In mathematics, a functional equation is, in the broadest meaning, an equation in which one or several functions appear as unknowns. So, differential equations and integral equations are functional equations. However, a more restricted meaning is often used, where a functional equation is an equation that relates several values of the same function. For example, the logarithm functions are essentially characterized by the logarithmic functional equation
Fundamenta Mathematicae is a peer-reviewed scientific journal of mathematics with a special focus on the foundations of mathematics, concentrating on set theory, mathematical logic, topology and its interactions with algebra, and dynamical systems.
Inventiones Mathematicae is a mathematical journal published monthly by Springer Science+Business Media. It was established in 1966 and is regarded as one of the most prestigious mathematics journals in the world. The current (2023) managing editors are Jean-Benoît Bost and Wilhelm Schlag.
In number theory, Fermat's Last Theorem states that no three positive integers a, b, and c satisfy the equation an + bn = cn for any integer value of n greater than 2. The cases n = 1 and n = 2 have been known since antiquity to have infinitely many solutions.
János Dezső Aczél, also known as John Aczel, was a Hungarian-Canadian mathematician, who specialized in functional equations and information theory.
Acta Scientiarum Mathematicarum is a Hungarian mathematical journal published by the János Bolyai Mathematical Institute. It was established by Alfréd Haar and Frigyes Riesz in 1922. The current editor-in-chief is Lajos Molnár. The journal is abstracted and indexed in Scopus and Zentralblatt MATH.
Themistocles M. Rassias is a Greek mathematician, and a professor at the National Technical University of Athens, Greece. He has published more than 300 papers, 10 research books and 45 edited volumes in research Mathematics as well as 4 textbooks in Mathematics for university students. His research work has received more than 19,000 citations according to Google Scholar and more than 5,800 citations according to MathSciNet. His h-index is 49. He serves as a member of the Editorial Board of several international mathematical journals.
Acta Applicandae Mathematicae is a peer-reviewed mathematics journal published by Springer. Founded in 1983, the journal publishes articles on applied mathematics.
Queueing Systems is a peer-reviewed scientific journal covering queueing theory. It is published by Springer Science+Business Media. The current editor-in-chief is Sergey Foss. According to the Journal Citation Reports, the journal has a 2019 impact factor of 1.114.
The stability problem of functional equations originated from a question of Stanisław Ulam, posed in 1940, concerning the stability of group homomorphisms. In the next year, Donald H. Hyers gave a partial affirmative answer to the question of Ulam in the context of Banach spaces in the case of additive mappings, that was the first significant breakthrough and a step toward more solutions in this area. Since then, a large number of papers have been published in connection with various generalizations of Ulam's problem and Hyers's theorem. In 1978, Themistocles M. Rassias succeeded in extending Hyers's theorem for mappings between Banach spaces by considering an unbounded Cauchy difference subject to a continuity condition upon the mapping. He was the first to prove the stability of the linear mapping. This result of Rassias attracted several mathematicians worldwide who began to be stimulated to investigate the stability problems of functional equations.
István Fenyő was a Hungarian mathematician, whose first name was also known as "Étienne, Stefan, Stephan or Stephen". He was best known for his publications of applied mathematics. He made significant contributions to analysis, algebra, geometry, integral equations and many other fields that pertain to his interests.
Jack Kenneth Hale was an American mathematician working primarily in the field of dynamical systems and functional differential equations.
Combinatorics, Probability and Computing is a peer-reviewed scientific journal in mathematics published by Cambridge University Press. Its editor-in-chief is Béla Bollobás.
The European Journal of Operational Research (EJOR) is a peer-reviewed academic journal in operations research. It was founded in 1977 by the Association of European Operational Research Societies, and is published by Elsevier, with Roman Słowiński as its Co-ordinating Editor. Currently, it publishes at a rate of 24 issues per annual volume, with approximately 250 pages per issue.
Graphs and Combinatorics is a peer-reviewed academic journal in graph theory, combinatorics, and discrete geometry published by Springer Japan. Its editor-in-chief is Katsuhiro Ota of Keio University.
4OR - A Quarterly Journal of Operations Research is a peer-reviewed scientific journal that was established in 2003 and is published by Springer Science+Business Media. It is a joint official journal of the Belgian, French, and Italian Operations Research Societies. The journal publishes research papers and surveys on the theory and applications of Operations Research. The Editors-in-chief are Yves Crama, Michel Grabisch, and Silvano Martello.
The Journal of Functional Analysis is a mathematics journal published by Elsevier. Founded by Paul Malliavin, Ralph S. Phillips, and Irving Segal, its editors-in-chief are, as of April 2024, Guido De Philippis, Alexandru D. Ionescu and Stefaan Vaes.
Journal of Classification is a peer-reviewed academic journal published by Springer Science+Business Media. It is the official journal of The Classification Society. The journal publishes three issues a year on topics in the field of classification, numerical taxonomy, multidimensional scaling and other ordination techniques, cluster analysis, tree structures and other network models. Each issue typically comprises four sections: articles, short notes and comments, software abstracts, and book reviews.
Peter Bernd Schneider is a German mathematician, specializing in the p-adic aspects of algebraic number theory, arithmetic algebraic geometry, and representation theory.
Jean Guy Dhombres is a French mathematician, historian of mathematics and the mathematical sciences, and biographer of Lazare Carnot.
