Subjects -> MATHEMATICS (Total: 1028 journals)
    - APPLIED MATHEMATICS (92 journals)
    - GEOMETRY AND TOPOLOGY (23 journals)
    - MATHEMATICS (729 journals)
    - MATHEMATICS (GENERAL) (45 journals)
    - NUMERICAL ANALYSIS (26 journals)
    - PROBABILITIES AND MATH STATISTICS (113 journals)

MATHEMATICS (729 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 538 Journals sorted alphabetically
Abakós     Open Access   (Followers: 2)
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg     Hybrid Journal   (Followers: 1)
Accounting Perspectives     Full-text available via subscription   (Followers: 4)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 13)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 5)
ACM Transactions on Mathematical Software (TOMS)     Hybrid Journal   (Followers: 6)
ACS Applied Materials & Interfaces     Hybrid Journal   (Followers: 38)
Acta Applicandae Mathematicae     Hybrid Journal   (Followers: 2)
Acta Mathematica Hungarica     Hybrid Journal   (Followers: 2)
Acta Mathematica Sinica, English Series     Hybrid Journal   (Followers: 5)
Acta Mathematica Vietnamica     Hybrid Journal  
Acta Mathematicae Applicatae Sinica, English Series     Hybrid Journal  
Advanced Science Letters     Full-text available via subscription   (Followers: 9)
Advances in Applied Clifford Algebras     Hybrid Journal   (Followers: 5)
Advances in Catalysis     Full-text available via subscription   (Followers: 7)
Advances in Complex Systems     Hybrid Journal   (Followers: 10)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 20)
Advances in Decision Sciences     Open Access   (Followers: 4)
Advances in Difference Equations     Open Access   (Followers: 2)
Advances in Fixed Point Theory     Open Access  
Advances in Geosciences (ADGEO)     Open Access   (Followers: 19)
Advances in Linear Algebra & Matrix Theory     Open Access   (Followers: 9)
Advances in Materials Science     Open Access   (Followers: 19)
Advances in Mathematical Physics     Open Access   (Followers: 5)
Advances in Mathematics     Full-text available via subscription   (Followers: 19)
Advances in Numerical Analysis     Open Access   (Followers: 4)
Advances in Operations Research     Open Access   (Followers: 13)
Advances in Operator Theory     Hybrid Journal  
Advances in Pure Mathematics     Open Access   (Followers: 8)
Advances in Science and Research (ASR)     Open Access   (Followers: 8)
Aequationes Mathematicae     Hybrid Journal   (Followers: 2)
African Journal of Educational Studies in Mathematics and Sciences     Full-text available via subscription   (Followers: 7)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 5)
Afrika Matematika     Hybrid Journal   (Followers: 2)
AKSIOMATIK : Jurnal Penelitian Pendidikan dan Pembelajaran Matematika     Open Access  
Al-Jabar : Jurnal Pendidikan Matematika     Open Access  
Al-Qadisiyah Journal for Computer Science and Mathematics     Open Access   (Followers: 3)
AL-Rafidain Journal of Computer Sciences and Mathematics     Open Access   (Followers: 3)
Algebra and Logic     Hybrid Journal   (Followers: 7)
Algebra Colloquium     Hybrid Journal   (Followers: 1)
Algebra Universalis     Hybrid Journal   (Followers: 2)
Algorithmic Operations Research     Open Access   (Followers: 5)
Algorithms     Open Access   (Followers: 13)
Algorithms Research     Open Access   (Followers: 1)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 8)
American Journal of Mathematical Analysis     Open Access   (Followers: 1)
American Journal of Mathematical and Management Sciences     Hybrid Journal  
American Journal of Mathematics     Full-text available via subscription   (Followers: 8)
American Journal of Operations Research     Open Access   (Followers: 7)
American Mathematical Monthly     Full-text available via subscription   (Followers: 3)
An International Journal of Optimization and Control: Theories & Applications     Open Access   (Followers: 12)
Analele Universitatii Ovidius Constanta - Seria Matematica     Open Access  
Analysis and Applications     Hybrid Journal   (Followers: 2)
Analysis and Mathematical Physics     Hybrid Journal   (Followers: 9)
Anargya : Jurnal Ilmiah Pendidikan Matematika     Open Access  
Annales Mathematicae Silesianae     Open Access  
Annales mathématiques du Québec     Hybrid Journal   (Followers: 3)
Annales Universitatis Mariae Curie-Sklodowska, sectio A – Mathematica     Open Access   (Followers: 1)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica     Open Access  
Annali di Matematica Pura ed Applicata     Hybrid Journal   (Followers: 1)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 14)
Annals of Functional Analysis     Hybrid Journal   (Followers: 2)
Annals of Mathematics     Full-text available via subscription   (Followers: 4)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 16)
Annals of PDE     Hybrid Journal  
Annals of Pure and Applied Logic     Open Access   (Followers: 4)
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   (Followers: 1)
Annals of West University of Timisoara - Mathematics and Computer Science     Open Access   (Followers: 1)
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: 3)
Applications of Mathematics     Hybrid Journal   (Followers: 2)
Applied Categorical Structures     Hybrid Journal   (Followers: 3)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 16)
Applied Mathematics     Open Access   (Followers: 7)
Applied Mathematics     Open Access   (Followers: 6)
Applied Mathematics & Optimization     Hybrid Journal   (Followers: 10)
Applied Mathematics - A Journal of Chinese Universities     Hybrid Journal   (Followers: 1)
Applied Mathematics and Nonlinear Sciences     Open Access  
Applied Mathematics Letters     Full-text available via subscription   (Followers: 1)
Applied Mathematics Research eXpress     Hybrid Journal   (Followers: 1)
Applied Network Science     Open Access   (Followers: 2)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 4)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 5)
Arab Journal of Mathematical Sciences     Open Access   (Followers: 3)
Arabian Journal of Mathematics     Open Access   (Followers: 1)
Archive for Mathematical Logic     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 4)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Armenian Journal of Mathematics     Open Access  
Arnold Mathematical Journal     Hybrid Journal   (Followers: 1)
Artificial Satellites     Open Access   (Followers: 19)
Asia-Pacific Journal of Operational Research     Hybrid Journal   (Followers: 3)
Asian Journal of Algebra     Open Access   (Followers: 1)
Asian Research Journal of Mathematics     Open Access  
Asian-European Journal of Mathematics     Hybrid Journal   (Followers: 2)
Australian Mathematics Teacher, The     Full-text available via subscription   (Followers: 7)
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)
Baltic International Yearbook of Cognition, Logic and Communication     Open Access   (Followers: 2)
Banach Journal of Mathematical Analysis     Hybrid Journal  
Basin Research     Hybrid Journal   (Followers: 6)
BIBECHANA     Open Access  
Biomath     Open Access  
BIT Numerical Mathematics     Hybrid Journal  
Boletim Cearense de Educação e História da Matemática     Open Access  
Boletín de la Sociedad Matemática Mexicana     Hybrid Journal  
Bollettino dell'Unione Matematica Italiana     Full-text available via subscription  
British Journal for the History of Mathematics     Hybrid Journal  
British Journal of Mathematical and Statistical Psychology     Full-text available via subscription   (Followers: 17)
Bruno Pini Mathematical Analysis Seminar     Open Access  
Buletinul Academiei de Stiinte a Republicii Moldova. Matematica     Open Access   (Followers: 1)
Bulletin des Sciences Mathamatiques     Full-text available via subscription   (Followers: 3)
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: 3)
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics     Open Access  
Bulletin of the Australian Mathematical Society     Full-text available via subscription   (Followers: 2)
Bulletin of the Brazilian Mathematical Society, New Series     Hybrid Journal  
Bulletin of the Iranian Mathematical Society     Hybrid Journal  
Bulletin of the London Mathematical Society     Hybrid Journal   (Followers: 3)
Bulletin of the Malaysian Mathematical Sciences Society     Hybrid Journal  
Cadernos do IME : Série Matemática     Open Access  
Calculus of Variations and Partial Differential Equations     Hybrid Journal  
Canadian Journal of Mathematics / Journal canadien de mathématiques     Hybrid Journal  
Canadian Journal of Science, Mathematics and Technology Education     Hybrid Journal   (Followers: 20)
Canadian Mathematical Bulletin     Hybrid Journal  
Carpathian Mathematical Publications     Open Access  
Catalysis in Industry     Hybrid Journal  
CEAS Space Journal     Hybrid Journal   (Followers: 6)
CHANCE     Hybrid Journal   (Followers: 5)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Chaos, Solitons & Fractals : X     Open Access   (Followers: 1)
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  
Ciencia     Open Access  
CODEE Journal     Open Access  
Cogent Mathematics     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 2)
Collectanea Mathematica     Hybrid Journal  
College Mathematics Journal     Hybrid Journal   (Followers: 3)
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 18)
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: 6)
Complex Analysis and its Synergies     Open Access   (Followers: 2)
Complex Variables and Elliptic Equations: An International Journal     Hybrid Journal  
Compositio Mathematica     Full-text available via subscription   (Followers: 1)
Comptes Rendus : Mathematique     Open Access  
Computational and Applied Mathematics     Hybrid Journal   (Followers: 3)
Computational and Mathematical Methods     Hybrid Journal  
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 1)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 11)
Computational Methods and Function Theory     Hybrid Journal  
Computational Optimization and Applications     Hybrid Journal   (Followers: 9)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 8)
Confluentes Mathematici     Hybrid Journal  
Constructive Mathematical Analysis     Open Access  
Contributions to Discrete Mathematics     Open Access  
Contributions to Game Theory and Management     Open Access  
COSMOS     Hybrid Journal   (Followers: 1)
Cross Section     Full-text available via subscription   (Followers: 1)
Cryptography and Communications     Hybrid Journal   (Followers: 10)
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  
Daya Matematis : Jurnal Inovasi Pendidikan Matematika     Open Access  
Demographic Research     Open Access   (Followers: 14)
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 33)
Desimal : Jurnal Matematika     Open Access  
Dhaka University Journal of Science     Open Access  
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 2)
Differentsial'nye Uravneniya     Open Access  
Digital Experiences in Mathematics Education     Hybrid Journal   (Followers: 2)
Discrete Mathematics     Hybrid Journal   (Followers: 8)
Discrete Mathematics & Theoretical Computer Science     Open Access   (Followers: 1)
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  
Doklady Akademii Nauk     Open Access  
Doklady Mathematics     Hybrid Journal  
Eco Matemático     Open Access  
Econometrics     Open Access   (Followers: 2)

        1 2 3 4 | Last

Similar Journals
Journal Cover
Aequationes Mathematicae
Journal Prestige (SJR): 0.517
Citation Impact (citeScore): 1
Number of Followers: 2  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1420-8903 - ISSN (Online) 0001-9054
Published by Springer-Verlag Homepage  [2468 journals]
  • Weighted Gaussian entropy and determinant inequalities

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      Abstract: We produce a series of results extending information-theoretical inequalities (discussed by Dembo–Cover–Thomas in 1988–1991) to a weighted version of entropy. Most of the resulting inequalities involve the Gaussian weighted entropy; they imply a number of new relations for determinants of positive-definite matrices. Unlike the Shannon entropy where the contribution of an outcome depends only upon its probability, the weighted (or context-dependent) entropy takes into account a ‘value’ of an outcome determined by a given weight function \({\varphi }\) . An example of a new result is a weighted version of the strong Hadamard inequality (SHI) between the determinants of a positive-definite \(d\times d\) matrix and its square blocks (sub-matrices) of different sizes. When \({\varphi }\equiv 1\) , the weighted inequality becomes a ‘standard’ SHI; in general, the weighted version requires some assumptions upon \({\varphi }\) . The SHI and its weighted version generalize a widely known ‘usual’ Hadamard inequality \({\mathrm{det}}\,{{\mathbf {C}}}\le \prod \nolimits _{j=1}^dC_{jj}\) .
      PubDate: 2022-01-22
       
  • On optimal inequalities between three-point quadratures

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      Abstract: We examine the family of all (at most) three-point symmetric quadratures on \([-1,1]\) which are exact on polynomials of order 3 to find all possible inequalities between them in the class of 3-convex functions. Next we optimise them by using convex combinations of the quadratures considered. We find the optimal quadrature and use it to construct the adaptive method of approximate integration. An effective method to estimate the error of this method is also given. It needs a considerably fewer number of subdivisions of the interval of integration than the classical adaptive methods as well as the method developed by the second-named author in his recent paper (Wa̧sowicz in Aequ Math 94(5):887–898, 2020).
      PubDate: 2022-01-17
       
  • Global forcing number for maximal matchings in corona products

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      Abstract: A global forcing set for maximal matchings of a graph \(G=(V(G), E(G))\) is a set \(S \subseteq E(G)\) such that \(M_1\cap S \ne M_2 \cap S\) for each pair of maximal matchings \(M_1\) and \(M_2\) of G. The smallest such set is called a minimum global forcing set, its size being the global forcing number for maximal matchings \(\phi _{gm}(G)\) of G. In this paper, we establish lower and upper bounds on the forcing number for maximal matchings of the corona product of graphs. We also introduce an integer linear programming model for computing the forcing number for maximal matchings of graphs.
      PubDate: 2022-01-15
       
  • Invariant vector means and complementability of Banach spaces in their
           second duals

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      Abstract: Let X be a Banach space. Fix a torsion-free commutative and cancellative semigroup S whose torsion-free rank is the same as the density of \(X^{**}\) . We then show that X is complemented in \(X^{**}\) if and only if there exists an invariant mean \(M:\ell _\infty (S,X)\rightarrow X\) . This improves upon previous results due to Bustos Domecq (J Math Anal Appl 275(2):512–520, 2002), Kania (J Math Anal Appl 445:797–802, 2017), Goucher and Kania (Studia Math 260:91–101, 2021).
      PubDate: 2022-01-11
       
  • A divided-difference characterization of polynomials over finite fields of
           characteristic two

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      Abstract: For a finite field \({\mathbb {F}}\) of characteristic 2, an integer \(n\ge 3\) , and for a function \(f : {\mathbb {F}}\rightarrow {\mathbb {F}}\) , if there is a function \(h: {\mathbb {F}} \rightarrow {\mathbb {F}}\) such that the divided difference \(f[x_1, \dots , x_n]\) on any n distinct elements of \({\mathbb {F}}\) satisfies \(f[x_1,\ldots ,x_n] = h(x_1 +\cdots + x_n)\) , then f is a polynomial of degree at most n over \({\mathbb {F}}\) . This makes earlier work of Davies and Rousseau complete.
      PubDate: 2022-01-09
       
  • Axiomatic characterization of the $$\chi ^{2}$$ χ 2 dissimilarity
           measure

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      Abstract: We axiomatically characterize the \(\chi ^{2}\) dissimilarity measure. To this end, we solve a new generalization of a functional equation discussed in Aczel (Lectures on functional equations and their applications. Academic Press, 1966).
      PubDate: 2022-01-09
       
  • Sections in functional equations: stability and hyperstability

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      Abstract: The section method provides a technique for solving certain functional equations with the help of their characteristic equations. We prove here that a large class of such equations are functionally stable in the hypothesis of the stability of the corresponding characteristic equations. We use these results to solve two equations that have composite functions as solutions and to give classes of control functions that ensure their generalized stability.
      PubDate: 2022-01-04
       
  • A Levi–Civita functional equation on semigroups

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      Abstract: Let S be a semigroup. We describe the solutions \(f,g:S \rightarrow \mathbb {C}\) of the functional equation $$\begin{aligned} f(xy) = f(x)g(y) + g(x)f(y) - g(x)g(y), \ x,y \in S, \end{aligned}$$ in terms of multiplicative functions on S and solutions of the particular case $$\begin{aligned} \varphi (xy) = \varphi (x)\chi (y) + \varphi (y)\chi (x), \ x,y \in S, \end{aligned}$$ of the sine addition law in which \(\chi :S \rightarrow \mathbb {C}\) is a non-zero multiplicative function and \(\varphi :S \rightarrow \mathbb {C}\) .
      PubDate: 2022-01-04
       
  • On the extremal compatible linear connection of a generalized Berwald
           manifold

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      Abstract: Generalized Berwald manifolds are Finsler manifolds admitting linear connections such that the parallel transports preserve the Finslerian length of tangent vectors (compatibility condition). It is known (Vincze in J AMAPN 21:199–204, 2005) that such a linear connection must be metrical with respect to the averaged Riemannian metric given by integration of the Riemann-Finsler metric on the indicatrix hypersurfaces. Therefore the linear connection (preserving the Finslerian length of tangent vectors) is uniquely determined by its torsion. If the torsion is zero then we have a classical Berwald manifold. Otherwise, the torsion is some strange data we need to express in terms of the intrinsic quantities of the Finsler manifold. The paper presents the idea of the extremal compatible linear connection of a generalized Berwald manifold by minimizing the pointwise length of its torsion tensor. It is uniquely determined because the number of the Lagrange multipliers is equal to the number of the equations for the compatibility of the linear connection with the Finslerian metric. Using the reference element method, the extremal compatible linear connection can be expressed in terms of the canonical data as well. It is an intrinsic algorithm to check the existence of compatible linear connections on a Finsler manifold because it is equivalent to the existence of the extremal compatible linear connection.
      PubDate: 2021-12-29
       
  • Eri Jabotinsky, mathematician and politician: a short biography

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      Abstract: Despite the fact that Eri Jabotinsky (1910–1969) published only few (i.e. fourteen) mathematical papers, some of them had a remarkable influence in iteration theory. But also his life was remakable. Eri was the son of the famous Zionist Revisionist leader Vladimir Ze’ev Jabotinsky. Eri Jabotinsky was active in the Zionist movement and later as parlamentarian in the Knesset. Here we give an outline of his live and a complete list of his publications.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00779-w
       
  • k-Valued Wilson functions

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      Abstract: We study k-valued solutions of Wilson’s \(\mu \) -functional equation on semigroups and monoids where k is an algebraically closed field of characteristic \(\ne 2\) . As applications we solve the functional equation on some finite groups and find the continuous, complex valued solutions on compact groups.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00784-z
       
  • Moment functions and exponential monomials on commutative hypergroups

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      Abstract: The purpose of this paper is to prove that if on a commutative hypergroup an exponential monomial has the property that the linear subspace of all sine functions in its variety is one dimensional, then this exponential monomial is a linear combination of generalized moment functions.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00827-5
       
  • Continuous solutions to two iterative functional equations

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      Abstract: Based on iteration of random-valued functions we study the problem of solvability in the class of continuous and Hölder continuous functions \(\varphi \) of the equations $$\begin{aligned} \varphi (x)=F(x)-\int _{\Omega }\varphi \big (f(x,\omega )\big )P(d\omega ),\\ \varphi (x)=F(x)+\int _{\Omega }\varphi \big (f(x,\omega )\big )P(d\omega ), \end{aligned}$$ where P is a probability measure on a \(\sigma \) -algebra of subsets of \(\Omega \) .
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00794-x
       
  • Interview with Ludwig Reich

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      Abstract: On the occasion of his 80th birthday, Ludwig Reich, editor-in-chief of Aequationes Mathematicae from 1996 to 2008, gave an interview conducted via Zoom. This paper presents his answers to several questions regarding his education and academic life.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00853-3
       
  • The solvability cardinal of the class of polynomials

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      Abstract: Let G be an Abelian group, and let \({{\mathbb {C}}}^G\) denote the set of complex valued functions defined on G. A map \(D: {{\mathbb {C}}}^G \rightarrow {{\mathbb {C}}}^G\) is a difference operator, if there are complex numbers \(a_i\) and elements \(b_i \in G\) \((i=1,\ldots , n)\) such that \((Df)(x)=\sum _{i=1}^n a_i f(x+b_i)\) for every \(f\in {{\mathbb {C}}}^G \) and \(x\in G\) . By a system of difference equations we mean a set of equations \(\{ D_i f=g_i : i\in I\}\) , where I is an arbitrary set of indices, \(D_i\) is a difference operator and \(g_i \in {{\mathbb {C}}}^G\) is a given function for every \(i\in I\) , and f is the unknown function. The solvability cardinal \(\mathrm{sc} \,({{\mathcal {F}}})\) of a class of functions \({{\mathcal {F}}} \subset {{\mathbb {C}}}^G\) is the smallest cardinal number \(\kappa \) with the following property: whenever S is a system of difference equations on G such that each subsystem of S of cardinality \(<\kappa \) has a solution in \({{\mathcal {F}}}\) , then S itself has a solution in \({{\mathcal {F}}}\) . The behaviour of \(\mathrm{sc} \,({{\mathcal {F}}})\) is rather erratic, even for classes of functions defined on \({{\mathbb {R}}}\) . For example, \(\mathrm{sc} \,({{\mathbb {C}}}[x])=3\) , but \(\mathrm{sc} \,({\mathcal {TP}}) =\omega _1\) , where \({\mathcal {TP}}\) is the set of trigonometric polynomials; \(\mathrm{sc} \,({{\mathbb {C}}}^{{\mathbb {R}}})=\omega \) , but \(\mathrm{sc} \,({\mathcal {DF}}) =(2^\omega )^+\) , where \({\mathcal {DF}}\) is the set of functions having the Darboux property. Our aim is to determine or to estimate the solvability cardinal of the class of polynomials defined on \({{{\mathbb {R}}}}^n\) , on normed linear spaces and, in general, on topological Abelian groups. Let
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00818-6
       
  • Quasi-Cauchy quotients and means

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      Abstract: Let \(I\subset {\mathbb {R}}\) be an interval that is closed under addition, and \( k\in {\mathbb {N}}\) , \(k\ge 2\,\) . For a function \(f:I\rightarrow \left( 0,\infty \right) \) such that \(F\left( x\right) :=\frac{f\left( kx\right) }{ kf\left( x\right) }\) is invertible in I, the k-variable function \( M_{f}:I^{k}\rightarrow I,\) $$\begin{aligned} M_{f}\left( x_{1},\ldots ,x_{k}\right) :=F^{-1}\left( \frac{f\left( x_{1}+\cdots +x_{k}\right) }{f\left( x_{1}\right) +\cdots +f\left( x_{k}\right) } \right) , \end{aligned}$$ is a premean in I,  and it is referred to as a quasi Cauchy quotient of the additive type of generator f. Three classes of means of this type generated by the exponential, logarithmic, and power functions, are examined. The suitable quasi Cauchy quotients of the exponential types (for continuous additive, logarithmic, and power functions) are considered. When I is closed under multiplication, the quasi Cauchy quotient means of logarithmic and multiplicative type are studied. The equalities of premeans within each of these classes are discussed and some open problems are proposed.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00856-0
       
  • Commutants of the multidimensional Jennings group

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      Abstract: The d-dimensional analogue \({\mathcal J}^{(d)}(\mathbf{k})\) of the Jennings group ( \(d=1\) ) of substitutions of mappings of formal power series with coefficients in an arbitrary field \(\mathbf{k}\) is defined and studied. More precisely, we find the commutants in the group \({\mathcal J}^{(d)}(\mathbf{k})\) for \(d\ge 2\) . The case \(d=1\) was done before.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00783-0
       
  • Linear functional equations and their solutions in generalized Orlicz
           spaces

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      Abstract: Assume that \(\Omega \subset \mathbb {R}^k\) is an open set, V is a real separable Banach space and \(f_1,\ldots ,f_N :\Omega \rightarrow \Omega \) , \(g_1,\ldots , g_N:\Omega \rightarrow \mathbb {R}\) , \(h_0:\Omega \rightarrow V\) are given functions. We are interested in the existence and uniqueness of solutions \(\varphi :\Omega \rightarrow V\) of the linear equation \(\varphi =\sum _{k=1}^{N}g_k\cdot (\varphi \circ f_k)+h_0\) in generalized Orlicz spaces.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00851-5
       
  • Some remarks on the stability of the Cauchy equation and completeness

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      Abstract: It was proved in Forti and Schwaiger (C R Math Acad Sci Soc R Can 11(6):215–220, 1989), Schwaiger (Aequ Math 35:120–121, 1988) and with different methods in Schwaiger (Developments in functional equations and related topics. Selected papers based on the presentations at the 16th international conference on functional equations and inequalities, ICFEI, Bȩdlewo, Poland, May 17–23, 2015, Springer, Cham, pp 275–295, 2017) that under the assumption that every function defined on suitable abelian semigroups with values in a normed space such that the norm of its Cauchy difference is bounded by a constant (function) is close to some additive function, i.e., the norm of the difference between the given function and that additive function is also bounded by a constant, the normed space must necessarily be complete. By Schwaiger (Ann Math Sil 34:151–163, 2020) this is also true in the non-archimedean case. Here we discuss the situation when the bound is a suitable non-constant function.
      PubDate: 2021-12-01
      DOI: 10.1007/s00010-021-00804-y
       
  • K-subadditive and K-superadditive set-valued functions bounded on
           “large” sets

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      Abstract: We prove that every K–subadditive set–valued map weakly K–upper bounded on a “large” set (e.g. not null–finite, not Haar–null or not a Haar–meager set), as well as any K–superadditive set–valued map K–lower bounded on a “large” set, is locally K–lower bounded and locally weakly K–upper bounded at every point of its domain.
      PubDate: 2021-10-07
      DOI: 10.1007/s00010-021-00850-6
       
 
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