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Physics

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Sunday 30 August

Computational Physics

A wide-range temperature-dependent deep potential for sodium with near-experimental accuracy from melting to the critical point

G. S. Demyanov, D. V. Minakov, V. B. Fokin et al. (+1 more)

We construct temperature-dependent deep potentials for sodium using finite-temperature DFT data obtained with the PBE, AM05, and $r^2$SCAN exchange-correlation functionals and investigate the thermophysical properties of sodium from room temperature to the critical region. The predicted critical parameters show a dependence on the exchange-correlation functional. The model based on the $r^2$SCAN functional gives a critical temperature $T_c=2.508(8)$ kK, density $\rho_c=0.203(4)$ g/cm$^{3}$, and pressure $P_c=0.249(6)$ kbar, in close agreement with the recommended values. This model is then used to reconstruct the normal-pressure and critical isobars and to calculate the enthalpy, heat capacities, thermal expansion coefficient, bulk moduli, Grüneisen parameter, and speed of sound. The calculated normal-pressure bcc density differs by only 0.06% from the experimental value. Direct solid-liquid coexistence simulations give a melting temperature of $346(2)$ K, 25 K below the recommended value, consistent with the sensitivity expected from meV/atom free-energy errors. Liquid-vapor coexistence simulations reproduce the binodal and yield a surface tension that approaches zero near the critical point. The calculated self-diffusion coefficient and shear viscosity extend the available transport-property data into the expanded-liquid and near-critical regions, where direct experimental information is sparse. We also demonstrate the thermodynamic consistency of the results by comparing the speed of sound obtained from direct acoustic simulations with that calculated from the equation of state.
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All authors G. S. Demyanov, D. V. Minakov, V. B. Fokin, P. R. Levashov

Computational Physics · Cross-listed from math.NA

Wigner-Eckart Factorization of the Polyatomic Boltzmann Collision Operator

Torsten Keßler, Bas W. T. Gieling, René R. Hiemstra et al. (+1 more)

We extend the Wigner-Eckart factorization of the spectral Boltzmann collision operator to polyatomic gases with continuous internal energy. Because internal energies are invariant under spatial rotations, the SO(3) reduction survives the Borgnakke-Larsen energy exchange, and the twelve-dimensional collision integral collapses onto a nine-dimensional kinematic core. The core splits into a sparse geometric tensor, evaluated exactly, and a dense physical tensor, integrated by singularity-resolving Gauss rules with an auxiliary Laplace representation of the fractional energy couplings. The quadrature attains near machine precision at the fractional exponents of real gases. The collision invariants are embedded exactly, preserving the translational-internal energy exchange. The factorization compresses the operator by three to nearly four orders of magnitude and accelerates its evaluation 40-fold over dense formulations. The method is validated against the exact monatomic limit, Landau-Teller relaxation, and an analytic frozen-channel Prandtl number, and it matches a published calibration of the same kernel for N2, CO, and H2.
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All authors Torsten Keßler, Bas W. T. Gieling, René R. Hiemstra, Michael R. A. Abdelmalik

Superconductivity

Interplay of Excitonic Charge Density Wave and Superconductivity in Transition Metal Dichalcogenides

Ayussh Anubhav Patel and Amit Ghosal

Motivated by the unique characteristics of the phase diagram of 1T-TiSe2, we investigated the complex interplay of excitonic charge density wave (CDW) and superconductivity (SC) on a two-dimensional triangular lattice, each site accommodating two orbitals. In response to various tuning parameters, such as intercalation, pressure, substitution, and gating, these materials exhibit a generic and gradual waning of CDW, followed by the emergence of SC. Intriguingly, the nature of CDW changes from commensurate to incommensurate with the appearance of SC. Setting up a minimal model based on observed excitonic CDW and electron and hole pockets in the Fermi surface, and analyzing it within a simple mean-field framework, we can comprehend some salient experimental features. We also found that the qualitative phase diagram remains insensitive to details of the band structure. These results offer crucial insights into the nature of the interplay between CDW and SC in transition-metal dichalcogenides.
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High Energy Physics (Theory)

BMN Spread Complexity Across Phase Transitions

Dibakar Roychowdhury

We investigate the dynamical behavior and spread complexity of quantum states within the mass-deformed BMN matrix model equipped with an emergent $U(1)$ global charge at finite temperature $\beta^{-1}$ and chemical potential $\nu$. Focusing on the strong-coupling regime ($\mu \gg 1$), we model the dynamics via a charged Thermofield Double (cTFD) state and trace the evolution of spread complexity across three distinct thermodynamic regimes. In the low-temperature gapped phase ($\beta \mu \gg 1$), discrete mass-gap bound states dominate, trapping wavepacket dispersion and producing non-chaotic, oscillatory early-time growth. Conversely, in the high-temperature continuum phase ($\beta \mu \ll 1$), thermal excitations overwhelm the mass gap, driving a transition to a continuous advection field that exhibits maximal chaotic scrambling with a Krylov Lyapunov exponent $\lambda_K = \pi / \beta$ that saturates the universal bound. In the intermediate temperature regime ($\beta \mu \sim 1, \beta \nu \sim 1$), the interplay between mass-gap bound states and the continuous thermal background induces a sub-leading correction to the Lanczos coefficients $b_n \sim \frac{\pi}{\beta} n + \gamma \sqrt{n}$, governing a continuous sub-exponential crossover before full chaotic thermalization. Technical derivations regarding KMS boundary conditions, grand canonical spectral moments, residue analysis, and time-reversal symmetry breaking in Krylov space are detailed in four dedicated appendices.
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Quantum Physics

Dark state as a measurable state by a dispersive readout without a Purcell limit

Wei-Chen Chien, Jyh-Yang Wang, Yen-Yu Chiang et al. (+6 more)

It is believed that the enhancement in qubit-resonator coupling allows a better dispersive readout but introduces greater Purcell loss. In this work, we propose that a dark mode in a coupled quantum system may violate this rule by introducing the ZZ interaction between the dark and a bright mode. The dark mode may exhibit an effective zero coupling strength, and zero Purcell loss with the resonator photons. Nevertheless, the dispersive shift is almost the same as the bright state, due to the higher order perturbation introduced by the higher excited states. Such a state demonstrates the measurability without a Purcell limit in circuit quantum electrodynamics.
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All authors Wei-Chen Chien, Jyh-Yang Wang, Yen-Yu Chiang, Cheng-Chengh Huang, Lih-Chieh Hsaio, Yen-Chun Chen, Cen-Shawn Wu, Chiidong Chen, Watson Kuo

Disordered Systems and Neural Networks

Pseudo Entropy in Quantum Spin Chains: from Integrability to Chaos

Tara Bahadur Rana, Yadav Raj Dahal and Kiran Adhikari

In this work, we study pseudo entropy and spectral dynamics in quantum spin chains (Heisenberg XXZ model and the mixed-field Ising model) to investigate whether they can serve as diagnostics of quantum chaos. First, we derive an exact relation between the real part of the thermal pseudo entropy and the spectral form factor. This provided evidence that pseudo entropy could exhibit the characteristic dip, logarithmic ramp, and plateau, implying the precise manner in which pseudo entropy probes chaos. We found that the imaginary part, while it does not diagnose chaos, can still provide crucial information about Fisher zeros that is not available in the real counterpart. For spatial pseudo entropy in the XXZ chain, we find that the logarithmic critical scaling persists in both integrable and chaotic regimes, and that the non-positivity conjecture holds. Finally, we derive an exact connection between pseudo entropy, relative pseudo entropy, and spectral complexity with a potential connection to holography.
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Statistical Mechanics

Branching stochastic mechanics: Clustering and connected correlations within a branching-process representation of the Schrödinger equation

Eric Dumonteil, Benoît Bischoff, Alain Letourneau et al. (+2 more)

Can finite-range correlations hide in the statistics of an extended quantum state? The Schrödinger-Nagasawa transform represents the wave function by positive forward and backward diffusion fields whose product is the Born density. We promote them to branching superprocesses, \(\Phi_F\) and \(\Phi_B\): diffusion samples stochastic paths, whereas Bohm/Fisher-controlled branching generates genealogies of alternative continuations. With rates evaluated on the prescribed Born density, their means reproduce Schrödinger dynamics exactly. The connected sector exhibits supercritical, critical, and subcritical clustering in confinement and has critical dimension \(d_c=2\) in free space. Stationary eigenmodes remain extended; subcritical clusters acquire the reduced de~Broglie scale. We then let the branching rate respond to the fluctuating product \(\Phi_F\Phi_B\). In the reciprocal basis, the fields equal a smooth reference \(R\) plus centered fluctuations \(\psi_F,\psi_B\), defining the signed kernel \(C_{\rm FB}(x,y)=\mathbb E_\omega[\psi_F(x)\psi_B(y)]\). On the anticorrelated branch, \(\rho_{\rm BSM}(x)=-C_{\rm FB}(x,x)\) is the positive organized connected weight. Stationary matching of this weight to the Born profile is imposed as a closure condition, while off-diagonal decay defines the correlation range. The pair equation splits into collective and relative sectors: spectral cancellation selects the Born collective mode, while suppression of the leading density fluctuation selects the anticorrelated source channel. With relative diffusivity \(D_{\rm eff}\) and positive relaxation rate \(\mu_{\rm FB}\), correlations have screening length \(\xi_{\rm FB}=\sqrt{D_{\rm eff}/\mu_{\rm FB}}\). Within this reciprocal closure, an extended Born-shaped connected weight and a finite correlation range can coexist in one stochastic kernel.
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All authors Eric Dumonteil, Benoît Bischoff, Alain Letourneau, Loïc Thulliez, Corentin Doutre

General Relativity and Quantum Cosmology

Two Languages for the Same Resonance: From Nuclear Decay to Black-Hole Ringdown

Okuto Morikawa

Quantum resonances and black-hole quasinormal modes (QNMs) are described by closely related mathematics: radiative boundary conditions, analytic continuation of Green functions or resolvents, poles on nonphysical sheets, and non-self-adjoint spectral representations. This article does not introduce that equivalence but reconstructs its genealogy. Nuclear resonance theory grew from radioactive decay, reaction cross sections, metastable compound states, and complex energies, whereas black-hole perturbation theory grew from spacetime stability and causal response. We place the two developments on a common chronology, from Sommerfeld's radiation condition and early nuclear-decay theory through Regge–Wheeler perturbations, Vishveshwara's 1968 dissertation and 1970 papers, Press's 1971 quasi-normal terminology, and the independent Aguilar–Balslev–Combes theory of analytic dilation, then follow their later mathematical reunification in scattering-resonance theory. Alongside the chronology, we give a working dictionary relating no-incoming and horizon-ingoing/infinity-outgoing conditions, pole energy and complex frequency, width and damping rate, residues and excitation factors, and nonresonant background with branch-cut and prompt contributions. The aim is to make the cross-disciplinary equivalence operational without flattening its history, and to distinguish mathematical equivalence from historical genealogy.
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Chemical Physics

Site-Specific Vibrational Dynamics to Probe Local and Global Protein Motions

Sena Aydin and Markus Meuwly

Vibrational spectroscopic probes can provide site-specific information on protein structure and dynamics. In this work, the possibility to relate protein motion with the vibrational response for –SCN, –N$_3$, and –SNO labels covalently linked to all alanine-residues in lysozyme is investigated. Depending on the position of the probe along the polypeptide chain, its local hydration, and the dynamics of its environment, the vibrational response can encode not only local fluctuations but also low-frequency, collective motions of the protein. The spectroscopic probes are described using machine-learning-based models for both bonded interactions, represented by reproducing-kernel models, and electrostatic interactions, represented by fluctuating minimally distributed charges. Spectroscopic dynamics are characterized through frequency fluctuation correlation functions (FFCFs). For many probe locations, the FFCFs contain a non-decaying component on the simulation time scale, indicating residual slow dynamics and incomplete sampling of the underlying conformational fluctuations. The magnitude of these static contributions is consistent with previous experimental observations, providing qualitative validation of the simulations. Overall, the results demonstrate that site-specific vibrational probes can report on dynamics extending beyond their immediate local environment and can, at suitable locations, provide information on collective protein motions.
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High Energy Physics (Phenomenology)

Seesaw and Axion in No-Scale Gravity

Anamaria Hell, Lincoln da S. Pereira and Tsutomu T. Yanagida

The No-Scale gravity is a compelling framework to describe particle physics, gravity and cosmology, in which all mass scales are an illusion given by the value of a scalar field $\phi$. This theory, however, falls under the umbrella of more general scalar-tensor theories, which propagate different modes depending on the scalar field, and faces the extensive debate regarding the equivalence between its Jordan and Einstein frame descriptions. In this work we advocate that by excluding the singular point in the transformation between the two frames (e.g., $\phi=0$) we can have the classical equivalence between them. To show the merit of removing this singular point, we argue the Jordan frame makes the symmetries of the model manifest, which creates a suitable playground for the particle-physics model building which we illustrate by showing the emergence of discrete symmetries which leads to a high-quality axion and also naturally incorporate the seesaw mechanism.
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Optics

Localization in microcavities revealed by phase-space non-Hermitian skin effect

Jung-Wan Ryu, Yong-Hoon Lee, Muhan Choi et al. (+2 more)

Contrary to the semiclassical expectation for fully chaotic systems, localization of resonances is found to be a common feature in open microcavities. In spiral-shaped dielectric microcavities, a substantial fraction of resonances localize on polygonal patterns in real space, are chiral, and their momentum distributions accumulate near the critical line for total internal reflection. Despite the extensive investigation, the physical mechanism responsible for their remarkable abundance has remained a long-standing question. Addressing this, we reveal a physical correspondence between an inhomogeneous-loss Hatano-Nelson model and the dielectric phase space of a spiral microcavity. We show that the combination of geometry-induced momentum drift and refractive escape yields a generalized non-Hermitian skin effect in the phase space momentum. We identify this mechanism as the origin of the critical-line localization of resonances in open chaotic spiral microcavities, extending the skin-effect concept beyond nonreciprocal lattices to phase space and to open chaotic wave systems.
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All authors Jung-Wan Ryu, Yong-Hoon Lee, Muhan Choi, Chang-Hwan Yi, Martina Hentschel

Strongly Correlated Electrons

Thermal Hall Signatures of Distinct Schwinger-Boson Flux Sectors on the Honeycomb Lattice

Daiki Sasamoto

Thermal transport offers a bulk probe of charge-neutral excitations in frustrated magnets. It remains challenging, however, to determine whether such transport can distinguish different parton mean-field structures of the same spin system. This question is particularly relevant on the honeycomb lattice, where distinct $0$-flux, $\pi$-flux, and chiral $\pi/2$-flux sectors have been proposed. In this paper, we compare self-consistent saddle-point solutions in these three sectors for a frustrated $J_1-J_2$ Heisenberg model with a next-nearest-neighbor Dzyaloshinskii-Moriya interaction and a perpendicular magnetic field. Using finite-temperature Schwinger-boson mean-field theory and the Kubo formula for bosonic Bogoliubov-de Gennes systems, we evaluate the intrinsic spinon thermal Hall conductivity. At a common parameter point where all three branches remain gapped, the $0$-flux response is positive and the $\pi$-flux response is negative for $D>0$ and $h>0$ under the sign conventions used in this paper, whereas the $\pi/2$-flux response changes sign with increasing temperature. We further show that a projective symmetry combining a sixfold rotation with time reversal forces the zero-field response of a fixed chiral $\pi/2$-flux domain to vanish. Within the mean-field regime examined in this paper, the sign and temperature dependence of $\kappa_{xy}/T$ therefore provide a flux-sensitive transport signature.
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Instrumentation and Detectors

A high-speed anamorphic pupil-conjugate slit spectrograph for rapid, self-luminous sources

Matthew Vayner and Kyle D. Gilroy

We present a slit imaging spectrograph whose wavelength registration is a property of the instrument rather than of the pointing of the fore-optic or the position of the source. An internal telecentric 4f relay places the system stop within the instrument while a cylindrical lens places the slit aperture at a plane where transverse position encodes source angle only (an $A = 0$ conjugate in the ABCD matrix formulation). As a result, the lateral motion of the source or the pointing of the fore-optic does not cause the spectral image illuminating the sensor to wander, thus eliminating any non-physical registration of chemical species not present in the event and the need for on-the-fly recalibration. Additionally, the use of a high-speed CMOS camera eliminates temporally averaged spectral lines and aliasing noise. We characterize wavelength calibration (He discharge lamp, quadratic fit, RMS residual 0.12 nm, verified with Ne discharge lamp, same calibration, RMS residual 0.13 nm), spectral resolution (R $\approx$ 639, FWHM 0.92 nm at the optimal slit width setting, R $\approx$ 783, FWHM 0.75 nm at the instrument profile floor), and pointing invariance (He 587.6 nm line wander 0.29 nm RMS, 1.03 nm peak-to-peak, a nearly 100x reduction relative to the same instrument with the aperture stop at the fore-optic pupil). We perform combustion spectroscopy on ignited nitrocellulose at 10 kHz, 99 $\mu$s exposure time, identifying Na, K, Ca, CaOH, and Rb chemical species using the unchanged wavelength calibration transferred from the helium discharge lamp.
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Mesoscale and Nanoscale Physics

Josephson-Phase Reversal of Non-Bloch Andreev Propagation

X. Z. Zhang and Hechen Ren

Non-Hermitian control is difficult in solid-state systems due to fixed dissipation. Here, we show that in a spin-orbit-coupled planar Josephson junction, changing only the Josephson phase reverses the non-Bloch propagation of a low-energy Andreev band and switches its boundary accumulation between junction edges. The phase reshapes the band's spin and electron-hole composition, causing a fixed reservoir to unequally attenuate counterpropagating modes. Weak-loss theory links this phase-controlled loss imbalance to boundary-selected complex momenta, offering an in situ route to reconfigurable non-Hermitian transport in superconducting platforms.
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Materials Science

Valley-Enabled Intrinsic Dresselhaus Spin-Orbit Coupling in Silicon

Johannes L. P. Steinschuld, Hendrik J. Bluhm, Lars R. Schreiber et al. (+1 more)

We develop a symmetry-based theory of spin-orbit-valley coupling in silicon that reveals an intrinsic source of Dresselhaus spin-orbit coupling independent of interfaces or external electric fields. Treating the valley degree of freedom as a symmetry-carrying quantum degree of freedom, we show that the Dresselhaus interaction is necessarily valley off-diagonal and that a bulk contribution proportional to the valley Pauli matrix $\tau_1$ is symmetry allowed. Tight-binding calculations yield a bulk coupling more than an order of magnitude larger than typical interface-induced spin-orbit coupling; achieving the same energy scale through the interface-induced mechanism would require electric fields roughly 50 times larger than typical fields. We further derive the symmetry-allowed spin-valley couplings generated by magnetic-field gradients and show how they account for the valley-dependent Zeeman splitting observed in micromagnet experiments. A slight tilt of the background magnetic field out of the plane produces an additional isotropic contribution linear in $B_z$, providing an experimentally accessible signature of the corresponding coupling constant. Finally, we predict a spin-independent micromagnet-induced valley splitting in the $\tau_3$ channel, which is distinct from the $\tau_{1,2}$ channels generated by alloy disorder and therefore remains robust against disorder-induced cancellation. These results establish valley symmetry as a fundamental ingredient in the spin-orbit physics of silicon and provide new mechanisms for controlling and probing spin and valley degrees of freedom in silicon quantum devices.
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All authors Johannes L. P. Steinschuld, Hendrik J. Bluhm, Lars R. Schreiber, Seyed Akbar Jafari

Earth and Planetary Astrophysics

Probing Triton's Space Environment and Internal Structure: An Integrated Detection-and-Interpretation Framework

Jiansen He, Chuanpeng Hou, Haoen Xie et al. (+10 more)

Triton, Neptune's largest moon, is a prime ocean-world target. Constraining ocean thickness, composition, and conductivity is essential for habitability assessment, but magnetic induction alone cannot resolve the thickness-conductivity degeneracy, and magnetic perturbations from Triton's space currents can obscure the internal induction signal. We present an integrated detection-and-interpretation concept linking four physically consistent calculations. Using `PlanetProfile', we construct a common radial interior structure (temperature, density, conductivity, seismic-wave speed). We then use `MoonMag' to compute the degree-one magnetic-induction response from that conductivity profile at the synodic, rotational, and orbital periods. We perform a multi-fluid `SWMF' simulation with the induced dipole as the inner-boundary condition and develop a Coulomb-gauge Poisson reconstruction to isolate space-current magnetic fields. Finally, we develop the `TritonSeis' workflow, three-dimensional seismic forward modeling plus hierarchical travel-time inversion, to constrain the ice-ocean and ocean-rock interface depths. We find that induction is substantially more sensitive to ocean conductivity than to layer thickness, and that space-current fields are comparable in amplitude to the internal induction signal. A five-station synthetic recovery test resolves both interfaces to first order, with errors of +8.4% for the ice shell and -12.5% for the ocean. Under a conservative noise assumption, the minimum detectable magnitudes are approximately 3.8-4.6 at epicentral distances of 100-1000 km. The Poisson reconstruction and end-to-end seismic recovery are, to our knowledge, the first such quantitative demonstrations for Triton. Coordinated magnetic, plasma, and seismic measurements are complementary and can break the conductivity-thickness degeneracy, providing a framework for future Triton exploration.
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All authors Jiansen He, Chuanpeng Hou, Haoen Xie, Jiaqi Li, Tianhang Chen, Hong Zou, Xuzhi Zhou, Hui Li, Yan Li, Fuchuan Pang, Bingkun Yu, Hui Huang, Tong Wang

Mathematical Physics · Cross-listed from math.QA

Poisson bialgebras by deformations-to-quasiclassical limits

Siyuan Chen and Chengming Bai

Poisson algebras are the quasiclassical limits of associative algebra deformations of commutative associative algebras. This paper extends this process to the level of bialgebras. We derive Poisson bialgebras as the quasiclassical limits of antisymmetric infinitesimal bialgebra deformations of commutative and cocommutative antisymmetric infinitesimal bialgebras. It might be regarded as the “infinitesimal" version of the quantization process of Lie bialgebras in terms of Hopf algebras. Such deformations-quasiclassical limits process for a Poisson bialgebra is equivalently characterized in terms of the introduced notions of deformations of a matched pair of associative algebras as well as a standard Manin triple of associative algebras, whose corresponding quasiclassical limits are a matched pair of Poisson algebras and a standard Manin triple of Poisson algebras, respectively. We illustrate these equivalent deformations-quasiclassical limits processes via coherent derivations.
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Materials Science

Phonon-Localization-Driven Decoupling of Dual-Channel Transport for Record-Low Intrinsic Lattice Thermal Conductivity

Zhunyun Tang, Xiaoxia Wang, Jin Li et al. (+4 more)

A fundamental bottleneck in pushing the intrinsic lattice thermal conductivity of inorganic crystalline solids to its lowest limit arises from the inherent competition between the particle-like propagation (\(\kappa_{\mathrm{L}}^{\mathrm{P}}\)) and wave-like tunneling (\(\kappa_{\mathrm{L}}^{\mathrm{C}}\)) channels. Herein, we demonstrate that phonon localization provides a robust pathway to decouple the dual-channel transport, achieving record-low \(\kappa_{\mathrm{L}}\) in quasi-1D ternary helical crystals. Despite the structural complexity leading to densely populated phonon branches and thus inducing abundant coherent phonons, the weak interchain interactions and heavy elements compress numerous branches into highly localized, nearly dispersionless flat bands. Such strong localization simultaneously suppresses both the diagonal and off-diagonal components of the group velocity, thereby synergistically suppressing \(\kappa_{\mathrm{L}}^{\mathrm{P}}\) and \(\kappa_{\mathrm{L}}^{\mathrm{C}}\). Taking InSeI as an example, the interchain room-temperature \(\kappa_{\mathrm{L}}^{\mathrm{P}}\) and \(\kappa_{\mathrm{L}}^{\mathrm{C}}\) are 0.145 and 0.053 W/mK, respectively, yielding an ultralow total \(\kappa_{\mathrm{L}}\) of 0.198 W/mK. Weaker interchain interactions further drive the room-temperature \(\kappa_{\mathrm{L}}\) of GaSeI and AlSeI to record lows of 0.086 and 0.089 W/mK, respectively; these values even drop to 0.058 and 0.059 W/mK at 900 K. These findings provide useful insights into exploring the thermal conductivity limit in crystals.
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All authors Zhunyun Tang, Xiaoxia Wang, Jin Li, Chaoyu He, Chao Tang, Mingxing Chen, Tao Ouyang

Statistical Mechanics

Representation Transitions Reveal Predictive Structure in Complex Systems: A Trajectory-Level Reconstruction in a Critical System

Jiaqi Pan

Trajectories in complex systems often contain structure that is not captured by the population-averaged, scalar statistics traditionally used to describe them. Here we reconstruct, through independent numerical re-simulation rather than literature review, a systematic search across representational forms - from single scalar statistics, through two independent discrete multi-feature classification attempts, to a trajectory-level structural representation and a diagnostic surrogate test, to a continuous low-dimensional compression - applied to the same underlying trajectory ensemble in a critical complex system. Predictive failure is not explained by insufficient correlation: one discrete representation's own strongest individual feature correlates with the target more strongly ($r=0.588$) than the eventual successful representation's own headline statistic ($r=0.540$), yet fails to separate the ensemble's two most consequential cases - while the continuous representation succeeds, robustly, across eight independent scale-removal folds ($r=0.677$-$0.717$, all $p<0.001$). The determining factor was not correlation strength but whether the representation preserved the structure relevant to prediction. These results indicate that the choice of representation determines whether predictive structure in complex systems becomes accessible - a scientific variable in its own right, not a downstream analysis choice.
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High Energy Physics (Phenomenology)

X(2370) as the pseudoscalar glueball: Another clue from a constituent approach

F. Buisseret

The pseudoscalar state X(2370) is the clearest glueball candidate experimentally identified so far. From a phenomenological point of view, constituent approaches, in which the lightest glueballs are modelled as bound states of two transverse constituent gluons linked by an adjoint flux tube, reach a good agreement with quenched lattice QCD pure gauge spectrum. Based on the assumption that the total decay width of glueballs or light unflavoured mesons is proportional to the energy stored in the flux tube, a model is developed that linearly correlates the hadron decay width to its mass. The model is first fitted on light unflavoured mesons and then extended to glueballs. Both the mass and decay width of the X(2370) are compatible with the results of the constituent approach. Other experimental glueball candidates in the scalar and tensor channels are also reviewed to show the ability of the developed approach to identify glueballs: The f$_2$(2150) and f$_2$(2300) states appear as promising tensor glueball candidates.
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Physics and Society

Peer Review at Capacity: An editor's view

Yamir Moreno

From the editor's desk, the pressure on peer review is no longer an abstract concern. It appears in the growing number of invitations needed to secure an appropriate report, the repeated reliance on a small group of dependable colleagues, and the duplication of work when manuscripts move between journals. The problem is not simply that science has too few potential reviewers. It is that reviewing labor is unevenly distributed, weakly recognized, and organized through a publication architecture built for a smaller system.
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Superconductivity

Magnetic contacts on freestanding superconducting LaAlO$_3$/SrTiO$_3$ micromembranes

Thies Jansen, Pinelopi Konstantinopoulou, Niklas Martin et al. (+5 more)

The superconducting two-dimensional electron gas (2DEG) at the LaAlO$_3$/SrTiO$_3$ (LAO-STO) interface is a promising platform for superconducting spintronics, however, integrating ferromagnetic contacts with the superconducting 2DEG remains challenging. Here, we realize superconducting LAO-STO micromembrane devices contacted by ferromagnetic nickel contacts through a side-contact geometry. Low-temperature transport measurements demonstrate that superconductivity is preserved in the presence of the ferromagnetic contacts. We show that the superconducting state is strongly influenced by the magnetic history of the nickel contacts, which generates a tunable effective magnetic field in the 2DEG. Through an effective field model, the magnetization of the contacts can be inferred from the maximum superconducting response. Our results establish ferromagnetically contacted LAO-STO as a platform for future investigations of spin injection into oxide superconductors and provide a route towards superconducting spintronic devices based on complex oxide interfaces.
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All authors Thies Jansen, Pinelopi Konstantinopoulou, Niklas Martin, Fabio Miletto Granozio, Alessia Sambri, Rasmus Bjørk, Felix Trier, Thomas S. Jespersen

Mesoscale and Nanoscale Physics

Localized orbitals and tunnel couplings from general confinement potentials in gate-defined quantum-dot arrays

Bohdan Khromets, William Chow and Jonathan Baugh

Efficient simulation of dense gate-defined multi-quantum-dot arrays requires accurate and scalable modeling methods, compatible with asymmetries and imperfections of realistic voltage-controlled confinement potentials. We present a numerical localization procedure that rotates the eigenbasis of a general one-particle effective orbital Hamiltonian into $s$-, $p$-, $d$-, $\ldots$-shells of localized orbital wavefunctions associated with individual quantum dots. The pairwise tunnel couplings between such states are computed directly as matrix elements of the Hamiltonian. We demonstrate this procedure on a 2D triangular Si-MOS triple-quantum-dot array by obtaining the voltage dependencies of the tunnel couplings and their distributions in the presence of disorder. We discuss the implications of this evaluation method on the many-body calculations, and relate it to the experimental tunnel coupling measurements.
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Fluid Dynamics

Splashing-regime transitions and secondary-droplet scaling in oblique drop impacts on a deep pool

Ying Xiong, Yang Zhang, Lingling Xie et al. (+1 more)

Oblique drop impact onto a deep liquid pool produces asymmetric crowns, directional jetting, and splashing transitions that cannot be characterized by the total impact inertia alone. We numerically investigate water drops impacting a quiescent deep pool over $41\leq We\leq1790$ and $10^\circ\leq\theta\leq90^\circ$. The simulations reproduce the principal features observed experimentally and identify five post-impact regimes in the $We$–$\theta$ plane: deposition, front splashing, side splashing, side-front splashing, and crown splashing. The deposition–front-splashing transition is described by the tangential-inertial parameter $K_s=We\cos\theta$, with $K_s^c\approx120$. This criterion follows from the competition between downstream crown-rim inertia and capillary retraction at the Taylor–Culick velocity. The transition from front to side-front splashing is instead governed primarily by normal impact inertia, with a critical normal Weber number $We_N^c\approx318$. Beyond these regime transitions, the secondary-droplet statistics reveal fragmentation behavior common to the different splashing regimes. The droplet-size distributions are positively skewed, and the median diameter follows $d_{s,\mathrm{med}}/D\sim We^{-3/5}$. Second-order velocity structure functions support a scale-dependent capillary–inertial description of rim and ligament breakup. Combined with mass conservation, this scaling gives $N_s\sim We^{9/5}$, providing a numerical explanation for the secondary-droplet-number scaling observed experimentally. Thus, directional impact inertia governs the macroscopic selection of splashing regimes, whereas the secondary-droplet populations across these regimes exhibit a common capillary–inertial fragmentation scaling.
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All authors Ying Xiong, Yang Zhang, Lingling Xie, Xiaolei Li

Instrumentation and Methods for Astrophysics

A generalized likelihood model for segmented muon counters

Joaquín de Jesús, Juan Manuel Figueira, Federico Sanchez et al. (+1 more)

Measurements of the muonic component of extensive air showers constrain cosmic-ray mass composition and hadronic interactions at energies beyond those accessible at accelerators. Arrays of segmented detectors with binary readout are widely used for this purpose: they sample the muon density at different distances from the shower core to reconstruct the muon lateral distribution function (LDF). Each detector response is summarized by the number of activated segments, $k$, whose probability distribution provides the likelihood relating the observation to the expected muon content. Signal pile-up, detector inefficiency, corner-clipping muons, and background signals shape this distribution, and neglecting them can bias the reconstruction. Existing analytical models include pile-up but otherwise assume an ideal detector response. In this work, we develop a unified statistical framework that incorporates inefficiency, corner clipping, and background through a small set of physically interpretable parameters. We derive exact expressions for the detector response and the likelihood required for muon-LDF reconstruction, together with a simple binomial approximation that preserves the main statistical properties of the exact distribution. Dedicated Monte Carlo simulations are used to assess the impact of the assumptions underlying the analytical treatment and show that it is negligible over the parameter range considered. They also show that the exact and approximate likelihoods yield similar performance in terms of estimator bias and confidence-interval coverage. Although motivated by the Underground Muon Detector of the Pierre Auger Observatory, the framework applies more broadly to segmented particle detectors with binary readout in which particle content is inferred from the number of activated segments.
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All authors Joaquín de Jesús, Juan Manuel Figueira, Federico Sanchez, Darko Veberic

Quantum Physics

Pathwise Random Hamiltonian Simulation

Davide Cugini

Randomized product formulas such as qDrift offer a resource-efficient alternative to deterministic Trotter–Suzuki decompositions for Hamiltonian simulation, removing their polynomial dependence on the number of Hamiltonian terms. qDrift, however, is intrinsically limited to first order in the evolution time, so its query complexity remains linear in the inverse of the target accuracy, $1/\epsilon$. We introduce Pathwise Random Hamiltonian Simulation (PRHS), which extends qDrift to arbitrary order by subdividing each time step into $M$ correlated slices, each evolving under a term sampled from a quasi-probability distribution that we construct in closed form and prove unique, with a bias decaying factorially in $M$. Optimizing jointly over the number of slices $M$ and the number of independent blocks $N$ interpolates between the standard qDrift protocol at long times and a high-precision regime where the query cost grows slower than any power of $1/\epsilon$, without requiring ancillary qubits. Numerical simulations of five molecular Hamiltonians confirm this advantage, with PRHS achieving accuracies two to four orders of magnitude beyond qDrift at equal query cost.
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Solar and Stellar Astrophysics

Ion-Scale Waves Regulated by Plasma Beta and Cross Helicity: Observational Evidence for the Helicity Barrier in Imbalanced Solar Wind Turbulence

G. Q. Zhao, R. Meyrand, H. Q. Feng et al. (+3 more)

Ion-scale waves are believed to play an important role in heating of the solar corona and wind, though their generation mechanism remains unclear. Based on Parker Solar Probe observations, this Letter investigates the occurrence of ion-scale waves in the near-Sun solar wind with heliocentric distances between 0.1 and 0.2 au. Results show that the occurrence rate of left-handed polarized waves significantly depends on the plasma beta ($\beta$) and cross helicity ($\sigma_c$). The occurrence rate rapidly increases with decreasing $\beta$ and increasing $\sigma_c$. Overall, the occurrence rate exceeds 45$\%$ when $\beta<0.2$ and $\sigma_c > 0.7$ are satisfied. These observations are consistent with the direct predictions of the helicity barrier theory that suggests the generation of ion cyclotron waves via imbalanced magnetized turbulence.
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All authors G. Q. Zhao, R. Meyrand, H. Q. Feng, H. F. Yang, L. Xiang, Z. Wang

High Energy Physics (Experiment)

Searching for Extra Dimensions and Copies of the Standard Model with IceCube

R. Abbasi, M. Ackermann, J. Adams et al. (+418 more)

The hierarchy problem remains an open question in particle physics. A number of theories that address this problem lower the fundamental scale of gravity, resulting in observable consequences in the neutrino sector. In this work, we place constraints on low-scale gravity scenarios using high-energy neutrinos observed with the IceCube Neutrino Observatory. The analysis is based on 10.7 years of upward-going muon neutrino data in the energy range from 0.5 to 100 TeV. In this energy range, the theories predict characteristic spectral distortions arising from matter effects when neutrinos propagate through Earth. In the context of large extra dimension models, we constrain the compactification radius of the largest extra dimension to $R \lesssim 0.17\,\mu\mathrm{m}$ at $90\%$ confidence level for both normal and inverted neutrino mass ordering. For scenarios with multiple Standard Model copies, we obtain lower limits of up to $N \gtrsim \mathcal{O}(400)$, depending on the value of the lightest neutrino mass. In parts of the parameter space, these results constitute the strongest constraints in the literature to our knowledge, while in other regions they probe previously unexplored parameter space.
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All authors R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, A. Sharma, S. Shefali, N. Shimizu, M. Shin, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, J. A. Urruty, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Solar and Stellar Astrophysics

Type I Solar Radio Bursts Modulated by Solar Flares

Yutong Li, Chuanyang Li, Yanke Tang et al. (+7 more)

Type I solar radio bursts (noise storms) are persistent meter-wave nonthermal emissions above active regions, with their occurrence and proper?ties closely related to the local magnetic configuration and nonthermal electron acceleration. This study examines a type I noise storm on 24 December 2023 and its relation to flare activity. The noise-storm source was co-spatial with active region AR 3529 and showed frequency-dependent spatial dispersion. The associated M2.9 flare strongly modulated the emission, with the storm intensity decreasing at flare onset, recovering afterward, and shifting to higher frequencies. Based on multiwavelength observations, we suggest that pre-flare small-scale reconnection supplied nonthermal electrons to overlying closed magnetic struc?tures and maintained the storm. During the flare, magnetic reconnection above the active region produced bidirectional plasma ejections and type III bursts with bidirectional frequency drifts; the gradually decreasing starting frequency of these bursts may indicate an upward-moving reconnection site. The resulting magnetic reconfiguration disrupted electron trapping and suppressed the storm, whereas post-flare magnetic recovery allowed the emission to resume. These results show that flares can modulate type I noise storms through magnetic restructuring and provide insight into the generation mechanism of noise storms.
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All authors Yutong Li, Chuanyang Li, Yanke Tang, Ning Gai, Zichuan Li, Zhe Cui, Yang Gao, Yifan Wang, Xiaodong Xu, Xiaodi Huo

Instrumentation and Methods for Astrophysics

Soft proton experiments supporting the development of astronomical X-ray instrumentation

S.J. Diebold, B. Heß, F. Pfeifle et al. (+11 more)

Orbital soft protons can severely degrade the performance of astronomical X-ray observatories. On the one hand, they may cause permanent radiation damage to X-ray detectors; on the other hand, they introduce an irreducible background component. Our low-energy grazing-incidence scattering setup provides experimental data for the validation of radiation transport simulations used in the assessment of future X-ray missions. Recent measurements indicate that a significant fraction of protons scattered from X-ray optics undergo charge exchange and therefore cannot be mitigated by magnetic diverters. In addition, we present initial proton-transmission measurements through a thin X-ray filter and compare them qualitatively with TRIM simulations. Quantitative measurements of energy loss and charge-exchange fractions, together with comparisons with TRIM and Geant4, are planned. In this publication, we present the upgraded experimental setup together with commissioning measurements for grazing-incidence scattering and proton transmission through thin X-ray filters.
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All authors S.J. Diebold, B. Heß, F. Pfeifle, L.Ph.H. Schmidt, C. Tenzer, T. Wildfang, D. Ferreira, M. Freyberg, S. Massahi, D. Paredes-Sanz, E. Perinati, A. Santangelo, B. Stelzer, S. Svendsen