January 2022 - Present, Senior Lecturer, University of the Free State, Bloemfontein, South Africa

October 2019 - December 2021, Postdoctoral Fellow, North-West University, Potchefstroom, South Africa

October 2016 - September 2019, PhD Student (Functional Analysis), Bergische Universität Wuppertal, Wuppertal, Germany

October 2015 - August 2016, PhD Student (cancelled), Vrije Universiteit Brussel, Brussels, Belgium

September 2010 - August 2015, BSc and MSc in Mathematics, Radboud Universiteit Nijmegen, Nijmegen, The Netherlands

External funding:

The following grants have been awared to me:

• DFG - Walter-Benjamin Program (2021): "Perturbation Methods for Abstract Cauchy Problems associated to Evolution Equations" (Project Number: 468736785)
• NRF Schholarship: Innovation and Freestanding Postdoctoral Fellowships (2022): "Well-Posedness and perturbations of (non)autonomous evolution equations" (Grant number: 138497)
• DSI-NRF Centre of Excellence in Mathematical and Statistical Sciences (CoE-MaSS) - Research Grant (2023):"Evolution equations on graph limits" (Reference number: 2022-54-OPA-Evolution)
• NRF Knowledge, Interchange & Collaboration (KIC) - Second Call (2023): Visiting Foreign Researcher: Dr. Christian Seifert (Hamburg, Germany), 2023, (Grant number: KIC22080247403)
• NRF Competitive Support for Unrated Researchers (2023 - 2025): "(Non)autonomous abstract Cauchy problems and beyond - Solutions and perturbation methods for evolution equations" (Grant number: SRUG220317136)
• DSI-NRF Centre of Excellence in Mathematical and Statistical Sciences (CoE-MaSS) - Research Grant (2024):"Bi-Continuous Semigroups: Applications and Beyond" (Reference number: 2024-031-OPA-Bi-Continuous Semigroups)
• NRF Knowledge, Interchange & Collaboration (KIC) - Second Call (2024): Visiting Foreign Researcher: Dr. Christian Seifert (Hamburg, Germany), 2023, (Grant number: KIC230816143482)

• DSI-NRF Centre of Excellence in Mathematical and Statistical Sciences (CoEMaSS) - Research Grant (2024): "Advancements of bi-continuous cosine families" (Reference number: 2025-013-OPA-Bi-Continous Cosine Families)

  
  

Peer-reviewed publications

1. C. Budde, Another special role of L8-spaces: Evolution equations and Lotz` Theorem, AIMS Math. 9:12, 36158–36166 (2024), URL https://doi.org/10.3934/math.20241716

2. C. Budde, On bi-continuous cosine families, Quaest. Math. 47:2, 1589–1611 (2024), URL https://doi.org/10.2989/16073606.2024.2328817

3. C. Budde and C. Seifert, Perturbations of non-autonomous second-order abstract Cauchy problems, Anal. Math. 50, 733–755 (2024), URL https://doi.org/10.1007/s10476-024-00035-8

4. C. Budde, A Banach bundle approach to dynamical processes on changing networks, Poincare J. Anal. Appl 11:1. 53–66 (2024), URL http://dx.doi.org/10.46753/pjaa.2024.v011i01.004

5. C. Budde and M. Kramar Fijavž, Well-posedness of non-autonomous transport equation on metric graphs, Semigroup Forum, 108:2, 319–334 (2024), URL https://doi.org/10.1007/s00233-024-10417-x

6. C. Budde and J. Kreulich, On Splittings and Integration of Almost Periodic Functions With and Without Geometry, Semigroup Forum, 108:2, 335–364 (2024), URL https://doi.org/10.1007/s00233-024-10415-z

7. C. Budde, How to approach stability of bi-continuous semigroups?, Math. Pannonica (N.S.),29:2, 282–290 (2023), URL https://doi.org/10.1556/314.2023.00029
8. C. Budde, On Trotter-Kato type inductive limits in the category of C0-semigroups, Adv. Dyn. Syst. Appl., 18:2, 125–136 (2023), URL https://dx.doi.org/10.37622/ADSA/18.2.2023.125-136
9. R. Benjamin and C. Budde, A note on the order Lozanovsky spectrum for positive operators, Complex Anal. Oper. Theory, 17:61 (2023), URL https://doi.org/10.1007/s11785-023-01374-4
10. C. Budde, A. Dobrick, J. Glück and M. Kunze, A monotone convergence theorem for strong Feller semigroups, Ann. Mat. Pura Appl. 202:1573-1589 (2023), URL https://doi.org/10.1007/s10231-022-01293-9 
11. C. Budde and J. Kreulich, Application of abstract semigroup theory to the asymptotic behavior of C0-semigroups, Complex Anal. Oper. Theory., 16:105 (2022), URL https://doi.org/10.1007/s11785-022-01285-w
12. C. Budde, L. Labuschagne and C. Steyn, Almost everywhere convergence for noncommutative spaces, Banach J. Math. Anal., 16:56 (2022), URL https://doi.org/10.1007/s43037-022-00209-2
13. C. Budde and S.-A. Wegner, A Lumer-Phillips type generation theorem for bi-continuous semigroups, Z. Anal. Anwend., 41(1-2):65-80, URL https://doi.org/10.4171/ZAA/1695 (2022)
14. C. Budde, Semigroups for flows on limits of graphs, Univ. Iagel. Acta Math., 7–21, URL https://doi.org/10.4467/20843828AM.21.001.14982.
15. C. Budde, Positive Desch-Schappacher perturbations of bi-continuous semigroups on AM-spaces, Acta Sci. Math. (Szeged), 87 (2021), 571–594, URL https://doi.org/10.14232/actasm-021-914-5.
16. C. Budde, Perturbations of uniformly mean ergodic semigroups, J. Semigroup Theory Appl. (2021), Article ID 1, URL http://dx.doi.org/10.28919/jsta/5509.
17. C. Budde and M. Kramar Fijavž, Bi-Continuous semigroups for flows on infinite networks, Netw. Heterog. Media, 16 (2021), 553–567, URL https://doi.org/10.3934/nhm.2021017.
18. C. Budde and R. Heymann, Extrapolation of operator-valued multiplication operators, Quaest. Math., 45 (2022), 347–356, URL https://doi.org/10.2989/16073606.2020.1859639.
19. C. Budde, Positive Miyadera-Voigt perturbations of bi-continuous semigroups, Positivity, 25 (2021), 1107–1129, URL https://doi.org/10.1007/s11117-020-00806-1.
20. C. Budde and B. Farkas, A Desch-Schappacher perturbation theorem for bi-continuous semigroups, Math. Nachr., 293 (2020), 1053–1073, URL https://doi.org/10.1002/mana.201800534.
21. C. Budde and B. Farkas, Intermediate and extrapolated spaces for bi-continuous operator semigroups, J. Evol. Equ., 19 (2019), 321–359, URL https://doi.org/10.1007/s00028-018-0477-8.
22. C. Budde and K. Landsman, A bounded transform approach to self-adjoint operators: functional calculus and affiliated von Neumann algebras, Ann. Funct. Anal., 7 (2016), 411–420, URL https://doi.org/10.1215/20088752-3605384.

Proceeding Articles

1. C. Budde and C. Seifert, Non-autonomous Desch-Schappacher perturbations, In: Choi, Y., Daws, M., Blower, G. (eds) Operators, Semigroups, Algebras and Function Theory. IWOTA 2021. Operator Theory: Advances and Applications, Vol 292. Birkhauser, Cham., 71–90 (2023), URL https://doi.org/10.1007/978-3-031-38020-4_4.

Theses

1. C. Budde, General Extrapolation Spaces and Perturbations of Bi-Continuous Semigroups, PhD thesis, Bergische Universität Wuppertal, 2019, Supervisor: Prof.Dr. Bálint Farkas, Second reader: Prof.Dr. Abdelaziz Rhandi.
2. C. Budde, Operator Algebras and Unbounded Self-Adjoint Operators, Master’s thesis, Radboud Universiteit Nijmegen, 2015, Supervisor: Prof.Dr. Klaas Landsman, Second reader: Dr. Jens Kaad.
3. C. Budde, Representation of Groups and Their Applications, Bachelor thesis, Radboud Universiteit Nijmegen, 2013, Original Dutch title: Representaties van groepen en hun Toepassingen, Supervisor: Prof.Dr. Gert Heckman, Second reader: Dr.Michael Müger.

Preprints

1. J. Allison, C. Budde, J. du Pisanie and J. Visagie, A critical review of existing and new population stability testing procedures in credit risk scoring, Submitted, arXiv:2303.01227. 

Current Teaching 

In 2025, I will lecture the following modules:

1st Semester: MATM3774 - Real Analysis

1st Semester: MATE6814 - Functional Analysis

2nd Semester: MATM3784 - Complex Analysis

Past Teaching

At the University of the Free State, I presented the following modules: 

1st Semester (2022/2023/2024): MATM3714 - Complex Analysis

2nd Semester (2022/2023/2024): MATM2624 - Linear Algebra

2nd Semester (2022/2023): MATE6824 - Functional Analysis 

2nd Semester (2024): MATF6824 - Measure and Integration Theory

During my time as postdoc at the North-West University (Potchefstroom) I taught the following modules: 

1st Semester (2020): MTHS 614 - Measure and Integration

2nd Semester (2021): STTK887 - Advanced Probability Theory

Teaching Assistance

As student as well as during my PhD I had the opportunity to assist the following modules: 

Analysis III (Bergische Universität Wuppertal)

Analysis II (Bergische Universität Wuppertal)

Analysis I (Bergische Universität Wuppertal)

Ordinary Differential Equations (Bergische Universität Wuppertal)

Calculus (Vrije Universiteit Brussel)

Introductory Mathematical Physics (Radboud Universiteit Nijmegen)

Theses Projects

If you are interested in writing a honours or Master thesis in the area of (functional) analysis, please do not hesitate to contact me directly by e-mail then I can send you a list of possible projects.