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Tuesday 4 August

Solar and Stellar Astrophysics

A comparison of best fits obtained in white dwarf asteroseismology using the WDEC and the LPCODE

Agnès Bischoff-Kim

We perform the asteroseismic fitting of 4 DAVs using a grid of WDEC models with chemical pro- files that closely mimic those of the LPCODE models and compare them with published asteroseis- mic fitting results using the LPCODE (Romero et al. 2017). These 4 objects are KIC 11911480, J113655.17+040952.6, KIC 4552982, and GD1212. The similarities in the results in those controlled experiments point to a consistency in the models. Given similar input, the LPCODE and the WDEC make similar models and calculate similar periods. We further perform the asteroseismic fitting of the same 4 DAVs by relaxing the constraints on the chemical profiles. We explore the effects of different methods for weighing the modes when calculating the goodness of fit of the models, as well as the effect of only including a subset of the known period spectrum. Such numerical experiments can help place recent and future efforts in pipeline fitting of numerous DAVs and DBVs using the WDEC on firmer footing (Hall et al. 2023).
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Quantum Physics

Applications of Spin-Dependent Generalized Squeezing in Hybrid Spin-Oscillator Quantum Processors

Kai Shinbrough, Donovan J. Webb, Iver R. Øvergaard et al. (+4 more)

Generalized squeezing interactions are foundational to quantum optics, and have recently come under experimental control in hybrid spin-oscillator quantum processors [O. Băzăvan, et al., Nat. Phys. 22, 757 (2026); S. Saner, et al., Phys. Rev. X 16, 021049 (2026)]. These interactions open the door for new applications in the processing of discrete- and continuous-variable quantum information, four of which we propose and investigate in this work: geometric phase gates mediated by spin-dependent generalized squeezing acting on two spins and a common oscillator; genuine N-body spin interactions mediated by individually addressed spin-dependent generalized squeezing; oscillator thermometry via spin readout; and the preparation of high-fidelity quantum states of the oscillator via spin-dependent generalized squeezing and mid-circuit measurement. A unifying feature of these applications is the geometric phase induced by generalized squeezing interactions, which is nonlinear in the Fock occupation of the oscillator and the interaction order of the generalized squeezing. This work provides a foundation for fast, high-fidelity discrete- and continuous-variable quantum computation and sensing in the hybrid spin-oscillator platform via generalized squeezing.
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All authors Kai Shinbrough, Donovan J. Webb, Iver R. Øvergaard, Oana Băzăvan, Sebastian Saner, Christopher J. Ballance, Raghavendra Srinivas

Earth and Planetary Astrophysics

JWST Transmission Spectroscopy of TOI-3235 b: Challenges in Constraining Giant Planet Atmospheres Around M Dwarfs Amid Stellar Contamination

Zoe Ko, Néstor Espinoza, Andrés Jordán et al. (+7 more)

Giant planets orbiting low-mass M dwarfs challenge current planet formation theories, which predict that such planets are unlikely to form. Characterizing their atmospheres can provide key insight into their origins, but analysis is complicated by stellar contamination in transmission spectra. We present a JWST/NIRSpec PRISM transmission spectrum of TOI-3235 b, a 604 K, 0.665 Jupiter-mass giant planet orbiting a 0.39 Solar-mass M dwarf. We apply a hierarchical retrieval framework incorporating an atmospheric model, a parametric stellar contamination model, and a Gaussian process (GP) to capture residual structure not explained by these deterministic components. We find that the inferred atmospheric properties are model-dependent: retrievals that treat stellar contamination deterministically yield a constrained CH4 abundance corresponding to a sub-solar metallicity that would challenge standard expectations from both core accretion and gravitational instability, along with potentially elevated CO and CO2 abundances that would require chemical disequilibrium. However, residual wavelength-correlated structure suggests the deterministic model is incomplete. Including a GP to marginalize over this structure broadens the atmospheric posterior distributions, preventing robust constraints on the atmospheric composition and highlighting the challenge of characterizing giant planet atmospheres around M dwarfs. We demonstrate that an eclipse observation could clarify these model-dependent ambiguities: detected emission features would constrain the planet's metallicity and test formation scenarios, while a featureless spectrum would confirm stellar contamination dominates the transmission spectrum, providing an empirical M dwarf contamination spectrum.
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All authors Zoe Ko, Néstor Espinoza, Andrés Jordán, Daniel Bayliss, Edward M. Bryant, Martin Schlecker, Melissa J. Hobson, Rafael Brahm, Remo Burn, Thomas Henning

Fluid Dynamics

An Artificial-Compressibility Physics-Informed Neural Network for the Unsteady Incompressible Navier–Stokes Equations

Aytekin Çibik

We study a physics-informed neural network (PINN) for the unsteady, two-dimensional incompressible Navier–Stokes equations in which the stiff divergence-free constraint is replaced by an artificial-compressibility (AC) relaxation governed by a single scalar parameter $\eps$. The relaxation reintroduces a pressure time derivative, converting a differential-algebraic constraint into an ordinary residual that a PINN can minimise directly. On the Taylor–Green vortex, which admits a closed-form unsteady solution, we quantify the effect of $\eps$: the residual divergence scales as $\eps\,|\partial_t p|$, so larger $\eps$ raises both the divergence and the velocity error, and both decrease monotonically and saturate as $\eps$ is reduced. On the $Re=100$ cylinder wake the plain forward AC-PINN collapses to the steady symmetric branch and does not reproduce von Kármán shedding; assimilating a few hundred sparse velocity sensors from a boundary-layer-resolved finite-element reference (whose Strouhal number, $0.176$, we bring close to the $0.164$–$0.172$ literature band by resolving the separating shear layer, though it remains just above it) recovers the unsteady vortex street to $7\%$ over the wake and its shedding frequency to within $3\%$ of that same reference — a bound set by the reference's own fidelity rather than an independent validation against the true flow.
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High Energy Physics (Phenomenology)

Pinpointing the Mechanism of Neutrinoless Weak Decays with Positrons

Julia Harz and George A. Parker

Neutrinoless double beta decay is the flagship laboratory probe of a Majorana contribution to the neutrino mass. However, besides the standard mass mechanism other higher- dimensional lepton number-violating interactions can enter, or even dominate, this process. The corresponding positron-emitting neutrinoless modes, such as electron capture or double-positron emission, have long been considered out of reach experimentally, due to their naturally smaller rates. Recently, innovative detector technologies as used in the proposed NuDoubt++ experiment are changing the game. In this work, we explore how a positron- and electron-mode detector can be complementary in the search for new physics. Assuming an observation of neutrinoless double beta decay, we predict the expected discovery half-life for the positron-modes. Using half-life ratios, especially between the double beta and electron capture modes, we demonstrate how underlying long-range interactions can be distinguished, in particular to identify a purely right-handed leptonic current.
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Astrophysics of Galaxies

Phosphorous in the moderately metal-poor bulge globular clusters NGC 6539 and NGC 6569

Morgan S. Camargo, Beatriz Barbuy, Heitor Ernandes et al. (+10 more)

The distinct stellar populations of the Galactic bulge can be disentangled through detailed analysis of their chemical abundances and kinematical properties. Recent studies have suggested that globular clusters located in the Galactic bulge with metallicities around $\rm [Fe/H] \approx -0.7$, may represent some of the oldest systems in the Milky Way, potentially tracing the early spheroidal bulge. The coincidence of a metallicity peak at $\rm [Fe/H] \approx -0.7$ in both field stars and globular clusters, together with the presence of phosphorus-rich (P-rich) stars, may provide important clues to the nature of the first generations of stars formed in the Galaxy. In this work, we investigate the odd-Z elements Na, Al and particularly P in the bulge globular clusters NGC~6539 ($\rm[Fe/H] \sim -0.75$) and NGC~6569 ($\rm [Fe/H] \sim -0.85$) using APOGEE spectra. We also examine the clusters Tonantzintla-1 and NGC~6316, which exhibit evidence of phosphorus enhancement. Our analysis confirms that NGC~6539 is a cluster of interest, with one clearly P-rich star, whereas NGC~6569 shows a lower level of P-enhancement. This again suggests that there might have been an early bulge building block with the metallicity of $\rm[Fe/H] \sim-0.75$, of which NGC~6539 would be part of. The observed abundance patterns indicate that the production of Na and Al is consistent with nucleosynthesis in massive stars. However, the origin of the phosphorus enrichment remains uncertain, suggesting that additional nucleosynthetic channels may be required to explain the observed abundances. These findings provide new constraints on the chemical evolution of the Galactic bulge and the nature of its earliest stellar populations.
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All authors Morgan S. Camargo, Beatriz Barbuy, Heitor Ernandes, Amâncio C. S. Friaça, Cristina Chiappini, Bernardo P. L. Ferreira, Stefano O. Souza, Sergio Ortolani, Domenico Nardiello, Eduardo Bica, José G. Fernández-Trincado, Nicolas Barrera, Doug Geisler

Materials Science

Pressure-Tunable Electronic and Magnonic Transport in Altermagnet La$_2$O$_3$Mn$_2$Se$_2$

Nafise Rezaei, Alireza Qaiumzadeh, Artem R. Oganov et al. (+1 more)

Hydrostatic pressure provides a symmetry-preserving route to engineer electronic and magnonic transport in the correlated insulating altermagnet La$_2$O$_3$Mn$_2$Se$_2$. Using first-principles calculations combined with spin-Hamiltonian modeling, we show that compression from 0 to 40 GPa markedly enhances the inequivalence between the competing second-neighbor exchange interactions, increasing $|J_{2a}-J_{2b}|$ from 1.97 to 9.38 meV while preserving the compensated antiferromagnetic ground state. The resulting exchange anisotropy amplifies the momentum-dependent splitting between the two chiral magnon branches, yielding a nearly fourfold enhancement of the longitudinal magnon-driven spin Seebeck response at 100 K, from $3.68\times10^{-1}$ to $1.36$ meV/K. In contrast, hydrostatic pressure preserves the magnetic-symmetry selection rules governing the anomalous Hall effect while redistributing the electronic Berry curvature, producing pronounced energy-dependent sign reversals in the anomalous Hall conductivity. These results identify exchange anisotropy as the microscopic mechanism underlying the pressure-enhanced magnon response and establish hydrostatic pressure as an effective means of simultaneously controlling electronic and magnonic transport in insulating altermagnets.
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All authors Nafise Rezaei, Alireza Qaiumzadeh, Artem R. Oganov, Mojtaba Alaei

High Energy Physics (Phenomenology)

Bare effective potential and Goldstone boson anti-resummation

Stephen P. Martin

I discuss the evaluation of the effective potential and related quantities starting from bare perturbation theory followed by $\overline{\rm{MS}}$ renormalization. The advantages of this method include a simple new way of avoiding infrared problems associated with Goldstone bosons, by treating their bare squared masses as two-point interaction vertices instead of incorporating them into the propagators. Thus, only positive integer powers of the Goldstone-boson squared masses appear at every stage of calculation, avoiding the imaginary parts and singularities encountered in intermediate steps of previous resummation methods for the minimization conditions. This Goldstone boson anti-resummation approach is implemented using simple rules provided through three-loop order in terms of the master vacuum integrals. Explicit results are given for the Standard Model at three-loop order. The method is shown to give effective potential minimization conditions that are consistent with previous resummation methods, but in a form more directly useful for related future multi-loop calculations of observables in the tadpole-free scheme.
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Solar and Stellar Astrophysics

A survey of ultra-compact high-state AM CVn binaries with ZTF and Gaia: New discoveries and observational constraints on Galactic space density

Ilkham Galiullin, Antonio C. Rodriguez, Kareem El-Badry et al. (+9 more)

Ultra-compact AM CVn binaries in the high-state of stable mass transfer ($\dot{M}\gtrsim10^{-9}M_\odot/\rm{yr}$) are expected to be among the loudest persistent sources for upcoming space-based GW observatories. These systems typically have orbital periods $P_{\rm{orb}}\lesssim30$ minutes. We present a systematic search for high-state AM CVn binaries in the Milky Way by targeting a region within the Gaia color-magnitude diagram, combined with ZTF time-domain photometry. We focus on variable targets within that sample with 5-30 minute periods. Our survey discovered three new high-state AM CVn binaries (ZTF J1840-1742, ZTF J2007-0527 and ZTF J2111+3158) with orbital periods of 16.86, 18.63, and 16.71 minutes, and recovered three known systems. We obtain high-speed photometry and phase-resolved spectroscopy to confirm their nature. Their spectra show helium emission lines with no detectable hydrogen. In two targets, the lines are double-peaked, and Doppler tomograms confirm an accretion disk. We estimate mass accretion rates of $\sim10^{-9}M_\odot/\rm{yr}$, and $3\sigma$ X-ray luminosity upper limits of $\sim10^{33}\rm{erg/s}$. Based on this sample, we infer a local space density of high-state AM CVn population in the Milky Way of $\sim(1.0-2.7)\times10^{-8}\rm{pc}^{-3}$ (for disk scale heights $h_z=300-200$ pc), representing 2-5% of the total Galactic AM CVn density. Their birth rate, $\sim(2.4-4.3)\times10^{-4}\rm{yr}^{-1}$ (for $h_z=300-200$ pc), is consistent with the total AM CVn birth rate, implying most systems entering the high-state phase survive and evolve to longer orbital periods. This local space density suggests LISA and TianQin will detect about 36% and 19% of the total Galactic population, respectively, during their nominal 4-yr missions ($S/N\ge5$). The Vera C. Rubin Observatory's LSST will detect about 34-44% of these systems over its 10-yr survey ($m_r\lesssim26.9$ mag).
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All authors Ilkham Galiullin, Antonio C. Rodriguez, Kareem El-Badry, Valery Suleimanov, Vladislav Dodon, Askar Sibgatullin, Warren R. Brown, Kevin Burdge, Jan van Roestel, Edo Berger, V. Ashley Villar, Ilaria Caiazzo

Plasma Physics

Computational Methods and GPU Acceleration in Plasma Physics: A Empirical Analysis of arXiv Publications and Research Trends

Jeremy J. Williams, Anders Brostrom and Stefano Markidis

Computational plasma physics increasingly relies on high-performance computing (HPC) methods, including particle-in-cell (PIC), gyrokinetic, and magnetohydrodynamic (MHD) simulations, yet field-wide evidence on how method choice, team size, and GPU adoption shape research outputs remains limited. We analyze 5,522 computational plasma physics papers published on arXiv between 2010 and 2025 using large-scale text mining, employing abstract length as a proxy for methodological and algorithmic complexity. Using ordinary least squares (OLS), tobit, and logistic regression models, we examine how abstract length and GPU mentions vary with computational method, number of authors, and publication year. Controlling for collaboration size and temporal trends, results show that MHD studies have longer abstracts than PIC and gyrokinetic papers, indicating more extensive methodological and physical exposition. Abstract length increases modestly with team size, while temporal effects suggest gradual changes in abstract conciseness over time. At the same time, PIC and gyrokinetic methods have grown substantially in relative prevalence over the past decade and are strongly linked to GPU adoption, reflecting their higher computational intensity and suitability for accelerator-based architectures. Together, these findings highlight a decoupling between methodological verbosity and method prevalence, offering a new bibliometric perspective on the evolution of HPC-driven plasma physics research.
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Soft Condensed Matter

Role of Particle Shape in Strain-Controlled Resuspension of Dense Suspensions

Mohammadreza Mahmoudian, Mahdi Vaezi and Parisa Mirbod

> Dense non-Brownian suspensions exhibit complex resuspension dynamics governed by hydrodynamic interactions, particle microstructure, and gravity. While viscous resuspension in spherical suspensions is known to be strain-controlled, its applicability to anisotropic particles remains unclear. Here, we investigate dense suspensions of spherical and rod-shaped particles under steady and oscillatory shear. The results reveal two strain-controlled transitions: particle detachment from the sediment bed and the transition to a fully suspended state. Both particle shapes exhibit the same critical strain for detachment, approximately 6, indicating that resuspension onset is largely independent of particle morphology. In contrast, complete resuspension requires a critical strain of approximately 120 for spheres and 180 for rods, demonstrating a strong effect of particle anisotropy. A fluid-strain scaling collapses the onset of resuspension across particle concentrations and shapes while highlighting the distinct influence of particle shape on complete suspension. These findings establish a unified strain-based framework for viscous resuspension and clarify the role of particle anisotropy in dense suspension dynamics.
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Astrophysics of Galaxies

Chemo-dynamical stratification of the Galactic disc using Gaia-ESO open clusters

Casmir O. Obasi, M. Gómez, J. G. Fernández-Trincado et al. (+5 more)

Understanding how the Milky Way disc assembled and evolved requires tracing the coupled evolution of stellar chemistry and orbital structure over time. Open clusters, as coeval stellar populations with well-constrained ages, distances, and chemical properties, provide powerful benchmarks for this purpose. We aim to characterise the age-dependent chemo-dynamical structure of the Galactic disc and to investigate how open clusters populate dynamical phase space as a function of age. We analysed a sample of Galactic open clusters using homogeneous chemical abundances from the Gaia-ESO Survey together with Gaia DR3 phase-space information. Combining cluster ages with orbital parameters and actions, we examined how clusters populate dynamical phase space over the last ~4 Gyr. We find that clusters with similar chemical properties occupy coherent regions of action space, while their orbital structure shows a clear dependence on age. Radial excursions and orbital eccentricities broaden systematically toward older ages, indicating increasingly diverse orbital configurations in the older cluster population. The dispersion in the [Fe/H]-Rg relation also increases with age, consistent with a combination of secular redistribution, survival bias, and dynamically distinct outer-disc populations. In addition, older clusters reach larger vertical amplitudes and vertical actions, revealing a coupled but anisotropic evolution between in-plane and vertical orbital structure. Open clusters provide precise, age-resolved tracers of the chemo-dynamical structure of the Galactic disc. Our results reveal systematic age-dependent variations in the orbital and chemical properties of the cluster population, consistent with the combined effects of secular evolution, orbital redistribution, and environmentally dependent cluster survival over the last few Gyr.
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All authors Casmir O. Obasi, M. Gómez, J. G. Fernández-Trincado, D. Minniti, B. Dias, B. Barbuy, M. V. Alonso, L. D. Baravalle

Fluid Dynamics

Floquet stability analysis of pulsatile particle-laden channel flow

Ananthapadmanabhan Ramesh, Benoit Pier and Parisa Mirbod

We investigate the linear stability of particle-laden pulsatile channel flow using Floquet analysis within a two-phase dusty-gas framework. Uniformly distributed spherical particles are coupled to an incompressible Newtonian fluid through Stokes drag, and the governing equations are linearized about a time-periodic base flow driven by a sinusoidally varying pressure gradient. The effects of Reynolds number, Womersley number, pulsation amplitude, particle relaxation time, and particle mass fraction on temporal instability are examined. In the steady limit, particles with very short relaxation times destabilize the flow, whereas finite relaxation times introduce interphase slip and drag-mediated damping that stabilize disturbances. Under pulsatile forcing, increasing pulsation amplitude destabilizes the flow at low Womersley numbers but stabilizes it at sufficiently high Womersley numbers. This transition is governed by the penetration depth of oscillatory motion and is systematically shifted by particle relaxation time and mass loading through interphase momentum exchange. A critical corresponding value remains small throughout, indicating strong particle-fluid coupling and ruling out resonance-like particle dynamics. These findings provide a unified physical framework for the stability of pulsatile particle-laden flows relevant to physiological and periodically forced multiphase systems.
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Mesoscale and Nanoscale Physics

Valley polarization of moiré interlayer exciton complexes driven by many-body interactions

Adrian O. Paulus, Mikołaj J. Metelski, Alain Dijkstra et al. (+4 more)

Localized interlayer excitons (IX) in moiré transition metal dichalcogenide heterostructures can both probe and participate in many-body states hosted by the moiré superlattice. When the IX density is small compared to the moiré lattice density, the formation of incompressible charge crystals at fractional electronic moiré fillings modifies exciton-charge scattering, leading to enhanced lifetimes in photoluminescence (PL) measurements. At high IX densities, the exciton dynamics are altered by the emergence of an excitonic Mott insulator and the formation of doubly-occupied sites (IXX). Here, we investigate the IX PL lifetime and valley polarization in an R-type $\mathrm{WSe_2}$/$\mathrm{WS_2}$ bilayer across a wide range of IX and charge densities. While previous studies reported a decrease of polarization in time-integrated measurements in charge-incompressible phases, our results show that this arises not from enhanced intervalley scattering, but from a dilution of the valley polarization by the dramatic enhancement of IX lifetimes. At high excitation densities, we probe the dynamics of the IXX and show that despite the nominal antiparallel valley configuration of the two constituent excitons, a strong, anomalous valley polarization develops as the IXX population decays. Our results shed light on the complex exciton and valley dynamics of IX and demonstrate that they are strongly modified by the rich many-body physics of moiré heterobilayers.
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All authors Adrian O. Paulus, Mikołaj J. Metelski, Alain Dijkstra, Kenji Watanabe, Takashi Taniguchi, Nathan P. Wilson, Jonathan J. Finley

Soft Condensed Matter

Fractional Viscoelasticity in Transient Unentangled Polymer Networks

Sachin Shanbhag and Ralm G. Ricarte

Stress relaxation in transient polymer networks often shows extended power-law behavior, $G(t) \sim t^{-\beta}$, where the exponent $\beta$ frequently departs from the value $1/2$ predicted by the sticky Rouse model and its variants. We introduce the fractional inhomogeneous Rouse model (FIRM), which uses a generalized Langevin equation driven by fractional Gaussian noise of exponent $\alpha$, while retaining heterogeneous bead friction to represent sticky cross-links. Thus, FIRM unifies subdiffusive sticker dynamics and chain heterogeneity within a single framework. We show that the relaxation modulus $G(t)$ can be represented as a linear combination of Mittag-Leffler functions. For homogeneous chains, it recovers two power-law regimes, $t^{-\alpha/2}$ and $t^{-2\alpha}$, on either side of the terminal relaxation time. Fitting FIRM to stress relaxation data for an imine-based polystyrene vitrimer shows that $\alpha < 1$ is required to capture the shape of the terminal relaxation. It also accommodates both Arrhenius and non-Arrhenius temperature dependence in the rheological activation energy. We derive expressions for dynamic properties such as mean-squared displacement and dielectric response and outline how generalized memory kernels extend the framework to real materials. Together, these results suggest novel ways in which data from rheology, dielectric spectroscopy, scattering, and other experimental methods may be incorporated into a chemistry-specific molecular model.
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High Energy Physics (Phenomenology)

Amnesia in the Axion Misalignment Landscape

Kierthika Chathirathas, Cem Eröncel, Mathieu Kaltschmidt et al. (+2 more)

Pre-inflationary axion cosmologies admit a broad range of initial velocities and angles that generate a landscape of misalignment histories, whose nonlinear fate and small-scale structure remain uncertain. We use lattice simulations to follow the QCD axion in the kinetic misalignment scenario through the QCD crossover into the non-relativistic regime, towards matter-radiation equality. In the meV mass range, this landscape contains a continuum of ”summit-landing" solutions sensitive to both the initial angle and velocity. Nonlinear fragmentation reduces the comoving axion number and modifies the relation between the misalignment history and present relic abundance. For sufficiently large axion masses, strong self-interactions drive the small-scale spectrum towards the attractor found for post-inflationary axions, so that distinct early histories can lead to similar late-time structures.
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All authors Kierthika Chathirathas, Cem Eröncel, Mathieu Kaltschmidt, Javier Redondo, Kenichi Saikawa

Fluid Dynamics

Impact of Wind Direction on Flow and Turbulent Statistics Over a Realistic Urban Area: A Large-Eddy Simulation Study

Josep M. Duró, Ernest Mestres, Ming Teng et al. (+2 more)

Effects of wind direction in realistic urban canopies remain difficult to characterize systematically because local flow patterns, building-height variability, and turbulent statistics within a realistic urban canopy may respond differently to changes in the approaching wind. To investigate these multi-scale directional impacts, we conducted high-resolution large-eddy simulations of the atmospheric boundary layer over the Zona Universitaria Pedralbes district in Barcelona. The computational meshes employ fourth-order spectral elements, yielding pedestrian-level resolutions below 1 m and resulting in approximately 5.0e8 degrees of freedom. Sixteen wind directions uniformly distributed over 360deg are simulated to capture the full directional response of the urban fabric.
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All authors Josep M. Duró, Ernest Mestres, Ming Teng, Oriol Lehmkuhl, Ivette Rodríguez

Quantum Physics

Photon localization: a comparative study

Laura M. Ferguson, Ricardo Rojas Castellano, Kayla Oltman et al. (+2 more)

We compare different measures for photon localization in terms of two-dimensional Gaussian wave packets of width Delta k. We find that all measures start to coalesce if the wave packet has evolved for times which are larger than a few (c Delta k)^{-1}. However, the Landau-Peierls wave function yields the largest initial offset <r>-ct > 0 while the Fourier transform of the helicity components of the k-space wave packet yields the smallest offset <r>-ct > 0 and converges towards <r>-ct = 0 fastest. We also discuss local detection of photons through a model detector consisting of ions in ion traps. The position-dependent detection probabilities are inferred from the scattering matrix. We find that the local detection probability for photons can be expressed in terms of three of the proposed localization measures, viz. the Landau-Peierls wave function, the energy wave function, and the Hawton density. Those three proposals also remain close throughout the time evolution of the single-photon wave packet. However, the energy wave function is locally related to electromagnetic fields and is therefore confirmed as the preferred tool for the description of local photon densities. The novelty of our observations concerns three items, viz. the possibility to express local photon absorption matrix elements through three of the proposed localization measures, the coalescence of all the proposed localization measures after sufficiently long evolution of a photon wave packet, and the striking differences of some of the proposed localization measures during early wave packet evolution.
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All authors Laura M. Ferguson, Ricardo Rojas Castellano, Kayla Oltman, Joshua G. Fenwick, Rainer Dick

Physics and Society

Efficient generation of networks with minimal average shortest-path distance

Meritxell Vila-Miñana and Filippo Radicchi

Designing networks that minimize distances and satisfy structural constraints is a fundamental task across transportation, communication, and biological systems. Here, we consider the problem of finding, for a given degree sequence, the network structure displaying the smallest possible average shortest-path length. While exact solutions are available in linear time for trees, such an optimization problem becomes computationally infeasible as soon as loops are allowed in the networks. We propose a fast algorithm to construct approximate solutions to such a degree-constrained distance-minimization problem. Accordingly, edges are first created between high-degree nodes; then, additional connections are placed following the rules of the standard configuration model. In spite of its simplicity, the algorithm displays outstanding performance as demonstrated in our systematic experiments on both synthetic and real degree sequences. Our method is particularly effective on synthetic degree sequences displaying medium levels of heterogeneity. When applied to degree sequences of real networks, the proposed algorithm is able to reduce the all-pair shortest path of real structures by 20%, on average. We perform a validation on small-sized networks, where we compare the shortest-path distance of the networks generated with our algorithm against those obtained via simulated annealing optimization. Although simulated annealing yields slightly better structures, our proposed algorithm provides nearly identical solutions at a substantially lower computational cost, making it a solid method in applications concerning large-scale systems.
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Statistical Mechanics

Gibbs variational principles and Boltzmann irreversible theorem

Mário J. de Oliveira and Silvio R. Salinas

We analyze the Gibbs variational principles associated with the probability distributions of (i) an isolated system and (ii) a system at constant temperature. We give an example of using the Gibbs inequality to obtain the free energy and analyze the phase diagram of an Ising model with competing interactions. We also review the Boltzmann irreversible theorem, and show how it is connected to the Gibbs variational principles. This connection is established by using the Kolmogorov equation for the evolution of the probability distribution, which predicts a monotonic increase of entropy for an isolated system, and a decrease of the free energy for a system in contact with a thermal reservoir.
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Quantum Physics

Quantum Contextuality and Entanglement-Free Grover Search in a Trapped-Ion Optical Qudit

Tarun Dutta, Jasper Phua Sing Cheng, Alex Jin et al. (+3 more)

Quantum computational advantage is generally attributed to coherent interference and other non-classical resources, yet their respective roles remain difficult to disentangle in experimental platforms where multipartite entanglement is inherently present. High-dimensional quantum systems provide an attractive route for investigating these resources while simultaneously reducing hardware overhead for quantum information processing. Here we realize a programmable four-dimensional optical qudit encoded in a single trapped $^{138}\mathrm{Ba}^{+}$ ion and demonstrate universal coherent control through phase-programmable optical rotations. Using this platform, we implement an entanglement-free realization of Grover's quantum search algorithm, achieving target-state identification probabilities of up to $94.5\pm2.0\%$. Within the same processor, we further demonstrate state-dependent quantum contextuality through a Clauser–Horne–Shimony–Holt (CHSH)-type noncontextuality inequality, obtaining a maximum violation of $S = 2.816 \pm 0.082$, in close agreement with the Tsirelson bound. By integrating programmable quantum computation and contextuality measurements within a single multilevel trapped-ion platform, our work establishes a versatile architecture for investigating the relationship between coherent interference and contextuality in quantum information processing and provides a scalable route toward high-dimensional quantum technologies.
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All authors Tarun Dutta, Jasper Phua Sing Cheng, Alex Jin, Sergi Ramos-Calderer, José Ignacio Latorre, Manas Mukherjee

Statistical Mechanics

Experimental Kuramoto Platform

Leandro Freitas, Victor H. S. Bittencourt, Débora D. Superbi et al. (+3 more)

Phase reduction provides a principled relationship between high-dimensional oscillator dynamics and low-dimensional phase models such as the Kuramoto model. However, connecting analytical results derived from the Kuramoto framework to experimental data remains an open challenge, as many physical platforms violate the weak-coupling assumptions underlying standard phase reduction. Here, we present an experimental platform based on electronic quadrature oscillators whose phase dynamics are, under certain assumptions, equivalent to the Kuramoto model. Crucially, this equivalence is achieved for both weak and strong coupling through a non-diffusive coupling circuit, and the design approach supports arbitrary (weighted and directed) network topologies while preserving scalability and oscillation regularity. Across different coupling schemes, we demonstrate that the platform reliably reproduces phase transitions predicted by the Kuramoto model for both global and cluster synchronization. This cost-effective platform enables systematic experimental validation of analytical and numerical results for synchronization in complex networks.
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All authors Leandro Freitas, Victor H. S. Bittencourt, Débora D. Superbi, Wanderley C. Silva Junior, Arthur N. Montanari, Luis A. Aguirre

Instrumentation and Detectors

High Temporal and Spatial Resolution X-Ray and Gamma-Ray Imaging using an Event-Mode Scintillator-Based Detector

Alexander Wolfertz, Ondrej Zapadlik, Alex Gustschin et al. (+2 more)

LumaCam detectors are a novel type of event-mode imaging detectors based on scintillator screens that have been developed recently for neutron imaging applications. They operate in an event-mode in which individual interactions of the incoming particles with the scintillator screen are reconstructed in both space and time, providing simultaneous high spatial and temporal resolution. In this work, we demonstrate the applicability of LumaCam detectors to X-ray and gamma-ray imaging. First tests with a 120 kV acceleration voltage X-ray source show a spatial detector resolution down to 50 um and the temporal resolution is estimated to be ~1 us. This combination makes LumaCam detectors especially suitable for imaging fast processes with high spatial resolution with limited cone beam magnification. The most significant adaption of the detector from the version for neutron detection is the scintillator screen. To further investigate the potential of LumaCam detectors for high-energy photon applications, additional measurements employing different scintillator screen materials have been carried out using gamma ray sources. The results show significant improvements in the temporal resolution with values as low as ~15 ns. In addition, some scintillators also show significant energy sensitivity in the photon multiplicity spectrum, highlighting the potential of LumaCam detectors for energy-selective X-ray and gamma-ray imaging.
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All authors Alexander Wolfertz, Ondrej Zapadlik, Alex Gustschin, Adrian Losko, Andrei Nomerotski

Astrophysics of Galaxies

Resolving dense photodissociation regions: the structure of photochemical fronts in three-dimensional gas distributions

Brandt A. L. Gaches, Thomas G. Bisbas, Lothar Brendel et al. (+1 more)

For decades, the Orion Bar has been the prototypical photodissociation region. Viewed nearly edge-on, it offers a unique window into the stratified chemical structure of the atomic-to-molecular transition of the interstellar medium. Understanding its photochemistry is essential to interpreting key observations originating from dense photo-dissociation regions. ALMA and JWST observations reveal that H2 photodissociation front overlaps with the C+ recombination front and exhibits a complex spatial morphology. Despite considerable theoretical effort, existing modeling approaches based on simplified geometrical assumptions have difficulties reproducing the spatial emission structure. Our aim is to investigate the response of photochemistry in realistic three-dimensional density distributions, using the Orion Bar as a representative application. We present the first fully three-dimensional high-resolution model of an Orion Bar analogue that resolves the relevant photochemical fronts using the upgraded steady-state 3D-PDR photo-dissociation region code, which allows for the treatment of plane-irradiatation and for the solution of the non-LTE H2 rovibrational levels. We find that the H2 dissociation front is characterized by a complex surface that overlaps with the C+ recombination front. Our 3D model can reproduce the complex morphology of H2 emission seen in observations, in particular the arc- and filament-like features, and provides a physical explanation of its chemistry. The overlapping H2 dissociation and C+ recombination fronts and the spatial emission morphology can be explained due to the three-dimensional gas distribution, resulting in shadowing and shielding by dense substructures. Our results mark a turning point for astrochemistry, where three-dimensional steady-state models can deliver fundamentally new insights into the chemistry of the interstellar medium. (Abridged)
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All authors Brandt A. L. Gaches, Thomas G. Bisbas, Lothar Brendel, Zhengping Zhu

Quantum Physics

Poled-fibre phase modulator for efficient high-dimensional quantum measurements

Nayda Guerrero, Nelson Villalba, Gustavo H. dos Santos et al. (+10 more)

Efficient detection of quantum states underpins advanced device-independent quantum-information protocols that provide the ultimate level of security for tasks including quantum random number generation and quantum key distribution (QKD). High-dimensional encoding is a natural route to boost the performance of such protocols, offering enhanced noise resilience and higher information capacity, yet their practical implementation remains challenging. A key experimental bottleneck in higher dimensions is the typical need of active modulators for basis selection, which incur substantial optical losses and polarization-sensitive operation. Poled optical fiber phase modulators (PFPMs) are a fiber-native electro-optic technology that naturally addresses these challenges, combining sub-dB insertion loss, intrinsic polarization independence, and direct compatibility with standard telecommunications fiber. Here we report the first use of a PFPM for active quantum-state measurements in a fully fiber-integrated platform. Basis selection in our receiver for four-dimensional qudits is achieved using a single PFPM, substantially simplifying the receiver architecture. As a benchmark, we perform a four-dimensional QKD session and obtain a finite secret-key rate per pulse that, to the best of our knowledge, surpasses all previously reported QKD demonstrations. Our results establish poled-fiber electro-optic modulation as a broadly applicable platform for high-efficiency detection in fiber-integrated quantum information processing.
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All authors Nayda Guerrero, Nelson Villalba, Gustavo H. dos Santos, Carlos J. Salazar, Cristobal Melo, Fernando Castillo, Jaime Cariñe, Guilherme B. Xavier, Esteban S. Gómez, Stephen P. Walborn, João Pereira, Gabriel Saavedra, Gustavo Lima

Earth and Planetary Astrophysics

A new window in time: a mid-infrared slit spectroscopy mode for precision time-series astronomy with JWST/MIRI

Achrene Dyrek, Taylor J. Bell, Pierre-Olivier Lagage et al. (+7 more)

The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) provides Low Resolution Spectroscopy (LRS) over 5-12 um at a resolving power of R ~ 100. To date, all MIRI LRS time-series observations (TSOs) have been carried out in slitless mode, since long-duration pointing stability within the narrow 4.7” x 0.51” slit could not previously be guaranteed, leading to the possibility of degraded TSOs due to jitter. Commissioning activities established the telescope jitter to be less than 1 milliarcsecond (mas), four times less than the initial requirement. It was, therefore, worth assessing the suitability of the MIRI LRS slit as a TSO mode for precision time-domain science; this is the aim of the Cycle 3 program (PID 6219, PI: A. Dyrek). We observed a transit of the exoplanet HAT-P-12b over ~10 hours and compared the results to archival slitless observations of the same target (PID 1281, PI: P.-O. Lagage). Two independent data reductions of the transit spectra of both slit and slitless configurations are consistent within 1 sigma, validating the feasibility of the new mode. A joint fit of the slit and slitless observations confirms the presence of a spectral feature near 7.5 um. Using measured JWST pointing variations, we estimated slit-loss variations to be smaller than 40 ppm at 10 um. The drawback of the slitless mode is a higher background. Compellingly, the slit background is ~ 38 times lower on average than in slitless mode, improving sensitivity for faint targets (Jmag ~ 13-15). We also identified time-correlated noise unique to the slit dataset at long wavelengths, which requires further investigation. This new capability of TSOs in slit mode, which will be supported in Cycle 7 (in 2028), opens a new avenue for precision time-series astronomy for faint targets with JWST/MIRI.
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All authors Achrene Dyrek, Taylor J. Bell, Pierre-Olivier Lagage, Sarah Kendrew, Gareb Fernandez-Rodriguez, Thomas Greene, Giuseppe Morello, Michiel Min, Mael Voyer, Hannu Parviainen

Instrumentation and Methods for Astrophysics

Breaking the brightness barrier: JWST/NIRCam DHS spectroscopy for high-precision time-series observations

Achrene Dyrek, John Stansberry, Louis E. Bergeron et al. (+12 more)

Many of the most scientifically compelling exoplanets orbit bright nearby stars that exceed the brightness limits of existing JWST spectroscopic observing modes. To address this limitation, a new NIRCam Short Wavelength Grism Time-Series mode has been developed by combining the Dispersed Hartmann Sensor (DHS) with a new on-board multistripe detector readout capability. The DHS disperses the incoming light through multiple pupil sub-apertures, reducing the incident flux and providing slitless spectroscopy between approximately 1.0 and 2.3 um. The multistripe readout mode further increases the accessible brightness range (K ~ 2.5 - 5.7 mag, depending on the spectral type of the object), with the previous limit being K ~ 5.7 mag at 1.5 um, by reading only the detector regions containing the DHS spectra, reducing the detector frame time with the standard RAPID readout mode from 10.74 s to 1.36 s over even less when using smaller substripe sizes. Together with the simultaneous long-wavelength grism observations, the new mode provides spectroscopic continuous coverage from approximately 1.0 to 5.0 um for targets as bright as K ~ 2.5 mag. We present the first results of on-orbit commissioning of this new observing mode with the final stage consisting of observations of a full transit of the exoplanet WASP-18b, which allowed us to demonstrate the feasibility of using NIRCam DHS for high-precision time-series observations. The commissioning presented in this paper marks the first deployment of the multistripe detector readout on JWST. Beyond NIRCam DHS, this new capability will be extended to other spectroscopic modes, including NIRISS SOSS and NIRSpec PRISM. Bright nearby stars host many of the highest-priority targets for exoplanet atmospheric characterization, making multistripe an important new capability for maximizing the scientific return of JWST.
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All authors Achrene Dyrek, John Stansberry, Louis E. Bergeron, Everett Schlawin, Nestor Espinoza, Brian Brooks, Mario Gennaro, Martha L. Boyer, Russell Ryan, Bryan Hilbert, Munazza K. Alam, Aarynn L. Carter, Norbert Pirzkal, Julien H. Girard, Anton M. Koekemoer

High Energy Astrophysical Phenomena

Profile Reconstruction from Temporally Stable Emission Components for Timing PSR J1713+0747

Shaswata Chowdhury, M. A. Krishnakumar, Sharika Dhakappa et al. (+26 more)

The assumption of long-term pulse-profile stability underpins high-precision pulsar timing and forms the basis of pulsar timing array experiments. However, several millisecond pulsars exhibit temporal profile variability that can introduce systematic biases in pulse time of arrival measurements and compromise timing precision. We present a profile-domain analysis of PSR J1713+0747 at low radio frequencies, in the 300-500 MHz band, using upgraded GMRT observations for the Indian Pulsar Timing Array experiment. We model frequency-resolved pulse profiles using a Bayesian Gaussian decomposition framework in which individual Gaussian components are associated with persistent emission regions through informative phase priors that permit modest temporal variations. By tracking the evolution of the decomposed components across observing epochs and frequency sub-bands, we identify central Gaussian components that remain precisely localized despite changes in the integrated pulse morphology. We then reconstruct pulse profiles with realistic noise using these central components and perform timing analysis. Our approach provides a physically motivated framework for mitigating pulse-profile variability and offers a generic methodology for recovering robust timing information from pulsars exhibiting profile evolution.
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All authors Shaswata Chowdhury, M. A. Krishnakumar, Sharika Dhakappa, Vidit Singh, Debabrata Deb, Jyotijwal Debnath, Kaustubh Rai, Pratik Tarafdar, Abhimanyu Susobhanan, Churchil Dwivedi, Bhal Chandra Joshi, Shantanu Desai, Neelam Dhanda Batra, Jaikhomba Singha, Himanshu Grover, Manjari Bagchi, Mayuresh Surnis, Avinash Kumar Paladi, Aman Srivastava, Arul Pandian B., Suruj Jyoti Das, Jibin Jose, Kuldeep Meena, Sushovan Mondal, K Nobleson, Keitaro Takahashi, Hemanga Tahbildar, Kunjal Vara, Zenia Zuraiq

High Energy Physics (Theory)

Exact Modular Completion of the ABJM Effective Twisted Superpotential

Seyed Morteza Hosseini

The effective twisted superpotential governs the supersymmetric partition functions of three-dimensional $\mathcal{N}=2$ theories in the Cardy limit and, at large $N$, the gravitational blocks that are glued into the entropy function of supersymmetric $\mathrm{AdS}_4$ black holes. We determine its on-shell structure for $\mathrm{U}(N)_k\times\mathrm{U}(N)_{-k}$ ABJM theory at the universal twist, using a machine-learning discovery pipeline—physics-informed symbolic regression with integer-relation detection—applied to Bethe-vacuum data of up to $800$ digits. Its perturbative part terminates after two terms, a shifted-rank $3/2$-power and an $N$-independent constant map, which we obtain in closed form for every integer level. Its type-IIA genus expansion admits a closed coefficient formula at arbitrary genus, involving binomial and Bernoulli-number terms, and is asymptotic. For $k=1,2,4$ the entire finite-$N$ remainder is a single absolutely convergent divisor-sum $q$-series, obtained by applying a first-order differential operator to the Eichler integral of a weight-four Eisenstein series on $\Gamma_0(2)$ or $\Gamma_0(4)$. This closed form reproduces the data to $\sim\!10^{-797}$.
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High Energy Physics (Phenomenology)

Quarkoniumlike states above open-flavor thresholds in Born-Oppenheimer EFT

Nora Brambilla, Roberto Bruschini, Abhishek Mohapatra et al. (+2 more)

Many quarkoniumlike states have been observed above open-flavor thresholds, but their organization and internal structure remain unsettled. We study the isoscalar hidden-charm and hidden-bottom sectors in Born–Oppenheimer effective field theory (BOEFT), between the spin–isospin averaged $S+S$ and $S+P$ thresholds. At leading order, heavy-quark spin decouples, and the quarkonium static potential mixes through string breaking with the lowest tetraquark/open-flavor BO potentials of the same quantum numbers. These potentials are constrained by QCD symmetries, their short- and long-distance behavior, and lattice-QCD data. The only calibrated parameter is the lowest $1^{--}$ adjoint meson mass, fixed from the shallow multiplet associated with the $\chi_{c1}(3872)$. Using $T$-matrix, $K$-matrix, and complex-scaling methods, we determine bound states and resonance poles, their masses, pole widths from the included nonstrange $S+S$ channels, normalized pole couplings, and prescription-dependent quarkonium–open-flavor composition measures. The spectrum exhibits a common heavy-quark-spin-symmetry multiplet organization. Most poles are short-distance, predominantly quarkonium resonances. The same equations generate shallow, spatially extended, open-flavor-dominated states with molecular long-distance characteristics. Their binding energies, radii, and small quarkonium components are highly sensitive to the adjoint meson mass, whereas the higher spectrum is more stable. The equations also predict a more compact open-flavor-dominated resonance in the $l = 0$ bottomoniumlike sector, with a dominant $P$-wave open-flavor component. Together with the hybrid levels, the spectrum provides multiplet assignments for most candidates. States not naturally accommodated point to the need for hidden-strange and $S+P$ tetraquark/open-flavor BO sectors and for hybrid–tetraquark and hybrid–quarkonium mixings.
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All authors Nora Brambilla, Roberto Bruschini, Abhishek Mohapatra, Fang-Zheng Peng, Tommaso Scirpa