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Physics

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Thursday 9 July

Physics Education

Teacher Leader Identity Development in a Physics Teaching Community of Practice: A Narrative Case Study

Hamideh Talafian, Maggie Mahmood, Eric Kuo et al. (+2 more)

This longitudinal narrative case study examines the leadership identity development of Kayla, a female high school physics teacher, across five years of participation in a community of practice (CoP). Drawing on multiple data sources, we trace how her participation evolved from classroom-level practice to broader institutional influence. Four interconnected dimensions of leadership identity development were identified: personal, social, practice, and institutional culture change. Findings show how CoP membership provided collective legitimacy and relational support that enabled Kayla to move beyond identity negotiation toward transformation , successfully advocating for an AP Physics course and increasing female student participation. This study contributes to teacher professional learning literature by demonstrating the value of an identity lens for understanding teacher leadership as a gradual, socially enabled process. The longitudinal design reveals transformative conditions that cross-sectional studies often obscure, highlighting narrative case study as a productive methodology for capturing teacher leadership identity development over time.
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All authors Hamideh Talafian, Maggie Mahmood, Eric Kuo, Morten Lundsgaard, Tim Stelzer

Optics

Seeing inside a Plasmonic Nanogap: Few-molecule Orientation and Preferential Adsorption

Francesco Ciccarello, Nobuaki Oyamada, Thwahira Shirin Alampara et al. (+2 more)

Molecule-surface interactions are central to many research and technological areas, spanning from heterogeneous catalysis and polymer science to electrochemistry. Of particular relevance are metallic nanogaps used in molecular electronics and near-field spectroscopy. Due to the buried nature of these double interfaces, few methods exist to monitor side-specific interactions and relative molecular orientation inside the gap. In this work, we introduce plasmon-enhanced nonlinear vibrational spectroscopy as an efficient tool to investigate surface molecular adsorption within metallic nanojunctions. By exploiting simultaneous vibrational sum- and difference-frequency generation in dual-resonant nanocavities, we resolve molecular orientation and preferential binding to one of the two gold surfaces, with few-molecule sensitivity. We also discover that the non-resonant (electronic) second-order nonlinear response is not an intrinsic property of the metal surface, but is instead governed by the molecule-surface interaction. Our findings provide a powerful analytical tool, easily implementable as an add-on to Raman spectroscopy, thanks to commercially available mid-infrared quantum cascade lasers.
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All authors Francesco Ciccarello, Nobuaki Oyamada, Thwahira Shirin Alampara, Konstantin Malchow, Christophe Galland

Astrophysics of Galaxies

Star Clusters in the Ultraviolet

Annapurni Subramaniam, Samyaday Choudhury, Richard de Grijs et al. (+5 more)

Ultraviolet (UV) observations provide a powerful window into the hot and evolved stellar populations that shape the structure, evolution and integrated light of star clusters. Because UV wavelengths are highly sensitive to massive main-sequence stars, blue straggler stars (BSS), extreme-horizontal branch (HB) stars, post-HB stars, interacting binaries and compact remnants, they probe key evolutionary processes that are inaccessible at optical and infrared wavelengths. This review synthesises five decades of UV studies of star clusters across the Milky Way, the Magellanic Clouds (MCs) and nearby galaxies, drawing on results from early space missions, wide-field surveys, and high-resolution imaging. In Galactic open clusters, UV studies have revealed compact companions$-$including white dwarfs, hot subdwarfs and stripped stars$-$and have established the mass-transfer origins of BSS, Blue Lurkers and yellow stragglers. In globular clusters, UV imaging has identified multiple stellar populations through UV-sensitive molecular bands, probed helium enrichment and mapped HB morphologies. Wide-field UVIT surveys have extended HST studies with homogeneous catalogues of HB and post-HB stars across entire clusters. In the MCs, UV observations have transformed our understanding of multiple populations, rotation-driven extended main-sequence turn-offs and the UV-dim phenomenon, while spectroscopic surveys have constrained massive-star evolution, stellar winds and binarity at low metallicity. UV mapping of the Magellanic Bridge has revealed ongoing massive-star formation in low-density tidal environments. Beyond the Local Group, UV studies of extragalactic clusters constrain star-formation histories, stellar feedback and population synthesis across galactic environments. Collectively, UV observations now form a cornerstone of star cluster astrophysics and will continue to do so with upcoming missions.
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All authors Annapurni Subramaniam, Samyaday Choudhury, Richard de Grijs, Vikrant V. Jadhav, Chengyuan Li, Snehalata Sahu, Kaushar Vaidya, Li Wang

Quantum Physics

A diagrammatic field theory of quantum error correction

Steven Rayan

We develop a field-theoretic framework for quantum error correction centred on fusion-space codes in unitary fusion categories. Admissible clusters determine total-charge sectors and orthogonal footprint projectors recording locally visible data left by error histories. The central distinction is between diagnostic footprint algebras and syndrome-admissible commuting algebras: the latter can be measured without revealing logical information and resolve chosen error representatives into measured sectors. For such algebras, exact correctability is equivalent to fibrewise Knill–Laflamme conditions, yielding a measure-then-recover factorization. Under a contractible-vacuum locality hypothesis, closed neutral composites give a categorical sufficient criterion for scalar action on the code. In the Ising theory, four $\sigma$ punctures show that pair-charge footprints can be complementary logical diagnostics and realize an exact one-qubit Clifford shadow. A proper six-$\sigma$ code instead admits a syndrome-admissible pair-charge measurement and exact recovery from an explicit Majorana bilinear error. A second bilinear has the same measured footprint but differs by a logical bit flip, producing a concrete nontrivial footprint fibre and genuine decoding ambiguity. We also formulate conformal-block likelihood data and compute geometry-dependent Ising four-point weights. For growing code families, we prove a conditional Peierls-type threshold theorem: bounded connected-region growth, local stochastic noise, local neutralizability of small residual components, and componentwise decoder balance imply $\Pr_L(\mathrm{fail})\le C|\Omega_L|e^{-cL}$ below a nonzero constant error rate. We conclude with representation-theoretic and algebro-geometric directions involving tube and Hopf algebras, Yangian-type structures, Higgs bundles, spectral curves, Jacobians, and abelian varieties.
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Earth and Planetary Astrophysics

Tentative detection of circularly polarized bursty radio emissions from the HD 189733 exoplanetary system using NenuFAR beamformed observations

Jake D. Turner, Philippe Zarka, Jean-Mathias Grießmeier et al. (+4 more)

Observing auroral radio emission is one of the most promising methods for detecting exoplanetary magnetic fields, which provide valuable insights into planetary interiors, atmospheric properties, and potential habitability. The first hints of exoplanet auroral emission are starting to emerge. Recently, Zhang et al. (2025) reported a detection at 50 MHz of a circularly polarized bursty emission from the HD 189733 exoplanetary system using NenuFAR low-frequency imaging observations. The source of the emission is still unknown and may be caused by planetary auroral emissions, star-planet interactions, stellar activity, or the M-dwarf stellar companion. In this study, we analyze beamformed observations from NenuFAR of HD 189733 taken simultaneously during the previously detected burst. This dataset allows for an independent verification of the detected burst with a different backend and processing steps. Using the BOREALIS data reduction pipeline, we tentatively detect circularly polarized bursty emission ($\sim$10$\sigma$) from HD 189733 $\sim$1 hour before the burst found from the imaging observations. However, some uncertainty remains on whether our detected signal is astrophysical in nature due to excess correlated noise. Assuming an astrophysical origin, our observed characteristics are most consistent with a planetary origin, but stellar emission cannot be completely ruled. Therefore, more low-frequency radio observations are needed to confirm the astrophysical nature of our signal and to search for periodicity in the radio signal from HD 189733 to determine the true cause of the emission. These observations are ongoing. Our study highlights the power of simultaneous beamformed and imaging observations in the search for radio emission from exoplanets.
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All authors Jake D. Turner, Philippe Zarka, Jean-Mathias Grießmeier, Corentin K. Louis, Xiang Zhang, Emilie Mauduit, Tomoki Kimura

High Energy Physics (Phenomenology)

Revisiting bounds on neutrino dark matter interaction at spikes

Yasaman Farzan

Interactions between high energy neutrinos produced in active galactic nuclei (AGNs) and the dark matter (DM) particles in the dense spike around the supermassive black holes may lead to attenuation of the flux. This consideration along with the observation of a sizeable flux from at least four AGNs have been used to derive bounds on the neutrino dark matter scattering cross section \cite{Cline:2022qld}. We show that the attenuation strongly depends on the details of the microphysics parameters. In particular if the mediator is a vector boson with a mass much smaller than the center of mass energy of the neutrino and dark matter, the energy loss of the neutrino and therefore the flux attenuation will be negligible so the upper bound on the cross section in this limit can be considerably relaxed.
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High Energy Physics (Theory)

Anomaly mediation in Seiberg-Witten theories

Cyrus Tearlach Robertson Orkish and Daniel Stolarski

We study the coupling of anomaly mediated supersymmetry breaking (AMSB) to $\mathcal{N}=2$ supersymmetric theories with $SU(2)$ gauge group. Perturbatively, $\mathcal{N}=1$ supersymmetry (SUSY) is preserved in the UV description with the AMSB terms being equivalent to a supersymmetric mass term for the adjoint chiral multiplet, as considered in the original Seiberg-Witten papers. We show, however, that nonperturbative instanton contributions break supersymmetry completely. In the IR description, the theory with AMSB is qualitatively similar to its $\mathcal{N}=1$ analog, exhibiting monopole condensation and confinement. However, the effective Lagrangian breaks supersymmetry completely, and the values of the condensates are different from their $\mathcal{N}=1$ analogs. Under physically reasonable assumptions, it can be shown that the vacua must change to those of the perturbatively identical $\mathcal{N}=1$-preserving deformation as the SUSY-breaking scale crosses the strong coupling scale. This change must be caused by effects that cannot in principle be described within the effective weakly coupled IR theory. It is not a phase transition, and the vacua appear to lie in the same universality class at any finite SUSY-breaking scale. Nonetheless, this work highlights the subtle manner in which AMSB coupling to nonperturbative effects can change the vacuum field configuration and the global symmetries of a theory.
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Exactly Solvable and Integrable Systems · Cross-listed from math.DS

Integrability of Cauchy problems for discrete conformal maps and circle patterns

Maxim Arnold and Anton Izosimov

A map from a square lattice to the Riemann sphere is called discrete conformal if the image of every elementary square is a harmonic quadrilateral. We prove that the initial value problem for discrete conformal maps with quasi-periodic boundary conditions is Liouville integrable. We also show that the image of the embedding of Schramm's orthogonal square grid circle patterns into the space of discrete conformal maps is the real part of a symplectic leaf. As a consequence, we obtain the integrability of the corresponding Cauchy problem for circle patterns.
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Quantum Physics · Cross-listed from cs.IT

Keyless Covert Communication Over Quantum MACs with General Message Sets

Hassan ZivariFard and Xiaodong Wang

We study covert classical communication over quantum multiple-access channels (MACs) with general message sets. Specifically, we consider a fully quantum MAC with arbitrary message sets and an arbitrary number of transmitters. We demonstrate the feasibility of achieving a positive covert rate over this channel and establish general one-shot and asymptotic achievable rate regions. For classical-quantum MACs with general message sets, we establish the covert capacity, when the transmitters are restricted to deterministic encoding. Our result recovers, as a special case, known results for classical communication over classical MACs with general message sets, covert communication of a classical message over a classical channel with two transmitters, and classical communication over quantum MACs. We provide three examples of MACs to which our results can be applied, either directly or indirectly, to achieve positive covert rates. Specifically, we first study covert communication over a finite-dimensional MAC with a helper. We then analyze a classical Gaussian MAC with a helper and derive its covert capacity. Finally, we extend the analysis to a single-mode bosonic MAC with a helper and show that positive covert rates can also be achieved in this setting. To the best of our knowledge, this is the first work to achieve positive-rate covert communication over both classical and quantum MACs.
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Materials Science

Hybrid DiffractGPT-Rietveld Refinement Framework for Automated X-ray Diffraction Analysis

Charles Rhys Campbell, Justin Ely, Jaehyung Lee et al. (+2 more)

X-ray diffraction (XRD) is fundamental to structural materials characterization, yet transforming a raw powder pattern into a refined crystal structure still demands considerable domain expertise. We present AGAPI-XRD, a hybrid framework integrating DiffractGPT generative structure prediction, database pattern matching against JARVIS-DFT and COD, and automated Rietveld refinement and ALIGNN-FF relaxation through a unified API at https://atomgpt.org/xrd. First, we used the AGAPI-XRD pipeline to evaluate the crystal structure of a variety of minerals in the RRUFF database that were experimentally characterized using powder x-ray diffraction. Next, we benchmarked the lattice parameter prediction fidelity of the AGAPI-XRD pipeline using a subset of the Alexandria PBE-hull dataset and the subset of RRUFF minerals that have known lattice parameters. AGAPI-XRD returns valid lattice parameters for 79.7% of the RRUFF benchmark minerals and for 94.8–98.1% of the Alexandria subset, while identifying a candidate structure for 93.8% of RRUFF minerals. For this benchmark, pattern matching delivers the highest accuracy for known phases, while DiffractGPT extends structure generation to complex materials absent from existing databases. Together, AGAPI-XRD advances accessible, end-to-end automated crystal structure determination from powder XRD data.
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All authors Charles Rhys Campbell, Justin Ely, Jaehyung Lee, Frank M. Abel, Kamal Choudhary

Soft Condensed Matter

Generic behavior of ultrastability and anisotropic molecular packing in co-deposited organic semiconductor glass mixtures

Shinian Cheng, Yejung Lee, Junguang Yu et al. (+2 more)

Vapor-deposited glass mixtures of organic semiconductors commonly serve as active layers in organic electronic devices, whose lifetime and performance are strongly influenced by the stability and structure of these mixed glasses. Here, we study the stability and anisotropic molecular packing of six co-deposited organic semiconductor glass mixtures with 50:50 weight ratio, by differential scanning calorimetry and spectroscopic ellipsometry. We find that all six binary systems exhibit high kinetic stability and significantly reduced enthalpy relative to the corresponding liquid-cooled glassy mixtures (ultrastable behavior), even for systems where the glass transition temperatures of the components differ by more than 90 K. Furthermore, we demonstrate that the birefringence of a co-deposited glass mixture, a measure of its anisotropic packing, can be predicted from the birefringence of glasses of the two pure components. These results for stability and structure are expected to be applicable to other co-deposited organic semiconductor glass mixtures, so long as the two components mix well in the glass and individually can form ultrastable glasses. Therefore, our findings are significant for designing novel electronic devices with enhanced device lifetime and increased operational efficiency.
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All authors Shinian Cheng, Yejung Lee, Junguang Yu, Lian Yu, Mark D. Ediger

Cosmology and Nongalactic Astrophysics

Chromatic Effects Across the Roman Focal Plane: Implications for Supernova Photometry and Measurements of Cosmological Parameters

Rujuta Purohit, Dillon Brout, Daniel Scolnic et al. (+14 more)

Calibration uncertainties are the leading systematics in cosmological analyses using Type Ia supernovae (SNe Ia). For the Nancy Grace Roman Space Telescope (Roman), we quantify the impact of chromatic effects on SNe Ia photometry and derived cosmological parameters, using simulated light curves from the High-Latitude Time Domain Survey. We investigate two sources of wavelength-dependent bias: focal plane array (FPA)-dependent wavelength shifts arising from spatial variations across Roman's 18 detectors, and coherent wavelength shifts corresponding to the measured $0.06\%$ uncertainty in absolute filter wavelength calibration. Using simulated SNe Ia light curves, we find that the FPA-dependent shifts – which range from +6 to -80 $\rm \AA$ introduce a redshift-dependent distance modulus bias that, if left uncorrected, propagates to $\Delta w_0 \sim -0.06$ and $\Delta w_a = -0.236$, which are larger than the forecast statistical uncertainties of $\sigma_{\rm stat, w_0} = 0.025$ and $\sigma_{\rm stat, w_a} = 0.114$, rendering the survey systematics-limited. We probe the impact of chromatic effects by employing detector-specific filter curves that recover unbiased cosmological constraints; to remain below the statistical noise floor, FPA wavelength shifts must be characterized to within 20%. In contrast, a coherent 0.06% offset in filter wavelength calibration – ranging from -3 to -11 $\rm \AA$ – produces negligible redshift-dependent bias, with a minimal spread in $w_a$ ($\Delta w_a = -0.0004, \sigma_{w_{a,\rm sys}} = 0.114)$, demonstrating that the achieved pre-launch calibration precision is sufficient for this systematic to remain subdominant. Our results establish that chromatic effects are a required component of SN Ia cosmology with Roman.
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All authors Rujuta Purohit, Dillon Brout, Daniel Scolnic, Richard Kessler, Jillian Paulin, Stefano Casertano, Nora F. Sherman, Rebekah Hounsell, Eric R. Switzer, Benjamin M. Rose, Masao Sako, Lauren Aldoroty, Kene Anumba, Maria Acevedo, David Rubin, Russell E. Ryan Jr., The Roman Supernova Cosmology Project Infrastructure Team

General Relativity and Quantum Cosmology

Probing Rotating Einstein-Power-Yang-Mills Black Holes through Shadows and Quasinormal Modes: Prospects for Event Horizon Telescope Constraints

I. Ezzaki, A. El Boukili, H. Lekbich et al. (+1 more)

Within Einstein power-Yang-Mills gravity (EPYM), we build a rotating black hole via the Newman-Janis procedure applied to the spherically symmetric static seed, obtaining an EPYM-inspired Kerr-like metric controlled by the spin \(a\), the magnetic Yang-Mills charge \(Q\), and the power parameter \(q\). We analyse the horizon structure and the photon region, and we compute the shadow as it appears to a remote observer for different values of these parameters. Using the published Event Horizon Telescope measurements of M87\(^*\) and Sgr A\(^*\), we constrain the Yang-Mills charge and the power parameter from the angular size and the Schwarzschild deviation \(\delta\) of the observed images. At the Maxwell point \(q = 1\) the spin marginalized likelihood of M87\(^*\) bounds the charge to \(Q \lesssim 0.29\,M\) at \(1\sigma\), while the fixed-spin band intersection at \(a = 0.7\,M\) gives the weaker \(Q \lesssim 0.52\,M\) from the M87\(^*\) angular size alone. The bound weakens as \(q \to 3/2\), where the shadow diameter becomes nearly insensitive to the charge. The shadow radius also fixes the limiting absorption cross section at high frequencies and hence the energy emission rate, which is suppressed by the charge and enhanced by the power parameter. We then compute the quasinormal modes of a massless scalar on the rotating background from the leading-order Wentzel-Kramers-Brillouin (WKB) conditions on the Teukolsky type radial potential, finding that the oscillation frequency rises and the damping rate falls as the charge or spin increases. The power parameter leaves an imprint on the shadow size and its charge sensitivity and in the quasinormal spectrum the shift is in principle present but lies below the resolution of current detectors.
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All authors I. Ezzaki, A. El Boukili, H. Lekbich, A. Benami

Quantum Physics

Two-photon blockade without cascade channel in strong light-matter coupling

Hang-Hang Han and Zu-Jian Ying

We report a distinct two-photon blockade (termed as weak TPB) discovered in the strong-coupling regime of a parity-broken generalized quantum Rabi model, in addition to the other two-photon blockade (termed as strong TPB) in the ultrastrong coupling (USC) regime. In contrast to the strong TPB conventionally with opened cascade decay channel, the weak TPB phase emerges unconventionally with closed cascade decay channel. The closure of cascade channel originally allowed to open by parity breaking is unexpected and its opening in the strong-TPB regime is actually delayed. We extract a cubic law for the cascade transition rate that accounts for the suppression of cascade channel and the delayed opening in the two TPB regimes. Furthermore, we find that the population on the cascade state, which is crucial in the strong TPB, contrarily plays a minor role in the weak TPB. Instead, it is the upper state above the cascade that is relevant for the weak TPB. We demonstrate that the interplay of weak anharmonicity and resonant driving is the primary mechanism responsible for the upper-state population and the formation of weak TPB. Our analyses not only provide deeper insights into the nature of different TPBs, but also imply mechanism and manipulation diversities for the multi-photon blockade, which may open more avenues for developing quantum technologies on the manipulation level of individual quanta.
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Materials Science

High density two-component glasses of organic semiconductors prepared by physical vapor deposition

Yejung Lee, Shinian Cheng and M. D. Ediger

Physical Vapor Deposition (PVD) is widely utilized for the production of organic semiconductor devices due to its ability to form thin layers with exceptional properties. Although the layers in the device usually consist of two or more components, there is limited understanding about the fundamental characteristics of such multi-component vapor-deposited glasses. Here, spectroscopic ellipsometry was employed to characterize the densities, thermal stabilities and optical properties of co-vapor deposited NPD and TPD glasses across the entire range of composition. We find that co-deposited NPD and TPD form high density glasses with enhanced thermal stability. The dependences of density and stability upon substrate temperature are correlated, and the birefringence of the co-deposited glasses is determined by the reduced substrate temperature of mixtures. Additionally, we observe that the transformation of a highly stable and dense two component glass into its supercooled liquid initiates from the free surface and propagates into the bulk at constant velocity, like single component PVD glasses. All these features are consistent with the surface equilibration mechanism.
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General Relativity and Quantum Cosmology

Generalized Fisher-Janis-Newman-Winicour (FJNW) and Yilmaz-Rosen solutions in the higher-dimensional scalar-tensor theory with nonminimal coupling

K.K. Ernazarov

This paper investigates higher-dimensional scalar-tensor theories of gravity with nonminimal coupling, focusing on the reconstruction of exact spherically symmetric solutions. We systematically apply the formalism developed in previous works, which demonstrates that any static spherically symmetric metric can be represented as an exact solution of a scalar-tensor theory with specific coupling functions $f(\phi)$ and potential $U(\phi)$. Our analysis centers on two important classes of solutions in arbitrary spacetime dimensions: the Fisher-Janis-Newman-Winicour (FJNW) metric and its limiting case, the generalized Yilmaz-Rosen metric. We derive the key relations for the coupling function $f(\phi)$ and the scalar field potential $U(\phi)$ for both solution families using the master equation formalism in the Jordan frame. For the FJNW metric, we find that in the special case $s = 2$, $D = 6$, the coupling function $f(\phi)$ is positive in the domain $u^3 > M$, corresponding to gravitational attraction and a canonical scalar field with vanishing potential $U(\phi) = 0$. In contrast, for the generalized Yilmaz-Rosen metric in arbitrary dimensions $D > 4$, the reconstructed coupling function is always negative, $f(\phi) < 0$, indicating a phantom scalar field with negative kinetic energy and repulsive gravity.
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Fluid Dynamics

Wall-bounded turbulence needs not be long

Carlos Martinez Lopez and Javier Jimenez

Experiments on the regeneration of long streaks in flows in which they had originally been damped show that their initial growth is due to the interaction of the mean shear with long cross-flow velocities (rollers) that remain even when the streaks are damped. More surprisingly, turbulence also persists in simulations in which only the long rollers are damped while long streaks remain, and these flows are also able to recover when the damping is removed. Finally, simulations are presented in which both streaks and rollers longer than $\lambda_x^+ \approx 600$ are damped. They survive and regenerate, and an interpretation in terms of their energy balance is provided. In contraposition to the classical minimal channels, which include infinitely long structures, these new flows do not contain features longer than the damping wavelength, and support a model in which wall turbulence only depends on processes for which the geometric aspect ratio is of order unity.
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High Energy Astrophysical Phenomena

Studying the Variable Continuum and Emission Line Spectrum of 4U 1700-377 using NuSTAR's Stray Light

Colin J Bourque, McKinley C Brumback, Brian W Grefenstette et al. (+4 more)

The high-mass X-ray binary 4U 1700-377 shows strong variation in brightness on timescales of hundreds of seconds due to accretion from a highly clumped stellar wind from the companion. Using two focused observations and five stray light observations from NuSTAR, we are able to expand the baseline of observations of the source and track spectral parameters throughout the source's variability. The focused NuSTAR observations confidently detect excess emission lines at energies above Fe K$\alpha$, but are unable to universally constrain the nature of these lines independently of model choice. Strong Fe K$\alpha$ fluorescence is ubiquitous in the stray light data, but these observations lack sufficient signal-to-noise to further measure additional emission lines. We discuss the statistics of a claimed cyclotron resonant scattering feature as seen in the stray light spectra, but find no conclusive evidence for its existence. Finally, we investigate two instances of sustained low-flux states of up to 60 ks. When this occurs, luminosity can fall by almost an order of magnitude and the high-energy continuum softens significantly without corresponding to increased absorption. We discuss the manner in which the changing shape of the continuum during these intervals may show accretion during an extended rarefied interval of stellar wind, or a possible change of the dominant accretion regime.
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All authors Colin J Bourque, McKinley C Brumback, Brian W Grefenstette, Douglas J K Buisson, Renee M Ludlam, Guglielmo Mastroserio, Steven Rossland

Instrumentation and Methods for Astrophysics

Lessons learned from ongoing coordination between NRAO/GBO and LEO NGSO satellite constellations

Bang D. Nhan, Christopher G. De Pree, Sheldon Wasik et al. (+3 more)

With the increased demand for spectrum usage in recent years, particularly with the expansion of NGSO satellite systems for broadband internet and cellular services, radio astronomy observatories located at remote sites have been faced with the challenge of increasingly detrimental RFI exposure from ubiquitous satellite downlinks. With the help of the U.S. NSF, NRAO and the radio astronomy community have spearheaded collaboration efforts with the commercial NGSO operators to develop different coordination techniques to alleviate the impacts of these downlink signals in radio astronomy scientific observations. This paper summarizes the ongoing coordination efforts, spectrum interference avoidance schemes, and a case study on community participation of the Operational Data Sharing (ODS) system between RAS and NGSO operators. We highlight some of the essential lessons learned from these collaborations and potential application of the ODS system to other potential spectrum stakeholders.
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All authors Bang D. Nhan, Christopher G. De Pree, Sheldon Wasik, Aaron Lawson, Daniel Bautista, Frank Schinzel

Fluid Dynamics

A Splitting Scheme for Dispersive Shallow Moment Equations

Ullika Scholz, Robin Paar and Manuel Torrilhon

The well-known Shallow Water Equations (SWE) are used for modeling incompressible free-surface flows whenever the shallowness allows for a vertical-averaging; i.e., vertical effects are negligible in comparison to horizontal ones. But vertical averaging comes with the price of losing information along the vertical axis. Moment models for shallow flow contain information on the vertical velocity and pressure profile despite being dimensionally reduced. A class of these models incorporating a non-hydrostatic pressure have been introduced before as Dispersive Shallow Moment Models (DSM). However, no method for solving the non-stationary equations has been presented yet, mainly because it was unclear how to compute the pressure equation in the form of the divergence-free constraint. We rewrite the pressure equations of the DSM models in the form of a Poisson-like problem to enable their solution with a projection-type splitting scheme. For the linear equations, we present the calculations for the generalized model and discuss the non-linear case. We state the first two linear models and the corresponding nonlinear counterparts. Finally, we introduce a hybrid Finite-Volume Finite-Difference method and discuss the non-stationary numerical results for an experiment with periodic boundary and uneven bottom topography.
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Materials Science

Grain-boundary-mediated kinetic arrest in graphite-to-diamond transformation

Zuzanna Malinowska-Trzmielak, Vilmos Neuman and Mark Wilson

The graphite-to-diamond transition exhibits striking variability under high-pressure, high-temperature (HPHT) conditions, producing diamond, graphitic phases, or metastable, mixed diamond-graphite nanocomposites despite similar synthesis conditions. Existing atomistic models, largely based on idealised single-crystal graphite, do not explain the persistence of partially transformed intermediate states under HPHT conditions. Here, using large-scale molecular dynamics simulations, we show that precursor grain structure governs graphite-to-diamond transformation pathways by decoupling diamond nucleation from cooperative transformation propagation. Grain boundaries first facilitate local sp$^3$ nucleation, after which diamond growth propagates within individual grains but becomes arrested at crystallographically mismatched grain boundaries. As a result, structurally heterogeneous graphite stabilizes kinetically arrested mixed sp$^2$-sp$^3$ states, whereas large or single-crystalline domains favour cooperative bulk transformation into diamond. Our findings identify structural heterogeneity as a missing control parameter alongside pressure and temperature, reframing metastable transformation products as kinetically trapped states arising from precursor microstructure rather than thermodynamic intermediates. Precursor crystallinity therefore emerges as a practical control parameter governing graphite-to-diamond transformation pathways.
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Strongly Correlated Electrons

Loop-current orderings in SU($N$) two-leg fermionic ladder through duality symmetries

M. Habchy, F. Rose and P. Lecheminant

We investigate the formation of loop-current ordered phases in half-filled SU($N$) two-leg fermionic ladders. Using a low-energy approach, we uncover the existence of non-perturbative duality symmetries relating four competing orders. Two of these orders correspond to loop-current ordered phases that spontaneously break the time-reversal symmetry and describe charge currents circulating in a staggered pattern either around the plaquettes or along the diagonals of the ladder. These unconventional phases are shown to be dual to conventional (charge and bond) density-wave phases through an exact density-current duality symmetry existing on the lattice. From a perturbative renormalization group approach, we find that these phases for $N>2$ are stabilized in a half-filled SU($N$) two-leg Hubbard ladder with an additional SU($N$) Hund's interaction. The effect of a small doping on these phases is also discussed.
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Materials Science

Ferroelastic instability in rutile TiO2 and thermodynamic suppression of the CaCl2-type phase

Jared Pohlmann, Anjy-Joe Olatunbosun and Kenneth Park

We investigate the role of the CaCl2-type (Pnnm) phase in the high-pressure transformation of rutile TiO2, whose experimental signature has remained elusive. While analogies with other rutile-type oxides suggest such an intermediate, TiO2 typically exhibits a direct transformation to higher-coordination phases such as baddeleyite. Using an all-electron density functional framework combined with density functional perturbation theory, we show that rutile TiO2 undergoes a ferroelastic instability characterized by the development of an orthorhombic strain and a double-well energy landscape at 13.5 GPa. This instability is associated with the softening of the C11 - C12 elastic combination and the condensation of a B1g phonon mode, involving coordinated rotations of TiO6 octahedra that lower the symmetry to the Pnnm structure. Despite this clear elastic and dynamical pathway, enthalpy calculations show that the CaCl2-type phase is only weakly stabilized relative to rutile and remains energetically unfavorable compared to competing columbite and baddeleyite phases. Consequently, the Pnnm phase does not emerge as a stable high-pressure polymorph but instead exists as a transient or weakly metastable intermediate. These results demonstrate that the CaCl2-type phase represents the intrinsic ferroelastic response of rutile TiO2, yet is suppressed by thermodynamic competition, providing a consistent and unified explanation for its elusive experimental observation.
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Physics and Society · Cross-listed from cs.CY

The queer Hero versus the Fool bias of the queer trait: An archetypometric analysis of the collective portrayal of queerness in fictional stories

Ashley M. A. Fehr, Calla Glavin Beauregard, Julia Witte Zimmerman et al. (+4 more)

Visibility in media is pivotal for identity development and for broadening societal views of gender and sexuality. Queer representation has increased in recent years, yet damaging stereotypes and tropes persist. Here, we focus on queer portrayal and its perception by audiences in fictional stories (television, film, and literature) by studying characters by their quantified archetypes which are operationalizations of common conceptions such as Hero, Diva, and Outcast. We use the archetypometrics and Fandom's LGBTQIA+ datasets to study samples of fictional characters along the trait differential spanning straight to queer. We find, quantify, and explain a seeming paradox. The characters with the highest queer score present positive primary archetypes and are typically Heroes rather than Fools, Angels rather than Demons, and Adventurers rather than Traditionalists. But evaluation across many stories for the straight-queer trait itself reveals a strong collective-writing bias towards Fool (away from Hero) and no meaningful loading for the other two dimensions. Our analysis offers a population-scale view of the complexities of queer portrayal, while also pointing to risks in blindly training on many-authored story corpora.
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All authors Ashley M. A. Fehr, Calla Glavin Beauregard, Julia Witte Zimmerman, Danny Benett, Timothy R. Tangherlini, Christopher M. Danforth, Peter Sheridan Dodds

Solar and Stellar Astrophysics

Observations of the Halo Star HD 177566

William V. Dixon and Pierre Chayer

We have analyzed archival FUV and optical spectra of the hot halo star HD 177566. The star has an effective temperature $T_{\rm eff} = 33{,}000 \pm 1000$ K, surface gravity $\log g = 3.79 \pm 0.11$, and helium abundance $\log N({\rm He})/N({\rm H}) = -0.86 \pm 0.05$. Abundances of 13 additional elements are consistent with those of other halo stars, save for carbon, which is underabundant by about 1 dex. The low-order hydrogen Balmer lines are not well reproduced by our models. The diffuse lines of He I are often broader than predicted, but the use of more recent line-broadening parameters significantly improves the fit. Scaling our best-fit model to the star's optical and near-IR magnitudes yields an extinction $E(B-V) = 0.095 \pm 0.005$, consistent with literature values, but the resulting model underpredicts the star's FUV flux by a factor of two. The star's effective temperature and luminosity ($\log L / L_{\odot} = 3.50 \pm 0.08$) place it on the post-AGB evolutionary tracks of a star that evolved from the red horizontal branch. Its low carbon abundance, $\log N({\rm C})/N({\rm O}) = -2.18 \pm 0.21$, indicates that it did not experience significant third dredge-up while ascending the AGB.
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Instrumentation and Methods for Astrophysics

A Calibration Audit of a Gaia XP White-Dwarf Main-Sequence Binary Catalog: How Much the BP-Band Residual Contaminates at Its Bound and Above

Karan Akbari

A Gaussian-process classifier on Gaia DR3 XP spectra produced $\sim$30,000 white-dwarf main-sequence binary candidates (Li et al. 2025), with probabilities but no likelihood. The corrected spectra agree with external libraries to better than 2% below 400 nm and 1% redward (Huang et al. 2024), and that residual sits where a hot white dwarf also adds flux. We asked whether it contaminates the selection at its bound. It does, weakly. The spurious rate runs about 1.7 times the baseline there. Put into the blue band, 2% of total flux is a median 55% local excess across our MS templates, 27 times that number read locally. We inject a blue taper clipped to that bound, under the templates' published per-pixel errors, with a $\Delta\chi^2$ threshold standing in for the classifier. The spurious rate is $0.09\pm0.02$ across 20 seeds on a 0.053 baseline, 19 of 20 above it. The unclipped 2% taper, above the redward bound, gives $0.11\pm0.03$. At that taper the amortized posterior's 90% coverage falls to 0.85 from a clean 0.88 on the flat-model leg, with PIT uniformity rejected at $p<10^{-5}$ in all four seeds. The selection fails in bulk only above a 10-15% local excess, and the rate reaches 0.96 near 50%. A model-comparison gate certifies binarity only above a white-dwarf flux share near 0.05. At share 0.01, near the catalog's median of 0.0096, the $\Delta\chi^2$ preference inverts at a 20% local excess. Outside Huang's color-magnitude box, 40% of the catalog, the post-correction residual is not measured.
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High Energy Astrophysical Phenomena

The SPOTLIGHT Pulsar Search Pipeline: A GPU-Accelerated FFT Approach

Jyotirmoy Das, Jayanta Roy, Nishant Pradeep Deo et al. (+20 more)

We present the pulsar search component of SPOTLIGHT (Survey for sPoradic radiO bursTs via a commensaL multI-beam Gpu-powered Hpc at the gmrT), a GPU-accelerated commensal backend operating at the upgraded Giant Metrewave Radio Telescope (uGMRT). While SPOTLIGHT is primarily designed for real-time detection and localisation of fast radio bursts (FRBs), it simultaneously records a subset of beamformed data products for periodicity searches without requiring dedicated telescope time. To process the large data volumes generated by the survey, we have developed a scalable FFT-based pulsar search pipeline that combines radio-frequency interference mitigation, GPU-accelerated dedispersion and periodicity searches, multi-beam candidate sifting, efficient folding and machine-learning classification. Using population synthesis and archival uGMRT observations, we estimate that a fully operational SPOTLIGHT survey with 160 PC and one IA beam could discover $\sim$ 450 new pulsars, probing both high-sky coverage and faint pulsars over three and a half years of commensal observations. The pipeline has been validated on GMRT Cycle 48 and 49 observations (i.e. April 2025 to Mar 2026), successfully re-detecting numerous known pulsars with a wide range of Period, DM and flux densities, and is currently operational for SPOTLIGHT commensal data processing. We describe the SPOTLIGHT observing system, pulsar survey design, search parameter space, candidate-selection strategy, current status, and future developments. SPOTLIGHT demonstrates the scientific potential of commensal pulsar surveys and serves as a pathfinder for real-time, large-scale pulsar and transient searches in the SKA era.
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All authors Jyotirmoy Das, Jayanta Roy, Nishant Pradeep Deo, Karel Adámek, Wes Armour, Kshitij Bane, Jayaram Chengalur, Kenil Ajudiya, Chahat Dudeja, Sridhar Gajendran, Zhaocheng Gong, Param Joshi, Sanjay Kudale, Arpan Pal, Ujjwal Panda, Adityan S, Raghav Wani, Junhao Zhang, Deepak Bhong, Shelton Gnanaraj, Santaji N. Katore, Mekhala Muley, Harshavardhan Reddy

Physics and Society

Self-similarity of mobility networks

Ying-Yue Lyu, Xiao-Yong Yan, Bin Jia et al. (+3 more)

Mobility systems of people and goods are inherently multi-scale, spanning levels of organization from individual cities to regions and nations. Understanding whether mobility networks exhibit similar patterns across these scales is important. Such similarity would point to common organizing principles, enabling insights gained at one scale to inform planning and management at others. Despite growing efforts to analyze mobility at multiple scales, such cross-scale similarity remains poorly understood, and renormalization provides a natural framework for addressing this question. Here, we propose a Neighbor-Limited Box Covering method to renormalize undirected weighted mobility networks. This method iteratively selects box centers in descending order of node strength, merges each center with a fixed number of its highest-weight neighbors to form a renormalized node, and aggregates edge weights between renormalized nodes to generate the network at the next scale. We apply this technique to uncover multi-scale structures of real-world inter-city human mobility and freight trip networks in China and find that the topological structures, weighted structural features, and dynamic processes all exhibit self-similarity across these multi-scale mobility networks. Moreover, we find that the constituent nodes in most renormalized nodes show a strong spatial cohesion, and the boundaries of them closely follow existing political and socio-economic borders, even though the method does not explicitly incorporate any spatial information. Our study not only reveals the consistency of multi-scale inter-city mobility patterns, but also provides important insights into their spatial organization. Furthermore, our method is applicable to mobility networks of different sizes and has potential as a powerful tool for the multi-scale analysis of various other real-world complex systems.
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All authors Ying-Yue Lyu, Xiao-Yong Yan, Bin Jia, Jobst Heitzig, Ziyou Gao, Jürgen Kurths

Soft Condensed Matter

A strong-coupling theory for polarizable symmetrically charged walls with counterions only

Ladislav Šamaj, Alexandre P. dos Santos and Emmanuel Trizac

A pair of parallel polarizable planar walls at distance d is considered. The walls are symmetrically charged with a uniform surface charge density, neutralized by mobile point counterions moving between them. The case of repulsive particle images is studied in the strong-coupling (SC) regime. Of interest is the dependence of the effective inter-wall interaction (pressure), mediated by the mobile counterions, as a function of the distance d. It is shown that previous virial SC single-particle theories work well at small d when the dielectric jump is small; for intermediate and large dielectric jumps they are inadequate even in the SC region. Here, we propose a Wigner-type SC theory based on harmonic deviations of particles from their ground-state monolayer or bilayer Wigner structures formed inside the space between the dielectric walls. Our Monte-Carlo simulations are in very good agreement with the Wigner SC predictions, even down to moderate coupling constants ($\Xi > 10$).
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Nuclear Theory

Magnetised Dense Nuclear Matter in Neutron Stars: A Relativistic Mean-Field Study of the Equation of State

Mojdeh Banafsheh

We study the static response of dense neutron-star matter to a prescribed magnetic-field strength within a deliberately minimal and internally consistent relativistic mean-field (RMF) baseline. The model includes neutrons, protons, electrons, and muons in beta equilibrium and charge neutrality, with a uniform external magnetic field incorporated through Landau quantisation of the charged species. The equation of state is evaluated self-consistently at zero temperature, while moderate finite-temperature effects are estimated through leading-order degenerate Sommerfeld corrections. Magnetic pressure anisotropy is included through the Maxwell contribution in the no-magnetisation approximation. The purpose of this baseline is to isolate the hierarchy of magnetic-field effects before introducing additional microphysics or dynamical magnetic-field evolution. We compare the linear QHD-I parameterisation, used as a stiff benchmark, with the nonlinear GM1 model as a more realistic reference. The results show that canonical magnetar-scale fields produce negligible changes in the bulk core equation of state, while visible Landau-quantisation and pressure-anisotropy effects emerge only as the field approaches the strongly quantising regime. The comparison between QHD-I and GM1 further shows that nuclear-model dependence dominates over static magnetic-field corrections up to the field strengths explored here. As an exploratory diagnostic, we use the isotropised equation of state to estimate the sensitivity of ordinary TOV mass–radius sequences to the prescribed magnetic field. This should not be interpreted as a fully anisotropic magnetised-star calculation. Anomalous magnetic moments, hyperons, quark degrees of freedom, and dynamical magnetic-field evolution are left for future extensions.
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