Publications



    Monograph

    Jointly with Nora Doll and Hermann Schulz-Baldes I have written a book on various topics about the spectral flow. It can be downloaded here:

    Spectral Flow - A Functional Analytic and Index-Theoretic Approach

    De Gruyter Studies in Mathematics 94

    Preprints

  1. R. Skiba, D. Strzelecki, N. Waterstraat
    An Index Theorem in Relative K-Theory for First-Order Systems
    submitted, 37 pages, 2026, arXiv:2603.20523 [math.DS]

  2. H. Cyris, J. Janczewska, N. Waterstraat
    A Comparison Principle for Bifurcation of Periodic Solutions of Hamiltonian Systems
    accepted for publication in Commun. Contemp. Math., arXiv:2512.24835 [math.DS]

  3. M. Starostka, N. Waterstraat
    Lecture notes on the relative cup-length for the Conley index and the Arnold conjecture
    to appear in Lect. Notes Nonlinear Anal., Juliusz Schauder Cent. Nonlinear Stud.


    4. Published Papers

  4. J. Janczewska, M. Izydorek, M. Starostka, N. Waterstraat
    On the Uniqueness of the G-equivariant Spectral Flow
    SIGMA 22, 2026, Paper No. 29, 21 pages

  5. J. Janczewska, M. Starostka, N. Waterstraat
    Local and Global Bifurcation for Periodic Solutions of Hamiltonian Systems via Comparison Theory for the Spectral Flow
    Topol. Methods Nonlinear Anal. 67, 2026, 103--120

  6. J. Janczewska, M. Izydorek, M. Starostka, N. Waterstraat
    The Equivariant Spectral Flow and Bifurcation for Functionals with Symmetries -- Part I
    Math. Ann. 393, 2026, 2187--2226

  7. J. Janczewska, M. Möckel, N. Waterstraat
    Bifurcation for a Class of Indefinite Elliptic Systems by Comparison Theory for the Spectral Flow via an Index Theorem
    NoDEA Nonlinear Differential Equations Appl. 32, 116, 2025

  8. J. Janczewska, M. Izydorek, N. Waterstraat
    Periodic solutions of Lagrangian systems under small perturbations
    Commun. Contemp. Math. 27, 2025, no. 5, Paper No. 2450031

  9. T. O. Rot, M. Starostka, N. Waterstraat
    The relative cup-length in local Morse cohomology
    Topol. Methods Nonlinear Anal. 64, 2024, 15-29

  10. R. Skiba, N. Waterstraat
    The Index Bundle for Selfadjoint Fredholm Operators and Multiparameter Bifurcation for Hamiltonian Systems
    Z. Anal. Anwend. 41, 2023, 487-501

  11. R. Skiba, N. Waterstraat
    Fredholm theory of families of discrete dynamical systems and its applications to bifurcation theory
    Discrete Contin. Dyn. Syst. 43, 2023, 1878-1904

  12. M. Starostka, N. Waterstraat
    On a Comparison Principle and the Uniqueness of Spectral Flow
    Math. Nachr. 295, 2022, 785--805

  13. M. Izydorek, J. Janczewska, N. Waterstraat
    The Equivariant Spectral Flow and Bifurcation of Periodic Solutions of Hamiltonian Systems
    Nonlinear Anal. 211, 2021

  14. M. Izydorek, J. Janczewska, N. Waterstraat
    Homoclinics for Singular Strong Force Lagrangian Systems in R^N
    Calc. Var. Partial Differential Equations 60, 2021

  15. N. Waterstraat
    On the Fredholm Lagrangian Grassmannian, Spectral Flow and ODEs in Hilbert Spaces
    J. Differential Equations 303, 2021, 667-700

  16. J. Ciesielski, J. Janczewska, N. Waterstraat
    On the existence of homoclinic type solutions for a class of inhomogenous second order Hamiltonian systems
    J. Dynam. Differential Equations 32, 2020, 1343-1356

  17. N. Doll, H. Schulz-Baldes, N. Waterstraat
    Parity as $\mathbb{Z}_2$-valued Spectral Flow
    Bull. London Math. Soc. 51, 2019, 836--852

  18. M. Izydorek, J. Janczewska, N. Waterstraat,
    The Maslov Index and the Spectral Flow-revisited
    Fixed Point Theory and Applications, 2019, Article Nr. 5

  19. M. Starostka, N. Waterstraat,
    The E-cohomological Conley Index, Cup-lengths and the Arnold Conjecture on T^{2n}
    Advanced Nonlinear Studies 19, 2019, 519-528

  20. G. Marchesi, A. Portaluri, N. Waterstraat,
    Not every conjugate point of a semi-Riemannian geodesic is a bifurcation point
    Differential Integral Equations 31, 2018, 871-880

  21. M. Izydorek, J. Janczewska, N. Waterstraat, A. Zgorzelska,
    Bifurcation of equilibrium forms of an elastic rod on a two-parameter Winkler foundation
    Nonlinear Anal. Real World Appl. 39, 2018, 451-463

  22. N. Waterstraat,
    A Remark on Bifurcation of Fredholm Maps
    Adv. Nonlinear Anal. 7, 2018, 285-292

  23. A. Portaluri, N. Waterstraat,
    Corrigendum to "A Morse-Smale index theorem for indefinite elliptic systems and bifurcation'' [J. Differential Equations 258 (5) (2015) 1715-1748]
    J. Differential Equations 264, 2018, 3067-3069

  24. N. Waterstraat,
    Spectral flow and bifurcation for a class of strongly indefinite elliptic systems
    Proc. Royal Soc. Edinburgh A 148, 2018, 1097-1113

  25. R. Skiba, N. Waterstraat,
    The Index Bundle and Multiparameter Bifurcation for Discrete Dynamical Systems
    Discrete Contin. Dynam. Systems 37, 2017, 5603-5629

  26. A. Portaluri, N. Waterstraat,
    A K-theoretical Invariant and Bifurcation for Homoclinics of Hamiltonian Systems
    J. Fixed Point Theory Appl. 19, 2017, 833-851

  27. J. Ciesielski, J. Janczewska, N. Waterstraat,
    On the existence of homoclinic type solutions of inhomogenous Lagrangian systems
    Differential Integral Equations 30, 2017, 259-272

  28. N. Waterstraat,
    Fredholm Operators and Spectral Flow
    Rend. Sem. Mat. Univ. Politec. Torino 75, 2017, 7-51

  29. A.M. Candela, N. Waterstraat,
    Bifurcation of critical points along gap-continuous families of subspaces
    J. Fixed Point Theory Appl. 19, 2017, 3053-3068

  30. F. Bei, N. Waterstraat,
    On the space of connections having non-trivial twisted harmonic spinors
    J. Math. Phys. 56, 2015

  31. N. Waterstraat,
    Spectral flow, crossing forms and homoclinics of Hamiltonian systems
    Proc. Lond. Math. Soc. (3) 111, 2015, 275-304

  32. N. Waterstraat,
    On bifurcation for semilinear elliptic Dirichlet problems on shrinking domains
    Springer Proc. Math. Stat. 119, 2015, 273-291

  33. A. Portaluri, N. Waterstraat,
    Yet another proof of the Morse index theorem
    Expositiones Math. 33, 2015, 378-386

  34. N. Waterstraat,
    A family index theorem for periodic Hamiltonian systems and bifurcation
    Calculus of Variations and PDE 52, 2015, 727-753

  35. M. Starostka, N. Waterstraat,
    A remark on singular sets of vector bundle morphisms
    European J. Math. 1, 154-159

  36. A. Portaluri, N. Waterstraat,
    A Morse-Smale index theorem for indefinite elliptic systems and bifurcation
    J. Differential Equations 258, 2015, 1715-1748

  37. A. Portaluri, N. Waterstraat,
    On bifurcation for semilinear elliptic Dirichlet problems on geodesic balls
    J. Math. Anal. Appl. 415, 2014, 240-246

  38. A. Portaluri, N. Waterstraat,
    Bifurcation results for critical points of families of functionals
    Differential Integral Equations 27, 2014, 369-386

  39. J. Pejsachowicz, N. Waterstraat,
    Bifurcation of critical points for continuous families of $C^2$ functionals of Fredholm type
    J. Fixed Point Theory Appl. 13, 2013, 537-560

  40. A. Portaluri, N. Waterstraat,
    On bifurcation for semilinear elliptic Dirichlet problems and the Morse-Smale index theorem
    J. Math. Anal. Appl. 408, 2013, 572-575

  41. N. Waterstraat,
    A remark on the space of metrics having non-trivial harmonic spinors
    J. Fixed Point Theory Appl. 13, 2013, 143-149

  42. N. Waterstraat,
    A K-theoretic proof of the Morse index theorem in semi-Riemannian geometry
    Proc. Amer. Math. Soc. 140, 2012, 337-349

  43. N. Waterstraat,
    The index bundle for Fredholm morphisms
    Rend. Sem. Mat. Univ. Politec. Torino 69, 2011, 299-315


    44. Other Publications

  44. N. Waterstraat,
    Ein Blick in die Nachbarschaft: Forschungsförderung in Polen
    Mitteilungen der DMV 33 (2), 2025

  45. I. S. Hähnlein, C. Luleich, P. Reiter, N. Waterstraat, P. Pirnay-Dummer,
    Transforming formal knowledge to language and graphs to promote mathematics learning: A repeated-measures mixed design quasi-experiment
    Computers in Human Behavior Reports 18, 2025

  46. N. Waterstraat,
    Das Institut für Mathematik (2018 bis heute)
    Cantor-Heft 26 der Georg-Cantor-Vereinigung, 2024, 7-12

  47. C. Luleich, N. Waterstraat, P. Reiter,
    Modelling Mathematical Knowledge from Natural Language Representations. Introducing a New Method
    Paper presented at the AECT, Jacksonville, FL, 2020

  48. N. Waterstraat,
    1,2,3...'ne Menge! Wie viel ist Unendlich?
    Cantor-Heft 21 der Georg-Cantor-Vereinigung, 2019, 9-18

  49. N. Waterstraat,
    The index bundle for gap-continuous families and the spectral flow
    Oberwolfach Rep. 9, 2012, 1530-1532