Optics
An Acousto-Optic Colorimeter
Pavel Aksentsev, Georgiy Lobarev, Sergey Korchagin et al. (+2 more)
Uniform color spaces and color-difference formulae rest on visual data obtained almost entirely with surface samples and conventional displays, whose primaries confine the measurements to a limited chromaticity range. The highly saturated region of color space is therefore the least measured part of human color perception, at the moment when
quantum-dot, microLED, and
laser displays have begun to operate inside it. Closing this gap requires stimuli more saturated than any fixed-primary device can produce, together with the stability and uniformity demanded by visual experiments. We present an acousto-optic colorimeter built for this purpose. A four-channel acousto-optic tunable filter selects narrow spectral components from a supercontinuum
laser over the calibrated range of 443–660~nm, with measured linewidths of 1.37–3.20~nm; the wavelength and radiance of every component are set electronically, so the primary set itself becomes an experimental variable. A compact diffuser–light-pipe homogenizer combines the selected components into a uniform observation field, and spectral feedback stabilizes their intensities. The calibrated primary set covered 95% of the area enclosed by the CIE 1964 $10^{\circ}$ spectral locus in the $x,y$ chromaticity plane. The calculated maximum luminance reached 1406~cd\,m$^{-2}$, with 328~cd\,m$^{-2}$ available at the gray Robertson chromaticity. Across an 18-mm observation field the mean spatial $\Delta E_{00}$ difference was 0.913, and five Robertson color centers reproduced under continuous feedback gave mean target errors of 0.34–1.26~$\Delta E_{00}$ over 10-min intervals. The instrument thus delivers calibrated, uniform, and stable highly saturated stimuli, and is intended to extend the empirical basis of color-difference measurement into the region where data are still absent.
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All authors Pavel Aksentsev, Georgiy Lobarev, Sergey Korchagin, Olga Polschikova, Egor Ershov
Quantum Physics
Divisibility of Non-Invertible Quantum Dynamics in the Heisenberg Picture
Federico Settimo and Dariusz Chruściński
We study divisibility of finite-dimensional
quantum dynamics in the Heisenberg picture when the dynamical maps need not be invertible. Heisenberg divisible dynamics determines unique reduced propagators on the accessible operator systems, and Heisenberg CP-divisibility is shown to be equivalent to an operator-norm monotonicity. Although each reduced propagator admits a unital completely positive extension, independently chosen extensions need not satisfy a composition law. Generalized inverses restore this law algebraically, but do not, in general, preserve complete positivity. We characterize the resulting obstruction and give a sufficient construction based on unital completely positive projections onto the accessible operator systems. It is shown that for
qubit dynamics Heisenberg CP-divisibility always guarantees a completely positive generalized-inverse propagator. Finally, we analyze time-local generators at singular times and identify the associated gauge freedom on dynamically inaccessible directions.
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Physics and Society · Cross-listed from q-fin.TR
A Finite Bid–Ask Spread from Replenishment Displaced from the Quote
Christopher Angstmann, Derick Diana and Tim Gebbie
We give a unified analytic account of a finite bid–ask spread in a two-field reaction–
diffusion order book. The model retains separate bid and ask densities in operational time, with
diffusion, cancellation, reaction and external order creation. On the symmetric equal-coefficient branch, the imbalance field determines the reaction price, while the total standing density carries the spread geometry. A
market-making source is introduced by withholding order placement over a finite interval around the reaction boundary, representing round-trip replenishment displaced from the quote. Under a separated, quasistationary and weak-overlap approximation, transport penetrates inward from the placement edges over the cancellation length, giving the quoted spread as the sub-threshold core of the placement-source-free interval.
Market orders remove standing density at the observed quote, whereas replenishment is delivered outside it and must diffuse back across the penetration depth. We derive the resulting delayed and attenuated quote-level response in operational time. On that branch, finite spread and price impact arise from distinct response sectors, while their calendar-time appearance requires a separate observation clock.
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Materials Science
Mechanistic transition between inter- and trans-granular creep cracking via a unified crystal plasticity-fracture framework
Weichen Kong, Yanwei Dai, Yue Wang et al. (+2 more)
High-temperature creep in metals remains challenging due to the complex interplay of deformation and failure mechanisms across multiple length scales. The trade-off between inter- and trans-granular cracking governs the transition of creep rupture behaviour in metallic materials. However, the micromechanical basis of the transition and its linkage to the macroscopic brittle to ductile transition in creep rupture behaviour remain unresolved. Here, the stress-dependent competition between grain-boundary cavitation and slip-induced intragranular cracking is revealed via a unified
crystal plasticity fracture framework. The framework incorporates
crystal plasticity, grain-boundary cavitation, and crystallographic crack propagation within an explicit polycrystalline microstructure. The microscale computation reveals the transition from trans-granular-dominated cracking at high stress levels to mixed inter- and trans-granular cracking at intermediate stresses and inter-granular-dominated cracking at lower stresses, accompanied by distinct damage localization modes and the
evolution of crack paths from grain boundary to grain-interior propagation. The results further quantify the linkage between microscopic fracture mechanisms and macroscopic creep rupture behaviour, including changes in rupture ductility and creep life. Under high-stress conditions, deformation-driven trans-granular damage localization promotes ductile rupture through extensive strain accumulation, whereas under lower-stress conditions, time-dependent grain-boundary damage accumulation leads to quasi-brittle rupture through localized inter-granular fracture.
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All authors Weichen Kong, Yanwei Dai, Yue Wang, Haitao Wang, Yinghua Liu
General Relativity and Quantum Cosmology
Time-Frequency Analysis for LISA: Galactic Foreground Modulation
Sudhi Mathur and Neil J. Cornish
Observations by the
Laser Interferometer Space
Antenna (LISA) will contain time-varying, cyclostationary confusion noise from the
Galaxy, which is naturally handled using time-frequency analysis methods. We present a fast, forward model that maps the parameterized
Galactic gravitational-wave luminosity density onto the annually modulated, unresolved confusion foreground in the complete set of time-delay interferometry channels. The line-of-sight luminosity integral is evaluated on a HEALPix grid and decomposed into spherical harmonics, while the detector response is decomposed analytically, independent of the
Galaxy model, such that a new
Galactic model costs a single map evaluation, transformation, and contraction. We compute the modulated covariance beyond the standard low-frequency limit, expanding the LISA response to second order in finite armlength corrections, and to first order in the unequal-arm corrections. These effects change the normalized modulation curves by up to $\sim\!0.23\%$ and $0.64\%$ for finite armlength corrections at $3$ and $5$ mHz respectively, and by $\sim\!0.074\%$ and $0.71\%$ for unequal-arm corrections in the self and cross channels respectively. Using the fast, forward model and a notional disk-and-bulge
Galaxy model, we construct a Fisher
matrix from the time-dependent channel covariance and forecast that one year of observation constrains the disk scale width and scale height relative to the distance to the
Galactic center at the $8\%$ and $12\%$ levels respectively, and leaves the strongly correlated bulge fraction and bulge radius individually unconstrained.
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High Energy Astrophysical Phenomena
Scalable and sequential inference of the neutron star equation of state with the Einstein Telescope
Thibeau Wouters, Thomas C. K. Ng, Hauke Koehn et al. (+4 more)
Future gravitational-wave observatories such as the Einstein
Telescope will detect tens of thousands of binary
neutron star mergers per year, making gravitational waves a dominant probe of the
neutron-
star equation of state in the coming decades. However, extracting this information requires hierarchical inference across a rapidly growing catalog of events, and existing methods must restart from scratch whenever a new event arrives, making them impractical at this scale. In this Letter, we introduce a hybrid sequential Monte Carlo
algorithm that combines data and likelihood tempering to adaptively update the equation-of-state posterior in batches, reusing previous inference results instead of restarting from a wide prior. Accelerated by GPU hardware, our method infers the equation of state from a simulated month of around 1500 binary
neutron star mergers in a few hours on a single GPU, and we project that a full year of detections could be processed in a few days on current hardware. This establishes sequential Monte Carlo as a practical route for real-time hierarchical inference with future gravitational-wave detectors.
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All authors Thibeau Wouters, Thomas C. K. Ng, Hauke Koehn, Fabian Gittins, Peter T. H. Pang, Tim Dietrich, Chris Van Den Broeck
Physics and Society
Probabilistic neighbors' selection competes with confirmation bias in a bounded confidence model
Chiara Giaquinta, Laura Hernández and David Chavalarias
In this work, we investigate three modified versions of the classic Hegselmann-Krause opinion dynamics model, incorporating features that are typical of many real-world systems, such as uncertainty in the selection of interacting
agents and a weighted evaluation of the relevance of their opinions in the influence function to enhance confirmation bias. Through extensive simulations across different network
topologies, ranging from stylized network models (Barabási-Albert, Erdős-Rényi, and Watts-Strogatz networks) to empirical networks with community structure, we identify the influence of each modification on opinion
evolution and convergence. Our findings reveal that they exert opposite effects on the bounded confidence threshold required for consensus. We further explore an extension based on a data-driven opinion initialization on the empirical networks, where initial opinions are drawn from Gaussian distributions specific to each detected community. While the qualitative effects of the three modified models remain consistent, this new initialization strategy reveals distinct dynamics within the network communities. These insights provide a new and comprehensive perspective on how realistic variations of the Hegselmann-Krause model, in terms of both interaction rules and initial opinion distributions, affect opinion dynamics and shed light on the mechanisms of consensus formation within structured communities.
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Instrumentation and Methods for Astrophysics
Optimizing Laguerre-Gaussian Mode Interferometry in Gravitational-Wave Detectors through Modal Degeneracy Breaking
Liu Tao, Eleonora Capocasa and Matteo Barsuglia
Higher-order Laguerre-Gaussian modes can reduce test-mass thermal noise in gravitational-wave interferometers, but their implementation is limited by degeneracy-induced coupling losses in realistic high-finesse cavities. We mitigate these losses by optimizing the mirror
curvature to break modal degeneracy. We develop a general framework for designing an axisymmetric corrective test-mass surface profile that lifts the degeneracy of the sixth-order Laguerre-Gaussian subspace while preserving an injected donut-shaped $\mathrm{LG}_{0,6}$ mode. Expanded in a
Fourier-Bessel basis, the profile is optimized to maximize the frequency splitting from the nearest unwanted mode while minimizing target-mode loss. For a Virgo-like Fabry-Perot arm cavity, the optimized profile separates the $\mathrm{LG}_{0,6}$ resonance from the nearest same-order resonance, $\mathrm{LG}_{1,4}$, by 2.04% of the free spectral range, reducing unwanted-mode gains below unity at the target-mode resonance and suppressing their resonant enhancement. The profile introduces negligible target-mode loss and improves robustness against astigmatism and realistic mirror surface distortions. Monte Carlo simulations with realistic mirror imperfections yield an average contrast defect of 368 ppm and an average reflected optical loss of 979 ppm, equivalent to a round-trip loss of approximately 3.5 ppm for the modeled cavity. These results substantially improve upon the central anti-reflective mirror mask approach based on selective loss engineering, bringing reflected optical loss within a factor of two of that obtained with the fundamental Gaussian mode under the same simulation conditions. This approach offers a route toward robust donut-shaped Laguerre-Gaussian modes in future precision interferometers with realistic imperfections.
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Statistical Mechanics
Long-Range Nonequilibrium Correlations as a Thermodynamic Speedometer
Vinesh Vijayan, Rishma Thilakaraj, Gokila V et al. (+1 more)
Despite purely local microscopic dynamics, nonequilibrium steady states can develop long-range correlations. We investigate this phenomenon in the boundary-driven symmetric simple exclusion process by relating its exact nonlocal large-deviation functional to finite-time thermodynamic irreversibility under weak time-dependent driving. Decomposing the long-range correlations into hydrodynamic modes, we find that the lag associated with the slowest mode satisfies an upper bound determined by the excess
entropy production rate at each driving frequency. This bound is approached in the quasistatic limit, whereas progressively shorter-wavelength modes do not generally satisfy the corresponding bound. These results provide a quantitative connection between the
curvature of the large-deviation functional, long-range correlations in the nonequilibrium steady state, and finite-time dissipation. Within the linear-response regime considered here, they indicate that the longest-wavelength hydrodynamic mode has a distinct relation between slow relaxation and thermodynamic irreversibility.
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All authors Vinesh Vijayan, Rishma Thilakaraj, Gokila V, Yogeshvari V A
Fluid Dynamics · Cross-listed from math.NA
Learning a generalized Navier-Stokes model beyond the continuum regime
Sihong Shao, Yanli Wang and Zhongwei Xu
Navier-Stokes (NS) equations lose accuracy in the transition regime when the Knudsen number is large, while the Boltzmann equation provides an adequate kinetic description with a substantially higher computational cost. In this work, a data-driven generalized Navier-Stokes (GNS) model is proposed to extend the applicability of the NS equations to the transition regime. A new relationship between the non-
equilibrium variables, such as the stress tensor and the heat flux, and the
equilibrium variables, including the density, macroscopic velocity, and the temperature, together with the Knudsen number, is learned from the data formed by the numerical solution to the Boltzmann equation. The standard end-to-end learning is utilized to construct the loss function, based on which, a long-term end-to-end learning method is proposed for the loss function to reduce accumulated error and improve long-term predictive accuracy. Several numerical examples, including one-dimensional wave and Riemann problems as well as two-dimensional isentropic
vortex and Taylor-Green
vortex problems, are studied to validate the efficiency of this new GNS model.
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Medical Physics
A Multimodal Hyperspectral and Laser Speckle Imaging Platform for Simultaneous Monitoring of Spinal Cord Oxygenation, Perfusion and Metabolism
Junda Wang, Luca Giannoni, Ayse Gertrude Yenicelik et al. (+3 more)
Hyperspectral imaging (HSI) enables spatial mapping of haemoglobin oxygenation and cytochrome-c-oxidase (CCO) redox changes in exposed neural tissue. In this study, we present a technical upgrade of an existing HSI platform by the integration of
laser speckle contrast imaging (LSCI), enabling contemporaneous assessment of oxygenation, oxidative metabolism, relative perfusion and a derived relative oxygen metabolic index in exposed spinal cord in a rat preclinical model. The upgraded system (hNIR+) uses a shared optical path and a single camera to acquire HSI and LSCI images from the same field of view using a sequential acquisition workflow. Hyperspectral images are acquired at 11 discrete wavelengths (600, 630, 665, 784, 800, 818, 835, 851, 868, 881, and 894 nm) to estimate changes in oxygenated haemoglobin (HbO2), deoxygenated haemoglobin (HHb) and oxidized CCO (oxCCO). LSCI is implemented using 632.8-nm coherent illumination to generate relative blood-flow index (rBFI) maps. The LSCI subsystem was validated using a controlled blood-flow phantom, where the LSCI-derived inverse speckle contrast index showed a strong positive linear relationship with pump-controlled flow. The upgraded platform was then evaluated in proof-of-concept observations of the rat spinal cord under normoxia, hypoxia and recovery conditions. Representative
multimodal maps and ROI-based time-course analysis showed clear dynamic responses in HbO2, HHb, oxCCO and rBFI during oxygen challenges that were consistent with the expected physiological responses of the spinal cord during hypoxia, hyperoxia and subsequent recoveries. Overall, these results demonstrate that integrating LSCI into HSI extends the platform to
multimodal and simultaneous monitoring of haemodynamic-metabolic coupling.
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All authors Junda Wang, Luca Giannoni, Ayse Gertrude Yenicelik, Eleni Giama, Frederic Lange, Ilias Tachtsidis
Astrophysics of Galaxies
Chaotic accretion can (still) explain early supermassive black hole growth
Kastytis Zubovas and Matas Tartėnas
The origin of supermassive black holes (SMBHs) is still debated, with hypotheses ranging from massive seeds to super-Eddington growth to chaotic
accretion. Recent discoveries of very high
redshift SMBHs constrain their possible origin and growth scenarios. We investigate whether the chaotic
accretion scenario can explain the most extreme high-
redshift SMBH masses. We predicted the exponential growth timescale of black holes accreting chaotically in a slowly-spinning dark matter
halo, in which uncorrelated gas inflows maintain a low
spin and hence a low radiative efficiency. We compared this prediction against the growth timescales and seed masses implied by a compilation of all known SMBH mass estimates at $z>7$ and against the feeding and feedback conditions expected in such
haloes. We found that in the period $7.6 < z < 10.6$, the most massive SMBHs likely grew very efficiently, with an exponential growth timescale $\tau \sim 32$~Myr, which is consistent with chaotic
accretion predictions provided that growth was almost continuous. All high-
redshift SMBHs with virial mass estimates could have grown from seeds with $M_{\rm seed} \lesssim 100 \, \msun$. We describe the
evolution of the mass reservoir feeding such a black hole, suggesting that wind-driven feedback eventually removes most of the gas and changes the growth mode of black holes at $z \sim 7.5$. We make several predictions regarding the
spins, host-
galaxy correlations, and observable counterparts of high-
redshift SMBHs that distinguish our model from its alternatives. These predictions will be testable in the near future. Chaotic
accretion from
stellar-mass seeds remains a viable origin for the earliest known SMBHs, without invoking massive seeds or super-Eddington growth.
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Quantum Gases
Polaronic Response of a Supersonic Impurity Strongly Coupled to a Bose Condensate
Sooshin Kim, Yoonsoo Kim, Seokmin Jang et al. (+1 more)
How a mobile
impurity exchanges momentum and energy with a many-body environment is a central question in nonequilibrium
quantum physics. This exchange becomes particularly complex when the
impurity moves rapidly and is strongly coupled to its bath. Here, we realize an interaction-tunable cold-atom
collider with fermionic $^{40}$K
impurities immersed in a $^{23}$Na Bose–Einstein condensate. A species-selective Raman pulse simultaneously launches the condensate and quenches the interspecies scattering length, producing an initial relative speed 36 times the condensate speed of sound. We track the ensuing relative motion as the interspecies interaction is tuned from weak coupling to resonance. At weak and intermediate coupling, the
impurity dynamics are well described by a finite-energy two-body collision model. Near resonance, however, the early-time
impurity acceleration is markedly suppressed relative to the two-body prediction, corresponding to a strong enhancement of the apparent dynamical inertia. The enhancement is observed near two distinct Feshbach resonances. These observations provide evidence for a polaronic response in the strongly coupled, supersonic regime of a degenerate Bose–
Fermi mixture.
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All authors Sooshin Kim, Yoonsoo Kim, Seokmin Jang, Jee Woo Park
Materials Science
First principles modeling of group-III acceptors and their potential lifetime-limiting effects in n-type 4H-SiC
José Coutinho
Accurate modeling of p-type dopants in 4H-SiC is essential for understanding the mechanisms governing doping efficiency and carrier transport. In this work, we revisit the electronic structure of boron- and aluminum-related acceptors using hybrid density functional methods. Besides defect formation energies and thermodynamic transition levels, we present a quantitative look into the carrier capture kinetics within the multi-
phonon emission framework. Our results reveal striking differences between the two most relevant p-type dopants. While $\textrm{B}_{\textrm{Si}}$ and $\textrm{B}_{\textrm{C}}$ exhibit nearly identical formation energies, consistent with the occurrence of both defects, the formation energy of $\textrm{Al}_{\textrm{C}}$ under intrinsic conditions is approximately 6.5 eV higher than that of $\textrm{Al}_{\textrm{Si}}$, confirming previous findings that the former is unlikely to occur. We further find that $\textrm{B}_{\textrm{Si}}$ possesses large electron and hole capture cross sections, identifying it as a plausible source of minority-carrier lifetime degradation of n-type material contaminated with boron. In addition, we predict a previously unexplored donor transition for $\textrm{B}_{\textrm{C}}$. If experimentally confirmed, this defect would represent additional problems to both p-type doped and boron contaminated 4H-SiC, not only because of its ineffectiveness as an electric dopant, but also due to trapping of up to two free holes, reducing the free-hole concentration and increasing scattering effects.
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General Relativity and Quantum Cosmology
Horizon-Scale Corrections to Black Hole Geometry from a Conserved Quantum Atmosphere
Kashif Ammar Yasir
Black holes are usually described either as classical geometries on which
quantum fields propagate or as objects whose complete
quantum description lies beyond semiclassical
gravity. Hawking radiation already shows, however, that a black hole is not an exactly isolated system: the horizon carries a thermal scale and, after coarse graining, may be associated with fluctuations, dissipation and environmental correlations. Whether this horizon-scale openness can be encoded directly in the gravitational background, before any
stochastic treatment of the metric, remains an open question. Here we answer it by introducing, for the first time, a conserved Hawking-scale anisotropic source representing the coarse-grained near-horizon atmosphere and solving the Einstein equations for a static black hole at fixed ADM mass. The dressed geometry has a renormalized mass function, a self-consistently shifted horizon and a modified surface
gravity. Because the same lapse governs the horizon and timelike geodesics, the thermal response is accompanied by a correlated orbital restructuring: the effective potential is renormalized, the ISCO moves inward and the near-horizon residence time increases. The construction adds no Langevin force to a fixed Schwarzschild background; rather, it defines a deterministic dressed mean geometry, providing a controlled background on which
stochastic metric fluctuations may subsequently be treated in the Einstein-Langevin framework. This establishes the deterministic mean-field sector as the necessary first step for future
stochastic gravity programs addressing horizon-scale openness.
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General Relativity and Quantum Cosmology
SNe Ia in Standard and Conformal Cosmological Models
A.B. Arbuzov, V. Shmidt and A.F. Zakharov
This article demonstrates the classical equivalence between standard and conformal cosmological models regarding the apparent luminosity of type Ia
supernovae. We show that previous claims of observational discrepancies stem from differing interpretations of physical quantities when transitioning between Einstein and Jordan frames. Specifically, we establish that in the conformal picture, SNe Ia are not "standard candles" in the conventional sense because their absolute luminosity depends on
redshift due to variations in local measurement units.
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Quantum Physics
Charging Dicke and Tavis–Cummings quantum batteries with a $\mathcal{PT}$-symmetric lossy–gain cavity pair
Shiqing Tang, Qing Yu, Ying Li et al. (+3 more)
We study how a parity–time-symmetric photonic environment changes the charging of Dicke and Tavis–Cummings
quantum batteries. For atoms prepared in the collective ground state the excitation number grows as the square of the charging time, with a coefficient set by the initial mean
photon number; the counter-rotating terms of the Dicke model add one to four times that number. Conservation of the total excitation number turns this into an exact ceiling on the stored Tavis–Cummings energy, the transition energy times the smaller of the
photon and atom numbers, met numerically to within two per cent, which the Dicke terms overshoot by a few per cent at ultrastrong coupling. We then couple a battery to a lossy–gain pair, keeping the parity–time
symmetry intact by putting an identical battery in each cavity; the closed moment system puts the exceptional point at the loss rate. Below it the gain cavity fills and the gain-side battery charges while the lossy-side one stays empty; above it
photons are shuttled away and dissipated. Solving the full Lindblad equation with batched Monte–Carlo wave functions, we find that the gain-side battery gains thirty-nine, twenty-six and twenty-eight per cent in stored energy, power and ergotropy in the broken phase and loses sixty-five, thirty-five and sixty-five per cent deep in the unbroken phase, where the lossy-side battery overtakes it. Restoring the counter-rotating terms leaves all of this unchanged within the statistical error; what they add is a reactive oscillation at twice the transition frequency that does no net work but nearly doubles the peak of the instantaneous power. The extra energy is of lower quality, the recoverable fraction dropping from about ninety-eight to ninety per cent. The optimum sits on the broken side, close to but not at the exceptional point.
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All authors Shiqing Tang, Qing Yu, Ying Li, Cuilu Zhai, Zhao-Hui Peng, Wangjun Lu
Instrumentation and Detectors
GEANT4-Based Comparative Study of Detector Response in Reduced and Fully Instrumented Silicon-Tungsten Sampling Calorimeter
A. Laha, S. Choudhury, S. Muhuri et al. (+1 more)
{A GEANT4-based simulation study of a silicon–tungsten (Si–W) sampling calorimeter is presented to investigate electromagnetic shower development and detector response in the energy range of 1–120 GeV. Two detector configurations are considered: a reduced sequential-sampling prototype (Configuration-I), where a single silicon detector layer is placed downstream of progressively increasing tungsten absorber depths to sample the longitudinal shower
evolution, and a fully instrumented sampling calorimeter (Configuration-II) consisting of twenty silicon layers interleaved with tungsten absorbers. The detector response is studied in terms of longitudinal shower development, shower maximum position, energy deposition, detector linearity, and calorimetric performance. Configuration-II provides simultaneous longitudinal sampling and allows event-by-event reconstruction of the deposited energy, yielding the expected linear response and energy resolution. Configuration-I reproduces the average longitudinal shower profiles and exhibits a strong linear correlation with the integrated shower response of Configuration-II. Although the absence of event-by-event multi-layer sampling prevents a direct determination of calorimetric energy resolution in Configuration-I, the observed correlation between two configurations is used to relate the response of the reduced prototype to that of the fully instrumented calorimeter and to estimate the corresponding calorimetric performance. The results demonstrate that the reduced prototype successfully reproduces the main characteristics of electromagnetic shower development observed in the fully instrumented detector, establishing its usefulness for detector characterization and test-beam studies when the construction of a complete prototype is limited by available resources.
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All authors A. Laha, S. Choudhury, S. Muhuri, M. Mondal
Materials Science
Layered spin-crossover metal-organic frameworks for light-induced control of two-dimensional quantum materials
Carla Boix-Constant, Alejandro Orellana-Silla, José Antonio Real et al. (+2 more)
Metal-organic frameworks (MOFs) are widely explored for gas separation, catalysis or energy storage, yet their integration with other electronically functional materials remains largely unexplored. Here, we integrate the layered Hofmann-type
spin-crossover (SCO) MOF {FeII(pyS2Et)2[PtII(CN)4]} into electrical nanodevices to control the properties of two-dimensional (2D)
quantum materials. Our molecular approach exploits the stimuli-responsive nature of SCO layered materials as switchable building blocks. We demonstrate selective modulation of the electronic transport in van der Waals
heterostructures interfacing SCO with 2D
quantum materials (few-layer
graphene,
magnetic CrSBr, superconducting NbSe2) through the strain induced via thermal and light-induced
spin transitions. In
graphene, the conductivity is selectively switched by light. In
spin-valves based on CrSBr
bilayers, the MOF triggers
magnetic hysteresis (absent in pristine CrSBr) and enables tunable non-volatile zero-field
memory. In NbSe2, light modulates the superconducting critical current and transition temperature. These results establish layered stimuli-responsive SCO MOFs as active molecular control elements for 2D
quantum materials, providing a route to strain-mediated control of electronic,
magnetic, and superconducting functionalities and extending MOF-based architectures beyond traditional porous-matter applications towards multifunctional electronics and spintronics.
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All authors Carla Boix-Constant, Alejandro Orellana-Silla, José Antonio Real, Samuel Mañas-Valero, Eugenio Coronado
Strongly Correlated Electrons
Two-exciton bound states in the Merrifield exciton model
Ning Wu, Runtian Li and Dazhi Xu
Understanding the formation and dynamics of two-
exciton bound states (BSs) is crucial for harnessing multi-
exciton phenomena and designing next-generation organic
semiconductor materials. While various mechanisms such as intermolecular
exciton-
exciton interactions or multi-level intramolecular configurations can generate these BSs, a fundamental understanding of their underlying
lattice dynamics remains a key challenge. Within this context, the Merrifield
exciton model stands out as a premier framework for capturing the intricate
quantum mixing between single-site doubly-excited states and two-particle scattering continuum. In this work, by constructing a set of exact two-
exciton Bloch states and applying a plane-wave ansatz to treat the resulting inhomogeneous tridiagonal
matrices, we provide a complete, rigorous solution to the two-
exciton problem in a finite-size Merrifield chain. We analytically map the parameter regions that support two-
exciton BSs, proving that at most two distinct types of BSs can emerge, located either above or below the scattering continuum. Furthermore, we provide a quantitative interpretation of how these two types of BSs evolve as a function of the total wave number within the whole Brillouin zone. The obtained closed-form expressions for the eigenenergies and wave functions offer valuable
benchmarks for exploring
exciton dynamics and optical responses in related molecular aggregates.
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Cosmology and Nongalactic Astrophysics
Stochastic Bubble Completion in de Sitter Space: Power Spectrum, Bispectrum, and Infrared Moment Hierarchies
Hyukjung Kim, Alp Kagan Ozmen and Heeseung Zoe
Stochastic bubble nucleation makes the local completion time of a first-order phase transition a random spatial field. We study its power spectrum and equilateral bispectrum in Minkowski and de Sitter backgrounds, with particular emphasis on the infrared consequences of a finite transition duration. In an eternally extended de Sitter history, rare bubbles nucleated in the remote past generate an ancient-bubble tail that produces a hierarchy of infrared-sensitive spatial moments. For the two-point function, the first finite-$k$ correction becomes tail sensitive at $H/\beta=1/5$, while the leading moment becomes singular at $H/\beta=1/3$. The corresponding three-point thresholds are $H/\beta=1/8$ and $1/6$, showing that the bispectrum is more infrared sensitive than the power spectrum. For any finite starting time, however, the ancient-bubble tail is cut off, all spatial moments remain finite, and the strict infrared spectra recover the analytic white-noise limits ${\cal P}_\tau\propto k^3$ and ${\cal B}^{\rm eq}_\tau\propto k^6$. The eternal-background thresholds instead control the duration dependence of the moment coefficients and the crossover into an intermediate tail-sensitive regime, in agreement with our numerical calculations. We further show that temporal localization of the nucleation history provides a smooth regulator of the ancient-bubble tail and restores the same analytic infrared limits. These results establish a general first-arrival framework for completion-time fluctuations and clarify how de Sitter expansion can generate distinct power-spectrum and bispectrum infrared hierarchies relevant to
curvature perturbations and non-Gaussianity.
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General Relativity and Quantum Cosmology
Scale-Invariant Non-Collapse from Raychaudhuri Comparison
Rohit Dhormare
We establish a scale-invariant spatial non-collapse estimate for hypersurface-orthogonal timelike geodesic congruences. The result extends a previous Raychaudhuri-based construction in which a comparison estimate for the expansion was used to control the volume of domains transported along the congruence. The additional ingredient here is a quantitative estimate of the spatial distance distortion induced by the expansion and shear. Assuming that the initial spatial geometry is non-collapsed up to a scale $r_0$, and that the expansion, shear, and timelike
Ricci curvature satisfy suitable uniform bounds, we obtain, before the first blow-up time of the Raychaudhuri comparison solution, \begin{equation*} \operatorname{Vol}_{h_\tau}\bigl(B_{h_\tau}(p_\tau,r)\bigr) \geq \kappa_{\mathrm{L}}(\tau)\, r^3, \end{equation*} where \begin{equation*} \kappa_{\mathrm{L}}(\tau) = \kappa_0 e^{-3K\tau} \exp\!\left(\int_0^\tau \Theta(s)\,ds\right), \qquad K = \frac{\Theta_0}{3} + \Sigma_0 . \end{equation*} Here $\Theta$ denotes the solution of the scalar Raychaudhuri comparison equation and $K$ controls the spatial metric distortion. For every finite time strictly before the comparison barrier, $\kappa_{\mathrm{L}}(\tau)$ is positive. When the comparison solution has a finite blow-up time, the explicit comparison coefficient approaches zero as that time is approached from below. The comparison barrier is a boundary of the estimate and is not, by itself, a statement that the physical congruence develops a focal point or spacetime singularity. The result is structurally analogous to scale-invariant non-collapse estimates in
geometric flow, but is mathematically distinct from Perelman's $\kappa$-noncollapsing
theorem for
Ricci flow.
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Mesoscale and Nanoscale Physics
Negative charging energy in LaAlO$_3$/SrTiO$_3$ quantum dots induced by SrTiO$_3$ polarization
J. Czarnecki, A. Sierant, B. Szafran et al. (+11 more)
We propose a microscopic mechanism for the negative charging energy in LaAlO$_3$/SrTiO$_3$
quantum dots, arising from the electrostatic image charge associated with the paraelectric response of SrTiO$_3$. Using a self-consistent configuration-interaction approach that accounts for both Coulomb repulsion and image-charge interactions, we find a robust regime of electron pairing whose strength is tunable through the confinement potential and the effective image-charge distance, set by the thickness of the interfacial two-dimensional electron gas. Our results establish dielectric image-charge effects as a route to controllable electron pairing in
oxide quantum dots and other materials with a strong dielectric response.
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All authors J. Czarnecki, A. Sierant, B. Szafran, P. Szumniak, T. S. Jespersen, G. Meucci, T. Jansen, R. Citro, A. Maiellaro, N. Bergeal, M. Bibes, M. Salluzzo, A. Kalaboukhov, P. Wójcik
Atomic Physics
Kaonic Atom X-ray Spectroscopy: From SIDDHARTA-2 to the EXKALIBUR Program
F. Sgaramella, L. Abbene, F. Artibani et al. (+31 more)
X-ray spectroscopy of kaonic atoms offers a unique experimental window on the interplay between low-energy strong interaction and precision atomic physics studies. This article reviews the scientific progress achieved with SIDDHARTA-2 at DAFNE and discusses how it shapes the next generation measurements. Particular emphasis is given to EXKALIBUR, a multifacility program designed to perform measurements of kaon-
nucleus interactions across the periodic table and to extend kaonic atom spectroscopy toward precision tests of bound-state QED and the charged-kaon mass extraction. The first proposed strong interaction campaign at J-PARC aims to investigate kaonic atoms with solid Li, Be, and B targets using new 1-mm-thick Silicon Drift Detectors and high-resolution TES microcalorimeters, exploiting isotope pairs to isolate
nuclear-structure and kaon-multinucleon effects. Measurements of Mg, Al, Si, and S with CdZnTe detectors will broaden this study toward heavier
nuclei. EXKALIBUR will establish a systematic experimental framework for testing low-energy strong interaction with strangeness and bound-state QED predictions across a broad range of kaonic atoms.
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All authors F. Sgaramella, L. Abbene, F. Artibani, M. Bazzi, G. Borghi, D. Bosnar, M. Bragadireanu, A. Buttacavoli, A. Clozza, F. Clozza, R. Del Grande, L. De Paolis, K. Dulski, C. Fiorini, I. Friščić, C. Guaraldo, T. Hashimoto, M. A. Iliescu, M. Iwasaki, A. Khreptak, S. Manti, J. Marton, P. Moskal, H. Ohnishi, F. Principato, A. Scordo, M. Silarski, D. Sirghi, F. Sirghi, M. Skurzok, A. Spallone, K. Toho, J. Zmeskal, C. Curceanu
Astrophysics of Galaxies
Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS): I. Overview of the ALMA Large Program
J. K. Jørgensen, A. Coutens, M. N. Drozdovskaya et al. (+27 more)
It remains a fundamental research question in astrochemistry to characterize the inventory of complex organic molecules formed during the early stages of
star formation, which may affect the eventual chemical composition of protoplanetary disks and potentially
planets. The Atacama Large Millimeter/submillimeter Array (ALMA) provides the angular resolution and sensitivity to zoom in on the hot (T > 100 K) gas surrounding embedded
solar-type protostars and chart their molecular inventories with high accuracy. The ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) aims to provide comprehensive inventories of the molecular content of a sample of protostellar sources to understand the chemical impact of their environments and evolutionary stages. COMPASS is an unbiased spectral survey of 11 line-rich Class 0 and I protostellar sources in the spectral range from 279.0 to 311.7 GHz at 0.15-0.5" angular resolution with ALMA, corresponding to the inner ~100 au (radius) around the targeted sources. This paper provides an overview of the COMPASS program and the adopted strategy in terms of observational setups and targeted sources. We also present a qualitative comparison of the spatial distributions of selected molecules and the relative strengths of the line fluxes of selected complex organics. The qualitative comparisons suggest that chemical differences between sources may be present, for example, between the abundances of groups of oxygen- and nitrogen-bearing species, but also that such variations occur at levels smaller than an order of magnitude. Quantitative comparisons of abundances at these levels require the large bandwidth of the survey, as well as a careful analysis of the excitation and strengths of the several thousands of lines detected toward each source in the survey, as will be explored in forthcoming papers.
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All authors J. K. Jørgensen, A. Coutens, M. N. Drozdovskaya, J.-E. Lee, A. L. Plunkett, S. Maret, A. Belloche, D. Harsono, Z. Telkamp, F. Cruz-Sáenz de Miera, M. L. R. van 't Hoff, Á Kóspál, M. Rao, J. Bergner, J.-H. Jeong, S. Spezzano, B. A. McGuire, P. Nazari, Y.-L. Yang, H.-S. Yun, A. Andreu, J. Ferrer Asensio, C.-H. Kim, N. F. W. Ligterink, Y. Lin, S.-Y. Liu, M. Lützen, P. Marchand, C. Xue, S. Zeng
Materials Science
A self-learning scientific agent for X-ray diffraction
Bin Cao, Huichi Zhou, Runyu Yang et al. (+7 more)
A central challenge for scientific
agents is to turn analytical experience into reusable expertise grounded in physical evidence. Here we introduce Gan Jiang, a self-learning
agent for powder X-ray diffraction built on a diffraction-analysis ecosystem we developed: XMatcher, XQueryer, XDecomposer and WPEM. Together, these engines span phase identification, multiphase decomposition and physics-constrained whole-pattern modelling. Gan Jiang converts analytical experience into executable skills by diagnosing failures, revising skill instructions and code, and validating revisions before reuse, without retraining the
language model or changing the underlying physical models. Skills selected using development data and frozen before held-out evaluation achieve higher refinement scores than the original expert-designed skills across FullProf, GSAS-II and PyWPEM. The
agent resolves strongly overlapping reflections, quantifies a five-phase ancient Egyptian cosmetic, tracks
lattice evolution in an operating battery and compares atomic configurations in a disordered
oxide catalyst. On DeltaXRDbench, it leads the evaluated methods in single- and multiphase identification across simulated and experimental data. Without supplied composition, single-phase top-1 accuracies reach 96.30%, 81.78% and 40.83% on MP500, RRUFF and opXRD, respectively, compared with 58.00%, 58.47% and 26.45% for the strongest comparator. These results demonstrate how an integrated scientific tool ecosystem can support
agents that extract structural knowledge from measurements while accumulating validated analytical expertise that transfers to new samples.
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All authors Bin Cao, Huichi Zhou, Runyu Yang, Jingsong Li, Shuchen Sun, Yan Song, Hanyu Gao, Zhongwei Yu, Tong-Yi Zhang, Jun Wang
Astrophysics of Galaxies
COSMOS-3D: Spectro-photometric Confirmation of Shabgard, a Cool, Metal-poor Brown Dwarf in the COSMOS Field
Bahareh S. Salmasi, Priyanka Jalan, Tomotsugu Goto et al. (+19 more)
Brown
dwarfs are unique laboratories for studying cool atmospheres, the low-mass end of
star formation, and the transition between
stars and
giant planets. Identifying and characterizing the coldest brown
dwarfs remains challenging, particularly at faint magnitudes in deep extragalactic surveys. We investigate COSMOS2025 ID639188, hereafter Shabgard, a compact source previously selected as a brown-
dwarf candidate from COSMOS-Web photometry. We use serendipitous JWST/NIRCam F444W wide-field slitless spectroscopy from COSMOS-3D, combined with COSMOS2025 NIRCam photometry and multi-epoch imaging. We extract a local-background-subtracted, profile-weighted $4.05$-$4.85\mu{\rm m}$ spectrum and compare the data with six atmosphere-model families. The LOWZ atmosphere-grid fit, using PCA interpolation and MCMC sampling, gives $T_{\rm eff}=718.6^{+10.6}_{-10.2}$ K and $[{\rm M/H}]=-1.00^{+0.07}_{-0.08}$, favoring a cool, subsolar-
metallicity atmosphere near the late-T/Y transition. A fixed-atmosphere molecular-opacity test strongly favors a contribution from CH$_4$ to the observed $4$-$5 \mu{\rm m}$ spectral shape, although the restricted wavelength coverage prevents a molecule-by-molecule abundance determination. Model-dependent physical estimates span approximately $23$-$52 {\rm M_{\rm Jup}}$ and $140$-$180$ pc. We measure a proper motion of $|\mu|=89.2\pm0.4$ mas yr$^{-1}$, while the LOWZ MCMC flux scaling gives a distance of $176.2^{+18.4}_{-17.8}$pc. Together, these results support the classification of Shabgard as a cool, metal-poor
Galactic brown
dwarf and demonstrate the ability of JWST deep-field surveys to discover and characterize faint substellar objects.
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All authors Bahareh S. Salmasi, Priyanka Jalan, Tomotsugu Goto, Tetsuya Hashimoto, Feige Wang, Tayyaba Zafar, Koki Kakiichi, Ece Kilerci, Srivardini Ayyappan, Romain A. Meyer, Anilkumar Mailvaganam, Tamal Mukherjee, Xuanyi Lyu, Imam Uzma Aalia, Arihant Raidani, Samuel Carlson, Jose Luis Carrillo Martinez, Andreas L. Faisst, Marko Shuntov, Hollis B. Akins, Zihao Li, the COSMOS-3D Collaboration
Disordered Systems and Neural Networks
Emergent Dimensionality in Diluted Power-Law Quantum Walks
G. A. Domínguez-Castro and L. Santos
We investigate single-excitation
quantum walks across the one-to-two-dimensional crossover in diluted power-law hopping models. Using arrays of $\ell$ coupled chains of length $L$, we identify the finite-size localization crossover from the longitudinal spreading of an initially localized excitation. The crossover filling is well described by an exponential approach to its two-dimensional value with increasing $\ell$, defining a characteristic transverse scale $\ell_e$, and effectively two-dimensional behavior emerges already for $\ell\ll L$. An independent spectral analysis shows that $\ell_e$ is set by the transverse extent of the eigenstates participating in the dynamics, providing a microscopic interpretation of the dimensional crossover. Our results reveal an intrinsic eigenstate scale governing emergent dimensionality in diluted systems with power-law hopping, a regime directly relevant to recently developed arrays of polar molecules, Rydberg atoms, and other
quantum simulators with long-range interactions.
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General Relativity and Quantum Cosmology
Gravitational-wave signatures of spinning particles around rotating hairy black holes
Surojit Dalui and Xian-Hui Ge
We study how the
spin of a compact secondary and a gravitational-decoupling deformation of the Kerr geometry are imprinted on gravitational waves from strong-field eccentric motion around a rotating black hole. The orbit is evolved with the Mathisson–Papapetrou–Dixon equations under the Tulczyjew
spin supplementary condition, and the radiation is computed with the numerical-kludge method. The deformation describes a black hole only below a critical curve in the plane of the two hair parameters. The
spin of the secondary pulls the pericenter inward and, above a critical value, carries the particle into the black hole. The hair raises this capture threshold, from $S\simeq0.66$ in Kerr to $0.9$ and above close to the horizon boundary, because it reduces the effective mass near the black hole. The emitted signal remains a discrete comb of orbital harmonics: the
spin strengthens the pericenter bursts and shifts power toward higher harmonics, while both the
spin and the hair leave their main imprint through an accumulated dephasing. The imprint of the hair is controlled by the parameter that sets the radial reach of the deformation, disappears in the Kerr-like limit of the family, and is amplified by the
spin of the secondary. For a source at $2$ Gpc with $M=10^6M_\odot$ and $\mu=10M_\odot$, a $6.8$ h segment of the signal carries a signal-to-noise ratio of about $1.4$ in LISA, $2.7$ in Taiji and $0.9$ in TianQin. Within the same segment the more extended deformations become distinguishable from Kerr, first in Taiji; since this holds for a nonspinning secondary, it applies directly to astrophysical EMRIs. The
spin-induced frequency shifts are linear in the
spin, so the large
spins used here are a magnified illustration of a dephasing that, for realistic secondaries, accumulates to a phase of order a radian over an inspiral.
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Nuclear Theory
Influence of nuclear matter properties on heavy-ion sub-barrier fusion reactions
Ki-Seok Choi, Hana Gil, Kouichi Hagino et al. (+3 more)
Interactions between two
nuclei in
nuclear reactions are calculated by applying the energy density method to
nuclear energy density functionals. We particularly focus on the effects of
nuclear mat- ter properties on fusion reactions by using the Korea-IBS-Daegu-SKKU (KIDS) density functional. Uncertainty of the equation of state in symmetric
nuclear matter is accounted for by using different values of the incompressibility and the effect is explored with the 40Ca+40Ca system. Though not prominent, a systematic dependence on the incompressibility can be inferred from the fusion cross sections. The effect of asymmetric
nuclear matter is described by adopting the
symmetry energy parameters that are consistent with the
neutron star data, but still have large uncertainties. In the application to the 48Ca+48Ca and 16O+208Pb systems, we observe a systematic dependence on the stiffness of the
symmetry energy. We also consider the uncertainty of the effective mass of the nucleon in
nuclear medium. We employ models that have isoscalar and isovector effective masses varying from minimum to maximum values in the allowed ranges. Contrary to incompressibility and
symmetry energy, fusion cross sections are insensitive to the isoscalar and isovector effective masses. Without any phenomenological adjustment or modification of the model, fusion processes are described accurately by applying the interaction potentials derived from
nuclear structure mod- els
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All authors Ki-Seok Choi, Hana Gil, Kouichi Hagino, W. Y. So, Chang Ho Hyun, K. S. Kim