Computational Physics
Feature-preserving Latent-EnKF for Data Assimilation of Flows with Shocks
Hemanth Chandravamsi, Hangchuan Hu, Ponkrshnan Thiagarajan et al. (+1 more)
The ensemble Kalman filter (EnKF) is widely adopted for sequential data assimilation, but fails for solutions with discontinuities, such as shocks in compressible flows. For ensembles with uncertainty in discontinuity location, the EnKF analysis can lose physical consistency, which can be viewed through three lenses: (i) bimodal pointwise statistics in the forecast ensemble, (ii) mixed-sign analysis weights in the affine superposition of forecast members, and (iii) spatially distributed Kalman-gain profiles that modify the state around a discontinuity rather than translating it coherently. In order to preserve flow features in the analysis state and, as such, maintain physical consistency, a feature-preserving latent-EnKF is introduced. The proposed method performs the ensemble update in a low-dimensional latent space learned by a coordinate-conditioned auto-decoder. The latent representation retains near-Gaussian ensemble statistics and provides coordinates in which flow features vary coherently across the forecast ensemble. The EnKF updates performed on the latent codes are decoded into coherent changes in the represented flow features, translating shocks through coordinate morphing rather than superposing them at displaced locations. The corresponding Kalman-gain profiles generated by the latent-EnKF exhibit an approximately step-like variation across the discontinuities, allowing the fronts to translate while preserving sharp features and monotonicity. Sod shock-tube, Mach~2 shock-cylinder, and immersed-body shape-inference tests with sparse, noisy observations demonstrate accurate recovery of shocks and contact discontinuities without spurious oscillations.
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All authors Hemanth Chandravamsi, Hangchuan Hu, Ponkrshnan Thiagarajan, Tamer A. Zaki
Optics · Cross-listed from hep-th
Localization of Chiral Electromagnetic Waves on Thick Axion Domain Walls
Nemanja Kaloper
We analyze Maxwell theory coupled to an
axion domain wall as a spectral boundary value problem. We find that a finite-width
axion domain wall generically supports a localized normalizable
chiral electromagnetic mode with linear, gapless dispersion. This mode arises from helicity-dependent coupling sourced by the
axion gradient: one polarization experiences an effective attractive potential and forms a bound state, while the opposite polarization is repelled. The existence of this
chiral surface
photon is robust over a wide regime of wall structures and
axion masses. Our result shows that
axion domain walls generically support a localized
chiral photon that has been missed in previous analyses.
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Physics and Society
A Mathematical Theory of Value: a synthesis on goal-directed agency under resource constraints
Cheng Qian
We propose that value – the quantity goal-directed
agents create, destroy, and exchange – is a lawful structural quantity in the same category as information. Following Shannon's method, we make one ruthless abstraction: value is the rate at which an
agent converts a resource into goal-progress, relative to a frame fixed by its goal. A scale-invariance axiom forces a logarithmic measure, $V=\sum_i k_i\ln e_i$; compounding of a reinvested resource forces the same form via the ergodicity argument of Peters (2019) – kin routes, a consistency check, not an over-determination. We derive a coding
theorem of value, $\Delta G \le I(X;Y)$; realized value decomposes as $G=D(q\|r)-D(q\|p)$. For populations, value is frame-relative while price is frame-independent; a fleet that pools its resource and fuses its perception inherits the ceiling $G_{\rm fleet}\le I(X;Y_{1:m})\le H(X)$ (a corollary; an earlier sum-form claim was wrong and is corrected in v5). A dynamical layer yields an is/ought asymmetry from which
alignment emerges as a control-stability condition. We test the single-frame laws on live
language models, pre-registered: perception mutual information tracks realized capability (Spearman $\rho=0.977$ over 30 model$\times$domain points); out-of-sample $\Delta G$ tracks $I(X;Y)$, shape-invariant across four task shapes ($n=42$, slope $0.953$); over-confidence is measurable dissipation. The stated continuation gate has since been run (pre-registered, frontier-model population): the coupled capacity-region prediction – growth-gap law, coalition submodularity with an XOR synergy control, joint ceiling, Kelly selection – is confirmed within its frozen bands on real
agents; the mean-field residual law $\|Vg\|/\gamma$ found no domain (populations hold no goal dispersion) and is retired to its mathematical scope. The contribution is the unification and the governance mapping that follows.
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Data Analysis and Statistics · Cross-listed from astro-ph.EP
Multifractal Signatures of Hamiltonian Chaos in Hyperion's Rotational Dynamics
S. Jaroszewicz, N. Mendez, Maria P. Beccar-Varela et al. (+1 more)
The chaotic rotation of Saturn's moon Hyperion is a paradigmatic example of
Hamiltonian chaos in a natural system. Although its tumbling motion is well established theoretically, identifying a robust observational signature of chaos from sparse and noisy astronomical time series remains a major challenge, making phase-space reconstruction techniques impractical under realistic conditions. In this work, we show that multifractal detrended fluctuation analysis (MFDFA) provides an effective alternative for detecting chaotic dynamics directly from photometric observations. Using historical ground-based light curves and synthetic
datasets, we demonstrate that the intermittency associated with chaotic tumbling produces a broad multifractal singularity spectrum. While multifractality is a known feature of
Hamiltonian chaos, we show that it can serve as a practical observational diagnostic when traditional chaos indicators fail because of sparse sampling. In particular, the multifractal spectrum remains detectable after realistic observational filtering and distinguishes chaotic tumbling from aliased regular rotation. By contrast, regular resonant rotation exhibits a significantly narrower spectrum, approaching the monofractal behavior expected for uncorrelated noise. For the observational data, we measure a broad spectral width consistent with the synthetic chaotic model, statistically distinct from surrogate
datasets, and robust against finite time-series length. These results establish multifractal scaling as a viable observational signature of
Hamiltonian chaos in sparse astronomical
datasets, bridging nonlinear dynamics and planetary photometry.
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All authors S. Jaroszewicz, N. Mendez, Maria P. Beccar-Varela, Maria Cristina Mariani
Atomic Physics · Cross-listed from cond-mat.quant-gas
Joyce Kwan, Perrin Segura, Yanfei Li et al. (+7 more)
Fractional
quantum Hall states are a cornerstone of topological physics, hosting fractionally charged quasiparticles with exotic statistics that promise to enable topologically protected
quantum information processing. Among these, the Pfaffian state introduced by Moore and Read implements a p-wave pairing structure that supports excitations with non-Abelian exchange statistics. Despite extensive study in electronic systems, direct access to its pairing structure has remained limited. Here we realize a three-particle bosonic Pfaffian state of ultracold $^{87}\mathrm{Rb}$ atoms in an optical
lattice subject to a Floquet-engineered synthetic
magnetic field. Using a
Bayesian-optimized adiabatic protocol, we prepare a state exhibiting Pfaffian pairing correlations. Site-resolved measurements of multi-point density correlations reveal a pronounced suppression of short-range three-body coincidences, reflecting the underlying pairing structure. We further probe the state's transport response through
Hall drift measurements. Our results establish a bottom-up approach to engineering non-Abelian topological order and lay the groundwork for future explorations of anyonic braiding in synthetic matter.
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All authors Joyce Kwan, Perrin Segura, Yanfei Li, Tizian Blatz, Annie Zhi, Brice Bakkali-Hassani, Annabelle Bohrdt, Martin Greiter, Fabian Grusdt, Markus Greiner
Physics and Society
Revealing Peri-Urban Dislocation through Percolation Analysis
Dr Melissa Barrientos-Trinanes, Professor Stephen Marshall and Professor Elsa Arcaute
This paper introduces peri urban dislocation as a structural condition that complements existing sprawl metrics by capturing hierarchical misalignments between inner city and peripheral areas. Whereas conventional measures emphasise density, land-use mix, or fragmentation, peri-urban dislocation reflects deeper divergences in the core periphery relational functional organisation of urban systems. We operationalise this concept using percolation analysis of street networks, revealing hierarchical patterns via clustering maps and dendrograms, providing a relational structure between urban elements. Two case studies, Valdivia, Chile, and Boston, USA, demonstrate contrasting manifestations: a structural reversal in Valdivia, where a homogeneous residential periphery dominates the hierarchical clustering process, and peri-urban voids in Boston, where isolated parcellations persist despite metropolitan consolidation. These findings position peri-urban dislocation as a structural dimension linked to sprawl yet distinct from metrics based on density or peripherality; one that may occur independently or represent a previously unidentified structural signature of sprawl. Methodologically, we apply established percolation techniques to expose this previously unarticulated structural phenomenon, enabling the detection of hierarchical misalignments within urban systems. Conceptually, we introduce peri urban dislocation as a new dimension of urban structure, helping articulate debates on sprawl and peri urbanisation through a complexity informed lens and enabling core periphery diagnostics across diverse urban contexts.
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Optics
Quantifying the Distribution of Biexciton Emission Efficiencies in Colloidal Quantum Shells
Tjom Arens, Dulanjan Harankahage, Divesh Nazar et al. (+2 more)
The efficiency of multi-
photon emission is an important characteristic of
quantum light sources. Bright multi-
photon emission is desirable for high-power lighting and
lasers, while its complete suppression is required for high-purity single-
photon generation. In colloidal
quantum emitters, multi-
photon emission can vary significantly between individual particles. Resolving this heterogeneity remains challenging with conventional particle-by-particle approaches. Here, we introduce a crosstalk-suppressed SPAD-array
photon-correlation approach for high-throughput quantification of multi-
photon emission from more than 1000 colloidal
quantum shells. By projecting two images of the same sample onto distant regions of the detector array, we avoid short-range crosstalk between detector pixels. Time gating suppresses dark-count coincidences and distinguishes individual emitters from clusters. Applying this method to
quantum shells reveals a near-Gaussian distribution of biexciton emission efficiencies, with a mean of 0.55 and an estimated intrinsic standard deviation of 0.12. Intra-batch correlations between the biexciton efficiency and the particle brightness are consistent with the volume scaling of Auger quenching. These results establish SPAD-array
photon correlation as a scalable route to resolve multi-
photon heterogeneities in nanoparticle ensembles.
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All authors Tjom Arens, Dulanjan Harankahage, Divesh Nazar, Mikhail Zamkov, Freddy T. Rabouw
Data Analysis and Statistics · Cross-listed from hep-ph
The Fundaments of Unity: ${\mathcal O}(1)$ Couplings in Quantum Field Theories
Ben Allanach
We critically examine the expectation that in a fundamental
quantum field theory, dimensionless couplings in the Lagrangian density should all be of order unity. We propose a measure to quantify the adherence of a theory to this: the spread (the ratio of the largest to the smallest of the magnitudes) of such dimensionless couplings, obtaining various closed-form results. If we take independent and identically distributed (IID) couplings to parameterise our uncertainty on the values of the order-unity couplings, the spread can be much larger than one might naively expect. For a theory with 20 IID unit normal couplings, the probability that the spread is greater than 100 is 0.29, for example. Even when the IID couplings have exponentially suppressed tails, the distribution of the spread has fat power-law tails whose amplitude grows with the number of independent couplings.
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Plasma Physics
Secondary drift-driven instabilities in the presence of a parallel-propagating electromagnetic ion cyclotron wave and cold multi-component ions
Opal Issan, Patrick Kilian, Vadim Roytershteyn et al. (+2 more)
Electromagnetic ion cyclotron (EMIC) waves are commonly observed in Earth's inner magnetosphere, particularly during geomagnetic storms driven by anisotropic ring-current
protons. While their role in radiation belt scattering of hot ions is well established, their interaction with the cold (less than 100 eV)
plasma remains less understood. This is partly due to limited magnetospheric cold ion observations, as spacecraft charging can prevent cold ions from reaching onboard instruments. It is well-known that the electric field of a parallel-propagating EMIC wave can drive inter-species perpendicular polarization drifts that excite lower-hybrid secondary instabilities. In multi-component
plasmas, these include the modified two-stream and the ion-ion cross-field instabilities. In this paper, we study the impact of such secondary instabilities on the parallel-propagating EMIC wave and multi-component
plasma via a fully kinetic particle-in-
cell simulation and linear theory. We find that the secondary waves persist even at low EMIC amplitudes, provided the cold population remains sufficiently cold. The kinetic simulation demonstrates that these secondary modes produce anisotropic heating of cold
protons and singly-charged oxygen ions, primarily in the direction perpendicular to the ambient
magnetic field and of electrons in both parallel and perpendicular directions.
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All authors Opal Issan, Patrick Kilian, Vadim Roytershteyn, Salomon Janhunen, Gian Luca Delzanno
Computational Physics · Cross-listed from cs.CE
A coupled finite element formulation for chemo-mechano-thermodynamical contact and its application to bonding and debonding
Roger A. Sauer
This work presents a finite element formulation for coupled chemo-mechano-thermodynamical large deformation contact. The formulation is based on the contact theory of Sauer et al. (2022) that contains six coupled (but separate) fields: the deformation and temperature of the two contacting bodies, as well as an interfacial bonding field and interfacial temperature. The latter is governed by the chemical and mechanical energy dissipation at the interface. Here the focus is placed on the
evolution of bonding and debonding, and how it is coupled to the mechanical and thermal contact state. Several elementary models are proposed for this based on a quadratic contact potential. The resulting contact formulation becomes very general and versatile, which is illustrated by several challenging examples. They include pressure- and gap- dependent bonding, exothermic bonding reactions, thermal hardening and thermal expansion, as well as simultaneous bonding and debonding. They are based on a monolithic finite element implementation using classical and isogeometric shape functions together with implicit time integration. Its full linearization, required for the Newton-Raphson solution method, is also provided for the six-field problem, as well as for several of its simplifications. If bonding sites are material points, the bonding variable can be condensed-out locally.
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Geophysics · Cross-listed from cs.CE
Local Stress Redistribution Controls Interactions between Hydraulic Fractures and Pre-existing Fractures
S. Shandilaya, M. Alaleeli, S.H. Kim et al. (+2 more)
Hydraulic fracture (HF) propagation in naturally fractured formations is strongly influenced by local stress states near pre-existing natural fractures (NFs). The role of NF-induced shear deformation and stress redistribution in controlling HF trajectories remains poorly characterized. This study investigates how NF-induced stress redistribution governs HF-NF interactions through coupled laboratory experiments and poroelastic extended finite element simulations on intact and pre-fractured PMMA specimens under plane-strain conditions. Digital image correlation provides full-field measurements of displacement and strain
evolution during mechanical loading and hydraulic fracturing. Under fixed-base, lateral confinement, and vertical compression boundary conditions, inclined NFs induce asymmetric stress redistribution and shear deformation, generating distinct local stress states prior to fluid injection. The results demonstrate that the HF trajectory is governed by the sign and spatial distribution of shear stress and shear strain components generated by NF orientation relative to the far-field maximum principal stress. Shear deformation that promotes compressive stress development adjacent to the NF causes the HF to deflect away, whereas shear deformation that reduces the effective normal stress along the NF promotes fracture attraction and linkage. Corresponding numerical reproduction of HF
curvature in pre-fractured specimens requires mixed-mode (Mode I-II) fracture energy release criteria, while the intact specimen propagates in pure Mode I. Overall, the findings reveal a transition from tensile opening to shear-assisted mixed-mode propagation as local stress states evolve due to the presence of NFs, providing a mechanistic basis for predicting and controlling fracture trajectories in subsurface stimulation and storage applications.
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All authors S. Shandilaya, M. Alaleeli, S.H. Kim, M. Mobasher, S. Roshankhah
Chemical Physics
Transferable Machine Learning of Electronic Hamiltonians with Superposition-of-Atomic-Potentials Features
Chaoqun Zhang, Christian Venturella, Enzhi Chen et al. (+1 more)
Machine learning (ML) of electronic
Hamiltonians offers a unified route to electronic wave functions and physical observables. We introduce a
Hamiltonian learning framework built on electronic features derived from the superposition-of-atomic-potentials (SAP) approximation, an efficient self-consistent-field initial guess that captures essential electron-electron screening. SAP quantities define a
symmetry-adapted intrinsic atomic orbital learning basis and provide physics-informed inputs to an orbital-based graph neural network that predicts converged Kohn-Sham Fock
matrices. To extend the approach to larger basis sets, we further develop a downfolding scheme that predicts large-basis electronic structure from minimal-basis features. On the QM9
dataset, the model accurately reproduces frontier and core orbital energies, dipole moments, and the full density of states. For organic charge-transport materials, it yields accurate intermolecular transfer integrals for benzene, tetracyanoquinodimethane (TCNQ), and tetrathiafulvalene (TTF) dimers, and transfers to unseen substituted-benzene heterodimers with a mean absolute error of 4.8 meV. These results establish SAP-based ML of electronic
Hamiltonians as a transferable and scalable tool for high-throughput electronic-structure prediction.
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All authors Chaoqun Zhang, Christian Venturella, Enzhi Chen, Tianyu Zhu
Atomic Physics
Photon Cycling and Laser Cooling of an Asymmetric Top Molecule
Grace K. Li, Giseok Lee, Jack Mango et al. (+8 more)
We realize two-dimensional magnetically-assisted Sisyphus
laser cooling of an asymmetric top molecule (ATM), calcium monoamide (CaNH$_2$). Vibrational state closure is achieved with $41.1 \pm 6.3$
photons scatters using optical pumping of the $X[3_1]$ state.
Photon-cycling measurements show good agreement with branching ratios determined by dispersed fluorescence spectroscopy. Rotational closure is maintained by driving the $X[1_{11}] \to A [0_{00}]$ transition. The observed absence of additional state leakage channels broadens the scope of molecular
laser cooling to include ATMs, which are the most general
geometric class of molecules and possess the richest internal structure. Future applications of
quantum controlled ATMs include new
quantum information platforms and searches for physics beyond the Standard Model.
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All authors Grace K. Li, Giseok Lee, Jack Mango, Hana Lampson, YongWoong Lee, Winston Wang, Avikar Periwal, Nathaniel B. Vilas, Alexander Frenett, Loïc Anderegg, John M. Doyle
Plasma Physics
Mixed Hermite-Legendre spectral method for kinetic plasma simulations
Opal Issan, Gian Luca Delzanno and Vadim Roytershteyn
Kinetic collisionless
plasma equations are commonly solved via spectral methods in velocity space. The most commonly used spectral method is based on Hermite
polynomials with a Maxwellian weight, as this basis efficiently represents near-Maxwellian distributions with relatively few degrees of freedom. An alternative approach uses Legendre
polynomials, which are better suited for resolving strongly non-Maxwellian features. In this paper, we propose a mixed method that combines the Hermite and Legendre expansions. The mixed method is particularly advantageous for problems in which non-Maxwellian features are localized in velocity space, such as beams and plateaus. We demonstrate analytically and numerically that the mixed method conserves total mass, momentum, and energy by imposing certain constraints. The numerical results show that, for the same number of degrees of freedom, the proposed mixed method can achieve improved accuracy in comparison to the individual Hermite or Legendre methods, while maintaining comparable computational cost.
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Fluid Dynamics
Laser-Liquid Interaction in Laser-Induced Forward Transfer (LIFT) Printing: A Multiscale Perspective on Bubble Dynamics and Material Ejection
Shuqi Zhou, Abdol Hadi Mokarizadeh and Ben Xu
Laser-induced forward transfer (LIFT) is a nozzle-free
laser-assisted printing method that provides an advanced manufacturing route for spatially selective deposition of functional inks, nanoparticle suspensions,
polymers, hydrogels, biological materials, and other difficult-to-nozzle formulations. The apparent simplicity of LIFT, however, conceals a strongly coupled
laser-
liquid interaction.
Laser energy is absorbed within a confined donor architecture, converted into thermal and
plasma responses, and then transformed into bubble-mediated motion of the donor material. The cavitation bubble provides the transient mechanical bridge between optical energy deposition and the hydrodynamic ejection process. This chapter presents LIFT from a multiscale perspective centered on bubble dynamics and material ejection. It first reviews major LIFT donor architectures. Then, it examines how donor ribbon design, absorbing-layer properties,
laser parameters, material rheology, control bubble inception/growth, jet formation, droplet breakup, and final deposition. Modeling approaches are discussed as tools for connecting experimental observations across time and length scales, ranging from reduced-order estimates to interface-resolving simulations and data-driven process maps. As one illustrative mechanistic example, thermal-only,
plasma-mediated, and coupled
plasma-thermal-thermoelastic frameworks for early-stage bubble inception are briefly compared to show how different inception assumptions can provide initial conditions for downstream bubble growth and jetting models. This chapter concludes by identifying opportunities for bubble-aware donor design, time-resolved diagnostics,
benchmark datasets, and predictive LIFT process maps based on intermediate bubble and jet observables.
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Optics
Deterministic Single-Photon Emitter Arrays in Hexagonal Boron Nitride by Carbon-Assisted Focused Ion Beam Engineering
Mangababu Akkanaboina, Rohit Kumar, Brijesh Kumar et al. (+4 more)
The realization of on-chip photonic
circuits requires scalable and deterministic single-
photon emitters (SPEs) at room temperature, which remain a challenge in van der Waals materials. In this work, we report a novel three-step fabrication process for the generation of spatially controlled SPE arrays in hexagonal boron nitride (hBN). The process comprises site-selective gallium (Ga) focused ion beam milling, nanoscale conformal carbon deposition over the patterned regions, and subsequent thermal annealing. The synergistic combination of these steps resulted in a site-correlated emitter yield of ($\sim 89\%$) across 100 fabrication sites. Second-order autocorrelation measurements revealed pronounced three-level emitter dynamics where the best emitters exhibited high purity ($g^{(2)}(0)=0.15 \pm 0.09$).To the best of our knowledge, this is the first lithography-free, direct-write approach combining Ga-ion milling, selective carbon engineering, and thermal annealing to deterministically generate \hBN{} \SPE{}s. The reproducibility of the method is validated across multiple independently fabricated samples. These results establish a scalable, lithography-free pathway toward on-demand SPE arrays relevant to integrated
quantum photonics.
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All authors Mangababu Akkanaboina, Rohit Kumar, Brijesh Kumar, Hrushikesh Gawali, Parul Sharma, Ikshvaku Shyam, Anshuman Kumar
Fluid Dynamics
Effect of Additively Manufactured Wall Lattice Structures on Flashback Limits in a Hydrogen Jet Flame Combustor
Alexander Jaeschke, Thomas Ludwig Kaiser, Lukas Melzig et al. (+3 more)
This study investigated how additively manufactured nozzles with body-centered cubic
lattice structures reduce the flame flashback propensity in a hydrogen jet flame burner. Five different configurations of a jet flame combustor were investigated, with a focus on mixing duct walls incorporating porous media. The nozzles were manufactured by the powder bed fusion of metals using a
laser beam process. The
lattice parameters were varied by the volume fraction and the strut diameter. For the experiments, pure hydrogen was used as fuel under atmospheric conditions at various equivalence ratios and Reynolds numbers of 9,000 - 12,000. Flow field measurements, flame imaging, and spectral proper orthogonal decomposition of the flame dynamics were employed to identify possible transition mechanisms from a stable operation to flashback. The flow fields and the flame shapes showed only minor effects from wall modifications, preserving general flow characteristics across configurations. The flow dynamics in the combustion chamber were dominated by large-scale coherent structures in the shear layer, specifically Kelvin-Helmholtz instabilities. The results demonstrated that the nozzle with the coarsest porous wall structure significantly improved the flashback resistance compared to a nozzle with a solid wall. It is concluded that the primary mitigation mechanism was a cooling effect by unburnt mixture flowing through the porous media. The findings confirmed that the integration of
lattice structures through additive manufacturing provides a viable strategy for hydrogen flashback mitigation by manipulating the coupled interaction between the flame and the thermal conditions of the wall.
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All authors Alexander Jaeschke, Thomas Ludwig Kaiser, Lukas Melzig, Michael F. Zaeh, Kilian Oberleithner, Christian Oliver Paschereit
Chemical Physics
Coupling of diffusion and reaction in a thin cylindrical tube: Methodological drawbacks of the Fick–Jacobs approach
Sergey D. Traytak and Timofey V. Fedoseev
We investigate a problem, that describes coupling between
diffusion and reaction inside a thin circular cylindrical tube. The asymptotic solution of the posed problem is derived by means of the boundary functions method. We perform comparison of this asymptotic solution against corresponding exact solution, which revealed serious methodological drawbacks of known Fick-Jacobs reduction approach. The results obtained may be used to study a wide range of reaction-
diffusion problems, when the Fick-Jacobs method cannot be applied.
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Chemical Physics
Excited-state Properties Beyond the Excitation Energy from Orbital-Optimized Density Functional Calculations I: Dipole Moments of Rydberg States
Lorenzo Restaino, Jukka John, Diego Llorena Prieto et al. (+3 more)
Rydberg excited states are challenging to describe due to their highly diffuse character. Orbital-optimized density functional calculations typically provide more accurate values of the excitation energy of Rydberg states than time-dependent density functional theory approaches, but their performance with respect to excited-state properties such as the dipole moment remains largely unexplored as existing
benchmarks are limited to the lowest excited state. Here, orbital-optimized density functional calculations with a plane-wave basis set are used to compute the dipole moment of several Rydberg states of a set of small molecules. Plane waves provide a flexible representation of diffuse Rydberg orbitals, whereas commonly used atomic orbitals basis sets are found to yield significant discrepancies in the magnitude and orientation of the dipole moment, even when diffuse functions are included and the excitation energy agrees well with the plane-wave results. The generalized gradient approximation functional PBE used in combination with the plane-wave representation of the orbitals gives good agreement with higher-level coupled-cluster calculations performed with sufficiently diffuse basis sets, when the latter are available. The hybrid functional PBE0 further improves the results, while PBE with globally scaled explicit Perdew-Zunger self-interaction correction generally leads to larger errors and an overestimation of the dipole moment, despite restoring the correct asymptotic $-1/r$ dependence of the effective Kohn–Sham potential.
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All authors Lorenzo Restaino, Jukka John, Diego Llorena Prieto, Yorick Leonard Adrian Schmerwitz, Elvar Örn Jónsson, Gianluca Levi
Fluid Dynamics · Cross-listed from math.NA
Symmetric structure-preserving discretization of N-phase incompressible fluid mixtures with arbitrary density ratios
M.F.P. ten Eikelder and A. Brunk
Diffuse-interface models are a widely used framework for interfacial dynamics in complex fluids, in which interfaces are represented through smooth transition layers and capillary effects are encoded by a free-energy functional. For incompressible mixtures with more than two phases, however, robust computation is substantially more difficult because the numerical method should preserve the balance structure of the continuum model, maintain the saturation constraint, dissipate energy, and treat all phases symmetrically even when density ratios are arbitrary. Existing structure-preserving methods are largely developed for binary flows or for formulations that distinguish a reference phase, so a genuinely symmetric N-phase discretization remains lacking. The practical problem is therefore to construct a fully-discrete method for N-phase incompressible Navier–Stokes–Cahn–Hilliard mixture models that retains the key thermodynamic and conservation properties of the continuum equations for arbitrary density ratios. Here we propose a symmetric fully-discrete method for the N-phase incompressible Navier–Stokes–Cahn–Hilliard mixture model with arbitrary density ratios. The method yields a fully-discrete problem in which every solution satisfies exact phase volume conservation, phase mass conservation, total volume conservation, total mass conservation, and a discrete energy-dissipation law. In addition, if the volume-saturation constraint holds for the initial data, then it is preserved at every time step. We numerically verify these structure-preserving properties and demonstrate the robustness of the method in representative multiphase flow problems. The resulting scheme provides a computational framework for incompressible N-phase mixture flows with complex interfacial dynamics and arbitrary density contrasts.
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Optics
On-chip measurement of the modal Stokes-Gell-Mann parameters for partially coherent three-mode light
Amin Hashemi, Abbas Shiri, Bahaa E. A. Saleh et al. (+2 more)
The Stokes parameters are three real parameters that completely characterize partially coherent optical fields spanned by two modes – whether a pair of polarization or spatial modes – and their use is thus ubiquitous in optics. Because the Stokes parameters are defined through an expansion of the $2\times2$ coherence
matrix in terms of the Pauli
matrices, they cannot be applied to optical fields comprising three modes, which are described by a $3\times3$ coherence
matrix. Examples of such fields include the polarization of non-paraxial fields (spanned by three orthogonal polarization modes), and fields comprising three spatial or temporal modes. It has long been theorized that the $3\times3$ Gell-Mann
matrices – developed in high-energy particle physics – can serve as a basis for $3\times3$ optical coherence
matrices, with 8~expansion coefficients known as the Stokes-Gell-Mann (SGM) parameters, but the measurement procedure is daunting, and the SGM parameters have not been measured directly to date in optics. Here we present the first measurements of the SGM parameters for partially coherent three-mode light in a photonic integrated platform comprising a hexagonal mesh of Mach-Zehnder interferometers. Measuring the SGM parameters on chip, from which we reconstruct the $3\times3$ coherence
matrix facilitates exploring the full space of iso-
entropy fields that can be inter-converted into each other unitarily, and those that share the same value of
entropy and yet cannot be inter-converted unitarily. These results pave the way to utilizing multimode partially coherent light in applications involving optical communications, sensing, and information processing.
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All authors Amin Hashemi, Abbas Shiri, Bahaa E. A. Saleh, Andrea Blanco-Redondo, Ayman F. Abouraddy
Optics · Cross-listed from quant-ph
On-Chip Quantum Randomness Amplification
Lang Li, Yutian Wu, Giulio Chiribella et al. (+1 more)
Randomness amplification, the task of extracting uniform private bits from biased seeds that may be partly known by a malicious third party, is of central importance in cryptography. The highest security in this task is provided by a class of
quantum protocols known as device-independent, which however are challenging to integrate into scalable devices. Semi-device-independent (SDI) protocols are a promising alternative that guarantees security under few natural assumptions, such as bounds on the amount of energy used by the devices. Here, we provide the first demonstration of SDI randomness amplification on an integrated silicon photonic chip, achieving a throughput rate of 20 Mbps suitable for practical applications. This rate is achieved through a novel technique for SDI
entropy certification, which delivers strictly tighter von Neumann
entropy bounds compared to existing methods and remains valid even if the preparation and measurement devices share
quantum correlations. Overall, the methods developed in this work enable the integration of SDI technology into portable telecom devices, opening up a new generation of
quantum cryptographic hardware.
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All authors Lang Li, Yutian Wu, Giulio Chiribella, Ravishankar Ramanathan
Optics
Fabricating fiber cavity mirror substrates compatible with high coupling efficiency
Michael Caouette-Mansour, Thomas J. Clark, Valeria Mosso Tsedilkina et al. (+1 more)
Fiber optical cavities offer small mode volumes and correspondingly strong light-matter interactions in an open Fabry-Perot geometry. However, existing fabrication techniques do not reliably produce substrates with surface profiles amenable to high mode matching between the cavity mode and fiber core, thereby limiting the achievable collection efficiency. Here we present a technique to fabricate fiber mirror substrates while using $\textit{in situ}$ reflectometry to constrain the achievable mode matching prior to coating. By measuring the back-reflection from freshly cleaved fiber tips, we pre-select 138 fibers compatible with 96.5-99.5% mode matching, and after a single CO$_2$
laser ablation pulse, these fibers remained compatible with 95.3-99.2%. This simple technique provides rapid feedback during each stage of substrate fabrication, greatly enhancing the yield of viable fiber mirror substrates prior to (expensive) coating runs.
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All authors Michael Caouette-Mansour, Thomas J. Clark, Valeria Mosso Tsedilkina, Jack C. Sankey
Fluid Dynamics
Adaptive, efficient, and scalable water wave modeling with dispersive hyperbolic systems
Carlos Muñoz-Moncayo and David I. Ketcheson
Accurate modeling of tsunamis (such as those generated by landslides) requires capturing both wave dispersion in the deep ocean and wave breaking near the shore. The shallow water equations are often preferred for working with tsunamis, but neglect dispersion and may be inaccurate in scenarios where dispersive effects are significant. In this work, we develop an approach that seeks to incorporate the best aspects of both
hyperbolic and dispersive models by combining either of two
hyperbolic reformulations of the Serre-Green-Naghdi equations away from the shore with the non-dispersive shallow water equations near the shore. The model is discretized and implemented within the GeoClaw software, and incorporates adaptive mesh refinement as well as shared-
memory parallelism. We validate it through comparison with
benchmarks and real tsunami data. The results and performance compare favorably with the existing dispersive water wave solvers, including a speedup of about 2x relative to GeoClaw's existing dispersive solver for a large-scale tsunami simulation.
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Computational Physics
fitPALSpectra: Python fitting of positron annihilation lifetime spectra
Georgios E. Pavlou
Positron annihilation lifetime spectroscopy (PALS) spectra are commonly analyzed by fitting multi-exponential lifetime models convoluted with the detector resolution function. In practice, this inverse problem is sensitive to initial parameter choices, parameter bounds, source corrections, and correlations between lifetime and intensity parameters. This paper presents fitPALSpectra, an open-source Python workflow for configurable PALS spectrum simulation, fitting, visualization, and reporting. The implementation uses an analytically integrated exponential–Gaussian response model, configurable source and sample components, constrained optimization, optional least-squares refinement, and machine-readable output of fit results, correlation
matrices, and fitted curves. Validation on fully synthetic spectra with known ground-truth parameters shows accurate recovery of the simulated lifetimes, intensities, detector full width at half maximum,
prompt shift, and background.
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Atmospheric and Oceanic Physics
The TEAMx Observational Campaign
Manuela Lehner, Claudia Acquistapace, Marco Arpagaus et al. (+44 more)
As part of the international research programme TEAMx (multi-scale transport and exchange processes in the atmosphere over mountains - programme and experiment) a one-year long measurement campaign, the TEAMx Observational Campaign (TOC), was conducted between 2024 and 2025 in a north-south transect through the Alps. Building on the dense operational measurement network in the Alps, the TOC was designed to collect long-term atmospheric observations over the highly complex Alpine terrain. During two six-week long Extended Observational Periods, more than 40 research institutions came together to instrument about 30 sites in the four target areas of the TEAMx domain and study different transport processes, from
gravity waves to orographic convection, thermally driven flows, and turbulent exchange. In addition to a suite of ground-based in-situ and remote-sensing instruments, observational activities included airborne measurements with up to three research aircraft and multiple UAS. This paper gives an overview of the science goals and the TOC design, together with preliminary analyses that highlight the potential of the collected
dataset.
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All authors Manuela Lehner, Claudia Acquistapace, Marco Arpagaus, Timothy P. Banyard, Francesco Barbano, Kathrin Baumann-Stanzer, Christophe Brun, Warren R. L. Cairns, Charles Chemel, Helen E. Dacre, Paolo di Girolamo, Luca di Liberto, Giorgio Doglioni, Philipp Gasch, Giacomo Gerosa, Lorenzo Giovannini, Sonja Gisinger, Alexander Gohm, Jan Handwerker, Neil P. Hindley, Stefan Kneifel, Peter Knippertz, Martin Kohler, Meinolf Kossmann, Stephen Mobbs, Andrew Orr, Andreas Platis, Ian Renfrew, Didier Ricard, Andrew Ross, Harald Saathoff, Leopold M. Schlagbauer, Stefano Serafin, Peter Sheridan, Ivana Stiperski, Nadia Vendrame, Hannes Vogelmann, Jutta Vüllers, Helen C. Ward, Clemens Wastl, Stephanie Westerhuis, Andreas Wieser, Norman Wildmann, Günther Zängl, Dino Zardi, TOC team, Mathias W. Rotach
Plasma Physics
Ionization-Induced Electrostatic Hose Instability in Electron-Beam-Sustained Plasmas
Jia-Hong Chen, Yi Yu, Jian Chen et al. (+1 more)
We report the discovery of a previously unrecognized electrostatic hose instability in electron-beam-sustained
plasmas, driven by the coupling between the electron beam centroid and the
plasma generated via the beam-impact ionization. Unlike the conventional hose instability of relativistic beams propagating in underdense
plasmas, this instability requires only ionization-capable electron beams readily produced by common emission processes and sheath acceleration, indicating broad relevance across various discharges. A linear theory is developed to predict the hosing frequency and growth rate, and particle-in-
cell/Monte Carlo simulations confirm both the onset of instability and the theoretical predictions.
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All authors Jia-Hong Chen, Yi Yu, Jian Chen, Zhi-Bin Wang
Data Analysis and Statistics · Cross-listed from stat.AP
Weibull-Stationary Stochastic Differential Equations for Conditional Long-Horizon Wind Power Forecasting
Luca Di Persio and Mehrdad Ghadiri
We present a one-month-ahead conditional probabilistic framework for wind-power
forecasting at ten-minute resolution. Monthly Weibull shape and scale parameters are estimated from serially dependent SCADA wind-speed data, corrected through a Godambe covariance, and forecast by a heteroskedastic Kalman filter on a bivariate VAR(1) state-space model. Conditional on the MMSE forecasted Weibull invariant law, we construct and compare three positive wind-speed SDE models: an Ornstein-Uhlenbeck-Weibull transform, a Fokker-Planck drift-first
diffusion, and a Fokker-Planck
diffusion-first model. The simulated wind-speed ensembles are mapped to power through a calibrated XGBoost power curve. Applied to January 2021 data from a Senvion MM92 turbine at Kelmarsh Wind Farm, the three SDE formulations are statistically indistinguishable in probabilistic accuracy, with mean CRPS values between 1.569 and 1.575 m/s. The
diffusion-first model is therefore preferred on computational grounds, reducing runtime by about a factor of seven relative to the OU-Weibull model. In the power domain, the Wasserstein distance between simulated and observed distributions is 26.1-27.6 kW, below $1.4\%$ of rated capacity, while the monthly energy-yield bias is about $-7.3\%$ for the examined month. Exceedance-probability errors remain below 1.6 percentage points over the 0-1500 kW range and about 2.2 percentage points near rated power. These quantities provide decision-relevant probabilistic inputs for downstream operational problems, rather than completed reserve, storage,
market, or fatigue-optimization decisions. Full marginalisation over the Kalman predictive law of the Weibull parameters is left as a natural extension.
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Accelerator Physics
Improvement of Heat-Treated Niobium Surface by In-situ Plasma Treatment Applied to Superconducting RF Resonator
C. Boutelaa, S. Gruszka, C. Cheney et al. (+11 more)
A specific heat treatment at 300 C, named medium-temperature baking (Mid-T baking) is applied to superconducting
radio-frequency (SRF) accelerating cavities to improve the quality factor (Qo) at medium accelerating fields (10 to 20 MV/m). This treatment is very successful when done properly as it can reduce by almost a factor of two the power dissipations in this field range. However, surface contamination can lead to the degradation of Qo instead.
Plasma-based surface treatment provides an effective approach to eliminate contaminants from the Niobium surface. In this study an insitu
plasma cleaning process with argon containing 10 % O2 was performed to remove hydrocarbons from Niobium surface. The treatment was applied before and after a heat treatment at 500 C under ultra-high
vacuum conditions (Mid-T baking). Changes in chemical speciation and
oxide layer alteration induced by
plasma processing were analyzed using insitu X-ray photoelectron spectroscopy (XPS) and exsitu scanning electron microscopy (SEM). The results show that
plasma treatment modifies the composition of Niobium
oxides, converting a Nb2O5 layer into NbO2. Furthermore, a
plasma treatment before Mid-T baking helps reduce unstable
oxides such as NbxO and significantly increases the proportion of metallic Niobium at the surface. The Niobium sample treated by
plasma prior to Mid-T baking showed a 53 % reduction in carbide formation. Moreover, the C1s component attributed to NbC bonds shifts toward lower binding energy, indicating the formation of a more metallic NbC phase. Whereas without
plasma treatment, the higher binding energy component observed after Mid T baking is consistent with Nb2C.
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All authors C. Boutelaa, S. Gruszka, C. Cheney, J. Yemane, T. Gerardin, E. Mistretta, J. Demailly, R. Laxdal, P. Kolb, J. Keir, B. Mercier, N. Prud homme, G. Sattonnay, D. Longuevergne
Geophysics
Effects of microstructural heterogeneity on the macroscopic spectrum of elastically accommodated grain-boundary sliding
Zhengxuan Li and John F. Rudge
Elastically accommodated grain-boundary sliding (EAGBS) is a plausible source of upper-mantle seismic attenuation and dispersion, yet classical theory predicts a localized Debye-like peak that is absent or only weakly expressed in dry olivine experiments. Here we test whether microstructural heterogeneity can explain this discrepancy using 2-D finite-element simulations on periodic Voronoi tessellations. We find that irregular grain geometry changes the baseline EAGBS response relative to the regular hexagonal
benchmark, but increasing grain-size variance alone produces only modest changes in modulus and peak height, with little spectral broadening. In contrast, a broad distribution of grain-boundary viscosities progressively suppresses and broadens the Debye-like loss peak into a weak background spanning a wide frequency interval. This broadening arises from the superposition of many localized relaxation processes with distinct characteristic timescales and motivates a reduced-order 0-D description of the aggregate response. These results suggest that the absence of a pronounced EAGBS peak in dry olivine does not necessarily imply the absence of EAGBS mechanism itself. If grain boundaries sample a sufficiently broad viscosity distribution, the macroscopic EAGBS contribution may appear experimentally only as part of a broad attenuation background, while still remaining relevant for upper-mantle seismic attenuation and velocity dispersion.
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