Statistical Mechanics
An exact and fast solution of the inverse Regularized Optimal Transport problem
Dario Mazzilli, Riccardo Piombo, Lorenzo Buffa et al. (+1 more)
Optimal transport describes the most efficient way to move mass between two distributions, given a cost
matrix for moving mass between each pair of locations. Entropic optimal transport, solved via the Sinkhorn
algorithm, is a widely used regularized version of this problem. Its inverse problem asks the opposite question: given an observed transport plan, what cost
matrix produced it? This is difficult because the cost is identifiable only up to an additive gauge freedom. Here we show that this freedom can be fixed exactly by a single double-centering operation applied to the observed plan, yielding the true cost
matrix in closed form, with no iterative optimization required. When a modest number of true cost entries are known, the same approach lets us jointly estimate the temperature parameter controlling the entropic regularization, together with a diagnostic for the reliability of this estimate. We further show that the method is not specific to the entropic optimal transport, but extends to a broader class of transport models defined by an invertible relation between cost and plan.
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All authors Dario Mazzilli, Riccardo Piombo, Lorenzo Buffa, Aurelio Patelli
Quantum Physics
A nonabelian anyon violates Haag duality
Daniel Wallick and Henrik Wilming
We show that a superselction sector describing a single nonabelian anyon violates Haag duality, which is equivalent to the fundamental
quantum-information theoretic principle of uniqueness of purifications. We provide a simple physics argument as well as a rigorous proof using sector theory, and instantiate our result concretely in Levin-Wen models. We also show that the associated ground state does not allow for
quantum steering despite being a pure state. Finally, we show that this ground state violates approximate Haag duality, disproving the
conjecture that all gapped ground states satisfy this condition. Our result implies that there are gapped phases of matter where Haag duality fails at every point in the phase.
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Soft Condensed Matter
Intruder dynamics in granular media under localized surface loading
E.M. Franklin, B. Darbois Texier, A. Seguin et al. (+2 more)
We experimentally investigate the dynamics of a spherical intruder driven horizontally at a constant force in a granular medium subjected to a localized surface overload. While intruder motion beneath a free surface exhibits constant acceleration in the quasistatic regime, the presence of a surface load induces a pronounced transient deceleration when the intruder passes below the loaded region. The magnitude of this deceleration increases with the applied overload and saturates at large overloads, while it decreases with intruder depth. Introducing a characteristic timescale and an overload-based Froude number, we show that the deceleration dynamics collapse onto master curves. We further develop a model incorporating stress transmission from the surface, which partially captures the intruder deceleration. In this approach, this deceleration is shown to depend on two parameters: the overload and the area on which this overload is applied. These results provide a framework to quantify how localized surface stresses influence subsurface intruder dynamics, with implications for locomotion, root growth, and underground transport in granular media.
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All authors E.M. Franklin, B. Darbois Texier, A. Seguin, D.D. Carvalho, Y. Bertho
High Energy Astrophysical Phenomena
AGN X-ray coronae at high luminosity: A broadband study of RBS 229 and PG 1407+265
Alessandro Leonardo Lai, Stefano Bianchi, Andrea Marinucci et al. (+8 more)
Context. The X-ray emission of active
galactic nuclei (AGNs) is commonly interpreted as arising from Comptonisation in a hot corona above the
accretion disc. A prominent soft X-ray excess is also observed in many sources and is often explained by a warm Comptonising layer. Aims. We investigate the X-ray-emitting coronae of the luminous
radio-quiet
quasars PG 1407+265 ($z=0.94$) and RBS 229 ($z=0.334$), testing whether a two-corona scenario consistently describes their broadband spectra. Methods. We combine XMM-Newton EPIC and Optical Monitor data with simultaneous NuSTAR observations and long-term Swift monitoring, and model the spectra using Comptonisation models. Results. Both
quasars are X-ray loud relative to the standard $\alpha_{\rm OX}$-$L_{\rm UV}$ relation, with PG 1407+265 showing the strongest deviation. Their spectra are well reproduced by a warm, optically thick Comptonising component accounting for the soft excess and a hot corona producing the hard X-ray continuum. Both sources show high-energy cut-offs at approximately 70-80 keV. RBS 229 exhibits moderate reflection and a weak neutral Fe K-alpha line, while no significant reflection features are detected in PG 1407+265. The warm-corona parameters of RBS 229 remain consistent across epochs, whereas PG 1407+265 shows strong variability, including an extreme soft-excess episode extending to approximately 3 keV in the rest frame. Conclusions. These results constrain AGN coronae in the poorly explored high-luminosity regime. The cut-offs are broadly consistent with trends in AGN luminosity and
accretion rate and remain below the runaway pair-production limit. The contrasting variability suggests that the warm corona responds to changes in the
accretion flow while remaining within a narrow range of physical conditions.
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All authors Alessandro Leonardo Lai, Stefano Bianchi, Andrea Marinucci, Enrico Piconcelli, Francesco Ursini, Elena Bertola, Giorgio Lanzuisi, Pierre-Olivier Petrucci, Daniel Stern, Cristian Vignali, Luca Zappacosta
Quantum Physics
DF-SQD: Deterministic Fields for Sampling-Based Quantum Diagonalization
Kushagra Agarwal and Anupama Ray
Sampling-based
quantum diagonalization method exploits
Quantum-centric supercomputing platforms to sample bitstrings for
Hamiltonian projection on a
quantum computer, and then classically diagonalize the
Hamiltonian to estimate the
eigenvalues and eigenvectors. In current
quantum devices an
algorithm is useful when shallow
quantum circuits with error mitigation support can discover better results while having either a proof of convergence or some method to explain trust in experiment. In this paper, we introduce DF-SQD, a hybrid
algorithm that derives deterministic auxiliary-field
circuits from selected double-factorization leaves of the two-electron tensor. The
circuits propose occupation-number configurations, while selected configuration interaction evaluates the original active-space
Hamiltonian and can recentre subsequent proposal rounds. On N2 (32
qubits; 6-31G basis) and a 40-
qubit [Fe2S2(SCH3)4]2- active-space
Hamiltonian, we show that DF-SQD improves the energy obtained from sampled determinant spaces while using shallow number-preserving
circuits in both simulator and hardware runs. For N2, DF-SQD is 45x more accurate with a 11.23% smaller subspace, and due to its ability to sample better bitstrings at lesser shots it is 2.93x faster than SQD in
quantum devices. For the iron-sulfur cluster, DF-SQD generated a subspace dimension of 221M with 400K shots, while SQD needed 1.5M shots to generate a 238M subspace, thus we have better subspace recovery evident from the hardware at 3.75x reduced shots. At a matched 50M subspace dimension, DF-SQD is 1.32x more accurate (achieves a 24.5% relative error reduction over standard SQD). So overall, our method is able to discover better results with shallower
circuits, is sample efficient, uses configuration recovery (so has targeted error mitigation) and we have empirical convergence observation.
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High Energy Physics (Phenomenology)
Fei Wang and Zi-qiang Zhang
Holographic predictions for vector
meson spin alignment at finite density have been limited by how the chemical potential is implemented. Existing models use a
baryon chemical potential and report that the
alignment is insensitive to it, while zero-density
benchmarks do not address the
geometric deformation. We address this limitation by using a charged AdS black-hole background with a
quark chemical potential and solving the coupled bulk vector equations with infalling horizon conditions. The zero-density limit reproduces previous results of Sheng et al. [Phys. Rev. D 110, 056047 (2024)]. At \(T=0.15~\mathrm{GeV}\), the \(J/\psi\) spectral function has a resonance peak at \(\mu=0\) that lowers and broadens with increasing \(\mu\), whereas the \(\phi\) spectral function shows no pronounced peak. In the helicity frame, \(\rho_{00}\) deviates positively from \(1/3\) for the \(J/\psi\) and negatively for the \(\phi\). The density response is more visible in our setup than the weak
baryon chemical potential sensitivity reported in a four-
flavor soft-wall model. This difference illustrates the model dependence of the density response: it is controlled by the chemical potential normalization. We identify the presence of the resonance peak and the signs of the helicity deviations as robust qualitative features, and treat the numerical shifts of \(\rho_{00}\) as model-dependent estimates.
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Mesoscale and Nanoscale Physics
Alexey A. Sokolik, Azat F. Aminov, Evgenii E. Vdovin et al. (+5 more)
Electron tunneling between sheets of
bilayer Bernal
graphene twisted at different small angles was studied experimentally and theoretically. The current-voltage characteristics exhibit resonant peaks, steps, and regions of negative differential resistance, the origin of which is explained by the intersections of energy- and momentum-shifted electron dispersions of adjacent layers. A theoretical analysis of tunneling transport demonstrated that the key to understanding this phenomenon lies in the competition between two contributions: between like (conductivity-conductivity or valence-valence) and unlike (conductivity-valence) bands of parallel
bilayer graphene sheets. A systematic
evolution of the tunneling current patterns with increase of the twist angle is investigated. Polarization of electron wave function across
graphene sublayers caused by displacement field within
bilayer graphene is shown to strongly affect the tunneling probability, thus enhancing negative differential resistance due to Van Hove singularities at the band edges.
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All authors Alexey A. Sokolik, Azat F. Aminov, Evgenii E. Vdovin, Yurii N. Khanin, Mikhail A. Kashchenko, Denis A. Bandurin, Sergey V. Morozov, Kostya S. Novoselov
Fluid Dynamics
On the Non-Negativity of Longitudinal Velocity Autocorrelations in Homogeneous Isotropic Turbulence: Kinematic Constraints, Convexity, and Spectral Broadening
Pavan B. Govindaraju
A fundamental question in the statistical theory of homogeneous isotropic
turbulence is whether the longitudinal velocity autocorrelation $f(r)$ remains non-negative and if it can be shown from first principles such as kinematic realizability. While incompressibility forces the transverse correlation $g(r)$ to exhibit a negative loop ($\int_0^\infty r g(r)\,dr = 0$), the sign behavior of $f(r)$ is subtle. We show that positive-definiteness via Bochner's and Schoenberg's
theorems structurally fails to enforce pointwise positivity because the 3D spherical projection kernels are sign-changing. By mapping the problem to the one-dimensional spectrum $E_{11}(k_1)$ via the cosine transform and applying Pólya's criterion, convexity of $E_{11}(k_1)$ provides a rigorous sufficient condition for $f(r) \ge 0$. While pure Kolmogorov $-5/3$ scaling is strictly convex, physically realizable spectra with Batchelor ($k^4$) or Saffman ($k^2$) infrared scaling are necessarily concave near $k_1 = 0$. For mature broadband spectra such as the von Kármán–Pao model, high-precision quadrature confirms that the convex inertial bulk dominates, yielding strictly positive tails and demonstrating that apparent negative dips are discrete
Fourier artifacts. Also, we construct a smooth, divergence-free, finite-energy narrowband initial field that produces a genuine negative loop ($\min_r f(r) \approx -0.083$), serving as a counterexample to universal non-negativity. Spectral bandwidth is shown as the governing physical parameter, with nonlinear triad interactions rapidly broadening narrowband fields over an eddy turnover time, systematically suppressing negative excursions and preserving $f(r) \ge 0$ in mature
turbulence.
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Quantum Physics
A Backend-Agnostic MWIS Kernel for Stochastic Unit Commitment with Neutral-Atom Hardware Validation
Jiying Chen, Min Lin, Jingwei Wen et al. (+2 more)
Quantum hardware is beginning to address structured combinatorial optimisation, but two steps still block practical use: mapping real operational models onto hardware-compatible instances, and converting noisy hardware output back into feasible decisions. Here we introduce a backend-agnostic computational interface that compiles the discrete decision layer of
stochastic unit commitment into a move-based maximum-weight independent set (MWIS) problem, while retaining continuous dispatch and feasibility recovery in the classical computational layer. We validate the approach in a green hydrogen scheduling setting and deploy it on the QuEra Aquila neutral-atom
quantum processor. This is the first end-to-end industrial scheduling workflow that connects real operational decisions to programmable neutral-atom hardware through a solver-agnostic MWIS representation. Across a 15-day hardware campaign on 50-node instances, hardware-generated solutions after classical refinement match or exceed the dispatch margins obtained from exact MWIS on every day. When scaling to 144 nodes, encoding quality remains stable, while the probability that the full atom array survives, rather than graph
embedding, emerges as the dominant bottleneck to further scaling. Together, these results establish a hardware-compatible computational pathway toward larger problem scales, and lay the groundwork for exploring regimes in which exact classical optimisation may no longer scale efficiently.
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All authors Jiying Chen, Min Lin, Jingwei Wen, Zhihong Zhang, Chuixiong Wu
Computational Physics
A Non-Isothermal Viscoplastic Constitutive Model for Clay Slip Surfaces
Saeed Tourchi, Ehsan Badakhshan, Milad Jabbarzadeh et al. (+2 more)
Clayey slip surfaces control the reactivation and long-term deformation of slow-moving landslides and may experience thermal fluctuations from
climate, seasonal ground-temperature changes, or subsurface heat sources. Experiments show that residual shear strength depends on temperature and shearing rate, yet most numerical approaches use temperature-independent strength parameters. We present a non-isothermal viscoplastic constitutive model for clayey slip surfaces implemented with zero-thickness interface elements. It includes temperature-dependent normal and tangential stiffness, progressive degradation of cohesion and friction angle, and rate-dependent viscoplastic slip governed by a non-associated flow rule. Coupling with hydraulic and thermal balance equations allows the interface response to evolve with stress state, temperature, aperture, and accumulated irreversible displacement. Validation against temperature-controlled drained ring-shear tests on bentonite and smectite-rich soils covers heating–cooling, cooling–heating, and combined thermal paths. The simulations reproduce thermal strengthening at slow shearing rates and thermal weakening or limited sensitivity at higher rates. Application to the Congress Street cut
benchmark shows that zero-thickness elements improve the representation of strain localization and progressive failure. Increasing temperature progressively degrades interface strength, increases displacement, joint aperture, and shear strain, and accelerates sliding. Temperature-dependent interface degradation can therefore reduce the apparent stability margin of clayey slopes and should be included in slope-stability assessments involving thermal fluctuations.
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All authors Saeed Tourchi, Ehsan Badakhshan, Milad Jabbarzadeh, Arash A. Lavasan, Jean Vaunat
Mesoscale and Nanoscale Physics
Alejandro S. Gómez, Rafael A. Molina, Pablo Burset et al. (+1 more)
Achieving robust topological superconductivity with multiple Majorana channels is a key step for scalable topological
quantum computing. To this end, we investigate magnetically doped three-dimensional topological
insulator heterostructures proximitized by an s-wave
superconductor within a fully three-dimensional extended Bernevig-Hughes-Zhang framework that explicitly accounts for vertical confinement. We show that
magnetic exchange coupling, orbital mixing, and bulk band inversion cooperate to generate effective equal-
spin p-wave pairing channels supporting multiple
chiral Majorana modes. The number of Majorana channels is determined by the confined modes in the vertical direction and the high-Chern-number phases of the normal state, which allows us to derive an analytical criterion for the emergence of the multiple-Majorana topological superconducting phases. The
chiral Majorana modes remain robust against strong disorder and moderate
symmetry-breaking perturbations. We also demonstrate that a superconducting phase difference defining a vertical Josephson junction acts as a tunable parameter that controls the hybridization, minigap, and effective multiplicity of the low energy Majorana channels. Our results establish
magnetic three-dimensional topological-
insulator heterostructures as a promising platform for engineering multiple
chiral Majorana modes.
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All authors Alejandro S. Gómez, Rafael A. Molina, Pablo Burset, Yuriko Baba
Atomic Physics
Polarization measurements of the $2s$–$2p_{3/2}$ VUV transition in N$^{4+}$ excited by electron collisions
Nobuyuki Nakamura, Ryohko Ishikawa and Motoshi Goto
We present the linear polarization of the $2s$–$2p_{3/2}$ transition in Li-like N$^{4+}$ excited by electron collisions, measured at electron energies between 85 and 1000~eV. The measured polarizations are compared with theoretical values calculated using the Flexible Atomic Code (FAC). Although the overall trend that the degree of polarization decreases with increasing electron energy is reproduced, the theoretical values are systematically larger in magnitude than the experimental values. After examining possible experimental sources of depolarization, we suggest that the discrepancy likely originates from an overestimation in the theoretical model. Further theoretical and experimental investigations along the isoelectronic sequence are needed to resolve this discrepancy.
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Optics
Exceptional Points in Photonics: From Non-Hermitian Physics to Applications
Fan Zhang, Nikolay Solodovchenko, Dmitrii N. Maksimov et al. (+5 more)
Open photonic systems provide a versatile platform for non-Hermitian physics, enabling control over complex spectra, transport, and light-matter interactions. Exceptional points (EPs), at which
eigenvalues and eigenvectors coalesce and the governing operator becomes defective, play a central role because they combine branch-point spectral
topology, nonanalytic perturbative response, and controllable eigenstate conversion. This Review provides a unified framework for EP photonics by systematically distinguishing exceptional degeneracies according to the underlying operator, spectral variable, boundary conditions, and experimentally accessible observables. We discuss
Hamiltonian EPs, absorbing EPs associated with scattering zeros, real-frequency scattering-
matrix and Jones-
matrix EPs, Bloch and Floquet EPs, and Liouvillian EPs in open
quantum systems. We review their spectral
topology, static and dynamical encircling, higher-order exceptional structures, and coexistence with bound states in the continuum, together with applications in sensing, lasing, coherent absorption, directional scattering, polarization and wavefront control, nonlinear optics, optical storage, nonreciprocal photonics, and
quantum photonics. We also critically assess the current limitations, practical challenges, and future perspectives of EP-based photonic technologies, with particular
attention to robustness, noise, scalability, and experimentally measurable performance.
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All authors Fan Zhang, Nikolay Solodovchenko, Dmitrii N. Maksimov, Xuchen Wang, Mingzhao Song, Filippo Capolino, C. T. Chan, Andrey Bogdanov
Cosmology and Nongalactic Astrophysics
First tomographic measurements of the angular clustering and bias of photometric quasars from S-PLUS
Maria Lopes, Felipe Avila, Armando Bernui et al. (+1 more)
We investigate the
quasar clustering in the QuCatS photometric catalog, constructed from the fourth data release of the Southern Photometric Local Universe Survey (S-PLUS). The
quasar sample for this study consists of $23,402$
quasars, spanning the
redshift interval $1.1 \leq z_{\rm phot} \leq 2.6$, which we divided into four bins for our tomographic analyses. In each bin, we measured the two-point angular correlation function and compared it with theoretical predictions for the clustering of dark matter in the flat-$\Lambda$CDM cosmological model. We then estimate the effective linear bias in each bin that best fits the data, obtaining $b_{Q}(z_{\rm eff}=1.26)=2.17^{+0.30}_{-0.35}$, $b_{Q}(z_{\rm eff}=1.63)=2.67^{+0.36}_{-0.42}$, $b_{Q}(z_{\rm eff}=2.04)=3.29^{+0.52}_{-0.62}$, and $b_{Q}(z_{\rm eff}=2.38)=4.05^{+0.71}_{-0.86}$. These measurements are consistent with previous analyses in the literature. Moreover, the
evolution of the bias agrees well with the $b(z)$ parameterization proposed by \cite{laurent2017}. Our measurements constitute the first cosmological study of the tomographic clustering of photometric
quasars provided by the S-PLUS
dataset, contributing to the mapping of the
evolution of linear bias and paving the way for future analyses of data releases with larger
datasets. In addition, our study also serves as a consistency test for the calibration procedure of the photometric
redshift probability distributions of the
quasars in the QuCatS catalog.
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All authors Maria Lopes, Felipe Avila, Armando Bernui, Lilianne Nakazono
Mesoscale and Nanoscale Physics
Interferometry reveals spin-singlet fractional quantum Hall edges in graphene
R. Ayache, K. Kim, M. Kuiri et al. (+7 more)
The edge modes of
spin-singlet fractional
quantum Hall (FQH) phases are manifestations of multicomponent topological order and SU(2)
spin symmetry. An archetype is the
spin-unpolarized state at $\nu$=2/3, whose edge is expected to host spatially coexisting yet counter-propagating charge and neutral
spin modes. Despite efforts, its edge properties, including
spin coherence and
spin-charge separation, have remained elusive owing to the difficulty of resolving
spins in FQH edge transport. Here, we develop a
spin-sensitive probe of
graphene FQH edges by using a p-n junction to interface a target FQH state with a probe integer
quantum Hall (QH) state of opposite polarity. An Aharonov-Bohm (AB) interferometer forms along the interface, when the target and probe edge channels carry the same
spin. We identify the
spin-unpolarized and polarized edges of the $\nu$=2/3 states at lower and higher
magnetic fields, respectively, through
spin-dependent interference. A novel multiparticle AB interference between two electrons of opposite
spin emerges from
spin-charge separation and recombination on the unpolarized edge, featuring a
spin swap. Our results establish edge transport as a probe of
spin-singlet topological orders, with implications for parafermion platforms in
graphene-
superconductor hybrids.
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All authors R. Ayache, K. Kim, M. Kuiri, Q. Benichou, H. Chakraborti, L. Pugliese, K. Watanabe, T. Taniguchi, H.-S. Sim, P. Roulleau
Nuclear Theory
Fundamental geometric limitations on disentangling nuclear-surface properties in relativistic heavy ion collisions
Hadi Mehrabpour, Behnaz Behzadmoghaddam, S. M. A. Tabatabaee Mehr et al. (+2 more)
The extraction of the
nuclear surface diffuseness from relativistic heavy ion collisions is limited by the intertwined responses of geometry-driven observables to surface diffuseness and intrinsic
nuclear deformation. We investigate this limitation using event-by-event Monte Carlo Glauber simulations, focusing on the sensitivity of multiparticle correlations to the Woods–Saxon surface diffuseness $a_0$ in intrinsically deformed
nuclei. We systematically examine the local correlations between $a_0$ and quadrupole and octupole deformation parameters, $\beta_2$ and $\beta_3$, and determine how these correlations affect the ability of different observables to constrain $a_0$. We find that observables dominated by
elliptic geometry exhibit a strong response to quadrupole deformation, leading to a local $a_0$–$\beta_2$ degeneracy that substantially limits their sensitivity to the
nuclear surface diffuseness. Triangular correlations provide a more independent response to the
nuclear surface and therefore retain additional information on $a_0$, although their sensitivity can also be modified by intrinsic deformation. Extending the analysis to simultaneous quadrupole and octupole deformation shows that the local degeneracy and least-constrained directions depend on the
nuclear configuration, demonstrating that the limitation on extracting $a_0$ is not described by a single global parameter correlation. We quantify these effects using multidimensional response maps, local sensitivity and information-
geometric measures, and a
Bayesian analysis of the resulting parameter constraints. The results clarify the fundamental limitations imposed by intrinsic multipole deformation on the determination of
nuclear surface diffuseness from relativistic heavy ion collisions and identify multiparticle correlations that provide more independent information on $a_0$.
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All authors Hadi Mehrabpour, Behnaz Behzadmoghaddam, S. M. A. Tabatabaee Mehr, Oscar Garcia-Montero, Li Yan
Materials Science
Geometry-Controlled Magnetic and Electronic Landscapes in Anisotropic van der Waals Materials
Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska et al. (+10 more)
Electronic structure in van der Waals materials is commonly engineered through composition, strain, electrostatic gating and
heterostructure assembly. Here we introduce geometronics, a concept in which substrate geometry locally reorients an anisotropic
crystal, transforming homogeneous external perturbation into programmable
magnetic and electronic landscapes. We demonstrate this concept using a
bilayer of the
antiferromagnetic semiconductor CrSBr transferred onto an inverted pyramidal nanoindentation, where the local
crystal orientation with respect to the external
magnetic field drives the coexistence of
antiferromagnetic and
ferromagnetic phases within a single continuous
crystal. The resulting
magnetic landscape creates a switchable excitonic potential well of up to 10–12 meV, directly visualised by spatially resolved spectroscopy. More generally, geometronics provides a universal route for deterministically programmed electronic and
magnetic landscapes without modifying the material itself. It therefore establishes substrate topography as a new design principle that exploits the intrinsic anisotropy of layered van der Waals materials.
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All authors Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska, Bartosz Hołyński, Gayatri, Grzegorz Krasucki, Mariusz Hasiak, Kseniia Mosina, Zdenek Sofer, Adam Babiński, Maciej R Molas, Paulina Plochocka, Michał Baranowski
Instrumentation and Methods for Astrophysics
4MOST Low Resolution Spectrographs Characterization in Chile
Florence Laurent, Didier Boudon, Eric Daguise et al. (+14 more)
4MOST, the 4m Multi Object Spectroscopic
Telescope, is the optical, fibre-fed, MOS facility for the VISTA
telescope at ESO's Paranal Observatory in Chile. Its main science drivers are in the fields of
galactic archeology, high-energy physics,
galaxy evolution and cosmology. The 4MOST consortium consists of several institutes in Europe and Australia under leadership of the Leibniz-Institut fur Astrophysik Potsdam (AIP). This paper focuses on the successful testing, installation and technical commissioning of the Low Resolution Spectrographs (LRS-A and B) for the 4MOST instrument at ESO's Paranal Observatory, Chile. This work was completed on October 18. 2025. Details on the assembly, integration, and performance of both 4MOST spectrographs from their arrival in the integration
hall through to the
telescope installation are provided.
Attention is given to the optimization of procedures implemented to enhance performance and meet the expected top-level requirements. The 4MOST LRS features 2436 fibres split into two low-resolution spectrographs LRS-A and LRS-B (1624 fibres, three arms, 370-950 nm, R > 4000) and one high-resolution spectrograph (812 fibres, three arms, ~44-69 nm coverage each, R > 18000). The fibre positioner covers a hexagonal field of view of ~4.1 deg2. The fibers are 85 {\mu}m core with an output beam at f/3. The Centre de Recherche Astrophysique de Lyon (CRAL) had the full responsibility for the two low-resolution spectrographs. Each of them is composed of an off-axis Schmidt collimator that produces a 200 mm beam, which is split into three spectral arms by dichroics and directed to F/1.73 cameras with standard 6k x 6k 15 microns pixel CCD detectors.
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All authors Florence Laurent, Didier Boudon, Eric Daguise, Remi Giroud, Aurelien Jarno, Alexandre Jeanneau, Andreas Kelz, Jens-Kristian Krogager, Victor Mauger-Vauglin, Jean-Emmanuel Migniau, Matthew Lehnert, Flora Paganelli, Arlette Pecontal, Emmanuel Pecontal, Alban Remillieux, Johan Richard, Allar Saviauk
Superconductivity
Thermodynamics of $T_{\rm c}$ suppression in far-overdoped Tl$_2$Ba$_2$CuO$_6$
Ayanesh Maiti, David M. Broun, Seunghyun Khim et al. (+7 more)
The physical origin of the suppression of superconductivity with hole doping in overdoped cuprates remains unclear. We measure the electronic specific heat of microgram-scale Tl$_2$Ba$_2$CuO$_6$
crystals and find sharp superconducting anomalies persisting far into the overdoped regime. A weak-coupling BCS-like framework incorporating the known
Fermi surface and cation disorder quantitatively reproduces the observed anomalies for $T_{\rm c}=14$-$25$ K and their weak doping dependence. The results show $T_{\rm c}(p)$ to be driven predominantly by a smoothly decreasing pairing strength.
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All authors Ayanesh Maiti, David M. Broun, Seunghyun Khim, Michal Moravec, Antony Carrington, Carsten Putzke, Vivek Mishra, Peter Hirschfeld, Andrew P. Mackenzie, Andreas W. Rost
Materials Science
Autonomous discovery of new structure-plausibility laws for explainable and rapid crystal diagnosis and screening
Zhilong Song and Lixue Cheng
Crystal generators and tool-using
agents propose structures faster than density functional theory (DFT) energy and
phonon calculations or experiments can assess them. Deciding which candidates merit expensive assessment is therefore the bottleneck, yet most screens test little beyond atomic overlap and give no chemical reason for failure. Here, our
agents generate, test and actively refute two million candidate laws, leaving eight Plausibility Rules for Inorganic Structures (PRIS). These laws encode five mechanisms: short-range repulsion, ionic contact and packing, electrostatic balance, bond-valence conservation and crystallographic site complexity. Experimental structures satisfy our law sets at 82–99%, but satisfy Pauling's rules 2–5 together at only 6.5%. The strictest set detects 87.9% of damaged
crystal structures, whereas distance cutoffs detect only 1.6–3.2%. PRIS plausibility is linearly correlated with synthesizability, so the PRIS-derived synthesis score (PSS) explainably screens 83.7% of hard-to-synthesize structures while retaining 80.7% of experimental structures. In a property-conditioned inverse-design run, PRIS and PSS can reduce the DFT validation queue by up to 67.3% and keep 99.2% of the candidates whose DFT-validated bulk
moduli reach the design target. Beyond screening, PRIS explains why GNoME remains enriched in rare low-
symmetry structures and reveals how wrong-element assignments in falsified
crystal reports hide behind plausible coordinates. PRIS moves screening from a pass-or-fail verdict to a chemical reason for failure, showing that autonomous
agents can discover, by active refutation, physicochemical laws that guide calculations and experiments.
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Astrophysics of Galaxies
Slow stellar halo rotation as a signature of disc flips and GES-like mergers
Kirill Batrakov, Alis J. Deason, Francesca Fragkoudi et al. (+3 more)
The
stellar halo of the Milky Way (MW) exhibits a weak net prograde rotational signal ($v_{\phi} \lesssim 25$ km~s$^{-1}$), yet its origin remains unexplained. To investigate this, we use the Auriga cosmological simulation suite of MW-mass
haloes to probe the rotation of
stellar haloes over the
redshift range $z_{\mathrm{red}}=0-2.5$. The rotational signal is found to persist over this
redshift range. We show that satellite progenitors of the
stellar halo exhibit a non-uniform distribution of infall directions, with a tendency to align with the host disc, albeit with significant scatter. Thus, we attribute the net rotation to the anisotropic
accretion of satellites.
Haloes that host
Gaia-Enceladus-Sausage (GES)-like substructures exhibit consistently slower rotational velocity, likely due to the head-on, more radial trajectory of the dominant progenitor in such systems.
Haloes whose
stellar discs have reorientated by $\geq 90^{\circ}$ also exhibit slower rotation, likely because the longer dynamical timescales of
haloes prevent them from quickly adjusting to disc reorientations. We also report a correlation between the rotation of
stellar and dark matter
haloes, suggesting a possible common origin driven by anisotropic
accretion. We therefore suggest that the MW experienced a disc flip and has a slowly rotating dark matter
halo.
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All authors Kirill Batrakov, Alis J. Deason, Francesca Fragkoudi, Thomas Tomlinson, Azadeh Fattahi, Vasily Belokurov
Solar and Stellar Astrophysics
A wavelet-based model of magnetic turbulence over a Parker spiral field
Andrea Larosa, Francesco Pucci, Francesco Malara et al. (+7 more)
The propagation of
Solar Energetic Particles (SEPs) through the heliosphere is strongly influenced by
solar-wind
magnetic turbulence, which governs particle scattering, field-line wandering, and cross-field transport. These processes shape SEP intensity profiles, anisotropies, and arrival times. Because heliospheric
turbulence spans a vast range of scales, direct numerical simulations cannot capture its full spectrum. Synthetic
turbulence models provide an efficient alternative by generating fields with prescribed statistical and spectral properties, enabling realistic studies of SEP transport. This work presents a numerical model able to generate synthetic
magnetic turbulence in the heliosphere with the goal of studying field line and particle
diffusion. The model is inspired by in situ
solar wind observations, indicating that
solar wind
turbulence properties vary with the distance from the Sun. We extend the Cartesian wavelet-based Synthetic
Turbulence Model (STM), presented in \cite{Malara2016PhRvE..94e3109M}, to the non-homogeneous expanding
solar wind. This is achieved by finding a suitable change of coordinates that allows one to pass from a space in which the
turbulence correlation length is homogeneous to one in which it is not. We present the analytical derivation, the numerical implementation, and testing. We obtain an improved and computationally efficient synthetic
turbulence model characterized by a background Parker spiral, a broad inertial range and tunable radial scalings for both the correlation length and the
magnetic-field fluctuation amplitude, as well as a controllable level of intermittency. The model capability of reproducing
solar wind
turbulence up to the particle Larmor scale and to take into account
solar wind radial
evolution makes it a powerful tool to study the propagation of SEPs throughout the heliosphere.
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All authors Andrea Larosa, Francesco Pucci, Francesco Malara, Oreste Pezzi, Silvia Perri, Gaetano Zimbardo, Giuseppe Nisticò, Federica Chiappetta, Massimo Chimenti, Luca Sorriso-Salvo
Astrophysics of Galaxies
The Physical Conditions of Low-Mass Galaxies at z=3.5-7.0 from JWST Spectroscopy: The Behaviour of Spectral Line Ratios with Burstiness
Ryan A. Cooper, Karina I. Caputi, Alessandro Marconi et al. (+5 more)
We present a study of the physical conditions of
galaxies at
redshifts $z=3.5-7.0$, based on emission-line diagnostics of JWST NIRSpec spectra for 1889
star-forming sources spanning more than 4~dex in
stellar mass. We find that the median H$\alpha$/H$\beta$ and [OIII]/H$\beta$ are constant throughout these
redshifts, indicating a slow
evolution of the interstellar medium conditions from the Epoch of Reionization to
Cosmic Noon. The
stellar-mass
evolution of these line ratios follow the expected trend for chemical enrichment and
dust build-up, with \ohb~being maximum for
galaxies with $\rm M_{\star} \approx 10^9 \, \rm M_\odot$, and the medians of H$\alpha$/H$\beta$ and [OII]/H$\beta$ monotonically increasing from $\rm{M}_{\rm \star} \approx 10^7$ through $ \approx 10^{10}\, \rm M_\odot$. Focusing on the 1552 low
stellar-mass ($<10^9 \, \rm M_\odot$)
galaxies, we particularly investigate the behaviour of the main spectral-line ratios with burstiness. We find a significantly higher degree of scatter in [OIII]/H$\beta$ and [OII]/H$\beta$ for high-burstiness than for low-burstiness
galaxies. Values of log([OIII]/H$\beta$)~$\gtrsim 0.8$ are almost exclusively seen amongst those with high burstiness. Meanwhile, log([OIII]/H$\beta$)~$\lesssim 0.3$ are virtually not found amongst high-burstiness
galaxies, except at the lowest
stellar masses $\mathrm{log(M_\star/M_\odot)}<7.5$. Our results are consistent with a scenario in which
star-formation bursts produce temporary chemical enrichment that is quickly lost via
stellar winds. They also suggest that
metallicity measures in bursting
galaxies are unstable, and that the search for the most metal-poor objects should optimally be conducted amongst low-burstiness or very low-
stellar mass sources.
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All authors Ryan A. Cooper, Karina I. Caputi, Alessandro Marconi, Anna Feltre, Edoardo Iani, Pierluigi Rinaldi, Guillaume Desprez, Harley Katz
Quantum Physics
Unbiased sampling from Boltzmann distributions with noisy energies
Iwo Sanderski, Gian Gentinetta and Giuseppe Carleo
Sampling from the Boltzmann distribution is central to computational physics, yet hard when the energy is known only through a
stochastic estimate, such as with machine-learned molecular potentials, in variational Monte Carlo, or on
quantum computers, because a noisy energy biases the sampled distribution. The penalty method of Ceperley and Dewing corrects this but requires the noise variance and becomes intractable when it is large. We introduce the Poisson product
estimator, an unbiased, non-negative
estimator of the Boltzmann weight that only needs an upper bound on the energy
estimator and remains efficient at high noise. Using it to optimize a variational
quantum circuit gradient-free, we recover the $H_3^+$ ground-state energy in a minimal basis and, by sampling rather than following a single trajectory, also map the variational energy landscape.
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High Energy Physics (Phenomenology)
Angular correlations and polarization in $Z$+jet production at the LHC
Francesco Giovanni Celiberto and Francesca Lonigro
Precision studies at the LHC increasingly require theoretical control over QCD radiation beyond fixed-order perturbation theory, particularly in final states characterised by large separations in rapidity. High-energy logarithms can generate corrections at the ten-percent level even for electroweak-scale observables, as recently observed in
Higgs production, motivating their systematic inclusion in precision analyses. We investigate this regime through Drell$-$Yan plus jet production, with particular emphasis on $Z$-
boson final states and their angular and polarisation structure. High-energy logarithms are resummed at next-to-leading logarithmic accuracy and consistently combined with NLO fixed-order information. Beyond inclusive rapidity and transverse-momentum spectra, the framework resolves the azimuthal harmonic content of the process, whose pattern is reshaped by the transition from leading- to next-to-leading-order emission dynamics. We further develop the JETHAD$-$DYnamis$-$POWHEG strategy towards realistic
lepton-level predictions, retaining
spin correlations, decay-angle information, and experimentally accessible kinematics. This programme establishes $Z$+jet production as a precision probe of high-energy QCD dynamics for Run~3 and the HL-LHC.
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Instrumentation and Methods for Astrophysics
Exploring reinforcement learning to enhance focal-plane wavefront control for vortex coronagraphs
Iremsu Taskin, Jalo Nousiainen, Gilles Orban de Xivry et al. (+2 more)
High Contrast Imaging (HCI) on ground-based
telescopes suffers from phase aberrations on the observed wavefront caused by atmospheric
turbulence. Adaptive Optics (AO) systems are adept at correcting these aberrations, but fall short in the correction of non-common path aberrations (NCPAs). NCPAs arise because the wavefront sensor (WFS) measures and corrects a wavefront that is different from that affecting the science images, thus requiring additional intervention. This work makes use of focal-plane wavefront sensing and reinforcement learning (RL) to address the wavefront aberrations caused by NCPAs. The PO4NCPA
algorithm utilizes sequential phase diversity to address phase ambiguities and is tested on a simulation designed for the Mid-infrared ELT Imager and Spectrograph (METIS) instrument. In this paper, we present the performance of PO4NCPA with scalar and vector
vortex coronagraphs to demonstrate its flexibility.
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All authors Iremsu Taskin, Jalo Nousiainen, Gilles Orban de Xivry, Olivier Absil, Markus Kasper
Statistical Mechanics
Dynamical phase transitions for single particles in the semiclassical and weak noise limits
Norayr Asriyan, Jan Meibohm, Vasco Cavina et al. (+1 more)
We present a unifying description of dynamical phase transitions in the
unitary evolution of an isolated
quantum particle and the dissipative relaxation of a classical Brownian particle, based on a dynamical generat- ing function. In the semiclassical and weak-noise limits, Fisher zeros of this function condense in the complex- time plane and reach the corresponding physical axes, producing dynamical phase transitions through a competition between return trajectories. This establishes a direct connection between
quantum and classical (finite-time) dynamical phase transitions, where the semiclassical limit plays the role of the thermodynamic limit. In particular, the established link naturally provides a classical version of the Loschmidt amplitude and shows how dynamical
quantum phase transitions, typically associated with isolated many-body systems, can arise in a single-particle
quantum system. The dynamical phases are distinguished by a unifying, trajectory- based order parameter, realized as a classical correlation function and a sequential
quantum weak value.
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All authors Norayr Asriyan, Jan Meibohm, Vasco Cavina, Massimiliano Esposito
High Energy Physics (Phenomenology)
Deviation from $\mu-\tau$ reflection symmetry under radiative corrections in the minimal seesaw framework
Prokash Pegu and Chandan Duarah
The $\mu$-$\tau$ reflection
symmetry predicts a maximal atmospheric mixing angle, $\theta_{23}=\pi/4$, and Dirac CP phase, $\delta=\pi/2$ or $3\pi/2$. Recent global analyses indicate small but significant deviations from these predictions, suggesting that the
symmetry is approximate and requires breaking. Motivated by this, we study the breaking of $\mu$-$\tau$ reflection
symmetry induced by radiative corrections in the minimal seesaw framework, assuming the
symmetry to be exact at the high-energy seesaw scale $\Lambda_{\mu\tau}=10^{14}~\mathrm{GeV}$. A distinctive feature of the minimal seesaw is that one light
neutrino remains massless, leaving only one physical Majorana CP phase. Starting from the integral solution of the one-loop RGE for the effective Majorana
neutrino mass
matrix, we derive analytical expressions for the low-energy
neutrino parameters at $\Lambda_{\mathrm{EW}}=172.76~\mathrm{GeV}$ in terms of their high-energy counterparts. We then numerically estimate the low-energy parameters within the MSSM, taking $\Lambda_s=1~\mathrm{TeV}$ and $\tan\beta=10$, $30$ and $50$. The analysis is performed separately for Normal Order (NO) and Inverted Order (IO). We find that the predicted
neutrino masses and mixing parameters are consistent with current experimental data in both scenarios. The sum of
neutrino masses, Jarlskog invariant $J$, and effective Majorana mass $|\langle m\rangle_{ee}|$ also satisfy current experimental constraints. Finally, we estimate the amount of deviations of the low-energy
neutrino parameters from their high-energy values and investigate their dependence on $\tan\beta$. We find that the magnitude of these deviations increases with increasing $\tan\beta$ for both NO and IO.
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Cosmology and Nongalactic Astrophysics
Angular power spectrum of induced gravitational waves: breaking model and parameter degeneracies in PTA observations
Peng-Yu Wu, Di Wu and Jing-Zhi Zhou
Large
primordial curvature and tensor perturbations on small scales can generate second-order tensor-scalar induced gravitational waves (TSIGWs) through scalar-scalar, tensor-scalar, and tensor-tensor source terms. TSIGWs are recognized as one of the principal contributors to the
stochastic gravitational wave background (SGWB) observations. We explore the energy density spectrum of second-order TSIGWs in the presence of non-Gaussian
primordial curvature perturbations. Furthermore, we present the first calculation of the anisotropic angular power spectrum associated with second-order TSIGWs, which provides a promising tool to discriminate them from other SGWB sources.
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Optics
Low-threshold vortex lasing in three-dimensional cavities via flatband bound states in the continuum
Zi-Xin Zhou, Weimin Wang, Huijie Li et al. (+2 more)
Bound states in the continuum (BICs) offer a robust route toward high-Q resonators and topological structured-light generation. While optically pumped BIC
lasers have advanced significantly, realizing electrically pumped
vortex lasers remains challenging due to conflicting requirements for optical confinement and carrier injection. Here, we demonstrate an electrically pumped vector
vortex laser based on a photonic
crystal-guiding layer-distributed Bragg reflector (PC-GL-DBR)
heterostructure. The photonic
crystal slab precisely tailors the
symmetry and dispersion of BIC modes, including a flatband BIC state, while an intermediate guiding layer enables optical mode engineering without directly patterning the multiple-
quantum-well active region, preserving efficient carrier injection and strong optical confinement. Under optical pumping, the device achieves single-mode lasing with a Q of 9700, a threshold of 0.129 kW/cm$^2$, and a side-mode suppression ratio of 26 dB. Crucially, room-temperature electrically pumped
vortex lasing is achieved with a low turn-on voltage of 1.8 V, a threshold current density of 0.13 kA/cm$^2$, and a cavity Q of 8600, successfully preserving the characteristic vector-
vortex emission of the topological BIC state. These results establish a practical route toward electrically driven BIC
vortex lasers for integrated structured-light sources and topological photonics.
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All authors Zi-Xin Zhou, Weimin Wang, Huijie Li, Yan-qing Lu, Jun-Long Kou