Computational Physics · Cross-listed from cond-mat.str-el
Charge-Ordered States and the Phase Diagram of the Extended Hubbard Model on the Bethe lattice
Aleksey Alekseev and Konrad Jerzy Kapcia
We study the extended Hubbard model (EHM) with both onsite Hubbard interaction and the intersite density-density interaction between nearest-neighbors using the standard Hartree mean-field approximation (MFA) on the Bethe
lattice. We found that, at the ground state, the system can be in a charge-ordered band-insulating (COI), a charge-order metallic (COM) or a non-charge-ordered (NO) state. Moreover, the finite-temperature phase diagrams are presented. Several observables like a charge-order parameter, a spectral function, and particularly at finite temperatures, a thermally-excited charge carrier concentration (to visualize the degree of
metallicity) are analyzed. The results show that increasing onsite repulsion suppresses charge order and change the properties of the system from insulating to metallic. Worth noting, that a number of phenomena can be found within the MFA, where their analysis is much simpler than in more advanced approaches. The method used for the EHM on the Bethe
lattice also allows for a series of analytical derivations and simplifications to see general geometry-independent features and analytical results, avoiding the numerical inaccuracies and other issues that appear with a purely numerical solution.
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Physics and Society
Disparity-in-Differences: Extracting Hierarchical Backbones of Weighted Directed Networks
Hyunuk Kim
Networks are useful representations for complex systems. Especially, heterogeneous and asymmetrical relations commonly found in complex systems can be converted to weighted directed edges between nodes. The disparity filter (Serrano et al., 2009) has successfully extracted backbones, sets of important edges, from empirical networks but is not designed to incorporate node-node dependency that may encode hierarchical relations. This paper proposes an extended disparity filter named "disparity-in-differences" that assigns a synthetic relation between two nodes if one depends relatively more on the other where the extent of asymmetric dependence is measured by the disparity between a normalized edge weight difference and an expected edge weight difference. For evaluation, the proposed method is applied to a journal citation network, a U.S. airport network, the Enron email network, and a world trade network. Compared to the disparity filter, the proposed approach better captures hierarchical relations that align well with journal quality ratings, airport hub categories by size, levels of management, and a core-periphery structure of countries, respectively.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci
Li-P-S Electrolyte Materials as a Benchmark for Machine-Learned Interatomic Potentials
Natascia L. Fragapane and Volker L. Deringer
With the growing availability of machine-learned interatomic potential (MLIP) models for materials simulations, there is an increasing demand for robust, automated, and chemically insightful benchmarking methodologies. In response, we here introduce LiPS-25, a curated
benchmark dataset for a canonical series of solid-state electrolyte materials from the Li2S-P2S5 pseudo-binary compositional line, including crystalline and amorphous configurations. Together with the
dataset, we present a suite of performance tests that range from conventional numerical error metrics to physically motivated evaluation tasks. With a focus on graph-based MLIP architectures, we run numerical experiments that assess (i) the effect of hyperparameters and (ii) the fine-tuning behavior of selected pre-trained ("foundational") MLIP models. Beyond the Li-P-S solid-state electrolytes, we expect that such
benchmarks and their code implementations can be readily adapted to other material systems.
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Optics
Chip-integrated Brillouin Saser Gyroscope
Wen-Qi Duan, Ming-Xuan Zhao, Jia-Qi Wang et al. (+5 more)
On-chip Brillouin
laser gyroscopes harnessing opto-acoustic interaction are an emerging approach to detect rotation, due to their small footprint, excellent stability and low power consumption. However, previous implementations rely solely on optical readout, leaving the simultaneously generated saser (sound amplification by stimulated emission) undetected due to the lack of capability to access the acoustic output. Here, we propose a gyroscope based on saser detection using a suspension-free chip platform that supports low-loss confinement of both optical and acoustic modes. With experimental feasible parameter with optical and acoustic quality factors of 10^5 and 5000, respectively, sasers show significantly suppressed thermal and frequency noises, leading to gyroscope performance that outperforms its optical counterparts. We predict an angle random walk ~0.1 deg/sqrt(h) by saser gyroscope, while a conventional Brillouin
laser gyroscope requires significantly higher pump power and optical quality factor to achieve comparable performance. Our work establishes the foundation for active phononic integrated
circuits with Brillouin gain, opening avenues in inertial sensing,
quantum transduction, and RF signal processing.
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All authors Wen-Qi Duan, Ming-Xuan Zhao, Jia-Qi Wang, Xin-Biao Xu, Luyan Sun, Guang-Can Guo, Ming Li, Chang-Ling Zou
Fluid Dynamics
General-purpose Data-driven Wall Model for Low-speed Flows Part I: Baseline Model
Yuenong Ling, Imran Hayat, Konrad Goc et al. (+1 more)
We present a general-purpose wall model for large-eddy simulation. The model builds on the building-block flow principle, leveraging essential physics from simple flows to train a generalizable model applicable across complex geometries and flow conditions. The model addresses key limitations of traditional
equilibrium wall models (EQWM) and improves upon shortcomings of earlier building-block-based approaches. The model comprises four components: (i) a baseline wall model, (ii) an error model, (iii) a classifier, and (iv) a confidence score. The baseline model predicts the wall-shear stress, while the error model estimates epistemic errors and aleatoric errors, both used for uncertainty quantification. In Part I of this work, we present the baseline model, while the remaining three components are introduced in Part II. The baseline model is designed to capture a broad range of flow phenomena, including
turbulence over curved walls and zero, adverse, and favorable mean pressure gradients, as well as flow separation and laminar flow. The problem is formulated as a regression task to predict wall shear stress using a neural network. Model inputs are localized in space and dimensionless, with their selection guided by information-theoretic criteria. Training data include, among other cases, a newly generated direct numerical simulation
dataset of turbulent boundary layers under favorable and adverse PG conditions. Validation is carried out through both a priori and a posteriori tests. The a priori evaluation spans 140 diverse high-fidelity numerical
datasets and experiments (67 training cases included), covering turbulent boundary layers, airfoils, Gaussian bumps, and full aircraft geometries, among others. We demonstrate that the baseline wall model outperforms the EQWM in 90% of test scenarios, while maintaining errors below 20% for 98% of the cases.
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All authors Yuenong Ling, Imran Hayat, Konrad Goc, Adrian Lozano-Duran
Optics
Metasurface-controlled high-speed tunable external cavity lasers
Zahra Basiri, Alessandro Tomasino, Gabriel Jülg et al. (+2 more)
Tunable
lasers are essential for optical communication, spectroscopy, and precision sensing, where flexible and fast control of the
laser wavelength is needed. However, conventional tunable
laser systems often rely on mechanical actuation, which limits their tuning speed, stability, and repeatability. Alternative tuning methods, such as adjusting the temperature of the gain medium or the injection current, are either slow or suffer from unwanted coupling between frequency and intensity. Electro-optic modulators implemented after the
laser offer fast frequency tunability but these components are bulky and prone to high insertion losses. Here, we introduce an external cavity
semiconductor laser that achieves ultrafast frequency and amplitude tunability within a compact footprint without any moving parts. The
laser employs a resonant electro-optic metasurface as the external mirror, providing narrowband feedback that enables simultaneous single-mode operation and voltage-controlled tuning across a wide range of currents. Leveraging a narrow linewidth design, we demonstrate mode-hop-free linear frequency tuning with rates of up to 70 THz/s, and frequency excursions reaching 110 MHz under a 10 V peak RF drive, clearly surpassing rates attainable through mechanical actuation. Moreover, by biasing the
laser near its threshold, our platform enables intensity modulation with an efficiency above 100% at a peak voltage of 4 V. These results highlight the platform's potential for applications requiring high-speed and mode-hop-free tunable
lasers, such as free-space optical communication,
laser ranging, and high-resolution spectroscopy.
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All authors Zahra Basiri, Alessandro Tomasino, Gabriel Jülg, Andrea Lanfranchi, Ileana-Cristina Benea-Chelmus
Physics and Society
An analytical and experimental study of the energy transition discourse on YouTube
Aleix Bassolas, Piero Birello and Julian Vicens
Energy production and management face significant political, economic, and environmental challenges, yet the rise in information consumption through social media undermines the availability of reliable knowledge to the general public. This study examines the ideas discussed in the energy transition content on YouTube, assesses the most effective methods of communicating knowledge and information to the general public, and identifies the most engaged audiences. We examine
videos related to the subject, analysing the themes discussed, the
language used, and the
emotions conveyed on YouTube, linking
language formality to user engagement. To test the relationship experimentally, we uploaded original content to YouTube through two mirror channels containing the same material but using different levels of
language formality. Our results indicate that conversational content reaches a broader audience, but retention rates are higher on the academic channel beyond the initial
video segments. Interest in the topic varies by viewer profile, with younger individuals and women showing greater engagement regardless of
language style.
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Optics
Performance Analysis of a Prime-Parameterized Fibonacci Spiral-Based Optical Phased Array
Anantha Kedar Sarma Inampudi, Anjali A R, Pranabendu Ganguly et al. (+1 more)
Optical phased arrays (OPAs) are a promising technology for realizing fast and on-chip non-mechanical beam steering. In this work, we propose and analyze the performance of a non-uniformly spaced
antenna arrangement based on the Fibonacci Spiral. A unique
prime-number-based parameterization for
antenna positioning and a tunable positional-control parameter ($\alpha$) are introduced. We show that, depending on the intended application of the OPA, by adjusting $\alpha$, we can achieve $\approx$ 56,562 resolvable points with 93
antennas arranged according to the
prime-parametrization. To the best of our knowledge, this result exceeds the reported values in existing literature for comparable non-redundant array configurations. We analyze the robustness of this design by evaluating the sensitivities of the three key performance metrics of an OPA: side-lobe suppression ratio (SLSR), field of view (FoV), and the far-field full width at half-maximum (FWHM), to the random disturbances in
antenna positions that may occur for practical implementation on a photonic chip.
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All authors Anantha Kedar Sarma Inampudi, Anjali A R, Pranabendu Ganguly, Syamsundar De
Physics Education
Efficient and affordable thermoelectric measurement setup using Arduino and LabVIEW for education and research
Alex J. Oh, Colby J. Stoddard, Craig Queenan et al. (+1 more)
Thermoelectric materials can convert thermal energy into electricity, making them promising candidates for harvesting waste heat, an increasingly important challenge in the energy-intensive modern world. The search for improved thermoelectric materials is therefore an active area of research in materials physics. Despite their fundamental and practical significance, thermoelectric properties - such as the Seebeck coefficient and power factor - are rarely explored in student labs due to the complexity in measurement schemes and requirement for sophisticated equipment. In this work, we present a user-friendly, low-cost and efficient thermoelectric measurement system built with Arduino and LabVIEW, which can simultaneously measure Seebeck coefficients and power factors as a function of temperature. This was made possible by improving the resolution of Arduino over ~1000 times with amplifiers and noise reduction schemes. With a total cost of only ~$100 and simple measurement protocols, this setup is well suited not only for student labs but also for efficient thermoelectric research.
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All authors Alex J. Oh, Colby J. Stoddard, Craig Queenan, Seongshik Oh
Optics
Tunable integrated ring resonators by femtosecond laser micromachining
Giulio Gualandi, Fabio Saretto, Daniele Pedroli et al. (+4 more)
Femtosecond
Laser Micromachining (FLM) is a powerful technology for the fabrication of photonic devices. In this context, the integration of resonant elements within the platform represents a key advancement, enhancing both its versatility and its compatibility with a wide range of optical and fluidic components specifically enabled by this technique. Here, we report the realization of a tunable racetrack resonator fabricated by FLM and operating at telecom wavelengths. Leveraging low-loss waveguides, we obtained a Q factor of the resonator as high as 8 x 10^5 at critical coupling. Moreover, by integrating two thermo-optic phase shifters, we achieved both resonance tuning and dynamic control of the Q factor. This capability makes the device highly versatile for applications requiring dynamic spectral control, such as tunable filters, gyroscopes, and sensors.
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All authors Giulio Gualandi, Fabio Saretto, Daniele Pedroli, Giacomo Corrielli, Marco Liscidini, Roberto Osellame, Andrea Crespi
Optics
Experimental Realization of All-Optical Terahertz Attoclock
Yanjun Gao, Yizhu Zhang, Yulin Chen et al. (+8 more)
The attoclock is a powerful tool for probing ultrafast electron dynamics with attosecond precision.Here, we demonstrate an all-optical terahertz (THz) attoclock that reconstructs photoionization dynamics by detecting the THz radiation emitted from Ar atoms ionized by two-color (800 nm/400 nm)
laser fields. In this approach, the polarization direction of the emitted THz field reflects the direction of the photoelectron drift velocity and thus serves as a direct observable that encodes the effective ionization delay, analogous to the angular deflection of photoelectrons in conventional attoclocks. By precisely tailoring the relative phase and ellipticity of the driving fields, we observe intensity-dependent rotations of the THz polarization. These rotations, which reveal changes of the effective delay, are consistent with both conventional attoclock measurements and time-dependent Schrödinger equation simulations. Our experiment establishes the feasibility of the THz attoclock as a
vacuum-free and contactless probe of tunneling dynamics, offering a transformative alternative for investigating condensed-matter systems where photoelectron detection is challenging.
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All authors Yanjun Gao, Yizhu Zhang, Yulin Chen, Jingjing Zhao, Meng Li, Xiaokun Liu, Yange Chen, Jiahui Guo, Kiyoshi Ueda, Ahai Chen, Yuhai Jiang
Biological Physics
Mesoscale tissue properties and electric fields in brain stimulation: Bridging the macroscopic and microscopic scales using layer-specific cortical conductivity
Boshuo Wang, Torge H. Worbs, Minhaj A. Hussain et al. (+4 more)
Accurate simulations of electric fields (E-fields) in neural stimulation depend on tissue conductivity representations that link underlying microscopic tissue structure with macroscopic assumptions. Mesoscale conductivity variations can produce meaningful changes in E-fields and neural activation thresholds but remain largely absent from standard macroscopic models. Conductivity variations within the cortex are expected given the differences in
cell density and volume fraction across layers. We review recent efforts modeling microscopic and mesoscopic E-fields and outline approaches that bridge micro- and macroscales to derive consistent mesoscale conductivity distributions. Using simplified microscopic models, effective tissue conductivity was estimated as a function of volume fraction of extracellular space, and the conductivities of different cortical layers were interpolated based on experimental volume fraction. The effective tissue conductivities were monotonically decreasing convex functions of the
cell volume fraction. With decreasing
cell volume fraction, the conductivity of cortical layers increased with depth from layer 2 to 6. Although the variation of conductivity within the cortex was small when compared to the conductivity of extracellular fluid (9% to 15%), the conductivity difference was considerably larger when compared between layers, e.g., with layer 3 and 6 being 20% and 50% more conductive than layer 2, respectively. The review and analysis provide a foundation for accurate multiscale models of E-fields and neural stimulation. Using layer-specific conductivity values within the cortex could improve the accuracy of estimations of thresholds and distributions of neural activation in E-field models of
brain stimulation.
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All authors Boshuo Wang, Torge H. Worbs, Minhaj A. Hussain, Aman S. Aberra, Axel Thielscher, Warren M. Grill, Angel V. Peterchev
Chemical Physics
Connecting Collisional and Photofragmentation Resonances in the H$_2$ Ungerade Symmetry
Dávid Hvizdoš, Roman Čurík and Chris H. Greene
A recently developed energy-dependent frame transformation theory that incorporates both ionization and dissociation channels of the H$_2$ molecule, is extended to treat the ungerade states that occur both in dissociative recombination and as the final state in ground state photoabsorption. The theoretical treatment includes the rotational degrees of freedom and is benchmarked against a two-dimensional model that can be solved with high accuracy and also compared with photoabsorption experiments. Analysis of the resulting spectra shows how the same resonances appear in very different observables, often with quite different line shapes.
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Data Analysis and Statistics · Cross-listed from cond-mat.stat-mech
Distinguishing thermal versus quantum annealing using probability-flux signatures across interaction networks
Yoshiaki Horiike and Yuki Kawaguchi
Simulated annealing provides a heuristic solution to combinatorial optimization problems. The cost function of a problem is mapped onto the energy function of a physical many-body system, and, by using thermal or
quantum fluctuations, the system explores the state space to find the ground state, which corresponds to the optimal solution of the problem. Studies have highlighted both the similarities and differences between thermal and
quantum fluctuations. Nevertheless, fundamental understanding of thermal and
quantum annealing remains incomplete, making it unclear how
quantum annealing outperforms thermal annealing in which problem instances. Here, we investigate the many-body dynamics of thermal and
quantum annealing by examining all possible interaction networks of $\pm J$ Ising
spin systems up to seven
spins. Our comprehensive investigation reveals that differences between thermal and
quantum annealing emerge for particular interaction networks, indicating that the structure of the energy landscape distinguishes the two dynamics. We identify the microscopic origin of these differences through probability fluxes in state space, finding that the two dynamics are broadly similar, but that
quantum tunnelling produces qualitative differences. Our results provide insight into how thermal and
quantum fluctuations navigate a system toward the ground state in simulated annealing, and are experimentally verifiable in atomic, molecular, and optical systems. Furthermore, these insights may improve mappings of optimization problems to Ising
spin systems, yielding more accurate solutions in faster simulated annealing and thus benefiting real-world applications in industry. Our comprehensive survey of interaction networks and visualization of probability flux can help to understand, predict, and control
quantum advantage in
quantum annealing.
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Optics
Stable high-charge vortex dissipative solitons in azimuthally modulated waveguide arrays with localized gain
Changming Huang, Qidong Fu and Li Ma
We study the existence and dynamical properties of
vortex solitons in Kerr media supported by azimuthally modulated waveguide
lattices with localized gain and nonlinear loss. In this dissipative system, we find that the accessible topological charge of
vortex solitons is strongly determined by the number of waveguide channels, with higher-order charges requiring progressively larger arrays. Power curves of
vortex solitons with different charges exhibit clear separation in large arrays but become less distinguishable in smaller ones. Furthermore, these robust
vortex solitons can be excited with nearly vanishing power thresholds, and higher-charge
vortices display enhanced propagation stability compared with lower-charge states. These findings expand the family of dissipative
vortex solitons supported by waveguide
lattices and provide a route to the realization of stable high-
symmetry vortex states.
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Computational Physics
A physics-inspired nonlinear momentum method for gradient descent with applications to inverse photonic design
Jianing Zhang and Rumei Liu
In this work, a nonlinear momentum method is introduced to enhance the convergence performance of momentum-based gradient optimization
algorithms. Classical momentum methods, such as the Heavy Ball method, can be viewed as a dynamical system with quadratic kinetic energy and linear damping. By extending this analogy to non-Newtonian dynamical systems, we construct a
Hamiltonian framework for optimization problems. In this framework, nonlinear kinetic energy and nonlinear damping effects naturally emerge. It provides a more flexible and physically interpretable mechanism for optimization
algorithms. Specifically, we employ an anharmonic kinetic energy function to capture the inertial effects of accumulated gradient information during the optimization process, while the nonlinear damping mechanism effectively regulates the contribution of momentum during convergence. Numerical experiments show that the proposed method achieves faster convergence compared to classical momentum
algorithms, making it particularly suitable for inverse design tasks. Moreover, the
Hamiltonian based algorithmic framework may offer physical insights for the development of efficient physics-inspired optimization
algorithms.
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Chemical Physics
Black-Box Uncertainty Estimation for Deep Learning Models in Atomistic Simulations
Idan Fonea, Amir Peles, Sivan Niv et al. (+2 more)
We analyze an ensemble-based approach for uncertainty quantification (UQ) in atomistic neural networks. This method generates an epistemic uncertainty signal without requiring changes to the underlying multi-headed regression neural network architecture, making it suitable for sealed or black-box models. We apply this method to molecular systems, specifically sodium (Na) and aluminum (Al), under various temperature conditions. By scaling the uncertainty signal, we account for heteroscedasticity in the data. We demonstrate the robustness of the scaled UQ signal for detecting out-of-distribution (OOD) behavior in several scenarios. This UQ signal also correlates with model convergence during training, providing an additional tool for optimizing the training process.
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All authors Idan Fonea, Amir Peles, Sivan Niv, Goren Gordon, Amir Natan
Fluid Dynamics
Fourth branch of instability of Stokes' wave and dependence of corresponding growth rate on nonlinearity
A.O. Korotkevich and A.O. Prokofiev
Through a massive computation we reached the fourth superharmonic instability branch of the Stokes' wave. Using the obtained results we checked phenomenological formulae for the dependence of the instability growth rates corresponding to different branches of instability on the nonlinearity parameter (steepness, defined as the wave \red{hight} to wavelength ratio $H/\Lambda$) in the vicinity of the new instability branch appearance and far from it. It is demonstrated, that the formulae, obtained as a least squares fit (using the information from the first three branches of instability) and a phenomenological asymptotics, work for the fourth branch as well. Range of applicability of the relations \red{is} corrected. \red{This result removes the necessity to compute further branches of instability if accuracy better than 10% for the growth rate is acceptable.} Growth rates for all four instability branches are reported.
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Plasma Physics
Algorithms and optimizations for global non-linear hybrid fluid-kinetic finite element stellarator simulations
Luca Venerando Greco
Predictive modeling of stellarator
plasmas is crucial for advancing
nuclear fusion energy, yet it faces unique computational difficulties. One of the main challenges is accurately simulating the dynamics of specific particle species that are not well captured by fluid models, which necessitates the use of hybrid fluid-kinetic models. The non-axisymmetric geometry of stellarators fundamentally couples the toroidal
Fourier modes, in contrast to what happens in tokamaks, requiring different numerical and computational treatment. This work presents a novel, globally coupled projection scheme inside the JOREK finite element framework. The approach ensures a self-consistent and physically accurate transfer of kinetic markers to the fluid grid, effectively handling the complex 3D mesh by constructing and solving a unified linear system that encompasses all toroidal harmonics simultaneously. To manage the computational complexity of this coupling, the construction of the system's
matrix is significantly accelerated using the Fast
Fourier Transform (FFT). The efficient localization of millions of particles is made possible by implementing a 3D R-Tree spatial index, which supports this projection and ensures computational tractability at scale. On realistic Wendelstein 7-X stellarator geometries, the fidelity of the framework is rigorously shown. In sharp contrast to the uncoupled approaches' poor performance, quantitative convergence tests verify that the coupled scheme attains the theoretically anticipated spectral convergence. This study offers a crucial capability for the predictive analysis and optimization of next-generation stellarator designs by developing a validated, high-fidelity computational tool.
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Instrumentation and Detectors
Development & Characterization of Electrodes for large-scale Xenon Time Projection Chambers
A. Elykov, S. Vetter, V. H. S. Wu et al. (+16 more)
Dual-phase
liquid xenon time projection chambers are the core detector elements of many experiments that conduct searches for Dark Matter and rare events, as well as in
neutrino and high-energy physics. As part of this detector technology, high-voltage electrodes are instrumental for the generation of observable signals and their physical interpretation. Thus, electrode design and manufacturing has to fulfill stringent requirements, and their production is associated with significant engineering challenges. In this work we describe the successful development of electrodes on the 1.5 m-scale, from their design and simulation to subsequent assembly and high-voltage testing in a gaseous argon environment. The produced electrodes were recently installed as an anode and a cathode during an upgrade to the XENONnT experiment.
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All authors A. Elykov, S. Vetter, V. H. S. Wu, A. Deisting, K. Eitel, R. Gumbsheimer, M. Kara, S. Lichter, S. Lindemann, T. Luce, Y. Ma, J. Müller, K. Müller, K. Ni, U. Oberlack, M. Schumann, P. Shagin, K. Valerius, M. Zhong
Applied Physics
Solar cells and thermoelectric generators as finite-time chemical heat engines
Tom Markvart
This paper shows a fundamental thermodynamic similarity between thermoelectric and photovoltaic energy converters which, at open
circuit, can be represented as isochoric engines generating a finite chemical potential which appears as voltage at the terminals of the device. We show that, allowing for the temperature variation of the Seebeck coefficient, the maximum energy efficiency is intrinsically lower than the Carnot efficiency, as assumed in most of the literature, although more sophisticated strategies may exist to recuperate this loss. At finite current, further losses can be modelled in terms of finite-time thermodynamics.
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Optics
Observation of nonlinear higher-order topological insulators with unconventional boundary truncations
Changming Huang, Alexander V. Kireev, Yuxin Jiang et al. (+10 more)
In higher-order topological
insulators (HOTIs), topologically nontrivial phases are usually associated with the shift of Wannier centers to topologically nontrivial positions on the edges of the unit
cells, and the emergence of fractional spectral charges in the corners of the
lattice upon its truncation that keeps the number of its unit
cells integer. Here we propose theoretically and illustrate experimentally a different approach to the construction of HOTIs. This approach utilizes
lattices with incomplete unit
cells and achieves localized modes of topological origin across a broader parameter space. When truncation disrupts translational
symmetry by cutting through the interior of multiple unit
cells, boundary modes in our system emerge for both trivial and topologically nontrivial positions of the Wannier centers. We link these modes to the appearance of fractional Wannier centers. We also demonstrate that linear boundary states give rise to rich families of stable
solitons bifurcating from them in the presence of focusing nonlinearity. Multiple types of thresholdless topological
solitons with different internal
symmetries are observed in waveguide arrays with triangular configurations featuring incomplete unit
cells for any dimerization of waveguide spacings. Our results expand the family of HOTIs and pave the way for the observation of boundary states with different
symmetries.
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All authors Changming Huang, Alexander V. Kireev, Yuxin Jiang, Victor O. Kompanets, Ce Shang, Yaroslav V. Kartashov, Sergei A. Zhuravitskii, Nikolay N. Skryabin, Ivan V. Dyakonov, Alexander A. Kalinkin, Sergei P. Kulik, Fangwei Ye, Victor N. Zadkov
Space Physics
Editorial: Impacts of the Extreme Gannon Geomagnetic Storm of May 2024 throughout the Magnetosphere-Ionosphere-Thermosphere System
Denny M. Oliveira, Mirko Piersanti, Maria-Theresia Walach et al. (+4 more)
Editorial for the Research Topic collection Impacts of the Extreme Gannon Geomagnetic Storm of May 2024 throughout the Magnetosphere-Ionosphere-Thermosphere System, published in Frontiers in Astronomy and Space Science.
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All authors Denny M. Oliveira, Mirko Piersanti, Maria-Theresia Walach, Livia R. Alves, W. Kent Tobiska, Xochitl Blanco-Cano, Katariina Nykyri
Atomic and Molecular Clusters
Exceptional-Point-Induced Sensitivity-Robustness Phase Transition in Quantum Interference
Xing Lin and Shuang Zhang
Quantum interference underpins many
quantum information protocols but is typically studied in lossless Hermitian systems. Here, we reveal an exceptional point induced phase transition in two
photon Hong Ou Mandel interference within a lossy coupled waveguide system. In the PT symmetric phase. interference is ultrasensitive to coupling strength, yielding sharp bunching antibunching switches. In the PT broken phase. it becomes robust oscillation free and propagation independent with coincidence probability stably tunable via coupling. These regimes enable enhanced
quantum sensing and reliable two
photon control for robust
quantum information processing.
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Optics
Reconstructive comb spectroscopy: A single-pixel detection paradigm beyond dual-comb limitations
Dongxu Zhu, Zhuoren Wan, Xiaoshuai Ma et al. (+13 more)
Frequency comb spectroscopy has revolutionized broadband molecular fingerprinting with mode-defined resolution. While dual-comb spectroscopy stands as a dominant paradigm for high-resolution measurements, it relies on mutually coherent dual combs, and its applicability to non-cooperative sensing is limited by the requirement for phase-sensitive detection and controlled optical returns. Here, we introduce reconstructive comb spectroscopy, a fundamentally different paradigm that eliminates these constraints. By integrating a mode-programmable optical comb with a computational sensing scheme based on single-pixel detection, our method achieves picometer-level spectral resolution over a 10-nm (1.27-THz) instantaneous bandwidth, with single-
photon sensitivity down to 10^-4
photons per pulse, and compressed spectral acquisition at 2.5% sampling while maintaining reconstruction errors below 10%. We demonstrate robust performance through scattering media and from non-cooperative targets. These capabilities establish reconstructive comb spectroscopy as a new platform for gas sensing, with broad applicability in remote atmospheric monitoring, industrial leak detection, and standoff chemical-threat identification.
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All authors Dongxu Zhu, Zhuoren Wan, Xiaoshuai Ma, Chongyuan Shui, Yifan Yang, Yuan Chen, Mei Yang, Zijian Wang, Xiuxiu Zhang, Min Li, Hua Li, Kun Huang, Ming Yan, Yan Liang, Weiwei Cai, Heping Zeng
Atomic and Molecular Clusters
Contact cluster modeling of allosteric communication in PDZ domains
Emanuel Dorbath, Fabian Rudolf, Adnan Gulzar et al. (+1 more)
Allostery, the intriguing phenomenon of long-range communication between distant sites in
proteins, plays a central role in biomolecular regulation and signal transduction. While it is commonly attributed to conformational rearrangements, the underlying dynamical mechanisms remain poorly understood. The contact cluster model of allostery [J. Chem. Theory Comput. 2024, 20, 10731-10739] identifies localized groups of highly correlated contacts that mediate interactions between secondary structure elements. This framework proposes that allostery proceeds through a multistep process involving cooperative contact changes within clusters and communication between distant clusters, transmitted through rigid secondary structures. To demonstrate the validity and generality of the model, this Perspective employs extensive molecular dynamics simulations ($\sim1\,$ms total simulation time) of four different photoswitchable PDZ domains and studies how different domains, ligands, and perturbations influence both the contact clusters and their dynamical
evolution. These analyses reveal several recurring clusters that represent shared flexible structural modules, such as loops connecting $\beta$-sheets, and show that the characteristic time scales of the nonequilibrium
protein response can be directly associated with the motions of individual contact clusters. Thus, the dynamic decomposition of PDZ domains into contact clusters uncovers a modular, dynamics-based architecture that underlies and facilitates long-range allosteric communication.
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All authors Emanuel Dorbath, Fabian Rudolf, Adnan Gulzar, Gerhard Stock
Optics
Theoretical Analysis of Chirped Pulse Effects on Plasma Formation in Water Liquid Jet
Shireen Hilal, Azat O. Ismagilov, Anton N. Tsypkin et al. (+1 more)
We present a theoretical study of how linear chirp controls
plasma density in a water jet using a two-stage framework. Stage I solves carrier-population and current equations at a single point, driven by a chirped super-Gaussian pulse. By fixing bandwidth and normalizing for intensity, we isolate a chirp-only response of
plasma density, which exceeds unity and shows a consistent advantage for negative over positive chirp. Stage II propagates the field in water via the angular-spectrum method and applies the same equations across space. Normal dispersion reverses the trend: the chirp-only
plasma density decreases as chirp grows, negative chirp remains less detrimental, and suppression is strongest for longer FTL pulses (e.g., 80 fs) due to dispersion-induced temporal spreading and spatio-temporal desynchronization. This study separates spectral-phase effects from bandwidth and intensity, yields testable predictions for water jets, and provides a foundation for future experiments and self-consistent propagation models.
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All authors Shireen Hilal, Azat O. Ismagilov, Anton N. Tsypkin, Maksim V. Melnik
Applied Physics
A damage detection method of plate structure using fan-shaped sensor clusters
Hand Yue, Ma Chenning, Liu Jinxia et al. (+3 more)
Plate structures are widely used in large-scale engineering fields such as aerospace, hull manufacturing, and construction. However, the plate structure is easily damaged during long-term service or when it is impacted by foreign objects. Such a damage may lead to serious safety accidents. Beamforming and L-shaped sensor cluster (LSSC) localization method can be used to locate the damage on the plate. However, when using beamforming or LSSC localization method to locate the damages on plate-like structures, there exists blind area. In this paper, by combining the beamforming and LSSC localization method, a fan-shaped sensor cluster is proposed through arranging five sensors in a fan shape, which can effectively reduce the blind areas. The positions of damages on the plate can be accurately detected by using two groups of fan-shaped sensor clusters and one sensor for transmitting the excitation signal. The feasibility of the fan-shaped sensor cluster localization method is verified through numerical simulations and experiments, and the results are compared with those obtained by using the T-shaped sensor cluster. The results show that the fan-shaped sensor cluster can more accurately identify the damages at different positions. Both simulation and experimental results indicate that the fan-shaped sensor cluster can improve the accuracy of damage location.
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All authors Hand Yue, Ma Chenning, Liu Jinxia, Zhou Zixian, Yan Shouguo, Cui Zhiwen
Fluid Dynamics · Cross-listed from math.AP
Dynamics of Ideal Fluid Flows
Tarek M. Elgindi
We will discuss various aspects of the incompressible Euler equation. We will discuss, in particular, problems related to the least action principle, the existence of special solutions, the problem of solvability, singularity formation, and asymptotic behavior.
Fluid Dynamics
From nature to engineering: Bio-inspired spacer solutions for membrane distillation
Alaa Adel Ibrahim and Stephan Leyer
Biomimetic design principles, inspired by the structure of alligator osteoderms, are employed to provide innovative solutions for enhancing membrane
distillation system performance. A novel spacer design for membrane
distillation (MD) systems is introduced, incorporating the unique structural features of these natural formations. Three-dimensional computational fluid dynamics (CFD) simulations are performed to investigate nine new spacer configurations, with particular emphasis placed on enhancing mixing efficiency within the feed channel, which serves as the primary focus of this research. Results demonstrate that the novel spacer configurations exhibit superior performance, achieving up to a fivefold increase in mixing efficiency relative to the baseline of an empty channel. Furthermore, the new spacers are assessed and contrasted with two types of conventional spacers and the empty channel configuration with respect to pressure drop, thermal performance, and mass transfer properties.
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