I am currently a Senior Research Scientist at NEC Laboratories Europe in Heidelberg, Germany (website).

Before joining NEC in 2022, I did my PhD in computational statistical physics at the University of Leipzig, Germany (website).

Preprints

  1. F. Alesiani, H. Christiansen, and F. Errica,
    Variational Kolmogorov-Arnold Network,
    under review (2025) [arXiv:2507.02466].

  2. H. Christiansen, T. Maruyama, F. Errica, V. Zaverkin, M. Takamoto, and F. Alesiani,
    Fast, Modular, and Differentiable Framework for Machine Learning-Enhanced Molecular Simulations,
    under review (2025) [arXiv:2503.20541].

  3. F. Alesiani, T. Maruyama, H. Christiansen, and V. Zaverkin
    Geometric Kolmogorov-Arnold Superposition Theorem,
    under review (2025) [arXiv:2502.16664].

  4. F. Errica, H. Christiansen, V. Zaverkin, M. Niepert, and F. Alesiani,
    Adaptive Width Neural Networks,
    under review (2025) [arXiv:2501.15889].

  5. H. Christiansen, S. Majumder, W. Janke, and M. Henkel,
    Finite-Size Effects in Aging can be Interpreted as Sub-Aging,
    under review (2025) [arXiv:2501.04843].

Publications

  1. F. Errica, H. Christiansen, V. Zaverkin, T. Maruyama, M. Niepert, and F. Alesiani,
    Adaptive Message Passing: A General Framework to Mitigate Oversmoothing, Oversquashing, and Underreaching,
    Int. Conf. Mach. Learn. (ICML) (2025) [arXiv:2312.16560].

  2. M. Conradi, H. Christiansen, S. Majumder, F. Müller, and W. Janke,
    Nonequilibrium Dynamics of the Helix-Coil Transition in Polyalanine,
    J. Chem. Phys. 162, 154902 (2025) [online].

  3. F. Müller, H. Christiansen, and W. Janke,
    Non-universality of aging during phase separation of the two-dimensional long-range Ising model,
    Phys. Rev. Lett. 133, 237102 (2024) [online] [arXiv:2409.08050].

  4. V. Zaverkin, F. Alesiani, T. Maruyama, F. Errica, H. Christiansen, M. Takamoto, N. Weber, and M. Niepert,
    Higher-Rank Irreducible Cartesian Tensors for Equivariant Message Passing,
    Adv. Neur. Inf. Proc. Sys. (NeurIPS) (2024) [arXiv:2405.14253].

  5. D. Warkotsch, H. Christiansen, J. Zierenberg, and W. Janke,
    Pulling on grafted flexible polymers can cause twisted bundles,
    Soft Matter 20, 4916 (2024) [online].

  6. S. Majumder, H. Christiansen, and W. Janke,
    Temperature and Solvent Viscosity Tune the Intermediates During the Collapse of a Polymer,
    Macromolecules 57, 10586 (2024) [arXiv:2405.04813].

  7. D. Gessert, H. Christiansen, and W. Janke,
    Aging following a zero-temperature quench in the d=3 Ising model,
    Phys. Rev. E 109, 044148 (2024) [online] [arXiv:2404.04214].

  8. V. Zaverkin, D. Holzmüller, H. Christiansen, F. Errica, F. Alesiani, M. Takamoto, M. Niepert, and J. Kästner,
    Uncertainty-biased molecular dynamics for learning uniformly accurate interatomic potentials,
    npj Comput. Mater. 10, 83 (2024) [online] [arXiv:2312.01416] [Research Square].

  9. H. Christiansen, F. Errica, and F. Alesiani,
    Self-Tuning Hamiltonian Monte Carlo for Accelerated Sampling,
    J. Chem. Phys. 159, 234109 (2023) [online] [arXiv:2309.13593].

  10. W. Janke, H. Christiansen, and S. Majumder,
    The Role of Magnetization in Phase-Ordering Kinetics of the Two-Dimensional Short-Range and Long-Range Ising Model,
    Eur. Phys. J. Spec. Top. 232, 1693 (2023) [online].

  11. D. Gessert, H. Christiansen, and W. Janke,
    Superdiffusion-Like Behavior in Zero-Temperature Coarsening of the d=3 Ising Model,
    Sci. Rep. 13, 13270 (2023) [online] [arXiv:2305.12161].

  12. F. Müller, H. Christiansen, S. Schnabel, and W. Janke,
    Fast, Hierarchical, and Adaptive Algorithm for Metropolis Monte Carlo Simulations of Long-Range Interacting Systems,
    Phys. Rev. X 13, 031006 (2023) [online] [arXiv:2207.14670]

  13. F. Müller, H. Christiansen, and W. Janke,
    Phase-Separation Kinetics in the Two-Dimensional Long-Range Ising Model,
    Phys. Rev. Lett. 129, 240601 (2022) [online].

  14. H. Christiansen, S. Majumder, and W. Janke,
    Zero-Temperature Coarsening in the 2D Long-Range Ising Model,
    Phys. Rev. E 103, 052122 (2021) [online] [arXiv:2011.06098].

  15. S. Majumder, H. Christiansen, and W. Janke,
    Understanding Nonequilibrium Scaling Laws Governing Collapse of a Polymer,
    Eur. Phys. J. B 93, 142 (2020) [online] [arXiv:1910.03394].

  16. H. Christiansen, S. Majumder, M. Henkel, and W. Janke,
    Aging in the Long-Range Ising Model,
    Phys. Rev. Lett. 125, 180601 (2020) [online] [Supplemental Material online] [arXiv:1906.11815].

  17. H. Christiansen, M. Weigel, and W. Janke,
    Accelerating Molecular Dynamics Simulations with Population Annealing,
    Phys. Rev. Lett. 122, 060602 (2019) [online] [arXiv:1806.06016].

  18. H. Christiansen, S. Majumder, and W. Janke,
    Phase Ordering Kinetics of the Long-Range Ising Model,
    Phys. Rev. E 99, 011301(R) (2019) [online] [arXiv:1808.10426].

  19. H. Christiansen, S. Majumder, and W. Janke,
    Coarsening and Aging of Lattice Polymers: Influence of Bond Fluctuations,
    J. Chem. Phys. 147, 094902 (2017) [online] [arXiv:1708.03216].

    20. Physics Conferences and ML Workshops

  20. F. Errica, H. Christiansen, V. Zaverkin, M. Niepert, and F. Alesiani,
    On Learning the Width of Neural Networks,
    Workshop: Combining Bayesian and Neural approaches for Structured Data, IJCNN Conference (2025) [online] [Workshop].

  21. F. Alesiani, F. Errica, and H. Christiansen,
    Towards solving Kolmogorov-Arnold Theorem using Variational Optimization,
    Workshop: Combining Bayesian and Neural approaches for Structured Data, IJCNN Conference (2025) [online] [Workshop].

  22. M. Conradi, H. Christiansen, S. Majumder, F. Müller, and W. Janke,
    Influence of Thermostats on the Dynamics of the Helix-Coil Transition,
    accepted for publication in Springer Proceedings in Physics (2025).

  23. P. Kuterba, H. Christiansen, Z. Danel, and W. Janke,
    Molecular dynamics simulations of the monomer density profiles of knotted ring polymer chains confined in a slit of two parallel walls with one attractive and another repulsive surface,
    J. Phys.: Conf. Ser. 2436, 012031 (2023) [online].

  24. H. Christiansen, M. Weigel, and W. Janke,
    Simulating Met-Enkephalin With Population Annealing Molecular Dynamics,
    J. Phys.: Conf. Ser. 2241, 012006 (2022) [online] [arXiv:2005.00810].

  25. H. Christiansen, M. Weigel, and W. Janke,
    Population Annealing Molecular Dynamics with Adaptive Temperature Steps,
    J. Phys.: Conf. Ser. 1163, 012074 (2019) [online].

  26. W. Janke, H. Christiansen, and S. Majumder,
    Coarsening in the Long-Range Ising Model: Metropolis versus Glauber Criterion,
    J. Phys.: Conf. Ser. 1163, 012002 (2019) [online].

  27. S. Majumder, H. Christiansen, and W. Janke,
    Dissipative Dynamics of a Single Polymer in Solution: A Lowe-Andersen Approach,
    J. Phys.: Conf. Ser. 1163, 012072 (2019) [online] [arXiv:1810.08561].

  28. S. Majumder, H. Christiansen, and W. Janke,
    Scaling Laws During Collapse of a Homopolymer: Lattice Versus Off-Lattice,
    J. Phys.: Conf. Ser. 955, 012008 (2018) [online] [arXiv:1712.03083].