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Wednesday 29 July

Astrophysics of Galaxies

Stellar photoionisation modelling in SYNTHESIZER

Aswin P. Vijayan, Stephen M. Wilkins, Sophie L. Newman et al. (+5 more)

Emission from photoionised gas surrounding young stellar populations ($H\text{II}$ regions) provides critical diagnostics of the physical conditions in star forming galaxies. This emission constrains the gas properties, the nature of ionising sources, and generates essential features for determining galaxy redshifts. To leverage spectroscopic observations to test galaxy formation models, it is essential to incorporate these emissions into synthetic datasets. Here, we present the integration of photoionised gas emission into the SYNTHESIZER package (https://synthesizer-project.github.io) and demonstrate its application. We quantify the impact of key modelling assumptions - including stellar population synthesis models, initial mass functions, ionisation parameter, gas density, geometry, abundance pattern, elemental depletion, and dust - on spectral diagnostics. Furthermore, we demonstrate the versatility of SYNTHESIZER through its application in different scenarios ranging from exploring emission in toy parametric models to large-volume cosmological simulations with realistic star formation and metal enrichment histories. Taken together, SYNTHESIZER provides a flexible, physically motivated framework to model stellar and nebular emissions, serving as a vital link between theory and observations in the era of next-generation spectroscopic missions.
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All authors Aswin P. Vijayan, Stephen M. Wilkins, Sophie L. Newman, Christopher C. Lovell, William J. Roper, Sabrina Berger, Thomas Harvey, Jack C. Turner

Quantum Physics

Coherent excitation of a two-state system by a Lorentzian field

Aida Shiroyan, Genko S. Vasilev and Nikolay V. Vitanov

We study the coherent excitation of a two-state quantum system by a field with a Lorentzian temporal envelope and constant carrier frequency. The associated differential equation admits an exact local representation in terms of confluent Heun functions. For the transition probability we develop a Dykhne-Davis-Pechukas (DDP) description based on the two relevant complex transition points and their interference. The DDP action is analyzed directly in the weak- and strong-coupling limits, yielding explicit asymptotic expressions for the oscillation phase, oscillation envelope, far-detuned line shape, and near-resonant behavior. In particular, the strong-coupling asymptotics imply a linewidth proportional to the inverse peak Rabi frequency for resonant odd-$\pi$ pulses, thereby exhibiting the power-narrowing characteristic of the Lorentzian pulse.
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High Energy Astrophysical Phenomena

On the triple nature of the PSR J0435+3233 system

Paulo C. C. Freire, Colin J. Clark, Cees G. Bassa et al. (+4 more)

The recent pulsar timing ephemeris of PSR J0435+3233 indicates that this millisecond pulsar (MSP) has a spin-down rate that is much higher than observed in other MSPs and challenges our understanding of the formation and evolution of MSPs. We propose that this system is a hierarchical triple, and that the high spin-down rate is caused by varying acceleration due to a tertiary in a wide orbit. We use pulsar timing methods with radio and gamma-ray observations of PSR J0435+3233 to determine the system properties. We find that a hierarchical triple timing model describes the timing observations of PSR J0435+3233 and that this results in the detection of gamma-ray pulsations back to the beginning of the Fermi Large Area Telescope (LAT) data in 2008. The intrinsic spin-down rate remains uncertain as it correlates with the parameters of the outer orbit, but large spin-down rates are excluded and the intrinsic rate is at least two orders of magnitude lower than the observed rate, in line with other Galactic MSPs. We identify a star located 11 mas from the pulsar position as the optical counterpart to the tertiary companion. From the 1.5-2.5 kpc distance and colours, we infer that the tertiary is a 1.2-solar mass F-type main-sequence star. Along with the pulsar binary, it orbits the common centre of mass with an eccentric (e ~ 0.6), wide (~70 yr) orbit that is likely seen at a low orbital inclination. We conclude that PSR J0435+3233 is a hierarchical triple system. We discuss the motivation and prospects for the continued study of this system. Spectral measurements of the outer star in addition to continued astrometric measurements will yield mass ratio and inclination estimates, while continued pulsar timing may yield a tighter constraint on violations of the Strong Equivalence Principle than are currently obtained from PSR J0337+1715.
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All authors Paulo C. C. Freire, Colin J. Clark, Cees G. Bassa, Guillaume Voisin, Rutger van Haasteren, Lars Nieder, Benjamin W. Stappers

Instrumentation and Methods for Astrophysics

Compton Polarimeter Prototype for the CUbesat Solar Polarimeter (CUSP) mission

Nicolas De Angelis, Andrea Alimenti, Riccardo Campana et al. (+41 more)

The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band (25-100 keV) by means of a dual-phase Compton polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star with its unprecedented sensitivity to solar flare polarization. CUSP is a project under development as part of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. In the frame of CUSP's Phase B, which started in December 2024, a flight-representative prototype of the Compton polarimeter has been developed and characterized with hard X-ray sources in the laboratory. This prototype consists of a 4$\times$4 central matrix of plastic scintillator bars surrounded by 4 strips of 8 elongated GAGG scintillators, respectively coupled to a multi-anode photomultiplier tube and arrays of avalanche photodiodes. These sensors are read out by custom front-end electronics based on MAROC-3A and SKIROC-2A ASICs with a Xilinx Artix 7 FPGA. The plastic scintillators act as scatterers, while the GAGG bars fully absorb the scattered photons. Coincident plastic-GAGG events allow for reconstructing the Compton scattering direction, whose distribution allows for inferring the polarization parameters of the source. We report here the measured performance of the polarimeter prototype using well-known radioactive isotopes and X-ray tubes, allowing us to assess the performance of our polarimeter prototype over the full 25-100 keV energy range.
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All authors Nicolas De Angelis, Andrea Alimenti, Riccardo Campana, Mauro Centrone, Giovanni De Cesare, Ettore Del Monte, Sergio Di Cosimo, Enrico Costa, Sergio Fabiani, Abhay Kumar, Pasqualino Loffredo, Giovanni Lombardi, Gabriele Minervini, Fabio Muleri, Paolo Romano, Alda Rubini, Enrico Silva, Paolo Soffitta, Giovanni Cucinella, Vito Di Bari, Simone Di Filippo, Andrea Negri, Massimo Perelli, Davide Albanesi, Valerio Campamaggiore, Giulia de Iulis, Andrea Del Re, Paolo Leonetti, Alessandro Zambardi, Ilaria Baffo, Pierluigi Fanelli, Costantino Zazza, Andrea Curatolo, Nicolas Gagliardi, Dario Modenini, Daniele Pecorella, Alice Ponti, Paolo Tortora, Valerio Vagelli, Daniele Brienza, Immacolata Donnarumma, Matteo Mergè, Emanuele Zaccagnino, Alessandro Turchi

Fluid Dynamics

Role of gravity on preferential clustering of microparticles in unsteady wake flows

Siddhi Arya and Partha S. Goswami

Direct numerical simulations are carried out for particle-laden flow over the cylinder to investigate preferential clustering of particles in an unbounded vertical channel flow. The flow is examined at Reynolds numbers Re=100 and 200 for varying particle Stokes number, particle loadings and Froude numbers to quantify the combined influence of particle inertia and gravitational settling on particle motion. The unladen flow exhibits the classical vortex shedding pattern observed in flow over bluff bodies at both Reynolds numbers. Reynolds number dependent wake width, wake recovery, and velocity-deficit evolution are observed, characterizing the coherent flow structures that govern particle dynamics. In particle-laden unsteady wake flows, the non-uniform particle distribution leads to formation of coherent voids and clusters, whose shape are directly correlated with background flow dynamics. Gravity modifies particle-fluid interaction, which leads to an increase in slip velocity, weakens vortex-induced particle clustering and promotes them to travel through vortices, resulting in a transition of the void shape from individual leaf-like structure to snake-like void zone and eventually into a nearly vertical void structure. In upstream region infront of the cylinder, inertial particles form a bow-shock-like structure whose extent increases with increase in Stokes number and finite Froude conditions. Voronoi based analysis combined with local Q values is used to investigate effect of gravity and inertia on particle distribution. The dimensionless settling velocity, St/Fr^2, is identified as the governing parameter controlling the evolution of void shape, normalized void cell area and the probability distribution of Voronoi cell areas. The effect of wake dynamics, particle inertia, and gravity is reported to jointly govern preferential clustering in bluff-body wakes.
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Instrumentation and Methods for Astrophysics

Testing of machine learning wavefront sensing algorithms on the Tiny Observatory for Telescope Optimization (TOTO) testbed

Sanchit Sabhlok, Solvay A. Blomquist, Maggie Y et al. (+16 more)

Phase retrieval techniques are utilized to correct low order wavefront aberrations originating from misalignments of the optical system in space based telescope concepts. Traditional phase retrieval involves observation of the Point Spread Function (PSF) and a diversity measurement, usually focus diversity although other measures are possible, to reconstruct the incident wavefront at the science detector. We consider a Machine Learning model trained originally on simulated data, and then augmented with real focus diversity data from the Tiny Observatory for Telescope Optimization (TOTO) testbed at the University of Arizona. We then compare the wavefront sensing performance of the Machine Learning model with known truth values of the generated dataset. The model predictions for low order Zernikes on TOTO data after training and validation show a reasonable agreement with the true Zernike coefficients.
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All authors Sanchit Sabhlok, Solvay A. Blomquist, Maggie Y, Kautz, Debstuti Biswas, Kevin Derby, Jaren N. Ashcraft, Hyukmo Kang, Simran Agarwal, Alexandra Kupersmith, Adam Schilperoort, Stephanie F. Rinaldi, Kelsey L. Miller, Kyle J. Van Gorkom, Corey Fucetola, Patrick Ingraham, Ewan S. Douglas, Heejoo Choi, Daewook Kim

Instrumentation and Methods for Astrophysics

Tiny Observatory for Telescope Optimization (TOTO): testing algorithms for autonomous on-orbit alignment for space-based telescope systems

Solvay A. Blomquist, Sanchit Sabhlok, Hyukmo Kang et al. (+11 more)

The Tiny Observatory for Telescope Optimization (TOTO) is an optical testbed designed to evaluate the efficacy of autonomously driven alignment algorithms for space-based telescope systems. For space-based missions, active control of the telescope alignment on-orbit offers potential to relax passive alignment requirements and reduce on-ground verification activities. TOTO is used to evaluate and verify simulation work of two primary alignment algorithms, Stochastic Parallel Gradient Descent (SPGD) and focus-diverse phase retrieval (FDPR). Previous simulation work has confirmed that by using SPGD for coarse alignment followed by focus-diverse phase retrieval for fine alignment, we can reach diffraction-limited performance on-orbit. This paper presents the results of the autonomous alignment algorithm of a Cassegrain telescope using TOTO. We report the current status of TOTO as well as preliminary results from SPGD and phase retrieval on the testbed using monochromatic light source to simulate an on-axis point source.
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All authors Solvay A. Blomquist, Sanchit Sabhlok, Hyukmo Kang, Maggie Y. Kautz, Simran Agarwal, Heejoo Choi, Alexandra Kupersmith, Adam Schilperoort, Kelsey L. Miller, Kyle J. Van Gorkom, Corey Fucetola, Patrick Ingraham, Ewan S. Douglas, Daewook Kim

Quantum Physics

Bosonic quantum communication beyond the thermal threshold

Francesco Anna Mele, Giuseppe Catalano, Marco Fanizza et al. (+2 more)

The quantum capacity of the bosonic thermal attenuator, which is given by the regularization of its coherent information, is unknown. The seminal work of Holevo and Werner established in 1999 the standard one-use lower bound obtained from input thermal states. We first prove that this long-standing lower bound is the exact supremum over all single-mode Gaussian states and then show that, crucially, a non-Gaussian state can do better. As a consequence, we prove positivity of the quantum capacity in a parameter region where the channel is not antidegradable, yet its coherent information optimized over single-mode Gaussian states vanishes. For example, with one thermal photon in the environment and at transmissivity $\eta=0.8$, the coherent information is non-positive for every single-mode Gaussian input. We give an explicit rank-two non-Gaussian state, supported on only six Fock levels, whose coherent information is certified to be at least $4.7\times10^{-4}$ qubits per channel use. This short witness is far from numerically optimal: a numerical optimization over fixed non-Gaussian families reaches at least $8.4\times 10^{-3}$ qubits per channel use at the same point. More generally, at $\nu=1$, using non-Gaussian inputs we certify positivity of the coherent information, and therefore of the quantum capacity, down to $\eta=0.7841$; by contrast, the channel is antidegradable, and hence has zero quantum capacity, for $\eta\leq0.75$. Overall, our work identifies new high-noise regimes in which bosonic quantum communication is possible.
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All authors Francesco Anna Mele, Giuseppe Catalano, Marco Fanizza, Vittorio Giovannetti, Ludovico Lami

Applied Physics

Phase noise analysis and control of VO$_2$-based relaxation type oscillators

Artem Litvinenko, Erbin Qiu, Sambit Ghosh et al. (+5 more)

VO$_2$-based relaxation oscillators form a rapidly developing field that finds applications in neuromorphic computing, Ising machines, and numerous signal processing concepts. These oscillators operate in a deeply nonlinear relaxation regime based on rapid phase transitions between insulating and metallic states in the VO$_2$ material. This process is governed by thermal effects, which lead to additional voltage fluctuations and contribute to a considerably wide spectral linewidth in the VO$_2$-based oscillator signal. In this work, we thoroughly study the phase noise in VO$_2$-based relaxation oscillators and demonstrate that the broadening of the generation spectrum linewidth at low oscillation frequencies is caused by an increased susceptibility to thermal fluctuations during the incubation phase. We explore the types of noise affecting oscillator stability and show that synchronization with an external square-wave signal improves the phase noise more effectively than a sinusoidal-shape injection locking signal.
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All authors Artem Litvinenko, Erbin Qiu, Sambit Ghosh, Juan Andres Hofer, Akash Kumar, Jong-Guk Choi, Ivan K. Schuller, Johan Åkerman

Biological Physics

Do ions have a coating in neuronal electrolytes under an electric field?

János Végh

Ions in electrolytes can have coatings and can combine into different complexes that significantly affects their size, mass, and transport features. Measuring such coatings of ions traveling in narrow, limited spaces inside biological objects is challenging. We assumed that the coating changes the size of the ion and that the speed of the complex may influence its composition. The original Stokes-Einstein relation for diffusion assumes a simple, spherical particle in a homogeneous Newtonian fluid. It was modified to describe an electric-field-driven drift. One possible application of the result is describing the propagation of axonal impulses, especially since soliton theory models it as a mechanical vibration, i.e., its speed changes rapidly. Hodgkin and Huxley measured the membrane current (due to axonal current) as a function of the clamping voltage, and they confirmed the linear dependence, that is, the independence of the ions' coating state from their speed.
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Fluid Dynamics

Kinetic Linear Stability Theory for High-Speed Compressible Flows: A High Performance Computing Framework

Irmak Taylan Karpuzcu, Deborah Levin and Vassilis Theofilis

Shock waves in high-speed compressible flows contain finite-thickness, high-gradient regions where the continuum assumption becomes questionable and translational non-equilibrium arises, including non-Maxwellian micro-velocity distributions. Classical shock stability analyses rely on Navier-Stokes or moment closures and cannot retain bi-modal velocity distributions inside the shock. We develop and apply, for the first time, a kinetic linear stability theory (kLST) for one-dimensional normal shocks by linearizing the Boltzmann-BGK equation about kinetic BE-BGK base flows. Perturbations are posed in reduced distribution functions, with macroscopic fields recovered by velocity-space moments, so the stability operator acts on the VDF rather than a closed continuum system. Verified against compressible Couette eigenvalue benchmarks near continuum, the framework is applied to argon shocks at $M_\infty=1.2$, $3.0$, and $4.0$. At low Mach number, where BE-BGK and Gilbarg-Paolucci profiles nearly coincide, the spectra recover stable continuous branches. At higher Mach number, comparing Maxwellian and non-equilibrium VDF-based eigenspectra shows that kinetic effects shift the spectrum toward less stable regions, so continuum predictions can miss important changes even when macroscopic profiles appear well resolved. For large high-Mach matrices–$O(10^5)$ unknowns and up to billions of nonzeros–we develop a parallel SLEPc/PETSc infrastructure using shift-and-invert Arnoldi with MUMPS LU for moderate sizes and Jacobi-Davidson (JD) with block-Jacobi ILU for the largest systems. Coupled spatial/micro-velocity sparsity causes severe LU fill-in, making direct solvers memory-limited and motivating JD. We compute kLST spectra for an $M_\infty=4.0$ shock with 281088 unknowns, to our knowledge the highest-Mach kinetic linear stability calculation reported for isolated finite-thickness shock layers.
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High Energy Astrophysical Phenomena

Radio Follow-Up of Einstein Probe Fast X-Ray Transients

Carmen Choza, Joe S. Bright, Francesco Carotenuto et al. (+3 more)

Fast X-ray transients (FXTs) are brief, luminous bursts of soft X-ray emission whose physical origins remain uncertain. The Einstein Probe (EP) mission has recently enabled prompt discovery of these events, providing opportunities for rapid multi-wavelength follow-up. We present a coordinated radio observing campaign targeting 20 FXTs detected by the EP in 2024. The core consists of 59 epochs with the Allen Telescope Array (ATA), sampling post-burst timescales from $\sim$1 to $\sim$65 days and reaching typical $3\sigma$ sensitivities of 0.6–1.5\,mJy across 1–8\,GHz. Two FXTs—EP240315a and EP241021a—have radio counterparts. For EP241021a, AMI-LA monitoring at 15.5\,GHz reveals a light curve peaking at $\sim$30 days with $F_{\nu}\approx1.0$\,mJy; equipartition analysis implies a Newtonian equipartition energy of $\sim3\times10^{49}$\,erg and a mildly relativistic on-axis solution with $\Gamma_{\rm on}\approx1.3$. Multi-frequency modelling of EP240315a, combining new VLA measurements with published MeerKAT, ATCA, and eMERLIN data, indicates highly relativistic early emission ($\Gamma\gtrsim3$) that decelerates with time, consistent with jetted outflow. The detections and ATA non-detections span luminosities overlapping the brightest GRB and relativistic tidal disruption event (TDE) afterglows, suggesting FXTs comprise a heterogeneous population including both relativistic and non-relativistic explosions. Under a GRB-like redshift prior, our $3\sigma$ ATA limits correspond to observer-frame specific-luminosity thresholds of $\sim10^{32}$–$10^{33}\,\mathrm{erg\ s^{-1}\ Hz^{-1}}$; for nearby events ($z\lesssim0.2$), $L_{\nu}\lesssim10^{30\text{--}31}\,\mathrm{erg\ s^{-1}\ Hz^{-1}}$. Planned ATA upgrades and next-generation arrays (SKA, DSA, ngVLA) will enable sensitive, population-level radio studies of the FXT radio sky.
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All authors Carmen Choza, Joe S. Bright, Francesco Carotenuto, Alex Pollak, Rob Fender, Andrew Siemion

Quantum Physics · Cross-listed from cs.IT

The Capacity Region of the Broadcast Channel with Non-Signaling Assistance

Yuhang Yao and Syed A. Jafar

The capacity region of the $K$-user discrete memoryless broadcast channel is fully characterized when non-signaling (NS) assistance is available to the transmitter and all $K$ receivers. The NS-assisted capacity region is shown to coincide with Sato's region, i.e., the region defined by sum-rate bounds over all subsets of messages, where each bound corresponds to full cooperation among that subset of receivers under a worst-case joint channel law consistent with the marginal channels.
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Fluid Dynamics · Cross-listed from math.NA

Comparison of a Parametric Physics-Informed Neural Network and a Tensorial Reduced-Order Model for the Shallow-Water Dam-Break Problem

Anton Myshak, Md Rezwan Bin Mizan and Ilya Timofeyev

We develop two parametric data-driven reduced models: a physics-informed neural network (PINN) and a non-intrusive tensorial reduced-order model (TROM), and apply both approaches to the parametrized one-dimensional shallow-water dam-break problem. Neither reduced model requires time integration: both learn a direct parameter-to-solution map from space, time, and dam-break parameters to the physical state, with the PINN providing predictions at arbitrary times and the TROM reconstructing solutions at the stored snapshot times. In addition, we demonstrate that it is essential to introduce shock-aware collocation to improve the robustness of the PINN model.
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Materials Science

Decoding the Micromagnetic Hamiltonian from Magnetic Fingerprints

Bradley J. Fugetta, Anqi Liu, Kai Liu et al. (+2 more)

Extracting intrinsic magnetic Hamiltonians directly from magnetometry is challenging due to the high dimensionality of the parameter space and the degeneracy induced by ensemble averaging. Here, we introduce a collection of deep convolutional neural networks (CNNs) to extract the full phenomenological micromagnetic Hamiltonian directly from the magnetic fingerprints encoded within First-Order Reversal Curves (FORCs). We validate this approach via closed-loop verification, re-creating the input magnetometry for both simulated and experimental FORCs. To mitigate false positives, we deploy an `Alice–Bob' parallel network that quantifies prediction uncertainty based on solely the information in FORCs without any additional ground-truth knowledge. This framework provides a robust, machine-learning-assisted approach to unravel the underlying spin behaviors in complex magnetic systems
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All authors Bradley J. Fugetta, Anqi Liu, Kai Liu, Amy Y. Liu, Gen Yin

Medical Physics

Rethinking AI in Medical Imaging: Assumptions, Reality, and Reframing; Towards Physician-Centered Agentic Reasoning

Arman Rahmim, Nourhan Bayasi, Xiaoxiao Li et al. (+2 more)

Medical imaging has served as primary proving ground for clinical AI, yet a decade of intense research has not translated into proportionate bedside impact. We argue that this gap is not primarily a product of insufficient algorithmic performance, inadequate regulation, or limited explainability. Rather, it reflects a structural misalignment, between how AI systems are designed and evaluated, and how clinical decisions are made. This work identifies 8 interconnected dimensions of this misalignment: 1) the dominance of pixel-only models in a multimodal clinical world; 2) the erosion of physician trust through opaque and inflexible systems; 3) the unfulfilled promise of foundation models in data-sparse medical domains; 4) the persistent bottleneck of non-shareable under-curated datasets; 5) the gap between validated algorithms and deployable clinical platforms; 6) the slow, unmonitored translation of evidence into routine practice; 7) the risk of AI displacing rather than extending physician judgment; and 8) the failure of prediction-centric AI to generate actionable, agentic clinical guidance. For each dimension, we reframe the problem and propose a path forward, culminating in a vision of physician-centered AI solutions with agentic reasoning that extend, rather than replace, clinical judgment.
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All authors Arman Rahmim, Nourhan Bayasi, Xiaoxiao Li, Babak Saboury, Fereshteh Yousefirizi

Fluid Dynamics

A sub-grid-scale model for polydisperse bubbly flows with heat and mass transfer

Anand Radhakrishnan and Spencer H. Bryngelson

Ensemble-averaged models of polydisperse bubbly flows require statistics of the evolving bubble population. Prior quadrature-based moment formulations close bubble pressure with a polytropic relation that omits heat and mass transfer at the bubble wall. We formulate constant-transfer equations for bubble pressure and vapor mass within a conditional hyperbolic quadrature method. Second-order conditional inversion produces four joint radius–radial-velocity nodes per equilibrium-radius bin. Bubble pressure and vapor mass are advanced at each node. The node values close the ensemble-averaged flow equations without adding mixed pressure or vapor-mass moments to the transported moment set. The model is implemented in MFC. Monte Carlo calculations verify the evolution of quadrature nodes and the mean bubble variables for a harmonically forced population. Bubble-screen calculations quantify closure error as the equilibrium radius is discretized and the initial distributions vary. The constant-transfer calculation does not exhibit the high-frequency pressure oscillations observed with the polytropic closure under the conditions considered. 3D bubble-screen calculations give a 1.5% relative root-mean-square error between the Euler–Euler center pressure and the mean of 40 volume-averaged Euler–Lagrange realizations.
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Materials Science

Structure and thermodynamic stability of $\beta$-Ga$_2$O$_3$ surfaces

Konstantin Lion and Claudia Draxl

We present a comprehensive first-principles investigation of all symmetrically inequivalent low-index surfaces of $\beta$-Ga$_2$O$_3$, examining their structural properties and thermodynamic stability across experimentally relevant growth conditions. Using density-functional theory with both the semi-local functional PBEsol and a modified PBE0 hybrid functional with 26% exact exchange, denoted PBE0(0.26), we calculate surface free energies for the (010), (100), (001), ($\bar{2}01$), (110), (111), and ($11\bar{1}$) orientations, including the effects of harmonic vibrational contributions and varying oxygen chemical potentials. We demonstrate that the energetic ordering remains consistent across computational approaches and that the vibrational contributions remain below 0.2 J/m$^2$ up to temperatures of 1000 K. A coordination-based model that correlates surface stability with the density of under-coordinated atoms reveals that under-coordinated oxygen atoms and tetrahedral Ga sites substantially destabilize surfaces, while exposed under-coordinated octahedral Ga atoms serve as indicators of surface stability. Our thermodynamic analysis shows that stoichiometric terminations dominate over nearly the entire range of chemical potentials relevant for $\beta$-Ga$_2$O$_3$ stability, while non-stoichiometric terminations emerge only under extreme reducing or oxidizing conditions. Notably, we predict the formation of stable Ga-rich terminations resembling Ga adlayers for the (100) and ($\bar{2}01$) surfaces under highly reducing conditions.
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Materials Science

Optimization of Epitaxial Mn4N Thin Films Grown by Sputtering for Spintronic Applications

Teodor Apetrei, Emre Demiroglu, Caner Deger et al. (+2 more)

Ferrimagnetic Mn4N has recently emerged as a promising rare-earth-free platform for spintronic devices due to its low magnetization, high domain wall mobility, and strong anomalous Hall response. However, the realization of thin films with robust perpendicular magnetic anisotropy (PMA) and spin-orbit torque (SOT) functionality through scalable deposition techniques remains a significant challenge. In this work, we systematically investigate the growth of Mn4N thin films by reactive magnetron sputtering and determine the conditions required to achieve high-quality films suitable for SOT applications. We demonstrate that epitaxial, single-crystalline Mn4N films with strong PMA can be obtained on MgO(100), whereas films deposited on SrTiO3(100) exhibit a textured structure. The optimized films show square-shaped hysteresis loops with high remanence, large and tunable coercivity, and a pronounced anomalous Hall effect. By combining structural, magnetic, and magnetotransport characterization with density functional theory calculations, we reveal that epitaxial strain plays a key role in tuning magnetic anisotropy, while also showing that it is not the only contributing factor. In particular, our results emphasize the importance of interfacial effects in stabilizing PMA. Finally, we demonstrate efficient current-induced magnetization switching in Mn4N/Pt bilayers, confirming strong interfacial spin transparency. These findings establish sputtered Mn4N as a promising and versatile material platform for energy-efficient spin-orbitronic devices.
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All authors Teodor Apetrei, Emre Demiroglu, Caner Deger, Can Onur Avci, Silvia Damerio

High Energy Physics (Theory)

A Darboux-Theorem-Based Derivation of Geometric Structures in Various Non-Abelian Gauge Theories

Eugen-Mihaita Cioroianu and Stefan-Sabin Manolescu

This paper illustrates the straightforward application of the Faddeev–Jackiw approach to several non-Abelian gauge theories, namely, the Freedman–Townsend, Yang–Mills, and non-Abelian BF models, as well as a nonlinear theory of BF type. For each theory, the procedure determines the phase space and its symplectic structure, the coisotropic constraint submanifold, the Hamiltonian, and the reducibility properties of the constraints. By combining these results with the Dirac conjecture, one reconstructs through direct computation the corresponding Lagrangian gauge transformations and their reducibility structure. The analysis provides a unified and efficient derivation of the principal Hamiltonian and Lagrangian gauge structures of these non-Abelian theories.
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Instrumentation and Methods for Astrophysics

PhoPS: An automated photometric pipeline for survey-era astronomy

Orhan Erece and Yucel Kilic

Modern astronomical surveys produce large volumes of imaging data together with highly accurate astrometric and photometric reference catalogues, creating a need for automated, robust, and instrument-independent reduction pipelines. We present PhoPS (Photometry and Astrometry of Point Sources), an open-source Python pipeline for fully automated astrometric calibration and photometric reduction of stellar and moving Solar System targets. PhoPS dynamically generates local Gaia DR3 astrometric index files propagated to the observation epoch, eliminating the need for pre-installed index collections while improving astrometric accuracy. Photometric calibration uses a field-dependent zero-point model based on Random Sample Consensus (RANSAC) linear regression to account for spatial systematics such as vignetting and detector non-uniformities. Astrometric performance was evaluated using 141672 matched measurements from 840 images obtained with the 1 m TUG100 telescope. Epoch propagation reduced the clipped N-weighted total RMS residual from 0.284 arcsec to 0.241 arcsec, a 15.0% improvement. The photometric uncertainty model was validated using 203 reference stars and 92980 measurements. Normalized residuals are centered near zero, but their widths are magnitude dependent, with sigma values of 2.069 for bright stars (10 <= G < 13), 1.129 for intermediate-brightness stars (13 <= G < 16), and 0.698 for faint stars (16 <= G < 18), indicating underestimated uncertainties for the brightest stars and conservative uncertainties for the faintest stars. PhoPS provides a lightweight, cross-platform solution for automated astronomical image reduction and is well suited to asteroid light-curve analysis, stellar variability studies, and the diagnosis of observational systematics.
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Cosmology and Nongalactic Astrophysics

Lyman-$\alpha$ forest holography: 3D predictions from 1D measurements

J. Chaves-Montero, A. Font-Ribera, J. Aguilar et al. (+68 more)

Cosmological analyses of Lyman-$\alpha$ forest clustering rely on either one-dimensional correlations along individual sightlines or three-dimensional correlations between different sightlines. Because these observables probe the matter distribution on very different scales, they have traditionally been analyzed independently. In this work, we bridge this gap using ForestFlow, an emulator trained on a suite of cosmological hydrodynamical simulations that provides a unified description of Lyman-$\alpha$ forest clustering from linear to nonlinear scales. This framework enables us to determine the range of three-dimensional clustering models compatible with the DESI one-dimensional flux power spectrum ($P_{\rm 1D}$). The resulting predictions successfully reproduce the large-scale clustering measured by the DESI BAO analysis and provide physically motivated priors on nonlinear clustering that are used in a companion paper presenting the full-shape analysis of the DESI DR2 Lyman-$\alpha$ forest. We validate our methodology using the large-volume, high-resolution hydrodynamical simulation ACCEL-2, demonstrating excellent agreement across the full range of scales considered. Finally, we combine constraints from the $P_{\rm 1D}$ and BAO analyses on the parameter combinations $b_\delta \sigma_8$ and $b_\eta f \sigma_8$, finding that the two probes provide comparable constraining power while exhibiting complementary parameter degeneracies. Our results establish a direct connection between one- and three-dimensional Lyman-$\alpha$ forest measurements through ForestFlow, an approach we term Lyman-$\alpha$ holography by analogy with the reconstruction of higher-dimensional structure from lower-dimensional information.
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All authors J. Chaves-Montero, A. Font-Ribera, J. Aguilar, S. Ahlen, E. Armengaud, A. Aviles, F. Beutler, D. Bianchi, S. Blasby, D. Brooks, K. Carrion, Z. Chen, T. Claybaugh, A. Cuceu, A. de la Macorra, A. Dey, P. Doel, W. Elbers, S. Ferraro, L. Flores, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, D. Gonzalez, A. X. Gonzalez-Morales, R. Gsponer, G. Gutierrez, C. Hahn, M. Herbold, H. K. Herrera-Alcantar, K. Honscheid, M. Ishak, S. Juneau, N. V. Kamble, D. Kirkby, A. Kremin, A. Lambert, M. Landriau, L. Le Guillou, K. Lodha, Z. Lukić, M. Manera, P. Martini, A. Meisner, R. Miquel, P. Mukherjee, A. Muñoz-Gutiérrez, S. Nadathur, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, H. Pulido-Hernández, I. Pérez-Ràfols, C. Ravoux, J. Rohlf, A. J. Rosado-Marín, G. Rossi, R. Ruggeri, M. F. Ruiz-Herrera Bernal, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, F. Sinigaglia, G. Tarlé, W. Turner, B. A. Weaver, H. Zhang

Cosmology and Nongalactic Astrophysics

CoLoRe-2LPT: Lyman-$\alpha$ mock catalogues for the validation of DESI cosmological analyses

M. F. Ruiz-Herrera Bernal, S. Avila, A. Font-Ribera et al. (+90 more)

The Lyman-$\alpha$ (Ly$\alpha$) forest has become a crucial probe for studying the large-scale structure of the universe at high redshift ($z > 2$), providing powerful constraints on Baryon Acoustic Oscillations (BAO) and the full-shape (FS) clustering of matter. As a key ingredient for upcoming BAO and FS analyses, we present a new generation of fast cosmological Ly$\alpha$ mocks based on second-order Lagrangian perturbation theory (2LPT). These new mocks significantly improve upon previous log-normal approaches, both at accurately capturing small scale clustering and at recovering the non-linear broadening of the BAO peak. They are able to reproduce Ly$\alpha$ statistics within $10\%$ of the latest DESI measurement; including the Ly$\alpha$ bias and the redshift-space distortion $\beta$ parameter, mean transmitted flux, and 1D power spectrum. The corresponding quasar (QSO) clustering is also improved with respect to previous approaches, calibrated against high-resolution Abacus simulations, recovering the observational QSO linear bias to less than $5\%$ and improving redshift-space distortions via 2LPT velocities and the addition of Fingers-of-God effects. Furthermore, these mocks incorporate high column density systems and metal lines, allowing us to explore the effects and systematics induced by these astrophysical contaminants. This new set of mocks has been key for enhancing the modeling and validation of the DESI DR2 Ly$\alpha$ full shape cosmological analysis. This work provides a physically motivated and computationally efficient tool for simulating current and next-generation Ly$\alpha$ surveys and validating FS and BAO analysis.
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All authors M. F. Ruiz-Herrera Bernal, S. Avila, A. Font-Ribera, H. K. Herrera-Alcantar, D. Alonso, A. Cuceu, L. Casas, F. Sinigaglia, J. Aguilar, S. Ahlen, O. Alves, U. Andrade, E. Armengaud, A. Bault, F. Beutler, D. Bianchi, M. Bonici, A. Brodzeller, D. Brooks, A. Carnero Rosell, J. Chaves-Montero, Z. Chen, Y. Cho, T. Claybaugh, K. S. Dawson, A. de la Macorra, A. Dey, W. Elbers, S. Ferraro, J. E. Forero-Romero, G. Gambardella, S. Gontcho A Gontcho, D. Gonzalez, A. X. Gonzalez-Morales, C. Gordon, R. Gsponer, G. Gutierrez, J. Guy, C. Hahn, M. Herbold, K. Honscheid, M. Ishak, S. Jos, S. Juneau, N. V. Kamble, T. Karim, D. Kirkby, A. Kremin, M. Landriau, A. Leauthaud, Q. Li, W. Liu, K. Lodha, O. Manasoiu, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Morawetz, P. Mukherjee, A. Muñoz-Gutiérrez, S. Nadathur, G. Niz, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, J. Pan, M. Pellejero Ibanez, W. J. Percival, C. Poppett, F. Prada, H. Pulido-Hernández, A. Pérez-Fernández, I. Pérez-Ràfols, C. Ravoux, J. Rohlf, G. Rossi, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, H. Seo, J. Silber, T. Simon, M. Siudek, G. Tarlé, W. Turner, R. Vaisakh, M. Vargas-Magaña, B. A. Weaver, H. Yang, H. Zhang

Cosmology and Nongalactic Astrophysics

Validation of the DESI DR2 Ly$\alpha$ forest full-shape analysis

M. Herbold, A. Cuceu, P. Martini et al. (+100 more)

We present the validation of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) Lyman-$\alpha$ (Ly$\alpha$) forest full-shape analysis. This analysis combines three-dimensional Ly$\alpha$ forest auto-correlations and cross-correlations with quasars to extract information from both the baryon acoustic oscillation (BAO) feature and the broadband clustering signal, with primary emphasis on the Alcock-Paczynski (AP) measurement. Compared to the DESI DR1 analysis, the DR2 validation uses substantially larger and more realistic mock datasets, including CoLoRe 2LPT and AbacusSummit Ly$\alpha$ forest simulations. The modeling framework is also improved through analytic marginalization over small scales ($<10$ $h^{-1}$Mpc) and the impact of ultraviolet background fluctuations. The validation program was completed prior to unblinding and defines quantitative requirements for the cosmological parameters of interest, which are evaluated using hundreds of mock realizations. We further test the analysis through independent fits to the auto- and cross-correlations, multiple catalog splits, and a broad suite of analysis and modeling variations applied to both mocks and blinded observational data. We find that the BAO and AP parameters satisfy all validation requirements and remain stable across all tests. In contrast, mock studies reveal a significant bias in the inferred growth-rate parameter $f\sigma_8$, leading us to exclude this measurement from the final analysis. The consistency across mocks, data splits, and robustness tests demonstrates that the DR2 Ly$\alpha$ full-shape analysis provides a reliable and substantially improved broadband AP measurement over previous Ly$\alpha$ forest studies.
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All authors M. Herbold, A. Cuceu, P. Martini, H. K. Herrera-Alcantar, J. Guy, C. Gordon, O. Manasoiu, J. Aguilar, S. Ahlen, O. Alves, U. Andrade, E. Armengaud, S. Avila, A. Aviles, A. Bault, F. Beutler, D. Bianchi, M. Bonici, A. Brodzeller, D. Brooks, A. Carnero Rosell, E. Chaussidon, J. Chaves-Montero, Z. Chen, T. Claybaugh, K. S. Dawson, A. de la Macorra, A. Dey, W. Elbers, V. A. Fawcett, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, G. Gambardella, S. Gontcho A Gontcho, D. Gonzalez, A. X. Gonzalez-Morales, R. Gsponer, G. Gutierrez, B. Hadzhiyska, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, S. Jos, S. Juneau, N. V. Kamble, N. G. Karaçayl{\i}, T. Karim, R. Kehoe, D. Kirkby, F.-S. Kitaura, A. Kremin, O. Lahav, M. Landriau, J. Lasker, L. Le Guillou, A. Leauthaud, M. E. Levi, Q. Li, W. Liu, K. Lodha, M. Manera, A. Meisner, R. Miquel, J. Morawetz, J. Moustakas, P. Mukherjee, A. Muñoz-Gutiérrez, S. Nadathur, G. Niz, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, J. Pan, M. P. Ibanez, W. J. Percival, F. Prada, H. Pulido-Hernández, A. Pérez-Fernández, I. Pérez-Ràfols, C. Ravoux, J. Rohlf, G. Rossi, R. Ruggeri, M. F. Ruiz-Herrera Bernal, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, H. Seo, J. Silber, T. Simon, F. Sinigaglia, M. Siudek, G. Tarlé, W. Turner, R. Vaisakh, M. Vargas-Magaña, B. A. Weaver, M. Wolfson, H. Yang, H. Zhang

Cosmology and Nongalactic Astrophysics

DESI DR2 Results IV: Alcock-Paczyński Measurements from the Lyman Alpha Forest and Cosmological Constraints

DESI Collaboration: A. G. Adame, J. Aguilar, S. Ahlen et al. (+151 more)

We present Alcock-Paczyński (AP) measurements from the full shape of Lyman-$\alpha$ (Ly$\alpha$) forest correlation functions measured from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI). Our measurements include information from the Ly$\alpha$ forest auto-correlation and its cross-correlation with quasars. We constrain the AP effect with $1\%$ precision at an effective redshift $z_\mathrm{eff}=2.33$, which is twice as tight as the Baryon Acoustic Oscillation (BAO) constraint from the same data. When using the joint Ly$\alpha$ AP and BAO results, we measure the ratios $D_\text{H}(z_\mathrm{eff})/r_\text{d}=8.600 \pm 0.066$ and $D_\text{M}(z_\mathrm{eff})/r_\text{d}=39.32 \pm 0.33$, where $D_\text{M}$ is the transverse comoving distance, $D_\text{H}$ is the Hubble distance, and $r_\text{d}$ is the sound horizon at the drag epoch. Assuming $\Lambda$CDM, Ly$\alpha$ forest measurements combined with a nucleosynthesis prior produce a constraint on the Hubble constant $H_0=66.5\pm1.3\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$. The Ly$\alpha$ AP result corresponds to a matter fraction constraint $\Omega_\text{m}=0.325\pm0.018$ in $\Lambda$CDM, which is $1.4\sigma$ higher than DESI BAO. This impacts the DESI results relative to the Cosmic Microwave Background (CMB), slightly reducing their discrepancy from $2.4\sigma$ to $2.2\sigma$. We present updated constraints on extended models using the joint DESI DR2 BAO and Ly$\alpha$ forest full shape data, together with external data sets. When considering a time-evolving dark energy equation of state parametrized by $w_0$ and $w_a$, we find it is preferred over $\Lambda$CDM at $2.7\sigma$ for the combination of DESI and CMB data, and at $3.2\sigma$ when also including supernovae. With the new Ly$\alpha$ AP measurement, DESI provides its most precise anchor for the expansion history at $z > 1$ in the matter-dominated Universe.
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All authors DESI Collaboration: A. G. Adame, J. Aguilar, S. Ahlen, O. Alves, A. Anand, U. Andrade, E. Armengaud, S. Avila, A. Aviles, P. Bansal, A. Bault, J. R. Bermejo-Climent, F. Beutler, D. Bianchi, C. Blake, S. Blasby, M. Bonici, S. Brieden, A. Brodzeller, D. Brooks, A. Carnero Rosell, K. Carrion, L. Casas, F. J. Castander, E. Chaussidon, J. Chaves-Montero, D. Chebat, X. Chen, Z. Chen, Y. Cho, T. Claybaugh, A. Cuceu, T. M. Davis, K. S. Dawson, R. de Belsunce, A. de la Macorra, J. Della Costa, A. Dey, M. Doshi, H. Ebina, D. J. Eisenstein, W. Elbers, G. Farren, V. A. Fawcett, E. Fernández-García, S. Ferraro, A. Font-Ribera, D. Forero-Sánchez, J. E. Forero-Romero, C. S. Frenk, G. Gambardella, C. Garcia-Quintero, L. H. Garrison, H. Gil-Marín, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, C. Gordon, D. Green, R. Gsponer, G. Gutierrez, J. Guy, B. Hadzhiyska, C. Hahn, S. He, M. Herbold, H. K. Herrera-Alcantar, M.-F. Ho, K. Honscheid, J. Hou, D. Huterer, V. Iršič, M. Ishak, J.-Q. Jiang, S. Jos, S. Juneau, N. V. Kamble, N. G. Karaçayl{\i}, T. Karim, D. Kirkby, A. Kremin, A. Krolewski, O. Lahav, C. Lamman, M. Landriau, J. Lasker, J.M. Le Goff, L. Le Guillou, A. Leauthaud, Q. Li, W. Liu, K. Lodha, Y. Luo, O. Manasoiu, M. Manera, P. Martini, M. Maus, A. Meisner, R. Miquel, J. Morawetz, J. Moustakas, E. Mueller, P. Mukherjee, A. Muñoz-Gutiérrez, A. D. Myers, S. Nadathur, J. Najita, G. Niz, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, J. Pan, M. P. Ibanez, W. J. Percival, A. Porredon, F. Prada, H. Pulido-Hernández, A. Pérez-Fernández, I. Pérez-Ràfols, A. Raichoor, M. Rashkovetskyi, J. Ratajczak, C. Ravoux, A. Robertson, A. Rocher, J. Rohlf, A. J. Ross, G. Rossi, R. Ruggeri, M. F. Ruiz-Herrera Bernal, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, H. Seo, A. Shafieloo, R. Sharples, J. Silber, T. Simon, F. Sinigaglia, M. Siudek, T. Tan, G. Tarlé, W. Turner, R. Vaisakh, M. Vargas-Magaña, B. A. Weaver, M. Wolfson, H. Yang, J. Yu, C. Yèche, H. Zhang, Y. Zhang, R. Zhao, R. Zhou

Mesoscale and Nanoscale Physics

Fluctuation electrodynamics of quantum capacitance in electron bilayers

Dmitry Zverevich, Alberto F. Morpurgo and Alex Levchenko

Capacitance provides a thermodynamic probe of interacting electrons. It characterizes the energy cost of transferring charge between conductors, which, in low-dimensional systems, is governed by exchange and correlation effects in addition to electrostatic contributions. We develop a theory of the quantum capacitance of electron double layers, semiconductor quantum wells as well as monolayer and bilayer graphene devices, focusing on the contribution generated by interlayer correlations. Within a functional-integral formulation we show that the separation-dependent part of the ground-state energy is, at the level of ring diagrams, exactly the nonretarded Lifshitz expression for the van der Waals energy of two conducting sheets, with reflection amplitudes built from the layer polarizabilities. The interlayer correction to the inverse capacitance is the second density derivative of this energy: a Casimir compressibility. The zero-point fluctuations that generate Casimir forces between mirrors are here the coupled plasmons of the bilayer, and their contribution to the capacitance is obtained in closed form; its sign shows that interlayer correlations oppose charging at high density. A Gell-Mann-Brueckner analysis gives the high-density limit in terms of universal functions. For graphene we find that monolayers behave like the electron gas, while bilayer graphene is anomalous: interband screening suppresses the correction by orders of magnitude and, within the two-band model, can even reverse its sign in the experimentally relevant range of separations. We delineate the limits of the theory, identifying the dilute Wigner-crystal regime and electron-hole double layers near exciton condensation as regimes where the capacitance becomes a probe of interlayer pairing.
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Biological Physics

Continuous Game of Life: cell emergence and self-organization at the edge of growth

Alexandre Guillet and Frank Jülicher

Conway's Game of Life shows that simple rules can generate a rich diversity of emerging structures. This cellular automaton has been translated to continuous space by Rafler (2011) in a simulation called SmoothLife. The isotropic rule of this continuous Game of Life generates patterns whose beauty has attracted the attention of a growing community at the intersection of science and computer art. We study a minimal variant of this model, continuous in space and time, that generates cell-like patterns capable of self-replicating, gliding and disappearing. The phenomenology of these unit patterns is reported and related to homogeneous-state bifurcations, symmetry breaking, observed shape instabilities, finite-amplitude morphological changes, and a dilute-to-dense transition associated with cell proliferation. Its mapping onto a large reaction-diffusion system is interpreted in terms of homeostatic concentrations of morphogens, regulated by the nonlinear survival rule and generated through a cell-sourced cascade of auxiliary reactions. Introducing a global conservation law that limits resource availability causes the system to self-organize at this dilute-to-dense transition, which we call the edge of growth. A further exploration of parameter space reveals a variety of phases and the richness of life-like morphologies organized around this edge. Resemblance to biological processes such as division, motility, and death, together with a concise formulation and numerical implementation, makes the continuous Game of Life an appealing model system for investigating the emergence and self-organization of life-like patterns.
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Materials Science

PEDOT:PSS-Coated Magnetoelastic Sensors for Highly Sensitive Wireless Humidity Sensing

Wenderson R. F. Silva, Robson C. O. Guedes, Gilberto Rodrigues-Junior et al. (+3 more)

Magnetoelastic (ME) resonators provide an attractive platform for passive and wireless sensing, particularly for monitoring relative humidity (RH) in sealed or hard-to-access environments. In this work, we introduce ME humidity sensors functionalized with poly(3,4-ethylenedioxythiophene) sulfonate (PEDOT), marking the first application of this conductive polymer in ME-based humidity sensing. PEDOT films were deposited onto Metglas resonators via a simple drop-casting process, producing uniform and mechanically stable coatings. Comprehensive structural and morphological characterization by SEM, EDX, Raman spectroscopy, AFM/KPFM, and XRD confirmed the structural integrity of the polymer and revealed humidity-induced swelling of the PSS-rich domains, accompanied by enhanced polymer-chain mobility and an increase in the lamellar spacing from 23.5 Å to 24.2 Å at 95% RH. These structural changes directly affected the dynamic response of the resonators, leading to a systematic resonance-frequency downshift driven by the combined effects of water adsorption, mass loading, and viscoelastic damping. The optimized device achieved a sensitivity of 155 Hz/% RH in the 20 - 70% RH range, outperforming previously reported ME humidity sensors, while exhibiting a resolution better than 0.1% RH together with excellent response and recovery times. These results establish PEDOT as a highly effective functional coating for magnetoelastic humidity sensors and demonstrate a simple, low-cost, wireless sensing platform with high sensitivity and strong potential for practical environmental and industrial monitoring applications.
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All authors Wenderson R. F. Silva, Robson C. O. Guedes, Gilberto Rodrigues-Junior, Eduarda P. M. Campos, Angelo Malachias, Joaquim B. S. Mendes

Mathematical Physics · Cross-listed from math.CO

Self-avoiding polygons on a three-row square-lattice strip

Michael von Thaden

We give a closed formula for the number $p^{S_2}(n)$ of self-avoiding polygons (SAPs) of length $n$ on the strip $S_2:=\mathbb{Z}\times\{0,1,2\}$, together with closed formulas for those subtypes of SAPs which are determined by the numbers of vertical steps in their leftmost and rightmost columns. For the subtype whose leftmost and rightmost columns each contain two vertical steps, we also derive an alternative representation as a binomial sum. Our derivation is elementary: it is purely combinatorial and geometric and avoids generating functions. Comparing the two representations yields a new geometric proof of an identity arising in Larsen's treatment \cite{L07} of a problem posed by Gessel \cite{G95}. Finally, we show that this subtype of SAPs is closely connected to the sequence A007909. More precisely, for $m\geq0$, the number of these SAPs whose leftmost and rightmost columns each contain two vertical steps and whose length equals $2m+6$ is given by the term of this sequence with index $m$, which thereby acquires a geometric interpretation alongside the compositions it enumerates.
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General Physics

Multiplicity of Massive Stars at Low Metallicity: Early Results from the BLOeM Campaign

T. Shenar, J. Bodensteiner, M. Abdul-Masih et al. (+73 more)

Massive stars at low metallicity (Z) play a central role in shaping the high-redshift Universe, yet their multiplicity remains poorly constrained. The Binarity at Low Metallicity (BLOeM) campaign is a two-year survey of 929 stars in the Small Magellanic Cloud with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument at ESO's Very Large Telescope, providing the first large-scale spectroscopic monitoring of massive stars at low Z (1/5 solar). Analysis of the initial nine epochs reveals high intrinsic binary fractions (>70%) on the main sequence and a steep decline in evolved objects. Analysis of the full dataset will yield orbital solutions, identify black-hole companions, and allow a derivation of the initial mass function for single and binary stars at low Z.
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All authors T. Shenar, J. Bodensteiner, M. Abdul-Masih, F. Backs, S. R. Berlanas, J. M. Bestenlehner, A. Bobrick, D. M. Bowman, N. Britavskiy, P. A. Crowther, K. Deshmukh, M. Fabry, M. Gieles, A. Gilkis, G. González i Torà, G. Gräfener, M. Gull, Y. Götberg, C. Hawcroft, V. Hénault-Brunet, A. Herrero, G. Holgado, R. G. Izzard, S. Janssens, H. Jin, V. M. Kalari, Z. Katabi, A. de Koter, J. Klencki, B. Kubátová, J. Kubát, N. Langer, T. Lechien, D. Lennon, R. Lefever, B. Ludwig, L. Mahy, J. Maíz Apellániz, I. Mandel, A. Mang Román, G. Maravelias, P. Marchant, A. Menon, F. Najarro, A. O'Grady, L. Oskinova, R. Ovadia, L. R. Patrick, D. Pauli, M. Pawlak, M. Bernini Peron, A. Picco, V. Ramachandran, M. Renzo, D. F. Rocha, H. Sana, A. A. C. Sander, T. Sayada, A. Schootemeijer, F. R. N. Schneider, R. Seeburger, K. Sen, S. Shahaf, S. Simón-Díaz, M. Stoop, S. Toonen, F. Tramper, R. Valli, P. Van Daele, J. Th. van Loon, L. van Son, A. Vigna-Gómez, J. I. Villaseñor, J. S. Vink, C. Wang, X.-T. Xu