Superconductivity
Enhanced Superconductivity in Multilayer FeSe Films by Simplified Molecular Beam Epitaxy
Maria Hilse, Hemian Yi, Zhe Chen et al. (+7 more)
Multi-unit-
cell (UC) e̱ta}-FeSe films grown on SrTiO3(100) continue to attract
attention because of the significant enhancement in the superconducting transition temperature (Tc) compared to that in bulk FeSe. In prior reports of molecular beam epitaxy (MBE)-grown e̱ta}-FeSe/SrTiO3(100), elaborate growth protocols have been used to achieve enhanced Tc, leading to a general belief that careful pre-treatment of the SrTiO3 substrate and post-growth annealing in ultrahigh
vacuum (UHV) are essential. Here, we report a greatly simplified protocol for the MBE growth of superconducting multi-UC e̱ta}-FeSe films on SrTiO3(100), eliminating the need for careful substrate pre-treatment and post-growth UHV annealing while still achieving an enhanced Tc. With appropriate capping, epitaxial films with 14 UC thickness exhibit a zero-resistance transition temperature Tc ~ 20 K in ex situ electrical transport measurements. The MBE optimization process is guided by the growth-parameter dependencies of film morphology and structural properties, as characterized by reflection high-energy electron diffraction, X-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy.
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All authors Maria Hilse, Hemian Yi, Zhe Chen, Jessica L. Thompson, Kalana D. Halanayake, Danielle Reifsnyder Hickey, Seong H. Kim, Cui-Zu Chang, Nitin Samarth, Roman Engel-Herbert
High Energy Physics (Phenomenology)
Resummed Power Corrections in Nuclear DVCS
John Terry
Generalized Parton Distributions (GPDs) encode the three-dimensional structure of
hadrons, yet their modification in
nuclear matter remains largely unconstrained. We report the first derivation of resummed QCD power corrections to deeply virtual Compton scattering on
nuclei. Extending techniques from inclusive deep inelastic scattering, we identify the
nuclear-enhanced higher-twist contributions generated by coherent final-state scattering of the struck
quark in the medium and resum them to all orders. The corrections are enhanced by an effective
nuclear size $A_{\rm eff}^{1/3}$ and result in an exclusive analogue of dynamical
nuclear shadowing. The shift is controlled by a parameter already fixed by inclusive
nuclear data, so no new nonperturbative input enters. We present quantitative predictions for
nuclear modifications of beam-
spin observables at the Electron–Ion
Collider.
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High Energy Physics (Theory)
Hagedorn temperature from holography: rotating and charged systems
Francesco Bigazzi, Tommaso Canneti, Federico Castellani et al. (+1 more)
Using the string/field theory correspondence as a tool, we study the dependence of the Hagedorn temperature of strongly coupled, planar gauge theories on angular velocities and chemical potentials for $U(1)$ global currents. Our results are obtained from an interplay of world-sheet semiclassical quantization methods and target space low energy effective ones. The Hagedorn temperature is given as an expansion in the inverse (large) 't Hooft coupling limit. Working to quadratic order in the fluctuations, the world-sheet analysis provides the leading, the next-to-leading and part of the next-to-next-to leading order terms. In particular, it captures the NNLO $\log 2$ terms which are due to the contributions of non-zero modes to the zero-point energy. These modes are not accounted for by the effective approach, within which they have to be included by hand using suitable educated guesses. On the other hand, the effective methods allow to compute in a relatively easy way the missing NNLO pieces (and even further subleading corrections), which could be accounted for from the world-sheet approach only working at quartic (or higher) order in the fluctuations. We present general results and several examples in various dimensions, including both confining models and conformal field theories on spheres (such as $\mathcal N=4$ SYM and ABJM) dual to string theories on global $AdS$ spaces.
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All authors Francesco Bigazzi, Tommaso Canneti, Federico Castellani, Aldo L. Cotrone
Biological Physics · Cross-listed from q-bio.PE
Global geometry of the genotype-phenotype map illuminates a trade-off between penetrance and mutational adaptability
Yutaro Ikeda, Kunihiko Kaneko and Tetsuhiro S. Hatakeyama
Evolution in changing environments requires both reliable expression of the currently favored phenotype, as quantified by penetrance, and the capacity to reach alternative phenotypes through mutation. Previous studies suggest that high penetrance may restrict such mutational access. However, because these studies focus on evolved genotypes and local mutational neighborhoods, they cannot determine whether this local constraint limits mutational adaptability under environmental change. Such adaptability depends on a genotype's position relative to high-fitness regions for other environments. Addressing this question requires reconstructing the full probability distribution over phenotypes for every genotype and the resulting environment-specific fitness landscapes across genotype space. Such reconstruction is generally infeasible because genotype and phenotype spaces grow combinatorially. Here, an abstract model of
stochastic genotype-phenotype mapping, inspired by interacting
spins in statistical physics, permits exhaustive reconstruction of the map. We find that high-penetrance genotypes tend to occupy the interior of environment-specific high-fitness regions and are mutationally robust, whereas lower-penetrance genotypes tend to lie near their boundaries and have greater mutational access to high-fitness regions for alternative environments. This global geometry generates a trade-off between penetrance and mutational adaptability. In evolutionary simulations, stronger phenotypic noise in a fixed environment increases the selective advantage of reliable expression, thereby favoring high penetrance and mutational robustness. Frequent environmental change instead favors mutational accessibility at the expense of penetrance. Thus, penetrance and adaptability are opposing consequences of the same global geometry, with environmental conditions determining their evolutionary balance.
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Solar and Stellar Astrophysics
Improving the Physical Interpretability of Gaussian Processes in Stellar Activity Modeling: A Study Case on Photometric Variability Among Stellar Clusters
Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty et al. (+12 more)
Gaussian Processes (GPs) are widely used to model
stellar variability in photometric surveys, but a statistically successful fit does not guarantee that the inferred hyperparameters correspond to physically meaningful
stellar properties. This is especially important for young, active
stars, whose TESS light curves contain evolving spots, harmonics, and non-sinusoidal variability. We use
stellar rotation as a case study to examine when the period hyperparameter of a quasi-periodic GP can be interpreted as a physical rotation period. We introduce a regularized GP likelihood that reweights the covariance-complexity term in the marginal likelihood, reducing the tendency of unconstrained models to converge toward preferred but misleading solutions. We test this framework on 539
stars in IC2602, the Tucana-Horologium Association, Pisces-Eridanus, and GroupX, with independently reported and manually vetted rotation periods. This
benchmark evaluates GP hyperparameter interpretability and automated period recovery with minimal human intervention. We compare regularized and unregularized models across several regularization strengths, {\lambda}, using literature agreement, sector-level diagnostics, and consistency across TESS sectors. Relative to the standard GP likelihood, regularization improves successful rotation-period recovery by an average of 7%. It also generally reduces the median absolute fractional deviation of periods across sectors, showing that the improvement is not limited to catastrophic failures but also mitigates smaller systematic errors. Regularization is particularly beneficial for non-sinusoidal or evolving modulation, where unconstrained GPs may recover harmonics or spurious timescales. These results show that likelihood regularization and cross-sector consistency are practical diagnostics for assessing when GP-based rotation periods are robust.
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All authors Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty, Mark Popinchalk, Jason Lee Curtis, Johanna M. Vos, Alexandrine L'Heureux, Andrew Ayala, Eleanor Johnson, Dawn McCullough, Nicole Munoz, Hannah Park, Xue Weng, Livia Poliquin, Ilhem Lazizi
Mesoscale and Nanoscale Physics
Hierarchical Quantum Transport from Coupled Topological Domain-Wall States in SSH Chains
Alessio Palavicini, César G. Galván and Carlos Ramírez
We investigate the transport properties of Su-Schrieffer-Heeger (SSH) chains containing multiple topological domain walls and show that their interaction generates a hierarchy of emergent spectral structures. Each domain wall contributes a localized state inside the SSH gap, and the hybridization of these states produces minibands whose signatures are directly reflected in the transmission spectra. By combining domain-wall
lattices with different domain-wall separations, we construct effective SSH structures within the miniband subspace. The resulting transmission spectra reproduce the characteristic features of conventional SSH chains, including gap formation, finite-size resonances, and the correspondence between transmission spectra and band structure. The construction can be applied recursively, generating successive generations of effective SSH structures. As a consequence, effective SSH spectra repeatedly emerge within progressively narrower energy intervals, producing a self-similar hierarchy of minibands and spectral gaps. To understand the origin of this hierarchy, we develop an effective renormalized description based on successive decimation. The effective parameters exhibit a hierarchy of interlaced singularities whose number increases at each iteration. These singularities partition the energy axis into progressively finer intervals and provide a natural interpretation of the repeated fragmentation of the spectrum. Our results show that topological domain-wall states can act as emergent degrees of freedom from which multiscale transport channels, effective couplings, and hierarchical spectral structures may be engineered. More generally, the framework introduced here establishes a connection between recursive topological constructions, effective
Hamiltonians, and the emergence of self-similar spectra in one-dimensional systems.
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Applied Physics
Imaging atomic scale stochasticity: noise in the nearly commensurate charge density wave of 1T-TaS$_2$ for leaky-integrator-and-fire neuromorphic emulator
Michael Verhage
Low-dimensional materials are promising materials for emulating
neuron-like firing were understanding of the atomic-scale origin of this behavior can benefit integration into neurormophic hardware. Using scanning tunneling microscopy (STM) as a highly local probe of correlations in the charge density wave (CDW), we study atomic-scale CDW noise in $1T\text{-}\mathrm{TaS}_2$ at room temperature. We statistically analyze the tunnel-junction noise and, to explain the temporally correlated current bursts, introduce a mesoscopic model in which the fractal structure and reorganization of CDW discommensurations are related. This noise mimics leaky-integrate-and-fire
neuron dynamics. Our results show that atomic-scale current bursts in the tunnel junction can act as effective nonlinear elements in spiking neural emulators, enabling bioinspired processing through rich CDW dynamics at room temperature and supporting the miniaturization of spiking devices.
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Chemical Physics
Collective intermolecular Coulombic decay beyond Coulomb
Alan G. Falkowski and Lorenz S. Cederbaum
Intermolecular Coulombic decay (ICD) is a widely spread phenomenon in nature and laboratory in which the excess energy of a donor is utilized to ionize a nearby acceptor. If the excess energy is insufficiently large to enable ICD, two (or more) donors can collectively transfer their combined excess energy to ionize the acceptor. Experiments show that this collective ICD is, surprisingly, operative in gases. Recently, it has been demonstrated that standard ICD can efficiently take place at large distances between the donors and acceptors due to retardation. Here, we derive the theory of collective ICD including retardation.
Quantum electrodynamics (QED) perturbation theory is used and it is shown that the theory can be substantially simplified and the process also made more amenable to interpretation by introducing two-body interaction potentials which include retardation. Explicit formulas for the rate of collective ICD are derived and interpreted by expressing the rate in terms of measurable quantities and
geometric factors. It is demonstrated that the change of the permanent dipole moments of the species upon excitation is a relevant ingredient in collective ICD.
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General Relativity and Quantum Cosmology
Unsupervised Deep Learning Method for Clustering KAGRA O3GK Transient Noise Data
Yubin Kim, Kihyun Jung and Kyujin Kwak
The advent of ground-based gravitational wave detectors has significantly improved the detection of faint gravitational wave signals. However, these detectors are affected by various types of transient noise, known as glitches, which can mimic true gravitational wave signals and limit detector sensitivity. Classifying glitches according to their time-frequency characteristics not only facilitates a deeper understanding of their origins, but also supports their mitigation on data to maintain data quality. While supervised machine learning methods are commonly employed for glitch classification, they require the labelling of training
datasets obtained through manual annotation, a process which is costly and not scalable for evolving detectors. In order to address this challenge, the present study investigates unsupervised deep learning methods for dimensionality reduction and clustering of glitch spectrogram images. In this study, three distinct approaches are applied and compared using data from the KAGRA detector's O3GK run. The findings of this study demonstrate that deep learning-based feature extraction significantly enhances the clustering performance compared to traditional machine learning methods. This study presents an initial analysis of the KAGRA glitch
dataset using unsupervised deep learning, highlighting the potential of this approach for efficient and scalable glitch classification in future observation runs.
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Soft Condensed Matter
Jerky Motion of Active Granular Particles
Alexander P. Antonov, Marco Musacchio, Hartmut Löwen et al. (+1 more)
Abrupt transitions between rest and motion can render the standard Newtonian description – based on position, velocity, and acceleration – incomplete, requiring higher-order derivatives such as the jerk, the third time derivative of position. Here, we show that the interplay between activity and dry friction gives rise to robust jerk-dominated dynamics in self-propelled particles: the particle speed increases quadratically with time under an active force, in contrast to the linear growth expected for conventional Newtonian dynamics. We demonstrate this behavior analytically, numerically, and experimentally using active vibrobots self-propelling on a vertically vibrating plate at low vibration amplitudes, where surface asperities generate dry friction and, thus, give rise to jerky motion when combined with activity. Our results establish dry friction as a simple mechanism for realizing higher-order dynamics in active matter and suggest that jerky dynamics may arise broadly in nonequilibrium systems with frictional contacts.
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All authors Alexander P. Antonov, Marco Musacchio, Hartmut Löwen, Lorenzo Caprini
Mesoscale and Nanoscale Physics
Visualizing flat-band spatial renormalization in rhombohedral graphene superlattices
Peng-Cheng Pan, Shihao Zhang, Yang Zhang et al. (+10 more)
Rhombohedral
graphene/hBN moiré superlattices exhibit flat-band-driven emergent phases, including superconductivity and the fractional
quantum anomalous
Hall effect (FQAHE), yet the microscopic role of the moiré potential remains unclear. Here, using scanning tunneling microscopy, we visualize moiré-modulated spatial renormalization of flat bands in rhombohedral pentalayer and tetralayer
graphene/hBN superlattices. We observe spatially hierarchical filling, manifested as periodic energy shifts of the flat bands at the moiré scale, leading to spatial reshaping of correlated states in the interacting regime. Remarkably, this modulation vanishes below a ~10 nm moiré period–the same threshold below which the FQAHE is absent. Theoretical modeling attributes this mechanism to atomic-corrugation-induced charge redistribution. Our work provides real-space visualization of moiré-engineered flat-band reconstruction, resolving a key link between moiré periodic potential and emergent topological order.
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All authors Peng-Cheng Pan, Shihao Zhang, Yang Zhang, Ji Huang, Ling-Hui Tong, Chen-Chen Xu, Yuan Tian, Li Zhang, Lijie Zhang, Yuanyuan Hu, Wen-Xiao Wang, Zhihui Qin, Long-Jing Yin
Cosmology and Nongalactic Astrophysics
Chebyshev interpolation in Einstein-Boltzmann codes
Herman Sletmoen
Einstein-Boltzmann codes compute theoretical predictions of cosmological models and rely heavily on interpolation in their independent variables: time $\tau$, wavenumber $k$ and multipole $\ell$. We give a practical summary of interpolation with Chebyshev
polynomials, which converges rapidly for smooth functions and thus pairs naturally with approximation-free Einstein-Boltzmann codes. By solving the perturbations and line-of-sight integrals at Chebyshev nodes in $k$ and $\ell$, we show that Chebyshev
polynomials interpolate to higher precision than traditional cubic splines from fewer explicit solutions. On a set of example spectra for matter and the
cosmic microwave background (CMB), we find up to four orders of magnitude lower interpolation error using the same number of points. For a typical CMB temperature spectrum computed with interpolation in both $k$ and $\ell$, Chebyshev
polynomials converge to $10^{-4}$-$10^{-5}$ relative error with only 50-80 points per variable, while cubic splines approach $10^{-4}$ error with 200 points, translating to a $2.5\times$-$4\times$ speedup. The exact improvement depends on the target function and is generally more dramatic at high precision levels. Standard Chebyshev $\ell$-interpolation needs line-of-sight integrals generalized to non-integer $\ell$, but we show a way to avoid this by rounding the nodes to integers. Chebyshev interpolation is implemented in SymBoltz, which is available at https://github.com/hersle/SymBoltz.jl.
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Materials Science
Thermal diffuse scattering in TEM: complex absorptive potentials compared to the frozen phonon model
Martin Hájek and Ján Rusz
In transmission electron microscopy, electrons undergo inelastic scattering primarily through
phonon excitations, known as thermal diffuse scattering. To capture the inelastic scattering effects on the elastic scattering components, absorptive effects must be included in the modeling of electron propagation, accounting for the gradual depletion of the elastic channel of the electron beam. Several approaches to modeling this absorption exist. In this paper, we compare the widely used complex absorptive potentials method to the more elaborate frozen
phonon model, based on correlated atomic motion and on the Einstein model of atomic motion.
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Astrophysics of Galaxies
Spatially resolved molecular gas conditions in the circumnuclear disc of 3C 84
Bin Jia, Tom Oosterloo, Serena Viti et al. (+1 more)
The brightest cluster
galaxy NGC 1275, at the centre of the Perseus cluster, hosts the
radio-loud AGN 3C 84 and a circumnuclear disc (CND) of cold molecular gas onto which large-scale CO filaments accrete, yet the physical and chemical conditions of the gas in the CND remain poorly constrained. We present a spatially resolved analysis of ALMA CO(2-1), HCN(3-2), and HCO$^+$(3-2) observations at 72 pc. The data are partitioned into beam-sized hexagonal regions and modelled with a
Bayesian framework that couples a neural network emulator of time-dependent chemistry (UCLCHEM) with non-LTE radiative transfer (SpectralRadex) to infer the gas density, kinetic temperature, and
cosmic ray ionisation rate in each region. All three line ratios peak in the inner disc and decline with radius. The inference shows radial gradients in density ($\log_{10} n({\rm H_2}) \approx 6.3$ to $\sim 5$), kinetic temperature (~200 K to ~160 K), and
cosmic ray ionisation rate ($\log_{10}(\zeta/\zeta_0) \approx 4.9$ to $\sim 3$). Despite the powerful
radio AGN, the observed HCN(3-2)/HCO$^+$(3-2) ratio remains $\lesssim 1$ across the disc. Our modelling attributes this to optical depth saturation of HCN(3-2) ($\tau \sim 1$-3), which suppresses the intensity ratio even when the HCN abundance exceeds that of HCO$^+$ by a factor of three or more. The HCN/HCO$^+$ intensity ratio therefore cannot be used as an abundance diagnostic without accounting for optical depth, and a low ratio does not necessarily imply weak AGN influence on the chemistry. Azimuthally resolved profiles suggest a localised HCO$^+$/CO enhancement at the western disc boundary, coinciding with the filament-disc
accretion interface and consistent with shock processing by velocity shear between the infalling filaments and the rotating disc. These results indicate that the CND is shaped by
accretion from its filamentary environment.
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All authors Bin Jia, Tom Oosterloo, Serena Viti, Raffaella Morganti
High Energy Physics (Phenomenology)
Electron and Muon $g-2$ Constraints on Light Vector Bosons: Dark Photons and the $X_{17}$ Boson
Raoul Serao and Antonio Capolupo
We combine the current experimental
muon $g-2$ world average, which incorporates the final Fermilab result, with the latest electron $g-2$ determinations based on cesium and rubidium measurements to set 95% CL exclusion contours for a pure vector mediator coupled to
leptons. We explicitly test the assumption that the electron and
muon coupling magnitudes are equal by comparing this restricted case with the case of independent electron and
muon couplings and quantify the impact on the allowed parameter space. In the minimal visible dark-
photon model, both
leptons constrain the same kinetic mixing and are analyzed through a combined $\chi^2$ analysis. We compare the resulting $g-2$ bounds with existing accelerator direct-search exclusions and model-dependent astrophysical and cosmological constraints. From the accelerator comparison, we identify a region in the $(m_{A'},|\epsilon|)$ parameter space near $17$~MeV, close to the reported $X_{17}$ mass, that remains allowed by the direct-search contours displayed here but is excluded by the cesium-based electron $g-2$ constraint. The rubidium-based fit does not exclude this interval. For an $X_{17}$
boson with independent
lepton couplings, we constrain the electron and
muon couplings separately. Electron-only direct searches leave two disconnected allowed regions near the reported $X_{17}$ mass: a newly reopened low-coupling interval and a higher-coupling region above the NA64 excluded band. The cesium-based electron $g-2$ constraint closes the higher-coupling region, while the rubidium-based constraint reduces its extent; neither affects the newly reopened low-coupling interval. Using the current experimental
muon $g-2$ world average, we obtain a new $g-2$-based exclusion region for the
muon coupling, with no significant preference for a nonzero coupling.
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General Relativity and Quantum Cosmology
Testing $f(Q)$ Gravity with DESI DR2 and Strong-Lensing Time Delays
Darshan Kumar, Saibal Ray, Fengge Zhang et al. (+3 more)
Symmetric teleparallel
gravity provides an alternative description of gravitation in which non-metricity replaces
curvature and torsion. Its extension through $f(Q)$
gravity offers a different
geometric description of the late-time expansion of the Universe and its accelerated phase. In this work, we investigate two $f(Q)$ models, a normalized power-law model and a square-root exponential model, and test their ability to describe the late-time expansion history. We constrain the model parameters through Markov chain Monte Carlo analyses using
Cosmic Chronometer measurements, DESI DR2
baryon acoustic oscillations, strong-
lensing time-delay observations, and three Type Ia
supernova compilations, Pantheon$^+$, Union 3.0, and DES Y5. We compare both models with the flat $\Lambda$CDM model using the minimum $\chi^2$, Akaike information criterion, and
Bayesian information criterion. The square-root exponential model provides a better statistical fit than $\Lambda$CDM for the combinations of
Cosmic Chronometer, DESI DR2, and strong-
lensing time-delay data with Pantheon$^+$ and Union 3.0, with improvements in both the goodness of fit and information criteria. The normalized power-law model remains statistically competitive with $\Lambda$CDM for the
supernova-inclusive combinations, although the information criteria do not favor its additional parameter. We also determine the transition
redshift from
cosmic deceleration to acceleration for both models, obtaining consistent values across the different
dataset combinations. The transition
redshifts agree with observational estimates of the
cosmic acceleration epoch. Overall, our results support $f(Q)$
gravity as a viable alternative to $\Lambda$CDM for explaining the late-time accelerated expansion of the Universe without requiring a cosmological constant.
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All authors Darshan Kumar, Saibal Ray, Fengge Zhang, Nisha Rani, Praveen Kumar Dhankar, Jie Zheng
Quantum Physics
Scalable Lindblad Noise Learning via Stochastic Tensor-Network Simulation
Alejandro R. Ramos Ramos, Maximilian Fröhlich, Aaron Sander et al. (+4 more)
Learning dissipation rates in large-scale open
quantum systems is a major obstacle for near-term
quantum technologies, as existing Lindblad estimation methods are typically limited to small system sizes due to the computational complexity of repeatedly solving the Lindblad equation during optimization. Here, we propose a scalable noise-learning framework for Lindblad dissipation rates that combines a
stochastic simulation method, the Tensor Jump Method (TJM), with gradient-free optimization of a least-squares cost-function defined on time series of local-observable expectation values. We demonstrate the approach on two noise models in the Ising model: a site-resolved (local) model, in which independent dissipation rates are learned for each site up to $N_{\mathrm{site}}=16$, and a spatially homogeneous (global) model with only seven parameters, scaled to $N_{\mathrm{site}}=160$ sites.We complement these numerical results with a series of exact, provable guarantees: the Frobenius variance of the TJM density-
matrix estimator is shown to equal $(1-\mathrm{Tr}[\rho^2])/N_{\mathrm{traj}}$, an exact purity-based characterization of the
stochastic estimation error; the corresponding purity
evolution is proven to be monotonically non-increasing for Hermitian jump operators; and, under a finite covariance distance assumption, the standard deviation of the cost-function is shown to decrease with system size, so that fewer trajectories are needed to reach a fixed target accuracy as the system grows. Together, this combination of scalable numerics and rigorous theoretical guarantees positions TJM-based noise learning as a practical foundation for characterizing dissipation in large
quantum devices and for guiding future work on error mitigation and
quantum error correction.
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All authors Alejandro R. Ramos Ramos, Maximilian Fröhlich, Aaron Sander, Robert Wille, Martin Eigel, Patrick Gelß, Sebastian Pokutta
General Relativity and Quantum Cosmology
Inhomogeneous Cosmologies with Bumpy Structure from Superfluid Pionic Vortices and the propagation of electromagnetic field
Fabrizio Canfora, Alex Giacomini, Nikolaos Dimakis et al. (+1 more)
In this work we introduce exact cosmological solutions in General Relativity in (3+1) dimensions which take into account both the usual fluid component as well as a superfluid component describing superfluid Pionic
vortices. Such superfluid
vortices are source of inhomogeneities which can be treated exactly, no perturbation theory is required. These analytic solutions are relevant to obtain a non-perturbative description of inhomogeneities in cosmology. We discuss the peculiar effects of these hadronic inhomogeneities on the propagation of electromagnetic fields on such cosmological backgrounds analyzing possible observable effects. Finally, the properties that the effective superfluid satisfy for such solutions to exist are discussed, together with possible extensions of this family of solutions.
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All authors Fabrizio Canfora, Alex Giacomini, Nikolaos Dimakis, Andronikos Paliathanasis
Mesoscale and Nanoscale Physics
Exciton fine structure in nanocrystals: effect of cuboidal and spheroidal shapes
M. A. Semina, O. O. Druzhinina, A. A. Golovatentko et al. (+1 more)
We present the theory of the band-edge
exciton fine structure in nanocrystals (NCs) with spheroidal and cuboidal shapes. The effects of the cubic
symmetry of the
crystal lattice, the cubic shape of the NC, and NC uniaxial anisotropy on the hole energy states and electron-hole exchange interactions are considered non-perturbatively.
Symmetry analysis yields an effective
Hamiltonian for the
exciton fine structure, parameterized by one constant for hole energy splitting and five independent constants for exchange interaction. Numerical calculations reveal that in uniaxially anisotropic zinc-blende NCs, the sign of the hole ground state splitting depends on the material parameters and on the orientation of the anisotropy axis relative to the crystallographic axes. Beyond the conventional bulk cubically-symmetric contribution to the exchange interaction, which originates from Bloch-function
symmetry and is typically negligible, in nanocrystals, we identify the contribution arising from the cubic
symmetry of the envelope wavefunction. This cubically symmetric envelope-induced short-range exchange is non-negligible in cuboidal NCs and induces a pronounced splitting of the dark
exciton states. We further analyze the influence of uniaxial anisotropy of the exchange constants on both the
exciton fine structure and the oscillator strength. Special
attention is paid to NCs, where the anisotropy of the exchange constants is comparable to a relatively small hole energy anisotropic splitting.
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All authors M. A. Semina, O. O. Druzhinina, A. A. Golovatentko, A. V. Rodina
Instrumentation and Methods for Astrophysics
NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II
Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer et al. (+21 more)
NIRC2, the Near Infrared Camera 2 on the Keck II
telescope, was recently upgraded with a new suite of polarimetric observing modes. The new polarimetry modes (referred to as NIRC2-Pol) open up a wide range of new studies, including investigations of
exoplanets, the
Galactic center, active
galactic nuclei, and
solar system objects. The new modes enabled by the upgrade span the 1.1 to 4.1 micron range (i.e. J through L' bands) and include imaging polarimetry, coronagraphic imaging polarimetry, and spectropolarimetry. NIRC2-Pol is unique, as Keck II is the largest
telescope (10 m) on which AO-fed infrared polarimetry capabilities are available, one of few with L' polarimetric imaging, and the only one where there is both a polarimetric mode and a
vortex coronagraph. Here, we introduce the design of NIRC2-Pol, its capabilities, and its current operational status. We also present its first on-sky results: the first L' polarimetric images of the AB Aurigae circumstellar disk. These images more clearly reveal the disk's iconic spiral arms than previous L' total intensity imaging.
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All authors Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse, Charles-Antoine Claveau, Greg Doppmann, Michael P. Fitzgerald, Matthew Freeman, Trisha Hammen, Ryan Hersey, Nemanja Jovanovic, Scott Lilley, Jessica Lu, James E. Lyke, Keith Matthews, Dimitri Mawet, William Melby, Thomas McIntosh, Max Service, Jacob Taylor
Chemical Physics
Efficient, precise DFT calculations of NMR shieldings: Revisiting the finite field approach
Xiao Liu, Kaushik D. Nanda, Jiashu Liang et al. (+1 more)
Absolute
nuclear magnetic shielding constants and relative chemical shifts are second-derivative response properties that underpin the interpretation of
Nuclear Magnetic Resonance (NMR) spectra and provide critical insights into the structural and electronic environments of diverse chemical systems. However, their accurate computation is often constrained by the need for method-specific, analytical response implementation, and therefore is particularly challenging for non-variational, correlated wavefunction methods where analytical second derivatives are frequently unavailable. Here we present a scalable framework that computes NMR shielding tensors through finite
magnetic field differentiation of complex-valued, gauge-including atomic-orbital (GIAO) based self-consistent field (SCF) calculations. By combining hybrid MPI and OpenMP parallelization and resolution-of-identity (RI) approximation-based Coulomb (J) and Exchange (K) implementation and mixed numerical/analytical derivatives computational scheme, we achieve very good efficiency for hybrid density functional theory (DFT) NMR shielding, relative to existing state-of-the-art analytic implementations across realistic chemical systems of various sizes. Forward differentiation with optimal step sizes derived from rigorous error analysis retains favorable numerical errors much smaller than experimental uncertainty or intrinsic DFT errors. The results demonstrate that RI-accelerated finite
magnetic field calculations can obtain DFT-level NMR shielding constants very precisely, providing a scalable foundation for extensions to more advanced
quantum chemistry methods in future work.
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All authors Xiao Liu, Kaushik D. Nanda, Jiashu Liang, Martin Head-Gordon
Atmospheric and Oceanic Physics
AICON: An operational global machine learning weather forecasting model
Tobias Goecke, Marek Jacob, Florian Prill et al. (+9 more)
We introduce AICON, a global machine learning weather prediction (MLWP) model which generates forecasts at 13 km spatial resolution with a 3-hour time step, trained on the high-resolution, non-hydrostatic ICON-DREAM
dataset. AICON is in full operational use at Deutscher Wetterdienst since 2nd of March 2026. The model employs a graph neural network (GNN) architecture with an encoder-processor-decoder structure, where node updates are performed using a graph
attention mechanism. A key feature of AICON is its use of an icosahedral multi-mesh derived from the native grid of the ICON model, ensuring consistency with the training data. ICON's terrain-following vertical SLEVE coordinate is one of the major distinctions from existing emulators. AICON's training strategy prioritizes small-scale fidelity by avoiding autoregressive multi-step rollout and longer forecast horizons during training, a design choice motivated by the hypothesis that this approach preserves fine-scale features often damped in models optimized for longer-range forecasts. We describe the prognostic and diagnostic variables used for training, the transfer learning protocol employed to accelerate convergence, and the model's performance across a range of evaluation metrics. An extensive evaluation, including routine verification against observation, a tropical cyclone case and spectral analysis reveal the strengths and limitations in the representation of atmospheric variability across scales. Routine verification against observations demonstrates competitive skill relative to the operational ICON model, particularly for near-surface variables in the short to medium forecast range.
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All authors Tobias Goecke, Marek Jacob, Florian Prill, Michael Denhard, Felix Fundel, Jan Keller, Roland Potthast, Hendrik Reich, Britta Seegebrecht, Sven Ulbrich, Arianna Valmassoi, Sabrina Wahl
Quantum Physics · Cross-listed from math.OA
Non-Subhomogeneity of Minimal Operator Systems over Positive Semidefinite and Lorentz Cones
Tim Netzer
The minimal operator systems over ${\rm Mat}_k(\mathbb C)_+$, $k\geqslant2$, and the Lorentz cones $\mathcal L_m$, $m\geqslant4$, are not subhomogeneous. For the $2\times2$ cone we construct extreme positive maps of arbitrarily large output dimension. Positive retracts give the remaining cases. Equivalently, for fixed $k\geqslant2$ and $d$, there exist $s>d$ and an entangled positive operator on $\mathbb C^k\otimes\mathbb C^s$ such that every compression of the second factor to $\mathbb C^d$ is separable.
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Mathematical Physics · Cross-listed from math.AP
On a bulk-surface Navier-Stokes-Cahn-Hilliard model: Existence of weak solutions and asymptotic limits
Jonas Stange
We study a thermodynamically consistent bulk-surface Navier–Stokes–Cahn–Hilliard system describing two-phase flows exhibiting moving contact lines, variable contact angles, and mass transfer. We establish the existence of global weak solutions for non-degenerate mobility functions and singular free-energy potentials. The proof is based on an implicit time-discretization scheme and a subdifferential characterization of the convex part of the bulk-surface free energy. Finally, we study the simultaneous high-friction and decoupling limit, and prove that corresponding weak solutions converge, up to a subsequence, to a weak solution of the Abels–Garcke–Grün model. One key ingredient of the proof is the Mosco convergence of the convex part of the bulk-surface free energy, which might be of independent interest.
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General Relativity and Quantum Cosmology
Global uniqueness of Kerr black hole spin and inclination from a segment of the critical curve
Kenta Hioki
High-resolution observations are expected to probe the
photon-ring structure of black hole images. The critical curve is the geometrically defined limiting locus on the observer's screen toward which successive higher-order
photon subrings accumulate. For a Kerr black hole, the shape of this limiting curve depends on the dimensionless
spin parameter $a$ and the inclination angle $i$. We investigate whether these parameters can be determined uniquely from a connected positive-length segment of the critical curve when the segment's position and orientation on the screen are unknown. For rotating non-extremal Kerr black holes with $0<a<1$ and $0<i\leq\pi/2$, we prove global uniqueness: if two such segments coincide as point sets after orientation-preserving rigid motions of the screen, then their Kerr parameter pairs coincide and the two rigid motions are identical. The proof uses an irreducible implicit
polynomial to show that a segment determines the full algebraic curve containing it and then recovers the parameter pair $(a,i)$ from rigid-motion invariants of that
polynomial.
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Optics
Ultrafast tuning of the focusing efficiency of a nonlinear atomically thin lens
Rahil Rezwan, Bernardo Dias, Tom Hoekstra et al. (+10 more)
Control over light focusing is paramount for optical and imaging systems. However, its implementation in active and integrated nanophotonic devices is hindered by the bulky and static nature of standard lenses. Here, we show that Fresnel Zone Plate Lenses (FZPL) based on a monolayer Transitional Metal Dichalcogenide are a viable solution to the challenges of miniaturization, integration, and active control of the focusing efficiency, featuring both ultrafast and large modulation depth. Using a monolayer $WSe_2$ FZPL, we demonstrate all-optical ultrafast ($\sim$ ps) modulation of the focusing efficiency close to $\sim$30%, that we achieve by exploiting the nonlinear
exciton-resonant enhancement and modulation of second harmonic generation.
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All authors Rahil Rezwan, Bernardo Dias, Tom Hoekstra, Mehmet At{\i}f Durmuş, Bauke van der Vorm, Till Weickhardt, Omid Ghaebi, Zhuoyuan Lu, Devapriyo Mithun, Carsten Ronning, Yuerui Lu, Jorik van de Groep, Giancarlo Soavi
Quantum Physics
When Similarity Is Interaction-Driven: Quantum Kernels for Regime-Sensitive Learning
Hanqiu Peng, Jianlong Lu and Ying Chen
Similarity in many decision systems is governed not by distance alone but by interactions among variables. In fraud and anomaly detection, small local perturbations can cross interaction-sensitive decision boundaries while leaving ambient distance almost unchanged. Motivated by this setting, we introduce a thin-slab interaction model and an interaction-driven
quantum kernel constructed from entangled Pauli-string feature maps. The feature map explicitly encodes sparse high-order block interactions. We show that the resulting fidelity kernel is positive semidefinite, admits an exact block-factorized formulation, and induces a geometry sensitive to changes in interaction regime. Across balanced and imbalanced synthetic experiments spanning third-, fourth-, sixth-, and eighth-order interactions, the proposed kernel consistently outperforms linear, radial basis function,
Laplacian, and
polynomial kernels, as well as an engineered-interaction linear baseline supplied with the planted block products. On real fraud-detection
benchmarks, it achieves the highest mean accuracy and F1 on Credit Card Fraud Detection and ranks second on IEEE-CIS Fraud Detection. Executed on a 156-
qubit IBM
Quantum processor in a fourth-order setting, the hardware-estimated kernel matches the noise-free simulator within seed-to-seed variability and retains its advantage over the baselines. These findings show that
quantum-kernel performance depends on
alignment between feature-map geometry and the underlying predictive structure, rather than on
Hilbert-space dimension alone. Because the prescribed block-factorized kernel can also be evaluated exactly on a classical computer, the results establish predictive and representational value rather than computational
quantum speedup.
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Mesoscale and Nanoscale Physics
Long-Range Order and Composite Boson Condensation in Lattice Quantum Hall States
Fabian J. Pauw, Nathan Goldman and Felix A. Palm
Topological states of matter, such as
quantum Hall states, are characterized by the absence of local order parameters. In the continuum, their topological order has been reinterpreted as the condensation of nonlocal composite
bosons, but this condensation and the resulting long-range correlations have so far eluded direct confirmation beyond the simplest trial states. Here, we apply tensor-network methods to
lattice Hamiltonians hosting
quantum Hall states, revealing this exotic order directly in interacting ground states and demonstrating both the long-range correlations and the condensation of composite
bosons. These correlations define a nonlocal order parameter that identifies phase transitions between trivial and topological phases, for both bosonic and fermionic models. The corresponding operators are accessible through site-resolved, local measurements on an extensive number of particles, making them directly probable in
quantum simulators. Our work opens new avenues for microscopic studies of topological
quantum matter beyond the reach of traditional solid-state approaches.
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Statistical Mechanics
Ideal Bose-Einstein condensation in the canonical ensemble: exact asymptotic estimates from large deviations
Giacomo Gradenigo, Dario Lucente and Luca Salasnich
In this work we present a large-deviations approach to the calculation of the canonical partition function for free
bosons. Three-dimensional Bose-Einstein condensation is studied in the fixed-density ensemble as a function of the dimensionless density $\varrho = \rho \lambda_T^3$, with $\rho=N/L^3$ the standard particle density, $\lambda_T$ the thermal wavelength, $L$ the linear size of the box and $N$ the total number of particles. A large-deviations approach in terms of the dimensionless parameter $\ell=L/\lambda_T$ allows us to provide exact asymptotic estimates of the canonical partition function both above and below the critical density $\varrho_c$ for Bose-Einstein condensation. We show how this approach allows to explicitly account for finite-size effects and how it fully captures the first-order aspects of the transition, allowing us to explicitate its driving mechanism in terms of the competing probabilities of normal and condensed phases. The proposed large-deviations approach allows then to obtain in all regimes explicit and simple analytical expressions, at the leading order in the large parameter $\ell$, for both the average fraction of particles in the ground state, the condensate fraction $\langle n_0(\varrho) \rangle = \langle N_0(\varrho) \rangle/N$, and for its fluctuations, $\sigma_0(\varrho) = \sqrt{\langle N_0^2(\varrho)\rangle - \langle N_0(\varrho)\rangle^2}/N$, retrieving for instance the anomalous scaling $\sigma_0(\varrho)\sim 1/V^{1/3}$ in the condensed regime, $\varrho > \varrho_c$. Our large-deviations asymptotic estimate, by analytically clarifying the mixed-order nature of Bose-Einstein condensation, allows then to reveal the similarity between this transition and other mixed-order transitions, as for instance the localization transition in the Discrete Non-Linear Schrödinger Equation.
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Mesoscale and Nanoscale Physics
Yuanchen Chi, Dongxu Di, Michael Fralaide et al. (+2 more)
Interfacial charge transfer provides an effective route for tailoring the optical and electronic properties of two-dimensional materials. Here, we investigate infrared surface plasmon polaritons in
oxide/
graphene heterostructures using scattering-type scanning near-field optical microscopy. Ultrathin
oxide overlayers deposited by physical vapor deposition enable systematic engineering of
graphene plasmons through interfacial charge redistribution. MoOx strongly enhances the plasmonic response, producing a longer plasmon wavelength, stronger fringe contrast, and reduced damping, whereas a subsequently deposited ZnOx overlayer partially reverses these changes. Energy-dependent nano-infrared imaging combined with quantitative modeling reveals an increased
graphene carrier density and the resulting modification of the plasmon dispersion. Thickness-dependent measurements show a rapid increase in charge-transfer doping at sub-nanometer MoOx thicknesses, followed by a weaker long-range contribution at larger overlayer thicknesses. Electrostatic gating further modulates the carrier density and produces a nonlinear response consistent with gate-dependent interfacial charge redistribution. In addition, an approximately 3-nm-thick MoOx overlayer stabilizes the plasmonic response for at least seven months under ambient conditions. These results establish
oxide/
graphene heterostructures as a robust platform compatible with scalable fabrication, providing a pathway toward stable and tunable infrared nanophotonic and optoelectronic devices.
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All authors Yuanchen Chi, Dongxu Di, Michael Fralaide, Jigang Wang, Zhe Fei