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Physics

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Monday 6 July

Chaotic Dynamics

Recurrence and anti-recurrence patterns reveal an antiperiodic fingerprint that survives into chaos in the Duffing–Holmes oscillator

Arturo C. Marti and Edson D. Leonel

The periodically forced Duffing–Holmes oscillator possesses a discrete symmetry under sign reversal of the coordinate combined with a half-period shift of the drive. When this symmetry is dynamically realized, the system supports antiperiodic solutions, whose state at any instant is the point reflection of the state half a driving period earlier. We show that a standard recurrence plot (RP) is blind to this symmetry, whereas a complementary anti-recurrence plot (anti-RP), built from the cross recurrence between a trajectory and its point-reflected image, detects it directly. Across four regimes – periodic and chaotic single-well motion, and antiperiodic and chaotic two-well motion – the anti-RP is empty when the attractor occupies one well and densely diagonal when the motion respects the symmetry. Crucially, the antiperiodic fingerprint persists into the chaotic two-well regime, where the anti-recurrence rate stays high relative to the ordinary one ($\mathrm{RR}_a/\mathrm{RR}\approx0.8$) despite the chaos. Recurrence quantification of both matrices separates order from chaos, while the anti-RP independently distinguishes one- from two-well, symmetry-respecting dynamics, giving a compact classification of all regimes. Requiring only a time series and the symmetry operation, the anti-RP is a model-free probe of dynamical symmetry for any system with a sign-reversal invariance, including experimental signals where phase-averaged observables fail.
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High Energy Physics (Experiment)

Measurement of the $b$-jet identification efficiency in dileptonic $t\bar{t}$ events using proton-proton collision data at $\sqrt{s}=13.6$ TeV collected with the ATLAS detector

The ATLAS Collaboration

This paper presents the performance of the identification of jets containing $b$-hadrons ($b$-jets) for the GN2 algorithm, a transformer-based model for jet flavour tagging, using data collected by the ATLAS detector at the LHC. The analysis uses proton-proton collision data recorded in 2022 and 2023 at a centre-of-mass energy of $\sqrt{s} = 13.6$ TeV, corresponding to an integrated luminosity of 56 fb$^{-1}$. The $b$-jet identification efficiency and jet flavour composition are extracted simultaneously from a sample enriched in top-quark pair events ($t\bar{t}$). This efficiency is measured as a function of the jet transverse momentum in the range of 20-400 GeV and across six intervals of cumulative efficiency as derived in simulated $t\bar{t}$ events: [100%, 90%], [90%, 85%], [85%, 77%], [77%, 70%], [70%, 65%], and [65%, 0%]. The GN2 algorithm demonstrates significant performance improvements over its predecessor DL1d, achieving up to a factor of two (three) higher rejection of light-flavour (charm-flavour) jets at the same $b$-jet efficiency. The measured efficiencies in data are compared with simulation to derive correction factors ranging from 0.9 to 1.3. The total uncertainty is around 1% for jets with transverse momentum larger than 60 GeV in the [65%, 0%] interval of cumulative efficiency.
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Materials Science

Data-driven atomistic modelling of hybrid halide perovskite passivation

Laura-Bianca Paşca, Henry J. Snaith and Volker L. Deringer

Molecular passivation of surface defects is key to improving the optoelectronic performance of hybrid halide perovskite materials, but the underlying atomistic mechanisms are incompletely understood. While machine-learned interatomic potentials are now widely used to simulate complex molecular and crystalline systems, their application to experimentally-realistic scenarios - such as molecules coordinating to perovskite surfaces - is still far from trivial. Here, we describe a multistep training pipeline, resembling continuous fine-tuning used for large language models, to underpin atomistic modelling and computational experiments in this domain. Our protocol involves two components: (i) a large, curated, and open dataset of diverse metal and hybrid halide perovskite structures ('hyP-26'); and (ii) a small, specialised dataset for an amino-silane molecule passivating the surface, providing highly specific information for fine-tuning. We apply this approach to explore collective behaviour at a mixed-composition halide perovskite surface passivated with a varying coverage of amino-silane molecules, revealing an evolution of interactions with increasing molecular surface coverage.
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Materials Science

High-temperature operation of III-nitride high-electron-mobility transistors

Yi-Chen Liu, Jacklyn Zhu, John Niroula et al. (+3 more)

High-electron-mobility transistors (HEMTs) made with III-nitride materials are of potential use in high-temperature electronic applications including power electronics, communications, aerospace and space exploration. However, the demands of such applications make it essential to understand the thermal limits and performance evolution of III-nitride HEMTs. Here, we analyze the high-temperature operation of III-nitride HEMTs, examining the impact on material properties, device structure, and circuit-level behavior. We explore the role of critical device layers - including barrier and channel engineering, substrate selection, and passivation strategies - in mitigating high-temperature-induced effects, and evaluate the thermal stability of III-nitride HEMTs in logic, radiofrequency, and power electronics applications. We also highlight key remaining challenges in the design and optimization of III-nitride devices for high-temperature applications.
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All authors Yi-Chen Liu, Jacklyn Zhu, John Niroula, Hridibrata Pal, Tomas Palacios, Savannah R. Eisner

High Energy Physics (Phenomenology)

Parametric Resonance of Higgsed Vector Dark Matter: Inflationary Initial Conditions and Sourced Displacements

Imtiaz Khan, Salvatore Capozziello, G. Mustafa et al. (+2 more)

Parametric resonance in a Higgsed Abelian sector provides an efficient mechanism for producing vector dark matter, but its viability depends crucially on the origin of the initial dark-Higgs displacement that seeds the resonance. In this work, we investigate this initial-condition problem in a weakly coupled Abelian-Higgs theory with potential $V=\lambda_4(\phi^2-v^2)^2/4$, using the calibrated nonlinear broad-resonance relic map together with a stochastic inflationary analysis of the dark-Higgs condensate. We show that a minimal light-spectator realization fails under standard inflationary duration: while broad resonance and isocurvature constraints require \( \phi_0/H_I \gtrsim 3.3\times10^4, \) the stochastic equilibrium and finite-duration random walk produce only \( \phi/H_I=\mathcal O(1). \) This large displacement mismatch is robust against order-of-magnitude variations in the resonance efficiency and broadness threshold, establishing a model-independent obstruction to the stochastic branch. We then identify a distinct classically sourced branch, generated by a negative Hubble-induced mass, in which the condensate tracks a time-dependent minimum, \( \phi_0=\kappa H_*/\sqrt{\lambda_4}, \) and the radial fluctuation remains heavy during inflation. In this case, the fixed-$e/\lambda_D$ relic scaling shifts from \( m_X\propto \lambda_4^{5/8}H_I^{-3/2} \) to \( m_X\propto \kappa^{-3/2}\lambda_4 H_*^{-3/2}. \) We derive the simultaneous consistency conditions for this sourced branch, including broad resonance, adiabatic tracking, perturbativity, sub-Planckian displacement, thermal non-erasure, spectator backreaction, and control of inflationary vector fluctuations. Our results establish that Higgsed-vector resonance is not merely a dark-matter production mechanism, but a sensitive probe of the inflationary and reheating dynamics that determine its initial conditions.
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All authors Imtiaz Khan, Salvatore Capozziello, G. Mustafa, Niamat Ullah, Farruh Atamurotov

Statistical Mechanics

A universal emulator for planar Ising lattices

Riccardo Ben Alì Zinati and Alessandro Codello

We introduce the notion of an Ising emulator for two-dimensional Ising models: a broad class of flat, unit-edge-length lattices can be represented as site- or bond-diluted supercells of a single host lattice, for which the Feynman–Vdovichenko/Kac–Ward solution is fixed once and for all. We construct explicit square and triangular emulators and show that a single transition matrix, supplemented by lattice-specific binary masks, gives all the thermodynamic quantities of interest for both ferro- and antiferromagnetic couplings. We apply the framework to all eleven Archimedean lattices, to all twenty 2-uniform lattices – whose thermodynamics is obtained here for the first time – and to several pentagonal lattices, and show that the same construction extends directly to fractal and disordered Ising models, with no modification to the underlying machinery.
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Quantum Physics

Quantum Spectral Anomaly Detection

Yewei Yuan, Michele Minervini, Mark M. Wilde et al. (+1 more)

A core task in quantum anomaly detection is to compute an anomaly score that quantifies how strongly a test quantum state deviates from a given quantum dataset assumed to be normal. Classically, principal component analysis (PCA) for centered data computes the anomaly score by evaluating the test sample relative to the subspace spanned by the selected leading eigenvectors. However, for quantum data that lack a standard centering, explicitly recovering principal eigenvectors, constructing full Gram matrices, or loading quantum-random-access-memory-style data can be more costly than estimating the anomaly score itself. To avoid these costs, we propose Quantum Spectral Anomaly Detection (QSPADE), which computes PCA-like anomaly scores directly from the spectrum of the average state of the normal dataset. By replacing hard PCA rank selection with a smooth, temperature-controlled spectral threshold, QSPADE makes near-threshold spectral components contribute partially to the anomaly score. This makes the score vary continuously rather than jump when a borderline component is included or excluded, and makes it less sensitive to noise or arbitrary hard cutoffs near the threshold. In the zero-temperature limit, QSPADE recovers the hard-projector PCA score. The proposed measurement-based quantum detector can be calibrated with a sample complexity independent of the data dimension. Numerical simulations show that QSPADE behaves like kernel-PCA on encoded classical data and detects changes across a transverse-field Ising transition without predefined order parameters. Consequently, QSPADE gives an efficient framework for both quantum-kernel anomaly detection on encoded classical data and the monitoring of quantum-native systems where diagnostic observables are unknown.
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All authors Yewei Yuan, Michele Minervini, Mark M. Wilde, Nana Liu

Biological Physics

Energetic Protection, Monotonicity and Switching Far from Equilibrium

Uğur Çetiner

At equilibrium, the ratio of two steady-state probabilities is a Boltzmann factor, set by a free-energy difference. Such ratios are the natural, normalization-independent readouts of both thermodynamics and information processing, and are often used as a measure of fidelity in biophysical systems. What becomes of these ratios once a system is driven from equilibrium, where the Boltzmann factor no longer holds? Representing Markov processes as graphs and their steady states as averages over a distribution on spanning trees, the arboreal distribution, we track the ratio $\pi_i/\pi_j$ under driving along energetic edges, where detailed balance is broken, relative to its equilibrium value. Our central finding is that a chosen ratio can stay exactly locked to its equilibrium value arbitrarily far from equilibrium, a phenomenon we call energetic protection, whenever an algebraic equality between spanning-tree weights holds. Just as detailed balance constrains rates around cycles, energetic protection constrains weights across trees, providing a new mechanism for robustness against fluctuations in the driving force, such as variations in ATP concentration. Away from this equality, single-edge driving collapses the response onto two arboreal coefficients and forces it to be monotonic, so nonmonotonic single-edge control is impossible at any strength. With two energetic edges, protection and monotonicity combine into a thermodynamic switch that holds a function at its equilibrium value for as long as desired and releases it sharply. Equilibrium is known for the limits it places on information processing. We show that new constraints, both no-go principles and exact invariances, survive far from equilibrium. These results reveal how the localization of energy expenditure governs the functional logic of nonequilibrium systems in physics and biology.
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Solar and Stellar Astrophysics

The steady incompressible ideal free-boundary flows of a hydromagnetic star

B. C. Low and S. W. McIntosh

This self-contained theoretical study treats incompressible, free-boundary flows in a gravitating, ideal hydromagnetic star abutting vacuum, centered on the steady field-aligned flows of Chandrasekhar, Prendergast and Tsinganos, together with a novel family of steady cross-field flows, all as solutions of the axisymmetric Tsinganos equation. In the absence of compressive waves and shocks, an incompressible fluid evolves by its frozen-in magnetic field propagating as transverse Alfvèn waves along the field lines, with pressure reacting instantly in place. The origin of the steady flows rests on the Parker theory that everywhere-continuous flows are the exception rather than the rule because of a basic propensity for tangential field/flow discontinuities. Astrophysical viscosity and electrical resistivity are not zero but are significant only over scales much smaller than macroscopic scales. Such near-ideal fluids have the same propensity for tangential discontinuities but the near-discontinuities readily dissipate by small-scale, viscous-resistive magnetic reconnections. The study treats the strictly ideal fluid separately in its own right, to construct a conceptual understanding of the turbulent creation of a steady flow in a self-organizing near-ideal fluid via irrepressible energy loss and field-topology changes as episodic reconnections run out of free energy. The study suggests that metastable storage of steady vortices and twisted fields is a natural product of the solar internal dynamo, to explain a recent, multi-instrument observation of solar-coronal eruptions persisting coherently in preferred longitudinal locations over solar-rotational timescales.
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Materials Science

Phase-field modeling of elastically driven abnormal grain growth

Yazhuo Liu, Yin Zhang, Kunqing Ding et al. (+6 more)

Grain-refined metals typically exhibit high strength, yet their engineering applications are often constrained by grain coarsening under thermo-mechanical loading. Recent experiments have revealed abnormal grain growth (AGG) in ultrafine-grained Ni thin films subjected to cyclic loading at room temperature. Unlike conventional AGG, which generally requires significant plastic deformation or high temperatures, this phenomenon occurs within the regime of macroscopic elastic deformation. This AGG is characterized by the preferential growth of grains with an in-plane <100> orientation aligned with the loading direction. Here, we investigate the underlying physical mechanisms by combining phase-field simulations with micromechanical analysis. The results indicate that elastic energy reduction provides a thermodynamically plausible driving force for this orientation-selective grain growth. Phase-field simulations reveal the evolution kinetics of AGG and confirm that local grain geometry and stress states play critical roles in determining the grain growth pathway. By applying this framework to systems with varying elastic anisotropy, we establish a general approach for investigating elastically driven AGG in polycrystalline materials.
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All authors Yazhuo Liu, Yin Zhang, Kunqing Ding, Yichen Yang, Alejandro Barrios, Xavier Maeder, Olivier Pierron, Xing Liu, Ting Zhu

Materials Science

Semiconductor nanofilms as thermal phonon polarizers: competing effects of scattering selection rules and boundary mode conversion

Vasumathy Ravishankar and Navaneetha K. Ravichandran

Phonon scattering selection rules are known to control heat flow through bulk solids. Here we show that these selection rules also modulate heat flow through nanoscale semiconductor films, although through a previously-unexplored mechanism. Using first-principles calculations, we expose a competition between these selection rules and phonon mode conversion at boundaries of nanoscale films, that drives mode-polarized heat currents at cryogenic temperatures ($\le$ 100 K). This polarizing effect is stronger in materials like indium phosphide, where selection rules based on large velocity differences between phonon branches amplifies the longitudinal acoustic (LA) phonon contribution to thermal conductivity by restricting their intrinsic scattering events, while boundary mode conversion in nanoscale films suppresses it by depopulating the LA phonons. The resulting transverse-polarized non-equilibrium phonons will enable symmetry-selective engineering of phonon coupling to electrons, strains and defects in nanoscale films, that is difficult to achieve in bulk solids.
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Astrophysics of Galaxies

Toward Unbiased Abundance Measurements in Inhomogeneous $\mathrm{H\,II}$ Regions

Eric Habjan, Christopher Faesi, Kathryn Kreckel et al. (+10 more)

Probing the chemical content of the interstellar medium (ISM) in nearby galaxies provides key insight into their chemical evolution and informs our interpretation of galaxies at higher redshift. However, nonlinear structure in the ISM, including density and temperature inhomogeneities, can bias chemical abundance measurements and systematically affect empirical calibrations derived from them. In this work, we investigate biases in $T_e$-derived oxygen abundance determinations and explore the physical properties that correlate with them. We combine $\mathrm{[O\,II]}\lambda\lambda3726, 3729$ measurements from SITELLE with a full suite of optical emission lines obtained with MUSE. From auroral emission lines ($\mathrm{[N\,II]}\lambda5755$, $\mathrm{[S\,III]}\lambda6312$, and $\mathrm{[O\,II]}\lambda\lambda7320, 7330$) and nebular emission lines (including $\mathrm{[N\,II]}\lambda6584$ and $\mathrm{[S\,III]}\lambda9069$), we derive electron densities, temperatures, and chemical abundances for a sample of $\mathrm{H\, II}$ regions in five galaxies. We find that densities derived from the $\mathrm{[O\,II]}$ auroral-to-nebular ratio are $\sim10^3$ cm$^{-3}$, which is higher than the standard $\mathrm{[S\,II]}$ densities derived from nebular doublet ratios. We demonstrate that combining the $\mathrm{[N,II]}$ electron temperature with the density inferred from the $\mathrm{[O\,II]}$ auroral-to-nebular line ratio yields singly ionized oxygen abundances consistent with literature expectations for a prescription insensitive to density inhomogeneities. We also find that the $\mathrm{[S\,III]}$ temperature provides a reliable estimate of $T_{e,\mathrm{[O\,III]}}$, enabling robust measurements of doubly ionized oxygen abundances. Overall, these results indicate that the abundance discrepancy factor could be higher in more chemically evolved $\mathrm{H\, II}$ regions.
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All authors Eric Habjan, Christopher Faesi, Kathryn Kreckel, J. Eduardo Méndez-Delgado, Francesco Belfiore, Ryan J. Vaught, Brent Groves, Fabian Scheuermann, Thomas G. Williams, Ralf S. Klessen, Amirnezam Amiri, Kathryn Grasha, Simon Glover

High Energy Physics (Theory)

Polynomial Initial-State Jumps and Christoffel Transforms in Krylov Complexity

Abhishek Chowdhury and Ajit Prasad Mahapatra

At fixed Hamiltonian $H$, changing the initial state changes the cyclic pair and hence generally the Lanczos basis and spread. For every normalizable polynomial preparation $\lvert\psi_Q\rangle=N_Q^{-1/2}Q(H)\lvert K_0\rangle$, we reconstruct its state-Krylov problem exactly from reference cyclic data. The transfer assumes no integrability and applies on finite or infinite cyclic support. Reweighting the reference spectral measure by $\lvert Q\rvert^2$ gives a finite-band connector for every prepared amplitude and a finite-rank Christoffel-Darboux projection for cumulative probabilities and spread, without rerunning ambient-space Lanczos. Fixed-degree seeds preserve the limiting Jacobi coefficients of asymptotically constant chains. Every Charlier number-state jump obeys $K_r(t)\ge K_0(t)$, with strict inequality for $r\ge1$ away from revivals. At every fixed finite $r$, the Hermite endpoint has exact all-level amplitudes, whereas the continuous-$q$-Hermite chord chain of double-scaled SYK has an all-level root-free re-Lanczos reconstruction. Writing $D_r^{\rm H}$ and $D_r^{\mathrm{ch}}(t)$ for the mean absolute Fock and chord displacements, respectively, the bounds are $K_r\ge D_r^{\rm H}$ and $K_r(t)\ge D_r^{\mathrm{ch}}(t)\ge\lvert\overline n_r(t)-r\rvert$. Thus rebuilt spread bounds physical displacement and signed chord drift. At fixed $0\le q<1$ and time, $K_r(t)-D_r^{\mathrm{ch}}(t)\to0$ as $r\to\infty$, with both approaching the same folded-Bessel limit. In Liouville space, the exact unnormalized gap measure family on an open inverse-temperature interval determines the positive transition-resolved measure, assuming the thermal kernel is known and strictly positive and the requisite exponential moments exist. One cyclic solution can therefore be reused across polynomial seeds while separating physical propagation, basis response, and rebuilt spread.
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High Energy Astrophysical Phenomena

AU or pc? Inferring the distance of magnetized plasma near FRBs from propagation diagnostics

Wanjin Lu, Dongzi Li, Zhenyin Zhao et al. (+1 more)

Fast Radio Bursts (FRBs) are highly energetic, millisecond-duration radio transients. A significant fraction of repeating FRBs are found in magneto-active environments significantly different from typical interstellar medium, offering important insights into their origins and evolutionary pathways. Possible explanations range from companion winds to young magneto-active supernvae remnants. The spatial scales of the magneto-active environment is a major distinction of different models. In this work, we present a new method to estimate the physical scale of the magneto-active region surrounding FRBs by jointly analyzing measurements of temporal scattering ($\tau_\mathrm{scat}$), depolarization ($\sigma_\mathrm{RM}$), and Faraday rotation measure (RM) variations ($\left|\Delta \mathrm{RM}/\Delta t\right|$) in repeating sources. We systematically apply this method to all active repeaters with multiple RM measurements. Despite the coarse sampling and large uncertainties, the inferred distances tentatively favor SNR-scale magneto-environments for FRB 20190303A, FRB 20190417A, and FRB 20190520B, while still allowing binary-scale structures for FRB 20180916B and FRB 20201124A under plausible assumptions. Better sampling of propagation effects, together with future advances in simultaneous wideband measurements of multiple effects with CHORD and the DSA, has the potential to systematic discrimination among the origins of FRB magneto-environments and constrain progenitor evolution.
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All authors Wanjin Lu, Dongzi Li, Zhenyin Zhao, Fayin Wang

High Energy Physics (Experiment)

A three-step proposal for searching for light shining through walls in the X-ray band at the High Energy Photon Source

R. T. Chang, S. Feng, X. P. Geng et al. (+18 more)

Despite compelling observational evidence for dark matter (DM), its fundamental physical properties remain poorly understood. In this report, we propose a three-step light-shining-through-walls (LSW) experimental scheme utilizing the high-brilliance, high-energy X-rays from the ID21 Hard X-ray Imaging Beamline at the High Energy Photon Source (HEPS) to search for signatures of dark photons (DPs) and other weakly interacting slim particles (WISPs). The scheme includes three steps of LSW experiments: a short-term (several days) dedicated exposure experiment, a long-term (several years) synchronous accompanying experiment, and a WISP detection with strong magnetic fields. Projection results show that this HEPS-based LSW experiment can effectively constrain DP parameters in the 1 eV–400 keV mass range, covering unexploited parameter space of the existing X-ray LSW experiments. It provides a least model-dependent and most purely-laboratory approach for probing dark sector particles and advancing new physics research beyond the Standard Model gradually.
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All authors R. T. Chang, S. Feng, X. P. Geng, C. Y. Hu, H. T. Hu, Y. Y. Hu, Y. H. Huang, B. Liao, F. L. Liu, P. Luan, S. S. Lv, M. L. Qiu, S. K. Shao, Q. L. Shuai, Q. Tang, H. R. Wang, D. Wu, M. Y. Wu, J. S. Xie, Z. H. Zhang, Z. H. Zhang

Strongly Correlated Electrons

Near itinerancy and slow singlet formation in the triangular lattice NaRuO2

Charles C. Tam, Alon Hendler Avidor, Pritam Bhattacharyya et al. (+6 more)

NaRuO$_2$ forms a delafossite-like structure that contains triangular sublattices of edge-sharing RuO$_6$ octahedra. It shows no evidence of magnetic order down to 100~mK and persistent spin fluctuations, suggestive of a quantum disordered magnetic ground state. In order to characterize the physical regime from which this disordered state arises, we use resonant inelastic X-ray scattering (RIXS) and X-ray absorption spectroscopy (XAS) at the Ru-$L_{2,3}$-edge, along with pulsed high-field magnetization to characterize both the local electronic structure and the magnetic interactions. We infer significant spin-orbit coupling from XAS measurements. With RIXS, we observe intraorbital excitations, which are damped due to the near itinerancy of the band and suggestive of strong charge fluctuations. Corroborated by models of the high-field magnetization to a random singlet model, we propose a picture of a nearly itinerant system with strong magnetic and charge fluctuations that destabilize long-range magnetic order.
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All authors Charles C. Tam, Alon Hendler Avidor, Pritam Bhattacharyya, Yongseong Choi, Daniel Haskel, Sven Luther, Hlynur Gretarsson, Liviu Hozoi, Stephen D. Wilson

Mathematical Physics

Lower bound on the energy-momentum relation of the polaron

Steffen Polzer

For a class of polaron-type models, we establish a lower bound on the energy-momentum relation in terms of the vacuum overlap and the spectral gap of the total momentum zero Hamiltonian. We show convergence of the rescaled mean square displacement of the associated path measure to the inverse of the effective mass. We derive a probabilistic criterion for the absence of ground states at large total momentum.
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Instrumentation and Methods for Astrophysics

Trigger system for the Payload for Ultrahigh Energy Observations (PUEO) balloon-borne neutrino detector

Q. Abarr, J. Alfaro, P. Allison et al. (+67 more)

The Payload for Ultrahigh Energy Observations (PUEO) is a NASA balloon-borne instrument for the detection of ultra-high energy (UHE) neutrinos with energies above $10^{17.5}~\textrm{eV}$ via either the Askaryan effect or geomagnetic emissions from an upward-going air shower. The main instrument trigger system for PUEO is a fully digital supersample rate beamformer based on 24 Xilinx Radio Frequency System-on-a-Chip (RFSoC) digitizers sampling 192 channels operating at $3~\textrm{GSa/s}$ and a system clock frequency of $375~\textrm{MHz}$. The trigger implements frequency band conditioning, dynamic radio-frequency interference (RFI) rejection, and matched filtering, with significant emphasis on optimization to reduce both the power and resource usage while maintaining sensitivity. The system implements 48 total synthetic antenna beams with up to 8 antennas each, covering a $\sim25^\circ$ range in zenith and $\sim60^\circ$ range in azimuth. Preflight testing demonstrated a trigger performance of a minimum signal-to-noise ratio (SNR) of $\sim1.5$ using simulated signals while consuming between $5-7~\textrm{W}$ in the trigger logic.
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All authors Q. Abarr, J. Alfaro, P. Allison, J. Alvarez-Muñiz, T. Anderson, H. Barnett, A. Basharina-Freshville, J. J. Beatty, L. Beaufore, D. Z. Besson, M. Betts, R. Bose, D. Braun, B. Chamanbahar, P. Chen, Y. Chen, J. M. Clem, T. Coakley, A. Connolly, K. Couberly, L. Cremonesi, A. Cummings, P. Dasgupta, C. Deaconu, J. Flaherty, C. Godden, P. W. Gorham, C. Hornhuber, J. Hoffman, K. Hughes, A. Hynous, A. Jung, A. M. Kofman, Y. Ku, D. Kullgren, C.-Y. Kuo, P. Linton, L. Lisalda, T. C. Liu, W. Luszczak, S. C. Mackey, Z. Martin, K. McBride, C. Miki, J. Nam, R. J. Nichol, A. Novikov, A. Nozdrina, E. Oberla, S. Prohira, H. Pumphrey, D. Radomski, B. F. Rauch, R. Scrandis, D. Seckel, M. F. H. Seikh, J. Shiao, G. Simburger, J. Tutt, A. G. Vieregg, S.-H. Wang, D. Washington, C. Welling, P. Windischhofer, S. A. Wissel, C. Xie, J. Yao, R. Young, E. Zas, A. Zeolla

Quantum Physics

Routing Anonymity and Identifiability of Noisy Quantum Hardware

Ben Priestley and Mina Doosti

Present-day quantum computing is cloud-based, where a user submits a circuit to a service provider's proprietary backend hardware. While providers may wish to hide implementation details, scheduling choices, or even which physical device was used, noisy finite-shot outputs can carry backend-specific fingerprints: information imprinted in the classical output distribution that can reveal the backend identity. So far, such fingerprints have mostly been studied from a benchmarking perspective, with limited attention to privacy considerations for users and providers. This work develops the first formal framework for backend identifiability and its privacy implications. We introduce a backend-identifiability game and use it to formalise routing anonymity as a security notion for quantum cloud services. We show that backend identifiability is a hypothesis-testing problem and prove that, under passive i.i.d. access to a single backend, routing anonymity decays exponentially at the Chernoff rate. We also establish a utility-anonymity trade-off, imposing fundamental limits on how much backend-specific information can be removed from classical outputs without degrading their usefulness. In addition, we observe that, for noisy quantum hardware, identifying fingerprints are inherently an intermediate-depth phenomenon, and establish a depth principle using Pauli-transfer-matrix tools. We complement the theory with experiments on Amazon Braket on AWS, using ion-trap and superconducting quantum processors. We observe 87-90% classification between superconducting backends and 96-100% classification across physical platforms, and find that identifiability can survive natural forms of post-processing. Overall, these results establish routing anonymity as a distinct security requirement for quantum cloud computing, and provide a framework for quantifying and controlling the utility-anonymity trade-off.
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High Energy Physics (Phenomenology)

Spin Polarization of Proca Stars Formed by Gravitational Bose–Einstein Condensation

Jiajun Chen

We study the internal spin polarization of Proca stars formed by gravitational Bose–Einstein condensation of a three-component nonrelativistic vector field. In idealized periodic-box simulations, we decompose the aperture-averaged spin into a coherent net fraction, a local polarization fraction, and their ratio, thereby distinguishing genuine coherent core polarization from local spin density whose direction cancels inside the aperture. For independent vector components, condensation produces Proca stars that are sizably but not maximally polarized. Across an independent-component simulation ensemble, the coherent core-spin fraction has mean $\langle\chi_{\rm net}\rangle\simeq0.62$, with substantial realization-to-realization scatter. We interpret this scatter as the outcome of random elliptical polarization of the dominant component-space mode, rather than as evidence for a universal Proca-star spin fraction. This interpretation is supported by the core polarization matrix: its leading eigenvector provides an estimate of the ideal single-mode spin fraction, while the difference between this estimate and the directly integrated coherent spin tracks the departure of the core from a rank-one component-space state. The measured leading-eigenvector spin fractions are broadly compatible with an isotropic random-complex-vector model and less compatible with an equal-amplitude random-phase model. Correlated and circular initial data drive the dominant component-space mode toward the circular-polarization bound, giving the ordering independent $\rightarrow$ correlated $\rightarrow$ circular. These results show that internal polarization is a genuine vector degree of freedom of gravitationally condensed nonrelativistic Proca stars, and that the resulting core spin is controlled by the polarization of the dominant condensed mode rather than by a fixed universal value.
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Solar and Stellar Astrophysics

Circumbinary disk formation through AGB star winds

Shunquan Huang and Rebecca G. Martin

Circumbinary disks are commonly observed around post-asymptotic giant branch (post-AGB) star binaries, yet their formation and especially their long-term evolution remain unclear. We investigate this process using smoothed-particle hydrodynamics simulations of AGB star wind-binary interactions across different wind velocities, binary eccentricities, and mass ratios. When the wind is fast, or the companion is relatively low-mass, corresponding to the Bondi-Hoyle regime, the outflow remains largely unbound and forms a spiral density pattern. In contrast, slower winds and more massive companions lead to wind Roche-lobe overflow (WRLOF), where a circumsingle disk forms around the companion and efficiently transfers angular momentum to the outflow, producing a circumbinary disk. We perform simulations for over 600 binary orbital periods and find that the resulting disk properties depend sensitively on binary parameters, with higher eccentricities producing more extended and eccentric circumbinary disks, while lower mass companions reduce the disk density and growth rate. We further find that angular momentum transport within the circumbinary disk is dominated by spiral structures and shocks generated by the binary-wind interaction, corresponding to effective stresses comparable to or larger than the imposed viscosity. These results show that wind-binary interactions can naturally generate diverse circumbinary disk morphologies observed in AGB and post-AGB star systems.
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Solar and Stellar Astrophysics

The birth of Be star disks III. SPH models of localised mass ejections

A. C. Rubio, A. C. Carciofi, D. Baade et al. (+4 more)

Classical Be stars exhibit mass ejection events that feed their viscous decretion disks. Recent TESS space photometry and simultaneous spectroscopy revealed that these flickers are localised, short-lived, and associated with near-Keplerian rotating material close to the stellar surface. We aim to constrain the geometrical and dynamical conditions required for a localised surface ejection to generate a Keplerian decretion disk and to predict the corresponding photometric, spectroscopic, and polarimetric observables. Material, and the injection radius. The SPH outputs were post-processed with the radiative transfer code HDUST to obtain synthetic observables. We scaled the density of the models to match the reference flicker for the Be star f\,Car. A mildly super-Keplerian rotation of the injection volume, a high viscosity, and a mass-loss rate of the order $10^{-6}\,\rm M_\odot \, yr^{-1} \, str^{-1}$ are required for the ejected material to remain in orbit and form a small disk. The synthetic observables reproduce the behaviour of the reference flicker. The simulations confirm that during mass ejection the disk is asymmetric and dynamically evolving, and circularises within a few days after the end of the flicker. Models with too wide mass ejection angle or too high angular velocity fail to reproduce the observed light curve and line profile behaviour. The models are consistent with mass ejection happening very close to the stellar equator. Localised, short-duration, mildly super-Keplerian ejections combined with high viscosity and high mass-loss rates can account for the short-timescale variability of the circumstellar environment of Be stars. Be disks can be formed from such outbursts and realistic 3D injection geometries are essential to connect surface dynamics to disk build-up within the framework of the viscous decretion disk model.
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All authors A. C. Rubio, A. C. Carciofi, D. Baade, J. Labadie-Bartz, T. H. de Amorim, I. A. Gabitova, M. W. Suffak

Quantum Gases

Excitation spectra and rank tomography of finite MPS tangent spaces

Otto T.P. Schmidt and Iacopo Carusotto

We formulate the matrix product state (MPS) tangent-space excitation construction for finite, non-uniform systems with open boundary conditions, using the smooth full-rank stratum of the MPS variety as the variational manifold. The resulting linear tangent ansatz yields a projected-Hamiltonian eigenproblem for approximating excitation spectra. We further introduce a rank tomography that characterizes the particle-sector expressivity of the MPS tangent space. For number-conserving systems, we resolve the Schmidt ranks of reference states by particle number and derive an explicit relation between the resulting rank profile and the dimensions of the tangent-space sectors. This allows sector completeness and parametric deficiency to be determined directly from the reference state, without explicitly constructing a tangent basis, and provides a direct diagnostic of the sectorwise expressivity of the MPS excitation ansatz. We benchmark the finite-system construction on Bose–Hubbard chains against exact diagonalization, finding accurate low-lying excitation branches while identifying sector-dependent limitations of the linear tangent ansatz.
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Materials Science

A Distributional Framework for Generative Modeling of Molecular Crystals

Michael Kilgour, Alex Dong, Mark E. Tuckerman et al. (+1 more)

Molecular crystals are a highly polymorphic class of materials, with a single molecule commonly crystallizing via multiple packing patterns, making structure and property prediction very challenging. Crystal structure prediction typically comprises the production of sets of promising candidate structures, each considered in isolation rather than as samples in a thermodynamic distribution. Likewise, modern generative approaches to this problem, despite naturally sampling distributions of crystals, lack a concrete formulation of the distributions being sampled. Two components are required to impart meaning to the distributions of crystals generated under such models: a canonical parameterization, and a loss function which equilibrates the generated samples to some target distribution. We develop such a parameterization, and train energy-based generative flow networks (GFlowNets) to approximate the Boltzmann distribution over crystal structures for target molecules and space groups. Combined, these components comprise our MXtalGFlow framework for molecular crystal modeling. Going beyond sampling disconnected sets of low-energy structures, MXtalGFlow yields a thermodynamic distribution over crystal structures. We sample and analyze distributions of crystals for two molecules, each under two energy functions, a Lennard-Jones potential and the Universal Model for Atoms. We characterize the local structural basins about the known polymorphs, and identify additional as-yet un-reported packing modes with competitive probabilities to the known experimental structures. With MXtalGFlow, we illustrate how to define and train a model to sample a thermodynamically meaningful distribution of molecular crystals, and analyze such a distribution to glean useful information.
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All authors Michael Kilgour, Alex Dong, Mark E. Tuckerman, Jutta Rogal

High Energy Physics (Theory)

Thermal two-point functions in SYK and complex-time singularities

Ilija Burić, Chi-Ming Chang, Ivan Gusev et al. (+3 more)

We analyze the finite-temperature two-point function of the large-$N$ SYK model at intermediate couplings away from the infrared fixed point. Specifically, we examine its analytic structure in the complex time plane, tracking the complex-time singularities over a range of temperatures. The location of the leading singularity lies on the imaginary axis. It controls the short-time dynamics of operator complexity, defining an `effective temperature' for the correlator. The next-to-leading singularity lies outside the thermal strip set by the above effective temperature. It has been argued that this could be interpreted in terms of bouncing null geodesics in the emergent black hole geometry. Both these singularities persist all the way down to zero temperature. We discuss our observations and motivate the related emergent geometry using a kinematic space perspective.
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All authors Ilija Burić, Chi-Ming Chang, Ivan Gusev, Elizabeth Helfenberger, Andrei Parnachev, Mukund Rangamani

Mathematical Physics

Collision geometry of relativistic spinning particles

Simone Calogero

We investigate elastic binary collisions of relativistic spinning particles in special relativity. The spin of each particle is represented by an antisymmetric second order tensor. Assuming the conservation of total four momentum and total spin tensor, together with the mass shell and spin constraints, we formulate the collision problem in a fully Lorentz covariant setting. We show that the relativistic collision problem admits a simple geometric formulation, reducing the original system of conservation laws to the solution of a quadratic equation on a circle. This reduction yields a complete classification of the postcollisional states together with explicit reconstruction formulas for all postcollisional variables from the conserved quantities. In particular, there are generically only finitely many postcollisional states, with the maximal number equal to eight.
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High Energy Astrophysical Phenomena

The disk luminosity deficit as a tracer of receding disk during Soft-to-Hard transitions in Black Hole X-ray Binaries

Sai-En Xu, Bei You, Yi Long et al. (+4 more)

Tracing the evolution of the thin accretion disk during the soft-to-hard state transition in black hole X-ray binaries (BHXRBs) remains difficult because conventional spectral estimates of the disk inner radius become highly model-dependent once the thermal component weakens. We present evidence that the thin disk recedes during this transition, obtained from a systematic study of RXTE/PCA observations of 26 BHXRBs. In 24 outbursts, the disk luminosity decays exponentially in the soft state, then drops significantly below the extrapolated baseline. This thermal luminosity deficit is considered a signature of reduced accretion efficiency, caused by the outward receding of the optically thick disk. Under this framework, we found that the estimated characteristic truncation radius increases rapidly as the systems evolve through the soft-to-hard transition. This interpretation is supported by timing analysis: in observations with well-constrained power density spectra, the characteristic frequencies of broadband noise and low-frequency QPOs generally decrease as the inferred truncation radius increases, consistent with the expansion of a hot inner flow. The onset and rapidity of recession vary substantially across different sources and outbursts. Our results demonstrate that luminosity deficits provide a practical empirical tracer of thin disk receding during soft-to-hard transitions, when direct spectral radius measurements become unreliable.
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All authors Sai-En Xu, Bei You, Yi Long, Zhen Yan, Andrzej A. Zdziarski, Rui-Xiang Hu, Alex Markowitz

High Energy Astrophysical Phenomena

The emergence of X-ray emission lines during relativistic radio-jet formation in the changing-look active galactic nucleus 1ES 1927+654

Dev R. Sadaula, Sibasish Laha, Eileen T. Meyer et al. (+27 more)

We present results from a comprehensive multi-wavelength monitoring campaign of the changing-look active galactic nucleus 1ES 1927+654 during the onset and evolution of a relativistic radio jet $\sim$(May 2022 - August 2025), using observations from XMM-Newton, Swift, TNG, ZTF, VLA, and VLBA. The soft X-ray emission lines at $\sim 0.56$ keV and $\sim 1$ keV have appeared with variable strength and width during the formation of the nascent jet. We note that the $\sim 1$ keV feature has been persisting since the post-2017 flare phase. We also report the detection of a broad ($\sim 800$ eV) FeK emission feature at $(6-7)$ keV in the $\sim 70$ ks stacked EPIC-pn spectra, marking the first such detection, which historically was lacking in this source. The joint spectral fitting of XMM-Newton EPIC-pn and RGS data reveals the presence of ionized absorbers in 2022 ($\log{\xi\mathrm{/erg\ cm\ s^{-1}}}\sim 1.5\pm 0.3$, $\mathrm{N_H} \sim 2.5\pm 0.9\times 10^{20} \mathrm{cm^{-2}}$), but weaker than that detected during the high accretion state in 2018 (Eddington ratio, $\lambda_{\rm Edd}>1$). The absorption features further weakened in 2023-2025 and were marginally detectable ($\mathrm{N_H} \le 10^{20}\mathrm{cm^{-2}}$). The entire scenario is suggestive of a real-time transition of the accretion flow (from $\lambda_{\rm Edd}>1$ to $\lambda_{\rm Edd}\sim 0.3$) during which the winds become weaker and the jet starts to form and evolve. Furthermore, both the soft X-ray $(0.3-2)$ keV and 5 GHz radio fluxes, which increased by factors of $\sim 10$ and $\sim 60$, respectively, since 2022, have recently plateaued at elevated levels, indicating a stabilized accretion disk, corona, and jet configuration.
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All authors Dev R. Sadaula, Sibasish Laha, Eileen T. Meyer, Onic I. Shuvo, Main Pal, Ritesh Ghosh, Matteo Guainazzi, Fabio Pacucci, Stefano Bianchi, Luigi Gallo, Rostom Mbarek, Amelia M. Hankla, Fabio La Franca, Tahir Yaqoob, Megan Masterson, Erin Kara, Missagh Mehdipour, Claudio Ricci, Javier A Garcia, Timothy R. Kallman, Ralf Ballhausen, Mitchell C. Begelman, Alexander Philippov, Suvendu Rakshit, Francesca Panessa, Ehud Behar, S. Bradley Cenko, Federica Ricci, Ilaria Villani, James N. Reeves

High Energy Astrophysical Phenomena

Geminga and Monogem in the CTAO Era: Probing TeV Halos and Cosmic-Ray Transport

Youyou Li, Oscar Macias, Manuela Vecchi et al. (+1 more)

TeV halos around Geminga and Monogem (B0656+14) reveal regions of strongly suppressed diffusion near middle-aged pulsars. Determining the sizes and magnetic-field strengths of these slow-diffusion zones is important for modelling lepton transport and assessing their contribution to the local positron excess. The Cherenkov Telescope Array Observatory (CTAO) will provide arcminute-scale imaging of extended gamma-ray emission. We construct two-zone diffusion models for Geminga and Monogem with GALPROP v57, injecting electrons and positrons according to the pulsar spin-down history and following their propagation through an evolving slow-diffusion bubble and the ambient interstellar medium. Calibrating to HAWC and Fermi-LAT measurements, we forward-fold the models through official CTAO instrument response functions, including realistic diffuse and instrumental backgrounds. For 50 h observations, both halos are detected with high significance ($\sim 13$–$30,\sigma$) from either site. Under optimistic background assumptions, CTAO can distinguish changes of $\Delta\gamma_1 \simeq 0.2$ in the high-energy injection index and $\Delta B \simeq 2,\mu{\rm G}$ in magnetic-field strength. For Monogem, compact bubbles with $R_{\rm SDZ}\approx30,{\rm pc}$ can be distinguished from extended ($\gtrsim50,{\rm pc}$) cases, although very large bubbles remain degenerate because of the finite field of view. Using an alternative Galactic diffuse template in the fit changes detection significances and parameter sensitivities by $\lesssim10%$, indicating robustness against plausible diffuse-background mismodelling.
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All authors Youyou Li, Oscar Macias, Manuela Vecchi, Shinichiro Ando

Optics

Photon-conserving Raman soliton attractors in focusing and defocusing Kerr media

Weiye Huang, Junhong Yang, Tao Sun et al. (+6 more)

The sign of the Kerr nonlinear coefficient has long been regarded as irrelevant to the direction of the Raman-induced soliton self-frequency shift. Yet the standard generalized nonlinear Schrödinger equation (GNLSE) predicts a frequency shift that depends on the sign of the nonlinearity, which leads to an unphysical blue shift in the defocusing case. We resolve this inconsistency by deriving the time-domain form of the photon-conserving GNLSE (pcGNLSE) from its established frequency-domain counterpart. The derivation reveals that photon-number conservation imposes two sign modifications relative to the standard GNLSE: the Raman-shift coefficient acquires the absolute value of the Kerr nonlinear coefficient in place of its signed counterpart, and the self-steepening-Raman dissipation term likewise carries an absolute-value prefactor rather than a signed one. These two modifications jointly guarantee a universal spectral redshift and monotonically decreasing pulse energy during propagation, irrespective of the signs of the Kerr nonlinear coefficient and its frequency derivative. Applying the method of moments to the time-domain pcGNLSE with appropriate chirped ansätze, we derive closed-form evolution equations for five pulse parameters and establish explicit attractor conditions under which bright or dark Raman solitons propagate with constant peak power. Direct numerical integration of the pcGNLSE confirms all analytical predictions and demonstrates that the standard GNLSE fails qualitatively, predicting unphysical energy growth and spectral blueshift in the negative-nonlinearity regime. The results provide a rigorous analytical framework for Raman soliton dynamics in materials with negative third-order susceptibility, with direct implications for soliton-based devices in emerging semiconductor waveguide and microresonator platforms.
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All authors Weiye Huang, Junhong Yang, Tao Sun, Qian Gao, Peilong Yang, Jintao Fan, Günter Steinmeyer, Jinhui Yuan, Chao Mei