Sergiy Gefter

Mathematical Division Department of Function Theory

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine

47 Nauky ave. Kharkiv, 61103, UKRAINE

Date of Birth:

 

May 17, 1961

 

 

Citizenship:

 

Ukrainе

 

 

Education:

 

M.S.

 

Faculty of Mechanics and Mathematics, Kharkiv State University, June, 1983; Title: "Property T and full factors of types III1". Supervisor V. Ya. Golodets


Ph.D.

 

Kharkiv State University, October 1987.  Title: "Property T in the orbit theory and in the von Neumann algebras". Supervisor V. Ya. Golodets

Permanent Positions:

Assistant professor, School of Mathematics and Mechanics Kharkiv State University, January 1987 - October 1993

Associate professor, School of Mathematics and Computer Sciences, V.N. Karazin Kharkiv National University, October 1993 - October 2022

Acting as Head of the Department of Fundamental Mathematics, School of Mathematics and Computer Sciences, V.N. Karazin Kharkiv National University, October 2022 – present time

Senior Research Fellow, the Department of Function Theory of the B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Kharkiv, January 2001 – April 2005

Senior Research Fellow, the Department of Function Theory of the B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Kharkiv, May 2025 – present time

 

 

Research interests:

Linear differential and difference equations in Banach and topological vector spaces, linear differential and difference equations over commutative rings, linear and nonlinear partial differential equations

Scopus Author ID: 6506698897 https://mathscinet.ams.org/mathscinet/MRAuthorID/218243

https://orcid.org/0000-0001-5301-5087

Participation in research funded by grants

Grant of NATIONAL RESEARCH FOUNDATION OF UKRAINE (2020-2021)

U.S. Civilian Research and Development Foundation (CRDF) grant UM1-2546-KH-03 (2004-2005)

CRDF grant UM1-2092 (2001-2002)

INTAS grant 97-1843

Long-term ISF (International Science Foundation, G.Soros) Grant U2B000 (1993-1995)


Recent articles:
  1. S.L. Gefter, A.L. Piven’, Partial Differential Equations in Module of Copolynomials over a Commutative Ring. Journal of Mathematical Physics, Analysis, Geometry2025, vol. 18, Issue1, р. 56–83. https://doi.org/10.15407/mag21.01.03
  2. S.L. Gefter, A.L. Piven’, Some class of nonlinear partial differential equations in the ring of copolynomials over a commutative ring. Front. Appl. Math. Stat. 2024, 10:1466569. https://doi.org/10.3389/fams.2024.1466569
  3. S. Gefter, A.Goncharuk, A. Piven'. Implicit Linear First Order Difference Equations Over Commutative Rings, Springer Nature Switzerland AG, S. Elaydi et al. (eds.), Advances in Discrete Dynamical Systems, Difference Equations and Applications, Springer Proceedings in Mathematics & Statistics, 2023, pp. 199-216. https://link.springer.com/chapter/10.1007/978-3-031-25225-9_10
  4. Hefter, S.L., Goncharuk, A.B. Linear Differential Equation with Inhomogeneity in the Form of a Formal Power Series Over a Ring with Non-Archimedean Valuation. Ukr Math J 74, 1668–1685 (2023). https://link.springer.com/article/10.1007/s11253-023-02163-0
  5. Hefter, S.L., Piven’, O.L. Infinite-Order Differential Operators in the Module of Formal Generalized Functions and in a Ring of Formal Power Series. Ukr Math J 74, 896–915 (2022). https://link.springer.com/article/10.1007/s11253-022-02116-z
  6. S.L. Gefter, A.L. Piven’, Implicit Linear Nonhomogeneous Difference Equation over ℤ with a Random Right-Hand Side, Journal of Mathematical Physics, Analysis, Geometry, 2022, vol. 18, Issue 1, 105–117. https://jmag.ilt.kharkov.ua/jmag/pdf/18/jm18-0105e.pdf
  7. S.L. Gefter, A.L. Piven’, Linear Partial Differential Equations in Module of Formal Generalized Functions over Commutative Ring, Journal of Mathematical Sciences (United States), 2021, vol. 257, 579–596. https://link.springer.com/article/10.1007/s10958-021-05505-0
  8. Gefter, S.L., Piven’, L. Implicit Linear Differential-Difference Equations in the Module of Formal Generalized Functions over a Commutative Ring. J. Math. Sci. 255, 409–422 (2021). https://link.springer.com/article/10.1007/s10958-021-05381-8
  9. Gefter, S., Piven, A. Initial problem for a nonhomogeneous linear differential-difference equation in a Banach space for a class of exponential type entire functions. European Journal of Mathematics 6, 197–207 (2020). https://doi.org/10.1007/s40879-019-00314-x
  10. Gefter, S.L., Piven, A.L. Formal Functional Calculus for Weakly Locally Nilpotent Operators in Fréchet Spaces. J Math Sci 247, 865–876 (2020). https://doi.org/10.1007/s10958-020-04842-w
Recent CONFERENCES 
  1. S. Gefter, R. Skurikhin, Categorical Version of Shilov’s Theorem on Closed Equivalence Relations, “Algebraic and geometric methods of analysis”, May 26-29,2025, Odesa, Ukraine, p. 103, https://www.imath.kiev.ua/~topology/conf/agma2025/agma2025-theses.pdf
  2. Gefter S., Piven’ O., Nonlinear partial differential equations in module of copolynomials over a commutative ring, Міжнародна конференція, присвячена 145-річчю з дня народження Ганса Гана, 23-27 вересня 2024, Чернівецький нац. Університет імені Юрія Федьковича. – Чернівці: 2024, С. 130–131. https://hahn.chnu.edu.ua/media/ntbkpax0/book-of-abstracts.pdf
  3. Sergiy Gefter and Aleksey Piven', Representations of solutions of some nonlinear PDEs in the form of series in powers of the -function, Bogolyubov Kyiv Conference “Problems of Theoretical and Mathematical Physics'', Kyiv, Ukraine, September 24-26, 2024 Book of abstracts. – P.110 https://indico.bitp.kiev.ua/event/13/book-of-abstracts.pdf
  4. Gefter, S., Piven’A., Linear differential operators of infinite order in the module of copolynomials, Матеріали міжнародної наукової конференції “Математика та інформаційні технології», присвяченої 55-річчю факультету математики та інформатики, Чернівці, Україна, 28–30 вересня, 2023, Чернівецький нац. університет.–Чернівці: 2023.– С. 52–55. https://fmi.chnu.edu.ua/media/qhufs0d5/materialy-mizhnorodnoi-naukovoi-konferentsii-fmi55.pdf
  5. Sergey Gefter, Aleksey Piven’, Partial differential equations in the module of copolynomials in several variables over a commutative ring// 6-th International Conference “Differential Equations and Control Theory’’ DECT-2023:Book of abstracts. Kharkiv: V.N. Karazin Kharkiv University, 2023.– P.15 – 16. https://appmath.univer.kharkov.ua/pdf/DECT2023/DECT2023_Book.pdf
  6. Anna Goncharuk, Sergey Gefter, Aleksey Piven’, Periodic and quasi-polynomial solutions of implicit linear difference equations over commutative rings, ICDEA 2022, 27th International Conference on Difference Equations and Applications,18-22 July 2022, Paris-Saclay, France, P. 137. https://icdea2022.sciencesconf.org/data/pages/icdea2022_leaflet_v5_1_.pdf
  7. A.B. Goncharuk; S.L. Gefter; O.L. Piven’, Quasi-polynomial solutions of implicit linear difference equations over a local commutative ring, THE INTERNATIONAL ONLINE CONFERENCE “CURRENT TRENDS IN ABSTRACT AND APPLIED ANALYSIS”, Book of Abstracts, Ivano-Frankivsk, 2022 , P.32 https://conference.pu.if.ua/cta/BookOfAbstracts.pdf
  8. S.L. Gefter, A.L. Piven’, Linear differential equations in the module of copolynomials, Vth International conference “Differential equations and control theory”, Book of abstracts, 2021, P. 18.https://appmath.univer.kharkov.ua/pdf/DECT2021/DECT2021_Book.pdf