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Thursday 24 September

Applied Physics

Integration of p-type Cr2O3 on Ultra-Wide Bandgap AlGaN PolFETs with 2.5 kV Breakdown Voltage

We demonstrate UWBG AlGaN polarization-graded field-effect transistors (PolFETs) incorporating room-temperature sputtered p-type oxide Cr2O3 as a P-N heterojunction gate, enabling superior field management for lateral device breakdown compared to conventional Schottky gates. Devices using reverse-graded n-AlGaN contact layers achieved a record-low Rc of 0.56 {\Omega}-mm. The Cr2O3 gate exhibits a turn-on voltage VON > 3.5 V and a positive threshold voltage shift of +1.63 V relative to Schottky gates, displaying enhanced channel depletion from the P-N junction. Fabricated devices show high Imax (590 mA/mm) and ION/IOFF of 3x10^7. Devices exhibited state-of-the-art VBR > 2.5 kV with 11.2 m{\Omega}-cm^2 specific on-resistance (LGD = 9.55 um, average breakdown field > 2.5 MV/cm), while shorter gate-drain devices showed high breakdown fields up to 5.3 MV/cm with 0.28 m{\Omega}-cm^2 specific on-resistance. These results showcase sputtered p-Cr2O3 as a viable, low thermal budget P-N junction gate technology for high-Al-composition AlGaN transistors in RF and power electronics.
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All authors Jonathan Pratt, Yizheng Liu, Ijaas Mohamed, Seungheon Shin, Akilesh Srikanth, Md Saklain Morshed, Brianna A. Klein, Andrew Armstrong, Andrew A. Allerman, Sriram Krishnamoorthy, Siddharth Rajan

Materials Science

Crystal symmetry predicts unconventional magnetism

Unconventional compensated magnets combine zero net magnetization with momentum-dependent spin polarization, but identifying them usually requires knowledge of their magnetic order. Here we show that crystal symmetry can constrain unconventional magnetic character before the magnetic ground state is known. Starting from a non-magnetic crystal structure and a specified magnetic sublattice, we generate symmetry-compatible compensated orders and classify their spin textures using spin-space-group symmetry. We identify materials whose generated candidates are all unconventional, either across a defined search space or after restricting the magnetic-cell size. Within the experimental benchmark, 68% of the prioritized materials are unconventional, compared with 9% of the remaining materials. Screening the Materials Project yields thousands of promising candidates for unconventional compensated magnetism. First-principles calculations for $\mathrm{VGe_3}$ and tetragonal $\mathrm{Fe_2SiO_4}$ connect these symmetry predictions to the energetics and spin textures of competing magnetic orders. In $\mathrm{VGe_3}$, a noncoplanar candidate permits mixed-wave spin polarization along a fixed axis without spin-orbit coupling, combining components that are odd and even under momentum reversal. This framework enables crystallography-guided searches for unconventional compensated magnets without first determining their magnetic ground states.
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All authors Ziyin Song, Zhong Fang, Chen Fang, Hongming Weng

High Energy Physics (Theory)

Infrared Screening of the Cosmological Constant

The observed cosmological constant is set by the deepest infrared scale of the present universe rather than by the microscopic scales that contribute to the vacuum energy. We show that this emerges as the quantum fluctuations of the gravitational field are progressively taken into account. Considering the Einstein-Hilbert+$R^2$ truncation of gravity, we find that in a wide region of the parameter space the theory develops instabilities that give rise to large amplitude quantum fluctuations which govern the renormalization group flow. Once the flow enters this region, it remains there all the way towards the infrared and progressively loses memory of its boundary conditions. The running cosmological constant $\Lambda_k$ ($k$ is the running scale) is driven towards the universal infrared scaling $\Lambda_k\sim \lambda_{_{\rm IR}}\,k^2$, with $\lambda_{_{\rm IR}}= \frac{1}{2(\pi-2)}$. At the deepest infrared scale $k_{_{\rm IR}}\sim H_0$ (the current Hubble scale), the cosmological constant is then screened to its observed value $\Lambda_{_{\rm IR}}\sim H_0^2$.
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Materials Science

Atom-Resolved Machine Learning of Dielectric and Piezoelectric Response

Predicting dielectric and piezoelectric responses in structurally complex materials requires large simulation cells, for which density-functional perturbation theory (DFPT) calculations scale as $\mathcal{O}(N^4)$ and become computationally prohibitive. However, machine-learning approaches have remained challenging, limited either by the large amounts of expensive DFPT data required for direct regression or by the cubic cost of reconstruction. We here propose a machine-learning framework that learns the ionic response as an atom-indexed field: DART (Direct Atom-Resolved response-Tensor learning) learns these fields directly and achieves high accuracy from small training sets, whereas LARS (Linear-scaling Atom-Resolved Response Solver) reconstructs them from learned microscopic ingredients through sparse linear solves and requires no DFPT labels for the ionic dielectric or piezoelectric tensors. Using DART, we extrapolate to 314 stackings of AlN/ScN superlattices absent from training and identify a high-response polar candidate, for which DFPT gives a laterally clamped piezoelectric strain coefficient $d_{33,f}=14.511$ pC/N and $k_t^2=20.46\%$, exceeding the ordered 1AlN/1ScN reference by 63% and 66%.
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All authors Jinyu Liu, Yingwei Chen, Liyang Ma, Hongyu Yu, Hongjun Xiang

Medical Physics · Cross-listed from q-bio.PE

Mathematical Modelling of Within-Host HIV Dynamics with Cytotoxic Immune Response and Antiretroviral Therapy

We develop and analyse a mechanistic ODE model of within-host HIV dynamics that includes uninfected CD4$^+$ T cells, latently and productively infected cells, free virions, and cytotoxic immune effectors. Antiretroviral therapy is described by two time-dependent efficacy functions that separately reduce new infections and virion production. We show that solutions remain non-negative and bounded, identify the infection-free and endemic equilibria, and derive the basic reproduction number together with the local stability condition for the infection-free state. We also obtain treatment-dependent suppression thresholds and an analytical estimate of when this threshold is crossed as treatment efficacy declines. Numerical simulations consider untreated infection, ART initiation, periodic variation in efficacy, and progressive loss of treatment effect. Without therapy, the model approaches a state of persistent infection. ART reduces viral load and promotes recovery of the CD4$^+$ T-cell population, while the latent reservoir persists under the parameter set considered. Periodic changes in treatment efficacy produce sustained forced oscillations. These results connect the analytical threshold conditions with the treatment-dependent dynamics of the model and provide a basis for future calibration, sensitivity analysis, uncertainty quantification, and extensions informed by clinical data.
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Materials Science

Subnanometer thermodynamic overlayers on bimetallic nanoparticles

Nanoparticle properties are governed by their surfaces, yet their atomic-scale surface structures remain challenging to predict. Here, we report that bimetallic nanoparticles can form a thermodynamically controlled "shell-dimer" architecture in which one metal forms an overlayer only a few atomic layers thick on another. Using Au-Rh as a model system, atomic-resolution imaging and molecular dynamics show that an ultrathin Au overlayer forms on Rh, stabilized by competition among surface, interfacial, and strain energies. Anisotropic strain limits its growth to the subnanometer scale, and changes in surface chemistry can destabilize the overlayer altogether. Across a range of bimetallic nanoparticles, we found that overlayer formation is associated with elemental immiscibility and lattice mismatch. These findings provide a basis for understanding and controlling surface structures in multimetallic nanoparticles.
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All authors Caitlin A. McCandler, Xianzhuo Lao, Jie Liu, Huipu Liu, Kristin A. Persson, Peng-Cheng Chen

Nuclear Experiment

Quarkonium production in light-ion collisions with the ALICE experiment

Quarkonium production has long been considered as one of the golden probes to study the quark-gluon plasma (QGP). In fact, the early production of heavy quarks (ccbar) and (bbbar) makes quarkonia an ideal tool to investigate the evolution of the hot and dense medium produced in ultra-relativistic heavy-ion collisions. In such a medium, quarkonium production is expected to be suppressed due to the screening of the binding potential between the heavy quark and antiquark and/or through in-medium interactions. Moreover, at LHC energies the recombination of uncorrelated charm quarks pairs, namely regeneration, was found to significantly affect charmonium observables, in contraposition to the suppression mechanism. In addition, measurements in smaller collision systems as p-Pb have highlighted the possibility to observe QGP-like effects. In this context, the study of charmonium production in intermediate collision systems, as light-ion collisions, becomes more and more interesting, representing an ideal test ground for the state-of-the art theoretical models. In this contribution the new measurements of charmonium production will be shown using the light-ion collisions data collected for the first time at the LHC in 2025 (oxygen-oxygen (OO), proton-oxygen (pO)). The results will be shown exploiting the forward ALICE rapidity coverage (2.5 < y < 4). Finally, the measurements will be compared with the existing theoretical models.
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Nuclear Theory

Rapid Uncertainty Quantification on a Latent Field using Fisher Information

Many inverse problems in physics infer an unobserved field from measurements connected to it through a governing equation. We combine Fisher information with a differentiable solver to quantify uncertainty in both the inferred field and its predicted observables, using a local Gaussian approximation without sampling the full parameter posterior. Applied to nuclear optical potentials, the method distinguishes features constrained by scattering measurements from those whose uncertainty remains set by the prior. Our flexible model improves agreement with held-out cross sections and achieves nearly nominal coverage with narrower predictive intervals than an established Bayesian optical model.
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All authors Karl Daningburg, A. E. Lovell, Arvind T. Mohan, R. O'Shaughnessy

Astrophysics of Galaxies

PAHSPECS: JWST/MIRI Spectroscopy of PAHs at Cosmic Noon

The physical conditions of the interstellar medium (ISM) are thought to differ greatly at high redshifts compared to local galaxies. Polycyclic aromatic hydrocarbons (PAHs) are key ISM constituents, mediating the heating and cooling of gas in photo-dissociation regions. However, PAHs are unexplored in main-sequence (MS) galaxies at z~1-2 (cosmic noon), limiting our view of the ISM's thermal and chemical balance. We present the PAH Spectroscopic Survey (PAHSPECS) JWST program, the first MIRI/MRS survey of the 3.3, 6.2, 7.7, 8.6 and 11.3$\mu$m PAH features in MS galaxies at z~1. The five targets come from the deep ALMA CO and continuum flux-limited sample in the HUDF. We detect the 6.2, 7.7 and 11.3$\mu$m PAHs in all galaxies, and the 3.3$\mu$m feature in only two. Spectral energy distribution (SED) fitting to broad-band mid-IR photometry recovers the 6.2 and 7.7$\mu$m PAH luminosities derived from spectral decomposition of the MRS spectra to within ~25% accuracy. However, the 3.3 and 11.3$\mu$m features are overestimated by ~50% (up to 3-5x). Spatially resolved maps of ASPECS-6, the most extended source, show variations of the 7.7$\mu$m PAH contribution to the MIRI F1500W flux, suggesting that while photometry can infer PAH luminosity accurately, IFU spectroscopy is necessary to study variations in PAH ratios and characterize galaxy dust properties. The PAH fraction of the total dust mass from photometric SED modeling roughly agrees with the $L_{\rm PAH}/L_{\rm IR}$ ratio measured from spectroscopy, but the correlation is not as tight as models predict. On average, PAHSPECS galaxies show an excess in 6.2$\mu$m equivalent width relative to nearby dusty luminous systems, but lower 3.3$\mu$m equivalent widths than local systems, similar to higher-mass starbursts at z~1-3. This points to differential changes in the size distributions of neutral and ionized PAHs in cosmic noon galaxies.
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All authors Irene Shivaei, Tanio Díaz Santos, Leindert A. Boogaard, Karin Sandstrom, Cristina Lofaro, Fergus R. Donnan, Pablo G. Pérez González, Roman Fernández Aránda, Javier Álvarez Márquez, Manuel Aravena, Roberto Decarli, Frédéric Galliano, Hanae Inami, Göran Östlin, Gergö Popping, Fabian Walter, Paul van der Wer

Quantum Physics

All you need is the universal correlation detector: A unified approach to universalize communication protocols over quantum channels

Constructing optimal quantum information protocols without complete knowledge of the underlying states or channels is a central challenge. We address this challenge by developing universal correlation detection as a common building block for quantum communication. Our detectors distinguish a bipartite state from the product of its marginals and attain the same first-order asymptotic performance as optimal tests constructed with complete state information. For general bipartite quantum states, knowledge of a single marginal suffices: a detector depending only on that marginal is first-order optimal for every compatible state. For classical-quantum states, the detector is fully universal and requires no prior state information. By combining these detectors with position-based decoding and convex splitting, we construct channel-independent coding schemes that achieve capacity for a range of communication tasks. These results turn universal correlation detection into a systematic tool for universal protocol design, providing a unified route to designing capacity-achieving protocols for many communication tasks over unknown quantum channels.
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Fluid Dynamics

Thermal behaviour of settling heavy inertial particles in turbulent natural convection

We investigate the dynamical and thermal behaviour of settling heavy inertial particles in bulk turbulent thermal convection. Direct numerical simulations are performed in a homogeneous Rayleigh-Benard convection setup, where a uniform mean temperature gradient drives statistically homogeneous convective turbulence seeded with passive inertial particles. We quantify the effects of dynamic and thermal inertia on particle statistics. In particular, we investigate how the fluctuations of particle velocity and temperature can be traced back to the correlations between particle and fluid variables, and how particle temperature statistics is affected by the interplay of settling and preferential concentration.
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All authors Hamid Reza Zandi Pour, Guido Boffetta, Stefano Musacchio, Filippo De Lillo

General Relativity and Quantum Cosmology

The Weyl double copy for relativistic Rindler fluids

We study the Petrov classification and Weyl double copy of the four-dimensional bulk metric dual to a $2+1$-dimensional relativistic Rindler fluid at first order in the relativistic gradient expansion. Upon imposing the fluid equations, the leading Weyl curvature is determined by the fluid vorticity and shear. At this order, the bulk geometry is generically of Petrov type II, with a type D branch for shear-free flows with nonzero vorticity and a type N branch for irrotational flows with nonzero shear. For the type D branch, we construct a purely magnetic Maxwell single copy on a fixed Rindler background and distinguish exact source-free solutions with a constant magnetic field from local perturbative solutions valid through first order in gradients. For the type N branch, we obtain a family of algebraic Weyl double copies parametrized by $\beta$. We derive explicit field strengths and gauge potentials for $\beta=0$ and $\beta=1$, together with the local Cauchy-Riemann conditions imposed by Maxwell's equations. These choices encode the fluid shear differently: for $\beta=0$, the shear dependence resides entirely in the zeroth-copy scalar, whereas for $\beta=1$, it enters the Maxwell field directly. Finally, using the non-relativistic hydrodynamic expansion with explicit $\epsilon$ counting, we derive the non-relativistic limits of the type D single copy and both type N choices, and compare the resulting structures with existing non-relativistic constructions.
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High Energy Physics (Theory)

Six-point consistency and uniqueness of the Veneziano amplitude

We establish uniqueness of the Veneziano four-point amplitude in a meromorphic class by combining six-point consistency with a known low-order supersymmetry relation. We consider planar tree-level scattering in four dimensions with a massless maximally supersymmetric vector multiplet and an additional scalar parity condition. A difference of supersymmetry Ward identities isolates massless factorization residues and eliminates every permitted contribution regular in a common kinematic limit. The resulting functional equation holds at every derivative order and fixes all angular dependence from the forward function after subtraction of the massless poles, at fixed Yang-Mills coupling. For a jointly meromorphic amplitude with simple planar poles, a nonempty spectrum of positive mass-squared poles separated from zero by a mass gap, nonnegative coefficients in the partial-wave expansions of scalar residues, and an exact unsubtracted forward dispersion relation, only the pole positions remain free. Positivity bounds their separation. The low-order relation saturates a sharp spectral inequality, requiring an infinite sequence of equally spaced mass-squared poles. The coupling and first massive pole position therefore determine the complete four-point function and all residues, without an initial finite-spin restriction.
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Quantum Physics

Computational Cryptography from Pseudoentanglement

The advent of pseudoentanglement and computational entanglement theory bootstrapped a wave of research at the intersection of computer science and information theory. In parallel, computational cryptography has undergone substantial development, prompted by the introduction of pseudorandom states and followed by the establishment of a baseline for the computational hardness required for quantum cryptography, from which EFI pairs emerge as a central primitive. We study the connection between pseudoentanglement and computational cryptography through EFI pairs. Our goal is to enable the use of resources arising from computational entanglement theory in the field of cryptography. For this, we establish the relation between operational instances of pseudoentanglement and the hierarchy of minimal assumptions for computational cryptography. We show that the existence of pseudoentanglement under two different operational definitions, with efficient state generation, is a sufficient condition for the existence of EFI pairs. Combined with a previously established result that the converse also holds under the second definition, this allows us to also demonstrate their equivalence. This places pseudoentanglement alongside other minimal assumptions in cryptography, not only offering an alternative perspective on this fundamental problem, but also building a bridge that allows insights from either area to inform the other. While proving these theorems, we introduce and demonstrate technical lemmas in quantum information and computational entanglement theory, relating the computational entanglement measures to the distance between states, establishing distinguishing conditions for mixtures of two families given pairwise distances between their states, and demonstrating the first continuity relation for a computational entanglement measure.
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All authors Ilia Ryzov, Manuel Goulão, Faedi Loulidi, David Elkouss

Instrumentation and Detectors · Cross-listed from cs.RO

High-Voltage Optocoupler Amplifier for Electrostatic Actuators

Many electrostatic actuators require multi-kilovolt drive voltages at sub-milliamp currents, a task poorly suited for conventional switching devices. As an alternative, we demonstrate a high-voltage amplifier using optocouplers as active elements. The amplifier produces a 20-kV peak-to-peak output with up to 500 Hz bandwidth while maintaining a minimal component count. By using optocouplers as linear devices in feedback, lower harmonic distortion and higher bandwidth are achieved than offered by equivalent PWM amplifiers. This design improves the viability of electrostatic actuators by providing a simpler method to achieve useful drive waveforms.
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High Energy Physics (Phenomenology)

Plasma Effects Suppress Mixing-Induced Collisional Freeze-In

Dark matter that is weakly mixed with particles in a thermal plasma can be produced through both, oscillatory and collisional freeze-in. While plasma effects have long been known to suppress the former, their role in collisional freeze-in remains less clear quantitatively, leading to conflicting results in sterile neutrino dark matter production via collisional freeze-in. Using first-principles nonequilibrium Kadanoff-Baym equations in the flavour-covariant formulation, we establish the general result that plasma effects also suppress collisional freeze-in: the vacuum mixing angle in the collision rate is replaced by its plasma-corrected counterpart. Applying this result, we conclude that sterile neutrinos cannot be dark matter in the keV-MeV mass range when produced from the Standard Model plasma.
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High Energy Physics (Phenomenology)

Mass spectrum and decay widths of charmonium-like mesons: A diabatic approach with complex scaling

In this work, we extend our previous diabatic framework for the charmonium-like spectrum below $4.3$ GeV by introducing the complex scaling method. Unlike the previous framework, the present approach explicitly incorporates couplings to the meson-meson continuum, comprehensively accounting for its contributions to the physical states. Consequently, it allows bound and resonant states to be treated on an equal footing, enabling the direct extraction of decay widths from complex energy eigenvalues without introducing any additional free parameters. Using the obtained solutions, we calculate the channel weights and complex root-mean-square radii ($r_{\scriptscriptstyle{RMS}}$ ) to elucidate their internal structures. Specifically, we find that the $\chi_{c1}(3872)$, $\psi(4040)$, and $\psi(4230)$ states exhibit significant molecular characteristics. Furthermore, we propose the $X(3940)$ as a candidate for a $J^{PC}=1^{++}$ state and discuss the nature of the $\chi_{c0}(2P)$ resonance in detail.
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General Relativity and Quantum Cosmology

Periastron advance from the perturbed Binet equation

We apply the Poincaré-Lindstedt method to the perturbed Binet equation describing conservative dynamics of the perturbed Kepler problem. We show that a simple treatment of divergent terms directly determines the frequency shift of the radial motion and hence the periastron advance. We provide explicit expressions for polynomial, logarithmic and inverse power perturbations, extend the procedure to higher perturbative orders and to problems involving several perturbation parameters. Applying this method to different physical effects relevant to compact binaries, we recover known results. We also obtain new contributions to the periastron advance, including the leading-order effects of arbitrary mass- and current-type tidal multipoles and mass-type spin-induced multipoles, the NNLO current-type tidal quadrupole contribution, electromagnetic electric-dipole contributions to NNLO and the eccentric corrections to the electric charge. Finally, we illustrate how the method can be directly applied to the problem of particle motion in Reissner-Nordström, de Sitter-Schwarzschild metrics and in a Yukawa potential.
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Soft Condensed Matter

Extracting hydrogel properties by watching hydrogel particles moving through solid ice

Strikingly, when hydrogel particles are embedded in ice in a temperature gradient, they move through the solid ice towards warmer temperatures, while swelling as they warm up. This motion comes from a flow of unfrozen water through the hydrogel mesh, driven by a process known as `cryosuction'. Here, we show how one can use this behavior to measure – with extremely high resolution – a range of different hydrogel transport properties, and how these change as a hydrogel deswells. These properties include permeability, compressibility, and poroelastic diffusivity: all of which are challenging to measure, but widely important for phenomena involving swelling, dehydration, transpiration and filtration. We demonstrate the measurement technique using poly(ethylene glycol) diacrylate (PEGDA) hydrogels. The technique uses picoliter-scale hydrogel volumes, and yields measurements of hydrogel properties that are consistent with existing literature data. The high resolution of our measurements also allows us to test commonly-used, classical predictions for hydrogel properties (derived assuming an idealized, homogeneous polymer network in the hydrogel). We show that these classical predictions do not work well, highlighting the need for new models that can accurately describe real hydrogels.
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All authors Yanxia Feng, Se-Hyeong Jung, Camillo Sirvinski, Dan Balkanyi, Federico Paratore, Lucio Isa, Robert W. Style

Lattice Field Theory

Accurate Sampling from Diffusion Models

A new proposal called DM-SMC (Diffusion Model - Sequential Monte Carlo) is investigated, which samples ensembles defined in terms of an action, using diffusion models trained on samples from the ensemble. The SMC setup allows for accurate sampling in spite of an approximate diffusion model and the finite stepsize used in the numerical solution of the stochastic process. Improved update strategies are also investigated. Results are presented for a $Z_2$ symmetric scalar field theory in 2 dimensions near its 2nd order phase transition.
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Pattern Formation and Solitons

Degenerate Turing bifurcation and the birth of localised patterns in activator-inhibitor systems

Precise conditions are provided for the existence and criticality of Turing bifurcations in a general class of activator-inhibitor reaction-diffusion equations on a one-dimensional infinite domain. The class includes generalised Schnakenberg and Brusselator models, as well as other models with cubic autocatalytic nonlinear terms. Previous numerical work suggests the existence of a bifurcation structure containing localised patterns due to the so-called homoclinic snaking mechanism. This paper provides explicit calculations to justify those results. Two distinct scalings of parameters that lead to tractable normal-form coefficients are considered in the limit that the diffusion ratio $\delta \to 0$. First, under a small-parameter scaling, the Turing bifurcation is shown to be always subcritical. Second, a large-parameter scaling reveals the Turing bifurcation to be supercritical, leading, by continuity, to the existence of a codimension-two degenerate bifurcation. The sign of a 5th-order normal form coefficient is also computed, which is shown to have the correct sign for the local birth of homoclinic snaking. For the case of the Brusselator, two such codimension-two points can be found explicitly, as can the leading-order expression for the Maxwell point, in a parameter wedge about which localised patterns emerge. Numerical results are found to be consistent with the theory.
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Materials Science

Local order in natural sanidine disentangled via single crystal diffuse scattering

Natural sanidine commonly preserves metastable chemical disorder at ambient conditions, but the local structural correlations associated with this disorder remain poorly understood due to a reliance on average-structure analysis alone. Here, we investigate single-crystal diffuse scattering in a natural sanidine from Drachenfels, Germany, with consistent observations across additional samples from Laacher See, Germany, and Vesuvio, Italy. The diffraction data reveal pronounced anisotropic diffuse features, including characteristic bowtie-like intensity distributions in reciprocal space. To resolve the origin of these features, we combine three-dimensional difference pair distribution function (3D-$\Delta$PDF) analysis with force-field calculations and Monte Carlo modelling. The 3D-$\Delta$PDF shows correlated deviations from the average structure and indicates a strong coupling between occupational and displacive disorder. Force-field calculations demonstrate that the aluminosilicate framework responds strongly to the local alkali occupancy, with the largest structural variation occurring along the $a$ direction. Guided by these observations, we construct a disorder model in which K/Na occupational short-range order is combined with chemically constrained Al/Si distributions and local framework relaxations. The model reproduces the main experimental diffuse-scattering features and shows that the bowtie-like diffuse scattering arises from correlated framework distortions driven primarily by local K/Na order.
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Superconductivity

Bounds on Bose-Einstein Condensation of Higgs modes in a Superconductor

Collective modes in a superconductor correspond to fluctuations in the amplitude (Higgs mode) or the phase (Goldstone mode) of the order parameter. Starting from the BCS Hamiltonian, we derive a microscopic Hamiltonian for the coupled Higgs-Goldstone-electron system that contains all interactions among these degrees of freedom. The Higgs subsystem is a weakly interacting Bose gas: Higgs modes experience a mutual attraction mediated by the virtual exchange of Bogoliubov quasi-particle pairs. They also interact with external electromagnetic-fields with a coupling constant that we derive explicitly. We use this theory to examine whether an optically pumped gas of Higgs modes can undergo Bose-Einstein condensation. We identify a density window, bounded below by the equilibrium condensation criterion and above by collapse due to the attractive interaction, in which condensation can occur and we derive the expected density of Higgs-modes due to external pumping. This pumping depends crucially on non-parabolic corrections to the electron dispersion around the Fermi-energy. We show that the pumped mode density is compatible with condensation for realistic material parameters. We suggest possible experimental signatures of this non-equilibrium condensate.
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General Relativity and Quantum Cosmology

Classical soft theorems meet the post-Newtonian expansion

Classical soft theorems govern the non-analytic structure of electromagnetic and gravitational radiation in the low-frequency regime, with the gravitational memory effect providing the canonical realization of the classical soft graviton theorem. While the soft behavior of radiation from hyperbolic scattering is well understood, its realization in gravitationally bound systems remains less explored. In this work, we study the soft structure of gravitational waveforms generated by compact binaries, focusing on the scattering of emitted radiation off the static background curvature within the multipolar post-Newtonian framework. We isolate the infrared (IR) logarithms associated with hereditary effects, including the tail-of-memory, and their higher generalizations with n-tail insertions. The resulting amplitudes exhibit a Laurent expansion in frequency space consistent with the Sahoo-Sen logarithmic soft theorems, thereby establishing a direct correspondence between gravitational memory effects, their higher-order tail corrections, and the soft expansion. We also comment on ultraviolet (UV) logarithms arising from short-distance sensitivity of the multipole expansion and their associated renormalization-group running.
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Mathematical Physics · Cross-listed from math.AP

Long Time Behaviour of the Two-Component Becker-Döring System

The classical Becker-Döring equations describe the formation of clusters by aggregation and fragmentation of monomers. If the total amount of mass is supercritical, larger and larger clusters are formed, leading to an asymptotic loss of mass in the long time limit. The two-component Becker-Döring system arises when clusters are built from two types of monomers. Here, we study the natural extension of the one-component system, where no energy or entropy is leaving or entering the system - the so called detailed balance assumption. We rigorously prove that all initial conditions admit a solution minimising the relative entropy as time approaches infinity. This shows, that the long time limit in the weak* topology is selected through the initial Type I and Type II masses. Furthermore, the proportion of lost Type I mass is determined by the limit point via the mixing ratio of Type I and Type II monomers that maximises the binding energy. The main difficulty of the two-component system is that no relative entropy is weak* continuous, which is crucial for the classical argument [2]. Instead, our proof is based on a discrete two-dimensional logarithmic Sobolev inequality, that bounds the entropy dissipation on the correct timescale. Our approach also improves current assumptions to determine the long time behaviour for the one-component system.
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Quantum Physics

Syndrome measurements enable deterministic fault-tolerant $T$ gates

Non-Clifford gates are essential for universal quantum computation, yet implementing them fault-tolerantly remains a central challenge for stabilizer codes. Here, we show how a syndrome degree of freedom can mediate a logical non-Clifford gate. Releasing one stabilizer check makes an additional logical qubit available within the encoded data block. Two Pauli rotations, followed by syndrome measurement and Clifford feed-forward, then implement a deterministic logical $T$ gate on every stabilizer code of distance at least two, in a suitable logical basis. During the ideal rotations, the state remains in an intermediate stabilizer code whose distance we determine exactly. For pure codes with a balanced factorization, this distance grows with the original code distance, whereas the maximum weight of the stabilizer generators bounds the intermediate distance from above. We realize the mechanism in two circuits that tolerate a single fault under local stochastic circuit noise: a fixed 22-qubit construction admitting recursive error suppression and a direct Golay-code gate protected by measuring a stabilizer check transported through the non-Clifford rotation, which can recover the unknown encoded state even after rejection. Serial implementations with ancilla reuse, reset, and flexible two-qubit connectivity require at most 33 and 32 physical qubits, respectively. These results establish a general mechanism for logical non-Clifford gates and demonstrate how syndrome measurements and recovery can protect the intermediate evolution of encoded information.
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High Energy Physics (Phenomenology)

Centrality-dependent nuclear modification from hard-soft correlations in the glasma

We present first predictions from the saturation-physics-based framework IP-Glasma for the nuclear modification factor $R_{AB}$ as a function of centrality in $p$ + O, $p$ + Pb, O + O, and Pb + Pb collisions due only to initial-state effects. The same framework is responsible for both soft ($p_T \lesssim 3 ~\mathrm{GeV}$) and semi-hard ($5 ~\mathrm{GeV} \lesssim p_T \lesssim 20 ~\mathrm{GeV}$) particle production, enabling the study of initial-state correlations between bulk and intermediate-$p_T$ particle production from a first-principles framework. We show that, tuned only to HERA data, IP-Glasma accurately predicts the self-normalized multiplicity distributions in $p$ + O, $p$ + Pb, O + O, and Pb + Pb collisions; the minimum-bias nuclear modification factor in $p$ + O and $p$ + Pb collisions; the centrality-cut nuclear modification factor in $p$ + Pb collisions; and the anomalous suppression of $R_{AA}$ observed in very peripheral Pb + Pb collisions. We find that IP-Glasma predicts significantly less suppression than is measured in both $\sqrt{s_{NN}} = 5.36 ~\mathrm{TeV}$ O + O and $\sqrt{s_{NN}} = 5.02 ~\mathrm{TeV}$ Pb + Pb collisions at the Large Hadron Collider, in qualitative agreement with the scenario in which $R_{AA} < 1$ is due to final-state energy loss. We show that the inelastic nucleon-nucleon cross section ($\sigma_{\text{inel}}^{NN}$) produced by IP-Glasma is extremely sensitive to the area of the subnucleonic hotspots; the same values of the hotspot area that reproduce the measured $\sigma_{\text{inel}}^{NN}$ also reproduce minimum-bias $R_{pA}$. Finally, we show that the hard-soft correlations in IP-Glasma arise from event-by-event fluctuations in the color fields, which simultaneously drive enhanced production of both soft and hard particles.
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Quantum Physics

The regularized channel Rényi divergence is continuous

We show that the regularized channel Rényi divergence is continuous at $\alpha = 1$. As consequences, we establish an exponentially strong converse for channel discrimination, a subchannel-smoothed asymptotic equipartition property, a relative entropy accumulation theorem, and a new proof of the generalized quantum Stein's lemma. Our result further shows that the regularized channel relative entropy is computable. The continuity proof relies on a variational formula that expresses the regularized channel divergence as a single-letter optimization over variables of unrestricted finite dimension. We then establish continuity using a novel spectral confinement technique.
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Quantum Physics

Efficient Synthesis of Multi-Controlled Toffoli Gates with Ternary Clifford$+P_9$ Gates

Temporary occupation of qutrit levels can reduce the width and depth required for binary circuit logic in quantum computing. We introduce an efficient intermediate-qutrit decomposition of multi-controlled Toffoli gates with binary-subspace inputs and outputs. For balanced control widths $n=2^h-1$, the proposed decomposition is evaluated hierarchically through a tree, allowing independent subtree computations to proceed in parallel and reducing the depth from linear to logarithmic. The balanced low-depth construction requires $6n+3$ logical $P_9$ injections and $\frac{n-3}{4}$ clean ancillary qutrits. It matches the direct $P_9$ count of a recursively extended Clifford+$P_9$ baseline derived from the state-of-the-art work while using asymptotically one-quarter as many clean ancillas and replacing linear depth with logarithmic depth. For arbitrary control widths, a sequential extension preserves the $6n+3$ $P_9$ count but has depth $O(\log m+n-m)$ for a balanced core $m=2^h-1\leq n$, which is linear in the worst case over $n$. By reducing the resource overhead of a widely used reversible primitive, the proposed decomposition provides a practical building block for the design and compilation of more resource-efficient quantum algorithms in the fault-tolerant regime.
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High Energy Astrophysical Phenomena

Exceptional Gamma-Ray Flaring Activity of the Blazar S4 0954+65 in Early 2025

S4 0954+65 (4FGL J0958.7+6534) is a TeV-detected blazar at a redshift of $z = 0.3694 \pm 0.0011$, classified as an intermediate-synchrotron-peaked BL Lac object. In early 2025, it entered an exceptional $\gamma$-ray high state. We aim to investigate the origin and physical properties of the exceptional 2025 flare, and to constrain the emission processes responsible for this flaring activity. We performed a multi-wavelength analysis using $\gamma$-ray, X-ray, optical/UV, radio, and 43 GHz Very Long Baseline Array (VLBA) observations. We examined multi-band correlations with the z-transformed discrete correlation function (zDCF), analyzed the spectral evolution and parsec-scale jet kinematics, and modeled the broadband spectral energy distributions (SEDs). The $\gamma$-ray variations lead the optical and radio emission by 3.22 days and possibly 18.26 days, respectively, while no significant correlation is found between the $\gamma$-ray and X-ray emission. The $\gamma$-ray spectra show a harder-when-brighter behavior, consistent with enhanced particle acceleration during the active state. A similar spectral trend is also observed in the X-ray band, where the photon index is anti-correlated with flux. During the major $\gamma$-ray flare, VLBA images reveal the emergence of a new superluminal radio knot from the core, whose extrapolated ejection time is consistent with the peak of the $\gamma$-ray flare. The temporal and structural evolution during the 2025 flare is consistent with a shock-in-jet scenario, in which a newly emerging disturbance propagates downstream and drives the flare. Broadband SED modeling shows that a leptonic synchrotron self-Compton plus external Compton model with dusty torus seed photons reproduces the multi-wavelength observations with physically plausible parameters. A lepto-hadronic interpretation remains possible but requires substantially higher jet power.
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All authors Zhihao Ouyang, Jingyu Wu, Hubing Xiao, Lili Yang, Shangchun Xie, Shaohua Zhang, Zhijian Luo, Jianzhen Chen, Jianguo Wang, Mingjun Liu, Qinyu Wu, Huaqing Cheng, Wenda Zhang, Junhui Fan