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Scientific activity

My research interests include functional analysis, the theory of linear operators on Hilbert spaces, and nonlinear analysis.

Research profiles and identifiers:

Publications:

  • Witold Majdak, Nikolaos S. Papageorgiou, Singular elliptic equations with (p(z),q(z))-growth, J. Fixed Point Theory Appl. 28 (2026), Article number 57.
  • Josef Diblík, Marek Galewski, Witold Majdak, Explicit solution of an initial problem for a matrix differential equation involving three matrices with a single time lag, Bulletin of Mathematical Sciences (2026), 2650004.
  • Krzysztof Bień, Witold Majdak, Nikolaos S. Papageorgiou, Parametric singular problems with an indefinite perturbation, The Journal of Geometric Analysis 34 (2024), Article no. 103.
  • Michał Bełdziński, Marek Galewski, Witold Majdak, On the nonlinear perturbations of self-adjoint operators, Advances in Nonlinear Analysis 11 (2022), 1117–1133.
  • Witold Majdak, Laurian Suciu, Convex and expansive liftings close to two-isometries and power bounded operators, Linear Algebra and its Applications 617 (2021), 1-26.
  • Witold Majdak, Laurian Suciu, Triangulations of operators with two-isometric liftings, Integral Equations Operator Theory 93 (2021), no. 1, 10.
  • Witold Majdak, Laurian Suciu, Brownian type parts of operators in Hilbert spaces, Results Math (2020) 75:5.
  • Witold Majdak, Laurian Suciu, Brownian isometric parts of concave operators, New York J. Math. 25 (2019), 1067–1090.
  • Witold Majdak, Mostafa Mbekhta, Laurian Suciu, Operators intertwining with isometries and Brownian parts of 2-isometries, Linear Algebra and its Applications 509 (2016), 168–190.
  • Witold Majdak, Jerzy B. Stochel, Weighted shifts on directed semi-trees: an application to creation operators on Segal-Bargmann spaces, Complex Anal. Oper. Theory 10 (2016), 1427–1452.
  • Ewelina Zalot, Witold Majdak, Spectral representations for a class of banded Jacobi-type matrices, Opuscula Math. 34 (2014), 871-887.
  • Witold Majdak, Nicolae-Adrian Secelean, Laurian Suciu, Ergodic properties of operators in some semi-Hilbertian spaces, Linear and Multilinear Algebra 61 (2013), 139–159.
  • Majdak, Jan Stochel, A local lifting theorem for jointly subnormal families of unbounded operators, Integral Equations Oper. Theory 69 (2011), 233-246.
  • Witold Majdak, A lifting theorem for unbounded quasinormal operators, J. Math. Anal. Appl. 332 (2007), 934-946.
  • Witold Majdak, Zoltan Sebestyen, Jan Stochel, James E. Thomson, A local lifting theorem for subnormal operators, Proc. Amer. Math. Soc. 134 (2006), 1687-1699.

Selected invited visits and conferences:

  • Conference "Dynamical Systems and Applications VI, DSA 2024", Łódź, Poland, June 26–28, 2024.
  • Conference "IWOTA 2022", Kraków, Poland, September 6–10, 2022.
  • Conference "Operator Theory and Beyond 2022", Jagiellonian University, Kraków, Poland, June 29–July 1, 2022.
  • Visiting Senior Scholar at Heilongjiang Institute of Technology, Harbin, China, December 2–21, 2018; talks at:
    • Harbin Engineering University, Harbin, China, December 5.
    • Harbin Institute of Technology, Harbin, China, December 6.
    • Heilongjiang Institute of Technology, Harbin, China, December 7.
    • Workshop on Nonlinear Analysis and Applications, Central South University, Changsha, China, December 9–11 (two reports).
    • Chinese Academy of Sciences, Beijing, China, December 13.
    • 3rd International Workshop on Nonlinear Analysis and its Applications, Heilongjiang Institute of Technology, Harbin, China, December 15–17.
    • Chongqing Technology and Business University, Chongqing, China, December 18.
  • Conference "Recent Advances in Nonlinear Analysis", Levico Terme (Trento), Italy, May 28–30, 2018.

Editorial Service:

  • Managing Editor of the journal Opuscula Mathematica
    (Impact Factor 2025: 2.2, Q1; CiteScore 2025: 2.9, Q1; SJR 2025: 0.717, Q1; SNIP 2025: 1.286)

Conference organizational activities:

  • Member of the Organizing Committee of the conference "Dynamical Systems and Applications VI, DSA 2024", Łódź, Poland (June 26–28, 2024).
  • Member of the Organizing Committee of the conference "IWOTA 2022", Kraków, Poland (September 6–10, 2022).
  • Co-organizer of "Elsevier - JMAA Conference on Nonlinear Analysis at AGH UST" (October 11–12, 2019).
  • Member of the Organizing Committee of the Jubilee Congress of Polish Mathematicians for the 100th Anniversary of the Polish Mathematical Society (September 3–7, 2019).
  • Member of the Organizing Committee of the conference "100 Years of Forensics" (July 7, 2019).
  • Member of the Organizing Committee of the conference "Forensics - Science, Modern Technologies" (September 20–22, 2017).
  • Co-organizer of the conference "Spectral Theory and Applications (STA 2017)".
  • Co-organizer of the conference "Spectral Theory and Applications (STA 2015)".
  • Program coordinator of the 6th European Congress of Mathematicians (2012).
  • Member of the Organizing Committee of the conference "Functions and Operators" (2010).