György Targonski

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György Targonski (born March 28, 1928 in Budapest ; † January 10, 1998 ) was a Hungarian-German mathematician and theoretical physicist . Since 1974 he has held a chair for applied mathematics at the Philipps University of Marburg .

Life

Childhood and studies

Targonski was born in Budapest in early spring 1928 as the son of the Polish physicist Anton Targoński and the Hungarian actress Rózsa Simonovits and spent a large part of his childhood in Berlin . Since his father, who was a Russian citizen and dealt with problems of the Brownian movement , cinema technology and patent law , neither spoke Hungarian nor his mother Polish, György's parents spoke French. Remarkably, however, they communicated with their son in German. Targonski, who was to learn a few more languages ​​in the course of his life, is said to have later often cited this curiosity as the reason why his French never reached a really high level.

His father died when György was only eight years old. He promised his father on his deathbed that he would take care of his mother while she was alive. Targonski was to keep this promise, from that day on for almost 60 years.

When life in Nazi Germany became more and more difficult, his mother moved with him back to his hometown in 1938. Only now did he learn the Hungarian language. When he was confined to bed for about ten months as a child because of a form of tuberculosis , he literally devoured the novels by Mór Jókai , which he read completely in their original language, which ultimately made Hungarian his native language.

In 1947 Targonski began to study mathematics at the traditional Péter Pázmány University (since 1950: Eötvös Loránd University ) after graduating from Verboczy Gimnazium , from which he graduated in 1951 with a state diploma. When he was a student, greats such as the Fourier analyst Leopold Fejér , the functional analyst Frigyes Riesz , the graph theorist Pál Turán , the geometrician György Hajós and the logician Rózsa Péter taught in Budapest . Targonski's work Az iteráziószámításról (roughly: “On the Calculus of Iteration” ), his first unofficial publication, won a prize in a Hungarian mathematics competition in 1951.

Wandering years

After completing his studies, Targonski initially worked as an assistant and lecturer at the Technical University of Budapest , where he completed his dissertation Vegtelen sorozatok az iteracióelmeletben (Infinite Rows in Iteration Theory ) in 1955 , which his professor, Béla Szőkefalvi-Nagy , recognized, but should do not come to the award of the doctorate.

The suppression of the Hungarian people's uprising , which began on October 23, 1956, forced Targonski to leave his home country. On November 13th of that year he, his future wife Jolán Margit Horváth and his mother boarded a train going “west” that took them to a small town near Lake Neusiedl . From there they walked towards the border, accompanied by a group of young miners from Tatabánya . When there was only a small canal left to cross at dawn, the Hungarian border guards patrolling there helped them. From Austria it went on to Switzerland.

Through the mediation of the mathematician Beno Eckmann , who would later appear as his sponsor, he got a job at the Swiss Federal Institute of Technology in Zurich (ETH). On December 15, 1956, Targonski married his wife Jolán.

This was followed by stays in Cambridge , at Queen Mary College in London and in Geneva ( CERN and the Institute for Theoretical Physics of the university there ), until he was finally awarded a PhD in 1963 at the University of Cambridge as a theoretical physicist with the thesis Contributions to the theory of Scattering .D. PhD. In the same year he moved to Fordham University in New York , where he initially taught as an Associate Professor and was made Full Professor of Mathematics in 1966 .

When he received a call to the chair for applied mathematics at the Philipps University in Marburg in 1974 , Targonski, who was an enthusiastic supporter of the European idea, followed suit. In 1977 he obtained German citizenship. In 1982 he moved to Frankfurt. Not only because he was used to being a “city dweller”, but also because he was able to visit his mother, who was living in Geneva at the time, more quickly and more often.

Health problems

Overall, Targonski should spend more time or work in Marburg than anywhere else, including Budapest. He published a little less than in the years immediately before, but accompanied a large number of diploma and doctoral students. In 1981 he brought out his book "Topics in Iteration Theory" which, in addition to his own work and that of other established researchers, also contained various research results from his students, especially doctoral and diploma students.

Also in 1981, Targonski suffered a severe stroke, which from then on severely impaired him and made him dependent on walking aids. He continued to take part in lectures, but from the summer semester of 1989 onwards he limited himself to more in-depth courses on his subject areas and mathematics for natural scientists , which he was able to hold on the Lahn Mountains. The usual cycles, in which university lecturers, starting from the basic lectures, through to intermediate to in-depth lectures and advanced seminars, accompany courses over almost the entire course of their studies, could no longer be completed due to a lack of mobility, since the basic lectures, which were also compulsory for physics students, usually had one almost three-digit audience numbers were held in the lecture hall building in downtown Marburg, five kilometers away.

Targonski and his wife, Jolán Targonski, who holds a doctorate in computer science and maths, experienced the political changes that began in 1988 with great joy. Nevertheless, he was not spared a second stroke, which befell him at the end of 1992, shortly after the death of his mother at the proud age of 100 years.

After he retired in 1993, Targonski finally passed away at the beginning of 1998 after years of severe health problems.

Trivia

Targonski spoke German and English as well as Russian at a very high level, but with a characteristic Hungarian accent. And although he had spent large parts of his childhood and the last two and a half decades in Germany, his internal notes on event preparations were always in Hungarian. He was known as a very educated and Christian person who especially developed very own forms of didactics. He used to spice up his mathematical lectures with plenty of anecdotes.

In the winter of 1998, when he had just passed away, a young man is said to have come to the office of the mathematics department with the request to speak to Mr. Targonski. He used to live in the neighborhood of the Targonskis and the professor always patiently and sensitively helped him when he had problems with mathematics as a student. Now he wanted to proudly and gratefully show him his fresh dissertation in the same subject.

Work area

Even as a schoolboy Targonski had the problem of iteration of linear operators , that is the repeated application of a function on their own value range fascinated. His first publications in 1952 and 1953 consequently dealt with problems of iteration.

In his early years of wandering from 1956 to about 1963, he worked a lot on operator theory associated with scattering sproblemen in physics, which is more like the functional analysis is attributable.

Targonski's actual life's work, however, lies in the area of functional equations and iteration theory . He had coined the second term himself for the first time, and his book "Topics in Iteration Theory" in 1981 was the first monograph on the subject. Targonski examined topics such as iterative roots of functions and the importance of fixed points as well as the existence of cycles of different lengths for the behavior with advancing iteration. This also includes the famous sentence “Period Three Implies Chaos ” by the American mathematicians Tien-Yien Li and James Yorke , which is basically just a corollary from the Sarkovskii theorem, which was about a decade older , but was found without knowledge of it. In general, Targonski dealt intensively with the mathematical “parallel worlds” that had ruled for decades without specialist communication between mathematical research in the West and that of the Eastern Bloc.

In addition to his regular, originally two-semester lecture Iteration Theory and Functional Equations and the very applied lecture Discrete Dynamics and Pseudostochastic Phenomena , which also falls directly into his field of research , Targonski also read ordinary differential equations and dynamic systems , cycles for function theory , topological dynamics and trigonometric series . In addition, there were basic lectures on analysis and, later, mathematics for natural scientists instead .

student

A total of four scientists and two women graduated from Targonski between 1978 and 1988:

  • Gisela Zimmermann: On the existence of iterative roots of images , 1978.
  • Uhland Burkart: For the characterization of discrete dynamic systems , 1978.
  • Reinhard Graw: About the orbit structure of continuous mappings , 1978.
  • Sabine Müllenbach: Contribution a Vetude de Viteration fractionnaire des endomorphismes , 1983.
  • Jürgen Weitkämper: Conjugation of quadratic polynomials, 1988.
  • Reginald Ferber: Spatial and temporal regularities of cellular automata , 1988.

Targonski's last two doctoral students became professors themselves, albeit at universities of applied sciences and each in the field of computer science . Weitkämper teaches and researches today (2015) at Jade University in Oldenburg and Ferber at Darmstadt University .

Publications

  • György I. Targonski: Az iteraziószamftasról [On the Iteration Calculus]. Budapest University (unpublished; 1951).
  • György I. Targonski: Ket formula a geodeziai alapvonalhosszusagok redukciójahoz [Two Formulas for the Reduction of Basic Distances in Geodesy]. Hungarian Institute of Cartography, Budapest (unpublished; 1952).
  • György I. Targonski: Representation of functions through chain rows . Publ. Math. Debrecen 2 (1952), pp. 286-290.
  • Z. Fekete, György I. Targonski: Kombinatorika [Combinatorics]. Tankonyvkiado, Budapest (1952).
  • György I. Targonski: An always Convergent Iteration Process . Acta Math. Acad. Sci. Hungar. 4, pp. 119-126 (1953).
  • Z. Bognar, György I. Targonski: About the determination of conjugated harmonic functions . Publ. Math. Debrecen 3 (1954); Pp. 215-216.
  • György I. Targonski: Vegtelen sorozatok az iteracióelmeletben [Infinite Series in the Theory of Iteration]. Thesis for the Candidature of Sciences. Budapest University (unpublished; 1955)
  • György I. Targonski: Interpolation through series of iterated functions . Commentationes Physico-Mathematicae 20, 9; Helsinki (1957); Pp. 3-12.
  • György I. Targonski: Approximation of velocity-dependent potentials by separable kernels . II Nuovo Cimento, Ser. X, 4 (1959); Pp. 1093-1101.
  • György I. Targonski: On Substitution Operators. I. A Summation Method . Technical Report No. AF 61 (052) - 320th Air Force Office of Scientific Research, Queen Mary College, University of London (unpublished; 1960).
  • A. Martin, György I. Targonski: On the uniqueness of a potential fitting a scattering amplitude at a given energy . II Nuovo Cimento, Ser. X, 20 (1961); Pp. 1182-1190.
  • B. Misra, D. Speiser, György I. Targonski: Integral representation of operators in scattering theory . Helvetica Phys. Acta 35 (1962); Pp. 329-330.
  • György I. Targonski: Contributions to the theory of scattering . Ph.D. thesis, Cambridge (1963).
  • György I. Targonski: On a theory of linear functional equations . Proc. 14th scand. Math. Congress, Copenhagen (1964).
  • Schröder's equation and a generalization of Chebyshev polynomials . Trans. New York Acad. Sci. 27 (1965), pp. 600-605.
  • György I. Targonski: A Bibliography on Functional Equations with Abstracts . US Air Force Office of Scientific Research Report, New York (unpublished; 1964).
  • György I. Targonski: Seminar on Functional Operators and Equations . Part I and II. Swiss Federal Institute of Technology, Zurich (1966).
  • György I. Targonski: Convergence theorems derived from the theory of Carleman integral operators . Comp. Math. Vol. 18, Fasc. 1,2 (1967), pp. 148-154.
  • György I. Targonski: On the classification of the linear operators on function algebras . Math. Zeitschr. 97, pp. 238-250 (1967).
  • György I. Targonski: Seminar on Functional Operators and Equations . Lecture Notes in Mathematics No. 33.Springer, Berlin, Heidelberg, New York (1967). ISBN 978-3-642-55859-7
  • György I. Targonski: A short survey of some recent results on integral operators . Nat. Science Found. Grant No. GP. 8757 (unpublished; 1968).
  • M. Schreiber, György I. Targonski: Carleman and semi-Carleman operators . Proc. Amer. Math. Soc. 24: 293-299 (1970).
  • György I. Targonski: Linear Endomorphisms of Function Algebras and Related Functional Equations . Indiana Univ. Math. Journ. 1970, 20, pp. 579-589.
  • Marek Kuczma (1935–1991; Jagiellonian University ), György I. Targonski: On a Pre-Schröder equation . Bull. Acad. Polon. Sci., Ser. sci. math. astr. phys. 18 (1970), pp. 721-724.
  • György I. Targonski: Problem (P63) . Aequationes Math. 4 (1970), p. 251.
  • György I. Targonski: About the linear functional equation of the first order . Jber. German. Math Association. 73, pp. 101-110 (1971).
  • György I. Targonski: Characterization of operators by functional equations . Demonstratio Math. 6 (1973), pp. 861-870.
  • György I. Targonski: An iteration theoretical approach to the concept of time . Proceedings of the International Conference on Point Mapping and its Applications, Toulouse, September 10-14, 1973. CNRS 1976, pp. 245-257.
  • György I. Targonski: Orbit properties of functions and "Pre - Abel" equations . Ann. Pole. Math. 33: 49-55 (1977).
  • György I. Targonski: Some applications of Kuratowski's concept of orbit . Ber. the math.-stat. Sect. Research Center Graz, Ber. No. 83, (1978).
  • György I. Targonski: On orbit theory and some of its applications . Zeszyty Nauk. Akad. Górn.-Hutniczej im. St. Staszica No. 764, Mat.-Fiz.-Chem. 43: 7-14 (1980).
  • György I. Targonski: Topics in Iteration Theory . Vandenhoeck and Rupprecht, Göttingen (1981). ISBN 3-525-40146-9
  • György I. Targonski: Unsolved problems in iteration theory . In: Theory de l'lteration et ses Applications , Toulouse, May 17-22, 1982. Editions du center national se la recherche scientifique (1982) pp. 23-32.
  • György I. Targonski: New directions and open problems in iteration theory . Ber. math. - stat. Section Forschungsgesellschaft Joanneum , Graz, No. 229 (1984), pp. 48–51
  • György I. Targonski: Iteration theory between functional equations and dynamics . Yearbook Overviews Mathematics (1985), pp. 9–28.
  • György I. Targonski: Embedding of discrete dynamical systems . In: Demongeot, J .; Goles, N .; Thuente, M. (Editor): Dynamical Systems and Cellular Automata . Academic Press, London, San Diego, New York, Boston, Sydney, Tokyo, Toronto, 1985, pp. 65-72.
  • Marek Cezary Zdun (* 1947, Pedagogical University Krakow ), György I. Targonski: Generators and co-generators of substitution semi-groups . Annal. Math. Siles. 1 (13): 169-174 (1985).
  • György I. Targonski: Phantom Iterates of Continuous Functions , in "Iteration Theory and Its Functional Equations", R. Liedl, L. Reich and G. Targonski ed. Springer Lecture Notes in Mathematics No. 1163 (1985), p. 196– 202.
  • György I. Targonski, Marek C. Zdun: Substitution Operators on LP-Spaces and their Semigroups . Mathematical-statistical section, Joanneum Research Association , Graz. Report No. 283 (1987), pp. 1-55.
  • Reginald Ferber, György Targonski and Jürgen Weitkämper: Fractional Time States of Cellular Automata , in: Proceedings of ECIT 89 Singapore . World Scientific (1991)
  • György I. Targonski: On composition operators . Zesz. Nauk. Pole. SI. No. 1070. Seria: Matematyka-Fizyka 64 (1991), pp. 229-234.
  • György I. Targonski: On a class of phantom fractional iterates . In ECIT 91 , pp. 295-304.
  • György I. Targonski: Functional equations connected with phantom iterates . Opuscula Math. 14: 179-182 (1994).
  • György I. Targonski: Progress of iteration theory since 1981 . Aeq. Math. 50 (1995), pp. 50-72 (§ 5.).
  • Proceedings of the ECIT98. Annales Mathematicae Silesianae 13, Katowice (1999).

Footnotes

  1. ↑ See Choczewski / J. Targonski 1999
  2. ↑ See Choczewski / J. Targonski 1999 p. 2
  3. ↑ Targonski read the cycle Analysis I to III last from the summer semester 1985 to the summer semester 1986, cf. Estate of György I. Targonski
  4. ↑ See the estate of György I. Targonski
  5. ↑ See Reich et al , p. 19 or (original) 46
  6. ↑ See Choczewski / J. Targonski 1999 , p. 10 below

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personal data
SURNAME Targonski, György
BRIEF DESCRIPTION Hungarian-German mathematician
DATE OF BIRTH March 28, 1928
PLACE OF BIRTH Budapest
DATE OF DEATH January 10, 1998