Quantum Physics
Physics-Constrained Conditional Generative Learning for Quantum State and Process Tomography
Daming Li and Luhao Shi
Quantum state and process
tomography constitute essential diagnostic tools in
quantum information science, yet their standard formulations suffer from prohibitive computational scaling as the number of
qubits grows. In this work, we introduce a physics-constrained conditional generative
adversarial network that bypasses iterative constrained inversion by directly learning a forward generative mapping conditioned on Pauli expectation values. The generator embeds a differentiable Cholesky layer at its output, which enforces Hermiticity, positive semidefiniteness, and unit trace by construction. Our experiments reveal that the strength of the $L^1$ penalty critically governs the emergence of GHZ coherence during training: an excessively large penalty postpones the coherence onset and yields a prolonged low-fidelity plateau, whereas an intermediate value enables the fastest stable convergence. Moreover, for high-temperature thermal states, an over-complete measurement basis proves necessary to prevent sustained late-stage fluctuations. By extending the same Cholesky constraint to the Choi-
matrix representation, the framework naturally accommodates
quantum process
tomography. For systems with $n \ge 6$
qubits, the exponential growth of the underlying $2^n \times 2^n$ density
matrix remains the fundamental bottleneck; we discuss how integrating tensor-network structures can contain the per-iteration cost while preserving reconstruction fidelity. Altogether, these results suggest that physically constrained generative learning offers a scalable and amortizable pathway toward data-driven
tomography for noisy intermediate-scale
quantum devices.
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High Energy Astrophysical Phenomena
The Geometry of Ultra-Fast Outflows Probed by Soft X-ray Variability in PDS 456
Riki Sato, Kouichi Hagino, Toshiya Iwata et al. (+20 more)
Constraining the location and geometry of ultra-fast
outflows (UFOs) is essential for identifying where they are launched and how they are accelerated. We investigate the soft X-ray variability of the luminous
quasar PDS 456 using simultaneous March 2024 observations with XRISM/Xtend and NuSTAR. A model-independent comparison between the
flare and quiescent phases reveals spectral variability around 1 keV in the rest frame, while the hard X-ray spectral shape remains nearly unchanged. Broadband spectral fitting shows that the soft X-ray structure is well described by a partial-covering low-ionization UFO with $\log (\xi/(\mathrm{erg~cm~s^{-1}})) \simeq 3.1$ and $v_{\mathrm{out}} \simeq 0.30c$. Time-sliced spectral analysis further reveals significant variability in the covering fraction of this absorber. Interpreting this variability as transverse motion across the X-ray source, we constrain the crossing velocity to be $v_{\mathrm{cross}} \lesssim 5 \times 10^{-3}c$ and derive a lower limit on the absorber distance of $r \gtrsim 4 \times 10^3 R_{\mathrm{g}}$. This location is substantially farther out than the high-ionization UFO previously inferred at ~200-600 $R_{\mathrm{g}}$, while the two phases have comparable
outflow velocities. The resulting velocity-distance structure disfavors a self-similar magnetocentrifugal wind and instead suggests either radiation-pressure acceleration following a Castor-Abbott-Klein-like velocity law or compact
magnetic acceleration through
magnetic reconnection. These results demonstrate that soft X-ray partial-covering variability can provide a geometrical probe of UFOs and directly connect spectral variability to wind acceleration.
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All authors Riki Sato, Kouichi Hagino, Toshiya Iwata, Ehud Behar, Valentina Braito, Chris Done, Misaki Mizumoto, James N. Reeves, Rozenn Boissay-Malaquin, Pierpaolo Condó, Luigi C. Gallo, Adam G. Gonzalez, Alfredo Luminari, Aiko Miyamoto, Ryuki Mizukawa, Hirokazu Odaka, Atsushi Tanimoto, Makoto Tashiro, Francesco Tombesi, Yerong Xu, Satoshi Yamada, Tahir Yaqoob, Aya Bamba
Optics
Density-gradient effect in high-harmonic generation in gases
Zoltán Filus, Tímea Grósz, Chinmoy Biswas et al. (+6 more)
High-harmonic generation (HHG) in gaseous targets is the most widespread method to produce coherent extreme-ultraviolet (XUV) pulses with sub-femtosecond duration. However, this process has intrinsically low efficiency, and substantial research and development is devoted worldwide to increase the achievable
photon flux through this highly nonlinear light–matter interaction process. In this work, we show the strong interplay of phase matching and absorption in gas-pressure gradients, substantially affecting macroscopic HHG efficiency. Through detailed experimental analysis and supporting numerical studies, we highlight their significance, particularly at the boundaries of the interaction volume. The concluded results have implications in the massively expanding application possibilities of HHG sources requiring high
photon flux, for example in the
semiconductor industry, in nanoscale imaging of biological and industrial samples, or in nonlinear optics in the XUV regime.
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All authors Zoltán Filus, Tímea Grósz, Chinmoy Biswas, Lénárd Gulyás Oldal, Tamás Bartyik, Barnabás Gilicze, Subhendu Kahaly, Katalin Varjú, Balázs Major
General Relativity and Quantum Cosmology
Dynamical friction on black holes in scalar field environment
Adith Praveen and Dawood Kothawala
Astrophysical black holes exist within non-
vacuum environments, and their motion through these environments generically result in a force on these black holes through processes such as dynamical friction and Bondi
accretion. We explore these forces numerically for black holes moving through a complex scalar field of mass $m$ with constant acceleration $a$, while also revisiting the constant velocity case considered in the existing literature. The former is modeled by the C-metric, while we use Painlevé-Gullstrand metric with an additional divergence and vorticity free velocity field to mimic the constant velocity motion. Our simulations reveal several novel and interesting aspects of the drag force in both cases. For the constant velocity case, the force saturates at late times, with a value that depends on velocity in a manner distinct from known dependence. For the constant acceleration case, the force increases to a maximum value $F_\star$ and then reduces drastically, with $F_\star \approx 0.3~ m a$. Moreover, the density wake in this case shows revivals separated by decreasing time intervals.
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Quantum Gases
Sound propagation in one-dimensional quantum droplets
Zizhou Yuan, Jiarui Xiao and Xiao-Long Chen
Sound propagation in
quantum droplets differs from that in conventional Bose-Einstein condensates (BECs) because of their self-bound nature and the role of
quantum fluctuations. We investigate sound propagation in one-dimensional
quantum droplets formed by a symmetric Bose-Bose mixture, focusing on finite-size and confinement effects. Using the extended Gross-Pitaevskii equation, we extract the sound velocity from the real-time propagation of localized density perturbations and compare it with the low-energy excitation spectrum. We find that, unlike in a conventional BEC, the sound velocity of a finite droplet is strongly affected by its density profile and
quantum-pressure contribution. It decreases with increasing particle number as the droplet evolves from a Gaussian-like to a flat-top profile, approaching the bulk
quantum-droplet value. In contrast, external harmonic confinement compresses the droplet and enhances the sound velocity, driving the system toward the acoustic behavior of a trapped BEC. Our results establish sound propagation as a sensitive probe of finite-size effects and the crossover between self-bound
quantum droplets and conventional Bose gases, and suggest a feasible route for experimental observation in ultracold $^{39}$K droplets.
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Chemical Physics
Model-free Reconstruction of Molecular Energy Levels by Broadband Kilohertz-accurate Cavity-enhanced Spectroscopy
S. Vasilchenko, A.-W. Liu, C.-X. Zuo et al. (+6 more)
Assigning the lines of high-resolution molecular spectra to
quantum states requires a
Hamiltonian model and substantial expert intervention, so the spectra of larger molecules accumulate vast numbers of unassigned lines. Here we show that molecular energy levels can instead be reconstructed directly from the raw, unassigned transition frequencies, using graph theory alone with no model and no prior assignment. Our inverse graph construction exploits recurring frequency differences and four-cycle closures to assemble an energy-level network at kilohertz precision. The dense, broadband spectra this requires are produced by a cavity-enhanced spectrometer (SCALS) that scans continuously across tens of terahertz at kilohertz accuracy, combining broadband coverage, high sensitivity, and high precision in a single automated instrument. Applied to the water absorption spectrum in the range of 1537–1605~nm, 686 Lamb dips of water were obtained without assignments, and the method reconstructs 158 energy levels that are mostly two orders of magnitude more precise than the corresponding literature values. By removing the assignment barrier, this approach opens a route to exploratory precision spectroscopy of polyatomic molecules without a priori knowledge of transition frequencies.
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All authors S. Vasilchenko, A.-W. Liu, C.-X. Zuo, Y.-Q. Cheng, Z.-T. Zhang, W.-T. Wang, Y. R. Sun, Y. Tan, S.-M. Hu
Fluid Dynamics
Validation of quasi-two-dimensional model of convection in a transverse magnetic field
Alexander Gelfgat
In this study we examine applicability of the quasi-two-dimensional (Q2D) model of natural convection in a laterally heated rectangular box subject to a transverse
magnetic field. For this purpose, results obtained using the Q2D model are compared with fully three-dimensional calculations for rectangular boxes with a square cross-section and horizontally elongated ones with the length to height ratio 8. The width to height ratio is varied from 1 to 10. It is argued that the Q2D model is valid under certain conditions, which include perfect thermal and electrical insulation of the spanwise boundaries and reflection
symmetry with respect to the spanwise midplane. It is shown that under these conditions, the Q2D model yields quantitatively correct results for boxes with square cross-section, as well as for horizontally elongated cavities, independently on the width to height ratio. Three-dimensional results obtained for boxes with perfectly conducting walls exhibit asymptotics at gradually increasing width ratio, which, however, does not agree with the predictions of an amended Q2D model. It is shown also that when is applicable, the Q2D model can correctly predict steady-oscillatory transition of three-dimensional flows. It is proposed to seek for extensions of the Q2D model for cavities with perfectly conducting spanwise boundaries.
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Earth and Planetary Astrophysics
Cooling-regulated gas accretion onto gap-opening planets
Ayumu Kuwahara, Michiel Lambrechts, Minghao Zhang et al. (+2 more)
Gas
accretion onto forming
planets controls the final masses of
giant planets and provides observable signatures of ongoing formation. How this process depends on the cooling properties of these newly attracted gas remains poorly constrained. We present long-term, three-dimensional global hydrodynamical simulations to quantify gas
accretion onto gap-opening
planets in the mass range between 1 and 3 Jupiter masses. We systematically vary the cooling time, $\beta$, from near-isothermal ($\beta=10^{-2}$ in units of orbital time) to near-adiabatic ($\beta=10^{2}$), and follow the
evolution until a quasi-steady state is reached. Our simulations show that the gas
accretion rate decreases monotonically with increasing $\beta$, as $\dot{M}_{\rm acc}\propto\beta^{-0.18}$, reaching values at $\beta=10^2$ that are approximately an order of magnitude lower than locally isothermal predictions, largely independent of
planet mass. The reduction in
accretion is traced to thermodynamic restructuring of the circumplanetary region: inefficient cooling weakens shocks, narrows the
accretion bands feeding the circumplanetary disk. Our results imply that thermodynamic effects should be taken into account when interpreting observed
accretion rates of young
planets, and may introduce systematic uncertainties in commonly used locally isothermal assumptions.
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All authors Ayumu Kuwahara, Michiel Lambrechts, Minghao Zhang, Ruobing Dong, Hideko Nomura
Statistical Mechanics
Correlated disorder versus correlated noise: Ordering in active systems
Sudip Mukherjee and Abhik Basu
Can quenched disorder generate ordering in driven systems? Using a recently proposed hydrodynamic model, we show that sufficiently long-ranged quenched disorder can induce long-range order in two-dimensional (2D) nonreciprocal XY systems, even when the clean system exhibits only short-range order at finite noise. Active surfaces tangentially advected by quenched velocities, governed by the same hydrodynamic equation, become statistically flat with super- or subdiffusive relaxation. In three dimensions (3D), quenched disorder combined with nonreciprocity produces a novel transition between strong-coupling and asymptotically noninteracting regimes, supporting either long- or short-range order. In both 2D and 3D, the exponents are nonuniversal, which vary continuously with the degree of transversality of the quenched disorder. The degree of transversality of the quenched disorder can be tuned to induce transitions in the model for fixed disorder and noise variances.
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Chemical Physics
Projected q-Shells for Nested Gausslet Bases
Steven R. White
Electronic-structure calculations require a finite representation of both the electronic wave functions and their Coulomb interaction. Conventional compact basis sets lead to a four-index interaction. Gausslet basis sets are one of a very small number of approaches that allow a much smaller two-index interaction, similar to a real-space grid, but with far fewer points. The continuing challenge in their development is reducing further the number of functions needed while maintaining high accuracy. Here we introduce projected q-shells (PQS), an improvement to the nested Cartesian gausslets of White and Lindsey. Their standard nesting construction divides a joining shell into disjoint faces, edges, and corners, reducing its
polynomial completeness from order q to order q-2. PQS approximately restores the two lost orders. In terms of completeness, we prove that for an ideal, undistorted parent, the span of the PQS basis is equivalent to an overcomplete basis of overlapping patches. Coordinate distortions, which are always used in practice, harm this equivalence only slightly. The moment properties that allow two-index interactions also become inexact, even without distortion, but we show that the improvement in order more than makes up for this loss. For similar basis sizes, PQS gives smaller one-electron and interaction errors on small molecules, such as H2+, H2, and C2, than standard nesting. The improvement is largest for more compact bases with smaller q.
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High Energy Astrophysical Phenomena
Hyperon bulk viscosity effects in neutron-star inspirals
Elena M. Kantor, Mikhail E. Gusakov and Kirill Y. Kraav
The paper revisits the role of hyperon bulk viscosity during
neutron-
star inspiral. We find that hyperon bulk viscosity exerts only a minor influence on the gravitational-wave phase, causing a phase shift of $\sim 10^{-3}\,\rm rad$. This shift is too small to be detected by existing gravitational-wave observatories, and it seems unlikely that next-generation detectors will be able to isolate this effect from other factors. However, our analysis indicates that hyperon bulk viscosity can significantly heat the hyperon core of a
neutron star, raising its temperature to approximately $5 \times 10^8\,\rm K$.
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Soft Condensed Matter
How a polymer filling enhances the rate and selectivity of colloid permeation across mesopores
Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter et al. (+2 more)
Polymer-functionalised mesopores are an emerging technology for colloid separation, sensing and delivery. Their potential is strikingly illustrated in living
cells, where
nuclear pore complexes (NPCs) control biocolloid transport between the
nucleus and the cytosol. Even colloids much smaller than the biopolymer-filled NPC channel are effectively blocked, but some larger colloids with distinct surface features rapidly permeate. Simplistically, one may expect any
polymer filling to obstruct and slow down colloid transport. We demonstrate how a
polymer filling that attracts colloids and extends beyond the mesopore, thus maximizing colloid capture, can instead increase permeation compared to a bare pore. We also define how
polymer-filled mesopores can effectively gate colloids according to their size and surface features. Our findings provide a basic physical explanation for the exquisite permselectivity of NPCs, and a rational design strategy for novel mesopore-based separation, sensing, catalysis and drug delivery devices with enhanced performance features.
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All authors Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter, Leonid I. Klushin, Oleg V. Borisov
Quantum Physics
Darell Timothy Tarigan, Fadhil Fatih Shiddiq, Hadyan Luthfan Prihadi et al. (+5 more)
Multipartite
entanglement is a critical property of parameterized
quantum circuits (PQCs), particularly for near-term hybrid
quantum-classical
algorithms, as it characterizes their ability to generate highly entangled states. However, measuring
entanglement remains computationally expensive because conventional Monte Carlo sampling scales unfavorably with system size. To overcome this challenge, we introduce a graph-based
transformer surrogate that predicts both the first-order Meyer-Wallach measure ($Q_1$) and the second-order Scott measure ($Q_2$), resolving
entanglement structures indistinguishable under $Q_1$ alone. Our central contribution is the
qubit-interconnected graph (QIG) encoding for
transformers, where each node represents a
qubit and weighted adjacencies record entangling-gate multiplicities. Fused with a gate-level DAG encoder, this yields the QIG-Fusion model. Evaluated on 50,000
circuits spanning 4- to 8-
qubit systems across a ten-seed protocol, QIG-Fusion achieves an RMSE as low as 0.037 ($Q_2$) and 0.038 ($Q_1$), with a Spearman rank correlation up to 0.95. This framework significantly reduces the computational cost of
Quantum Architecture Search (QAS), enabling efficient
entanglement estimation for large-scale PQCs.
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All authors Darell Timothy Tarigan, Fadhil Fatih Shiddiq, Hadyan Luthfan Prihadi, Donny Dwiputra, Jusak S. Kosasih, Yanoar P. Sarwono, Freddy Permana Zen, Rui-Qin Zhang
Quantum Physics
Pulsed single-photon magnetometry with a $\Lambda$-type three-level system: near-optimal frequency-resolved photon counting
Seyed Mostafa Moniri, Elnaz Darsheshdar and Mikayel Khanbekyan
We investigate pulsed single-
photon magnetometry with a Zeeman-sensitive $\Lambda$-type three-level system driven by a classical control field. We derive the asymptotic output state and decompose its
quantum Fisher information into
photon-loss, spectral-intensity, and spectral-phase contributions. Environmental coupling reshapes the scattering response and can increase
magnetic-field information. At critical coupling, real-frequency zeros of the scattering amplitude redistribute information toward measurable spectral intensity, allowing frequency-resolved
photon counting to capture nearly all of the
magnetic-field information encoded in the output state when the zeros lie within the pulse bandwidth. For long Gaussian pulses with a smooth, nonzero central-frequency scattering amplitude, the additional spectral-intensity contribution and residual spectral-phase information gap decrease as $T^{-2}$ or faster.
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Optics
Compact Variational Neural Networks for Spectral Inference from a Single Nonlinear 2D Perovskite Photodetector
Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam et al. (+4 more)
Spectroscopy conventionally separates optical frequencies before detection, imposing persistent constraints on footprint, complexity and scalability. Here we establish an alternative paradigm in which the nonlinear optoelectronic dynamics of a single two-dimensional perovskite photodetector physically encode the incident optical field and machine learning performs the inverse spectral reconstruction. Using a planar fluorinated phenethylammonium lead iodide (F-PEAI) photodetector, we exploit wavelength- and irradiance-dependent current-voltage signatures arising from the coupled effects of photocarrier generation, trapping, interfacial transport and field-dependent carrier dynamics. A compact variational encoder-decoder preserves the functional and history-dependent structure of these responses by independently projecting forward and reverse voltage sweeps onto a truncated Legendre-
polynomial basis before mapping them through a probabilistic latent representation to continuous spectral parameters. Trained on fewer than 400 experimental voltage sweeps, the model generalises to excitation wavelengths excluded from training, reconstructing wavelength with $R^2=0.958$ and a mean absolute error of 8.1 nm, while recovering log-normalised irradiance with $R^2=0.987$. Voltage-resolved analysis further reveals that wavelength and irradiance are encoded differently across the nonlinear device response, with distinct bias regions carrying complementary optical information. These results establish nonlinear material and interface dynamics as a computational resource for spectroscopy and point towards hardware-
algorithm co-design in which materials, interfaces and inference architectures are engineered jointly to maximise information content, enabling compact spectroscopic systems without dispersive optics or detector arrays.
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All authors Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam, Rosanna Mastria, Francesco Saverio Difeo, Monica Felicia Craciun, Saverio Russo
Lattice Field Theory
A different kind of continuum limit for the three-dimensional U(1) gauge theory
Andreas Athenodorou, Claudio Bonati and Ivan Soler Calero
In three-dimensional compact U(1)
lattice gauge theory color confinement can be understood analytically through the dynamics of
magnetic monopoles. However, its continuum limit is pathological, since the ratio of the glueball masses to the square root of the string tension vanishes as the continuum limit is approached. We investigate a simple extension of the Wilson action in which the total number of
lattice monopoles is coupled to an additional parameter $\mu$. By tuning $\beta$ and $\mu$ simultaneously, we identify a line of constant physics along which the ratio of the lightest glueball mass to the square root of the string tension remains constant. We further show that the same scaling is satisfied, within numerical uncertainties, by the other low-lying glueball masses considered in this work. Along this trajectory, the string tension in
lattice units decreases with increasing $\beta$, thus suggesting that the modified
lattice action may provide a regularization of three-dimensional compact U(1) gauge theory with a physically well-behaved continuum limit.
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High Energy Astrophysical Phenomena
From Inspiral to Expansion: The Wake-Driven Torque on Binary Black Holes in Gaseous Medium
Jixuan Yang, Lile Wang, Xinyu Li et al. (+1 more)
Binary black holes (BBHs) in gaseous medium, such as active
galactic nucleus (AGN) disks, are important gravitational-wave sources, yet the gas-driven torque that governs their orbital
evolution remains to be fully understood. Most existing studies of BBHs in gas often approximate the net torque as the sum of independent dynamical friction (DF) forces exerted on each black hole by its own wake, neglecting the mutual gravitational coupling between the two wakes. We perform three-dimensional hydrodynamic simulations of circular BBHs in a uniform flow and find the torque is determined by the wake-wake interactions. The net torque is controlled by a single parameter $\eta \equiv v_g/v_o$, the ratio of the gas flow velocity to the binary orbital velocity. At small $\eta$, the wakes merge into a single overdense envelope and the time-averaged torque is negative; as $\eta$ increases, the wakes separate and the torque becomes positive. In AGN disks, capture-channel binaries in a disk model naturally produce $\eta$ in the positive-torque regime; the expansion timescale is comparable to or shorter than the disk lifetime, suggesting that gas-driven expansion can compete with gravitational-wave inspiral and suppress the capture-channel merger rate.
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All authors Jixuan Yang, Lile Wang, Xinyu Li, Rixin Li
Cosmology and Nongalactic Astrophysics
Learning the averaged history of an inhomogeneous universe from its present day density field
Jonas Broe Bendtsen and Sofie Marie Koksbang
In this work, we investigate whether machine learning can be used to infer averaged cosmological quantities directly from the present day matter density distribution. Using an implementation of the simplified silent universe framework, we generate a
dataset consisting of 92610 independent relativistic, simplified cosmological simulations spanning a range of initial conditions and average cosmological parameters. We train a convolutional neural network to take the present-time matter density field as input and predict the averaged matter, cosmological constant,
curvature, and kinematical backreaction density parameters as well as the Hubble parameter, at both initial and present time. The network achieves coefficients of determination exceeding 0.9 for all predicted quantities, with error distributions showing that only a small fraction of predictions reach percent-level errors or above. Although our use of the simplified silent universe approximation precludes direct application of the trained model to observational data, the results provide a proof-of-principle that neural networks can successfully recover averaged cosmological properties, including backreaction, at different epochs, simply from the late-time matter distribution. More broadly, our findings demonstrate that information about the averaged cosmological history of a universe is encoded in its present-time density field and can be extracted using machine learning techniques. This opens the possibility of applying similar approaches to more realistic cosmological simulations and observational probes such as N-body simulations and weak-
lensing maps, ultimately providing a new avenue for constraining the large-scale
evolution of the Universe.
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High Energy Physics (Phenomenology)
Magnetic Moments and Radiative Transitions of the $T_{cc}(3875)^+$ and its partner states
Jing Wu, Yi-Kun Wang, Kai-Bao Chen et al. (+3 more)
We systematically investigate the
magnetic moments (MMs) and radiative decay widths of S-wave doubly heavy tetraquark states based on chromomagnetic interaction (CMI). They provide a complementary probe to distinguish compact from molecule structures in addition to the mass spectrum and strong decay properties. Using the CMI eigenvectors, we compute the MMs and M1 transition rates for the tetraquarks in the compact configuration. We predict the MM of the observed $T_{cc}(3875)^+$ with $I(J^P)=0(1^+)$ to be 0.45 $\mu_N$ when treating it as a compact tetraquark state, whereas the MM of the $0(1^+)$ $DD^*$ molecule is about $-0.07\,\mu_N$. Five radiative transition channels related to the $T_{cc}(3875)^+$ are identified with widths ranging from $6.07$ keV to $306.37$ keV. Our results show that the MMs of the $J^P=1^+$ $bc\bar{q}\bar{q}^\prime$ ($q/q^\prime=u,d,s$) and $J^P=1^+$ $QQ\bar{n}\bar{s}$ ($Q=b,c; n=u,d$) states are influenced by the diquark-
spin mixing. Through the analyses of radiative transitions between different tetraquark states, we find that such processes in the $QQ\bar{n}\bar{n}^\prime$, $QQ\bar{s}\bar{s}$, and $bc\bar{n}\bar{s}$ cases may serve to reveal the tetraquark structures of the initial or final states. We also define the
magnetic coupling
matrices characterizing the MMs of the tetraquark system with $J^P=1^+$, with which the range of MM can be constrained. The present study provides a valuable reference point for the search of exotic states in future particle physics experiments.
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All authors Jing Wu, Yi-Kun Wang, Kai-Bao Chen, Yan-Rui Liu, Jian-Bo Cheng, Wei-Hua Yang
Mesoscale and Nanoscale Physics
Significant modulation of acoustoelectric current associated with charge density wave transitions
Natsumi Nikaido, Takuya Kawada, Koji Fujiwara et al. (+5 more)
We studied acoustoelectric (AE) currents in materials that undergo charge density wave (CDW) transitions, induced by a surface acoustic wave (SAW) on a piezoelectric substrate. The polarity and magnitude of the AE current in NbSe$_3$ and 2H-TaSe$_2$ were modulated due to their CDW transitions. We also found that the sign of the AE current depends on the SAW propagation direction with respect to the crystalline axis of the substrate.A phenomenological model assuming strain-modified conductivity can qualitatively account for the significant modulation of the AE current associated with the CDW transition, as well as the SAW propagation orientation dependence. The present results offer a powerful probe for exploring SAW-electron interactions in van der Waals materials, thereby highlighting their potential for advancing the emerging field of straintronics.
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All authors Natsumi Nikaido, Takuya Kawada, Koji Fujiwara, Jihoon Park, Nan Jiang, Kouta Kondou, Shintaro Takada, Yasuhiro Niimi
High Energy Physics (Phenomenology)
Celestial probes of dark matter electromagnetic interactions
Alejandro Ibarra, Merlin Reichard and Gaurav Tomar
We investigate the
neutrino flux from the Sun and Earth, as well as the heating of Jupiter and white
dwarfs, induced by the annihilation of
spin-$1/2$ dark matter particles captured through their electromagnetic interactions with
nuclei. Using current data, we derive constraints on the electromagnetic moments and compare them with existing bounds from direct dark matter searches, laboratory experiments, and astrophysical observations. We find that celestial bodies provide leading constraints in several regions of parameter space: the Earth is particularly sensitive to millicharged dark matter, while massive white
dwarfs provide powerful probes of the
magnetic dipole moment, charge radius, and anapole moment in regions where direct searches lose sensitivity. We illustrate the implications of these constraints in simplified models of Dirac and Majorana dark matter with radiatively generated electromagnetic moments, as we discuss the complementarity between capture in celestial bodies and other dark matter searches.
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High Energy Physics (Theory)
Jesse van Muiden
We study
holographic ensembles in type IIB string theory on the Schur twisted AdS$_5 \times S^5$ background, and its corresponding boundary partition function: the Schur index of $\mathcal{N}=4$ SYM. In the supergravity limit the two natural ensembles are either at fixed flux on $S^5$, corresponding to a boundary theory at fixed rank, or its conjugate choice of fixed potential on the boundary of AdS$_5$, corresponding on the boundary to a grand canonical ensemble of theories at fixed chemical potential. Due to the self-dual nature of the five-form in type IIB supergravity the choice of ensembles is not seen in the standard bulk action, but rather by the coupling of an additional topological term. We compute the bulk partition function to one loop, including the Kaluza-Klein determinant and the measure of the ensemble-changing sum, and show that depending on the sign of this topological term it matches the perturbative boundary partition function in either the canonical or the grand canonical ensemble.
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High Energy Astrophysical Phenomena
Rapid Variability and Broadband Spectral Modeling in the Flaring Activity of BL Lacertae
Xin Chang, Dingrong Xiong, Chenxu Liu et al. (+17 more)
We report a multi-wavelength study of two flaring episodes of the blazar BL Lacertae during MJD 60500-60800 (9 July 2024 - 5 May 2025). The source reached a daily-averaged $\gamma$-ray flux of $(1.03 \pm 0.05) \times 10^{-5} \, \mathrm{ph \, cm^{-2} \, s^{-1}}$ ($E > 100$ MeV) on MJD 60588 (5 October 2024). Using orbit-binned data from the Large Area
Telescope (LAT) onboard the
Fermi Gamma-ray Space
Telescope, we identify a minimum flux halving timescale of $\tau = 1.33 \pm 0.29$ hr. This constrains the upper limit on the $\gamma$-ray emitting region size to $R \le 2.0 \times 10^{15}$ cm, as well as its distance from the central supermassive black hole to $R_\mathrm{H} \le 5.9 \times 10^{16}$ cm, assuming a Doppler factor of $\delta = 14.8$ derived from the spectral energy distribution (SED) modeling. We find tentative evidence for sub-minute $\gamma$-ray variability with a minimum doubling time of $0.7 \pm 0.2$ min ($p$-value = 0.03). This may originate from an extremely compact region with a size of $R \le 1.8 \times 10^{13}$ cm, suggesting that the emission arises from magnetohydrodynamic substructures, such as plasmoids within a
magnetic reconnection zone. Spectral analysis reveals a significant “softer-when-brighter” trend ($r = 0.96, p = 4.5 \times 10^{-4}$) during the minute-scale
flare peaks, indicating a complex interplay between particle acceleration and radiative cooling. The SED is reproduced using a one-zone leptonic model, in which synchrotron self-Compton (SSC) and external Compton (EC) scattering effectively account for the high-energy emissions. The reduced
magnetic field strengths and hard electron injection spectral indices observed during the flaring states suggest enhanced particle acceleration efficiency, possibly associated with relativistic
magnetic reconnection.
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All authors Xin Chang, Dingrong Xiong, Chenxu Liu, Rui Xue, Tingfeng Yi, Jia Zhang, Yu Pan, Xingzhu Zou, Xinlei Chen, YeHao Cheng, Yuanpei Yang, Jinghua Zhang, Xiangkun Liu, Yuan Fang, Guowang Du, Tao Wang, Xufeng Zhu, Zhongxiang Wang, Sarira Sahu, Xiaowei Liu
Soft Condensed Matter
Shape Evolution and Dynamics of Deformable Ring
Arun Kumar, Partha Sarathi Mondal, Pritha Dolai et al. (+1 more)
We numerically investigate the dynamics of a deformable closed ring filled with active particles. The ring is modeled as a flexible boundary made up of passive beads interacting with a harmonic spring force. The interior of the ring is filled with active Brownian particles (ABPs), and their activity is controlled through the rotational
diffusion coefficient. We explore how, by systematically varying the activity of ABPs, packing fraction, and size of the ring, we can control the shape deformation and dynamics of the ring. At low packing fractions, low rotational
diffusion coefficients, and smaller ring sizes, the ring exhibits highly irregular and strongly deformed shapes due to the uneven spatial arrangement of active particles along the boundary. Increasing the packing fraction, rotational
diffusion coefficient, or ring size promotes a more even distribution of active particles within the ring, thereby suppressing shape deformations and fluctuations, driving the ring toward a more circular shape. We further analyze the mean-squared displacement (MSD) of the ring's center of mass and observe a crossover from ballistic to diffusive dynamics, which can be tuned by varying the system parameters. Our results demonstrate that, despite its internal complexity and deformability, the ring exhibits emergent behavior analogous to that of a single effective active particle. This study provides insight into the collective effects of confined active matter and the resulting macroscopic dynamics of deformable systems.
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All authors Arun Kumar, Partha Sarathi Mondal, Pritha Dolai, Shradha Mishra
Mesoscale and Nanoscale Physics
Multi-dimensional spectroscopy of mobile excitons in two-dimensional semiconductors
Ned Wheaton, Jeffrey A. Davis, Jesper Levinsen et al. (+1 more)
Multi-dimensional coherent spectroscopy (MDCS) goes beyond standard linear-response probes and provides a powerful tool for investigating correlations between quasiparticles such as
excitons (bound electron-hole pairs). Here we present a microscopic theory of MDCS that accounts for the delocalized nature of
excitons in two-dimensional
semiconductors. In contrast to the more phenomenological few-level approaches typically employed for modelling MDCS, our theory features mobile
excitons with continuous momentum degrees of freedom. We find that the energy continuum associated with
exciton momenta is crucial for producing interaction-induced decoherence, as well as capturing the interference between different
exciton-polaron quasiparticles in the case of charge-doped
semiconductors. Crucially, our calculated MDCS spectra agree well with recent experiments on doped monolayer MoSe$_2$ [Hao et al., Nature Communications 8, 15552 (2017)], and they suggest that the interactions between
exciton polarons depend strongly on phase-space filling effects, where
exciton polarons compete for electrons. Our results demonstrate that microscopic approaches allow one to gain new insights from the fine structure of MDCS on two-dimensional
semiconductors, and they illustrate the utility of microscopic approaches to modelling MDCS experiments more generally.
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All authors Ned Wheaton, Jeffrey A. Davis, Jesper Levinsen, Meera M. Parish
Quantum Gases
Coherence Resonance Phenomena in an Atom-Dimer Two Mode BECs
Avinaba Mukherjee
We investigate the non-
equilibrium dynamics of atomic-molecular Bose-Einstein condensates coupled via a Feshbach resonance, with Gaussian white noise acting on both the coupling strength and the detuning. Using the bosonic Josephson-junction and Bloch-sphere formalisms, we examine how coherence (coupling) noise and imbalance (detuning) noise modify the coherence-resonance point as functions of the initial polarization and the Feshbach detuning. Noise plays a more coherent role when its characteristic timescale matches the intrinsic timescales of the dynamics, leading to extrema in the time-averaged purity and the Husimi-Q distribution.
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Mesoscale and Nanoscale Physics
Quantum geometric bounds at finite temperature for one-dimensional chiral systems
Peng He, Hai-Tao Ding and Yu-Guo Liu
The geometry and
topology of
quantum states are intimately related at zero temperature through exact bounds that constrain
geometric quantities from below by topological invariants. At finite-temperature, however, the analogous relations remain unclear. Here we establish rigorous
geometric lower bounds for one-dimensional (1D)
chiral-symmetric systems at finite temperature within the Uhlmann's framework for mixed states. We show that the Bures length is bounded by a continuous
geometric phase angle. We further derive a temperature-dependent bound that interpolates between the zero-temperature limit and a trivial high-temperature regime. Our results are verified analytically and numerically using the Su-Schrieffer-Heeger (SSH) model and the spinless Kitaev chain model. Finally, we discuss potential ways to detect the geometry of the density
matrix in
quantum circuits, with the
quantum imaginary time
evolution (QITE) method.
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Fluid Dynamics
High-Order CFD Modeling of Rotating Actuator Line Systems
Abdullah Al Imran and Meilin Yu
High-order computational fluid dynamics (CFD) methods combined with actuator-based blade representations provide an attractive approach for simulating rotating energy systems. In this work, we develop a high-order computational framework that couples the flux reconstruction/correction procedure via reconstruction (FR/CPR) formulation with a rotating actuator line model (ALM). Blade rotation and unsteady aerodynamic forces are implemented through time-dependent source terms applied on a fixed cartesian grid. This approach allows simulations of a fully rotating turbine without using explicit blade geometry. Aerodynamic loads are computed using quasi-steady airfoil data and distributed into the flow field with Gaussian smoothing to maintain numerical stability in the high-order scheme. The framework is tested using a two-bladed vertical-axis wind turbine (VAWT) operating at a low tip speed ratio (TSR). The phase-averaged blade motion and overall load are analyzed to study variations with azimuthal angle. In addition, instantaneous and mean flow fields are examined to describe wake structure and unsteady
vortex shedding. Normalized mean wake velocity profiles are used for validation through comparison with experimental measurements and blade-resolved large-eddy simulations (LES) reported in the literature. The results show that the proposed high-order virtual-body framework can reliably capture major blade-loading trends, flow organization, and wake features under strongly unsteady conditions, while maintaining
geometric simplicity.
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Nuclear Theory
Microscopic Realization of Topologically Quantized Alignment in Fast-Rotating Nuclei
Ganlong Ding, Sibo Wang, Hiroyuki Tajima et al. (+3 more)
We present the first quantitative microscopic realization of topologically quantized
alignment in a finite
nuclear system. The realization is obtained by exact diagonalization of a cranking seniority model, with the first Chern number evaluated over the sphere of cranking-axis orientations and analyzed together with the orientation-averaged
alignment and cranking-frame configuration probabilities. The Chern number changes in integer steps as the system evolves from initially paired configurations to increasingly aligned configurations. A new intermediate phase is found in which the Chern number is already nonzero while the
alignment continues to evolve toward its quantized value. We show that this deviation originates from the competition among pairing, axial quadrupole splitting, and Coriolis mixing. Thus, our microscopic approach reveals a more nuanced emergence of topologically quantized
alignment in realistic
nuclei, providing a quantitative stepping stone toward experimental investigations.
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All authors Ganlong Ding, Sibo Wang, Hiroyuki Tajima, Daisuke Suzuki, Jing Peng, Haozhao Liang
Statistical Mechanics
The thermodynamic freedom of a thermodynamic computer
Stephen Whitelam
Thermodynamic computers are
stochastic physical devices designed to perform calculations at the thermal energy scale. Their operation is constrained by the equations of
stochastic thermodynamics, among which are a set of bounds, known as speed limits, that relate a thermodynamic computer's run time to its computational progress and the heat it dissipates. Using the Wasserstein speed limit we assess the thermodynamic efficiency of a simulation model of a thermodynamic computer trained to perform a standard machine-learning classification task. On this task the thermodynamic computer is as capable as a simple multilayer perceptron. We show that different inference protocols allow the computer to operate within 40% of the thermodynamic limit of efficiency without loss of accuracy, or to perform inference increasingly rapidly at fixed accuracy and thermodynamic efficiency. These results indicate that a thermodynamic computer designed for a particular task retains considerable freedom in its thermodynamic operation.
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