---
_id: '63557'
abstract:
- lang: eng
  text: We discretise a recently proposed new Lagrangian approach to optimal control
    problems with dynamics described by force-controlled Euler-Lagrange equations
    (Konopik et al., in Nonlinearity 38:11, 2025). The resulting discretisations are
    in the form of discrete Lagrangians. We show that the discrete necessary conditions
    for optimality obtained provide variational integrators for the continuous problem,
    akin to Karush-Kuhn-Tucker (KKT) conditions for standard direct approaches. This
    approach paves the way for the use of variational error analysis to derive the
    order of convergence of the resulting numerical schemes for both state and costate
    variables and to apply discrete Noether’s theorem to compute conserved quantities,
    distinguishing itself from existing geometric approaches. We show for a family
    of low-order discretisations that the resulting numerical schemes are ‘doubly-symplectic’,
    meaning they yield forced symplectic integrators for the underlying controlled
    mechanical system and overall symplectic integrators in the state-adjoint space.
    Multi-body dynamics examples are solved numerically using the new approach. In
    addition, the new approach is compared to standard direct approaches in terms
    of computational performance and error convergence. The results highlight the
    advantages of the new approach, namely, better performance and convergence behaviour
    of state and costate variables consistent with variational error analysis and
    automatic preservation of certain first integrals.
author:
- first_name: Michael
  full_name: Konopik, Michael
  last_name: Konopik
- first_name: Sigrid
  full_name: Leyendecker, Sigrid
  last_name: Leyendecker
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Rodrigo T.
  full_name: Sato Martín de Almagro, Rodrigo T.
  last_name: Sato Martín de Almagro
citation:
  ama: Konopik M, Leyendecker S, Maslovskaya S, Ober-Blöbaum S, Sato Martín de Almagro
    RT. On the variational discretisation of optimal control problems for unconstrained
    Lagrangian dynamics. <i>Multibody System Dynamics</i>. Published online 2026.
    doi:<a href="https://doi.org/10.1007/s11044-025-10138-1">10.1007/s11044-025-10138-1</a>
  apa: Konopik, M., Leyendecker, S., Maslovskaya, S., Ober-Blöbaum, S., &#38; Sato Martín de Almagro,
    R. T. (2026). On the variational discretisation of optimal control problems for
    unconstrained Lagrangian dynamics. <i>Multibody System Dynamics</i>. <a href="https://doi.org/10.1007/s11044-025-10138-1">https://doi.org/10.1007/s11044-025-10138-1</a>
  bibtex: '@article{Konopik_Leyendecker_Maslovskaya_Ober-Blöbaum_Sato Martín de Almagro_2026,
    title={On the variational discretisation of optimal control problems for unconstrained
    Lagrangian dynamics}, DOI={<a href="https://doi.org/10.1007/s11044-025-10138-1">10.1007/s11044-025-10138-1</a>},
    journal={Multibody System Dynamics}, publisher={Springer Science and Business
    Media LLC}, author={Konopik, Michael and Leyendecker, Sigrid and Maslovskaya,
    Sofya and Ober-Blöbaum, Sina and Sato Martín de Almagro, Rodrigo T.}, year={2026}
    }'
  chicago: Konopik, Michael, Sigrid Leyendecker, Sofya Maslovskaya, Sina Ober-Blöbaum,
    and Rodrigo T. Sato Martín de Almagro. “On the Variational Discretisation of Optimal
    Control Problems for Unconstrained Lagrangian Dynamics.” <i>Multibody System Dynamics</i>,
    2026. <a href="https://doi.org/10.1007/s11044-025-10138-1">https://doi.org/10.1007/s11044-025-10138-1</a>.
  ieee: 'M. Konopik, S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, and R. T. Sato Martín de Almagro,
    “On the variational discretisation of optimal control problems for unconstrained
    Lagrangian dynamics,” <i>Multibody System Dynamics</i>, 2026, doi: <a href="https://doi.org/10.1007/s11044-025-10138-1">10.1007/s11044-025-10138-1</a>.'
  mla: Konopik, Michael, et al. “On the Variational Discretisation of Optimal Control
    Problems for Unconstrained Lagrangian Dynamics.” <i>Multibody System Dynamics</i>,
    Springer Science and Business Media LLC, 2026, doi:<a href="https://doi.org/10.1007/s11044-025-10138-1">10.1007/s11044-025-10138-1</a>.
  short: M. Konopik, S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, R.T. Sato Martín de Almagro,
    Multibody System Dynamics (2026).
date_created: 2026-01-12T11:33:54Z
date_updated: 2026-01-12T11:35:27Z
department:
- _id: '636'
doi: 10.1007/s11044-025-10138-1
language:
- iso: eng
publication: Multibody System Dynamics
publication_identifier:
  issn:
  - 1384-5640
  - 1573-272X
publication_status: published
publisher: Springer Science and Business Media LLC
status: public
title: On the variational discretisation of optimal control problems for unconstrained
  Lagrangian dynamics
type: journal_article
user_id: '87909'
year: '2026'
...
---
_id: '59792'
abstract:
- lang: eng
  text: "<jats:title>Abstract</jats:title>\r\n          <jats:p>Motivated by mechanical
    systems with symmetries, we focus on optimal control problems possessing certain
    symmetries. Following recent works (Faulwasser in Math Control Signals Syst 34:759–788
    2022; Trélat in Math Control Signals Syst 35:685–739 2023), which generalized
    the classical concept of <jats:italic>static turnpike to manifold turnpike</jats:italic>
    we extend the <jats:italic>exponential turnpike property</jats:italic> to the
    <jats:italic>exponential trim turnpike</jats:italic> for control systems with
    symmetries induced by abelian or non-abelian groups. Our analysis is mainly based
    on the geometric reduction of control systems with symmetries. More concretely,
    we first reduce the control system on the quotient space and state the turnpike
    theorem for the reduced problem. Then we use the group properties to obtain the
    <jats:italic>trim turnpike theorem</jats:italic> for the full problem. Finally,
    we illustrate our results on the Kepler problem and the rigid body problem.\r\n</jats:p>"
author:
- first_name: Kathrin
  full_name: Flaßkamp, Kathrin
  last_name: Flaßkamp
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
citation:
  ama: Flaßkamp K, Maslovskaya S, Ober-Blöbaum S, Wembe Moafo BE. Trim turnpikes for
    optimal control problems with symmetries. <i>Mathematics of Control, Signals,
    and Systems</i>. Published online 2025. doi:<a href="https://doi.org/10.1007/s00498-025-00408-w">10.1007/s00498-025-00408-w</a>
  apa: Flaßkamp, K., Maslovskaya, S., Ober-Blöbaum, S., &#38; Wembe Moafo, B. E. (2025).
    Trim turnpikes for optimal control problems with symmetries. <i>Mathematics of
    Control, Signals, and Systems</i>. <a href="https://doi.org/10.1007/s00498-025-00408-w">https://doi.org/10.1007/s00498-025-00408-w</a>
  bibtex: '@article{Flaßkamp_Maslovskaya_Ober-Blöbaum_Wembe Moafo_2025, title={Trim
    turnpikes for optimal control problems with symmetries}, DOI={<a href="https://doi.org/10.1007/s00498-025-00408-w">10.1007/s00498-025-00408-w</a>},
    journal={Mathematics of Control, Signals, and Systems}, publisher={Springer Science
    and Business Media LLC}, author={Flaßkamp, Kathrin and Maslovskaya, Sofya and
    Ober-Blöbaum, Sina and Wembe Moafo, Boris Edgar}, year={2025} }'
  chicago: Flaßkamp, Kathrin, Sofya Maslovskaya, Sina Ober-Blöbaum, and Boris Edgar
    Wembe Moafo. “Trim Turnpikes for Optimal Control Problems with Symmetries.” <i>Mathematics
    of Control, Signals, and Systems</i>, 2025. <a href="https://doi.org/10.1007/s00498-025-00408-w">https://doi.org/10.1007/s00498-025-00408-w</a>.
  ieee: 'K. Flaßkamp, S. Maslovskaya, S. Ober-Blöbaum, and B. E. Wembe Moafo, “Trim
    turnpikes for optimal control problems with symmetries,” <i>Mathematics of Control,
    Signals, and Systems</i>, 2025, doi: <a href="https://doi.org/10.1007/s00498-025-00408-w">10.1007/s00498-025-00408-w</a>.'
  mla: Flaßkamp, Kathrin, et al. “Trim Turnpikes for Optimal Control Problems with
    Symmetries.” <i>Mathematics of Control, Signals, and Systems</i>, Springer Science
    and Business Media LLC, 2025, doi:<a href="https://doi.org/10.1007/s00498-025-00408-w">10.1007/s00498-025-00408-w</a>.
  short: K. Flaßkamp, S. Maslovskaya, S. Ober-Blöbaum, B.E. Wembe Moafo, Mathematics
    of Control, Signals, and Systems (2025).
date_created: 2025-05-05T09:23:38Z
date_updated: 2025-05-05T09:24:09Z
department:
- _id: '636'
doi: 10.1007/s00498-025-00408-w
language:
- iso: eng
publication: Mathematics of Control, Signals, and Systems
publication_identifier:
  issn:
  - 0932-4194
  - 1435-568X
publication_status: published
publisher: Springer Science and Business Media LLC
status: public
title: Trim turnpikes for optimal control problems with symmetries
type: journal_article
user_id: '87909'
year: '2025'
...
---
_id: '58544'
abstract:
- lang: eng
  text: 'We introduce a new classification of multimode states with a fixed number
    of photons. This classification is based on the factorizability of homogeneous
    multivariate polynomials and is invariant under unitary transformations. The classes
    physically correspond to field excitations in terms of single and multiple photons,
    each of which being in an arbitrary irreducible superposition of quantized modes.
    We further show how the transitions between classes are rendered possible by photon
    addition, photon subtraction, and photon-projection nonlinearities. We explicitly
    put forward a design for a multilayer interferometer in which the states for different
    classes can be generated with state-of-the-art experimental techniques. Limitations
    of the proposed designs are analyzed using the introduced classification, providing
    a benchmark for the robustness of certain states and classes. '
author:
- first_name: Denis
  full_name: Kopylov, Denis
  id: '98502'
  last_name: Kopylov
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Laura
  full_name: Ares, Laura
  last_name: Ares
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Torsten
  full_name: Meier, Torsten
  id: '344'
  last_name: Meier
  orcid: 0000-0001-8864-2072
- first_name: Polina
  full_name: Sharapova, Polina
  id: '60286'
  last_name: Sharapova
- first_name: Jan
  full_name: Sperling, Jan
  id: '75127'
  last_name: Sperling
  orcid: 0000-0002-5844-3205
citation:
  ama: Kopylov D, Offen C, Ares L, et al. Multiphoton, multimode state classification
    for nonlinear optical circuits .
  apa: Kopylov, D., Offen, C., Ares, L., Wembe Moafo, B. E., Ober-Blöbaum, S., Meier,
    T., Sharapova, P., &#38; Sperling, J. (n.d.). <i>Multiphoton, multimode state
    classification for nonlinear optical circuits </i>.
  bibtex: '@article{Kopylov_Offen_Ares_Wembe Moafo_Ober-Blöbaum_Meier_Sharapova_Sperling,
    title={Multiphoton, multimode state classification for nonlinear optical circuits
    }, author={Kopylov, Denis and Offen, Christian and Ares, Laura and Wembe Moafo,
    Boris Edgar and Ober-Blöbaum, Sina and Meier, Torsten and Sharapova, Polina and
    Sperling, Jan} }'
  chicago: Kopylov, Denis, Christian Offen, Laura Ares, Boris Edgar Wembe Moafo, Sina
    Ober-Blöbaum, Torsten Meier, Polina Sharapova, and Jan Sperling. “Multiphoton,
    Multimode State Classification for Nonlinear Optical Circuits ,” n.d.
  ieee: D. Kopylov <i>et al.</i>, “Multiphoton, multimode state classification for
    nonlinear optical circuits .” .
  mla: Kopylov, Denis, et al. <i>Multiphoton, Multimode State Classification for Nonlinear
    Optical Circuits </i>.
  short: D. Kopylov, C. Offen, L. Ares, B.E. Wembe Moafo, S. Ober-Blöbaum, T. Meier,
    P. Sharapova, J. Sperling, (n.d.).
date_created: 2025-02-10T08:26:45Z
date_updated: 2025-02-10T08:36:12Z
department:
- _id: '623'
- _id: '15'
- _id: '636'
external_id:
  arxiv:
  - '2502.05123'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.48550/arXiv.2502.05123
oa: '1'
publication_status: submitted
status: public
title: 'Multiphoton, multimode state classification for nonlinear optical circuits '
type: preprint
user_id: '85279'
year: '2025'
...
---
_id: '59794'
abstract:
- lang: eng
  text: The depth of networks plays a crucial role in the effectiveness of deep learning.
    However, the memory requirement for backpropagation scales linearly with the number
    of layers, which leads to memory bottlenecks during training. Moreover, deep networks
    are often unable to handle time-series data appearing at irregular intervals.
    These issues can be resolved by considering continuous-depth networks based on
    the neural ODE framework in combination with reversible integration methods that
    allow for variable time-steps. Reversibility of the method ensures that the memory
    requirement for training is independent of network depth, while variable time-steps
    are required for assimilating time-series data on irregular intervals. However,
    at present, there are no known higher-order reversible methods with this property.
    High-order methods are especially important when a high level of accuracy in learning
    is required or when small time-steps are necessary due to large errors in time
    integration of neural ODEs, for instance in context of complex dynamical systems
    such as Kepler systems and molecular dynamics. The requirement of small time-steps
    when using a low-order method can significantly increase the computational cost
    of training as well as inference. In this work, we present an approach for constructing
    high-order reversible methods that allow adaptive time-stepping. Our numerical
    tests show the advantages in computational speed when applied to the task of learning
    dynamical systems.
author:
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Pranav
  full_name: Singh, Pranav
  last_name: Singh
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
citation:
  ama: Maslovskaya S, Ober-Blöbaum S, Offen C, Singh P, Wembe Moafo BE. Adaptive higher
    order reversible integrators for memory efficient deep learning. Published online
    2025.
  apa: Maslovskaya, S., Ober-Blöbaum, S., Offen, C., Singh, P., &#38; Wembe Moafo,
    B. E. (2025). <i>Adaptive higher order reversible integrators for memory efficient
    deep learning</i>.
  bibtex: '@article{Maslovskaya_Ober-Blöbaum_Offen_Singh_Wembe Moafo_2025, title={Adaptive
    higher order reversible integrators for memory efficient deep learning}, author={Maslovskaya,
    Sofya and Ober-Blöbaum, Sina and Offen, Christian and Singh, Pranav and Wembe
    Moafo, Boris Edgar}, year={2025} }'
  chicago: Maslovskaya, Sofya, Sina Ober-Blöbaum, Christian Offen, Pranav Singh, and
    Boris Edgar Wembe Moafo. “Adaptive Higher Order Reversible Integrators for Memory
    Efficient Deep Learning,” 2025.
  ieee: S. Maslovskaya, S. Ober-Blöbaum, C. Offen, P. Singh, and B. E. Wembe Moafo,
    “Adaptive higher order reversible integrators for memory efficient deep learning.”
    2025.
  mla: Maslovskaya, Sofya, et al. <i>Adaptive Higher Order Reversible Integrators
    for Memory Efficient Deep Learning</i>. 2025.
  short: S. Maslovskaya, S. Ober-Blöbaum, C. Offen, P. Singh, B.E. Wembe Moafo, (2025).
date_created: 2025-05-05T09:25:28Z
date_updated: 2025-09-30T15:16:09Z
ddc:
- '510'
department:
- _id: '636'
external_id:
  arxiv:
  - '2410.09537'
file:
- access_level: closed
  content_type: application/pdf
  creator: sofyam
  date_created: 2025-05-05T09:28:02Z
  date_updated: 2025-05-05T09:28:02Z
  file_id: '59795'
  file_name: 2410.09537v2.pdf
  file_size: 1830758
  relation: main_file
  success: 1
file_date_updated: 2025-05-05T09:28:02Z
has_accepted_license: '1'
language:
- iso: eng
status: public
title: Adaptive higher order reversible integrators for memory efficient deep learning
type: preprint
user_id: '85279'
year: '2025'
...
---
_id: '62980'
abstract:
- lang: eng
  text: <jats:p>We introduce a new classification of multimode states with a fixed
    number of photons. This classification is based on the factorizability of homogeneous
    multivariate polynomials and is invariant under unitary transformations. The classes
    physically correspond to field excitations in terms of single and multiple photons,
    each of which is in an arbitrary irreducible superposition of quantized modes.
    We further show how the transitions between classes are rendered possible by photon
    addition, photon subtraction, and photon-projection nonlinearities. We explicitly
    put forward a design for a multilayer interferometer in which the states for different
    classes can be generated with state-of-the-art experimental techniques. Limitations
    of the proposed designs are analyzed using the introduced classification, providing
    a benchmark for the robustness of certain states and classes.</jats:p>
article_number: '033062'
author:
- first_name: Denis A.
  full_name: Kopylov, Denis A.
  last_name: Kopylov
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Laura
  full_name: Ares, Laura
  last_name: Ares
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Torsten
  full_name: Meier, Torsten
  id: '344'
  last_name: Meier
  orcid: 0000-0001-8864-2072
- first_name: Polina R.
  full_name: Sharapova, Polina R.
  id: '60286'
  last_name: Sharapova
- first_name: Jan
  full_name: Sperling, Jan
  id: '75127'
  last_name: Sperling
  orcid: 0000-0002-5844-3205
citation:
  ama: Kopylov DA, Offen C, Ares L, et al. Multiphoton, multimode state classification
    for nonlinear optical circuits. <i>Physical Review Research</i>. 2025;7(3). doi:<a
    href="https://doi.org/10.1103/sv6z-v1gk">10.1103/sv6z-v1gk</a>
  apa: Kopylov, D. A., Offen, C., Ares, L., Wembe Moafo, B. E., Ober-Blöbaum, S.,
    Meier, T., Sharapova, P. R., &#38; Sperling, J. (2025). Multiphoton, multimode
    state classification for nonlinear optical circuits. <i>Physical Review Research</i>,
    <i>7</i>(3), Article 033062. <a href="https://doi.org/10.1103/sv6z-v1gk">https://doi.org/10.1103/sv6z-v1gk</a>
  bibtex: '@article{Kopylov_Offen_Ares_Wembe Moafo_Ober-Blöbaum_Meier_Sharapova_Sperling_2025,
    title={Multiphoton, multimode state classification for nonlinear optical circuits},
    volume={7}, DOI={<a href="https://doi.org/10.1103/sv6z-v1gk">10.1103/sv6z-v1gk</a>},
    number={3033062}, journal={Physical Review Research}, publisher={American Physical
    Society (APS)}, author={Kopylov, Denis A. and Offen, Christian and Ares, Laura
    and Wembe Moafo, Boris Edgar and Ober-Blöbaum, Sina and Meier, Torsten and Sharapova,
    Polina R. and Sperling, Jan}, year={2025} }'
  chicago: Kopylov, Denis A., Christian Offen, Laura Ares, Boris Edgar Wembe Moafo,
    Sina Ober-Blöbaum, Torsten Meier, Polina R. Sharapova, and Jan Sperling. “Multiphoton,
    Multimode State Classification for Nonlinear Optical Circuits.” <i>Physical Review
    Research</i> 7, no. 3 (2025). <a href="https://doi.org/10.1103/sv6z-v1gk">https://doi.org/10.1103/sv6z-v1gk</a>.
  ieee: 'D. A. Kopylov <i>et al.</i>, “Multiphoton, multimode state classification
    for nonlinear optical circuits,” <i>Physical Review Research</i>, vol. 7, no.
    3, Art. no. 033062, 2025, doi: <a href="https://doi.org/10.1103/sv6z-v1gk">10.1103/sv6z-v1gk</a>.'
  mla: Kopylov, Denis A., et al. “Multiphoton, Multimode State Classification for
    Nonlinear Optical Circuits.” <i>Physical Review Research</i>, vol. 7, no. 3, 033062,
    American Physical Society (APS), 2025, doi:<a href="https://doi.org/10.1103/sv6z-v1gk">10.1103/sv6z-v1gk</a>.
  short: D.A. Kopylov, C. Offen, L. Ares, B.E. Wembe Moafo, S. Ober-Blöbaum, T. Meier,
    P.R. Sharapova, J. Sperling, Physical Review Research 7 (2025).
date_created: 2025-12-09T09:08:39Z
date_updated: 2025-12-09T09:10:01Z
department:
- _id: '15'
- _id: '569'
- _id: '170'
- _id: '293'
- _id: '706'
- _id: '636'
- _id: '35'
- _id: '230'
- _id: '429'
- _id: '623'
doi: 10.1103/sv6z-v1gk
intvolume: '         7'
issue: '3'
language:
- iso: eng
project:
- _id: '53'
  name: 'TRR 142: Maßgeschneiderte nichtlineare Photonik: Von grundlegenden Konzepten
    zu funktionellen Strukturen'
- _id: '56'
  name: TRR 142 - Project Area C
- _id: '174'
  name: 'TRR 142 ; TP: C10: Erzeugung und Charakterisierung von Quantenlicht in nichtlinearen
    Systemen: Eine theoretische Analyse'
- _id: '266'
  name: 'PhoQC: Photonisches Quantencomputing'
publication: Physical Review Research
publication_identifier:
  issn:
  - 2643-1564
publication_status: published
publisher: American Physical Society (APS)
status: public
title: Multiphoton, multimode state classification for nonlinear optical circuits
type: journal_article
user_id: '16199'
volume: 7
year: '2025'
...
---
_id: '62979'
abstract:
- lang: eng
  text: We introduce a new classification of multimode states with a fixed number
    of photons. This classification is based on the factorizability of homogeneous
    multivariate polynomials and is invariant under unitary transformations. The classes
    physically correspond to field excitations in terms of single and multiple photons,
    each of which being in an arbitrary irreducible superposition of quantized modes.
    We further show how the transitions between classes are rendered possible by photon
    addition, photon subtraction, and photon-projection nonlinearities. We explicitly
    put forward a design for a multilayer interferometer in which the states for different
    classes can be generated with state-of-the-art experimental techniques. Limitations
    of the proposed designs are analyzed using the introduced classification, providing
    a benchmark for the robustness of certain states and classes.
author:
- first_name: Torsten
  full_name: Meier, Torsten
  id: '344'
  last_name: Meier
  orcid: 0000-0001-8864-2072
- first_name: Polina R.
  full_name: Sharapova, Polina R.
  id: '60286'
  last_name: Sharapova
- first_name: Jan
  full_name: Sperling, Jan
  id: '75127'
  last_name: Sperling
  orcid: 0000-0002-5844-3205
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
citation:
  ama: Meier T, Sharapova PR, Sperling J, Ober-Blöbaum S, Wembe Moafo BE, Offen C.
    Multiphoton, multimode state classification for nonlinear optical circuits. Published
    online 2025.
  apa: Meier, T., Sharapova, P. R., Sperling, J., Ober-Blöbaum, S., Wembe Moafo, B.
    E., &#38; Offen, C. (2025). <i>Multiphoton, multimode state classification for
    nonlinear optical circuits</i>.
  bibtex: '@article{Meier_Sharapova_Sperling_Ober-Blöbaum_Wembe Moafo_Offen_2025,
    title={Multiphoton, multimode state classification for nonlinear optical circuits},
    author={Meier, Torsten and Sharapova, Polina R. and Sperling, Jan and Ober-Blöbaum,
    Sina and Wembe Moafo, Boris Edgar and Offen, Christian}, year={2025} }'
  chicago: Meier, Torsten, Polina R. Sharapova, Jan Sperling, Sina Ober-Blöbaum, Boris
    Edgar Wembe Moafo, and Christian Offen. “Multiphoton, Multimode State Classification
    for Nonlinear Optical Circuits,” 2025.
  ieee: T. Meier, P. R. Sharapova, J. Sperling, S. Ober-Blöbaum, B. E. Wembe Moafo,
    and C. Offen, “Multiphoton, multimode state classification for nonlinear optical
    circuits.” 2025.
  mla: Meier, Torsten, et al. <i>Multiphoton, Multimode State Classification for Nonlinear
    Optical Circuits</i>. 2025.
  short: T. Meier, P.R. Sharapova, J. Sperling, S. Ober-Blöbaum, B.E. Wembe Moafo,
    C. Offen, (2025).
date_created: 2025-12-09T08:59:27Z
date_updated: 2025-12-09T09:10:23Z
department:
- _id: '15'
- _id: '170'
- _id: '293'
- _id: '706'
- _id: '636'
- _id: '230'
- _id: '623'
- _id: '429'
- _id: '35'
language:
- iso: eng
project:
- _id: '53'
  name: 'TRR 142: Maßgeschneiderte nichtlineare Photonik: Von grundlegenden Konzepten
    zu funktionellen Strukturen'
- _id: '56'
  name: TRR 142 - Project Area C
- _id: '174'
  name: 'TRR 142 ; TP: C10: Erzeugung und Charakterisierung von Quantenlicht in nichtlinearen
    Systemen: Eine theoretische Analyse'
- _id: '266'
  name: 'PhoQC: Photonisches Quantencomputing'
status: public
title: Multiphoton, multimode state classification for nonlinear optical circuits
type: preprint
user_id: '16199'
year: '2025'
...
---
_id: '59507'
abstract:
- lang: eng
  text: Differential equations posed on quadratic matrix Lie groups arise in the context
    of classical mechanics and quantum dynamical systems. Lie group numerical integrators
    preserve the constants of motions defining the Lie group. Thus, they respect important
    physical laws of the dynamical system, such as unitarity and energy conservation
    in the context of quantum dynamical systems, for instance. In this article we
    develop a high-order commutator free Lie group integrator for non-autonomous differential
    equations evolving on quadratic Lie groups. Instead of matrix exponentials, which
    are expensive to evaluate and need to be approximated by appropriate rational
    functions in order to preserve the Lie group structure, the proposed method is
    obtained as a composition of Cayley transforms which naturally respect the structure
    of quadratic Lie groups while being computationally efficient to evaluate. Unlike
    Cayley-Magnus methods the method is also free from nested matrix commutators.
author:
- first_name: Boris Edgar
  full_name: Wembe Moafo, Boris Edgar
  id: '95394'
  last_name: Wembe Moafo
- first_name: 'Cristian '
  full_name: 'Offen, Cristian '
  last_name: Offen
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Pranav
  full_name: Singh, Pranav
  last_name: Singh
citation:
  ama: Wembe Moafo BE, Offen C, Maslovskaya S, Ober-Blöbaum S, Singh P. Commutator-free
    Cayley methods. <i>J Comput Appl Math</i>. 477(15). doi:<a href="https://doi.org/10.1016/j.cam.2025.117184">10.1016/j.cam.2025.117184</a>
  apa: Wembe Moafo, B. E., Offen, C., Maslovskaya, S., Ober-Blöbaum, S., &#38; Singh,
    P. (n.d.). Commutator-free Cayley methods. <i>J. Comput. Appl. Math</i>, <i>477</i>(15).
    <a href="https://doi.org/10.1016/j.cam.2025.117184">https://doi.org/10.1016/j.cam.2025.117184</a>
  bibtex: '@article{Wembe Moafo_Offen_Maslovskaya_Ober-Blöbaum_Singh, title={Commutator-free
    Cayley methods}, volume={477}, DOI={<a href="https://doi.org/10.1016/j.cam.2025.117184">10.1016/j.cam.2025.117184</a>},
    number={15}, journal={J. Comput. Appl. Math}, author={Wembe Moafo, Boris Edgar
    and Offen, Cristian  and Maslovskaya, Sofya and Ober-Blöbaum, Sina and Singh,
    Pranav} }'
  chicago: Wembe Moafo, Boris Edgar, Cristian  Offen, Sofya Maslovskaya, Sina Ober-Blöbaum,
    and Pranav Singh. “Commutator-Free Cayley Methods.” <i>J. Comput. Appl. Math</i>
    477, no. 15 (n.d.). <a href="https://doi.org/10.1016/j.cam.2025.117184">https://doi.org/10.1016/j.cam.2025.117184</a>.
  ieee: 'B. E. Wembe Moafo, C. Offen, S. Maslovskaya, S. Ober-Blöbaum, and P. Singh,
    “Commutator-free Cayley methods,” <i>J. Comput. Appl. Math</i>, vol. 477, no.
    15, doi: <a href="https://doi.org/10.1016/j.cam.2025.117184">10.1016/j.cam.2025.117184</a>.'
  mla: Wembe Moafo, Boris Edgar, et al. “Commutator-Free Cayley Methods.” <i>J. Comput.
    Appl. Math</i>, vol. 477, no. 15, doi:<a href="https://doi.org/10.1016/j.cam.2025.117184">10.1016/j.cam.2025.117184</a>.
  short: B.E. Wembe Moafo, C. Offen, S. Maslovskaya, S. Ober-Blöbaum, P. Singh, J.
    Comput. Appl. Math 477 (n.d.).
date_created: 2025-04-10T14:42:52Z
date_updated: 2025-12-16T15:17:27Z
department:
- _id: '94'
doi: 10.1016/j.cam.2025.117184
intvolume: '       477'
issue: '15'
language:
- iso: eng
publication: J. Comput. Appl. Math
publication_status: submitted
status: public
title: Commutator-free Cayley methods
type: journal_article
user_id: '95394'
volume: 477
year: '2025'
...
---
_id: '59797'
author:
- first_name: Michael
  full_name: Konopik, Michael
  last_name: Konopik
- first_name: Rodrigo
  full_name: T. Sato Martín de Almagro, Rodrigo
  last_name: T. Sato Martín de Almagro
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Sigrid
  full_name: Leyendecker, Sigrid
  last_name: Leyendecker
citation:
  ama: Konopik M, T. Sato Martín de Almagro R, Maslovskaya S, Ober-Blöbaum S, Leyendecker
    S. Variational integrators for a new Lagrangian approach to control affine systems
    with a quadratic Lagrange term. <i>Journal of Nonlinear Science</i>. 2025;36(11).
    doi:<a href="https://doi.org/10.1007/s00332-025-10229-5">10.1007/s00332-025-10229-5</a>
  apa: Konopik, M., T. Sato Martín de Almagro, R., Maslovskaya, S., Ober-Blöbaum,
    S., &#38; Leyendecker, S. (2025). Variational integrators for a new Lagrangian
    approach to control affine systems with a quadratic Lagrange term. <i>Journal
    of Nonlinear Science</i>, <i>36</i>(11). <a href="https://doi.org/10.1007/s00332-025-10229-5">https://doi.org/10.1007/s00332-025-10229-5</a>
  bibtex: '@article{Konopik_T. Sato Martín de Almagro_Maslovskaya_Ober-Blöbaum_Leyendecker_2025,
    title={Variational integrators for a new Lagrangian approach to control affine
    systems with a quadratic Lagrange term}, volume={36}, DOI={<a href="https://doi.org/10.1007/s00332-025-10229-5">10.1007/s00332-025-10229-5</a>},
    number={11}, journal={Journal of Nonlinear Science}, author={Konopik, Michael
    and T. Sato Martín de Almagro, Rodrigo and Maslovskaya, Sofya and Ober-Blöbaum,
    Sina and Leyendecker, Sigrid}, year={2025} }'
  chicago: Konopik, Michael, Rodrigo T. Sato Martín de Almagro, Sofya Maslovskaya,
    Sina Ober-Blöbaum, and Sigrid Leyendecker. “Variational Integrators for a New
    Lagrangian Approach to Control Affine Systems with a Quadratic Lagrange Term.”
    <i>Journal of Nonlinear Science</i> 36, no. 11 (2025). <a href="https://doi.org/10.1007/s00332-025-10229-5">https://doi.org/10.1007/s00332-025-10229-5</a>.
  ieee: 'M. Konopik, R. T. Sato Martín de Almagro, S. Maslovskaya, S. Ober-Blöbaum,
    and S. Leyendecker, “Variational integrators for a new Lagrangian approach to
    control affine systems with a quadratic Lagrange term,” <i>Journal of Nonlinear
    Science</i>, vol. 36, no. 11, 2025, doi: <a href="https://doi.org/10.1007/s00332-025-10229-5">10.1007/s00332-025-10229-5</a>.'
  mla: Konopik, Michael, et al. “Variational Integrators for a New Lagrangian Approach
    to Control Affine Systems with a Quadratic Lagrange Term.” <i>Journal of Nonlinear
    Science</i>, vol. 36, no. 11, 2025, doi:<a href="https://doi.org/10.1007/s00332-025-10229-5">10.1007/s00332-025-10229-5</a>.
  short: M. Konopik, R. T. Sato Martín de Almagro, S. Maslovskaya, S. Ober-Blöbaum,
    S. Leyendecker, Journal of Nonlinear Science 36 (2025).
date_created: 2025-05-05T09:35:31Z
date_updated: 2026-01-06T18:26:57Z
department:
- _id: '636'
doi: 10.1007/s00332-025-10229-5
intvolume: '        36'
issue: '11'
language:
- iso: eng
publication: Journal of Nonlinear Science
status: public
title: Variational integrators for a new Lagrangian approach to control affine systems
  with a quadratic Lagrange term
type: journal_article
user_id: '87909'
volume: 36
year: '2025'
...
---
_id: '59799'
author:
- first_name: Michael
  full_name: Konopik, Michael
  last_name: Konopik
- first_name: Sigrid
  full_name: Leyendecker, Sigrid
  last_name: Leyendecker
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Rodrigo
  full_name: T. Sato Martín de Almagro, Rodrigo
  last_name: T. Sato Martín de Almagro
citation:
  ama: Konopik M, Leyendecker S, Maslovskaya S, Ober-Blöbaum S, T. Sato Martín de
    Almagro R. A new Lagrangian approach to optimal control of second-order systems.
    <i>Nonlinearity</i>. 2025;38(11). doi:<a href="https://doi.org/10.1088/1361-6544/ae1d08">10.1088/1361-6544/ae1d08</a>
  apa: Konopik, M., Leyendecker, S., Maslovskaya, S., Ober-Blöbaum, S., &#38; T. Sato
    Martín de Almagro, R. (2025). A new Lagrangian approach to optimal control of
    second-order systems. <i>Nonlinearity</i>, <i>38</i>(11). <a href="https://doi.org/10.1088/1361-6544/ae1d08">https://doi.org/10.1088/1361-6544/ae1d08</a>
  bibtex: '@article{Konopik_Leyendecker_Maslovskaya_Ober-Blöbaum_T. Sato Martín de
    Almagro_2025, title={A new Lagrangian approach to optimal control of second-order
    systems}, volume={38}, DOI={<a href="https://doi.org/10.1088/1361-6544/ae1d08">10.1088/1361-6544/ae1d08</a>},
    number={11}, journal={Nonlinearity}, author={Konopik, Michael and Leyendecker,
    Sigrid and Maslovskaya, Sofya and Ober-Blöbaum, Sina and T. Sato Martín de Almagro,
    Rodrigo}, year={2025} }'
  chicago: Konopik, Michael, Sigrid Leyendecker, Sofya Maslovskaya, Sina Ober-Blöbaum,
    and Rodrigo T. Sato Martín de Almagro. “A New Lagrangian Approach to Optimal Control
    of Second-Order Systems.” <i>Nonlinearity</i> 38, no. 11 (2025). <a href="https://doi.org/10.1088/1361-6544/ae1d08">https://doi.org/10.1088/1361-6544/ae1d08</a>.
  ieee: 'M. Konopik, S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, and R. T. Sato
    Martín de Almagro, “A new Lagrangian approach to optimal control of second-order
    systems,” <i>Nonlinearity</i>, vol. 38, no. 11, 2025, doi: <a href="https://doi.org/10.1088/1361-6544/ae1d08">10.1088/1361-6544/ae1d08</a>.'
  mla: Konopik, Michael, et al. “A New Lagrangian Approach to Optimal Control of Second-Order
    Systems.” <i>Nonlinearity</i>, vol. 38, no. 11, 2025, doi:<a href="https://doi.org/10.1088/1361-6544/ae1d08">10.1088/1361-6544/ae1d08</a>.
  short: M. Konopik, S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, R. T. Sato Martín
    de Almagro, Nonlinearity 38 (2025).
date_created: 2025-05-05T09:37:50Z
date_updated: 2026-01-06T18:24:40Z
department:
- _id: '636'
doi: 10.1088/1361-6544/ae1d08
intvolume: '        38'
issue: '11'
language:
- iso: eng
publication: Nonlinearity
status: public
title: A new Lagrangian approach to optimal control of second-order systems
type: journal_article
user_id: '87909'
volume: 38
year: '2025'
...
---
_id: '53101'
abstract:
- lang: eng
  text: In this work, we consider optimal control problems for mechanical systems
    with fixed initial and free final state and a quadratic Lagrange term. Specifically,
    the dynamics is described by a second order ODE containing an affine control term.
    Classically, Pontryagin's maximum principle gives necessary optimality conditions
    for the optimal control problem. For smooth problems, alternatively, a variational
    approach based on an augmented objective can be followed. Here, we propose a new
    Lagrangian approach leading to equivalent necessary optimality conditions in the
    form of Euler-Lagrange equations. Thus, the differential geometric structure (similar
    to classical Lagrangian dynamics) can be exploited in the framework of optimal
    control problems. In particular, the formulation enables the symplectic discretisation
    of the optimal control problem via variational integrators in a straightforward
    way.
article_type: original
author:
- first_name: Sigrid
  full_name: Leyendecker, Sigrid
  last_name: Leyendecker
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Rodrigo T. Sato Martín de
  full_name: Almagro, Rodrigo T. Sato Martín de
  last_name: Almagro
- first_name: Flóra Orsolya
  full_name: Szemenyei, Flóra Orsolya
  last_name: Szemenyei
citation:
  ama: Leyendecker S, Maslovskaya S, Ober-Blöbaum S, Almagro RTSM de, Szemenyei FO.
    A new Lagrangian approach to control affine systems with a quadratic Lagrange
    term. <i>Journal of Computational Dynamics</i>. 2024;0(0):0-0. doi:<a href="https://doi.org/10.3934/jcd.2024017">10.3934/jcd.2024017</a>
  apa: Leyendecker, S., Maslovskaya, S., Ober-Blöbaum, S., Almagro, R. T. S. M. de,
    &#38; Szemenyei, F. O. (2024). A new Lagrangian approach to control affine systems
    with a quadratic Lagrange term. <i>Journal of Computational Dynamics</i>, <i>0</i>(0),
    0–0. <a href="https://doi.org/10.3934/jcd.2024017">https://doi.org/10.3934/jcd.2024017</a>
  bibtex: '@article{Leyendecker_Maslovskaya_Ober-Blöbaum_Almagro_Szemenyei_2024, title={A
    new Lagrangian approach to control affine systems with a quadratic Lagrange term},
    volume={0}, DOI={<a href="https://doi.org/10.3934/jcd.2024017">10.3934/jcd.2024017</a>},
    number={0}, journal={Journal of Computational Dynamics}, publisher={American Institute
    of Mathematical Sciences (AIMS)}, author={Leyendecker, Sigrid and Maslovskaya,
    Sofya and Ober-Blöbaum, Sina and Almagro, Rodrigo T. Sato Martín de and Szemenyei,
    Flóra Orsolya}, year={2024}, pages={0–0} }'
  chicago: 'Leyendecker, Sigrid, Sofya Maslovskaya, Sina Ober-Blöbaum, Rodrigo T.
    Sato Martín de Almagro, and Flóra Orsolya Szemenyei. “A New Lagrangian Approach
    to Control Affine Systems with a Quadratic Lagrange Term.” <i>Journal of Computational
    Dynamics</i> 0, no. 0 (2024): 0–0. <a href="https://doi.org/10.3934/jcd.2024017">https://doi.org/10.3934/jcd.2024017</a>.'
  ieee: 'S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, R. T. S. M. de Almagro,
    and F. O. Szemenyei, “A new Lagrangian approach to control affine systems with
    a quadratic Lagrange term,” <i>Journal of Computational Dynamics</i>, vol. 0,
    no. 0, pp. 0–0, 2024, doi: <a href="https://doi.org/10.3934/jcd.2024017">10.3934/jcd.2024017</a>.'
  mla: Leyendecker, Sigrid, et al. “A New Lagrangian Approach to Control Affine Systems
    with a Quadratic Lagrange Term.” <i>Journal of Computational Dynamics</i>, vol.
    0, no. 0, American Institute of Mathematical Sciences (AIMS), 2024, pp. 0–0, doi:<a
    href="https://doi.org/10.3934/jcd.2024017">10.3934/jcd.2024017</a>.
  short: S. Leyendecker, S. Maslovskaya, S. Ober-Blöbaum, R.T.S.M. de Almagro, F.O.
    Szemenyei, Journal of Computational Dynamics 0 (2024) 0–0.
date_created: 2024-03-28T15:58:02Z
date_updated: 2024-03-28T16:07:34Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.3934/jcd.2024017
has_accepted_license: '1'
issue: '0'
keyword:
- Optimal control problem
- Lagrangian system
- Hamiltonian system
- Variations
- Pontryagin's maximum principle.
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://www.aimsciences.org/article/doi/10.3934/jcd.2024017
oa: '1'
page: 0-0
publication: Journal of Computational Dynamics
publication_identifier:
  issn:
  - 2158-2491
  - 2158-2505
publication_status: published
publisher: American Institute of Mathematical Sciences (AIMS)
status: public
title: A new Lagrangian approach to control affine systems with a quadratic Lagrange
  term
type: journal_article
user_id: '87909'
volume: '0'
year: '2024'
...
---
_id: '46469'
abstract:
- lang: eng
  text: 'We show how to learn discrete field theories from observational data of fields
    on a space-time lattice. For this, we train a neural network model of a discrete
    Lagrangian density such that the discrete Euler--Lagrange equations are consistent
    with the given training data. We, thus, obtain a structure-preserving machine
    learning architecture. Lagrangian densities are not uniquely defined by the solutions
    of a field theory. We introduce a technique to derive regularisers for the training
    process which optimise numerical regularity of the discrete field theory. Minimisation
    of the regularisers guarantees that close to the training data the discrete field
    theory behaves robust and efficient when used in numerical simulations. Further,
    we show how to identify structurally simple solutions of the underlying continuous
    field theory such as travelling waves. This is possible even when travelling waves
    are not present in the training data. This is compared to data-driven model order
    reduction based approaches, which struggle to identify suitable latent spaces
    containing structurally simple solutions when these are not present in the training
    data. Ideas are demonstrated on examples based on the wave equation and the Schrödinger
    equation. '
article_number: '013104'
article_type: original
author:
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
citation:
  ama: Offen C, Ober-Blöbaum S. Learning of discrete models of variational PDEs from
    data. <i>Chaos</i>. 2024;34(1). doi:<a href="https://doi.org/10.1063/5.0172287">10.1063/5.0172287</a>
  apa: Offen, C., &#38; Ober-Blöbaum, S. (2024). Learning of discrete models of variational
    PDEs from data. <i>Chaos</i>, <i>34</i>(1), Article 013104. <a href="https://doi.org/10.1063/5.0172287">https://doi.org/10.1063/5.0172287</a>
  bibtex: '@article{Offen_Ober-Blöbaum_2024, title={Learning of discrete models of
    variational PDEs from data}, volume={34}, DOI={<a href="https://doi.org/10.1063/5.0172287">10.1063/5.0172287</a>},
    number={1013104}, journal={Chaos}, publisher={AIP Publishing}, author={Offen,
    Christian and Ober-Blöbaum, Sina}, year={2024} }'
  chicago: Offen, Christian, and Sina Ober-Blöbaum. “Learning of Discrete Models of
    Variational PDEs from Data.” <i>Chaos</i> 34, no. 1 (2024). <a href="https://doi.org/10.1063/5.0172287">https://doi.org/10.1063/5.0172287</a>.
  ieee: 'C. Offen and S. Ober-Blöbaum, “Learning of discrete models of variational
    PDEs from data,” <i>Chaos</i>, vol. 34, no. 1, Art. no. 013104, 2024, doi: <a
    href="https://doi.org/10.1063/5.0172287">10.1063/5.0172287</a>.'
  mla: Offen, Christian, and Sina Ober-Blöbaum. “Learning of Discrete Models of Variational
    PDEs from Data.” <i>Chaos</i>, vol. 34, no. 1, 013104, AIP Publishing, 2024, doi:<a
    href="https://doi.org/10.1063/5.0172287">10.1063/5.0172287</a>.
  short: C. Offen, S. Ober-Blöbaum, Chaos 34 (2024).
date_created: 2023-08-10T08:24:48Z
date_updated: 2024-08-12T13:45:43Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.1063/5.0172287
external_id:
  arxiv:
  - '2308.05082 '
file:
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2024-01-09T10:48:38Z
  date_updated: 2024-01-09T10:48:38Z
  file_id: '50376'
  file_name: Accepted manuscript with AIP banner CHA23-AR-01370.pdf
  file_size: 13222105
  relation: main_file
  title: Accepted Manuscript Chaos
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2024-01-09T11:19:49Z
  date_updated: 2024-01-09T11:19:49Z
  description: |-
    We show how to learn discrete field theories from observational data of fields on a space-time lattice. For this, we train
    a neural network model of a discrete Lagrangian density such that the discrete Euler–Lagrange equations are consistent
    with the given training data. We, thus, obtain a structure-preserving machine learning architecture. Lagrangian
    densities are not uniquely defined by the solutions of a field theory. We introduce a technique to derive regularisers for
    the training process which optimise numerical regularity of the discrete field theory. Minimisation of the regularisers
    guarantees that close to the training data the discrete field theory behaves robust and efficient when used in numerical
    simulations. Further, we show how to identify structurally simple solutions of the underlying continuous field theory
    such as travelling waves. This is possible even when travelling waves are not present in the training data. This is
    compared to data-driven model order reduction based approaches, which struggle to identify suitable latent spaces
    containing structurally simple solutions when these are not present in the training data. Ideas are demonstrated on
    examples based on the wave equation and the Schrödinger equation.
  file_id: '50390'
  file_name: LDensityPDE_AIP.pdf
  file_size: 12960884
  relation: main_file
  title: Learning of discrete models of variational PDEs from data
file_date_updated: 2024-01-09T11:19:49Z
has_accepted_license: '1'
intvolume: '        34'
issue: '1'
language:
- iso: eng
oa: '1'
project:
- _id: '52'
  name: 'PC2: Computing Resources Provided by the Paderborn Center for Parallel Computing'
publication: Chaos
publication_identifier:
  issn:
  - 1054-1500
publication_status: published
publisher: AIP Publishing
quality_controlled: '1'
related_material:
  link:
  - description: GitHub
    relation: software
    url: https://github.com/Christian-Offen/DLNN_pde
status: public
title: Learning of discrete models of variational PDEs from data
type: journal_article
user_id: '85279'
volume: 34
year: '2024'
...
---
_id: '59791'
author:
- first_name: Sofya
  full_name: Maslovskaya, Sofya
  id: '87909'
  last_name: Maslovskaya
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
citation:
  ama: 'Maslovskaya S, Ober-Blöbaum S. Symplectic Methods in Deep Learning. In: <i>IFAC-PapersOnLine</i>.
    Vol 58. Elsevier BV; 2024:85-90. doi:<a href="https://doi.org/10.1016/j.ifacol.2024.10.118">10.1016/j.ifacol.2024.10.118</a>'
  apa: Maslovskaya, S., &#38; Ober-Blöbaum, S. (2024). Symplectic Methods in Deep
    Learning. <i>IFAC-PapersOnLine</i>, <i>58</i>(17), 85–90. <a href="https://doi.org/10.1016/j.ifacol.2024.10.118">https://doi.org/10.1016/j.ifacol.2024.10.118</a>
  bibtex: '@inproceedings{Maslovskaya_Ober-Blöbaum_2024, title={Symplectic Methods
    in Deep Learning}, volume={58}, DOI={<a href="https://doi.org/10.1016/j.ifacol.2024.10.118">10.1016/j.ifacol.2024.10.118</a>},
    number={17}, booktitle={IFAC-PapersOnLine}, publisher={Elsevier BV}, author={Maslovskaya,
    Sofya and Ober-Blöbaum, Sina}, year={2024}, pages={85–90} }'
  chicago: Maslovskaya, Sofya, and Sina Ober-Blöbaum. “Symplectic Methods in Deep
    Learning.” In <i>IFAC-PapersOnLine</i>, 58:85–90. Elsevier BV, 2024. <a href="https://doi.org/10.1016/j.ifacol.2024.10.118">https://doi.org/10.1016/j.ifacol.2024.10.118</a>.
  ieee: 'S. Maslovskaya and S. Ober-Blöbaum, “Symplectic Methods in Deep Learning,”
    in <i>IFAC-PapersOnLine</i>, 2024, vol. 58, no. 17, pp. 85–90, doi: <a href="https://doi.org/10.1016/j.ifacol.2024.10.118">10.1016/j.ifacol.2024.10.118</a>.'
  mla: Maslovskaya, Sofya, and Sina Ober-Blöbaum. “Symplectic Methods in Deep Learning.”
    <i>IFAC-PapersOnLine</i>, vol. 58, no. 17, Elsevier BV, 2024, pp. 85–90, doi:<a
    href="https://doi.org/10.1016/j.ifacol.2024.10.118">10.1016/j.ifacol.2024.10.118</a>.
  short: 'S. Maslovskaya, S. Ober-Blöbaum, in: IFAC-PapersOnLine, Elsevier BV, 2024,
    pp. 85–90.'
date_created: 2025-05-05T09:21:13Z
date_updated: 2025-05-05T09:22:27Z
department:
- _id: '636'
doi: 10.1016/j.ifacol.2024.10.118
intvolume: '        58'
issue: '17'
language:
- iso: eng
page: 85-90
publication: IFAC-PapersOnLine
publication_identifier:
  issn:
  - 2405-8963
publication_status: published
publisher: Elsevier BV
status: public
title: Symplectic Methods in Deep Learning
type: conference
user_id: '87909'
volume: 58
year: '2024'
...
---
_id: '34135'
abstract:
- lang: eng
  text: By one of the most fundamental principles in physics, a dynamical system will
    exhibit those motions which extremise an action functional. This leads to the
    formation of the Euler-Lagrange equations, which serve as a model of how the system
    will behave in time. If the dynamics exhibit additional symmetries, then the motion
    fulfils additional conservation laws, such as conservation of energy (time invariance),
    momentum (translation invariance), or angular momentum (rotational invariance).
    To learn a system representation, one could learn the discrete Euler-Lagrange
    equations, or alternatively, learn the discrete Lagrangian function Ld which defines
    them. Based on ideas from Lie group theory, in this work we introduce a framework
    to learn a discrete Lagrangian along with its symmetry group from discrete observations
    of motions and, therefore, identify conserved quantities. The learning process
    does not restrict the form of the Lagrangian, does not require velocity or momentum
    observations or predictions and incorporates a cost term which safeguards against
    unwanted solutions and against potential numerical issues in forward simulations.
    The learnt discrete quantities are related to their continuous analogues using
    variational backward error analysis and numerical results demonstrate the improvement
    such models can have both qualitatively and quantitatively even in the presence
    of noise.
author:
- first_name: Yana
  full_name: Lishkova, Yana
  last_name: Lishkova
- first_name: Paul
  full_name: Scherer, Paul
  last_name: Scherer
- first_name: Steffen
  full_name: Ridderbusch, Steffen
  last_name: Ridderbusch
- first_name: Mateja
  full_name: Jamnik, Mateja
  last_name: Jamnik
- first_name: Pietro
  full_name: Liò, Pietro
  last_name: Liò
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
citation:
  ama: 'Lishkova Y, Scherer P, Ridderbusch S, et al. Discrete Lagrangian Neural Networks
    with Automatic Symmetry Discovery. In: <i>IFAC-PapersOnLine</i>. Vol 56. Elsevier;
    2023:3203-3210. doi:<a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">10.1016/j.ifacol.2023.10.1457</a>'
  apa: Lishkova, Y., Scherer, P., Ridderbusch, S., Jamnik, M., Liò, P., Ober-Blöbaum,
    S., &#38; Offen, C. (2023). Discrete Lagrangian Neural Networks with Automatic
    Symmetry Discovery. <i>IFAC-PapersOnLine</i>, <i>56</i>(2), 3203–3210. <a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">https://doi.org/10.1016/j.ifacol.2023.10.1457</a>
  bibtex: '@inproceedings{Lishkova_Scherer_Ridderbusch_Jamnik_Liò_Ober-Blöbaum_Offen_2023,
    title={Discrete Lagrangian Neural Networks with Automatic Symmetry Discovery},
    volume={56}, DOI={<a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">10.1016/j.ifacol.2023.10.1457</a>},
    number={2}, booktitle={IFAC-PapersOnLine}, publisher={Elsevier}, author={Lishkova,
    Yana and Scherer, Paul and Ridderbusch, Steffen and Jamnik, Mateja and Liò, Pietro
    and Ober-Blöbaum, Sina and Offen, Christian}, year={2023}, pages={3203–3210} }'
  chicago: Lishkova, Yana, Paul Scherer, Steffen Ridderbusch, Mateja Jamnik, Pietro
    Liò, Sina Ober-Blöbaum, and Christian Offen. “Discrete Lagrangian Neural Networks
    with Automatic Symmetry Discovery.” In <i>IFAC-PapersOnLine</i>, 56:3203–10. Elsevier,
    2023. <a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">https://doi.org/10.1016/j.ifacol.2023.10.1457</a>.
  ieee: 'Y. Lishkova <i>et al.</i>, “Discrete Lagrangian Neural Networks with Automatic
    Symmetry Discovery,” in <i>IFAC-PapersOnLine</i>,  Yokohama, Japan, 2023, vol.
    56, no. 2, pp. 3203–3210, doi: <a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">10.1016/j.ifacol.2023.10.1457</a>.'
  mla: Lishkova, Yana, et al. “Discrete Lagrangian Neural Networks with Automatic
    Symmetry Discovery.” <i>IFAC-PapersOnLine</i>, vol. 56, no. 2, Elsevier, 2023,
    pp. 3203–10, doi:<a href="https://doi.org/10.1016/j.ifacol.2023.10.1457">10.1016/j.ifacol.2023.10.1457</a>.
  short: 'Y. Lishkova, P. Scherer, S. Ridderbusch, M. Jamnik, P. Liò, S. Ober-Blöbaum,
    C. Offen, in: IFAC-PapersOnLine, Elsevier, 2023, pp. 3203–3210.'
conference:
  end_date: 2023-07-14
  location: ' Yokohama, Japan'
  name: The 22nd World Congress of the International Federation of Automatic Control
  start_date: 2023-07-09
date_created: 2022-11-23T08:17:10Z
date_updated: 2023-12-29T14:26:00Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.1016/j.ifacol.2023.10.1457
external_id:
  arxiv:
  - '2211.10830'
file:
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2023-04-17T08:05:55Z
  date_updated: 2023-04-17T08:05:55Z
  description: |-
    By one of the most fundamental principles in physics, a dynamical system will
    exhibit those motions which extremise an action functional. This leads to the formation of
    the Euler-Lagrange equations, which serve as a model of how the system will behave in time.
    If the dynamics exhibit additional symmetries, then the motion fulfils additional conservation
    laws, such as conservation of energy (time invariance), momentum (translation invariance), or
    angular momentum (rotational invariance). To learn a system representation, one could learn
    the discrete Euler-Lagrange equations, or alternatively, learn the discrete Lagrangian function
    Ld which defines them. Based on ideas from Lie group theory, we introduce a framework to learn
    a discrete Lagrangian along with its symmetry group from discrete observations of motions and,
    therefore, identify conserved quantities. The learning process does not restrict the form of the
    Lagrangian, does not require velocity or momentum observations or predictions and incorporates
    a cost term which safeguards against unwanted solutions and against potential numerical issues
    in forward simulations. The learnt discrete quantities are related to their continuous analogues
    using variational backward error analysis and numerical results demonstrate the improvement
    such models can have both qualitatively and quantitatively even in the presence of noise.
  file_id: '44037'
  file_name: LNN_project.pdf
  file_size: 576115
  relation: main_file
  title: Discrete Lagrangian Neural Networks with Automatic Symmetry Discovery
file_date_updated: 2023-04-17T08:05:55Z
has_accepted_license: '1'
intvolume: '        56'
issue: '2'
language:
- iso: eng
main_file_link:
- url: https://www.sciencedirect.com/science/article/pii/S2405896323018657
oa: '1'
page: 3203-3210
publication: IFAC-PapersOnLine
publication_status: published
publisher: Elsevier
quality_controlled: '1'
related_material:
  link:
  - description: GitHub
    relation: software
    url: https://github.com/yanalish/SymDLNN
status: public
title: Discrete Lagrangian Neural Networks with Automatic Symmetry Discovery
type: conference
user_id: '85279'
volume: 56
year: '2023'
...
---
_id: '42163'
abstract:
- lang: eng
  text: 'The article shows how to learn models of dynamical systems from data which
    are governed by an unknown variational PDE. Rather than employing reduction techniques,
    we learn a discrete field theory governed by a discrete Lagrangian density $L_d$
    that is modelled as a neural network. Careful regularisation of the loss function
    for training $L_d$ is necessary to obtain a field theory that is suitable for
    numerical computations: we derive a regularisation term which optimises the solvability
    of the discrete Euler--Lagrange equations. Secondly, we develop a method to find
    solutions to machine learned discrete field theories which constitute travelling
    waves of the underlying continuous PDE.'
author:
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
citation:
  ama: 'Offen C, Ober-Blöbaum S. Learning discrete Lagrangians for variational PDEs
    from data and detection of travelling waves. In: Nielsen F, Barbaresco F, eds.
    <i>Geometric Science of Information</i>. Vol 14071. Lecture Notes in Computer
    Science (LNCS). Springer, Cham.; 2023:569-579. doi:<a href="https://doi.org/10.1007/978-3-031-38271-0_57">10.1007/978-3-031-38271-0_57</a>'
  apa: Offen, C., &#38; Ober-Blöbaum, S. (2023). Learning discrete Lagrangians for
    variational PDEs from data and detection of travelling waves. In F. Nielsen &#38;
    F. Barbaresco (Eds.), <i>Geometric Science of Information</i> (Vol. 14071, pp.
    569–579). Springer, Cham. <a href="https://doi.org/10.1007/978-3-031-38271-0_57">https://doi.org/10.1007/978-3-031-38271-0_57</a>
  bibtex: '@inproceedings{Offen_Ober-Blöbaum_2023, series={Lecture Notes in Computer
    Science (LNCS)}, title={Learning discrete Lagrangians for variational PDEs from
    data and detection of travelling waves}, volume={14071}, DOI={<a href="https://doi.org/10.1007/978-3-031-38271-0_57">10.1007/978-3-031-38271-0_57</a>},
    booktitle={Geometric Science of Information}, publisher={Springer, Cham.}, author={Offen,
    Christian and Ober-Blöbaum, Sina}, editor={Nielsen, F and Barbaresco, F}, year={2023},
    pages={569–579}, collection={Lecture Notes in Computer Science (LNCS)} }'
  chicago: Offen, Christian, and Sina Ober-Blöbaum. “Learning Discrete Lagrangians
    for Variational PDEs from Data and Detection of Travelling Waves.” In <i>Geometric
    Science of Information</i>, edited by F Nielsen and F Barbaresco, 14071:569–79.
    Lecture Notes in Computer Science (LNCS). Springer, Cham., 2023. <a href="https://doi.org/10.1007/978-3-031-38271-0_57">https://doi.org/10.1007/978-3-031-38271-0_57</a>.
  ieee: 'C. Offen and S. Ober-Blöbaum, “Learning discrete Lagrangians for variational
    PDEs from data and detection of travelling waves,” in <i>Geometric Science of
    Information</i>, Saint-Malo, Palais du Grand Large, France, 2023, vol. 14071,
    pp. 569–579, doi: <a href="https://doi.org/10.1007/978-3-031-38271-0_57">10.1007/978-3-031-38271-0_57</a>.'
  mla: Offen, Christian, and Sina Ober-Blöbaum. “Learning Discrete Lagrangians for
    Variational PDEs from Data and Detection of Travelling Waves.” <i>Geometric Science
    of Information</i>, edited by F Nielsen and F Barbaresco, vol. 14071, Springer,
    Cham., 2023, pp. 569–79, doi:<a href="https://doi.org/10.1007/978-3-031-38271-0_57">10.1007/978-3-031-38271-0_57</a>.
  short: 'C. Offen, S. Ober-Blöbaum, in: F. Nielsen, F. Barbaresco (Eds.), Geometric
    Science of Information, Springer, Cham., 2023, pp. 569–579.'
conference:
  end_date: 2023-09-01
  location: Saint-Malo, Palais du Grand Large, France
  name: '  GSI''23 6th International Conference on Geometric Science of Information'
  start_date: 2023-08-30
date_created: 2023-02-16T11:32:48Z
date_updated: 2024-08-12T13:46:29Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.1007/978-3-031-38271-0_57
editor:
- first_name: F
  full_name: Nielsen, F
  last_name: Nielsen
- first_name: F
  full_name: Barbaresco, F
  last_name: Barbaresco
external_id:
  arxiv:
  - '2302.08232 '
file:
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2023-08-02T12:04:17Z
  date_updated: 2023-08-02T12:04:17Z
  description: |-
    The article shows how to learn models of dynamical systems
    from data which are governed by an unknown variational PDE. Rather
    than employing reduction techniques, we learn a discrete field theory
    governed by a discrete Lagrangian density Ld that is modelled as a neural network. Careful regularisation of the loss function for training Ld is
    necessary to obtain a field theory that is suitable for numerical computations: we derive a regularisation term which optimises the solvability of
    the discrete Euler–Lagrange equations. Secondly, we develop a method to
    find solutions to machine learned discrete field theories which constitute
    travelling waves of the underlying continuous PDE.
  file_id: '46273'
  file_name: LDensityLearning.pdf
  file_size: 1938962
  relation: main_file
  title: Learning discrete Lagrangians for variational PDEs from data and detection
    of travelling waves
file_date_updated: 2023-08-02T12:04:17Z
has_accepted_license: '1'
intvolume: '     14071'
keyword:
- System identification
- discrete Lagrangians
- travelling waves
language:
- iso: eng
oa: '1'
page: 569-579
project:
- _id: '52'
  name: 'PC2: Computing Resources Provided by the Paderborn Center for Parallel Computing'
publication: Geometric Science of Information
publication_identifier:
  eisbn:
  - 978-3-031-38271-0
publication_status: published
publisher: Springer, Cham.
quality_controlled: '1'
related_material:
  link:
  - description: GitHub
    relation: software
    url: https://github.com/Christian-Offen/LagrangianDensityML
series_title: Lecture Notes in Computer Science (LNCS)
status: public
title: Learning discrete Lagrangians for variational PDEs from data and detection
  of travelling waves
type: conference
user_id: '85279'
volume: 14071
year: '2023'
...
---
_id: '29240'
abstract:
- lang: eng
  text: "The principle of least action is one of the most fundamental physical principle.
    It says that among all possible motions connecting two points in a phase space,
    the system will exhibit those motions which extremise an action functional. Many
    qualitative features of dynamical systems, such as the presence of conservation
    laws and energy balance equations, are related to the existence of an action functional.
    Incorporating variational structure into learning algorithms for dynamical systems
    is, therefore, crucial in order to make sure that the learned model shares important
    features with the exact physical system. In this paper we show how to incorporate
    variational principles into trajectory predictions of learned dynamical systems.
    The novelty of this work is that (1) our technique relies only on discrete position
    data of observed trajectories. Velocities or conjugate momenta do not need to
    be observed or approximated and no prior knowledge about the form of the variational
    principle is assumed. Instead, they are recovered using backward error analysis.
    (2) Moreover, our technique compensates discretisation errors when trajectories
    are computed from the learned system. This is important when moderate to large
    step-sizes are used and high accuracy is required. For this,\r\nwe introduce and
    rigorously analyse the concept of inverse modified Lagrangians by developing an
    inverse version of variational backward error analysis. (3) Finally, we introduce
    a method to perform system identification from position observations only, based
    on variational backward error analysis."
article_type: original
author:
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
citation:
  ama: Ober-Blöbaum S, Offen C. Variational Learning of Euler–Lagrange Dynamics from
    Data. <i>Journal of Computational and Applied Mathematics</i>. 2023;421:114780.
    doi:<a href="https://doi.org/10.1016/j.cam.2022.114780">10.1016/j.cam.2022.114780</a>
  apa: Ober-Blöbaum, S., &#38; Offen, C. (2023). Variational Learning of Euler–Lagrange
    Dynamics from Data. <i>Journal of Computational and Applied Mathematics</i>, <i>421</i>,
    114780. <a href="https://doi.org/10.1016/j.cam.2022.114780">https://doi.org/10.1016/j.cam.2022.114780</a>
  bibtex: '@article{Ober-Blöbaum_Offen_2023, title={Variational Learning of Euler–Lagrange
    Dynamics from Data}, volume={421}, DOI={<a href="https://doi.org/10.1016/j.cam.2022.114780">10.1016/j.cam.2022.114780</a>},
    journal={Journal of Computational and Applied Mathematics}, publisher={Elsevier},
    author={Ober-Blöbaum, Sina and Offen, Christian}, year={2023}, pages={114780}
    }'
  chicago: 'Ober-Blöbaum, Sina, and Christian Offen. “Variational Learning of Euler–Lagrange
    Dynamics from Data.” <i>Journal of Computational and Applied Mathematics</i> 421
    (2023): 114780. <a href="https://doi.org/10.1016/j.cam.2022.114780">https://doi.org/10.1016/j.cam.2022.114780</a>.'
  ieee: 'S. Ober-Blöbaum and C. Offen, “Variational Learning of Euler–Lagrange Dynamics
    from Data,” <i>Journal of Computational and Applied Mathematics</i>, vol. 421,
    p. 114780, 2023, doi: <a href="https://doi.org/10.1016/j.cam.2022.114780">10.1016/j.cam.2022.114780</a>.'
  mla: Ober-Blöbaum, Sina, and Christian Offen. “Variational Learning of Euler–Lagrange
    Dynamics from Data.” <i>Journal of Computational and Applied Mathematics</i>,
    vol. 421, Elsevier, 2023, p. 114780, doi:<a href="https://doi.org/10.1016/j.cam.2022.114780">10.1016/j.cam.2022.114780</a>.
  short: S. Ober-Blöbaum, C. Offen, Journal of Computational and Applied Mathematics
    421 (2023) 114780.
date_created: 2022-01-11T13:24:00Z
date_updated: 2023-08-10T08:42:39Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.1016/j.cam.2022.114780
external_id:
  arxiv:
  - '2112.12619'
file:
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2022-06-28T15:25:50Z
  date_updated: 2022-06-28T15:25:50Z
  description: |-
    The principle of least action is one of the most fundamental physical principle. It says that among all possible motions
    connecting two points in a phase space, the system will exhibit those motions which extremise an action functional.
    Many qualitative features of dynamical systems, such as the presence of conservation laws and energy balance equa-
    tions, are related to the existence of an action functional. Incorporating variational structure into learning algorithms
    for dynamical systems is, therefore, crucial in order to make sure that the learned model shares important features
    with the exact physical system. In this paper we show how to incorporate variational principles into trajectory predic-
    tions of learned dynamical systems. The novelty of this work is that (1) our technique relies only on discrete position
    data of observed trajectories. Velocities or conjugate momenta do not need to be observed or approximated and no
    prior knowledge about the form of the variational principle is assumed. Instead, they are recovered using backward
    error analysis. (2) Moreover, our technique compensates discretisation errors when trajectories are computed from the
    learned system. This is important when moderate to large step-sizes are used and high accuracy is required. For this,
    we introduce and rigorously analyse the concept of inverse modified Lagrangians by developing an inverse version of
    variational backward error analysis. (3) Finally, we introduce a method to perform system identification from position
    observations only, based on variational backward error analysis.
  file_id: '32274'
  file_name: ShadowLagrangian_revision1_journal_style_arxiv.pdf
  file_size: 3640770
  relation: main_file
  title: Variational Learning of Euler–Lagrange Dynamics from Data
file_date_updated: 2022-06-28T15:25:50Z
has_accepted_license: '1'
intvolume: '       421'
keyword:
- Lagrangian learning
- variational backward error analysis
- modified Lagrangian
- variational integrators
- physics informed learning
language:
- iso: eng
oa: '1'
page: '114780'
publication: Journal of Computational and Applied Mathematics
publication_identifier:
  issn:
  - 0377-0427
publication_status: epub_ahead
publisher: Elsevier
quality_controlled: '1'
related_material:
  link:
  - relation: software
    url: https://github.com/Christian-Offen/LagrangianShadowIntegration
status: public
title: Variational Learning of Euler–Lagrange Dynamics from Data
type: journal_article
user_id: '85279'
volume: 421
year: '2023'
...
---
_id: '37654'
abstract:
- lang: eng
  text: "Recently, Hamiltonian neural networks (HNN) have been introduced to incorporate
    prior physical knowledge when\r\nlearning the dynamical equations of Hamiltonian
    systems. Hereby, the symplectic system structure is preserved despite\r\nthe data-driven
    modeling approach. However, preserving symmetries requires additional attention.
    In this research, we\r\nenhance the HNN with a Lie algebra framework to detect
    and embed symmetries in the neural network. This approach\r\nallows to simultaneously
    learn the symmetry group action and the total energy of the system. As illustrating
    examples,\r\na pendulum on a cart and a two-body problem from astrodynamics are
    considered."
article_number: '063115'
article_type: original
author:
- first_name: Eva
  full_name: Dierkes, Eva
  last_name: Dierkes
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Kathrin
  full_name: Flaßkamp, Kathrin
  last_name: Flaßkamp
citation:
  ama: Dierkes E, Offen C, Ober-Blöbaum S, Flaßkamp K. Hamiltonian Neural Networks
    with Automatic Symmetry Detection. <i>Chaos</i>. 2023;33(6). doi:<a href="https://doi.org/10.1063/5.0142969">10.1063/5.0142969</a>
  apa: Dierkes, E., Offen, C., Ober-Blöbaum, S., &#38; Flaßkamp, K. (2023). Hamiltonian
    Neural Networks with Automatic Symmetry Detection. <i>Chaos</i>, <i>33</i>(6),
    Article 063115. <a href="https://doi.org/10.1063/5.0142969">https://doi.org/10.1063/5.0142969</a>
  bibtex: '@article{Dierkes_Offen_Ober-Blöbaum_Flaßkamp_2023, title={Hamiltonian Neural
    Networks with Automatic Symmetry Detection}, volume={33}, DOI={<a href="https://doi.org/10.1063/5.0142969">10.1063/5.0142969</a>},
    number={6063115}, journal={Chaos}, publisher={AIP Publishing}, author={Dierkes,
    Eva and Offen, Christian and Ober-Blöbaum, Sina and Flaßkamp, Kathrin}, year={2023}
    }'
  chicago: Dierkes, Eva, Christian Offen, Sina Ober-Blöbaum, and Kathrin Flaßkamp.
    “Hamiltonian Neural Networks with Automatic Symmetry Detection.” <i>Chaos</i>
    33, no. 6 (2023). <a href="https://doi.org/10.1063/5.0142969">https://doi.org/10.1063/5.0142969</a>.
  ieee: 'E. Dierkes, C. Offen, S. Ober-Blöbaum, and K. Flaßkamp, “Hamiltonian Neural
    Networks with Automatic Symmetry Detection,” <i>Chaos</i>, vol. 33, no. 6, Art.
    no. 063115, 2023, doi: <a href="https://doi.org/10.1063/5.0142969">10.1063/5.0142969</a>.'
  mla: Dierkes, Eva, et al. “Hamiltonian Neural Networks with Automatic Symmetry Detection.”
    <i>Chaos</i>, vol. 33, no. 6, 063115, AIP Publishing, 2023, doi:<a href="https://doi.org/10.1063/5.0142969">10.1063/5.0142969</a>.
  short: E. Dierkes, C. Offen, S. Ober-Blöbaum, K. Flaßkamp, Chaos 33 (2023).
date_created: 2023-01-20T09:10:06Z
date_updated: 2023-08-10T08:37:01Z
ddc:
- '510'
department:
- _id: '636'
doi: 10.1063/5.0142969
external_id:
  arxiv:
  - '2301.07928'
file:
- access_level: open_access
  content_type: application/pdf
  creator: coffen
  date_created: 2023-04-26T16:20:56Z
  date_updated: 2023-04-26T16:20:56Z
  description: |-
    Incorporating physical system knowledge into data-driven
    system identification has been shown to be beneficial. The
    approach presented in this article combines learning of an
    energy-conserving model from data with detecting a Lie
    group representation of the unknown system symmetry.
    The proposed approach can improve the learned model
    and reveal underlying symmetry simultaneously.
  file_id: '44205'
  file_name: JournalPaper_main.pdf
  file_size: 5200111
  relation: main_file
  title: Hamiltonian Neural Networks with Automatic Symmetry Detection
file_date_updated: 2023-04-26T16:20:56Z
has_accepted_license: '1'
intvolume: '        33'
issue: '6'
language:
- iso: eng
oa: '1'
publication: Chaos
publication_identifier:
  issn:
  - 1054-1500
publication_status: published
publisher: AIP Publishing
related_material:
  link:
  - description: GitHub
    relation: software
    url: https://github.com/eva-dierkes/HNN_withSymmetries
status: public
title: Hamiltonian Neural Networks with Automatic Symmetry Detection
type: journal_article
user_id: '85279'
volume: 33
year: '2023'
...
---
_id: '21600'
abstract:
- lang: eng
  text: Many problems in science and engineering require an efficient numerical approximation
    of integrals or solutions to differential equations. For systems with rapidly
    changing dynamics, an equidistant discretization is often inadvisable as it results
    in prohibitively large errors or computational effort. To this end, adaptive schemes,
    such as solvers based on Runge–Kutta pairs, have been developed which adapt the
    step size based on local error estimations at each step. While the classical schemes
    apply very generally and are highly efficient on regular systems, they can behave
    suboptimally when an inefficient step rejection mechanism is triggered by structurally
    complex systems such as chaotic systems. To overcome these issues, we propose
    a method to tailor numerical schemes to the problem class at hand. This is achieved
    by combining simple, classical quadrature rules or ODE solvers with data-driven
    time-stepping controllers. Compared with learning solution operators to ODEs directly,
    it generalizes better to unseen initial data as our approach employs classical
    numerical schemes as base methods. At the same time it can make use of identified
    structures of a problem class and, therefore, outperforms state-of-the-art adaptive
    schemes. Several examples demonstrate superior efficiency. Source code is available
    at https://github.com/lueckem/quadrature-ML.
author:
- first_name: Michael
  full_name: Dellnitz, Michael
  last_name: Dellnitz
- first_name: Eyke
  full_name: Hüllermeier, Eyke
  id: '48129'
  last_name: Hüllermeier
- first_name: Marvin
  full_name: Lücke, Marvin
  last_name: Lücke
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Christian
  full_name: Offen, Christian
  id: '85279'
  last_name: Offen
  orcid: 0000-0002-5940-8057
- first_name: Sebastian
  full_name: Peitz, Sebastian
  id: '47427'
  last_name: Peitz
  orcid: 0000-0002-3389-793X
- first_name: Karlson
  full_name: Pfannschmidt, Karlson
  id: '13472'
  last_name: Pfannschmidt
  orcid: 0000-0001-9407-7903
citation:
  ama: Dellnitz M, Hüllermeier E, Lücke M, et al. Efficient time stepping for numerical
    integration using reinforcement  learning. <i>SIAM Journal on Scientific Computing</i>.
    2023;45(2):A579-A595. doi:<a href="https://doi.org/10.1137/21M1412682">10.1137/21M1412682</a>
  apa: Dellnitz, M., Hüllermeier, E., Lücke, M., Ober-Blöbaum, S., Offen, C., Peitz,
    S., &#38; Pfannschmidt, K. (2023). Efficient time stepping for numerical integration
    using reinforcement  learning. <i>SIAM Journal on Scientific Computing</i>, <i>45</i>(2),
    A579–A595. <a href="https://doi.org/10.1137/21M1412682">https://doi.org/10.1137/21M1412682</a>
  bibtex: '@article{Dellnitz_Hüllermeier_Lücke_Ober-Blöbaum_Offen_Peitz_Pfannschmidt_2023,
    title={Efficient time stepping for numerical integration using reinforcement 
    learning}, volume={45}, DOI={<a href="https://doi.org/10.1137/21M1412682">10.1137/21M1412682</a>},
    number={2}, journal={SIAM Journal on Scientific Computing}, author={Dellnitz,
    Michael and Hüllermeier, Eyke and Lücke, Marvin and Ober-Blöbaum, Sina and Offen,
    Christian and Peitz, Sebastian and Pfannschmidt, Karlson}, year={2023}, pages={A579–A595}
    }'
  chicago: 'Dellnitz, Michael, Eyke Hüllermeier, Marvin Lücke, Sina Ober-Blöbaum,
    Christian Offen, Sebastian Peitz, and Karlson Pfannschmidt. “Efficient Time Stepping
    for Numerical Integration Using Reinforcement  Learning.” <i>SIAM Journal on Scientific
    Computing</i> 45, no. 2 (2023): A579–95. <a href="https://doi.org/10.1137/21M1412682">https://doi.org/10.1137/21M1412682</a>.'
  ieee: 'M. Dellnitz <i>et al.</i>, “Efficient time stepping for numerical integration
    using reinforcement  learning,” <i>SIAM Journal on Scientific Computing</i>, vol.
    45, no. 2, pp. A579–A595, 2023, doi: <a href="https://doi.org/10.1137/21M1412682">10.1137/21M1412682</a>.'
  mla: Dellnitz, Michael, et al. “Efficient Time Stepping for Numerical Integration
    Using Reinforcement  Learning.” <i>SIAM Journal on Scientific Computing</i>, vol.
    45, no. 2, 2023, pp. A579–95, doi:<a href="https://doi.org/10.1137/21M1412682">10.1137/21M1412682</a>.
  short: M. Dellnitz, E. Hüllermeier, M. Lücke, S. Ober-Blöbaum, C. Offen, S. Peitz,
    K. Pfannschmidt, SIAM Journal on Scientific Computing 45 (2023) A579–A595.
date_created: 2021-04-09T07:59:19Z
date_updated: 2023-08-25T09:24:50Z
ddc:
- '510'
department:
- _id: '101'
- _id: '636'
- _id: '355'
- _id: '655'
doi: 10.1137/21M1412682
external_id:
  arxiv:
  - arXiv:2104.03562
has_accepted_license: '1'
intvolume: '        45'
issue: '2'
language:
- iso: eng
main_file_link:
- url: https://epubs.siam.org/doi/reader/10.1137/21M1412682
page: A579-A595
publication: SIAM Journal on Scientific Computing
publication_status: published
related_material:
  link:
  - description: GitHub
    relation: software
    url: https://github.com/lueckem/quadrature-ML
status: public
title: Efficient time stepping for numerical integration using reinforcement  learning
type: journal_article
user_id: '47427'
volume: 45
year: '2023'
...
---
_id: '47147'
alternative_title:
- GAMM Rundbriefe
author:
- first_name: Yana
  full_name: Lishkova, Yana
  last_name: Lishkova
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
- first_name: Sigrid
  full_name: Leyendecker, Sigrid
  last_name: Leyendecker
citation:
  ama: Lishkova Y, Ober-Blöbaum S, Leyendecker S. <i>Multirate Discrete Mechanics
    and Optimal Control for a Flexible Satelite Model </i>. Invited Mathematical Magazine
    Article; 2023.
  apa: Lishkova, Y., Ober-Blöbaum, S., &#38; Leyendecker, S. (2023). <i>Multirate
    Discrete Mechanics and Optimal Control for a Flexible Satelite Model </i>. Invited
    Mathematical Magazine Article.
  bibtex: '@book{Lishkova_Ober-Blöbaum_Leyendecker_2023, title={Multirate Discrete
    Mechanics and Optimal Control for a Flexible Satelite Model }, publisher={Invited
    Mathematical Magazine Article}, author={Lishkova, Yana and Ober-Blöbaum, Sina
    and Leyendecker, Sigrid}, year={2023} }'
  chicago: Lishkova, Yana, Sina Ober-Blöbaum, and Sigrid Leyendecker. <i>Multirate
    Discrete Mechanics and Optimal Control for a Flexible Satelite Model </i>. Invited
    Mathematical Magazine Article, 2023.
  ieee: Y. Lishkova, S. Ober-Blöbaum, and S. Leyendecker, <i>Multirate Discrete Mechanics
    and Optimal Control for a Flexible Satelite Model </i>. Invited Mathematical Magazine
    Article, 2023.
  mla: Lishkova, Yana, et al. <i>Multirate Discrete Mechanics and Optimal Control
    for a Flexible Satelite Model </i>. Invited Mathematical Magazine Article, 2023.
  short: Y. Lishkova, S. Ober-Blöbaum, S. Leyendecker, Multirate Discrete Mechanics
    and Optimal Control for a Flexible Satelite Model , Invited Mathematical Magazine
    Article, 2023.
date_created: 2023-09-21T07:20:43Z
date_updated: 2023-09-21T07:27:15Z
language:
- iso: eng
publisher: Invited Mathematical Magazine Article
status: public
title: 'Multirate Discrete Mechanics and Optimal Control for a Flexible Satelite Model '
type: report
user_id: '15694'
year: '2023'
...
---
_id: '47148'
author:
- first_name: Y.
  full_name: Lishkova, Y.
  last_name: Lishkova
- first_name: M.
  full_name: Bando, M.
  last_name: Bando
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
citation:
  ama: 'Lishkova Y, Bando M, Ober-Blöbaum S. Variational approach for modelling and
    optimal control of electrodynamic tether motion. In: Accepted for the 74th International
    Astronautical Concress (IAC); 2023.'
  apa: Lishkova, Y., Bando, M., &#38; Ober-Blöbaum, S. (2023). <i>Variational approach
    for modelling and optimal control of electrodynamic tether motion</i>.
  bibtex: '@inproceedings{Lishkova_Bando_Ober-Blöbaum_2023, title={Variational approach
    for modelling and optimal control of electrodynamic tether motion}, publisher={Accepted
    for the 74th International Astronautical Concress (IAC)}, author={Lishkova, Y.
    and Bando, M. and Ober-Blöbaum, Sina}, year={2023} }'
  chicago: Lishkova, Y., M. Bando, and Sina Ober-Blöbaum. “Variational Approach for
    Modelling and Optimal Control of Electrodynamic Tether Motion.” Accepted for the
    74th International Astronautical Concress (IAC), 2023.
  ieee: Y. Lishkova, M. Bando, and S. Ober-Blöbaum, “Variational approach for modelling
    and optimal control of electrodynamic tether motion,” 2023.
  mla: Lishkova, Y., et al. <i>Variational Approach for Modelling and Optimal Control
    of Electrodynamic Tether Motion</i>. Accepted for the 74th International Astronautical
    Concress (IAC), 2023.
  short: 'Y. Lishkova, M. Bando, S. Ober-Blöbaum, in: Accepted for the 74th International
    Astronautical Concress (IAC), 2023.'
date_created: 2023-09-21T07:25:40Z
date_updated: 2023-09-21T07:27:21Z
language:
- iso: eng
publisher: Accepted for the 74th International Astronautical Concress (IAC)
status: public
title: Variational approach for modelling and optimal control of electrodynamic tether
  motion
type: conference
user_id: '15694'
year: '2023'
...
---
_id: '30490'
author:
- first_name: Jacky
  full_name: Cresson, Jacky
  last_name: Cresson
- first_name: Fernando
  full_name: Jiménez, Fernando
  last_name: Jiménez
- first_name: Sina
  full_name: Ober-Blöbaum, Sina
  id: '16494'
  last_name: Ober-Blöbaum
citation:
  ama: Cresson J, Jiménez F, Ober-Blöbaum S. Continuous and discrete Noether’s fractional
    conserved quantities for restricted calculus of variations. <i>AIMS</i>. 2022;14(1):57-89.
  apa: Cresson, J., Jiménez, F., &#38; Ober-Blöbaum, S. (2022). Continuous and discrete
    Noether’s fractional conserved quantities for restricted calculus of variations.
    <i>AIMS</i>, <i>14(1)</i>, 57–89.
  bibtex: '@article{Cresson_Jiménez_Ober-Blöbaum_2022, title={Continuous and discrete
    Noether’s fractional conserved quantities for restricted calculus of variations},
    volume={14(1)}, journal={AIMS}, author={Cresson, Jacky and Jiménez, Fernando and
    Ober-Blöbaum, Sina}, year={2022}, pages={57–89} }'
  chicago: 'Cresson, Jacky, Fernando Jiménez, and Sina Ober-Blöbaum. “Continuous and
    Discrete Noether’s Fractional Conserved Quantities for Restricted Calculus of
    Variations.” <i>AIMS</i> 14(1) (2022): 57–89.'
  ieee: J. Cresson, F. Jiménez, and S. Ober-Blöbaum, “Continuous and discrete Noether’s
    fractional conserved quantities for restricted calculus of variations,” <i>AIMS</i>,
    vol. 14(1), pp. 57–89, 2022.
  mla: Cresson, Jacky, et al. “Continuous and Discrete Noether’s Fractional Conserved
    Quantities for Restricted Calculus of Variations.” <i>AIMS</i>, vol. 14(1), 2022,
    pp. 57–89.
  short: J. Cresson, F. Jiménez, S. Ober-Blöbaum, AIMS 14(1) (2022) 57–89.
date_created: 2022-03-24T12:26:10Z
date_updated: 2022-03-24T12:26:32Z
department:
- _id: '636'
language:
- iso: eng
page: 57-89
publication: AIMS
status: public
title: Continuous and discrete Noether's fractional conserved quantities for restricted
  calculus of variations
type: journal_article
user_id: '15694'
volume: 14(1)
year: '2022'
...
