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Physics Physics

physics Watch Physics

Thursday 11 December

General Physics

A Re-Examination Of Foundational Elements Of Cosmology

Lavinia Heisenberg

This paper undertakes a conceptual re-examination of several foundational elements of cosmology through the lens of spacetime symmetries. A new derivation of the Friedmann-Lemaître-Robertson-Walker metric is obtained by a careful conceptual examination of rotations and translations on generic manifolds, followed by solving the rotational and translational Killing equations, yielding both the metric and its translational generators for $k\in\{-1,0,1\}$ without any further assumptions. We then analyze how continuous symmetries are inherited by the Einstein tensor and the Hilbert energy-momentum tensor, proving two general propositions. Furthermore, we use the Maxwell and Kalb-Ramond fields to show that a homogeneous and isotropic energy-momentum tensor, in general, does not give rise to field configurations which share these symmetries. In particular, the Kalb-Ramond field we derive is significantly more general than what is usually encountered in the cosmological context. Finally, we provide a rigorous but accessible, elementary, and transparent derivation of the scalar-vector-tensor decomposition from the linearized Einstein equations. Together, these results highlight the value of multiple complementary formulations of the same cosmological physics.
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Physics and Society

Analysis of airport runway pavement reliability considering temperature variation: The case of Sao Paulo-Congonhas international airport

Felipe H. Cava, Dimas B. Ribeiro, Claudia A. Pereira et al. (+2 more)

Airport pavement design methods, such as those of the FAA, assume general climatic conditions, although regional temperature variations significantly affect pavement behavior, stress strain distribution, performance, and reliability. With global warming, evaluating how temperature influences pavement materials and resilience has become increasingly important. This study conducts a reliability analysis of pavement designed by traditional methods while incorporating seasonal temperature variation for Sao Paulo Congonhas International Airport CGH. After designing the pavement based on the airports traffic mix, a Monte Carlo Simulation was used to assess reliability under temperature changes. Results show that the cumulative damage factor from MCS is 79% lower than that obtained with the FAA method, indicating that aircraft cause less damage than predicted. The pavement could support 2.5 times more traffic at 95% reliability and 5.0 times more at 50% reliability. These findings suggest that, in Brazilian airports where fatigue governs design, FAARFIELD overestimates damage and increases construction costs, highlighting the need to calibrate design methods to local climatic conditions. Limitations include the deterministic temperature model and the exclusion of factors such as precipitation, thickness variability, and temperature dependent fatigue testing. Future work will aim to address these gaps and refine performance equations.
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All authors Felipe H. Cava, Dimas B. Ribeiro, Claudia A. Pereira, Mauro Caetano, Evandro Jose da Silva

Biological Physics

Absement: Quantitative Assessment of Metabolic Cost during Quasi-Isometric Muscle Loading

Serhii V Marchenko

Small deviations during nominally isometric loading can be separated into a sustained mean offset and fluctuations about that offset. We develop a local quasi-static model that connects these video-accessible kinematic quantities to metabolic energy. Muscle activation is eliminated through joint-moment equilibrium, and the resulting metabolic power is reduced to a smooth function of a locally invertible muscle-length coordinate. For the deviation \(x(t)=\ell(t)-\ell_0\), the reduced energy satisfies \[ \mathcal{E}_{\mathrm{met}}[\ell] = P_0T + C_1\Delta\mathcal{A}_{\ell} + C_2\mathcal{M}_{2,\ell} + R_3, \qquad |R_3| \leq KT\|x\|_{L^\infty(0,T)}^3, \] where \(\Delta\mathcal{A}_{\ell}=\int_0^T x(t)\,dt\) is signed deviation absement and \(\mathcal{M}_{2,\ell}=\int_0^T x(t)^2\,dt\) is the second raw integral moment. Equivalently, if \(\mu_\ell\) and \(\sigma_\ell^2\) are the mean and variance of the observed length deviation, then \(\Delta\mathcal{A}_{\ell}=T\mu_\ell\) and \(\mathcal{M}_{2,\ell}=T(\mu_\ell^2+\sigma_\ell^2)\). A video-based protocol can therefore estimate the required predictors without differentiating the recorded trajectory. Within the autonomous quasi-static model, periodic variation does not require a separate cycle-specific predictor: its mean contributes through absement and its dispersion through the second moment. This moment-based protocol, rather than the Taylor expansion alone, provides the experimentally testable result: residual dependence on frequency after control for the first two moments would identify the limit of the quasi-static reduction.
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Fluid Dynamics

Model for self-organized Leidenfrost rotating polygons as cnoidal waves

A. S. Carstea and A. Ludu

The remarkable appearance of self-organized regular and peaked polygonal rotating patterns in shallow Leidenfrost rings is investigated as a balance between surface tension geometry and nonlinear terms of Euler equation. Using the Boussinesq shallow convection approximation and a specialized expansion of the Laplace equation solutions, we derive a nonlinear equation that can be integrated in terms of elliptic functions. The model rigorously accounts for surface tension, the contribution of the poloidal rolling vortex, and the interplay between buoyancy-driven and thermocapillary flows. We obtain cnoidal waves solutions describing the dynamics of the inner free surface of the Leidenfrost ring, to predict polygonal patterns in liquid nitrogen. These predictions are compared with experimental observations.Additionally, we introduce a simplified model based on poloidal averaging of the capillary pressure, leading to a Korteweg-de Vries-type equation. This simplified model not only reproduces the cnoidal wave solutions but also predicts new trigonometric solutions, offering insights into the formation of peaked polygons.
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Fluid Dynamics

The role of the second normal stress difference in rod-climbing effect

Rishabh More

The Weissenberg (rod-climbing) effect, i.e., the rise of a viscoelastic fluid along a thin rotating rod, has long served as a canonical demonstration of elasticity and normal-stress differences in complex fluids. The effect is most commonly attributed to the first normal stress difference $N_{1}$, which induces tensile hoop stresses that draw fluid upward along the rod. The second normal stress difference $N_{2}$, in contrast, is often presumed negligible or dynamically unimportant. However, many polymer solutions and industrial fluids, such as suspensions, exhibit $N_{2}$ of appreciable magnitude, and modern constitutive models predict that it can significantly modify free-surface stresses and thereby the climbing behaviour. In this work, we perform high-resolution axisymmetric simulations of the Linear Phan–Thien–Tanner (LPTT) model to systematically isolate the influence of $N_{2}$ on rod climbing. We show that increasing the magnitude of $N_{2}$ progressively weakens the climbing response and ultimately reverses it, producing rod-descending once the normal-stress ratio exceeds a critical value $\psi_{0}\approx 0.25$. Larger $N_{2}$ also destabilises the flow, promoting early onset (in terms of the rotation speed) of bubble formation, subcritical Hopf oscillations, and fully asymmetric three-dimensional motion that culminates in rupture. By mapping these regimes in the $(Wi,\psi_{0})$ parameter space, where $Wi$ is the Weissenberg number, we reconcile discrepancies among perturbation theory, experiments, and numerical simulations. These results establish $N_{2}$ as a crucial control parameter governing free-surface stability in viscoelastic liquids.
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Applied Physics

Gate-controlled analog memcapacitance in LaAlO3/SrTiO3 interface-based devices

Soumen Pradhan, Victor Lopez-Richard, Igor Ricardo Filgueira e Silva et al. (+8 more)

Current memcapacitor implementations typically demand complex fabrication processes or depend on organic materials exhibiting poor environmental stability and reproducibility. Here, we demonstrate memcapacitor structures utilizing a quasi 2-dimensional electron gas, formed at the crystalline LaAlO3/SrTiO3 heterointerface, as electrodes and SiO2/SrTiO3 as dielectric layer. The observed memcapacitance originates from the charge localization in a lateral floating gate, while an applied gate voltage enables reversible tuning of the device capacitance. Furthermore, preprogrammed or erased gate biases enable controllable shifts of the capacitance hysteresis window toward positive or negative bias, leading to an enlarged capacitance gap at zero bias. A memcapacitor model developed for this system reproduces the main features of the experimental capacitance hysteresis, capturing the effects of charge fluctuations and dielectric frequency modulation within the oxide layer. The demonstrated low-voltage operation and gate tunability of oxide interface-based memcapacitors highlight their potential for power-efficient, capacitor-based neuromorphic and synaptic electronic architectures.
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All authors Soumen Pradhan, Victor Lopez-Richard, Igor Ricardo Filgueira e Silva, Fabian Hartmann, Ana Luiza Costa Silva, Leonardo K. Castelano, Merit Spring, Silke Kuhn, Michael Sing, Ralph Claessen, Sven Höfling

Chemical Physics · Cross-listed from quant-ph

Negative Marginal Densities in Mixed Quantum-Classical Liouville Dynamics

Kai Gu and Jeremy Schofield

The mixed quantum-classical Liouville equation (QCLE) provides an approximate perturbative framework for describing the dynamics of systems with coupled quantum and classical degrees of freedom of disparate thermal wavelengths. The evolution governed by the Liouville operator preserves many properties of full quantum dynamics, including the conservation of total population, energy, and purity, and has shown quantitative agreement with exact quantum results for the expectation values of many observables where direct comparisons are feasible. However, since the QCLE density matrix operator is obtained from the partial Wigner transform of the full quantum density matrix, its matrix elements can have negative values, implying that the diagonal matrix elements behave as pseudo-densities rather than densities of classical phase space. Here, we compare phase-space distributions generated by exact quantum dynamics with those produced by QCLE evolution from pure quantum initial states. We show that resonance effects in the off-diagonal matrix elements differ qualitatively, particularly for low-energy states. Furthermore, numerical and analytical results for low-dimensional models reveal that the QCLE can violate the positivity of marginal phase-space densities, a property that should hold at all times for any physical system. A perturbative analysis of a model system confirms that such violations arise generically. We also show that the violations of positivity of the marginal densities vanish as the initial energy of the system increases relative to the energy gap between subsystem states. These findings suggest that a negativity index, quantifying deviations from positivity, may provide a useful metric for assessing the validity of mixed quantum\textendash{}classical descriptions.
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Optics

Bismuth nanogratings with narrow plasmon resonances for dynamic polarized color generation and colorimetric sensing

Fernando Chacón-Sánchez, Fátima Cabello, Marina García Pardo et al. (+3 more)

Bismuth nanostructures are appealing for sustainable color generation and sunlight harvesting, thanks to their non-toxicity and their tunable visible-to-near infrared interband plasmon resonances. However, owing to their broad and polarization-insensitive spectral features, the nanostructures reported so far displayed a limited color tunability and were lacking other functionalities such as sensing. Herein, we report bismuth nanogratings with polarization-sensitive and narrow plasmon resonances (Q > 10). They were fabricated on the $cm^2$ scale following a lithography-free approach: conformal pulsed laser deposition of bismuth onto both the reflective and transparent nanostructured layers of DVDs. We characterized their specular reflectance for different orientations of the plane of incidence, angles of incidence, and polarizations of light. When light is polarized in the plane perpendicular to the lines, plasmon resonances occur and shift across the visible-to-near infrared upon changing the angle of incidence. In contrast, no such resonances occur when light is polarized in the plane parallel to the lines. This results in well-contrasted, polarization-sensitive colors, which are iridescent for the former orientation of polarization, and not for the latter. Resonances strongly shift upon changing the refractive index of the surrounding medium (> 500 nm/RIU), resulting in a marked change in the plasmonic color, e.g., from green in air to red in water. This showcases the potential of these nanogratings for dynamic polarized color generation and colorimetric sensing.
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All authors Fernando Chacón-Sánchez, Fátima Cabello, Marina García Pardo, Emmanuel Haro-Poniatowski, Rosalía Serna, Johann Toudert

Fluid Dynamics

Vortices, turbulence, and center of pressure in flow over pitching swept wings

Dipan Deb, Yuanhang Zhu, Philip Gaudio et al. (+1 more)

This study examines the center of pressure (CoP) movement of rigid pitching swept wings based on prior measurements by (Zhu, Breuer, 2023}. The wings analyzed feature sweep angles of $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$, and are subjected to large amplitude sinusoidal pitching instabilities below a critical torsional spring stiffness. The CoP location is determined from time-resolved force and moment measurements, revealing minimal variation in the cross-chord direction but significant spanwise and chord-wise movement, varied by sweep angle. The trajectory of the CoP varies with sweep angle due to the evolving strength and dynamics of the leading edge and tip vortices. The Force Moment Partitioning Method (FMPM) is applied to stereo Particle Image Velocimetry (PIV) data to identify contributions from wing kinematics, vortex structures, and viscous effects. This approach elucidates the roles of leading edge and tip vortices, as well as the periodic and stochastic components of the flow field, in influencing the net forces and moments.
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All authors Dipan Deb, Yuanhang Zhu, Philip Gaudio, Kenneth Breuer

Classical Physics · Cross-listed from quant-ph

Solutions of Koopman-von Neumann equations, their superpositions, and uncertainties

Mustafa Amin and Mark A. Walton

The so-called Koopman-von Neumann (KvN) formulation brings classical mechanics to Hilbert space, but many techniques familiar from quantum mechanics remain missing. We use the gauge freedom of the KvN equation to derive separable solutions of the KvN equation, and by extension the classical Liouville equation. The canonical ensemble solution of statistical mechanics is shown to arise from separable solutions. We discuss the Hermiticity of the Liouvillian operator, and treat a case where its spectrum is discrete. Finally, we analyze an uncertainty relation between the so-called dynamical time and the Liouvillian, and argue that such a relation is natural and can be understood entirely within a classical framework.
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Atomic Physics

Neutral Barium in Solid Neon: Optical Spectroscopy and First Excited State Lifetime

Alessandro Lippi, Giovanni Carugno, Roberto Calabrese et al. (+5 more)

Matrix isolation spectroscopy enables probing atomic properties in controlled cryogenic environments. We present a spectroscopic study on neutral barium atoms embedded in a neon cryogenic crystal at 6.8 K, extending previous investigations performed in other noble gas hosts. The visible and near-infrared emission spectra were recorded under two different laser excitation schemes. First, 10-ns laser pulses at 355 nm were used to directly excite high-lying energy levels of barium, enabling the observation of fluorescence cascades. Second, a tunable continuous-wave laser operating between 700 nm and 900 nm allowed us to determine the matrix-induced shifts of barium energy levels relative to their vacuum values, as well as the inhomogeneous linewidths of the observed transitions and to perform lifetime measurements. Our results confirm multiple radiative pathways and matrix-induced relaxation channels affecting the 5d6s and 6s6p barium manifolds. Furthermore, we present the first lifetime measurement of the barium 5d6s 3D1 state in a neon crystal, yielding 0.39 \pm 0.02 s, with a predicted increase of about 10% at 2 K. The study of fluorescence and spectroscopic properties of barium isolated in neon represents an important step toward future searches for the electron electric dipole moment using barium monofluoride in neon matrices, where neutral barium atoms may act as unavoidable impurities and potential sources of background and systematic limitations.
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All authors Alessandro Lippi, Giovanni Carugno, Roberto Calabrese, Federico Chiossi, Marco Guarise, Madiha M. Makhdoom, Giuseppe Messineo, Jacopo Pazzini

Data Analysis and Statistics

Machine Learning

Javier M. Duarte, Uros Seljak and Kazu Terao

This chapter gives an overview of the core concepts of machine learning (ML) – the use of algorithms that learn from data, identify patterns, and make predictions or decisions without being explicitly programmed – that are relevant to particle physics with some examples of applications to the energy, intensity, cosmic, and accelerator frontiers.
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Instrumentation and Detectors

Experimental and Monte Carlo Simulation Studies to Investigate the Working Principle of Compact Nanodosimeters

Victor Merza, Aleksandr Bancer, Vladimir Bashkirov et al. (+9 more)

In recent years, compact nanodosimetric detectors based on ion multiplication in low-pressure gas have been developed and gained attention in the scientific community. These detectors use strong electric fields to collect and multiply positive ions produced by the incident radiation in mm-sized cell holes in dielectric materials, achieving a nm-equivalent spatial resolution of the localization of ionization events, when scaled to liquid water at unit density. Their design assumes that ion-impact ionizations of gas molecules within the cell holes dominate signal formation, yet this assumption has lacked direct physical verification. Electron emission from the cell hole walls or the cathode due to ion-impact could also contribute, requiring alternative designs to optimize efficiency. To investigate the relative importance of the possible mechanisms, a nanodosimetric detector featuring a single cell hole with a diameter of 1.5 mm in a dielectric plate was developed. Ion collection and multiplication were achieved by applying a negative high voltage to the glass cathode 0.5 mm below the cell hole, assisted by a low drift field above the plate. A grounded readout electrode with a 0.8 mm hole covers the cell hole to prevent interactions of collected ions with the hole walls. High signal yields in 1 mbar and 2 mbar propane gas were observed and indicated that ion-impact ionizations of the gas molecules could indeed be the primary mechanism for signal induction. Ion-induced secondary electron emission from the cathode was identified as another potential contribution. The compact nanodosimeter setup was further modeled with Geant4-DNA and Garfield++ for deeper insight. The results of these studies are important for understanding and developing a new class of nanodosimeters with potential applications in particle therapy, radiation protection, space dosimetry, and particle physics.
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All authors Victor Merza, Aleksandr Bancer, Vladimir Bashkirov, Ana Belchior, Beata Brzozowska, João F. Canhoto, Piotr Gasik, Jaroslaw Grzyb, Khaled Katmeh, Marcin Pietrzak, Antoni Ruciński, Reinhard Schulte

Instrumentation and Detectors

Characterization of CRYO ASIC for charge readout in the nEXO experiment

Z. Li, M. Yu, E. Angelico et al. (+141 more)

nEXO is a proposed next-generation experiment searching for the neutrinoless double beta decay of $^{136}$Xe using a tonne-scale liquid xenon (LXe) time projection chamber (TPC). To image the ionization signals from events in the liquid xenon, the detector will employ metallized fused-silica charge collection tiles instrumented with cryogenic application-specific integrated circuits (ASICs), referred to as CRYO ASIC, which are designed to operate directly in LXe to minimize input capacitance and pick-up noise. Here we present the performance of the CRYO ASIC mounted on an auxiliary printed circuit board and evaluated both in a cryogenic environmental chamber and in a dedicated LXe test stand. We demonstrate that the ASICs achieve the desired performance at liquid xenon temperatures, showing a gain stability better than 0.2% over 24-hour operation and reliable in-situ calibration using an on-chip pulser. In the LXe test stand, we show that boiling caused by the chip heat dissipation can be mitigated by operating the system above ~0.1 MPa. The in-LXe noise measured agrees with simulation, which indicates it the $150~e^-$ design requirement can be satisfied. These results establish CRYO ASIC as a viable low-noise in-LXe charge readout solution for nEXO.
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All authors Z. Li, M. Yu, E. Angelico, A. Atencio, A. Gupta, P. Knauss, A. Pena-Perez, B. G. Lenardo, P. Acharya, A. Amy, A. Anker, I. J. Arnquist, J. Bane, V. Belov, T. Bhatta, A. Bolotnikov, J. Breslin, P. A. Breur, J. P. Brodsky, E. Brown, T. Brunner, B. Burnell, E. Caden, G. F. Cao, L. Q. Cao, D. Cesmecioglu, D. Chernyak, M. Chiu, R. Collister, M. Marquis, T. Daniels, L. Darroch, R. DeVoe, M. L. di Vacri, X. Defay, Y. Y. Ding, D. Doering, M. J. Dolinski, A. Dragone, B. Eckert, A. Emara, N. Fatemighomi, W. Fairbank, B. T. Foust, D. Gallacher, N. Gallice, A. Gaur, W. Gillis, F. Girard, A. Gorham, K. Gracequist, G. Gratta, C. A. Hardy, J. Hasi, S. Hedges, M. Heffner, E. Hein, H. Hernandez Herrera, J. D. Holt, A. Iverson, X. S. Jiang, A. Karelin, D. Keblbeck, C. Kenney, I. Kotov, A. Kuchenkov, K. S. Kumar, S. Lavoie, A. Larson, M. B. Latif, K. G. Leach, D. S. Leonard, G. Lessard, K. K. H. Leung, G. Li, X. Li, C. Licciardi, R. Lindsay, R. MacLellan, S. Majidi, C. Malbrunot, B. Markovic, J. Masbou, M. Medina-Peregrina, S. Mngonyama, B. Mong, D. C. Moore, K. Ni, I. Nitu, A. Nolan, S. C. Nowicki, J. C. Nzobadila Ondze, A. Odian, J. L. Orrell, G. S. Ortega, L. Pagani, H. Peltz Smalley, A. Piepke, A. Pocar, S. Prentice, V. Radeka, E. Raguzin, R. Rai, H. Rasiwala, D. Ray, B. Reese, S. Rescia, F. Retiere, G. Richardson, V. Riot, R. Ross, L. Rota, P. C. Rowson, R. Saldanha, S. Sangiorgio, S. Sekula, T. Shetty, L. Si, F. Spadoni, V. Stekhanov, X. L. Sun, S. Thibado, T. Totev, S. Triambak, R. H. M. Tsang, O. A. Tyuka, T. Vallivilayil John, E. van Bruggen, M. Vidal, S. Viel, M. Walent, H. Wang, Q. D. Wang, M. Watts, W. Wei, M. Wehrfritz, L. J. Wen, S. Wilde, X. M. Wu, H. Xu, H. B. Yang, L. Yang, O. Zeldovich, J. Zhao

Optics

Deep diffractive optical neural networks for detecting Skyrmionic topologies of light

Hadrian Bezuidenhout, Cade Peters, Ram Kumar et al. (+2 more)

Optical Skyrmions are topological forms of structured light with the potential of an infinite encoding alphabet that is immune to disturbance. This attractive prospect is hindered by the lack of any topological detector, a challenging problem due to the non-orthogonal nature of the topological invariant (N). Here we demonstrate the first deterministic detector for Skyrmionic topologies of light using a deep diffractive optical neural network. Our network uses two independent processing channels of 5 diffractive layers each to map incoming topologies to spatially separated Gaussian channels from which N can be detected. We overcome the complexity of the training by using a spatial mode basis rather than pixels, reducing the training variables by x1000 compared to current methods. We use the detector on an input set of 81 input topologies, showing high accuracy even in the presence of significant levels of noise. Finally, to show the practical utility of the device, we transmit and receive an image encoded in a 14-level topological alphabet with no discernible cross-talk. Our work offers a new paradigm for the emergent field of diffractive optical networks and can easily be extended to other forms of optical topologies, setting a clear pathway for their deployment in real-world applications.
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All authors Hadrian Bezuidenhout, Cade Peters, Ram Kumar, Andrew Forbes, Isaac Nape

Data Analysis and Statistics · Cross-listed from quant-ph

Universal and non-universal facets of quantum critical phenomena unveiled along the Schmidt decomposition theorem

Samuel M. Soares, Lucas Squillante, Henrique S. Lima et al. (+2 more)

Critical phenomena have been extensively investigated both theoretically and experimentally in many fields, such as condensed matter physics, biology, e.g., brain criticality, and cosmology. In particular, the behaviour of response functions right at critical points (CPs) is highly topical. It turns out that in the frame of Boltzmann-Gibbs-von Neumann-Shannon approach, the extensive character of entropy breaks down at CPs. The latter implies diverging susceptibilities, which is at odds with experimental observations. Here, we investigate the influence of the spin magnitude $S$ on the quantum Grüneisen parameter $\Gamma^{0\text{K}}_{q}$ right at CPs for the 1D Ising model under a transverse magnetic field. Our findings are fourfold: $\textit{i}$) for higher $S$, $\Gamma^{0\text{K}}_{q}$ is increased, but remains finite, reflecting the enhancement of the Hilbert space dimensionality; $\textit{ii}$) the Schmidt decomposition theorem recovers the extensivity of the nonadditive $q$-entropy $S_q$ only for a $\textit{special}$ value of the entropic index $q$; $\textit{iii}$) the universality class in the frame of $S_q$ depends only on the symmetry of the system; $\textit{iv}$) we propose an experimental setup to explore finite-size effects in connection with the Hilbert space occupation at CPs. Our findings unveil both universal and non-universal aspects of quantum criticality in terms of $\Gamma^{0\text{K}}_{q}$ and $S_q$.
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All authors Samuel M. Soares, Lucas Squillante, Henrique S. Lima, Constantino Tsallis, Mariano de Souza

Space Physics

Microgravity and Near-Absolute Zero: A New Frontier in Quantum Computing Hardware

Denis Saklakov

Quantum computing qubits are notoriously fragile, requiring extreme isolation from environmental disturbances. This paper advances the hypothesis that a combination of microgravity and ultra-low temperature (near absolute zero) provides an almost "ideal" operating environment for quantum hardware. Under such conditions, gravitational perturbations, thermal noise, and vibrational disturbances are minimized, thereby significantly extending qubit coherence times and reducing error rates. We survey four leading qubit platforms - superconducting circuits, trapped ions, ultracold neutral atoms, and photonic qubits - and explain how each can benefit from a weightless, cryogenic setting. Recent experiments support this vision: Bose-Einstein condensates on the International Space Station (ISS) maintained matter-wave coherence far longer than on Earth, atomic clocks in orbit achieved record stability, and a photonic quantum computer deployed in space is demonstrating robust operation. Finally, we outline a proposed side-by-side experiment comparing identical quantum processors on the ground and in microgravity. Such a test would directly measure improvements in qubit coherence (T1, T2), gate fidelity, and readout accuracy when the influence of gravity is removed.
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Atmospheric and Oceanic Physics

Integrating Regional Ice Charts and Copernicus Sea Ice Products for Navigation Risk in Alaskan Waters

Grant Peel and Ersegun Deniz Gedikli

As climate change continues to reshape marginal ice zones in the Arctic, accurate and reliable sea ice data are critical for ensuring maritime safety. This study compares regional ice charts from the Alaska Sea Ice Program with satellite derived Copernicus sea ice concentration data to evaluate spatial and temporal discrepancies in ice representation across Alaskan waters from January 2010 to March 2025. Daily Arctic Sea Ice Program polygons were aligned with Copernicus grid points in a common UTM framework, and residuals were computed to quantify systematic differences. Results show that Copernicus consistently underestimates ice concentration relative to Arctic Sea Ice Program, particularly in nearshore and marginal ice zones affected by land-spillover and mixed-pixel effects such as those observed in Cook Inlet. Empirical Orthogonal Function analysis shows that both datasets capture the same dominant physical modes of sea ice variability, with the first mode representing the annual freeze thaw cycle and the second reflecting marginal ice-zone dynamics. To assess operational implications, vessel Automatic Identification System data were combined with Alaska Sea Ice Program ice charts using the IACS POLARIS Risk Index Outcome framework. Approximately 36 percent of AIS observations within ice affected waters corresponded to negative Risk Index Outcome values, indicating that vessels frequently operated under elevated-risk conditions. These findings demonstrate that regional charts and Copernicus provide complementary capabilities that together enable more accurate and operationally meaningful Arctic navigation and risk assessments.
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Optics

3D-printed microscope with illumination for undergraduate wave optics laboratory

S.G. Martanov, V.A. Prudkoglyad, A.A. Galiullin et al. (+2 more)

We present an educational tool, a microscope with a video camera, that can be fabricated either from a standard microscope or assembled from inexpensive, commercially available components (objectives, beam splitters, LEDs, linear stages) and 3D-printed elements. Usage of interference filters in combination with white light-emitting diode (LED) illumination enables the quantitative study of optical phenomena such as refraction, interference (e.g., Newton's rings), Fresnel and Fraunhofer diffraction. Thus, we propose an instrument that can be used to illustrate the theoretical foundations of an undergraduate optics course and beyond.
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All authors S.G. Martanov, V.A. Prudkoglyad, A.A. Galiullin, G.A. Shmakov, A.Yu. Kuntsevich

Physics Education

A Framework for Understanding the Impact of Integrating Conceptual and Quantitative Reasoning in a Quantum Optics Tutorial on Students' Conceptual Understanding

Paul D. Justice, Emily Marshman and Chandralekha Singh

We investigated the impact of incorporating quantitative reasoning for deeper sense-making in a Quantum Interactive Learning Tutorial (QuILT) on students' conceptual performance using a framework emphasizing integration of conceptual and quantitative aspects of quantum optics. In this investigation, we compared two versions of the QuILT that were developed and validated to help students learn various aspects of quantum optics using a Mach Zehnder Interferometer with single photons and polarizers. One version of the QuILT is entirely conceptual while the other version integrates quantitative and conceptual reasoning (hybrid version). Performance on conceptual questions of upper-level undergraduate and graduate students who engaged with the hybrid QuILT was compared with that of those who utilized the conceptual QuILT emphasizing the same concepts. Both versions of the QuILT focus on the same concepts, use a scaffolded approach to learning, and take advantage of research on students' difficulties in learning. The hybrid and conceptual QuILTs were used in courses for upper-level undergraduates or first-year physics graduate students in several consecutive years at the same university. The same conceptual pre-test and post-test were administered after traditional lecture-based instruction in relevant concepts and after student engaged with the QuILT, respectively. We find that the post-test performance of physics graduate students who utilized the hybrid QuILT on conceptual questions, was better than those who utilized the conceptual QuILT. For undergraduates, the results showed differences for different classes. One possible interpretation of these findings consistent with our framework is that integrating conceptual and quantitative aspects of physics in research-based tools and pedagogies should be commensurate with students' prior knowledge of physics and mathematics involved.
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Fluid Dynamics

Physics-Informed Dynamical Modeling of Extrusion-Based 3D Printing Processes

Mandana Mohammadi Looey, Marissa Loraine Scalise, Amrita Basak et al. (+1 more)

The trade-off between model fidelity and computational cost remains a central challenge in the computational modeling of extrusion-based 3D printing, particularly for real time optimization and control. Although high fidelity simulations have advanced considerably for offline analysis, dynamical modeling tailored for online, control-oriented applications is still significantly underdeveloped. In this study, we propose a reduced order dynamical flow model that captures the transient behavior of extrusion-based 3D printing. The model is grounded in physics-based principles derived from the Navier Stokes equations and further simplified through spatial averaging and input dependent parameterization. To assess its performance, the model is identified via a nonlinear least squares approach using Computational Fluid Dynamics (CFD) simulation data spanning a range of printing conditions and subsequently validated across multiple combinations of training and testing scenarios. The results demonstrate strong agreement with the CFD data within the nozzle, the nozzle substrate gap, and the deposited layer regions. Overall, the proposed reduced order model successfully captures the dominant flow dynamics of the process while maintaining a level of simplicity compatible with real time control and optimization.
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All authors Mandana Mohammadi Looey, Marissa Loraine Scalise, Amrita Basak, Satadru Dey

History and Philosophy of Physics

Ugo Amaldi, the DELPHI Collaboration and The Physics Legacy of LEP

Alessandro De Angelis

This article offers a portrait of the DELPHI experiment at CERN's Large Electron-Positron Collider (LEP) through the scientific life and leadership of Ugo Amaldi. It traces how DELPHI contributed to LEP's physics program, from precision studies at the Z pole to higher-energy running with W-pair production and increasingly ambitious Higgs searches. Along the way, it highlights Ugo Amaldi's technical and organizational innovations, especially his insistence on bold detector choices and his sustained support for young physicists and collaborative leadership. The article also recalls Ugo's influential work on the unification of forces and shows how DELPHI's technologies, software, governance structures, and data-sharing practices anticipated many features of later collider experiments and of contemporary science policy. In this sense, DELPHI's legacy is not only foundational for today's particle physics, but also a lasting and formative element of modern scientific culture.
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Medical Physics

Integrating Uncertainty Quantification into Computational Fluid Dynamics Models of Coronary Arteries Under Steady Flow

Muhammad Usman, Peter N. Castillo, Akil Narayan et al. (+1 more)

Computational models are continuously integrated in the clinical space, where they support clinicians in disease diagnosis, prognosis, and prevention strategies. While assisting in clinical space, these computational models frequently use deterministic approaches, where the inherent (aleatoric) variability of input parameters is ignored. This questions the credibility and often hinders the clinical adoption of these computational models. Therefore, in this study, we introduced uncertainty quantification in the computational fluid dynamics models of the left main coronary artery to analyze the influence of input hemodynamics parameters on wall shear stress (WSS). UncertainSCI was used, where an emulator was built using polynomial chaos expansion between the input parameters and the output quantity of interest, and the output sensitivities and statistics were directly extracted from the emulator. The uncertainty-informed framework was first applied to an analytical solution of the Navier-Stokes equation (Poiseuille flow) and then to a patient-specific model of the left main coronary artery. Different input hemodynamics parameters are considered, such as pressure, viscosity, density, velocity, and radius, whereas wall shear stress was considered as our output quantity of interest. The results suggest that velocity dominated the variability in WSS in the analytical model (~79%), whereas viscosity dominated in the patient-specific model (~59%). The results further suggest that out of all the Sobol indices interactions, unary interactions were the most dominant ones, contributing ~93.2% and ~99% for the analytical and patient-specific model, respectively. This study will enhance confidence in computational models, facilitating their adoption in the clinical space to improve decision-making for coronary artery disease diagnosis, prognosis, and therapeutic strategies.
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All authors Muhammad Usman, Peter N. Castillo, Akil Narayan, Lucas H. Timmins

Fluid Dynamics

Dynamics of motions and deformations of an arbitrary geometry flexural floe in ocean waves

Andrei Ludu

This paper develops a comprehensive mathematical framework for modeling the coupled hydroelastic dynamics of sea-ice floes of arbitrary shape and non-uniform thickness under linear ocean wave forcing. We simultaneously incorporate four dominant rigid-body motions (heave, surge, roll, pitch) and the complete spectrum of flexural deformation modes within a unified Green function formulation. The water flow is modeled using potential theory with Laplace's equation, while the floe obeys a generalized Kirchhoff-Love plate equation with spatially varying flexural rigidity. We formulate the coupled fluid-structure interaction problem through kinematic velocity-matching conditions and dynamic pressure-continuity conditions at the ice-water interface. The elastic eigenproblem with free-edge boundary conditions yields a complete orthogonal basis of deformation modes, accounting for added mass effects through modified natural frequencies. By decomposing the velocity potential into partial potentials associated with incident waves, scattered waves, rigid motions, and elastic modes, we reduce the problem to a system of Fredholm integral equations of the second kind for surface density functions on all boundary segments. The solution methodology employs single-layer potential representations with fundamental Green functions for Laplace's equation. We present explicit formulations for all boundary conditions in compact tensor form, provide asymptotic analysis for the spectrum of non-uniform thickness floes, and discuss resonance phenomena arising from the interaction between incident wave frequency and natural vibration modes.
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Atomic Physics

Rapid multi-mode trapped-ion laser cooling in a phase-stable standing wave

Zhenzhong Xing, Hamim Mahmud Rivy, Vighnesh Natarajan et al. (+3 more)

Laser cooling is fundamental to quantum computing and metrology using atomic systems. Precise control often requires cooling atoms' motional degrees of freedom to the quantum ground state, imposing operation time and architectural limitations particularly in large-scale systems. Here we demonstrate how the integrated optical control of interest for scaling trapped-ion systems additionally enables laser cooling that bypasses limitations of conventional schemes. Leveraging multi-channel integrated delivery of ultraviolet to infrared wavelengths for calcium ion control including in passively phase-stable ultraviolet standing waves (SWs), we experimentally verify a long-standing prediction by Cirac et al., realizing Doppler cooling to below the conventional Doppler limit at a SW node. We also present the first realization of ground-state cooling via electromagnetically induced transparency (EIT) using a “probe" beam delivered as a SW with atoms positioned at a node, predicted to enable multi-mode sub-recoil-limit laser cooling. We demonstrate cooling of motional modes spanning an approximately 5 MHz bandwidth from the Doppler temperature to near the ground state within 150~\textmu s, reaching $\bar n \approx 0.05$ phonon number occupancies for the target mode. Direct evaluation against the comparable running-wave (RW) scheme shows the SW implementation's simultaneous advantage in cooling rate, motional mode bandwidth, and final phonon number, as previously theoretically predicted. Our work leverages capabilities enabled by integrated optical delivery to demonstrate fast cooling of multiple modes to the quantum ground state, and more broadly how scalable approaches to optical control can enable enhancements in fundamental atomic functionalities.
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All authors Zhenzhong Xing, Hamim Mahmud Rivy, Vighnesh Natarajan, Aditya Milind Kolhatkar, Gillenhaal Beck, Karan K. Mehta

Optics · Cross-listed from quant-ph

Quantifying classical and quantum bounds for resolving closely spaced, non-interacting, simultaneously emitting dipole sources in optical microscopy

Armine I. Dingilian, Aarnah Kurella, Cheyenne S. Mitchell et al. (+3 more)

Recent theoretical and experimental work has shown that the quantum Fisher information associated with estimating the separation between two optical point sources remains finite at small separations, effectively opening new routes to super-resolution imaging of simultaneously emitting sources. Most studies to date, however, implicitly invoke the scalar approximation, which is not appropriate in the context of high-numerical-aperture microscopy. Utilizing parameter estimation theory, here we consider the estimation of separation between two closely spaced dipole emitters, a commonly employed model for single-molecule optical beacons. We consider two limiting cases: one in which the orientations of the emitters are fixed and equal, and another in which both dipoles freely sample all of orientation space over the course of the measurement. We quantify precision limits using quantum and classical variants of the Fisher information and Cramér-Rao bound. In all cases, the vectorial nature of the emission complicates the analyses, but with appropriate filtering of the collected light in the azimuthal-radial polarization basis, a previously proposed scheme to saturate the quantum Fisher information via image inversion interferometry can be salvaged.
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All authors Armine I. Dingilian, Aarnah Kurella, Cheyenne S. Mitchell, Dhananjay Dhruva, David J. Durden, Mikael P. Backlund

Atmospheric and Oceanic Physics · Cross-listed from astro-ph.EP

Impact of geometry on 1D molecular-kinetics simulations of acoustic-gravity wave propagation into the exosphere

Jose A. Perez Chavez, Orenthal J. Tucker, Shane R. Carberry Mogan et al. (+2 more)

Direct Simulation Monte Carlo (DSMC) calculations of acoustic gravity wave propagation into the exobase region of a Mars-like atmosphere reveal that radial geometry can reduce wave-driven heating compared to a Cartesian model. We examine two acoustic wave (AW) modes with periods of 11 minutes (AW1) and 5.5 minutes (AW2) propagating from 100 to 320 km altitude using a radial molecular kinetics model. The wave-driven heating was reduced by 40-56% with cycle-averaged temperature gradient $\langle dT/dr \rangle$ decreasing from 9.4 K per scale height H0 to 5.6 K/H$_0$ for AW1 and from 4.4 K/H$_0$ to 1.9 K/H$_0$ for AW2 when accounting for planetary curvature. While the growth in wave density amplitude was attenuated for the 1D radial geometry as well, the heating differences are more pronounced, with both effects driven by geometric spreading accumulating as waves propagate into increasingly rarefied regions. These findings suggest that accounting for curvature effects is crucial when conducting DSMC estimates of acoustic wave contributions to thermospheric heating and atmospheric escape, as Cartesian-based derived counterparts may be overestimated by factors of 1.7-2.3 for these frequencies.
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All authors Jose A. Perez Chavez, Orenthal J. Tucker, Shane R. Carberry Mogan, Robert E. Johnson, Christopher Blaszczak-Boxe

Chemical Physics · Cross-listed from cond-mat.mes-hall

Topological Engineering of a Frustrated Antiferromagnetic Triradical in Aza-Triangulene Architectures

Francisco Romero-Lara, Manuel Vilas-Varela, Manish Kumar et al. (+16 more)

Open-shell nanographenes provide a versatile platform to host unconventional magnetic states within their {\pi}-conjugated networks. Particularly appealing are graphene architectures that incorporate spatially separated radicals and tunable interactions, offering a scalable route toward spin-based quantum architectures. Triangulenes are ideal for this purpose, as their radical count scales with size, although strong hybridization prevents individual spin control. Here, we realize a radical reconfiguration strategy that transforms a single-radical aza-triangulene into three topologically protected spin states by covalently extending it with armchair anthene moieties of increasing length. Scanning tunnelling spectroscopy reveals emergent correlated spins forming a frustrated spin trimer whose interaction weakens with anthene length. This trend is captured by multi-reference electronic-structure calculations, which trace a progressive rise in polyradical character driven by the progressive reorganization of the correlated frontier orbitals into three edge-localized natural orbitals. Consequently, the initial single-radical doublet reorganizes into non-interacting edge spins, a molecular analog of a three-qubit quantum register.
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All authors Francisco Romero-Lara, Manuel Vilas-Varela, Manish Kumar, Ricardo Ortiz, Alessio Vegliante, Lucía Gómez-Rodrigo, Trisha Sai, Jan Patrick Calupitan, Diego Soler, Nikas Friedrich, Dongfei Wang, Jon Ortuzar, Leonard Edens, Stefano Trivini, Thomas Frederiksen, Fabian Schulz, Pavel Jelínek, Diego Peña, Jose Ignacio Pascual

Chemical Physics

Basic requirements for potential differences across solid–fluid interfaces

David Fertig, Adrian L. Usler and Mathijs Janssen

At model water–vapor and water–solid interfaces, molecular ordering leads to charge oscillations and, thereby, to a spatially varying electrostatic potential. Atomistic simulations indicate that such ordering leads to an electric potential difference $\chi$, the surface potential, of about $-0.5\,\mathrm{V}$ across the first few molecular layers. Here, we calculate surface potentials at interfaces between a simple model fluids and a solid, with Molecular Dynamics simulations. The fluids are made up of either diatomic, dipolar molecules or a single Lennard-Jones particle with a dipole moment. All fluids show some structuring near the interface, but charge oscillations and a non-zero surface potential are present only for asymmetric molecules (unequal diameters of the atoms) or molecules with an off-center dipole. We condense this finding into the criterion that the geometric and dipolar centers of a molecule must differ for the fluid to exhibit a surface potential. Remarkably, while the solid–fluid interaction strength strongly affects the magnitude of charge oscillations, it hardly affects the potential drop $\chi$. Further, our results demonstrate that changing the diameter of the smaller atom can flip the sign of the surface potential, thus highlighting the importance of steric effects.
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Instrumentation and Detectors

Cosmic Ray Measurements Using Charge and Light Readout in a Pixelated Liquid Argon Time Projection Chamber

SoLAr Collaboration: N. Anfimov, A. Branca, J. Bürgi et al. (+39 more)

Liquid argon time projection chambers have emerged as a competitive technology for detecting solar neutrinos. The SoLAr collaboration was formed to explore argon detectors with pixelated light and charge readout, aiming for high detection efficiency and improved energy resolution. Building on the success of an initial prototype, we present results obtained with a second SoLAr prototype (V2), a $30 \times 30 \times 30$ cm$^{3}$ time projection chamber operated in a cryostat containing several hundred kilograms of liquid argon. We report measurements of cosmic-ray muons using both tracking and calorimetry from light and charge sensors, and we highlight the improved performance achieved through combined charge and light reconstruction. These results demonstrate the promise of dual-readout detectors and motivate future prototyping efforts toward kiloton-scale facilities.
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All authors SoLAr Collaboration: N. Anfimov, A. Branca, J. Bürgi, L. Calivers, P. Carniti, E. Calvo, E. Cristaldo, C. Cuesta, F. Declich, R. Diurba, P. Dunne, D. A. Dwyer, J. Evans, A. C. Ezeribe, A. Gauch, I. Gil-Botella, C. Gotti, S. Greenberg, D. Guffanti, A. Karcher, J. Kunzmann, N. Lane, S. Manthey Corchado, N. McConkey, A. Minotti, A. Navrer-Agasson, S. Parsa, G. Pessina, G. Ruiz Ferreira, B. Russell, S. Söldner-Rembold, A. M. Szelc, A. Tapper, F. Terranova, C. Tognina, D. Trotta, S. Tufanli, H. Vieira de Souza, G. Vitti Stenico, A. Verdugo, M. Weber, I. Xiotidis