Optics
Wearable metasurfaces for boosting the effective area of mobile-device antennas
Mohammad M. Asgari, Xianghui Qiu, Francisco S. Cuesta et al. (+5 more)
Wireless communications increasingly face scenarios with compact user equipments operating in propagation environments where signal blockage, absorption, and device size limitations strongly constrain link performance. Most approaches to wireless-link enhancement focus either on improving base-station
antenna systems, for example, through massive
MIMO architectures; on engineering the propagation environment using reconfigurable intelligent surfaces and active relays. Here, we propose an alternative user-side strategy for improving wireless links based on wearable metasurfaces that enhance the effective
antenna area of compact wireless devices. The proposed passive metasurface is integrated into clothing and engineered to collect the power of electromagnetic waves incident on user's body and route the collected power toward a mobile device in the form of surface waves. This mechanism significantly increases the effective receiving and transmitting area of the device
antenna and its gain without external power sources, active control electronics, or additional stand-alone hardware. We implement the concept on a hoodie textile using a scalable screen-printing process with conductive silver ink and demonstrate an approximately tenfold enhancement of the received signal at 26 GHz. This passive approach effectively brings the human body into the communication network by turning clothing into a virtual thin and flexible lens for focusing the incident power on the user equipment.
Read the full abstract ▾
All authors Mohammad M. Asgari, Xianghui Qiu, Francisco S. Cuesta, Shuai S. A. Yuan, Kamil A. Isik, Sergei Tretyakov, Xuchen Wang, Viktar Asadchy
Atomic Physics
Nuclear Spin Oscillator Based on $^3$He to Search for Exotic Spin Coupling
Heather R. Pearson, Anna Molodtsova, Sage C. Weisrock et al. (+2 more)
We describe an experimental investigation of a
nuclear spin oscillator based on $^3$He
nuclei as a possible detector to search for exotic
spin couplings. A magnetically shielded vapor
cell comprised of an alkali atom mixture ($95\%$ potassium and $5\%$ rubidium) and $^3$He gas is polarized via
laser light resonant with the $D_1$ transition in rubidium in the presence of a dc
magnetic field. The potassium atoms and $^3$He
nuclei are polarized via
spin-exchange collisions with the polarized rubidium atoms. The
nuclear spins are tipped with a
magnetic field applied perpendicular to the dc
magnetic field. The resulting Larmor precession of the $^3$He
nuclear spins is monitored via Faraday rotation of
laser light near resonant with the $D_1$ transition in potassium. The Faraday rotation signal is filtered, amplified, and used to apply a
magnetic field in a direction perpendicular to the dc
magnetic field, resulting in a self-sustained oscillation of the
nuclear spins at a frequency that is directly proportional to the dc
magnetic field. We demonstrate a sensitivity to exotic
spin couplings that is $\approx 5$ times higher than the alkali atom magnetometers that have been used in the Global Network of Optical Magnetometers to Search for Exotic Physics collaboration.
Read the full abstract ▾
All authors Heather R. Pearson, Anna Molodtsova, Sage C. Weisrock, Sherlock Tingrui Zhao, Jason E. Stalnaker
Optics
Experimental Observation of Ghost Image Revivals via Structured Coherence
Weining Wang, Yaning Zhou, Sergey A Ponomarenko et al. (+2 more)
Ghost imaging retrieves an object's image from intensity correlations between two light beams, neither of which independently carries information about the object. However, conventional ghost imaging critically relies on precise object positioning and conjugate matching between the two arms, causing the image to disappear when these conditions are violated and the object is accessible from one plane only. In this Letter, we break this fundamental limitation by reporting the first experimental observation of revivals of ghost images of arbitrary objects via engineering the longitudinal intensity autocorrelation of a structured thermal light field into a coherence comb. With the reference arm fixed, translating the object produces periodic revivals of the ghost image whenever the object position matches a comb-tooth position, reminiscent of the Talbot effect. This capability enhances the flexibility of correlation imaging, enabling robust tomographic imaging of moving and non-periodic complex objects.
Read the full abstract ▾
All authors Weining Wang, Yaning Zhou, Sergey A Ponomarenko, Yangjian Cai, Xin Liu
Instrumentation and Detectors · Cross-listed from astro-ph.IM
The beamformed trigger of RNO-G: its design and in-field performance
RNO-G Collaboration: S. Agarwal, J. A. Aguilar, N. Alden et al. (+75 more)
The
Radio Neutrino Observatory in Greenland (RNO-G) is a
neutrino detector under construction at Summit Station, with 8 out of a planned 35 stations currently deployed. We have designed and deployed a new phased array (PA) trigger based on delay-and-sum beamforming and power integration. This trigger improves detector performance by suppressing thermal noise and better targeting
neutrino-induced Askaryan signals. The new PA trigger has been deployed since the 2025 season. The trigger performance has been characterized using test pulses and calibration pulsers both in the lab and in-situ, and we find across these tests a 25% average reduction in the signal-to-noise ratio (SNR) needed to trigger on signals. Simulations are shown to be representative of the detector, and simulated trigger efficiencies are within 10% of measured data. Following the in-situ trigger validation, we use data-driven trigger performance to inform simulations of the detector effective volumes. The PA trigger increases our effective volume significantly, by over a factor of 2 below 0.1 EeV and at least a factor of 1.3 at the highest energies of 100 EeV.
Read the full abstract ▾
All authors RNO-G Collaboration: S. Agarwal, J. A. Aguilar, N. Alden, S. Ali, P. Allison, M. Betts, D. Besson, A. Bishop, O. Botner, S. Bouma, S. Buitink, R. Camphyn, J. Chan, S. Chiche, B. A. Clark, K. Couberly, D. Dakroub, K. D. de Vries, C. Deaconu, P. Giri, C. Glaser, H. Gui, A. Hallgren, J. C. Hanson, S. Hassiki, K. Helbing, B. Hendricks, J. Henrichs, N. Heyer, C. Hornhuber, E. Huesca Santiago, K. Hughes, A. Jaitly, A. Karle, J. L. Kelley, C. Kopper, M. Korntheuer, M. Kowalski, I. Kravchenko, R. Krebs, M. Kugelmeier, D. Kullgren, R. Lahmann, C.-H. Liu, Y. Liu, M. J. Marsee, K. Mulrey, M. Muzio, A. Nelles, A. Novikov, A. Nozdrina, E. Oberla, N. Punsuebsay, M. Ravn, Z. Riesen, A. Rifaie, D. Ryckbosch, F. Schlüter, O. Scholten, P. Schriefer, D. Seckel, M. F. H. Seikh, Z. S. Selcuk, J. Stachurska, J. Stoffels, S. Toscano, D. Tosi, J. Tutt, N. van Eijndhoven, A. G. Vieregg, A. Vijai, H. Warnhofer, D. Washington, C. Welling, D. R. Williams, P. Windischhofer, S. Wissel, A. Zink
Physics and Society · Cross-listed from cond-mat.dis-nn
A Grand-Canonical Solution to a Class of Random Optimization Problems
Izat B Baybusinov, Enrico M Fenoaltea, Zhen Han et al. (+1 more)
We introduce a general framework to solve a class of combinatorial opti- mization problems, including the matching problem, the Traveling Salesman Problem, and also the minimum weight k-factor problem. By reformulating these problems as an arrangement model, we recast the optimization task into a grand-canonical ensemble, where chemical potentials are used to re- lax strict topological constraints. The analytical solution found can serve as a
polynomial-time
algorithm to compute an approximate minimum cost for arbitrary k and link-weight distributions. Our framework is complementary to existing approaches and reveals new connections between combinatorial optimization and the statistical physics of disordered systems.
Read the full abstract ▾
All authors Izat B Baybusinov, Enrico M Fenoaltea, Zhen Han, Yi-Cheng Zhang
Physics and Society · Cross-listed from eess.SY
Does Central Planning Fail Locally? Evaluating EV Charging Flexibility Optimization Across Grid Levels
Ambra Van Liedekerke, Lorenzo Zapparoli, María Parajeles Herrera et al. (+3 more)
Electric vehicles (EVs) are a key enabler of global decarbonization, and their charging flexibility is crucial for integrating high shares of renewable energy into future power systems. Research on EV charging flexibility in future power systems has largely focused on either the transmission or the distribution level, with limited integration between the two. However, these two scales cannot be separated: EV charging optimized at the national transmission level for system-wide planning is ultimately activated in local distribution grids, where it may cause voltage and loading issues. This study bridges that gap by evaluating EV charging flexibility across both grid levels, using two different control approaches. First, a top-down approach disaggregates the optimal charging demand obtained from a centralized planner at the transmission grid down to the distribution grid, explicitly accounting for grid constraints and individual driving requirements. Second, a bottom-up approach optimizes EV charging locally under distribution-grid constraints using electricity price signals from the centralized planning model. Controlled charging from the top-down and bottom-up approaches is then compared with uncontrolled charging. Results show that the top-down approach produces EV charging schedules that are compatible with individual driving behavior and reduce grid violations compared to uncontrolled charging. The bottom-up approach identifies an optimal profile similar to the centrally optimized profile, showing that electricity price signals are a suitable coordination mechanism. These findings suggest that centrally optimized EV charging remains effective when implemented at the distribution level, in systems with high DER penetration.
Read the full abstract ▾
All authors Ambra Van Liedekerke, Lorenzo Zapparoli, María Parajeles Herrera, Blazhe Gjorgiev, Gabriela Hug, Giovanni Sansavini
Optics
Wavelength-diverse transmission for turbulence-resistant free-space optical communication
Nicolas Couture, Brandon Buscaino, Douglas Charlton et al. (+2 more)
Free-space optical communication (FSOC) links are susceptible to outages caused by atmospheric
turbulence-induced fading. Wavelength diversity can mitigate fading by transmitting correlated information across substantially uncorrelated channels. In this study, we demonstrate a wavelength diversity system to mitigate the effects of
turbulence on a signal propagated in free space. A modified polarization-multiplexed coherent optical transceiver transmits a 56.8 GBaud signal at a client rate of 200 Gbps across two carrier frequencies within the C-band over a bench-top free-space link with a
turbulence emulator. Two synchronized single-wavelength coherent receivers capture the received waveforms at each carrier frequency, which are subsequently digitally combined using maximal ratio combining for offline processing. Our results demonstrate a reduction in outage probability by nearly a factor of 20 compared to the single carrier transmission scenario. Finally, we observe fading-dependent correlation between wavelengths in the C-band, which is exploited to reduce the outage probability by 86%.
Read the full abstract ▾
All authors Nicolas Couture, Brandon Buscaino, Douglas Charlton, Mohammad E. Mousa-Pasandi, Kim B. Roberts
Computational Physics
Stochastic Counterdiabatic Driving via Biorthogonal Liouvillian Eigenmodes
Sandeep Suresh Cranganore, Sebastian Lehner, Johannes Brandstetter et al. (+1 more)
Finite-time driving of
stochastic systems generates excess dissipation, causing the evolving probability distribution to lag behind the instantaneous
equilibrium, and consequently degrading the convergence of nonequilibrium free energy
estimators based on the Jarzynski equality. Escorted free energy simulations address the non-adiabatic lag by engineering control fields $\mathbf{u}$ that eliminate the lag, enforcing the trajectory-wise equality $\mathcal{W}_\mathbf{u} = \Delta \mathcal{F}$, and yielding zero-variance
estimators. However, constructing the escorting field in closed form remains a challenge, approached variously through flow-field methods, targeted free energy perturbation, or learned diffeomorphisms. In this work, we construct a complementary numerical framework based on gauge-type transforms instead of generalized coordinate transforms for perfect escorting based on the exact spectral decomposition of the time-dependent Fokker-Planck generator. The biorthogonal decomposition of the Liouville operator directly yields a counterdiabatic correction whose action on the instantaneous
equilibrium distribution exactly cancels the non-adiabatic lag at arbitrary driving speed in formal analogy with shortcuts-to-adiabaticity techniques such as Berry's transitionless driving for
quantum systems. Numerical verification for simulations of an overdamped particle in a time-varying double-well potential and harmonic traps confirms that the counterdiabatic condition is satisfied to machine precision, with the non-adiabatic lag suppressed by roughly twelve orders of magnitude in total variation distance and sixteen orders in KL divergence relative to the unescorted dynamics. As a diagnostic, we demonstrate vanishing dissipated work $\mathcal{W}_{\text{diss}}(t) \approx 0$ for the deterministically propagated Fokker-Planck density across all protocol speeds.
Read the full abstract ▾
All authors Sandeep Suresh Cranganore, Sebastian Lehner, Johannes Brandstetter, Max Welling
Optics · Cross-listed from astro-ph.IM
Sensitivity of Laguerre-Gaussian Modes to Misalignment and Mode Mismatch in Gravitational-Wave Detectors
Liu Tao and Matteo Barsuglia
Higher-order Laguerre-Gaussian (LG) modes have broader and more uniform transverse intensity distributions than the fundamental Gaussian mode, making them attractive for precision optical applications. In gravitational-wave detectors, their enhanced spatial averaging of thermally driven test-mass fluctuations can reduce thermal noise. Their implementation, however, requires efficient coupling of the injected beam to the target cavity eigenmode. Residual misalignment and mode mismatch couple power out of the desired mode, reducing intracavity power buildup and degrading detector sensitivity. Here, we analytically and numerically evaluate the coupling loss induced by misalignment and mode mismatch for a generic $\mathrm{LG}_{p,\ell}$ beam. We show that the leading-order loss due to angular or lateral misalignment scales as $2p+|\ell|+1$, whereas that due to waist size or waist position mismatch scales as $2p^2+2p+(2p+1)|\ell|+1$. Although sensitivity to imperfect coupling generally increases with mode order, the donut-shaped $\mathrm{LG}_{0,\ell}$ family exhibits favorable mode mismatch scaling: its loss factor reduces to $|\ell|+1$ and therefore increases only linearly with the azimuthal index. This robustness, together with their broad intensity profiles and central dark regions that permit selective mirror masking, provides additional practical motivation for using $\mathrm{LG}_{0,\ell}$ modes in precision interferometers, including gravitational-wave detectors.
Read the full abstract ▾
Applied Physics · Cross-listed from cond-mat.mes-hall
Large-area CVD Graphene for Photogating-Based Photodetection
D.A. Matienko, D.P. Borisenko and A.Yu. Kuntsevich
Our work explores large-area CVD
graphene as a scalable platform for photodetectors. We show that substrate-induced photogating in
graphene/SiO$_2$/Si structures enables a photoconductivity signal in mono-, bi-, and trilayer CVD
graphene. The devices respond to illumination with
photon energies above the Si band gap and do not respond to telecom frequency, suggesting the photoconductivity mechanism through the photogating. Large sample area and gate voltage-dependent resistivity measurements allow us to prove the dominant role of the photogating directly, demonstrating similarity of the capacitive recharging current and the photoresponse. The sensitivity is the highest (995 A/W) for the monolayer
graphene. Increasing the number of
graphene layers reduces the sensitivity due to screening and parallel conduction, but can improve detectivity by lowering the noise level. The sensitivity of CVD
graphene device depends on fabrication route of photolitography: device with metal contacts fabricated before
graphene transfer show higher photoresponce. Thus, our work demonstrate the potential of industrially relevant CVD
graphene for sensitive photogating-based photodetectors.
Read the full abstract ▾
Optics
Lead nanoparticles, the deep-ultraviolet to near-infrared plasmonic platform
Michael Foltýn, Michal Kvapil, Kristýna Bukvišová et al. (+2 more)
Among the other non-noble metals, lead (Pb) is a material of particular interest for plasmonic applications in the deep ultraviolet spectral region. However, experimental studies on its plasmonic performance have not yet been conducted. In this work, the dependence of the optical properties of spherical lead nanoparticles on their diameter is demonstrated. The plasmonic performance of chemically synthesized lead nanoparticles is evaluated at the single-particle level by means of a combination of scanning transmission electron microscopy and electron energy loss spectroscopy. Our findings demonstrate that these nanoparticles support localized surface plasmon resonances across the entire spectrum from near-infrared to deep-ultraviolet. This range was identified as the most extensive among all plasmonic elemental metals, extending to wavelengths below 200 nanometers. Consequently, lead nanoparticles exhibit stable plasmonic performance over a remarkably broad wavelength range, thereby substantiating their potential as a multispectral plasmonic platform.
Read the full abstract ▾
All authors Michael Foltýn, Michal Kvapil, Kristýna Bukvišová, Tomáš Šikola, Michal Horák
Classical Physics · Cross-listed from gr-qc
The Magnusian generator for dissipative systems and application to leading 2.5PN radiation-reaction dynamics
Francisco M. Blanco
The Magnusian is a phase-space function that generates finite-time
evolution through nested Poisson brackets. It is related to several familiar generators of classical dynamics, including the radial action, the eikonal phase and related quantities. In this work, we extend the Magnusian framework to systems with dissipation and nonlocal-in-time interactions using the in-in formalism, also known as the Schwinger-Keldysh or Galley formalism. This framework is particularly natural for binary dynamics, where integrating out the mediating gravitational field can produce both dissipative radiation-reaction effects and hereditary, nonlocal-in-time interactions. We derive the generalized Magnusian and show that it continues to generate finite-time
evolution. As an application, we construct the Magnusian for Newtonian bound motion subject to the leading 2.5PN radiation-reaction force. The resulting generator defines a discrete
evolution map from one cycle to the next and describes the
evolution of the system in agreement with numerical solutions.
Read the full abstract ▾
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Aligning Heterogeneous DFT Datasets: A Graph Neural Network Approach to Cross-Functional Formation Energies
Yidong Huang, Tenglong Lu, Hanwen Kang et al. (+3 more)
Heterogeneous density functional theory (DFT) calculations, particularly plane-wave implementations, introduce systematic formation energy errors ranging from tens to hundreds of meV/atom, depending on the selection of exchange-correlation functionals, kinetic energy cutoffs, pseudopotentials, and dispersion corrections. As demonstrated by the MatPES
dataset, identical structures can exhibit an average energy discrepancy of 107 meV/atom between PBE and r2SCAN calculations. Such method-dependent discrepancies hinder the integration of multi-source DFT data, greatly limiting the scale and quality of
datasets for training robust materials AI models. Here, we resolve this fundamental data silo barrier via graph-based transfer learning. Leveraging 380,190 structurally paired PBE-r2SCAN entries from the MatPES database, we train a structure-aware graph neural network to predict cross-functional energy residuals and align inconsistent DFT energy scales. By adopting GPTFF model architecture, the model converts conventional PBE energies to r2SCAN-level accuracy with a mean absolute error of 14.3 meV/atom, compared with 18.2 meV/atom achieved by CHGNet. This versatile approach effectively upgrades massive legacy PBE
datasets to high-precision r2SCAN standards. It enables reliable predictions of phase stability, battery voltage profiles, and reaction thermodynamics, while allowing the integration of multi-source DFT data to advance the development of high-performance materials foundation models.
Read the full abstract ▾
All authors Yidong Huang, Tenglong Lu, Hanwen Kang, Junfeng Huang, Sheng Meng, Miao Liu
Atmospheric and Oceanic Physics · Cross-listed from stat.AP
Memory operator ensembles indicate proximity to criticality in simulated AMOC transitions
Mauricio Herrera-Marín
Classical early-warning signals assume that recovery slows near a tipping point, but in a well-studied CESM simulation of AMOC collapse, autocorrelation and variance decrease instead. We develop a preregistered diagnostic that uses only past data to estimate the slowest mode of a
memory operator fitted to the evolving overturning structure. The operator ensemble produces an exploratory alarm 77 years before collapse, compared with 29 years for a physics-based freshwater-transport indicator. A blind test on the recovery branch does not validate the same timing rule, supporting interpretation of the diagnostic as a proximity measure rather than a universal clock. In nine additional simulations, it warns before all four finite-rate forced transitions but not before three rapid noise-induced collapses available only as scalar AMOC records. Matched ablations show that the signal depends on long-timescale
memory and vertical overturning structure rather than trend, forcing, or multivariate information alone.
Read the full abstract ▾
Physics and Society
Teacher Knows It Best: Spontaneous Symmetry Breaking and Tipping Points in Networked Langevin Dynamics AI Sycophancy
Sayantari Ghosh, Saumik Bhattacharya and Partha Pratim Chakrabarti
We formulate a statistical physics framework to model a networked
stochastic dynamical system exhibiting bistability, driven by additive noise and social conformity. We apply this model to understand and mitigate AI-induced delusional spiraling-a phenomenon where algorithmic sycophancy from Large
Language Models continuously reinforces inaccurate beliefs within a socially interacting society. By partitioning the network into a majority of regular
agents and a minority of "aware" nodes (Teachers) placed at topological hubs, we use a degree-weighted mean-field approximation to reduce high-dimensional coupled Langevin equations into a single macroscopic drift equation. We provide a closed-form analytical derivation for the deterministic critical tipping time through a saddle-node bifurcation. We validate this analytical boundary using finite-size scaling and demonstrate a universal data collapse across diverse network
topologies. Finally, we optimize an intervention strategy under a strict budget constraint that balances the topological footprint against driving velocity. We prove mathematically that under certain conditions, a highly concentrated, rapid intervention targeting massive hubs strictly outperforms a distributed, slow approach to rescue the network.
Read the full abstract ▾
Optics
Comparison between methods to measureintensity modulator Vpi
Gilles Feugnet, Salma Essawab, Jimmy Pennanech et al. (+6 more)
We describe and compare in this paper two common methods to measure the half-wave voltage (Vpi) of an electro-optical modulator versus RF frequency of the driving electronic signal. We detail the required calibration procedures when necessary and demonstrate the methods experimentally from 100MHz up to 40GHz. Guidelines are finally given to select the most appropriate method depending on the application and modulator characteristics.
Read the full abstract ▾
All authors Gilles Feugnet, Salma Essawab, Jimmy Pennanech, Delphine Pommier, Jerome Bourderionnet, Arnaud Brignon, Benoit Benazet, Homa Zarebidaki, Waldemar Schmidt
Fluid Dynamics
Bubble growth on arrays of micro-electrodes
Mengyuan Huang, Gerd Mutschke, Zhicheng Yuan et al. (+1 more)
Gas bubbles evolving on electrodes during water-electrolysis are blocking active reaction area, thus hindering mass transfer and raising Ohmic resistance. Unlike earlier models that prescribe a uniform current density on the wetted part of the electrode, we resolve the primary electric field, which allows the current density and the interfacial gas production to respond to the geometry of the electrode and the temporal
evolution of the bubbles. Using three-dimensional geometrical volume-of-fluid (VOF) simulations with phase change in Basilisk, we examine the growth of single-bubbles on electrodes of different size and of multiple bubbles growing on arrays of catalytic electrode islands. The non-uniform current density and the associated Ohmic resistance significantly affect the growth dynamics. Unlike the case of a single bubble, the outer bubbles in case of electrode islands tend to drift outward during growth, thus delaying full electrode coverage and sustaining current. Footprint tracking and a theoretical analysis show that this drift is governed by the
liquid advection driven by the growth of neighboring bubbles, scaling with their separation 1/d2, and modulated by the current-density asymmetry. These results show how electrode patterning and bubble spacing can be exploited to tailor the electric field distribution and reduce bubble-induced resistive losses during water electrolysis.
Read the full abstract ▾
All authors Mengyuan Huang, Gerd Mutschke, Zhicheng Yuan, Kerstin Eckert
Fluid Dynamics · Cross-listed from cond-mat.soft
Steady base states in a two-dimensional chiral fluid. The chiral Stokes cavity
Francisco Vega Reyes
We develop from first principles the hydrodynamics of a two-dimensional
chiral fluid, i.e. one carrying a net microscopic angular-momentum (
spin) field. Enforcing angular-momentum conservation without imposing stress-tensor
symmetry, we derive the full form of the stress tensor and of the
spin flux, and we show that the entire
chiral response is generated from the classical Newtonian one by a single operation of direct physical origin — the $90^{\circ}$ rotation through which chirality acts, mirrored at the particle level by transverse forces (Caprini & Marini Bettolo Marconi 2025). Applied to the irreducible (deviatoric) decomposition, the rotation assigns to each classical channel a
chiral partner — pressure to
chiral pressure, bulk and shear viscosities to their odd counterparts, the
spin-flux gradient to its rotated image — one coefficient and one mechanical action per channel, with no further cross-couplings. In this representation the steady base states become elementary. Quiescent states are organised by a holomorphic
chiral complex potential, the mechanical and
chiral pressures forming a conjugate harmonic pair subject to a topological existence condition; inhomogeneous activity forces azimuthal flows; and a boundary-driven confined flow, the
chiral Stokes cavity, obeys a modified Helmholtz–Poisson system, solved in closed form in a circular domain and numerically in a square one. A single dimensionless group controls both geometries and sets the crossover from a screened, single-
vortex regime to a sequence of sign-reversing vortical structures. The theory yields quantitative predictions, amenable to direct comparison with experiments on air-fluidised
chiral disks (López-Castaño et al. 2022), and recovers the phenomenological frameworks of the
chiral-fluid literature as particular cases.
Read the full abstract ▾
Optics
Hyperspectral imaging for inline quality monitoring of roll-to-roll slot-die coated organic photovoltaic active layers
Abdelouadoud Mammeri, Søren Alkærsig Jensen, Søren AR Kynde et al. (+5 more)
Lab-scale organic
solar cells have shown high efficiency and strong potential for large-scale production. Among the fabrication techniques for upscaling production, roll-to-roll slot-die coating offers a cost-effective route toward scalable manufacturing. However, reliable in-line metrology is needed for real-time assessment and quality control of the coating during roll-to-roll manufacturing. In this work, we employ a hyperspectral camera for inline monitoring of P3HT and OIDTBR active layers in a roll-to-roll setup. Using multivariate curve resolution, we reliably resolved the spatial distribution of donor and acceptor contributions in the coating. Furthermore, by fitting the absorbance spectra of P3HT, we map the
exciton bandwidth, providing insights into the
polymer's aggregation and chain interactions. These results demonstrate the potential of hyperspectral imaging as a powerful tool for real-time monitoring and quality control in large-scale organic
solar cell production.
Read the full abstract ▾
All authors Abdelouadoud Mammeri, Søren Alkærsig Jensen, Søren AR Kynde, Astrid Tranum Rømer, Raimo Korhonen, Matteo Ciambezi, Moises Espindola, Jens Wenzel Andreasen
Instrumentation and Detectors
Spatial resolution for gamma ray interactions in stacks of monolithic silicon sensors
Luca Terenzi, Sara Garbolino, Elias Rieger et al. (+5 more)
We are developing a new implementation of Compton imaging for
nuclear medicine using a large volume of stacked monolithic silicon sensors. In this work we investigate how the spatial resolution is impacted by the pixel size, an important input to the design of the sensors. In general CMOS design is less challenging with larger pixels leaving more space for analog and digital electronics. On the other hand, spatial resolution is one of the key parameters that will impact the performance of the Compton imaging system. It is also important to consider the range of the
recoil electron produced in Compton or photoelectric interactions, which impacts how accurately the interaction point can be estimated. The achievable resolution was evaluated with two interaction position reconstruction
algorithms: one based on a Gaussian fit of the detected charge and a second based on the characteristic energy deposition along the electron track, with the former performing better at lower energies. Monte Carlo simulations were performed for 140 keV and 511 keV sources embedded in a water phantom, with pixel pitches ranging from 25 $\mu m$ to 250 $\mu m$. Energy-averaged in-plane resolution degraded from 8 $\mu m$ to 94 $\mu m$ as pixel size increased. The out-of-plane resolution was 216 $\mu m$ at low energies, limited by sensor thickness, and improved to 155 $\mu m$ at higher energies. The results suggest that pixel sizes in the order of 100 $\mu m$ can achieve spatial resolutions on the order of tens of micrometers.
Read the full abstract ▾
All authors Luca Terenzi, Sara Garbolino, Elias Rieger, Mats Persson, Moa Yveborg Tamm, Manuel Da Rocha Rolo, Lucio Pancheri, Mats Danielsson
Fluid Dynamics
Influence of a vertical-wall leading edge on bouncing and escape bubble rising regimes
A. Rubio-González, E. J. Vega and R. Bolaños-Jiménez
This work investigates deformable gas bubbles rising near a vertical wall in ultrapure water, focusing on how the position of the wall leading edge affects their near-wall dynamics. Two configurations are considered: (i) a wall extending from 11–25 bubble diameters below the bubble injection point, so that the bubble rises under the continuous influence of the boundary; and (ii) a wall whose leading edge is located 144 mm above the injector, corresponding to approximately 80–180 bubble diameters, allowing the bubble to reach its terminal velocity before entering the wall-bounded region. The results show that the wall leading-edge position influences both the transition from periodic bouncing (PB) to bouncing–tumbling–escaping (BTE) dynamics and the rebound frequency within the PB regime. When the wall leading edge is placed downstream, the onset of BTE occurs at smaller bubble sizes, corresponding simultaneously to lower Bond ($Bo$), Galilei ($Ga$), and Reynolds ($Re$) numbers. The Strouhal number ($St$) follows a similar decreasing trend in both configurations at low Bond numbers, but the two behaviours diverge for ($Bo \gtrsim 0.15$). For the PB regime, when the wall extends from the injector, $St$ approaches an approximately constant value of $St\simeq0.014$, whereas substantially lower values are measured for the downstream-wall configuration. The larger rebound amplitudes and longer return stages observed in the latter configuration account for lower frequencies. These findings indicate that the bubble dynamics depend not only on the conventional control parameters and wall separation, but also on the wall geometry and the associated pre-interaction bubble hydrodynamic history.
Read the full abstract ▾
Optics
Ultranarrow-linewidth self-injection-locked tunable blue GaN DFB laser
Georges Perin, Laurent Lablonde, Marco Rossetti et al. (+4 more)
In this work, we demonstrate an ultra-narrow linewidth self-injection locked distributed feedback (DFB) diode
laser emitting at 452 nm, achieving an intrinsic linewidth of 170 Hz with a fiber output power of 11 mW. The linewidth reduction of the DFB
laser is obtained thanks to the coupling with an external cavity based on a fiber Bragg grating (FBG). Experimental results demonstrate excellent agreement with our theoretical modeling of the self-injection dynamics. Furthermore, the tuning capabilities of the system are characterized, with tunability achieved via current modulation, yielding a tuning efficiency of 300 MHz/mA over a continuous mode-hop-free range of 600 MHz. This architecture offers a robust pathway toward an integration within a compact package. Ultimately, such compact, stable, and frequency-tunable visible light sources are key for integrated optical atomic clocks and
underwater lidar application.
Read the full abstract ▾
All authors Georges Perin, Laurent Lablonde, Marco Rossetti, Marco Malinverni, Antonino Castliglia, Marcus Duelk, Stéphane Trebaol
Atomic Physics
Evolution of dipole-dipole dynamics in cold ammonia collisions
Yao Chang, André J.A. van Roij, Stach E.J. Kuijpers et al. (+4 more)
Cold polar molecules offer fascinating prospects for ultracold chemistry and
quantum physics, including new platforms for
quantum simulation or computation. However, their inherent collision properties remain largely unknown. It has proven extremely hard to experimentally probe collisions between two dipolar molecules at sufficiently low energies and high precision, as it appears fundamentally impossible to merge two beams of molecules with significant dipole moments. Here we report measurements of state-to-state cross sections for collisions between ammonia isotopologues at energies between 0.3 and 100 cm$^{-1}$ using a novel beam merger. We experimentally observed a local maximum in the cross sections that indicates the effective dipole moments can switch off at low collision energies. Scattering calculations reproduced this maximum in good agreement and explained the observed scaling with the parity splitting energies in the molecular energy level structures. Measurements of the correlated energy transfer in both collision partners yielded direct evidence of the suppression of the dipole-dipole interaction at low energies. Our results demonstrate how collisions between an important class of polar molecules evolve from the high temperature limit towards the ultracold regime in a counterintuitive way, have major consequences for the feasibility of future experiments and the interpretation of previous work, and offer distinctive opportunities to control cold molecular collisions with external fields.
Read the full abstract ▾
All authors Yao Chang, André J.A. van Roij, Stach E.J. Kuijpers, Sven Herbers, Etienne F. Walraven, Tijs Karman, Sebastiaan Y.T. van de Meerakker
Plasma Physics
Quasistatic modeling of ultrarelativistic beam-plasma instabilities
P. San Miguel Claveria, L. Gremillet, X. Davoine et al. (+5 more)
Relativistic particle beams propagating through dense ambient
plasmas are susceptible to streaming instabilities that can govern the system dynamics in various astrophysical and laboratory settings. For an unmagnetized, collisionless
plasma pervaded by a dilute, cold relativistic beam, the dominant instabilities are the quasielectrostatic, oblique two-stream (OTSI) and the essentially
magnetic, current filamentation instability (CFI). While their linear and nonlinear properties have been researched for decades, most treatments assume unbounded, uniform systems and thus predict purely temporal instability growth. This assumption, however, is questionable for realistic configurations where a bounded beam continuously encounters fresh
plasma. This feature causes instabilities to grow in a spatiotemporal manner. Whereas spatiotemporal perturbative treatments of streaming instabilities were derived as early as the 1960s, only recently have the spatiotemporal regimes of OTSI and CFI been addressed theoretically. Yet these models are restricted to a specific instability class, and hence cannot describe the competition between spatiotemporal OTSI and CFI. In this work, we present a unified, fully electromagnetic quasi-static model of all unstable modes arising throughout the beam. By not adopting the slowly varying envelope approximation (SVEA), we find that a previously unreported spatiotemporal CFI actually prevails near the front, precisely where the SVEA fails, and is only superseded by OTSI further back in the beam. Furthermore, we demonstrate that our model also captures the growth of the self-modulation and hosing instabilities excited by long, narrow beams. Comparisons with particle-in-
cell simulations confirm the validity of the quasistatic approach for modeling streaming
plasma instabilities triggered by relativistic dilute beams.
Read the full abstract ▾
All authors P. San Miguel Claveria, L. Gremillet, X. Davoine, Q. Labro, A. Matheron, M. Tamburini, F. Fiuza, S. Corde
Plasma Physics
Modeling ultrarelativistic streaming plasma instabilities under the quasistatic approximation
P. San Miguel Claveria, Q. Labro, X. Davoine et al. (+5 more)
Plasma streaming instabilities excited by relativistic charged particle beams play a pivotal role in astrophysical and laboratory environments. Their numerical study, however, is challenged by the disparity in spatiotemporal scales between the background
plasma and beam particles, which can differ by several orders of magnitude for tenuous, ultrarelativistic beams. Here, we exploit the quasistatic approximation (QSA) to develop a new theoretical framework capable of capturing the full unstable spectrum in the spatiotemporal regime relevant for beams that continuously encounter unperturbed
plasma at their leading edge. Within this linear, fully electromagnetic model, we uncover a previously unreported spatiotemporal
evolution of the current filamentation instability and elucidate its interplay with the oblique two-stream instability, predicting the dominance of filamentation in the vicinity of the beam front. The good agreement between theory, kinetic particle-in-
cell (PIC) simulations, and QSA-based PIC simulations validates the robustness of the approach. By pushing QSA-based PIC simulations to extremely dilute electron-positron beams, such as those found in blazar jets, we demonstrate their unique ability to capture the rich nonlinear dynamics of streaming instabilities in parameter regimes previously inaccessible to kinetic simulations.
Read the full abstract ▾
All authors P. San Miguel Claveria, Q. Labro, X. Davoine, A. Matheron, M. Tamburini, S. Corde, L. Gremillet, F. Fiuza
Instrumentation and Detectors
MADHAT: A Sensor Prototype for the ALICE 3 Outer Tracker
Philip Hauer, Lars Döpper, Malte Grönbeck et al. (+3 more)
The ALICE collaboration plans a completely new tracking detector based on silicon MAPS technology manufactured in the 65 nm production node as part of the ALICE~3 upgrade during Long Shutdown 4 of the LHC. The size of the whole active area is planned to be 50 m$^2$, with the Outer Tracker spanning 45 m$^2$. To reach the material budget target of less than 1% $X_0$ per layer, open questions like cooling solutions, mechanical structures and electronics have to be answered. A simple sensor prototype MADHAT (Mechanical Assessment Design for Heat And Thermal solutions), mechanically identical to the final sensor, but with integrated heating elements and temperature probes, was developed to study the temperature distribution in the final detector assembly and to assess different mechanical designs of the
circuit board that houses the sensor. Furthermore, it will be used to practice the industrialization of the whole mass-production, including the assembly of FPCs with external companies. In this paper, we present the design of the MADHAT, a prototype readout module and show the results of first measurements.
Read the full abstract ▾
All authors Philip Hauer, Lars Döpper, Malte Grönbeck, Alexander Rachev, Felix Lochter, Bernhard Ketzer
Optics · Cross-listed from math.AP
Non-singular hotspots between closely spaced high-index nanoparticles
Konstantinos Alexopoulos, Bryn Davies and Pierre Millien
We study the concentration of the field between two nearly touching high-index dielectric resonators in three dimensions. The model is a scalar Helmholtz transmission problem in the resonant regime, wherein the wavelength inside the resonators of the same order as their typical diameter. The material contrast enters only a lower-order term of the equation and not its principal part. As a consequence, the gradient of the field stays bounded independently of the distance separating the particles, and does not blow up. Nevertheless, simulations and experiments show that the gradient still concentrates in the gap: as the particles approach, it grows like the inverse of their separation over an intermediate range of distances and then saturates once they are very close. We explain this pre-asymptotic effect through a weak-coupling regime, in which the resonant modes of the pair are perturbations of the modes of each isolated particle. When such a mode keeps a nonzero contrast between the two facing boundaries, a mean value argument across the gap accounts for the growth of the gradient; this requires strengthening the standard spectral perturbation estimates from an average to a pointwise control. The growth stops once the interaction between the particles is no longer weak and the perturbation theory fails. Numerical experiments confirm the transition from amplification to saturation.
Read the full abstract ▾
Accelerator Physics
Gravity-Aligned Vertical Electron-Positron Linear Collider
Tetsuo Abe
A
gravity-aligned vertical electron-positron linear
collider is proposed as a concept to break the cost-and-scale impasse that confronts conventional horizontal
Higgs factories. The accelerating axis is oriented along the local gravitational field inside a single deep vertical shaft. Positrons are injected downward from the surface while electrons are accelerated upward from the bottom, the two beams meeting at an interaction point located deep underground. Targeting a staged center-of-mass energy in the
Higgs factory range (250-500 GeV), this concept assumes high-gradient, high-efficiency, normal-conducting accelerating structures operated at cryogenic temperature together with a two-beam power-delivery scheme. It can be designed to reuse the existing KEK/SuperKEKB accelerator complex at the KEK Tsukuba Campus. We discuss the advantages of the vertical orientation, namely a small surface footprint, intrinsic azimuthal
symmetry of the
gravity load, deep vibration isolation of the collision point,
gravity-assisted cryogenics, a natural vertical
alignment reference, a cosmically quiet deep interaction point, an opportunity for on-site electricity self-sufficiency, and a unique opportunity in social/industrial evaluation, as well as the principal disadvantages and challenges, including the required accelerating gradient and the construction of a kilometers-deep shaft. Using only publicly available information, we argue that excavating a shaft with a depth of ~3 km is feasible at a geologically favorable site. This paper is deliberately concept-level and is intended to motivate technological innovation, feasibility studies, and the exploration of possible new channels for Beyond-Standard-Model searches through vertical collisions.
Read the full abstract ▾
Chemical Physics · Cross-listed from cond-mat.dis-nn
Coupling of Cation and Anion Dynamics in Solid Electrolytes Revealed by Virtual Isotopic Substitution Molecular Dynamics
Xintian Wang, Andrew L. Goodwin and Theodosios Famprikis
We characterise the interplay between cation-translational and anion-rotational dynamics on the model system $\rm \alpha\text{-}Li_{2}SO_{4}$ through virtual isotopic substitution molecular dynamics (VISMD) simulations. We independently control in turn the lithium translational- and sufate rotational- diffusivity by varying the masses of lithium and oxygen, respectively, showing that both diffusivities exhibit power-law relationships with the masses of each individual component. Changing either diffusivity produces an effect on the other; i.e. there exists a bidirectional coupling between anion and cation diffusive dynamics. From our variable-temperature/variable-mass
dataset we demonstrate that the apparent activation energy for lithium
diffusion depends strongly on the isotope mass, decreasing with accelerated sulfate dynamics; an observation which provides clear evidence of mode-coupling between cation and anion dynamics.
Read the full abstract ▾
Physics and Society
Nonlinear Model Reduction of Complex Networks via Spectral Submanifolds
Kaviya Bhaskaran, Shobhit Jain and Mingwu Li
Complex networked systems are prevalent in biology, engineering, and the social sciences, yet their high-dimensional, nonlinear dynamics pose major challenges for analysis and prediction. A mathematically rigorous route to simplification is to represent system behavior on a low-dimensional, smooth invariant
manifold known as a spectral submanifold (SSM). Here we present a comprehensive SSM reduction framework and its globalized extension (gSSM) for dimensionality reduction in large-scale nonlinear networks. Our approach yields accurate global and node-level predictions across synthetic and real networks, including highly heterogeneous
topologies and systems with higher-order interactions. Crucially, SSM is a robust tipping-point predictor: even at low truncation order (e.g., $O(2)$) it reliably identifies the onset of sustained activity, while higher orders and gSSM capture post-onset amplitudes and saturation. Consistently, the reduction collapses the full network dynamics to a one-dimensional system, offering clarity and efficiency. Across all the realizations, SSM/gSSM consistently outperform classical spectral and mean-field methods in modeling critical transitions at both microscopic and macroscopic scales, establishing SSM-based reduction as a robust, interpretable tool for nonlinear networked systems with broad applicability to epidemiology, ecology, and engineered networks.
Read the full abstract ▾