TY - GEN A1 - Zonker, Johannes A1 - Padilla-Iglesias, Cecilia A1 - Djurdjevac Conrad, Natasa T1 - Supplementary code and data for Royal Society Open Science Manuscript rsos.230495 N2 - In this repository are all files necessary to run the agent-based model of the paper "Insights into drivers of mobility and cultural dynamics of African hunter–gatherers over the past 120 000 years", Royal Society Open Science, 10(11), 2023. Y1 - 2023 U6 - https://doi.org/10.12752/9254 ER - TY - GEN A1 - Helfmann, Luzie A1 - Djurdjevac Conrad, Natasa A1 - Lorenz-Spreen, Philipp A1 - Schütte, Christof T1 - Supplementary code for the paper Modelling opinion dynamics under the impact of influencer and media strategies N2 - This repository contains the Julia code accompanying the paper "Modelling opinion dynamics under the impact of influencer and media strategies", Scientific Reports, Vol.13, p. 19375, 2023. Y1 - 2023 U6 - https://doi.org/10.12752/9267 ER - TY - THES A1 - Binkowski, Felix T1 - Riesz-projection-based methods for the numerical simulation of resonance phenomena in nanophotonics Y1 - 2023 U6 - https://doi.org/10.17169/refubium-41230 ER - TY - JOUR A1 - Oehme, Stephan A1 - Moewis, Philippe A1 - Boeth, Heide A1 - Bartek, Benjamin A1 - von Tycowicz, Christoph A1 - Ehrig, Rainald A1 - Duda, Georg A1 - Jung, Tobias T1 - Altered knee kinematics after posterior cruciate single-bundle reconstruction - a comprehensive prospective biomechanical in vivo analysis JF - Frontiers in Bioengineering and Biotechnology Y1 - 2024 U6 - https://doi.org/10.3389/fbioe.2024.1322136 VL - 12 ER - TY - JOUR A1 - Ernst, Ariane A1 - Falkenhagen, Undine A1 - Winkelmann, Stefanie T1 - Model reduction for calcium-induced vesicle fusion dynamics JF - Proceedings in Applied Mathematics & Mechanics N2 - In this work, we adapt an established model for the Ca2+-induced fusion dynamics of synaptic vesicles and employ a lumping method to reduce its complexity. In the reduced system, sequential Ca2+-binding steps are merged to a single releasable state, while keeping the important dependence of the reaction rates on the local Ca2+ concentration. We examine the feasibility of this model reduction for a representative stimulus train over the physiologically relevant site-channel distances. Our findings show that the approximation error is generally small and exhibits an interesting nonlinear and non-monotonic behavior where it vanishes for very low distances and is insignificant at intermediary distances. Furthermore, we give expressions for the reduced model’s reaction rates and suggest that our approach may be used to directly compute effective fusion rates for assessing the validity of a fusion model, thereby circumventing expensive simulations. Y1 - 2023 U6 - https://doi.org/10.1002/pamm.202300184 VL - 23 IS - 4 ER - TY - GEN A1 - Colom, Rémi A1 - Mikheeva, Elena A1 - Achouri, Karim A1 - Zuniga-Perez, Jesus A1 - Bonod, Nicolas A1 - Martin, Olivier J.F. A1 - Burger, Sven A1 - Genevet, Patrice T1 - Crossing of the Branch Cut: The Topological Origin of a Universal 2π-Phase Retardation in Non-Hermitian Metasurfaces (Laser Photonics Rev. 17(6)/2023) T2 - Laser Photonics Rev. Y1 - 2023 U6 - https://doi.org/10.1002/lpor.202370029 VL - 17 SP - 2370029 ER - TY - GEN A1 - Weiser, Martin A1 - Hubig, Michael A1 - Shanmugam Subramaniam, Jayant T1 - Reconstructing Ambient Temperature Changes in Death Time Estimation with a Bayesian Double-Exponential Approach T2 - Zenodo N2 - Code and data for the reconstruction of ambient temperature drop in time of death estimation We provide Octave code and temperature measurement data for - empirircally estimating thermal sensor likelihood - estimating time and amplitude of a single sudden ambient temperature drop from temperature measurement data in two thermally different compartments. Y1 - 2025 U6 - https://doi.org/10.5281/zenodo.17702240 ER - TY - JOUR A1 - Sekulic, Ivan A1 - Schaible, Jonas A1 - Müller, Gabriel A1 - Plock, Matthias A1 - Burger, Sven A1 - Martínez-Lahuerta, Víctor José A1 - Gaaloul, Naceur A1 - Schneider, Philipp-Immanuel T1 - Physics-informed Bayesian optimization of expensive-to-evaluate black-box functions JF - Mach. Learn. Sci. Technol. N2 - Abstract Bayesian optimization with Gaussian process surrogates is a popular approach for optimizing expensive-to-evaluate functions in terms of time, energy, or computational resources. Typically, a Gaussian process models a scalar objective derived from observed data. However, in many real-world applications, the objective is a combination of multiple outputs from physical experiments or simulations. Converting these multidimensional observations into a single scalar can lead to information loss, slowing convergence and yielding suboptimal results. To address this, we propose to use multi-output Gaussian processes to learn the full vector of observations directly, before mapping them to the scalar objective via an inexpensive analytical function. This physics-informed approach retains more information from the underlying physical processes, improving surrogate model accuracy. As a result, the approach accelerates optimization and produces better final designs compared to standard implementations. Y1 - 2025 U6 - https://doi.org/10.1088/2632-2153/ae1f5f VL - 6 SP - 040503 PB - IOP Publishing ER - TY - CHAP A1 - Zschiedrich, Lin A1 - Betz, Fridtjof A1 - Binkowski, Felix A1 - Kuen, Lilli A1 - Hammerschmidt, Martin A1 - Burger, Sven T1 - Efficient Photonic Component Analysis via AAA Rational Approximation T2 - 2025 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) Y1 - 2025 U6 - https://doi.org/10.1109/NUSOD64393.2025.11199710 SP - 115 EP - 116 ER - TY - THES A1 - Plock, Matthias T1 - On Methods for Bayesian Optimization of Least Squares Problems and Optimization of Nanophotonic Devices Y1 - 2025 U6 - https://doi.org/10.17169/refubium-48179 ER - TY - GEN A1 - Sekulic, Ivan A1 - Schaible, Jonas A1 - Müller, Gabriel A1 - Plock, Matthias A1 - Burger, Sven A1 - Martinez-Lahuerta, Victor J. A1 - Gaaloul, Naceur A1 - Schneider, Philipp-Immanuel T1 - Data publication for Physics-informed Bayesian optimization of expensive-to-evaluate black-box functions T2 - Zenodo Y1 - 2025 U6 - https://doi.org/10.5281/zenodo.16751507 ER - TY - GEN A1 - Betz, Fridtjof A1 - Binkowski, Felix A1 - Fischbach, Jan David A1 - Feldman, Nick A1 - Zschiedrich, Lin A1 - Rockstuhl, Carsten A1 - Koenderink, A. Femius A1 - Burger, Sven T1 - Uncovering Hidden Resonances in Non-Hermitian Systems with Scattering Thresholds (Laser Photonics Rev. 19(21)/2025) T2 - Laser Photonics Rev. Y1 - 2025 U6 - https://doi.org/10.1002/lpor.70534 VL - 19 IS - 21 SP - e70534 ER - TY - JOUR A1 - Abou Hamdan, Loubnan A1 - Jana, Aloke A1 - Colom, Rémi A1 - Aboujoussef, Nour A1 - Carlson, Cooper A1 - Overvig, Adam A1 - Binkowski, Felix A1 - Burger, Sven A1 - Genevet, Patrice T1 - A Complex-Frequency Framework for Kerker Unidirectionality in Photonic Resonators Y1 - 2026 U6 - https://doi.org/10.21203/rs.3.rs-8444305/v1 ER - TY - JOUR A1 - Trower, Maia A1 - Djurdjevac Conrad, Natasa A1 - Klus, Stefan T1 - Clustering Time-Evolving Networks Using the Spatiotemporal Graph Laplacian JF - Chaos: An Interdisciplinary Journal of Nonlinear Science N2 - Time-evolving graphs arise frequently when modeling complex dynamical systems such as social networks, traffic flow, and biological processes. Developing techniques to identify and analyze communities in these time-varying graph structures is an important challenge. In this work, we generalize existing spectral clustering algorithms from static to dynamic graphs using canonical correlation analysis (CCA) to capture the temporal evolution of clusters. Based on this extended canonical correlation framework, we define the spatio-temporal graph Laplacian and investigate its spectral properties. We connect these concepts to dynamical systems theory via transfer operators, and illustrate the advantages of our method on benchmark graphs by comparison with existing methods. We show that the spatio-temporal graph Laplacian allows for a clear interpretation of cluster structure evolution over time for directed and undirected graphs. Y1 - 2025 U6 - https://doi.org/10.1063/5.0228419 VL - 35 SP - 013126 ER - TY - JOUR A1 - Straube, Arthur A1 - Höfling, Felix T1 - Memory effects in colloidal motion under confinement and driving JF - J. Phys. A: Math. Theor. N2 - The transport of individual particles in inhomogeneous environments is complex and exhibits non-Markovian responses. The latter may be quantified by a memory function within the framework of the linear generalised Langevin equation (GLE). Here, we exemplify the implications of steady driving on the memory function of a colloidal model system for Brownian motion in a corrugated potential landscape, specifically, for one-dimensional motion in a sinusoidal potential. To this end, we consider the overdamped limit of the GLE, which is facilitated by separating the memory function into a singular (Markovian) and a regular (non-Markovian) part. Relying on exact solutions for the investigated model, we show that the random force entering the GLE must display a bias far from equilibrium, which corroborates a recent general prediction. Based on data for the mean-square displacement (MSD) obtained from Brownian dynamics simulations, we estimate the memory function for different driving strengths and show that already moderate driving accelerates the decay of the memory function by several orders of magnitude in time. We find that the memory may persist on much longer timescales than expected from the convergence of the MSD to its long-time asymptote. Furthermore, the functional form of the memory function changes from a monotonic decay to a non-monotonic, damped oscillatory behaviour, which can be understood from a competition of confined motion and depinning. Our analysis of the simulation data further reveals a pronounced non-Gaussianity, which questions the Gaussian approximation of the random force entering the GLE. Y1 - 2024 U6 - https://doi.org/10.1088/1751-8121/ad5b2d SN - 1751-8113 VL - 57 SP - 295003 PB - IOP Publishing ER - TY - JOUR A1 - Boniface, Dolachai A1 - Straube, Arthur A1 - Tierno, Pietro T1 - Photocatalytic magnetic microgyroscopes with activity-tunable precessional dynamics JF - Nano Letters N2 - Magnetic nano/microrotors are passive elements that spin around an axis due to an external rotating field while remaining confined to a close plane. They have been used to date in different applications related to fluid mixing, drug delivery or biomedicine. Here we realize an active version of a magnetic microgyroscope which is simultaneously driven by a photo-activated catalytic reaction and a rotating magnetic field. We investigate the uplift dynamics of this colloidal spinner when it stands up and precesses around its long axis while self-propelling due to the light induced decomposition of hydrogen peroxide in water. By combining experiments with theory, we show that activity emerging from the cooperative action of phoretic and osmotic forces effectively increase the gravitational torque which counteracts the magnetic and viscous ones, and carefully measure its contribution. Y1 - 2024 U6 - https://doi.org/10.1021/acs.nanolett.4c03386 VL - 24 IS - 47 SP - 14950 EP - 14956 ER - TY - GEN A1 - Villani, Paolo A1 - Weiser, Martin T1 - Adaptive Gaussian process regression for inverse problems. ALGORITMY 2024 N2 - This submission contains the code used for the proceedings paper for ALGORITMY 2024, concerning surrogate model-based inverse problems. Version 2 modified plot appearances and fixed some minor typos. Y1 - 2024 ER - TY - JOUR A1 - Ernst, Marco A1 - Asselineau, Charles-Alexis A1 - Tillmann, Peter A1 - Jäger, Klaus A1 - Becker, Christiane T1 - Modelling bifacial irradiance – Step-by-step comparison and validation of view factor and ray tracing models JF - Appl. Energy Y1 - 2024 U6 - https://doi.org/10.1016/j.apenergy.2024.123574 SN - 0306-2619 VL - 369 SP - 123574 PB - Elsevier BV ER - TY - GEN A1 - Sekulic, Ivan A1 - Schneider, Philipp-Immanuel A1 - Hammerschmidt, Martin A1 - Burger, Sven T1 - Machine-learning driven design of metasurfaces: learn the physics and not the objective function T2 - Proc. SPIE Y1 - 2024 U6 - https://doi.org/10.1117/12.3022119 VL - PC13017 SP - PC130170X ER - TY - GEN A1 - Bopp, Julian M. A1 - Plock, Matthias A1 - Turan, Tim A1 - Pieplow, Gregor A1 - Burger, Sven A1 - Schröder, Tim T1 - ‘Sawfish’ Photonic Crystal Cavity for Near-Unity Emitter-to-Fiber Interfacing in Quantum Network Applications (Advanced Optical Materials 13/2024) T2 - Adv. Optical Mater. Y1 - 2024 U6 - https://doi.org/10.1002/adom.202470046 VL - 12 SP - 2470046 ER - TY - JOUR A1 - Klus, Stefan A1 - Djurdjevac Conrad, Natasa T1 - Dynamical systems and complex networks: A Koopman operator perspective JF - Journal of Physics: Complexity N2 - The Koopman operator has entered and transformed many research areas over the last years. Although the underlying concept–representing highly nonlinear dynamical systems by infinite-dimensional linear operators–has been known for a long time, the availability of large data sets and efficient machine learning algorithms for estimating the Koopman operator from data make this framework extremely powerful and popular. Koopman operator theory allows us to gain insights into the characteristic global properties of a system without requiring detailed mathematical models. We will show how these methods can also be used to analyze complex networks and highlight relationships between Koopman operators and graph Laplacians. Y1 - 2024 U6 - https://doi.org/10.1088/2632-072X/ad9e60 VL - 5 IS - 4 SP - 041001 PB - IOP Publishing ER - TY - JOUR A1 - Krüger, Jan A1 - Manley, Phillip A1 - Bergmann, Detlef A1 - Köning, Rainer A1 - Bodermann, Bernd A1 - Eder, Christian A1 - Heinrich, Andreas A1 - Schneider, Philipp-Immanuel A1 - Hammerschmidt, Martin A1 - Zschiedrich, Lin A1 - Manske, Eberhard T1 - Introduction and application of a new approach for model-based optical bidirectional measurements JF - Meas. Sci. Technol. Y1 - 2024 U6 - https://doi.org/10.1088/1361-6501/ad4b53 VL - 35 SP - 085014 ER - TY - JOUR A1 - Manley, Phillip A1 - Hammerschmidt, Martin A1 - Zschiedrich, Lin A1 - Jäger, Klaus A1 - Becker, Christiane A1 - Burger, Sven T1 - Modelling luminescent coupling in multi-junction solar cells: perovskite silicon tandem case study JF - Proc. SPIE Y1 - 2024 U6 - https://doi.org/10.1117/12.3023941 VL - 13014 SP - 1301404 ER - TY - CHAP A1 - Schaible, Jonas A1 - Yoo, Danbi A1 - Winarto, Hanifa A1 - Miaskiewicz, Alexandra A1 - Albrecht, Steve A1 - Wessels, Andreas A1 - Bläsi, Benedikt A1 - Burger, Sven A1 - Jaeger, Klaus A1 - Becker, Christiane T1 - On aesthetical appearance of colored perovskite solar modules T2 - Proc. SPIE Y1 - 2024 U6 - https://doi.org/10.1117/12.3017427 VL - PC13014 SP - PC1301406 PB - SPIE ER - TY - CHAP A1 - Becker, Christiane A1 - Bläsi, Benedikt A1 - Burger, Sven A1 - Ehrler, Bruno A1 - Gordon, Ivan A1 - Isabella, Olindo A1 - Jäger, Klaus A1 - Jost, Marko A1 - Manley, Phillip A1 - Muñoz, Delfina A1 - Paetzold, Ulrich W. A1 - Sai, Hitoshi A1 - Yablonovitch, Eli T1 - Optical challenges for terawatt-scale photovoltaics T2 - Proc. SPIE Y1 - 2024 U6 - https://doi.org/10.1117/12.3016415 VL - PC13014 SP - PC1301401 PB - SPIE ER - TY - CHAP A1 - Semler, Phillip A1 - Weiser, Martin ED - Fackeldey, Konstantin ED - Kannan, Aswin ED - Pokutta, Sebastian ED - Sharma, Kartikey ED - Walter, Daniel ED - Walther, Andrea ED - Weiser, Martin T1 - Adaptive gradient-enhanced Gaussian process surrogates for inverse problems T2 - Mathematical Optimization for Machine Learning: Proceedings of the MATH+ Thematic Einstein Semester 2023 N2 - Generating simulated training data needed for constructing sufficiently accurate surrogate models to be used for efficient optimization or parameter identification can incur a huge computational effort in the offline phase. We consider a fully adaptive greedy approach to the computational design of experiments problem using gradient-enhanced Gaussian process regression as surrogates. Designs are incrementally defined by solving an optimization problem for accuracy given a certain computational budget. We address not only the choice of evaluation points but also of required simulation accuracy, both of values and gradients of the forward model. Numerical results show a significant reduction of the computational effort compared to just position-adaptive and static designs as well as a clear benefit of including gradient information into the surrogate training. Y1 - 2025 U6 - https://doi.org/10.1515/9783111376776-005 SP - 59 EP - 78 PB - De Gruyter ER - TY - JOUR A1 - Djurdjevac Conrad, Natasa A1 - Quang Vu, Nhu A1 - Nagel, Soeren T1 - Co-evolving networks for opinion and social dynamics in agent-based models JF - Chaos: An Interdisciplinary Journal of Nonlinear Science N2 - The rise of digital social media has strengthened the coevolution of public opinions and social interactions, that shape social structures and collective outcomes in increasingly complex ways. Existing literature often explores this interplay as a one-directional influence, focusing on how opinions determine social ties within adaptive networks. However, this perspective overlooks the intrinsic dynamics driving social interactions, which can significantly influence how opinions form and evolve. In this work, we address this gap, by introducing the co-evolving opinion and social dynamics using stochastic agent-based models. Agents' mobility in a social space is governed by both their social and opinion similarity with others. Similarly, the dynamics of opinion formation is driven by the opinions of agents in their social vicinity. We analyze the underlying social and opinion interaction networks and explore the mechanisms influencing the appearance of emerging phenomena, like echo chambers and opinion consensus. To illustrate the model's potential for real-world analysis, we apply it to General Social Survey data on political identity and public opinion regarding governmental issues. Our findings highlight the model's strength in capturing the coevolution of social connections and individual opinions over time. Y1 - 2024 U6 - https://doi.org/10.1063/5.0226054 SN - 1054-1500 VL - 34 IS - 9 ER - TY - GEN A1 - Kuen, Lilli A1 - Löffler, Lorenz A1 - Tsarapkin, Aleksei A1 - Zschiedrich, Lin A1 - Feichtner, Thorsten A1 - Burger, Sven A1 - Höflich, Katja T1 - Source Code and Simulation Results: Chiral and directional optical emission from a dipole source coupled to a helical plasmonic antenna T2 - Zenodo Y1 - 2024 U6 - https://doi.org/10.5281/zenodo.10598255 SP - doi: 10.5281/zenodo.10598255 ER - TY - JOUR A1 - Müller, Gabriel A1 - Martínez-Lahuerta, Victor J. A1 - Sekulic, Ivan A1 - Burger, Sven A1 - Schneider, Philipp-Immanuel A1 - Gaaloul, Naceur T1 - Bayesian optimization for state engineering of quantum gases JF - Quantum Sci. Technol. Y1 - 2025 U6 - https://doi.org/10.1088/2058-9565/ad9050 VL - 10 SP - 015033 ER - TY - JOUR A1 - Erban, Radek A1 - Winkelmann, Stefanie T1 - Multi-grid reaction-diffusion master equation: applications to morphogen gradient modelling JF - Bulletin of Mathematical Biology N2 - The multi-grid reaction-diffusion master equation (mgRDME) provides a generalization of stochastic compartment-based reaction-diffusion modelling described by the standard reaction-diffusion master equation (RDME). By enabling different resolutions on lattices for biochemical species with different diffusion constants, the mgRDME approach improves both accuracy and efficiency of compartment-based reaction-diffusion simulations. The mgRDME framework is examined through its application to morphogen gradient formation in stochastic reaction-diffusion scenarios, using both an analytically tractable first-order reaction network and a model with a second-order reaction. The results obtained by the mgRDME modelling are compared with the standard RDME model and with the (more detailed) particle-based Brownian dynamics simulations. The dependence of error and numerical cost on the compartment sizes is defined and investigated through a multi-objective optimization problem. Y1 - 2025 U6 - https://doi.org/10.1007/s11538-024-01377-y VL - 87 SP - 6 ER - TY - CHAP A1 - Villani, Paolo A1 - Unger, Jörg F. A1 - Weiser, Martin T1 - Adaptive Gaussian Process Regression for Bayesian inverse problems T2 - Proceedings of the Conference Algoritmy 2024 N2 - We introduce a novel adaptive Gaussian Process Regression (GPR) methodology for efficient construction of surrogate models for Bayesian inverse problems with expensive forward model evaluations. An adaptive design strategy focuses on optimizing both the positioning and simulation accuracy of training data in order to reduce the computational cost of simulating training data without compromising the fidelity of the posterior distributions of parameters. The method interleaves a goal-oriented active learning algorithm selecting evaluation points and tolerances based on the expected impact on the Kullback-Leibler divergence of surrogated and true posterior with a Markov Chain Monte Carlo sampling of the posterior. The performance benefit of the adaptive approach is demonstrated for two simple test problems. Y1 - 2024 SP - 214 EP - 224 ER - TY - JOUR A1 - Andrés Arcones, Daniel A1 - Weiser, Martin A1 - Koutsourelakis, Faidon-Stelios A1 - Unger, Jörg F. T1 - A Bayesian Framework for Simulation-based Digital Twins of Bridges JF - EUROSTRUCT 2023:European Association on Quality Control of Bridges and Structures: Digital Transformation in Sustainability N2 - Simulation-based digital twins have emerged as a powerful tool for evaluating the mechanical response of bridges. As virtual representations of physical systems, digital twins can provide a wealth of information that complements traditional inspection and monitoring data. By incorporating virtual sensors and predictive maintenance strategies, they have the potential to improve our understanding of the behavior and performance of bridges over time. However, as bridges age and undergo regular loading and extreme events, their structural characteristics change, often differing from the predictions of their initial design. Digital twins must be continuously adapted to reflect these changes. In this article, we present a Bayesian framework for updating simulation-based digital twins in the context of bridges. Our approach integrates information from measurements to account for inaccuracies in the simulation model and quantify uncertainties. Through its implementation and assessment, this work demonstrates the potential for digital twins to provide a reliable and up-to-date representation of bridge behavior, helping to inform decision-making for maintenance and management. Y1 - 2023 U6 - https://doi.org/10.1002/cepa.2177 VL - 6 IS - 5 SP - 734 EP - 740 ER - TY - CHAP A1 - Andrés Arcones, Daniel A1 - Weiser, Martin A1 - Koutsourelakis, Faidon-Stelios A1 - Unger, Jörg F. T1 - Evaluation of Model Bias Identification Approaches Based on Bayesian Inference and Applications to Digital Twins T2 - 5th ECCOMAS Thematic Conference on Uncertainty Quantification in Computational Sciences and Engineering N2 - In recent years, the use of simulation-based digital twins for monitoring and assessment of complex mechanical systems has greatly expanded. Their potential to increase the information obtained from limited data makes them an invaluable tool for a broad range of real-world applications. Nonetheless, there usually exists a discrepancy between the predicted response and the measurements of the system once built. One of the main contributors to this difference in addition to miscalibrated model parameters is the model error. Quantifying this socalled model bias (as well as proper values for the model parameters) is critical for the reliable performance of digital twins. Model bias identification is ultimately an inverse problem where information from measurements is used to update the original model. Bayesian formulations can tackle this task. Including the model bias as a parameter to be inferred enables the use of a Bayesian framework to obtain a probability distribution that represents the uncertainty between the measurements and the model. Simultaneously, this procedure can be combined with a classic parameter updating scheme to account for the trainable parameters in the original model. This study evaluates the effectiveness of different model bias identification approaches based on Bayesian inference methods. This includes more classical approaches such as direct parameter estimation using MCMC in a Bayesian setup, as well as more recent proposals such as stat-FEM or orthogonal Gaussian Processes. Their potential use in digital twins, generalization capabilities, and computational cost is extensively analyzed. Y1 - 2023 UR - https://2023.uncecomp.org/proceedings/pdf/19795.pdf SP - 1 EP - 15 ER - TY - JOUR A1 - Maier, Kristina A1 - Weiser, Martin A1 - Conrad, Tim T1 - Hybrid PDE-ODE Models for Efficient Simulation of Infection Spread in Epidemiology JF - Proceedings of the Royal Society A N2 - This paper introduces a novel hybrid model combining Partial Differential Equations (PDEs) and Ordinary Differential Equations (ODEs) to simulate infectious disease dynamics across geographic regions. By leveraging the spatial detail of PDEs and the computational efficiency of ODEs, the model enables rapid evaluation of public health interventions. Applied to synthetic environments and real-world scenarios in Lombardy, Italy, and Berlin, Germany, the model highlights how interactions between PDE and ODE regions affect infection dynamics, especially in high-density areas. Key findings reveal that the placement of model boundaries in densely populated regions can lead to inaccuracies in infection spread, suggesting that boundaries should be positioned in areas of lower population density to better reflect transmission dynamics. Additionally, regions with low population density hinder infection flow, indicating a need for incorporating, e.g., jumps in the model to enhance its predictive capabilities. Results indicate that the hybrid model achieves a balance between computational speed and accuracy, making it a valuable tool for policymakers in real-time decision-making and scenario analysis in epidemiology and potentially in other fields requiring similar modeling approaches. Y1 - 2025 U6 - https://doi.org/10.1098/rspa.2024.0421 VL - 481 IS - 2306 PB - Royal Society ER - TY - JOUR A1 - Andrés Arcones, Daniel A1 - Weiser, Martin A1 - Koutsourelakis, Faidon-Stelios A1 - Unger, Jörg F. T1 - Model bias identification for Bayesian calibration of stochastic digital twins of bridges JF - Applied Stochastic Models in Business and Industry N2 - Simulation-based digital twins must provide accurate, robust and reliable digital representations of their physical counterparts. Quantifying the uncertainty in their predictions plays, therefore, a key role in making better-informed decisions that impact the actual system. The update of the simulation model based on data must be then carefully implemented. When applied to complex standing structures such as bridges, discrepancies between the computational model and the real system appear as model bias, which hinders the trustworthiness of the digital twin and increases its uncertainty. Classical Bayesian updating approaches aiming to infer the model parameters often fail at compensating for such model bias, leading to overconfident and unreliable predictions. In this paper, two alternative model bias identification approaches are evaluated in the context of their applicability to digital twins of bridges. A modularized version of Kennedy and O'Hagan's approach and another one based on Orthogonal Gaussian Processes are compared with the classical Bayesian inference framework in a set of representative benchmarks. Additionally, two novel extensions are proposed for such models: the inclusion of noise-aware kernels and the introduction of additional variables not present in the computational model through the bias term. The integration of such approaches in the digital twin corrects the predictions, quantifies their uncertainty, estimates noise from unknown physical sources of error and provides further insight into the system by including additional pre-existing information without modifying the computational model. Y1 - 2024 U6 - https://doi.org/10.1002/asmb.2897 VL - 41 IS - 3 ER - TY - JOUR A1 - Wehlitz, Nathalie A1 - Sadeghi, Mohsen A1 - Montefusco, Alberto A1 - Schütte, Christof A1 - Pavliotis, Grigorios A. A1 - Winkelmann, Stefanie T1 - Approximating particle-based clustering dynamics by stochastic PDEs JF - SIAM Journal on Applied Dynamical Systems N2 - This work proposes stochastic partial differential equations (SPDEs) as a practical tool to replicate clustering effects of more detailed particle-based dynamics. Inspired by membrane mediated receptor dynamics on cell surfaces, we formulate a stochastic particle-based model for diffusion and pairwise interaction of particles, leading to intriguing clustering phenomena. Employing numerical simulation and cluster detection methods, we explore the approximation of the particle-based clustering dynamics through mean-field approaches. We find that SPDEs successfully reproduce spatiotemporal clustering dynamics, not only in the initial cluster formation period, but also on longer time scales where the successive merging of clusters cannot be tracked by deterministic mean-field models. The computational efficiency of the SPDE approach allows us to generate extensive statistical data for parameter estimation in a simpler model that uses a Markov jump process to capture the temporal evolution of the cluster number. Y1 - 2025 U6 - https://doi.org/10.1137/24M1676661 VL - 24 IS - 2 SP - 1231 EP - 1250 ER - TY - JOUR A1 - Höfling, Felix A1 - Straube, Arthur T1 - Langevin equations and a geometric integration scheme for the overdamped limit of rotational Brownian motion of axisymmetric particles JF - Physical Review Research N2 - The translational motion of anisotropic or self-propelled colloidal particles is closely linked with the particle’s orientation and its rotational Brownian motion. In the overdamped limit, the stochastic evolution of the orientation vector follows a diffusion process on the unit sphere and is characterized by an orientation-dependent (“multiplicative”) noise. As a consequence, the corresponding Langevin equation attains different forms depending on whether Itō’s or Stratonovich’s stochastic calculus is used. We clarify that both forms are equivalent and derive them in a top-down approach from a geometric construction of Brownian motion on the unit sphere, based on infinitesimal random rotations. Our approach suggests further a geometric integration scheme for rotational Brownian motion, which preserves the normalization constraint of the orientation vector exactly. We show that a simple implementation of the scheme, using Gaussian random rotations, converges weakly at order 1 of the integration time step, and we outline an advanced variant of the scheme that is weakly exact for an arbitrarily large time step. Due to a favorable prefactor of the discretization error, already the Gaussian scheme allows for integration time steps that are one order of magnitude larger compared to a commonly used algorithm for rotational Brownian dynamics simulations based on projection on the constraining manifold. For torques originating from constant external fields, we prove by virtue of the Fokker-Planck equation that the constructed diffusion process satisfies detailed balance and converges to the correct equilibrium distribution. The analysis is restricted to time-homogeneous rotational Brownian motion (i.e., a single rotational diffusion constant), which is relevant for axisymmetric particles and also chemically anisotropic spheres, such as self-propelled Janus particles. Y1 - 2025 U6 - https://doi.org/10.1103/wzdn-29p4 VL - 7 SP - 043034 ER - TY - JOUR A1 - Schaible, Jonas A1 - Winarto, Hanifah A1 - Škorjanc, Viktor A1 - Yoo, Danbi A1 - Zimmermann, Lea A1 - Jäger, Klaus A1 - Sekulic, Ivan A1 - Schneider, Philipp‐Immanuel A1 - Burger, Sven A1 - Wessels, Andreas A1 - Bläsi, Benedikt A1 - Becker, Christiane T1 - Optimizing Aesthetic Appearance of Perovskite Solar Cells Using Color Filters JF - Solar RRL N2 - The significance of color aesthetics in photovoltaic (PV) modules gains importance, especially in design‐centric applications like building‐integrated PVs. Color filters based on distributed Bragg reflectors, consisting of alternating thin‐film layers of different refractive indices, can modify the appearance of standard silicon modules. This approach is also extended to optimize the color appearance of emerging PV technologies such as perovskite solar cells, which typically exhibit a less appealing gray–brownish appearance. In this contribution, perovskite solar‐cell stacks combined with MorphoColor color filters are presented. Angular‐resolved reflectance simulations based on wave optics and ray tracing with experimental data are validated, and the color appearance from various viewing angles is evaluated. Additionally, the impact of individual layers on color appearance and the maximum achievable short‐circuit current density in the perovskite solar cell is investigated. By applying Bayesian optimization, the color distance is minimized to the targeted appearance. Tailoring the bridging layers between the color filter and the perovskite solar cell is found to strongly influence the color impression due to the coherently combined color filter and perovskite solar cell. The presented color optimization concept allows to customize the aesthetics of emerging PV thin‐film technologies such as perovskite solar cells. Y1 - 2025 U6 - https://doi.org/10.1002/solr.202400627 VL - 9 SP - 2400627 PB - Wiley ER - TY - GEN A1 - Roche, Léo J. A1 - Betz, Fridtjof A1 - Yang, Yuhui A1 - Limame, Imad A1 - Shih, Ching-Wen A1 - Burger, Sven A1 - Reitzenstein, Stephan T1 - Inside Front Cover: Numerical Investigation of a Coupled Micropillar - Waveguide System for Integrated Quantum Photonic Circuits (Adv. Quantum Technol. 12/2024) T2 - Adv. Quantum Technol. Y1 - 2024 U6 - https://doi.org/10.1002/qute.202470036 VL - 7 SP - 2470036 ER - TY - CHAP A1 - Mukherjee, Deshabrato A1 - Burger, Sven A1 - Siefke, Thomas A1 - Gour, Jeetendra A1 - Bodermann, Bernd A1 - Petrik, Peter T1 - Modeling of dimensions and sensing properties of gold gratings by spectroscopic ellipsometry and finite element method T2 - EPJ Web of Conferences Y1 - 2024 U6 - https://doi.org/10.1051/epjconf/202430902016 VL - 309 SP - 02016 ER - TY - JOUR A1 - Djurdjevac Conrad, Natasa A1 - Tonello, Elisa A1 - Zonker, Johannes A1 - Siebert, Heike T1 - Detection of dynamic communities in temporal networks with sparse data JF - Applied Network Science N2 - Temporal networks are a powerful tool for studying the dynamic nature of a wide range of real-world complex systems, including social, biological and physical systems. In particular, detection of dynamic communities within these networks can help identify important cohesive structures and fundamental mechanisms driving systems behaviour. However, when working with real-world systems, available data is often limited and sparse, due to missing data on systems entities, their evolution and interactions, as well as uncertainty regarding temporal resolution. This can hinder accurate representation of the system over time and result in incomplete or biased community dynamics. In this paper, we compare established methods for community detection and, using synthetic data experiments and real-world case studies, we evaluate the impact of data sparsity on the quality of identified dynamic communities. Our results give valuable insights on the evolution of systems with sparse data, which are less studied in existing literature, but are frequently encountered in real-world applications. Y1 - 2025 U6 - https://doi.org/10.1007/s41109-024-00687-3 VL - 10 PB - Springer International Publishing ER - TY - JOUR A1 - Zimper, Sebastian A1 - Cornalba, Federico A1 - Djurdjevac Conrad, Natasa A1 - Djurdjevac, Ana T1 - On reduced inertial PDE models for Cucker-Smale flocking dynamics JF - Proceedings of the Royal Society A N2 - In particle systems, flocking refers to the phenomenon where particles’ individual velocities eventually align. The Cucker-Smale model is a well-known mathematical framework that describes this behaviour. Many continuous descriptions of the Cucker-Smale model use PDEs with both particle position and velocity as independent variables, thus providing a full description of the particles mean-field limit (MFL) dynamics. In this paper, we introduce a novel reduced inertial PDE model consisting of two equations that depend solely on particle position. In contrast to other reduced models, ours is not derived from the MFL, but directly includes the model reduction at the level of the empirical densities, thus allowing for a straightforward connection to the underlying particle dynamics. We present a thorough analytical investigation of our reduced model, showing that: firstly, our reduced PDE satisfies a natural and interpretable continuous definition of flocking; secondly, in specific cases, we can fully quantify the discrepancy between PDE solution and particle system. Our theoretical results are supported by numerical simulations. Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1098/rspa.2024.0675 VL - 481 PB - Royal Society ER - TY - JOUR A1 - Fischbach, Jan David A1 - Betz, Fridtjof A1 - Asadova, Nigar A1 - Tassan, Pietro A1 - Urbonas, Darius A1 - Stöferle, Thilo A1 - Mahrt, Rainer F. A1 - Burger, Sven A1 - Rockstuhl, Carsten A1 - Binkowski, Felix A1 - Sturges, Thomas Jebb T1 - A framework to compute resonances arising from multiple scattering JF - Adv. Theory Simul. Y1 - 2025 U6 - https://doi.org/10.1002/adts.202400989 VL - 8 SP - 2400989 ER - TY - JOUR A1 - Jäger, Klaus A1 - Tejada, Alvarjo A1 - Berwig, Sebastian A1 - Hammerschmidt, Martin A1 - Tockhorn, Philipp A1 - Albrecht, Steve A1 - Becker, Christiane T1 - Optical Simulations of Nanotextured All-Perovskite Tandem Solar Cells JF - Adv. Theory Simul. Y1 - 2025 U6 - https://doi.org/10.1002/adts.202400724 VL - 8 SP - 2400724 ER - TY - CHAP A1 - Binkowski, Felix A1 - Betz, Fridtjof A1 - Hammerschmidt, Martin A1 - Zschiedrich, Lin A1 - Burger, Sven T1 - Poles and Zeros in Resonant Nano-Photonic Systems T2 - 2024 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR) Y1 - 2024 U6 - https://doi.org/10.1109/CLEO-PR60912.2024.10676837 ER - TY - CHAP A1 - Jäger, Klaus A1 - Burger, Sven A1 - Aeberhard, Urs A1 - Llado, Esther Alarcon A1 - Bläsi, Benedikt A1 - Ehrler, Bruno A1 - Favre, Wilfried A1 - Fejfar, Antonín A1 - Gageot, Tristan A1 - Gordon, Ivan A1 - Helmers, Henning A1 - Höhn, Oliver A1 - Isabella, Olindo A1 - Jošt, Marko A1 - Ledinský, Martin A1 - Mandal, Jyotirmoy A1 - Manley, Phillip A1 - Munoz, Delfina A1 - Lizcano, Juan Camilo Ortiz A1 - Paetzold, Ulrich W. A1 - Raman, Aaswath P. A1 - Sai, Hitoshi A1 - Saive, Rebecca A1 - Schmid, Martina A1 - Yablonovitch, Eli A1 - Becker, Christiane T1 - A Roadmap on Optics for Terawatt Scale Photovoltaics T2 - Advanced Photonics Congress 2024 Y1 - 2024 U6 - https://doi.org/10.1364/SELED.2024.STu2G.5 SP - STu2G.5 PB - Optica Publishing Group ER - TY - JOUR A1 - Armas, Jay A1 - Merbis, Wout A1 - Meylahn, Janusz M A1 - Rafiee Rad, Soroush A1 - del Razo, Mauricio J T1 - Risk aversion can promote cooperation JF - Journal of Physics: Complexity N2 - Cooperative dynamics are central to our understanding of many phenomena in living and complex systems. However, we lack a universal mechanism to explain the emergence of cooperation. We present a novel framework for modelling social dilemma games with an arbitrary number of players by combining reaction networks, methods from quantum mechanics applied to stochastic complex systems, game theory and stochastic simulations of molecular reactions. Using this framework, we propose a novel and robust mechanism for cooperation based on risk aversion that leads to cooperative behaviour in population games. Rather than individuals seeking to maximise payouts in the long run, individuals seek to obtain a minimum set of resources with a given level of confidence and in a limited time span. We show that this mechanism can lead to the emergence of new equilibria in a range of social dilemma games. Y1 - 2025 U6 - https://doi.org/10.1088/2632-072X/adb234 VL - 6 IS - 1 ER - TY - JOUR A1 - Asadova, Nigar A1 - Achouri, Karim A1 - Arjas, Kristian A1 - Ajuguié, Baptiste A1 - Aydin, Roland A1 - Baron, Alexandre A1 - Beutel, Dominik A1 - Bodermann, Bernd A1 - Boussaoud, Kaoutar A1 - Burger, Sven A1 - Choi, Minseok A1 - Czajkowski, Krzysztof A1 - Evlyukhin, Andrey B. A1 - Fazel-Najafabadi, Atefeh A1 - Fernandez-Corbaton, Ivan A1 - Garg, Puneet A1 - Globosits, David A1 - Hohenester, Ulrich A1 - Kim, Hongyoon A1 - Kim, Seokwoo A1 - Lalanne, Philippe A1 - Le Ru, Eric C. A1 - Meyer, Jörg A1 - Mun, Jungho A1 - Patelli, Lorenzo A1 - Pflug, Lukas A1 - Rockstuhl, Carsten A1 - Rho, Junsuk A1 - Rotter, Stefan A1 - Stout, Brian A1 - Törmä, Päivi A1 - Trigo, Jorge Olmos A1 - Tristram, Frank A1 - Tsitsas, Nikolaos L. A1 - Vallée, Renaud A1 - Vynck, Kevin A1 - Weiss, Thomas A1 - Wiecha, Peter A1 - Wriedt, Thomas A1 - Yannopapas, Vassilios A1 - Yurkin, Maxim A. A1 - Zouros, Grigorios P. T1 - T-matrix representation of optical scattering response: Suggestion for a data format JF - J. Quant. Spectrosc. Radiat. Transf. Y1 - 2025 U6 - https://doi.org/10.1016/j.jqsrt.2024.109310 VL - 333 SP - 109310 ER - TY - JOUR A1 - Roche, Léo J. A1 - Betz, Fridtjof A1 - Yang, Yuhui A1 - Limame, Imad A1 - Shih, Ching-Wen A1 - Burger, Sven A1 - Reitzenstein, Stephan T1 - Numerical Investigation of a Coupled Micropillar - Waveguide System for Integrated Quantum Photonic Circuits JF - Adv. Quantum Technol. Y1 - 2024 U6 - https://doi.org/10.1002/qute.202400195 VL - 7 SP - 2400195 ER - TY - JOUR A1 - Binkowski, Felix A1 - Burger, Sven A1 - Kewes, Günter T1 - A tiny Drude scatterer can accurately model a coherent emitter in nanophotonics JF - Nanophotonics Y1 - 2024 U6 - https://doi.org/10.1515/nanoph-2024-0170 VL - 13 SP - 4537 ER - TY - JOUR A1 - Berns, Manon A1 - Yildiz, Mirza A1 - Winkelmann, Stefanie A1 - Walter, Alexander T1 - Independently engaging protein tethers of different length enhance synaptic vesicle trafficking to the plasma membrane JF - The Journal of Physiology N2 - Synaptic vesicle (SV) trafficking toward the plasma membrane (PM) and subsequent SV maturation are essential for neurotransmitter release. These processes, including SV docking and priming, are coordinated by various proteins, such as SNAREs, Munc13, and Synaptotagmin (Syt), which connect—tether—the SV to the PM. Here, we investigated how tethers of varying lengths mediate SV docking using a simplified mathematical model. The heights of the three tether types—estimated from the structures of the SNARE complex, Munc13, and Syt—defined the SV-to-PM distance ranges for tether formation. Geometric considerations linked SV-to-PM distances to the probability and rate of tether formation. We assumed that SV tethering constrains SV motility and that multiple tethers associate by independent interactions. The model predicted that forming multiple tethers favors shorter SV-to-PM distances. Although tethers acted independently in the model, their geometrical properties often caused sequential assembly, from longer ones (Munc13/Syt), that accelerated SV movement towards the PM, to shorter ones (SNAREs) which stabilized PM-proximal SVs. Modifying tether lengths or numbers affected SV trafficking. The independent implementation of tethering proteins enabled their selective removal to mimic gene knockout situations. This showed that simulated SV-to-PM distance distributions qualitatively aligned with published EM studies upon removal of SNARE and Syt tethers, while Munc13 knockout data were best approximated when assuming additional disruption of SNARE tethers. Thus, while salient features of SV docking can be accounted for by independent tethering alone, our results suggest that functional tether interactions not yet featured in our model are crucial for biological function. Y1 - 2025 U6 - https://doi.org/10.1113/JP286651 VL - 603 IS - 20 SP - 6107 EP - 6134 ER - TY - GEN A1 - Binkowski, Felix A1 - Betz, Fridtjof A1 - Hammerschmidt, Martin A1 - Zschiedrich, Lin A1 - Burger, Sven T1 - Source code and simulation results: Resonance modes in microstructured photonic waveguides - Efficient and accurate computation based on AAA rational approximation T2 - Zenodo Y1 - 2024 U6 - https://doi.org/10.5281/zenodo.14202408 SP - doi: 10.5281/zenodo.14202408 ER -