Statistical Mechanics
Papers
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Sunday 20 September
We study the one-dimensional long-range self-avoiding walk in the grand-canonical ensemble where the statistical weight of a jump of length $r$ decays algebraically as $r^{-(d+\sigma)}$. Using large-scale Monte Carlo simulations with an efficient irreversible update scheme, we obtain high-precision estimates of the critical fugacity $z_c$, the universal Binder ratio $Q_N^c$, the correlation-length exponent $\nu$, and the anomalous dimension $\eta$. For $\sigma>1$, the critical fugacity varies smoothly with $\sigma$, while the Binder ratio and the critical exponents remain consistent with the short-range universality class. For $\sigma \le 1$, by contrast, the results clearly depart from short-range behavior, identifying $\sigma=1$ as the boundary between long-range and short-range regimes. In the long-range Wilson-Fisher regime with $1/2 < \sigma \leq 1$, $\eta$ agrees with the long-range Gaussian-fixed-point prediction $\eta_{\mathrm{GFP}}=2-\sigma$, whereas $Q_N^c$ and $\nu$ vary nontrivially with $\sigma$ and exhibit discontinuous jumps at $\sigma=1$. These findings are in good agreement with the recently proposed universality diagram in the $(d,\sigma)$ plane for long-range O$(n)$ models, with the self-avoiding walk corresponding to the $n\to0$ limit.
Quantum Physics
Stochastic Reconfiguration as Statistical Filtering for Overparameterized Neural Quantum States
Stochastic reconfiguration (SR) is the standard optimizer for neural quantum states (NQS), but modern NQS often have far more parameters than Monte Carlo samples. We show that in this regime the diagonal shift is more than a numerical stabilizer. It acts as a statistical filter for finite-sample generalization. At a fixed wave function, SR is ridge regression from tangent features to the centered local energy. Its residual is the expressivity gap, the part of imaginary-time evolution outside the current tangent space. This gap is orthogonal to the tangent space in population, but finite batches make it act as noise that SR can overfit. The shift therefore balances shrinkage of useful update directions against variance from fitting sampled residuals. Exact diagnostics on a $4\times4$ Heisenberg graph separate two effects of overparameterization. Larger tangent spaces help when they reduce the expressivity gap, but they can hurt when they overfit a fixed gap. In a $100$-site transverse-field Ising family trained with a foundation NQS, validation risk is U-shaped in the shift while variance decreases, matching the noisy-ridge model. This view leads to multi-shift SR (MS-SR), which averages independent ridge solves at data-adaptive shifts to form a richer, lower-variance spectral filter. Checkpoint-local experiments show that MS-SR lowers validation risk and update variance relative to the fixed-shift SR baseline. We further compare MS-SR and SR in paired online training continuations, with independent endpoint energy evaluations and a separate update-cost benchmark.
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Atomic Physics
Energy and Angular-Momentum Redistribution in Hydrogen Migdal Ionization
MARVEL's first direct observation of Migdal ionization in neutron scattering marks an experimental milestone and opens a new avenue for probing electronic response to nuclear recoil. Hydrogen, both the simplest atom and a constituent of its molecular target, provides a controlled benchmark. Within the nonrelativistic sudden approximation, we compute its energy-differential and integrated ionization probabilities with the full recoil phase. At the recoil parameter $\beta\equiv v_N/(\alpha c)=1.04$, the full-to-dipole spectral ratio rises from $0.43$ when the emitted-electron energy is $1\%$ of the hydrogen binding energy to $5.0$ when it is $2.3$ times that energy. Near $\beta=10$, partial waves with orbital angular momentum $\ell\ge3$ carry more than $90\%$ of the calculated continuum probability. An independent bound-state-closure evaluation verifies the absolute normalization: at eight recoil values, its ionization probabilities agree with the continuum-integrated results to relative discrepancies below $4.4\times10^{-7}$. These results extend the hydrogen dipole response to the fast-neutron regime and establish energy and angular-momentum redistribution as linked consequences of resolving the recoil phase across an atom.
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Instrumentation and Detectors
ARGUS: an experiment-agnostic framework for detector-health monitoring in particle physics
Every particle-physics experiment builds detector-health monitoring, and many end up rebuilding it, because a first system written under commissioning pressure often proves too rigid to maintain. ARGUS (Automated Anomaly-detection, Run-quality and General Unified Surveillance) is a configuration-driven framework that separates what is generic in this problem (the health monitors, their validation, and the reporting) from what is not (the data schema and the thresholds). Standing it up for a new detector requires a data adapter and a configuration file, not a rewrite. Detector health is judged by four independent monitors: expert cuts, which are authoritative; a machine-learning second opinion that is additive and off by default; a trend forecast that gives early warning before a threshold is crossed; and a reference-histogram comparison with pluggable statistical tests. The monitors are compared and never merged, and an alerting layer turns their flags and warnings into deduplicated notifications. We demonstrate the full chain on a synthetic reference detector with planted pathologies and a fault-injection campaign that manufactures ground truth: the cuts recover every planted pathology with no false positives, the machine-learning monitor reaches a ROC AUC of 0.896 on injected faults and extends coverage to fault classes no cut was written for, the forecast flags a drifting channel before its cut fires, and the histogram comparison catches every planted shape distortion while holding its configured false-positive rate on clean pairs. A second demonstration shows the framework adapting to a reorganized file layout with no change to code or configuration. Every result and figure in this paper regenerates from the code alone. The framework has been implemented for two particle-physics experiments, where it is under evaluation; adoption decisions rest with the collaborations.
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Optics
$f$-2$f$ self-referencing for silicon nitride photonics via a heterogeneously integrated lithium niobate layer
Heterogeneous integration combines complementary material properties in a single photonic platform. Here, we demonstrate on-chip $f$-2$f$ self-referencing in a heterogeneously integrated Si$_3$N$_4$/LiNbO$_3$ platform, in which supercontinuum generation in a Si$_3$N$_4$ waveguide and second-harmonic generation in a LiNbO$_3$ layer are spatially separated and linked by adiabatic escalator couplers. Pumped by a 1560 nm mode-locked laser with 75 pJ on-chip pulse energy, we detect the carrier-envelope offset frequency with 30 dB signal-to-noise ratio in 300 kHz resolution bandwidth. A comparative measurement confirms that the second harmonic originates in the LiNbO$_3$ layer and indicates opportunity for further improvements through periodic poling. These results establish heterogeneous Si$_3$N$_4$/LiNbO$_3$ integration as a viable building block for self-referenced ultrafast pulse sources in low-loss Si$_3$N$_4$ photonics.
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Quantum Physics
Simultaneous Reduction of Observables and Measured Qudits in Entanglement-Assisted Quantum Local Recovery
For a general entanglement-assisted or unassisted quantum error-correcting code, a set of erasures, and an associated repair group, we propose a linear algebraic procedure to compute a reduced set of observables and a reduced repair group of codeword qudits for correcting the given erasures. The procedure has cubic complexity in the repair group size and the computed set of observables has the smallest possible size for correcting the given erasures. We specialize the general procedure to quantum codes constructed from Euclidean and Hermitian orthogonality, and provide closed-form upper bounds on the size of reduced repair groups for those special cases. Based on these closed-form bounds, we propose quantum counterparts of the information locality of classical local recovery.
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Fluid Dynamics
Wall-modelled large-eddy simulation of turbulent channel flow with unstable stratification
Unstable thermal stratification modifies near-wall momentum and heat transport, causing the mean velocity profile to depart from the classical logarithmic law and complicating wall modelling for turbulent mixed convection. We develop a buoyancy-modified logarithmic-quadratic wall model for incompressible Poiseuille–Rayleigh–Bénard flow. The model combines an approximately linear relation between the near-wall mean temperature and mean streamwise velocity with a thermally modified mean-gradient representation inspired by mixing-length scaling. A priori assessments using wall quantities from the direct numerical simulation (DNS) database show that the calibrated wall law reconstructs near-wall velocity and wall-function-equivalent eddy-viscosity profiles. We implement the wall model in wall-modelled large-eddy simulations (WMLES) at friction Reynolds numbers up to $Re_\tau\approx6000$ and Rayleigh numbers up to $Ra=10^{10}$. For cases with DNS reference profiles at $Ra=10^8$ and $10^9$, the maximum pointwise absolute relative errors are $3.6\%$ for the mean velocity and $1.9\%$ for the mean temperature. For cases with available DNS global-transport data, the maximum relative deviations in the Nusselt number $Nu$ and skin-friction coefficient $C_f$ are $11.7\%$ and $15.9\%$, respectively. The WMLES reduces the mesh count by factors of approximately $195$–$542$ relative to the corresponding DNS meshes. For the $Ra=10^{10}$ and $Ri_b=0.1$ case, extrapolation of reference DNS resolution strategies gives a mesh count of order $10^{11}$, approximately three orders of magnitude larger than the present WMLES mesh count. We also examine how the balance between shear and buoyancy reorganises flow structure, and we identify signatures consistent with the coexistence of streamwise-elongated motions resembling very-large-scale motions and buoyancy-associated streamwise rolls.
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Astrophysics of Galaxies
Hierarchical Dynamics within Molecular Clouds: Type 4 Scaling Relations of Molecular Clouds in the Second Galactic Quadrant
We present a statistical study of the hierarchical structure of molecular clouds in the second quadrant of the Galactic midplane (139.75 deg <= l <= 159.75 deg, -5.25 deg <= b <= 8.25 deg), based on high-sensitivity 12CO and 13CO J = 1-0 data from the Milky Way Imaging Scroll Painting survey. Using DBSCAN and a non-binary Dendrogram algorithm, we identify 2,912 13CO clouds. Type 2 (multicloud, single-tracer) scaling relations show arm-dependent trends: the power-law index of the linewidth-size relation is about 0.32 in the Local Arm and about 0.42 in the Perseus and Outer Arms. The classical Keto-Heyer relation is weak in the Local Arm but present in the Perseus and Outer Arms, with a slope of about 0.3. The virial parameter is anti-correlated with cloud size, mass, and surface density, consistent with previous surveys. Type 4 (single-cloud, single-tracer) scaling relations exhibit stronger internal correlations. The linewidth-size index spans about 0.3-0.8 and correlates positively with sonic Mach number, indicating that the relation is not universal but depends on cloud compressibility. While substructures do not follow the conventional surface-density-based Keto-Heyer relation, a volume-density formulation restores a clear virial scaling, with evolutionary tracks aligning along lines of constant virial parameter. Moreover, the structural complexity of molecular clouds, characterized by the relationship between the number of substructures and the min_delta parameter, correlates with surface density rather than sonic Mach number, contrary to results from turbulence-only magnetohydrodynamic simulations. Together, these results are more consistent with a gravity-regulated hierarchical dynamical picture than with a purely turbulence-supported scenario.
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High Energy Physics (Phenomenology)
Exploring interference between $P_{c \bar c}$ resonances and background in the pion-induced reaction
We present a phenomenological study of the near-threshold $\pi^- p \to J/\psi n$ reaction, focusing on the interference effects between the $s-$channel $P_{c \bar c}$ resonances and non-resonance background. This reaction provides a complementary probe to photoproduction for investigating the nature of the hidden-charm pentaquark states. Using an effective Lagrangian approach, we construct scattering amplitudes for $J^P=1/2^-$ and $3/2^-$ $P_{c\bar c}$ states under two spin-parity scenarios, with the background dominated by the $t-$channel $\rho$ meson exchange. We find that the interference can produce peaks, dips, or complex line shapes depending on the relative phase, in contrast to the simple resonance peaks commonly reported in previous theoretical studies. The two spin-parity scenarios yield qualitatively similar patterns, indicating that our main conclusion is robust. Given the current scarcity of experimental data for the pion-induced channel, we emphasize the urgent need for future measurements at J-PARC to understand the dynamics of the $J/\psi N$ interaction near threshold and to search for the heavy pentaquark states.
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Quantum Physics
Static classical-quantum-entanglement trade-offs: an entropic converse and single-letter characterizations
The direct static capacity region of a bipartite quantum state describes its asymptotic conversion into classical communication, quantum communication, and entanglement, with all communication directed from Alice to Bob. This paper gives a unified entropic converse for this region. The proof treats generated and consumed resources simultaneously and derives all three information inequalities for one local instrument. Its main ingredients are no-signalling, the chain rule, strong subadditivity, and continuity of conditional entropy. A supporting-hyperplane characterization leads to the static capacity formula, which is helpful in determining single-letterization of the capacity region. For a pure state of entanglement entropy $h$ subjected to erasure with probability $p$, the complete region is the convex hull of $0$ and $(0,-ph,(1-p)h)$, plus the unit-resource cone. This statement holds for arbitrary collective instruments by using subset-entropy inequalities related to earlier methods used for the dynamic capacity region of the erasure channel. Complete characterizations also hold for symmetrically extendible states and locally flagged pure-state mixtures. For maximally correlated states, the optimization over local instruments admits an exact matrix formulation and an additive outer bound. An explicit qubit example shows that a nonorthogonal discarded quantum memory can outperform every efficient instrument and every instrument with conditionally commuting discarded states. For states obtained by qubit dephasing of Schmidt-aligned pure states, an exact threshold characterizes when the static capacity formula vanishes, at every blocklength and after regularization. Full single-letter characterizations for general Hadamard states and for the remaining trade-offs for dephased states remain open, with sufficient additivity conditions identified.
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Plasma Physics
VEQDB: A Compact and Reconstructible Multi-Device Tokamak Equilibrium Database
Tokamak equilibria are commonly exchanged as gridded G-EQDSK files whose conventions, resolutions, and machine-specific formats impede cross-device comparisons and data-driven modeling. Here, we present VEQDB, an open, compact, and reconstructible fixed-boundary equilibrium database built on continuous MXH–Chebyshev geometry and independent physical-profile roots. By decoupling authoritative equilibrium physics from rectangular meshes, VEQDB enables continuous evaluation and metric differentiation at arbitrary application-demanded resolutions. Backed by an automated numerical validation pipeline, VEQDB is structured as an extensible repository for ongoing community expansion. Its inaugural release provides 13,291 accepted equilibria across 267 conventional and spherical tokamaks, encompassing parameter-sampled Grad–Shafranov solutions, G-EQDSK projections spanning EAST, MAST-U, and ITER scales, and controlled variation families with explicit provenance. Benchmark projections reproduce normalized flux maps with RMS errors between $1.09 \times 10^{-3}$ and $1.45 \times 10^{-3}$, while compact JSON representations achieve an 89–96-fold size reduction relative to standard $129 \times 129$ G-EQDSK files. The complete initial release occupies 41~MB in raw JSON and 18~MB in compressed archives, and all records successfully passed independent reload and evaluation tests. VEQDB establishes an extensible, provenance-preserving foundation for equilibrium studies, reduced-order surrogate modeling, and cross-machine workflows.
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Mesoscale and Nanoscale Physics
Non-Markovian Quantum Dynamics of Exciton-Polaritons
Exciton-polaritons, hybrid light-matter quasiparticles formed when a material interacts with a confined electric field, have experimentally been shown to exhibit mesoscale coherent quantum propagation that remains robust at room temperature. However, an accurate and direct quantum dynamical simulation of this phenomenon that does not resort to semi-classical approximations is prohibitively expensive computationally, limiting the microscopic understanding of the rich dynamical interplay among phonons, photons, and electrons under collective light-matter coupling. To address this fundamental challenge, we develop a non-Markovian master equation approach which enables the fully quantum mechanical simulation of non-equilibrium exciton-polariton dynamics and captures phonon-induced decoherence and dissipation beyond the conventional Markovian limit. To carry out this task, a procedure is developed in which the wave vector space is coarse-grained and each diagonal element of the density matrix is evolved in parallel. To demonstrate the utility of this approach, we simulate exciton-polariton transport in TIPS-pentacene. We find that our approach reasonably captures the experimentally observed renormalization of the polariton group velocity, which originates from the phonon-induced non-Markovian Lamb shift. We further show that this renormalization cannot be reproduced within conventional Markovian theories.
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High Energy Physics (Phenomenology)
QCD thermodynamics through the crossover as a gas of confining strings with repulsive interactions
We investigate QCD thermodynamics in the intermediate-temperature regime using a gas of confining strings supplemented by excluded volume (EV) corrections. In this description, the discrete hadron resonance spectrum is replaced by an exponentially growing open-string spectrum characterized by a Hagedorn temperature $T_H$, related to the confining string tension. With a common EV parameter shared by mesons and baryons, the model gives a good description of bulk lattice-QCD thermodynamics above the pseudocritical temperature. Among the values considered, $T_H \simeq 300\,\text{MeV}$ provides the best agreement, lower than the value $T_H \simeq 320\!-\!340\,\text{MeV}$ inferred from ideal-string-gas fits to the vacuum hadron spectrum. A simultaneous calibration of the mesonic and baryonic EV parameters gives $b_M \simeq 0.19\,\text{fm}^3$ and $b_B \simeq 0.73\,\text{fm}^3$. Within the present spectral ansatz, the larger baryonic EV parameter indicates that stronger effective suppression is required in the baryon sector, although noticeable tensions remain in several conserved-charge observables.
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Astrophysics of Galaxies
Tracing Interstellar Gas in Quiescent Galaxies Using Na I D and Ca II H&K Absorption
For over two decades, Na I D ($\lambda \lambda5891.58, 5897.56$ Å) absorption has been the primary optical tracer of cool, neutral gas in galaxies. In contrast, Ca II H&K ($\lambda \lambda$3934.78, 3969.59 Å), which traces both neutral and ionized gas, has been comparatively unexplored. Here, we present a comparative study of the Na I D and Ca II H&K interstellar absorption lines using spatially resolved MaNGA IFU spectroscopy of 140 red geyser galaxies (local quiescent systems hosting low-luminosity AGN with bisymmetric ionized outflows) and a control sample of 140 quiescent galaxies. Using Gaussian fits to the Na I D and Ca II K lines, we measure gas velocity and dispersion. We find that the Ca II reservoirs are up to ~ 6 times larger in area, twice as radially extended, and have ~ 1.7 - 1.8x broader line widths than Na I D. Furthermore, Na I D shows a direct dependence on dust reservoir size, but the correlation vanishes for Ca II. In only ~ 20% of galaxies do the Na I D detections extend beyond dust regions, but this fraction jumps to ~70% for Ca II. Using these findings, we argue that dust plays a significant role in shielding Na I D from ionizing radiation, whereas Ca II, with its higher ionization potential, is not as dependent on shielding and can more easily survive beyond regions of dust. Na I D and Ca II trace distinct gas components, and studying both together provides a more complete picture of gas flows in galaxies.
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Quantum Physics
Radial Coarse Graining Restores Vacuum Majorization in Wigner Phase Space
Quantum uncertainty limits how strongly Wigner functions can concentrate in phase space. It is commonly conjectured that the vacuum Wigner function continuously majorizes that of any Wigner-positive state. However, by constructing Wigner-positive states whose localized quantum coherence lowers their Wigner entropy below the vacuum value, we show that this conjecture is incorrect. We restore vacuum majorization at finite resolution by integrating single-mode Wigner functions over concentric radial energy shells, obtaining probability vectors majorized by that of the vacuum for all Wigner-positive states and for Wigner-negative states with non-negative shell weights. Anchoring these shells to a fixed oscillator frame breaks affine symplectic invariance, rendering this relation strict for every non-vacuum Gaussian pure state. For Wigner-negative states, the persistence of negative shell weights defines a radial negativity scale with Airy-edge semiclassical asymptotics for highly excited Fock states. Operationally, we combine the majorization relation with partial transposition to obtain a two-mode entanglement criterion directly evaluable from radially binned joint homodyne outcomes without state reconstruction.
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Fluid Dynamics
Cascade-driven fragmentation-aggregation transitions in decaying turbulence
In decaying turbulence, the turbulent cascade is not merely a passive background for breakup but an evolving stability boundary that dynamically selects the fragmentation-aggregation pathway. As turbulence decays, the Hinze scale sweeps through the bubble-size distribution, progressively eliminating the breakable population and driving a transition from a mixed breakup-coalescence regime to a self-sustaining pure-coalescence state. Our model predicts a critical turbulence decay exponent $m=5/3$, a transient mixed breakup-coalescence regime, and a late-stage pure-coalescence state with a universal coalescence hazard. Interestingly, the transient breakup acts as a catalyst that amplifies mixed-regime bubble growth relative to pure coalescence. Results from our direct numerical simulations of decaying homogeneous isotropic turbulence as well as high-Reynolds-number duct-flow experiments collapse onto the model predictions when expressed in terms of the measured decay rate. These results replace the conventional instantaneous Hinze criterion with a non-equilibrium, cascade-controlled framework for turbulent fragmentation and aggregation.
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High Energy Physics (Phenomenology)
Initial-state control of vorticity–shear competition in longitudinal $\Lambda$ polarization in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36\,\mathrm{TeV}$
We investigate how the transverse initial energy-density distribution controls the second sine harmonic of longitudinal $\Lambda$ polarization in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36\,\mathrm{TeV}$. We use (3+1)-dimensional Particle-In-Cell Relativistic ideal hydrodynamics and the Becattini–Buzzegoli–Palermo isothermal local-equilibrium prescription. Across the twelve selected initial states, the kinematic-vorticity contribution $P_{z,s2}^{\omega}$ is negative, whereas the kinematic-shear contribution $P_{z,s2}^{\Xi}$ is positive. Changing the initial energy-density normalization $e_{\mathrm{peak}}$, transverse smoothing width $\sigma_\perp$, or reduced impact parameter $b_0$ modifies the relative magnitudes of the two contributions rather than merely rescaling their sum. Reducing the transverse smoothing width $\sigma_\perp$ generally strengthens both contributions, whereas increasing the initial energy-density normalization $e_{\mathrm{peak}}$ can preferentially weaken $P_{z,s2}^{\Xi}$ and reverse the total harmonic. At fixed $e_{\mathrm{peak}}$, the impact-parameter dependence is mainly shear driven for narrower transverse smoothing and mainly vorticity driven for broader transverse smoothing. Applying the Liu–Yin prescription to the two tested hydrodynamic backgrounds reverses the total sign, showing that the sign depends on the polarization formula as well as on the fluid fields. Our results obtained with ideal hydrodynamics and the ILE prescription have the same sign and order of magnitude as the ALICE measurements for peripheral Pb–Pb collisions in the $50$–$70\%$ centrality interval, showing that such a positive harmonic can arise from an initial-state-controlled, shear-dominated balance at decoupling.
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High Energy Astrophysical Phenomena
A dynamic magneto-ionic environment around a long-period radio transient
Faraday rotation provides one of the most direct probes of magnetized plasma along the line of sight, from the large-scale Galactic magnetic field to compact plasma environments local to radio sources. In particular, temporal variations in rotation measure can trace changes in the density, magnetic-field strength, or geometry of the Faraday-rotating medium, as observed in radio pulsars and fast radio bursts. Long-period radio transients (LPTs), a recently identified class of coherent radio sources with periods of hundreds to thousands of seconds, remain poorly explored because their physical nature is still uncertain. Here we present full-Stokes observations of the 421-s LPT source CHIME J0630+25 and report, for the first time, extreme rotation measure (RM) variability from approximately -400 to -1630 rad m^-2. The rapid RM changes occur on short timescales, including a difference of approximately 50 rad m^-2 between two consecutive rotation periods and a sudden change of approximately 536 rad m^-2 within approximately 2500 s. Compared with other radio-emitting sources, CHIME J0630+25 occupies an unusual region of the DM-RM plane: despite its very small DM of approximately 22 pc cm^-3, |RM| reaches over 1.6 x 10^3 rad m^-2, far exceeding that expected from the interstellar medium and pulsars. The fast and large-amplitude RM variations should arise from a compact, structured, and rapidly evolving magneto-ionic environment local to the source, possibly associated with a compact binary system.
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Saturday 19 September
General Physics
Effects Induced by the Inclusion of the Symmetric Derivatives of the Vector Potential Affinors in Modified Electrodynamics
This work continues the study of the real vector field theory.It shows how the potentials can be used to derive the field and dynamical variables of the wave electrojeitonic field generated by an electrically charged point particle.The derived expressions provide the angular distributions of the instantaneous electrojeitonic radiated power emitted by an charged particle in arbitrary motion. The results predict the dominance of longitudinal electrojeitonic radiation from ultrarelativistic charged particles.Keywords: electrojeitonic field, longitudinal electrojeitonic waves, electrojeitonic radiation.
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General Physics
Enhancement of Gravitationally Induced Entanglement via Quantum Squeezing
Gravitational generation of quantum entanglement on squeezed coherent states in a system of two quantum mechanical particles is explored. The particles are modeled as harmonic oscillators, and their gravitational interaction is described by an interaction potential. Dynamics of the gravi- tationally induced entanglement is explored using the linear entropy of entanglement. An analytical expression for the linear entropy is obtained via Gaussian integration and covariance method. In the short-time weakly coupled regime, it is observed that the entanglement is proportional to the square of the time interval, square of the interaction strength, and proportional to the squeezing parameters of the modes. These results provide insights into the effects of quantum squeezing on entanglement generation in systems with gravitational interactions. Analytically and numerically it is shown that momentum squeezing can enhance gravitationally induced quantum entanglement.
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High Energy Physics (Phenomenology)
Chiral Phase Structure and In-Medium Modifications of Charmed Meson Masses within SU(4) extended Linear-Sigma Models
We extend the Polyakov-loop-enhanced linear-sigma model to encompass four flavors and utilize it to analyze the light, strange, and charmed meson mass spectrum as it transitions from the vacuum into a hot and dense medium. Within the mean-field approximation, we determine the masses of scalar ($0^{++}$), pseudoscalar ($0^{-+}$), vector ($1^{--}$), and axial-vector ($1^{++}$) meson states, encompassing both open- and hidden-charm constituents, as functions of temperature $T$ and baryon chemical potential $\mu_B$. With parameters calibrated to the vacuum spectrum, the charm degree of freedom proves essential for an accurate description of observed masses, and charmed states acquire their in-medium modifications from the light and strange condensates that modify their valence quarks. Each species seems to undergo melting along its distinct trajectory, yet all transitions occur within a narrow band surrounding the chiral transition. The open-charm $D$-meson functions as a precise indicator of chiral restoration: its mass increases substantially across the transition and reflects the non-strange condensate, whereas hidden-charm states remain largely unaffected and serve as reference standards for the surrounding matter. We establish that transition points from three independent measurements delineate the chiral phase boundary ($T_c$, $\mu_B$), whose curvature matches lattice-QCD predictions and which persists as a crossover throughout the examined range, exhibiting no critical endpoint.
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Fluid Dynamics
Learning Stiffness Dependent Fluid Structure Dynamics from Coarse Flow Representations
This paper develops a data-driven framework for long-term prediction of fluid–structure interaction (FSI) dynamics, focusing on the flow-induced vibration (FIV) of a flexible plate. A stiffness-conditioned neural evolution operator jointly represents the Eulerian flow field and Lagrangian structural state. The plate is represented by 101 ordered structural tokens carrying nodal coordinates and velocities, with nondimensional bending stiffness as a global conditioning variable. Bidirectional cross-attention couples fluid and structural representations within a hybrid CNN-Transformer architecture. Trained with staged multi-step autoregressive rollouts and symmetry-reflected trajectories, a single operator captures three stiffness-dependent response regimes: deflected–flapping, deflected, and flapping. The predicted trajectories preserve the principal flow structures, structural oscillations, and dominant frequencies, while blind 1000-step rollouts remain bounded. The operator also interpolates to stiffness values excluded from training. To reduce sensitivity to under-resolved near-wall gradients in force reconstruction, we develop a differentiable aerodynamic-force module based on the derivative-moment transformation (DMT). Conventional wall-stress surface integrals are replaced by an enclosed 2D curve integral around the core vortex region, enabling accurate reconstruction of lift and drag. A Signed Distance Function (SDF) and smoothed Dirac-delta formulation make the integration fully differentiable while preserving gradient flow. The proposed framework provides an accurate and differentiable surrogate for stiffness-dependent FSI dynamics, enabling efficient parameter studies and future stiffness optimization for flow-energy-harvesting applications.
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Materials Science
Electrothermal Compact Drift Model of TiO$_2$ Memristors: Verilog-A Implementation and Dimensionless Regime Mapping
Compact models of titanium-dioxide memristors used in circuit simulation commonly follow the drift formulation of Strukov et al. and assume a constant ionic mobility, although oxygen-vacancy migration is thermally activated and Joule self-heating is unavoidable. We present ATDM (Arrhenius Thermally Activated Drift Model), a minimal electrothermal compact model that couples the drift equation to a lumped heat balance through an Arrhenius mobility. It adds one thermal state while preserving the electrical state variable, the relation $v=iR(x)$, and the isothermal limit. The model is implemented in Verilog-A, compiled with OpenVAF, and simulated as a device in ngspice, where it reproduces an independent reference implementation within $0.009\,\%$ of the peak voltage and recovers the isothermal excursion at zero activation energy. A dimensionless formulation introduces a thermal lag $\varepsilon$ and an effective switching number $\Theta$. Across $2.5\times10^{5}$ simulations, $\Theta$ orders the state-variable excursion over the tested quasi-static domain with a robust relative scatter of $4\,\%$ and no fitted constant, and the $(\varepsilon,\Theta)$ regime map quantifies when the quasi-static thermal reduction remains valid. Under current drive, the stroboscopic map of the reduced model is proved to be strictly increasing, which excludes period-doubling and chaos in that reduction. Within the sampled ranges, a variance-based sensitivity analysis identifies the effective thermal resistance as a first-order contributor to self-heating, while separate capacitance sweeps show a weak influence of the thermal capacitance in the quasi-static regime. The results characterize the specified model with representative, uncalibrated parameters.
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Atomic Physics
The use of coherent states in the excitation and ionization of atoms by a short symmetric pulse
We propose a new model for describing the excitation of atoms by short symmetric pulses. The theory is based on the impulse approximation and incorporates a confining potential approximated by a harmonic oscillator. Results are presented for a wide variety of parameters, including field intensity and laser frequency. Permitted and forbidden transitions are analyzed in detail. The photon energy spectrum presents peaks attributed to multiphoton absorption. Our model demonstrates robustness and reliability, paving the way for addressing more complex scenarios.
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General Relativity and Quantum Cosmology
Testing Van der Waals black holes using black hole photon rings
The Van der Waals black hole (BH) is a non-Kerr model in Anti-de Sitter (AdS) spacetime that exhibits characteristic thermodynamic phase transitions. Whether the physical validity of parameters such as the BH molecular volume $b$ and pressure $P$ is feasible still requires observational verification. As a sensitive probe of strong gravitational fields, the BH photon ring directly carries spacetime geometric information, making it an ideal object for model testing. In accordance with the spacetime metric associated with this BH, this study obtains the null geodesic equations for photons and conserved quantities, determines the photon sphere conditions and radii via effective potential analysis, investigates the photon ring classification and radiative properties, and employs measurements from the Event Horizon Telescope (EHT) to place constraints on parameters and simulate the optical appearance. The results show that the molecular volume parameter $b$ significantly regulates the radius of the photon sphere radius, photon ring structure, and the luminosity. Within a specific interval, the model exhibits a high degree of agreement with the EHT measurements for M87* and Sgr A*. This interval not only satisfies the energy conditions (weak, strong, and dominant) but also corresponds to a stable Van der Waals-type phase transition region. Furthermore, the photon ring can distinguish between the Van der Waals BH and the Schwarzschild BH: due to the small-black-hole-large-black-hole (SBH-LBH) phase transition and microstructural discontinuities, the photon ring of the Van der Waals BH is particularly sensitive to the parameter $b$, whereas the Schwarzschild BH lacks these features. This work uses the photon ring to probe BH molecular models, linking its microstructure, spacetime geometry and observational signatures, and provides a new way to derive BH microphysics from observations.
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High Energy Physics (Theory)
Loop Equations for Multi-Matrix Models
We revisit the combinatorial loop-equation method for computing planar disc amplitudes in multi-matrix models with polynomial potentials. We develop a procedure which organises the Schwinger-Dyson constraints by the level of their boundary insertions and, when the resulting system closes, produces an algebraic equation for the planar disc function. Using this method we recover the disc partition functions associated with fixed, mixed, and free boundary conditions in the three-state Potts model, previously obtained by saddle-point methods. As a novelty we derive an algebraic equation for the fixed-boundary resolvent of the three-state Potts model with unequal quadratic and cubic couplings. We further show one can compute the disc partition function for several unsolved two- and three-matrix models. These examples demonstrate that loop equations provide a practical route to identifying and solving sectors of multi-matrix models beyond the standard one- and two-matrix cases.
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Instrumentation and Detectors
Radiation hardness characterization of SiPM sensors for Low Earth Orbit space missions
This work presents a comprehensive radiation hardness characterization of SiPM devices for space-based applications: FBK NUV-HD-MT and NUV-HD-LowCT (1$\times$1, 3$\times$3, and 6$\times$6~mm$^2$) and Hamamatsu S14160 MPPCs with equivalent active areas. Total Ionizing Dose (TID) tests were performed at the ESA/ESTEC Co-60 facility with a level of dose up to 20~krad in silicon, while displacement damage effects were evaluated using 100~MeV protons with a fluence up to $1.12\times10^{11}$~p/cm$^2$ at the Paul Scherrer Institute. Radiation damage in SiPMs manifests through two main mechanisms: ionizing energy loss and non-ionizing energy loss (NIEL), which increases dark current and dark count rate. In this work, breakdown voltage, dark current, and quenching resistance were systematically measured as functions of accumulated dose and fluence. Gain and dark count rates were indirectly measured from the characterized electrical parameters. Both technologies exhibit remarkable stability of most of the functional parameters across all dose levels, while dark current shows predictable increases significantly more pronounced under proton irradiation due to displacement damage. Based on these results, both FBK and Hamamatsu devices are confirmed suitable for Low Earth Orbit (LEO) mission environment.
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General Physics
Comparing Mass-Varying Neutrino Dark Energy Models with DESI DR2: Cosmological Constraints and Bayesian Evidence
We investigate late-time cosmic acceleration in mass-varying neutrino (MaVaN) dark energy scenarios, where the neutrino mass is coupled to a dynamical quintessence field through a conformal interaction. Starting from the coupled conservation equations, we derive the corresponding background evolution equations for three related scenarios: a constant dark-energy equation of state with a constant coupling (Case-I), an exponential neutrino mass linked to an exponential potential under an adiabatic minimum-tracking approximation (Case-II), and a CPL-type time-varying equation of state with constant coupling (Case-III). For each case we obtain the neutrino and dark energy density evolution and the corresponding Hubble parameter, and use an MCMC analysis (emcee) to test the models against DESI DR2 BAO data, the compressed Planck CMB likelihood, and three supernova compilations (Pantheon+, DES-SN5YR, Union3), taken one at a time. Across the three cases, $H_0$ and $\Omega_{m0}$ move together in a way set mainly by which supernova sample is used, following the pattern already seen in other DESI DR2 analyses. A nonzero coupling stays consistent with the data in most fits, though its size, and sometimes its sign, depend on how it enters the model and on the priors chosen for the underlying parameters. The resulting neutrino mass bounds range from about $0.06$ to $0.3\,\mathrm{eV}$, depending on the case and dataset combination. Comparing the Bayesian evidence of each case with flat $\Lambda$CDM gives a mixed picture, with no case preferred throughout, so we regard these results as suggestive rather than firm evidence for a coupling between neutrinos and dark energy.
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Lattice Field Theory
Gradient Flow for the Jet Transport Coefficient: A Quenched Lattice Benchmark
We apply the gradient-flow framework to determine the nonperturbative medium contribution to the jet transport coefficient $\hat q$ using quenched lattice QCD in the temperature range $0.76T_c \leq T \leq 2.25T_c$. The calculation focuses on the leading-twist contribution at leading order for an asymptotically energetic quark propagating through a thermal pure-gluon plasma. In the infinite-energy limit, the operator-product expansion expresses $\hat q/T^3$ in pure gauge theory as the product of a perturbative short-distance coefficient and the entropy density $s/T^3$. The latter is determined from the gradient-flow energy-momentum tensor at three lattice spacings for each temperature and the former is estimated perturbatively at one-loop order. We find that $\hat q/T^3$ is strongly suppressed below $T_c$, rises rapidly across the deconfinement transition, and remains approximately constant at $\hat q/T^3\simeq1.1$ throughout the deconfined temperature range studied. This is statistically consistent with the previous quenched lattice determination based on a different renormalization procedure, providing a nontrivial validation of the gradient-flow framework for the jet transport coefficient. The systematic treatment of operator renormalization and matching provided by gradient flow becomes particularly important in full QCD, because the need to renormalize quark operators and account for their mixing with the gluonic sector can likewise be addressed within the same framework.
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Quantum Physics
Complete Detector Records and Contextual Source Laws in a Retrocausal Spin Model
Detector outcome probabilities can be independent of a later measurement setting even when earlier timestamps, detector seeds, or environmental records depend on that setting. We characterize complete-record preservation for a positive wrapped-Cauchy retrocausal spin source. An antipodal identity yields necessary and sufficient conditions for passive and environmental readouts, and source compensation permits a common normalized analyzer for source spins and prepared continuations. Gaussian controller and reset calculations distinguish inverse raw history weights from normalized thermal operations. A quantum instrument provides an operational benchmark, whereas a setting-dependent separable source produces setting-dependent statistics at an earlier joint probe. For two equal-width contexts, a calibrated weak probe requires a minimum source change of $\operatorname{sech}(2g)/8$ in trace distance for exact protection at every nonzero strength. The signal–source-change tradeoff is sharp for this pair of contexts. A contextual positive-history construction recovers the isolated hidden law and preserves records for a specified class of finite adaptive quantum apparatuses, subject to quantum calibration and restricted field access. Direct readout of an added likelihood field distinguishes two future axes with unit probability. The analytical results are supported by continuous-angle and quantum-trajectory simulations, deterministic quadrature, and exhaustive enumeration of a finite policy class. The analysis concerns the specified statistical models; their microscopic physical realization remains an open question.