Calculus of Variations and Partial Differential Equations     Hybrid Journal  
Canadian Journal of Science, Mathematics and Technology Education     Hybrid Journal   (Followers: 19)
Carpathian Mathematical Publications     Open Access   (Followers: 1)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
CHANCE     Hybrid Journal   (Followers: 5)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Annals of Mathematics, Series B     Hybrid Journal  
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Mathematics     Open Access  
Clean Air Journal     Full-text available via subscription   (Followers: 1)
Cogent Mathematics     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Collectanea Mathematica     Hybrid Journal  
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Commentarii Mathematici Helvetici     Hybrid Journal   (Followers: 1)
Communications in Advanced Mathematical Sciences     Open Access  
Communications in Combinatorics and Optimization     Open Access  
Communications in Contemporary Mathematics     Hybrid Journal  
Communications in Mathematical Physics     Hybrid Journal   (Followers: 2)
Communications On Pure & Applied Mathematics     Hybrid Journal   (Followers: 3)
Complex Analysis and its Synergies     Open Access   (Followers: 2)
Complex Variables and Elliptic Equations: An International Journal     Hybrid Journal  
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 8)
Compositio Mathematica     Full-text available via subscription   (Followers: 1)
Comptes Rendus Mathematique     Full-text available via subscription   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 3)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 5)
Computational Methods and Function Theory     Hybrid Journal  
Computational Optimization and Applications     Hybrid Journal   (Followers: 8)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 9)
Concrete Operators     Open Access   (Followers: 5)
Confluentes Mathematici     Hybrid Journal  
Contributions to Game Theory and Management     Open Access  
COSMOS     Hybrid Journal  
Cryptography and Communications     Hybrid Journal   (Followers: 13)
Cuadernos de Investigación y Formación en Educación Matemática     Open Access  
Cubo. A Mathematical Journal     Open Access  
Current Research in Biostatistics     Open Access   (Followers: 8)
Czechoslovak Mathematical Journal     Hybrid Journal   (Followers: 1)
Demographic Research     Open Access   (Followers: 12)
Demonstratio Mathematica     Open Access  
Dependence Modeling     Open Access  
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 31)
Developments in Clay Science     Full-text available via subscription   (Followers: 1)
Developments in Mineral Processing     Full-text available via subscription   (Followers: 3)
Dhaka University Journal of Science     Open Access  
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 4)
Differentsial'nye Uravneniya     Open Access  
Discrete Mathematics     Hybrid Journal   (Followers: 8)
Discrete Mathematics & Theoretical Computer Science     Open Access  
Discrete Mathematics, Algorithms and Applications     Hybrid Journal   (Followers: 2)
Discussiones Mathematicae - General Algebra and Applications     Open Access  
Discussiones Mathematicae Graph Theory     Open Access   (Followers: 1)
Diskretnaya Matematika     Full-text available via subscription  
Dnipropetrovsk University Mathematics Bulletin     Open Access  
Doklady Akademii Nauk     Open Access  
Doklady Mathematics     Hybrid Journal  
Duke Mathematical Journal     Full-text available via subscription   (Followers: 1)
Eco Matemático     Open Access  
Econometrics     Open Access   (Followers: 2)
Edited Series on Advances in Nonlinear Science and Complexity     Full-text available via subscription  
Educação Matemática Debate     Open Access  
EduMatSains     Open Access  
Electronic Journal of Combinatorics     Open Access  

        1 2 3 4 | Last

Journal Cover
Algebra Universalis
Journal Prestige (SJR): 0.583
Citation Impact (citeScore): 1
Number of Followers: 2  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1420-8911 - ISSN (Online) 0002-5240
Published by Springer-Verlag Homepage  [2352 journals]
  • A Gelfand duality for compact pospaces
    • Authors: Laurent De Rudder; Georges Hansoul
      Abstract: It is well known that the category of compact Hausdorff spaces is dually equivalent to the category of commutative \(C^\star \) -algebras. More generally, this duality can be seen as a part of a square of dualities and equivalences between compact Hausdorff spaces, \(C^\star \) -algebras, compact regular frames and de Vries algebras. Three of these equivalences have been extended to equivalences between compact pospaces, stably compact frames and proximity frames, the fourth part of what will be a second square being lacking. We propose the category of bounded Archimedean \(\ell \) -semi-algebras to complete the second square of equivalences and to extend the category of \(C^\star \) -algebras.
      PubDate: 2018-05-17
      DOI: 10.1007/s00012-018-0519-7
      Issue No: Vol. 79, No. 2 (2018)
  • A refinement of the equaclosure operator
    • Authors: J. B. Nation; Joy Nishida
      Abstract: A stronger version of a known property is shown to hold for the natural equaclosure operator on subquasivariety lattices.
      PubDate: 2018-05-14
      DOI: 10.1007/s00012-018-0518-8
      Issue No: Vol. 79, No. 2 (2018)
  • Congruence meet-semidistributive locally finite varieties and a finite
           basis theorem
    • Authors: George F. McNulty; Ross Willard
      Abstract: We provide several conditions that, among locally finite varieties, characterize congruence meet-semidistributivity and we use these conditions to give a new proof of a finite basis theorem published by Baker, McNulty, and Wang in 2004. This finite basis theorem extends Willard’s Finite Basis Theorem.
      PubDate: 2018-05-14
      DOI: 10.1007/s00012-018-0524-x
      Issue No: Vol. 79, No. 2 (2018)
  • Polymorphism clones of homogeneous structures: generating sets,
           Sierpiński rank, cofinality and the Bergman property
    • Authors: Christian Pech; Maja Pech
      Abstract: In this paper, motivated by classical results by Sierpiński, Arnold and Kolmogorov, we derive sufficient conditions for polymorphism clones of homogeneous structures to have a generating set of bounded arity. We use our findings in order to describe a class of homogeneous structures whose polymorphism clones have a finite Sierpiński rank, uncountable cofinality, and the Bergman property.
      PubDate: 2018-05-14
      DOI: 10.1007/s00012-018-0527-7
      Issue No: Vol. 79, No. 2 (2018)
  • A conference report: The 5th Novi Sad Algebraic Conference (in conjunction
           with AAA94)
    • Authors: Igor Dolinka
      Abstract: Headlining the Topical Collection dedicated to The 5th Novi Sad Algebraic Conference (NSAC 2017), we provide a brief report of the conference along with some of its history and background.
      PubDate: 2018-05-09
      DOI: 10.1007/s00012-018-0528-6
      Issue No: Vol. 79, No. 2 (2018)
  • Infinitely many reducts of homogeneous structures
    • Authors: Bertalan Bodor; Peter J. Cameron; Csaba Szabó
      Abstract: It is shown that the countably infinite dimensional pointed vector space (the vector space equipped with a constant) over a finite field has infinitely many first order definable reducts. This implies that the countable homogeneous Boolean-algebra has infinitely many reducts.
      PubDate: 2018-05-09
      DOI: 10.1007/s00012-018-0526-8
      Issue No: Vol. 79, No. 2 (2018)
  • On classes of structures axiomatizable by universal d-Horn sentences and
           universal positive disjunctions
    • Authors: Guillermo Badia; João Marcos
      Abstract: We provide universal algebraic characterizations (in the sense of not involving any “logical notion”) of some elementary classes of structures whose definitions involve universal d-Horn sentences and universally closed disjunctions of atomic formulas. These include, in particular, the classes of fields, of non-trivial rings, and of directed graphs without loops where every two elements are adjacent. The classical example of this kind of characterization result is the HSP theorem, but there are myriad other examples (e.g., the characterization of elementary classes using isomorphic images, ultraproducts and ultrapowers due to Keisler and Shelah).
      PubDate: 2018-05-07
      DOI: 10.1007/s00012-018-0522-z
      Issue No: Vol. 79, No. 2 (2018)
  • Congruence structure of planar semimodular lattices: the General Swing
    • Authors: Gábor Czédli; George Grätzer; Harry Lakser
      Abstract: The Swing Lemma, proved by G. Grätzer in 2015, describes how a congruence spreads from a prime interval to another in a slim (having no \(\mathsf {M}_{3}\) sublattice), planar, semimodular lattice. We generalize the Swing Lemma to planar semimodular lattices.
      PubDate: 2018-04-30
      DOI: 10.1007/s00012-018-0483-2
      Issue No: Vol. 79, No. 2 (2018)
  • Infinite idempotent quasi-affine algebras need not be hereditarily
           absorption free
    • Authors: Joe Cyr
      Abstract: It is known that for finite algebras, solvable implies hereditarily absorption free. We present an example which shows that this implication does not hold for infinite algebras. This example is also quasi-affine, contradicting an earlier statement that quasi-affine algebras are hereditarily absorption free.
      PubDate: 2018-04-24
      DOI: 10.1007/s00012-018-0521-0
      Issue No: Vol. 79, No. 2 (2018)
  • Maximal essential extensions in the context of frames
    • Authors: Richard N. Ball; Aleš Pultr
      Abstract: We show that every frame can be essentially embedded in a Boolean frame, and that this embedding is the maximal essential extension of the frame in the sense that it factors uniquely through any other essential extension. This extension can be realized as the embedding \(L \rightarrow \mathcal {N}(L) \rightarrow \mathcal {B}\mathcal {N}(L)\) , where \(L \rightarrow \mathcal {N}(L)\) is the familiar embedding of L into its congruence frame \(\mathcal {N}(L)\) , and \(\mathcal {N}(L) \rightarrow \mathcal {B}\mathcal {N}(L)\) is the Booleanization of \(\mathcal {N}(L)\) . Finally, we show that for subfit frames the extension can also be realized as the embedding \(L \rightarrow {{\mathrm{S}}}_\mathfrak {c}(L)\) of L into its complete Boolean algebra \({{\mathrm{S}}}_\mathfrak {c}(L)\) of sublocales which are joins of closed sublocales.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0508-x
      Issue No: Vol. 79, No. 2 (2018)
  • Special elements of the lattice of monoid varieties
    • Authors: Sergey V. Gusev
      Abstract: We completely classify all neutral and costandard elements in the lattice \(\mathbb {MON}\) of all monoid varieties. Further, we prove that an arbitrary upper-modular element of \(\mathbb {MON}\) except the variety of all monoids is either a completely regular or a commutative variety. Finally, we verify that all commutative varieties of monoids are codistributive elements of \(\mathbb {MON}\) . Thus, the problems of describing codistributive or upper-modular elements of \(\mathbb {MON}\) are completely reduced to the completely regular case.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0513-0
      Issue No: Vol. 79, No. 2 (2018)
  • An error in a proof in Boolean Algebras with Operators, Part I
    • Authors: Richard L. Kramer; Roger D. Maddux
      Abstract: An error in a proof of a correct theorem in the classic paper, Boolean Algebras with Operators, Part I, by Jónsson and Tarski is discussed.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0520-1
      Issue No: Vol. 79, No. 2 (2018)
  • A note on archimedean ordered semigroups
    • Authors: Niovi Kehayopulu
      Abstract: We characterize the ordered semigroups that are archimedean and contain an intra-regular element, showing that they are exactly nil extensions of simple ordered semigroups, also the ordered semigroups that are both archimedean and \(\pi \) -semisimple or both archimedean and \(\pi \) -quasi-semisimple.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0502-3
      Issue No: Vol. 79, No. 2 (2018)
  • Axiomatizations of universal classes through infinitary logic
    • Authors: Michał M. Stronkowski
      Abstract: We present a scheme for providing axiomatizations of universal classes. We use infinitary sentences there. New proofs of Birkhoff’s \(\mathsf {HSP}\) -theorem and Mal’cev’s \(\mathsf {SPP_U}\) -theorem are derived. In total, we present 75 facts of this sort.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0507-y
      Issue No: Vol. 79, No. 2 (2018)
  • Quasiorder lattices of varieties
    • Authors: Gergő Gyenizse; Miklós Maróti
      Abstract: The set \({{\mathrm{Quo}}}(\mathbf {A})\) of compatible quasiorders (reflexive and transitive relations) of an algebra \(\mathbf {A}\) forms a lattice under inclusion, and the lattice \({{\mathrm{Con}}}(\mathbf {A})\) of congruences of \(\mathbf {A}\) is a sublattice of \({{\mathrm{Quo}}}(\mathbf {A})\) . We study how the shape of congruence lattices of algebras in a variety determine the shape of quasiorder lattices in the variety. In particular, we prove that a locally finite variety is congruence distributive [modular] if and only if it is quasiorder distributive [modular]. We show that the same property does not hold for meet semi-distributivity. From tame congruence theory we know that locally finite congruence meet semi-distributive varieties are characterized by having no sublattice of congruence lattices isomorphic to the lattice \(\mathbf {M}_3\) . We prove that the same holds for quasiorder lattices of finite algebras in arbitrary congruence meet semi-distributive varieties, but does not hold for quasiorder lattices of infinite algebras even in the variety of semilattices.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0512-1
      Issue No: Vol. 79, No. 2 (2018)
  • Homomorphisms from $$C(X,\mathbb {Z})$$ C ( X , Z ) into a ring of
           continuous functions
    • Authors: Ali Reza Olfati
      Abstract: Let X be a zero-dimensional space and Y be a Tychonoff space. We show that every non-zero ring homomorphism \(\Phi :C(X,\mathbb {Z})\rightarrow C(Y)\) can be induced by a continuous function \(\pi :Y\rightarrow \upsilon _0X.\) Using this, it turns out that the kernel of such homomorphisms is equal to the intersection of some family of minimal prime ideals in \({{\mathrm{MinMax}}}\left( C(X,\mathbb {Z})\right) .\) As a consequence, we are able to obtain the fact that the factor ring \(\frac{C(X,\mathbb {Z})}{C_F(X,\mathbb {Z})}\) is a subring of some ring of continuous functions if and only if each infinite subset of isolated points of X has a limit point in \(\upsilon _0X.\) This implies that for an arbitrary infinite set X,  the factor ring \(\frac{\prod _{_{x\in X}}\mathbb {Z}_{_{x}}}{\oplus _{_{x\in X}}\mathbb {Z}_{_{x}}}\) is not embedded in any ring of continuous functions. The classical ring of quotients of the factor ring \(\frac{C(X,\mathbb {Z})}{C_F(X,\mathbb {Z})}\) is fully characterized. Finally, it is shown that the factor ring \(\frac{C(X,\mathbb {Z})}{C_F(X,\mathbb {Z})}\) is an I-ring if and only if each infinite subset of isolated points on X has a limit point in \(\upsilon _0X\) and \(\upsilon _0X{\setminus }\mathbb {I}(X)\) is an extremally disconnected \(C_{\mathbb {Z}}\) -subspace of \(\upsilon _0X,\) where \(\mathbb {I}(X)\) is the set of all isolated points of X.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0509-9
      Issue No: Vol. 79, No. 2 (2018)
  • The convolution algebra
    • Authors: John Harding; Carol Walker; Elbert Walker
      Abstract: For L a complete lattice L and \(\mathfrak {X}=(X,(R_i)_I)\) a relational structure, we introduce the convolution algebra \(L^{\mathfrak {X}}\) . This algebra consists of the lattice \(L^X\) equipped with an additional \(n_i\) -ary operation \(f_i\) for each \(n_i+1\) -ary relation \(R_i\) of \(\mathfrak {X}\) . For \(\alpha _1,\ldots ,\alpha _{n_i}\in L^X\) and \(x\in X\) we set \(f_i(\alpha _1,\ldots ,\alpha _{n_i})(x)=\bigvee \{\alpha _1(x_1)\wedge \cdots \wedge \alpha _{n_i}(x_{n_i}):(x_1,\ldots ,x_{n_i},x)\in R_i\}\) . For the 2-element lattice 2, \(2^\mathfrak {X}\) is the reduct of the familiar complex algebra \(\mathfrak {X}^+\) obtained by removing Boolean complementation from the signature. It is shown that this construction is bifunctorial and behaves well with respect to one-one and onto maps and with respect to products. When L is the reduct of a complete Heyting algebra, the operations of \(L^\mathfrak {X}\) are completely additive in each coordinate and \(L^\mathfrak {X}\) is in the variety generated by \(2^\mathfrak {X}\) . Extensions to the construction are made to allow for completely multiplicative operations defined through meets instead of joins, as well as modifications to allow for convolutions of relational structures with partial orderings. Several examples are given.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0510-3
      Issue No: Vol. 79, No. 2 (2018)
  • Axiomatisability and hardness for universal Horn classes of hypergraphs
    • Authors: Lucy Ham; Marcel Jackson
      Abstract: We consider hypergraphs as symmetric relational structures. In this setting, we characterise finite axiomatisability for finitely generated universal Horn classes of loop-free hypergraphs. An Ehrenfeucht–Fraïssé game argument is employed to show that the results continue to hold when restricted to first order definability amongst finite structures. We are also able to show that every interval in the homomorphism order on hypergraphs contains a continuum of universal Horn classes and conclude the article by characterising the intractability of deciding membership in universal Horn classes generated by finite loop-free hypergraphs.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0515-y
      Issue No: Vol. 79, No. 2 (2018)
  • Polymorphism clones of homogeneous structures: gate coverings and
           automatic homeomorphicity
    • Authors: Christian Pech; Maja Pech
      Abstract: Every clone of functions comes naturally equipped with a topology, the topology of pointwise convergence. A clone \(\mathfrak {C}\) is said to have automatic homeomorphicity with respect to a class \(\mathcal {K}\) of clones, if every clone isomorphism of \(\mathfrak {C}\) to a member of \(\mathcal {K}\) is already a homeomorphism (with respect to the topology of pointwise convergence). In this paper we study automatic homeomorphicity properties for polymorphism clones of countable homogeneous relational structures. Besides two generic criteria for the automatic homeomorphicity of the polymorphism clones of homogeneous structures we show that the polymorphism clone of the generic poset with strict ordering has automatic homeomorphicity with respect to the class of polymorphism clones of countable \(\omega \) -categorical structures. Our results extend and generalize previous results by Bodirsky, Pinsker, and Pongrácz.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0504-1
      Issue No: Vol. 79, No. 2 (2018)
  • Unique inclusions of maximal C-clones in maximal clones
    • Authors: Mike Behrisch; Edith Vargas-García
      Abstract: C-clones are polymorphism sets of so-called clausal relations, a special type of relations on a finite domain, which first appeared in connection with constraint satisfaction problems in work by Creignou et al. from 2008. We completely describe the relationship regarding set inclusion between maximal C-clones and maximal clones. As a main result we obtain that for every maximal C-clone there exists exactly one maximal clone in which it is contained. A precise description of this unique maximal clone, as well as a corresponding completeness criterion for C-clones is given.
      PubDate: 2018-04-20
      DOI: 10.1007/s00012-018-0497-9
      Issue No: Vol. 79, No. 2 (2018)
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