Chemical Physics
Thermodynamically consistent modeling of ion exchange membranes in multi-ionic environments
Noah Lettner, Felix K. Schwab and Birger Horstmann
Ion exchange membranes are useful for a wide range of applications, including water desalination, fuel
cells, and aqueous batteries. Accordingly, a variety of models for ion exchange membranes has been proposed, each emphasizing different aspects that govern their static and dynamic properties. By reviewing these models, we identify key physical contributions and beneficial modeling strategies. Based on these insights, we derive a thermodynamically consistent model by combining mass-action site occupation with mean-field electrostatic interactions along the
polymer backbone. In this derivation, we explicitly account for multicomponent electrolytes at elevated concentrations. The parameters of the resulting model relate closely to those of other models, but gain consistency and interpretability through the underlying derivation. A discussion of the model parameters highlights redundancies and linkages between quantities that are commonly treated independently. Comparison to experimental data shows that both static and dynamic membrane properties are reproduced with good accuracy by the presented model. This makes it a promising basis for theory-driven membrane optimization and supports the tailored design of ion exchange membranes for various technologies.
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Computational Physics · Cross-listed from math.NA
A Fourth-order Conservative Adaptive Multiresolution Wavelet Upwind Scheme for Compressible Flows
Bing Yang, Xiaojing Liu, Youhe Zhou et al. (+2 more)
A fourth-order conservative adaptive multiresolution average-interpolating wavelet upwind scheme is proposed for compressible flows governed by
hyperbolic conservation laws. A family of asymmetric average-interpolating wavelets with upwind properties is constructed for conservative finite volume discretization, while symmetric average-interpolating wavelets are employed for multiresolution decomposition and reconstruction of physical variables in the adaptive procedure. Since both the conservative discretization and the adaptive multiresolution representation are constructed from
cell-average quantities, the proposed scheme preserves strict conservation during both numerical
evolution and adaptive
cell redistribution. Unlike hybrid adaptive wavelet methods that use wavelets mainly for data compression and mesh adaptation, the present adaptive wavelet upwind scheme utilizes average-interpolating wavelet multiresolution approximation to reconstruct the interface values directly for numerical flux evaluation, thereby avoiding additional ghost-
cell marking and reconstruction near coarse–fine mesh interfaces. The boundary variation diminishing reconstruction is incorporated at the finest resolution level to achieve non-oscillatory shock-capturing capability. Numerical tests demonstrate that the proposed scheme achieves the expected fourth-order accuracy, maintains conservation errors close to machine precision, and controls numerical errors around the prescribed threshold. The proposed method also sharply captures shock waves and contact discontinuities without spurious oscillations and resolves multiscale smooth structures through a sparse adaptive representation. These results indicate that the proposed scheme provides an efficient, conservative, and reliable approach for high-resolution simulations of compressible flows.
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All authors Bing Yang, Xiaojing Liu, Youhe Zhou, Feng Xiao, Jizeng Wang
Optics · Cross-listed from astro-ph.IM
On-sky binary source hypothesis testing beyond the diffraction limit using spatial mode demultiplexing based detection
John S. Wallis, Ayden S. McCann, Joshua J. Collier et al. (+4 more)
Improving the resolution of
telescope systems will provide the opportunity to study new physical phenomena in previously unobserved environments. Spatial mode de-multiplexing (SPADE) based imaging is a promising and rapidly evolving technique for pushing the resolution of optical
telescopes beyond the diffraction limit. A key application of this technique is for near-optimal hypothesis testing for the presence of secondary and extended sources in the sub-diffraction regime. We present the first demonstration of a binary-SPADE based hypothesis testing instrument deployed on-sky. In our proof-of-principle experiment, based on mode demultiplexing with a double clad fiber coupler, we demonstrate detection of a binary
star system separated below the diffraction limit. We perform measurements in the
photon-starved regime where no image can be formed by traditional direct imaging. We find the scaling of the system's type II error rate (the “binary source miss" chance) was heavily limited by unbalanced loss in our double-clad fiber coupler when compared to the idealized
quantum limits. Despite this the evaluated type II error is always lower than a perfect direct imaging measurement. We expect that if this instrument is scaled to larger aperture
telescope systems the effects of atmospheric
turbulence will further degrade this system's performance.
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All authors John S. Wallis, Ayden S. McCann, Joshua J. Collier, Lilani D. Toms-Hardman, Alex M. Frost, Benjamin P. Dix-Matthews, David R. Gozzard
Biological Physics · Cross-listed from cond-mat.stat-mech
Equilibrium cluster statistics of cooperative and anticooperative binding on finite one-dimensional rings
Thomas Alfonsi, Jérôme Dorignac, John Palmeri et al. (+1 more)
We study
equilibrium clustering in a finite one-dimensional
lattice gas of $L$ sites with periodic boundary conditions, as a minimal model for adsorption and binding on small ring-like substrates. Using a grand-canonical formulation with nearest-neighbor coupling, we derive exact finite-size expressions for the mean occupancy, the mean number of domain walls, and the mean number of clusters. Building on exact $k$-site correlation functions, we further derive expressions for the mean number of clusters of size $k$ and for two complementary size statistics: the cluster-size distribution, and the site-weighted cluster-size distribution. These observables characterize how spatial organization changes across attractive (cooperative) and repulsive (anticooperative) interactions, and highlight finite-size and parity-dependent effects of the underlying
lattice, the latter being particularly pronounced near half filling in small systems. To access larger
lattices without enumerating all $2^L$ microstates, we also develop a cluster-based combinatorial formulation in which configurations are classified by cluster counts and sizes, reducing the effective state space to a set whose size scales with integer partitions, $\approx e^{\sqrt{L}}$, rather than with $\approx e^{L}$. Taken together, our results provide exact
benchmarks for finite periodic systems and suggest experimentally relevant cluster observables that complement occupancy-based measures of cooperativity, with particular relevance for binding on ring-like substrates for biological assemblies.
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All authors Thomas Alfonsi, Jérôme Dorignac, John Palmeri, Nils-Ole Walliser
Optics
Broken-symmetry phenomena enhanced by quasi-bound states in the continuum
Jan David Fischbach, Lukas Rebholz, Nikita Ustimenko et al. (+3 more)
Many of the most powerful and elegant models in physics are grounded in
symmetries. In electrodynamics, for example,
geometric symmetries govern the observable effects of light-matter interactions. However, for man-made objects, exact
symmetries are rarely met and tiny deviations are common. Nonetheless, even approximate
symmetries keep many
symmetry-derived rules effectively intact. However, as we will show here, this is not universally true. We demonstrate that an incremental violation of the
symmetry of a carefully designed system can produce an optical response maximally different from the unbroken
symmetry case. To do so, we exploit
symmetry-protected quasi-bound states in the continuum (qBICs). Specifically, we design a four-fold rotationally symmetric metasurface composed of nearly dual-symmetric meta-atoms that supports a pair of spectrally aligned electric and
magnetic qBICs. At normal incidence,
symmetry forbids helicity-preserving reflection. However, for arbitrarily small deviations from normal incidence, the strong resonant enhancement associated with the qBICs overcomes the near-
symmetry suppression and enables perfect helicity-preserving reflection. This rapidly emerging violation of
symmetry-rules reveals a fundamental intricacy when it comes to treating near-symmetric systems. At the same time, our work opens the door to novel applications in metrology and sensing.
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All authors Jan David Fischbach, Lukas Rebholz, Nikita Ustimenko, Markus Nyman, Carsten Rockstuhl, Ivan Fernandez-Corbaton
Physics and Society
Making Sense of Symbols: Yin and Yang in Zurich
Frank Schweitzer
The widely known Yin-Yang symbol (Taijitu) is based on nested circles of different radii whose areas are colored black and white such that the interface traces an $\mathcal{S}$-shaped curve. We address the question of how this symbol can be related to physical phenomena such as daytime and nighttime duration and the annual seasons. Using a simple dynamic model of daytime duration, we introduce the excess daytime fraction and reconstruct the symbol using the latitude of Zurich. In particular, we explain how the black and white areas are linked to the stability of Yin or Yang predominance. We further demonstrate that the Golden and Silver Ratios found in the geometry of the symbol carry meaning with respect to the Gregorian calendar. Finally, we construct an alternative Yin-Yang symbol using logarithmic spirals with the Golden Ratio as the growth parameter. The didactical quantitative derivation of the Yin-Yang symbol and its grounding in real-world observations can be regarded as a novel perspective on this iconic pattern.
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Classical Physics
Crack opening and closure detection through coupled DCPD and non-continuous DIC method – Application to LCF tests
Théotime Asselin, Olivier Ancelet, Guillaume Benoit et al. (+3 more)
The crack closure effect of a low-alloyed steel subjected to low-cycle fatigue loading has been characterized at two different imposed strain amplitudes. Two techniques (non-continuous DIC H-DIC and DCPD) have been employed in this aim, leading to similar conclusions. Thus, it is shown that the crack does not remain completely closed during a part of the compressive portion of the fatigue cycle for both applied loadings. The crack opening strains, combined with the cyclic stress-strain curve of the material allowed to determine an equivalent cyclic opening stress. This confirmed that the crack opening stresses decrease with the applied maximum stress when subjected to tension-compression loading, as commonly found in the literature.
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All authors Théotime Asselin, Olivier Ancelet, Guillaume Benoit, Florence Hamon, Valéry Valle, Gilbert Hénaff
Optics
Optimization of vacuum acceleration with radially polarized laser beams having phase aberrations
Spencer W. Jolly
The strong electric fields from tightly-focused and ultrashort
laser beams have always been discussed as a way to accelerate charged particles without any need for a medium or external cavity. Radially-polarized light is one way to do this, motivated by the emergence of longitudinal electrical fields with tight focusing. However, the
laser pulse will generally quickly overtake the electrons under its influence, and every-other half-cycle will decelerate the electrons in effect partially reversing the acceleration. In this work we present the effect of optical aberrations, primarily spherical aberration, and how despite their purely spatial nature they can significantly optimize the net acceleration, and advantageously allow for longer pulses to drive this optical field-based process. We discuss the optical physics responsible for this increase in performance and find optimal aberration profiles using a
stochastic algorithm.
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Computational Physics
High-Order Simulation of Particle-Laden Flows in Moving Domains Using Coupled ALE and Sliding Mesh Approaches
Anna Schwarz and Patrick Kopper
In practical applications, compressible particle-laden flows in moving geometries involve complex, non-linear, and multi-scale inter-actions with turbulent structures. Resolving these dynamics numerically requires careful algorithmic treatment to accurately predict particle trajectories. This work presents a high-fidelity Euler-Lagrange framework that couples a high-order discontinuous Galerkin spectral element method for the continuous phase with a Lagrangian point-particle tracking scheme. To manage moving and deforming domains, the framework integrates two distinct mesh movement strategies: the arbitrary Lagrangian-Eulerian method for general mesh deformations such as time-resolved particle-induced surface deformations and its special interface case, the sliding mesh approach, uniquely suited for rigid rotational or translational movements. A primary focus is placed on tightly coupling the arbitrary Lagrangian-Eulerian formulation into the temporal
evolution step by utilizing radial basis function morphing to capture the non-linear feedback loop between evolving surface
topologies and the continuous phase. Concurrently, the framework ensures time- and high-order accurate coupling of the mesh movement
algorithms with the dispersed phase. In particular, the proposed
algorithm resolves the sliding mesh tracking problem by enforcing strict spatial and temporal accuracy as Lagrangian particles cross non-conforming grid interfaces between adjacent moving zones. The
algorithms are rigorously validated against multiple
benchmarks and subsequently applied to two challenging compressor rotor applications: the first focusing on solid-particle erosion, and the second featuring an upstream cylindrical wake generator.
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Physics and Society · Cross-listed from cond-mat.stat-mech
Thermodynamic description of wealth inequality in the world
Klaus M. Frahm, Leonardo Ermann and Dima L. Shepelyansky
According to the recent Wealth Thermalization Hypothesis (WTH) the wealth inequality in the world is described by the Rayleigh-Jeans (RJ) thermal distribution of interacting
agents in a society with social stratification. In this concept, the wealth layers of society are associated with energy levels from a nonlinear dynamical system conserving two integrals of motion being total energy and probability norm. This leads to RJ condensation and the formation of a huge poverty phase of low wealth and a tiny oligarchic phase that captures a main part of total society wealth. This RJ phenomenon has similarities with self cleaning in multimode optical fibers and constraint driven condensation in various physical systems. We analyze real Lorenz and Pareto curves for wealth of households in countries and the world, Gross Domestic Product of countries,
market capitalization of companies at stock exchange of Hong Kong, Shanghai, London, bitcoin transactions, world trade between countries and show that the WTH theory gives a good description of these curves. On the basis of this comparison we argue that the RJ thermal distribution provides a universal description of wealth inequality in the world.
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Instrumentation and Detectors
A High-Precision Frequency Locking Method Based on All-Phase FFT Demonstrated on a Crystal Oscillator with Rubidium Clock Reference
Qibin Zheng, Kang Xu, Jiacheng Yang et al. (+4 more)
This article proposes a novel frequency-locking method based on frequency-domain unbiased phase estimation (FDUPE) for high-precision frequency control. By performing weighted recombination of the acquired data followed by
Fourier-transform processing, the phase at the center of the data segment can be estimated without bias, making the method suitable for frequency-locking applications. The principle of the proposed method is analyzed, and an electronic prototype is developed to experimentally validate its feasibility. In the prototype, analog-to-digital converters (ADCs) are used for signal digitization, and a field-programmable gate array (FPGA) is used to implement the FDUPE
algorithm. A digital proportional-integral-derivative (PID) controller is also implemented on the FPGA to provide feedback for accurate frequency locking. In the experiment, a (10~\mathrm{MHz}) voltage-controlled oscillator (VCO) with a free-running Allan deviation of (1 \times 10^{-9}) at (1~\mathrm{s}) is used as the device under test (DUT), while a rubidium atomic clock with an Allan deviation of (2 \times 10^{-11}) at (1~\mathrm{s}) serves as the high-stability reference source. Experimental results show that the proposed system achieves excellent locking performance, reducing the standard deviation of frequency fluctuations from (12.75~\mathrm{mHz}) root-mean-square (rms) in the free-running state to (0.88~\mu\mathrm{Hz}) rms after locking. Correspondingly, the Allan deviation at (10~\mathrm{s}) is reduced from (9.6 \times 10^{-10}) to (1.45 \times 10^{-14}), representing a five-order-of-magnitude improvement in frequency stability.
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All authors Qibin Zheng, Kang Xu, Jiacheng Yang, Liguo Zhou, Li Ding, Xianfeng Jiang, Zhaohui Bu
Instrumentation and Detectors
Optimized filtering for pulse-shape based pile-up rejection applied to $0\nu\beta\beta$ search with $^{100}$Mo
V. Berest, M. Buchynska, P. Carniti et al. (+13 more)
Pile-up events, arising from the partial or complete temporal overlap of distinct signals, represent a major challenge in many areas of experimental physics where rare or low-rate processes are targeted. If not properly identified, pile-up can distort reconstructed observables, degrade energy resolution, and generate backgrounds that mimic genuine events of interest. This work presents an
algorithm to obtain an optimized digital filter for the discrimination of pile-up events for detectors with known signal response and stationary noise power spectral density. It is developed in the context of the search for neutrinoless double beta decay with cryogenic Li$_{2}$$^{100}$MoO$_4$ detectors like CUPID, where pile-up induced background from $^{100}$Mo $2\nu\beta\beta$ is expected to be the leading background contribution. For this application, the new filter discriminant reduces the pile-up induced background (at 90% efficiency) by 31%, compared to an analysis with a reference method previously presented in Eur. Phys. J. C 83(5), 373 (2023). While the discussion is grounded in cryogenic calorimetric detectors, the concepts and methods described are broadly applicable to a wide class of detector technologies and experimental contexts.
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All authors V. Berest, M. Buchynska, P. Carniti, A. Giuliani, C. Gotti, H. Khalife, P. Loaiza, P. de Marcillac, C. Nones, M. Pageot, E. Olivieri, G. Pessina, D. V. Poda, J. A. Scarpaci, B. Schmidt, A. S. Zolotarova
Physics and Society · Cross-listed from nlin.AO
Explosive Transitions in Complex Networks with Adaptive Competing Interactions
Umesh Kumar Verma
Adaptation plays a central role in regulating collective behavior in complex systems. We study the collective dynamics of non-identical Stuart-Landau oscillators coupled through adaptive attractive-repulsive interactions. Without adaptation, oscillators coupled with only attractive coupling exhibit a continuous transition to synchronization. However, incorporating adaptive coupling, where the interaction strength evolves based on the global state of the system, induces an explosive transition to synchronization. When both attractive and repulsive couplings are present without adaptation, the system displays a continuous transition to synchronization and an abrupt transition to oscillation death. Remarkably, when adaptation is incorporated into this competing coupling framework, the system again exhibits an abrupt transition to synchronization. Interestingly, oscillation death occurs only in the absence of adaptation and is suppressed when adaptive coupling is present. These results are robust across different network
topologies, including global, nonlocal, and scale-free networks, underscoring the versatility of adaptive mechanisms in controlling and stabilizing emergent dynamics in complex networks.
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Geophysics
Joint Analysis of Shannon and Tsallis Entropy and GRACE-FO driven Equivalent Water Height Anomalies for Pre- and Post-Rupture Monitoring: An Example of the 2023 Mw = 7.8 Kahramanmaraş Earthquake, Türkiye
Muhammed Hossein Mousavi, Hamzeh Mohammadigheymasi and Amirreza Moradi
In order to understand the variations in fault systems throughout the seismogenic cycle, mechanical states and the complexities of seismic interactions must be considered. In this study, we present a data integration framework combining a 25-year seismic catalog with Equivalent Water Height (EWH)
datasets from the GRACE-FO mission and two information-theoretic complexity measures (Shannon and Tsallis
entropy) to examine spatiotemporal changes in the East Anatolian Fault System associated with the 2023 Kahramanmaraş earthquake doublet. The pre-rupture period exhibits a systematic increase in the
entropy measures alongside a gradual decrease in EWH, suggesting a transition towards fault network criticality driven by segment fragmentation, long-range correlations, poroelastic contraction, fluid migration, and progressive stress accumulation. During the co-seismic phase, we observe an abrupt increase in
entropy with a corresponding negative shift in EWH. In the post-seismic period, the persistence of elevated
entropy and EWH anomalies indicates that the fault system remains in a non-
equilibrium state dominated by aftershock clustering, fault zone damage, permeability changes, and viscoelastic relaxation. Additionally, structured computational workflows detailing these joint methodologies are provided via the Seismic
Entropy Analysis (
Algorithm 1) and the Relationship Between Tsallis q and Gutenberg-Richter b-value (
Algorithm 2) pseudo-codes, facilitating the direct reproduction and regeneration of all results.
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Optics
Dual Line Coherent Detection
Nelson Castro, Yiming Li, Mohammed Patel et al. (+3 more)
We experimentally demonstrate dual-line coherent detection using an optical frequency comb local oscillator, enabling large frequency offset tolerance with minimal additional signal processing. The proposed method achieves 200 GHz offset tolerance for 400 Gbit/s signals with low penalty, supporting uncooled, low-cost coherent transceivers.
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All authors Nelson Castro, Yiming Li, Mohammed Patel, Frank Smyth, Sergei Turitsyn, Andrew Ellis
Physics and Society
Demand-agnostic assessment of on-demand pooled transit services
Olha Shulika, Hanna Vasiutina, Michał Bujak et al. (+2 more)
This study proposes a method to assess the potential of pooled on-demand transit feeder services in urban areas where demand is not yet known. We introduce the fraction of demand, reflecting the probability that a resident will use the service. Demand is generated on the distribution of residents address points at varying demand fraction levels. Through simulations, we match travellers into pooled rides and evaluate the service potential using three performance indicators (KPIs). We observe how these KPIs change with varying demand fractions and identify the most promising hub for each area. By setting KPI thresholds, we select the optimal combination of area and hub that meets these thresholds at the lowest demand fraction. This approach provides municipalities with a structured tool for pre-deployment evaluation, helping them choose the most suitable areas for launching new services despite the absence of exact demand data. We illustrate its application through a case study in Krakow, ranking 12 pre-selected areas for feeder service deployment.
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All authors Olha Shulika, Hanna Vasiutina, Michał Bujak, Farnoud Ghasemi, Rafał Kucharski
Atomic Physics · Cross-listed from cond-mat.mtrl-sci
Hydrogen s-electrons as the origin of crystal magnetism beyond spin-orbit coupling
Baiqiang Liu, Zhen Gong, Rui Liu et al. (+3 more)
Magnetism has long been attributed to localized d, f, and even p electrons with strong correlations, whereas s electrons exemplified by hydrogen are reactive and tend to have their
spins quenched, making s-electron-derived magnetism and long-range ordered
magnetic crystals seem unattainable. Here we report a low-Z
ferromagnetic crystal H13@(BN)12 using first-principles calculations, where thirteen hydrogen atoms are encapsulated within a (BN)12 cage and magnetism originates from the 1s electron of the central hydrogen atom. The
crystal remains stable under ambient pressure owing to chemical precompression. Notably, the central hydrogen atom retains a
magnetic moment of 1 {\mu}B, with long-range
magnetic order established through multicenter bonding within the H13 aggregate and the intercell B-B network, while the zero orbital angular momentum of s electrons renders
spin-orbit coupling (SOC) negligible as expected. Electronic structure analyses reveal that the large cavity and central negative electrostatic potential of the (BN)12 cage localize the hydrogen 1s electron, preventing
spin quenching. Interestingly, under 16 GPa compression, the system transforms into a nonmagnetic metallic state driven by delocalized electrons of the central hydrogen atom. This study opens a pathway for constructing s-electron-driven
magnetic materials and lays the foundation for developing low-energy consumption
magnetic devices without SOC.
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All authors Baiqiang Liu, Zhen Gong, Rui Liu, Siyang Liu, Yue Feng, Zhigang Wang
Biological Physics · Cross-listed from q-bio.CB
A nonlinear theory for chemotactic fronts of mixed populations
Giulia L. Celora, Marjorie Watts, Carles Falcó et al. (+1 more)
Collective migration of heterogeneous
cell populations is central to many biological and physiological processes, including development and immune response. Recent experimental and theoretical advances have shown how asymmetric interactions with self-generated chemical gradients shape the spatial distribution of distinct
cell types within migrating collectives. However, the principles governing robust spatial organisation of heterogeneous
cell populations remain poorly understood. Here, we use asymptotic analysis to systematically derive a nonlinear analytical theory for heterogeneous
cell collectives guided by self-generated chemotaxis. Our theory disentangles how heterogeneity in
cell diffusivity, chemoattractant consumption, and chemotactic sensitivity shape the density profiles of migrating heterogeneous collectives, revealing four distinct dynamical behaviours that together capture all possible regimes. We calibrate our framework to experimental data on the co-migration of dendritic and T
cells. We predict that this system operates in a parameter regime that balances intercellular mixing with T-
cell localisation at the leading front of the migrating collective. Our theory reveals that this behaviour is enabled by intermediate long-range chemoattractant signalling generated through strong chemoattractant consumption by dendritic
cells. Overall, our framework provides general principles for understanding how non-reciprocal chemical interactions shape robust collective migration in heterogeneous
cell populations.
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All authors Giulia L. Celora, Marjorie Watts, Carles Falcó, Mohit P. Dalwadi
Applied Physics · Cross-listed from cond-mat.mes-hall
Higher-order topological metasurface based on split-ring resonators with dipole-quadrupole couplings
Alina D. Rozenblit and Nikita A. Olekhno
Photonic higher-order topological
insulators (HOTI) are characterized by a hierarchy of topologically-protected states with different dimensionalities, making them especially interesting for potential applications that combine strong localization of electromagnetic fields and their robust waveguiding. However, their practical implementation often requires expensive processing techniques and is limited by accessible material parameters. In this paper, we demonstrate that a
radio-frequency photonic HOTI can be implemented as a metasurface composed of split-ring resonators with couplings between dipole and quadrupole modes. We verify, by numerical simulations and experimentally at frequencies of 1.5-1.7 GHz, that a proposed metasurface supports corner- and edge-localized states. Our results reveal a scalable and easily reconfigurable GHz-range platform that employs printed
circuit board technology, thus making crucial steps required for further experimental studies of photonic HOTI and the development of their microwave applications.
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Atomic Physics
Creating squeezed and non-classical collective motional many-body states through stroboscopic Rydberg dressing
Roman Wußler, Chris Nill, Sylvain de Léséleuc et al. (+2 more)
Realizing conditional
quantum operations, e.g.,
quantum gates, for
quantum computing and simulation requires controlled interactions between particles. Often, these interactions depend on the interparticle distance, and accordingly, an uncertainty of the relative particle position may translate into gate infidelities. We consider here a
quantum computing platform based on an array of neutral atoms and present a method that allows to reduce the uncertainty of all interatomic distances. Our approach exploits the coupling between atomic motion and stroboscopically excited atomic Rydberg states. It allows to collectively squeeze the modes corresponding to interatomic displacements, thereby reducing distance fluctuations down to a fraction of the motional
vacuum state. Furthermore, the method permits the creation of non-classical states with substantial Wigner negativity. These correlated states may allow reducing motional decoherence, increasing gate fidelity, and potentially yield a resource for
quantum-enhanced metrology.
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All authors Roman Wußler, Chris Nill, Sylvain de Léséleuc, Christian Groß, Igor Lesanovsky
Space Physics
High-energy Particle Transport in Three-dimensional Anisotropic Turbulent Magnetic Fields
Daniela Maci, Rony Keppens and Fabio Bacchini
The understanding and modeling of high-energy particles transport in turbulent
magnetic fields is an important open question in space- and astrophysics. The multiscale, nonlinear nature of
turbulence, and the high variability of
turbulence properties across different environments, make it particularly challenging to reach a full understanding of the interactions between particles and turbulent fluctuations. Using synthetic, realistically looking turbulent
magnetic field realizations generated by the BxC toolkit, we investigate how the scattering of particles is affected by anisotropic fluctuations in strongly turbulent fields. We find evidence that, in the absence of a uniform background or guide
magnetic field, the scattering process is not governed by the
turbulence correlation length. We then further verify this hypothesis by studying particle transport in the presence of a guide field. We find evidence of a different scattering mechanism than the usual pitch-angle
diffusion used to describe scattering in strong-guide-field settings.
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Fluid Dynamics
The magneto-Leidenfrost effect in ferrofluid droplets
Abhishek Kumar Jaiswal, Neeladri Sekhar Bera and Purbarun Dhar
The dynamic Leidenfrost effect LFE and behaviour of impinging colloidal droplets is strongly influenced by the impact and spreading paradigms. LFE actuated rebound and levitation occurs due to enhanced spreading and near-frictionless
recoil over the intervening vapour layer, providing opportunities for external field stimulus aided modulation and control of impact outcomes, and the resulting boiling-LFE behaviour.
Magnetic field modulated LFE onset, dynamics and boiling transport of stable aqueous nano Fe2O3 based ferrofluid droplets was studied using high speed imaging. The interplay between
magnetic, inertia, and viscocapillary forces on droplet spreading, magneto LFE-driven rebound conditions, residence time, and post-impact regimes was analysed using dimensionless parameters maximum spread factor, Weber number, and
magnetic Bond number. We report a purely new phenomenon, namely magneto Leidenfrost effect MLFE, wherein
magnetic field induces LFE aided onset of droplet rebound at substrate temperatures Ts below the zero-field dynamic Leidenfrost temperature LFT. The critical for the onset of MLFE decreases with increasing . Increasing the nanoparticle concentration permits the onset even at considerably lower . At elevated Ts , the residence time is noted as dependent. At much higher Ts, increasing promotes formation of radial filamentous structures, leading to complete droplet fragmentation. We also propose a theoretical framework that explains
magnetic field driven spreading enhancement and rebound, and predicts of MLFE droplets in agreement with experiments. Our findings provide valuable insights into the novel realm of field dictated LFE, and hold significant implications towards the design of frictionless, rapid colloid droplet transport systems, and targeted droplet manipulation or activation for advanced thermal management.
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Geophysics
Incorporating wave physical priors into diffusion models: A novel approach to seismic resolution enhancement
Huanhuan Tang, Shijun Cheng, Weijian Mao et al. (+2 more)
Seismic resolution enhancement remains a critical challenge in exploration geophysics, particularly when processing field data characterized by limited bandwidth, strong noise, and insufficient labeled training samples. Existing deep learning methods typically rely on supervised learning with synthetic training data, leading to distribution mismatch and poor generalization on real seismic acquisitions. To address these limitations, we develop a physics-guided self-supervised
diffusion model (PG-SSDM) that learns directly from field observations without requiring paired high-resolution labels. The proposed framework combines three key innovations. First, a self-supervised training strategy constructs learning targets by progressively filtering the observed data itself, eliminating the need for high-resolution ground truth through iterative refinement across multiple stages. Second, seismic convolution model is embedded as a hard physical constraint in both the training loss function and the reverse sampling process, ensuring that generated high-resolution outputs respect fundamental seismic wave propagation physics. Third, the probabilistic nature of
diffusion models enables uncertainty quantification, providing spatial confidence maps that identify regions where resolution enhancement may be less reliable. We validate PG-SSDM on synthetic data under various noise conditions and on a 3D post-stack field
dataset. Experimental results demonstrate that the proposed method effectively recovers thin layers and subtle structures, suppresses noise, preserves structural continuity, thereby significantly improving the resolution and interpretability of seismic data.
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All authors Huanhuan Tang, Shijun Cheng, Weijian Mao, Haoran Zhang, Yingying Zhang
Fluid Dynamics
Dynamics of a vortex column of supercritical fluid across the pseudo-boiling line
Jordi Poblador-Ibanez and Fazle Hussain
The
evolution of an axisymmetric
vortex column in a weakly compressible supercritical fluid is analysed. A thermal layer is imposed to radially stratify the fluid and uncover effects of the large fluid property variations across the pseudo-boiling line. A multi-dimensional flow solver based on a low-Mach approximation is employed. Using supercritical carbon dioxide as the fluid, we examine axisymmetric configurations at low Reynolds number with the
vortex core hotter or colder than the surrounding fluid and for different thermodynamic pressures close to the critical pressure. Vorticity
evolution depends strongly on the core temperature and ambient pressure, differing substantially from the classical Oseen solution during the thermal mixing process under highly varying fluid properties. Viscous effects dominate the vorticity
evolution. Beyond
diffusion, three additional viscous mechanisms are identified, which become significant across the pseudo-boiling line: (1) a vorticity stretching term, (2) an
alignment of vorticity and viscosity/density gradients, and (3) a vorticity source due to the interaction between the fluid swirl and the viscosity and density gradients. The first two mechanisms alter existing vorticity, while the latter injects new vorticity. In fact, the third mechanism can generate reverse vorticity, locally increasing circulation and substantially modifying the temporal
evolution of the
vortex.
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Chemical Physics
Photoinduced enhancement of chemical shift sensitivity to local vibrations
Ana Martínez Gutiérrez, Oliver Alexander, Pablo Estévez Alonso et al. (+26 more)
The advent of novel free-electron
laser sources enabling time-resolved x-ray photoelectron spectroscopy (tr-XPS) provides a unique opportunity to monitor local chemical environments in real time by measuring sub-eV shifts in core-electron binding energies. These shifts reflect the interplay between electronic excitation and
nuclear motion, an interplay that remains largely unexplored. In our combined theoretical and experimental study of fluoropyridine (C$_5$H$_4$FN), we investigate this link by monitoring the evolving chemical environment at the N and F atomic sites as the photoexcited $S_1$ state relaxes to the ground state via a conical intersection. We find that the F site responds primarily to vibrational relaxation, showing minimal sensitivity to the electronic excited state. In contrast, excitation to $S_1$ induces a measurable energy shift at the N site and significantly enhances its sensitivity to local vibrations within the ring. This behavior arises from a photoinduced redistribution of charge, which also increases the Coulomb interaction between the 1s electron at the N atom and the atomic partial charge at an adjacent C atom. This insight opens new avenues for exploring ultrafast dynamics and conical intersection pathways in more complex systems, from photostable DNA bases to light-harvesting materials.
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All authors Ana Martínez Gutiérrez, Oliver Alexander, Pablo Estévez Alonso, Lorenzo Paoloni, Terry Mullins, André Al-Haddad, Thomas M. Baumann, Rebecca Boll, Christoph Bostedt, Simon Dold, Alberto De Fanis, Gianluca Geloni, Markus Ilchen, Iyas Ismail, Björn Lautenschlager, Tommaso Mazza, Dooshaye Moonshiram, Solène Oberli, Dawei Peng, Ralph Püttner, Svitozar Serkez, Marc Simon, Florian Trinter, Sergey Usenko, Michael Meyer, Jonathan P. Marangos, Jesús González-Vázquez, Daniel E. Rivas, Antonio Picón
Chemical Physics
Constrained Optimization Algorithms for Orbital Optimization in Quantum Chemistry
Junzhe Zhang, Shuoyi Hu and Bing Gu
We present a modular constrained-orbital-optimization framework for
quantum chemistry. The formulation separates the correlated electronic-structure solver from the orbital optimizer: the solver supplies one- and two-particle reduced density
matrices, while the molecular orbitals are updated on the orthonormality-constrained Stiefel
manifold with an implicit steepest-descent
algorithm. Because the orbital optimizer only requires reduced density
matrices, MP2, CASCI, and DMRG can be treated within the same interface. For CASCI solvers, the approach is closely related to optimal-orbital full configuration interaction and CASSCF\cite{helgaker_MulticonfigurationalSelfConsistentField_2000a}, but uses a solver-independent constrained-optimization update rather than CAS-specific orbital-rotation equations. When conventional CASSCF orbital-rotation iterations converge to higher-energy local solutions, CO-CAS can recover lower-energy stationary solutions. We also introduce a modified direct inversion in the iterative subspace procedure to accelerate macro-iteration convergence and a dynamical-weighting scheme to improve state-averaged excited-state calculations. Applications to LiF, H$_2$O, and pyrazine show that orbital optimization lowers energies relative to fixed-orbital MP2, CASCI, and DMRG references while improving convergence and potential-energy-curve smoothness.
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Computational Physics
Latent Residual-Closure Fourier Neural Operator for Robust Multi-Field Solving in Particle-in-Cell Simulations
Jianhua Lyu and Linlin Zhong
Particle-in-
cell (PIC) simulations are widely used for kinetic
plasma modeling in energy applications, but their efficiency is often limited by repeated field solves on dense meshes. This work proposes a Latent Residual-Closure
Fourier Neural Operator (LRC-FNO) for robust surrogate multi-field solving in PIC simulations. Rather than treating field prediction as a purely data-driven regression task, LRC-FNO formulates PIC field solving as a two-level residual-closure problem involving source compression and source-to-field operator mapping. An autoencoder extracts compact representations of particle-deposited source fields, while a Latent Closure Refiner recovers unresolved residual structures lost during compression. A Coarse-FNO Solver captures the dominant field response, and a Residual-Closure FNO restores full-resolution corrections. The method is tested on three
benchmarks with increasing complexity: 1D linear Landau damping (LLD), 2D two-stream instability (TSI), and a 2D scrape-off layer (SOL) fusion
plasma model. In LLD and TSI, LRC-FNO better preserves charge-to-potential mapping, potential-mode
evolution, residual charge structures, and particle-field energy exchange during closed-loop PIC integration. In the SOL case, LRC-FNO achieves relative L2 errors of 0.0447 for the self-consistent potential and 0.0251 for the
magnetic vector potential in single-step prediction. More importantly, when used as a neural initial guess with 20 iterative corrections, LRC-FNO maintains strong physical consistency in extrapolated closed-loop simulations, preserving charge and current density structures over a time range close to twice the training horizon. These results demonstrate that LRC-FNO can serve as both a fast surrogate field solver and a high-quality initialization strategy for iterative PIC field solvers.
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Optics
Multipolar optical binding in focus
Ashutosh Shukla, Sneha Boby and G V Pavan Kumar
The optical binding of gold nanoparticles has conventionally been explored within the Rayleigh limit using dipole approximations. But the field is increasingly focusing on the Mie regime for particles in the 100-500 nm range, where the dipole approximation is insufficient, and a complex landscape of multipolar resonances must be considered. This can be leveraged to engineer more complex forms of optical matter. To this end, we computationally study the optical binding force landscapes experienced by a pair of AuNPs using generalized multiparticle Mie theory. We calculate the total optical binding forces and mechanical trap stiffness values ($dF_i/di$) at the specific resonance wavelengths where the electric dipole, quadrupole, or octupole modes reach their respective scattering peaks and dominate the mechanical response. We demonstrate that the plasmonic mode
symmetry greatly influences the spatial distribution of zero-force nodes and the
rigidity of the optically bound dimer. By aligning these multipolar phenomena with standard experimental configurations, this work provides a mechanical framework for programmable metafluids and reconfigurable micromachines, bridging the gap between fundamental electrodynamics and reconfigurable nanomanipulation.
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Optics
Reservoir computing based on multicore fibers
Igor Chekhovskoy, Stanislav Mitsai, Georgiy Patrin et al. (+2 more)
Photonic reservoir computing offers a hardware-efficient route to processing temporal and sequential data, but delay-based implementations often rely heavily on temporal multiplexing, where long temporal masks are required to generate a sufficiently rich reservoir state. Here we show numerically that the spatial degrees of freedom of an active multicore fiber placed inside a delayed optical feedback loop can reduce this dependence on serial temporal encoding. The input signal is encoded by temporal and spatial masks, the pump distribution across the cores controls the reservoir operating point through the core-dependent effective gain and saturation energy, and the detected core intensities serve as readout features for a single trained linear layer. The system is modeled by linearly coupled nonlinear Schrödinger equations with saturable gain and solved using a split-step
Fourier method. On the Mackey-Glass one-step-ahead prediction
benchmark, a seven-core reservoir with equal temporal masks reduces the validation normalized root mean square error from 0.5956 for the single-core baseline to 0.0651 at a modulation rate of 40 GHz. At 1 GHz, spatial-only encoding reaches an error of 0.0323 using one temporal sample per symbol and no temporal mask. These results show that an active multicore fiber can provide both parallel readout channels and a tunable nonlinear transformation, offering a route to photonic reservoirs with reduced reliance on temporal multiplexing.
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All authors Igor Chekhovskoy, Stanislav Mitsai, Georgiy Patrin, Mikhail Fedoruk, Alexey Kokhanovskiy
Fluid Dynamics
Stability of Kirigami parachutes in effectively infinite numerical domains
Gabriel D. Weymouth and Marin Lauber
Kirigami, the art of cutting flat sheets into deployable 3D structures, has recently inspired a new class of parachutes which can deploy into a naturally stable inverted canopy. However, the dynamic mechanism, fluid forces, and geometrical parameters that grant this stability have not yet been clearly identified. In this paper, we use a novel Biot-Savart far-field boundary condition to perform prescribed acceleration and free-falling simulations in effectively infinite domains, tracking the descent of a parameterized kirigami parachute. The far-field velocity is reconstructed from the interior vorticity, resulting in less than 0.1% variation in the predicted dynamics as the domain size is doubled. We first show the linear forces drop 2-5 times as the parachute is deployed due to increased permeability, whereas the moments increase due the counterbalancing effect of the increased lever-arm. Next, we find that the kirigami parachute achieves stable flight for deployment heights as small as half its radius, quickly damping out applied perturbations. For smaller deployments, the parachute tumbles due to side-slip and rotational coupling, as in falling disks. These effectively unbounded simulations identify that deployments approximately equal to the radius offer high drag forces with strong dynamic stability, providing a simple design rule for deployable parachutes.
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