Staff Profile

I am Director of Pure Mathematics in the School of Mathematics, Statistics and Physics, and I co-chair the School's EDI Committee. I am a member of the London Mathematical Society and the European Mathematical Society, and I have been a Fellow of the UK Higher Education Academy (Advance HE) since 2017. From 2019 to 2024 I represented the UK on the managing committee of an EU-funded project on Mathematical Models for Interacting Dynamics on Networks (COST Action 18232).

Before arriving in Newcastle I was at the University of Oxford, most recently as a fellow of St John's College, and before that as an undergraduate and later graduate student at Hertford College and Balliol College, respectively. I completed my Habilitation at TU Dresden, Germany.

My area of research is operator theory, and I am particularly interested in the quantitative asymptotic behaviour of operator semigroups. My work combines elements of functional analysis, harmonic analysis and complex analysis, and it has applications in the study of energy decay of damped waves, in some areas of mathematical control theory and in the theory of iterative methods.

I recently co-organised the conference New Challenges in Operator Semigroups, which was held in St John's College, Oxford.

My work has received generous financial support from various sources, including the London Mathematical Society, the Heilbronn Institute for Mathematical Research, the Engineering and Physical Sciences Research Council and the European Cooperation in Science and Technology (COST).

I welcome enquiries from prospective Master's students, PhD students and postdocs in my area of expertise.

I am currently module leader for:

• Linear Analysis MAS3702/MAS8702

• Articles

  • Pritchard AKJ, Seifert D. The asymptotic behaviour of the Cesàro operator. Journal of Mathematical Analysis and Applications 2025, 543(1), 128847.
  • Nicaise S, Paunonen L, Seifert D. Stability of abstract coupled systems. Journal of Functional Analysis 2025, 289(2), 110909.
  • Paunonen L, Seifert D, Vanspranghe N. A non-uniform Datko--Pazy theorem for bounded operator semigroups. Studia Mathematica 2025, 280, 193-203.
  • Batty CJK, Seifert D. A Katznelson-Tzafriri theorem for analytic Besov functions of operators. Journal of Operator Theory 2024, 91(2), 545-565.
  • Dell'Oro F, Paunonen L, Seifert D. Optimal decay for a wave-heat system with Coleman-Gurtin thermal law. Journal of Mathematical Analysis and Applications 2023, 518(2), 126706.
  • Chill R, Paunonen L, Seifert D, Stahn R, Tomilov Y. Nonuniform stability of damped contraction semigroups. Analysis & PDE 2023, 16(5), 1089-1132.
  • Batty CJK, Seifert D. A continuous-parameter Katznelson-Tzafriri theorem for algebras of analytic functions. Studia Mathematica 2023, 270, 229-239.
  • Batty CJK, Seifert D. Some developments around the Katznelson-Tzafriri theorem. Acta Scientiarum Mathematicarum 2022, 88, 53-84.
  • Chill R, Seifert D, Tomilov Y. Semi-uniform stability of operator semigroups and energy decay of damped waves. Philosophical Transactions A 2020, 378(2185), 20190614.
  • Ng ACS, Seifert D. Optimal rates of decay in the Katznelson-Tzafriri theorem for operators on Hilbert spaces. Journal of Functional Analysis 2020, 279(12), 108799.
  • Ng ACS, Seifert D. Optimal energy decay in a one-dimensional wave-heat system with infinite heat part. Journal of Mathematical Analysis and Applications 2020, 482(2), 123563.
  • Hibble SJ, Chippindale AM, Zbiri M, Rees NH, Keeble DS, Wilhelm H, d'Abrumenil S, Seifert D. Intra- and Interchain Interactions in (Cu_1/2Au_1/2)CN, (Ag_1/2Au_1/2)CN, and (Cu_1/3Ag_1/3Au_1/3)CN and Their Effect on One-, Two-, and Three-Dimensional Order. Inorganic Chemistry 2020, 59(16), 11704–11714.
  • Paunonen L, Seifert D. Asymptotics and approximation of large systems of ordinary differential equations. Systems & Control Letters 2020, 140, 104703.
  • Debruyne G, Seifert D. Optimality of the quantified Ingham-Karamata theorem for operator semigroups with general resolvent growth. Archiv der Mathematik 2019, 113(6), 617–627.
  • Rozendaal J, Seifert D, Stahn R. Optimal rates of decay for operator semigroups on Hilbert spaces. Advances in Mathematics 2019, 346, 359-388.
  • Batty CJK, Paunonen L, Seifert D. Optimal energy decay for the wave-heat system on a rectangular domain. SIAM Journal on Mathematical Analysis 2019, 51(2), 808-819.
  • Paunonen L, Seifert D. Asymptotics for periodic systems. Journal of Differential Equations 2019, 266(11), 7152-7172.
  • Debruyne G, Seifert D. An abstract approach to optimal decay of functions and operator semigroups. Israel Journal of Mathematics 2019, 233(1), 439-451.
  • Mokhtar-Kharroubi M, Seifert D. Rates of convergence to equilibrium for collisionless kinetic equations in slab geometry. Journal of Functional Analysis 2018, 275(9), 2404-2452.
  • Paunonen L, Seifert D. Asymptotic behaviour of coupled systems in discrete and continuous time. Journal of Dynamics and Differential Equations 2018, 30(2), 433-444.
  • Badea C, Seifert D. Quantified asymptotic behaviour of Banach space operators and applications to iterative projection methods. Pure and Applied Functional Analysis 2017, 2(4), 585-598.
  • Darwin O, Jha A, Roy S, Seifert D, Steele R, Stigant L. Non-optimality of the Greedy Algorithm for subspace orderings in the method of alternating projections. Results in Mathematics 2017, 72(1), 979-990.
  • Paunonen L, Seifert D. Asymptotics for infinite systems of differential equations. SIAM Journal on Control and Optimization 2017, 55(2), 1153-1178.
  • Paunonen L, Seifert D. Asymptotic behaviour in the robot rendezvous problem. Automatica 2017, 79, 127-130.
  • Badea C, Seifert D. Ritt operators and convergence in the method of alternating projections. Journal of Approximation Theory 2016, 205, 133-148.
  • Seifert D. Rates of decay in the classical Katznelson-Tzafriri theorem. Journal d'Analyse Mathématique 2016, 130(1), 329-354.
  • Chill R, Seifert D. Quantified versions of Ingham’s theorem. Bulletin of the London Mathematical Society 2016, 48(3), 519-532.
  • Batty CJK, Paunonen L, Seifert D. Optimal energy decay in a one-dimensional coupled wave-heat system. Journal of Evolution Equations 2016, 16(3), 649–664.
  • Seifert D. Some improvements of the Katznelson-Tzafriri theorem on Hilbert space. Proceedings of the American Mathematical Society 2015, 143, 3827-3838.
  • Seifert D. A quantified Tauberian theorem for sequences. Studia Mathematica 2015, 227, 183-192.
  • Seifert D. A Katznelson–Tzafriri Theorem for Measures. Integral Equations and Operator Theory 2015, 81(2), 255–270.

• Conference Proceedings (inc. Abstracts)

  • Pritchard AKJ, Seifert D. Tauberian theorems for sequences and the Katznelson-Tzafriri theorem. In: International Workshop on Operator Theory and its Applications (IWOTA) 2024. 2024, University of Kent, Canterbury, UK: Birkhäuser.
  • Paunonen L, Seifert D. Polynomial stability of a coupled wave-heat network. 2025. In Press.
  • Dell'Oro F, Seifert D. A short elementary proof of the Gearhart-Prüss theorem for bounded semigroups. In: Control and Inverse Problems. CIP 2022. 2022, Monastir, Tunisia: Springer Nature.
  • Paunonen L, Seifert D. Asymptotic behaviour of platoon systems. In: 22nd International Symposium on Mathematical Theory of Networks and Systems. 2016, Minnesota, MN, USA.