Physics and Society
Community structure of the pseudofractal web
Alexei Vazquez
The Ramsey community number $r_\kappa$ is the smallest network size at which a graph is better described by a partition into communities than by no partition, under a prescribed detection rule. On a scale-free graph this question is confounded: a block model can split the network merely to absorb its degree distribution. I compute $r_\kappa$ analytically for the deterministic pseudofractal scale-free web of Dorogovtsev, Goltsev, and Mendes, separating genuine community structure from degree heterogeneity with two closed-form detection rules. Under a plain Bernoulli
stochastic block model, the web's natural recursive bipartition is unpreferred while small and breaks at $r_\kappa=1095$ nodes, with a log-evidence growing as $(\ln 3-\tfrac{2}{3}\ln 2)n$. Under a degree-corrected model tested against the configuration-model null, the same partition survives, breaking far earlier at $r_\kappa=42$, with a log-evidence growing as $(2\ln 3-\tfrac{4}{3}\ln 2)n$ – exactly twice the plain slope, and independent of the prior. Degree correction reverses the ordering of the candidate cuts, demoting the hub-leaf split and elevating the recursive one. Because the web is self-similar, the best description is not two communities but a nested hierarchy: the degree-corrected evidence keeps rising as the partition is refined, and is maximised at of order $\sqrt{n}$ communities of $\sim\sqrt{n}$ nodes. A purely local recursive rule thus builds true hierarchical community structure, over and above the scale-free degree sequence it also produces, in an exactly solvable setting.
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Optics
Heterogeneously Integrated Balanced Photodetector on an Ultra-Low Loss Silicon Nitride Delay Line Interferometer
Rahul Chawlani, Fatemehsadat Tabatabaei, Mark W. Harrington et al. (+7 more)
Thin core silicon nitride photonics enables ultra-low loss, CMOS foundry compatible integration that supports wavelengths from the visible to shortwave infrared. Applications that can benefit from the resulting lower cost, improved robustness, and portability include
quantum sensing and computing, ultra-low noise microwave generation, optical clocks, optical gyros, coherent fiber communications, and fiber sensing. An important next step is integration of functional
circuits and systems on chip with heterogeneous integration of active components such as high-performance photodetection. Yet to date integrated high-performance photodetectors on the thin film silicon nitride platform has remained elusive. In this work, we demonstrate heterogeneous integration of an InGaAs on InP substrate Modified Uni-Traveling Carrier balanced photodetector with a 15-meter-long unbalanced thin core silicon nitride Mach-Zehnder Interferometer with a bandwidth of 0.92 GHz and a responsivity of 0.305 A/W at 1550 nm with a propagation loss as low as 2.5 dB/m at 1600 nm. Using this
circuit we demonstrate two functions, a meter-scale differential interferometer
laser stabilization
circuit achieving a nearly 23 dB noise suppression at 1 kHz offset and an optical frequency discriminator frequency noise measurement with high sensitivity across 6 orders of magnitude from 10 Hz to 10 MHz. These results demonstrate that the high performance of thin core silicon nitride devices can be combined with integrated high-performance photodetection to realize on-chip stabilized
lasers and
circuits and pave the path towards full systems on chip.
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All authors Rahul Chawlani, Fatemehsadat Tabatabaei, Mark W. Harrington, Kaikai Liu, Steven M. Zhu, Jiawei Wang, Meiting Song, Xiangwen Guo, Andreas Beling, Daniel J. Blumenthal
Quantum Physics
Fringe field induced spin-OAM mixing of twisted electrons
S. V. Gatalina and S. S. Baturin
We study
spin effects in twisted-electron propagation through the entrance or exit region of an axially symmetric
magnetic coil. Starting from the Foldy-Wouthuysen reduction of the Dirac equation, we derive a paraxial spinor equation in which the longitudinally varying solenoidal field produces, in addition to the usual diagonal Zeeman term, a transverse Pauli coupling proportional to the fringe-field gradient. The scalar transverse dynamics is treated exactly by the Ermakov mapping, which absorbs the longitudinally dependent focusing into a metaplectic scaling transformation and reduces the orbital
evolution to that of a stationary two-dimensional oscillator. On this background, the transverse Pauli term is treated perturbatively and yields an explicit first-order correction for arbitrary realistic solenoidal profiles. Axial
symmetry implies conservation of the total projection of angular momentum, so each
spin flip is accompanied by a compensating one-
quantum change of orbital angular momentum. In addition, the linear coordinate structure of the perturbation restricts the first-order dynamics to at most two neighboring radial sidebands for each incoming oscillator component. We derive the corresponding transition amplitudes and show how their phases are governed jointly by the Ermakov accumulation and the diagonal
spin-orbital rotation. The resulting framework provides a direct way to quantify
spin-orbit mixing of twisted electrons in realistic
magnetic lenses and solenoidal beam-line elements, and it identifies a route toward controlled
spin-OAM conversion in engineered sequences of
magnetic-field edges.
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Quantum Physics
Symmetry-resolved parent Hamiltonians for entangled bosonic cat resources
Šimon Bräuer and Klaus Mølmer
Schrödinger cat states, formed from superpositions of well-separated coherent states, are promising resources for bosonic
quantum information. We construct parent
Hamiltonians for entangled multimode cat states by separating the selection of local coherent-state branches from the correlations and
symmetries that determine their global superposition. GHZ-, cluster-, and W-type cat states illustrate three distinct mechanisms for this construction. In the limit of well-separated branches, the resulting oscillator
Hamiltonians reduce to familiar
qubit parent models based on correlations, stabilizers, and exchange
symmetry. The same constraint structure also provides a common basis for coherent preparation, dissipative stabilization, and state certification.
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Astrophysics of Galaxies
Hayley Bignall and Rajan Chhetri
Time domain studies of active
galactic nuclei (AGN) at
radio wavelengths probe physical processes near the central engine via intrinsic variability, in particular within the relativistic jets, as well as small-scale structures in the local
Galactic interstellar medium (ISM) via scintillation and scattering effects. Recent discoveries reinforce the expectation that the high sensitivity, large field-of-view, and broadband frequency coverage of the SKA
telescopes will help to revolutionise our understanding of AGN populations and the
evolution of jets, and allow detailed modelling of the structure and dynamics of scattering
plasma in the local ISM over a large fraction of the sky.
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Fluid Dynamics
An inertial slender-body theory
Anmol Joshi, Anubhab Roy, Arjun Sharma et al. (+1 more)
We present a fully inertial slender-body theory (SBT) that incorporates the effect of fluid inertia on the scale of the length (the "outer" region) as well as the characteristic diameter (the "inner" region) of a steadily translating slender particle. This is achieved by matching the solution of the quasi-two-dimensional full Navier-Stokes equations in the inner region to an outer solution that consists of a superposition of a solution of the linearized Navier-Stokes equations driven by a line of forces and a potential flow solution driven by a line distribution of sources and source dipoles. The drag and lift forces result from the distribution of Oseen force singularities. These Oseenlets also predominantly govern the torque at small Reynolds numbers and large aspect ratios. However, the potential flow singularities play a crucial role in yielding a torque that grows with increasing Reynolds number at large Reynolds numbers and finite aspect ratios. By comparing the forces and torque on the steadily translating particle with those obtained from a finite difference Navier-Stokes solution, we demonstrate the accuracy of the resulting inertial SBT for $\mathrm{Re}_D$ up to 10, where $\mathrm{Re}_D$ is the Reynolds number based on the smallest dimension, i.e., the characteristic cross-sectional diameter of the slender particle.
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All authors Anmol Joshi, Anubhab Roy, Arjun Sharma, Donald L. Koch
Geophysics · Cross-listed from cs.LG
MABLE: Masked Autoencoding with Bi-Lipschitz Decoding for Embeddings and Graph Metric Learning
Yaniv Shulman, Shaghayegh Akbarpour and Jack B. Muir
We propose MABLE (Masked Autoencoding with Bi-Lipschitz Decoding for
Embeddings and Graph Metric Learning), a self-supervised framework for learning node and graph
embeddings from large, heterogeneous graphs, demonstrated here on geospatial mineral-exploration data. MABLE combines masked reconstruction with fixed cosine-similarity losses that align matched augmented views while keeping unpaired
embeddings well spread. A bi-Lipschitz feature decoder ties a low-dimensional reconstruction component of each node
embedding to feature similarity, while matched-node consistency shapes the remaining context used by graph pooling. Lipschitz-controlled pooling helps stabilize graph-level representations under perturbations of retained node
embeddings, while augmentation
alignment trains robustness to masking, node dropping, and sampling variation. Across local copper and regional Arabian Shield studies, MABLE
embeddings provide complementary downstream signal and produce coherent
embedding-derived layers for hypothesis generation without learned discriminators or hard-negative selection.
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Quantum Physics
Error-tolerant secure key leasing for quantum decryption keys in public-key encryption
Duo Xu and Yuki Takeuchi
We propose the first error-tolerant secure key leasing (SKL) for public-key encryption. As with SKL in prior works, our protocol consists of a lessor and lessee. In the protocol, the lessor encodes its secret key into
quantum states and leases the key to the lessee. Then, the lessor can ask the lessee to return the secret key at a later point. The lessor is able to check whether the lessee has returned its key honestly. However, our protocol works even when the leased secret key is subject to noise. The lessee decrypts the ciphertext correctly, and the lessor verifies the return of the secret key correctly when the amount of error is below a certain threshold. Our improved protocol does not change the encoding of the secret key, and thus adds no overhead to the
quantum information processing. Our most significant result is a framework to analyze the trade-off between robustness against error and security. We bridge the security of the error-tolerant SKL and that of the error-tolerant certified deletion with shortened codes, which is a relatively less explored concept in coding theory.
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Quantum Physics
Time-dependent multiparameter estimation for quantum experiments via online-offline sequential Monte-Carlo method
Chattamas Manoworakul, Jason F. Ralph, Nattaphong Wonglakhon et al. (+1 more)
While typical online estimation methods can estimate the multiparameter dynamics of many systems, they may not be sufficient for a system with highly noisy measurement and rapid detection rate. In this paper, we create a hybrid estimation method by augmenting the sequential Monte Carlo (SMC) sampler, an online estimation method with an offline technique known as the time-batch estimation technique. By continuously monitoring the system, we may divide signals into batches and average them into an averaged trajectory. The system dynamics is then evolved with batch-averaged Kraus maps, for which we derive a highly efficient approximation. To facilitate the adoption of our
algorithm, we present a modular derivation of the SMC methods and showcase our
algorithm as an explicit example. We then implement our
algorithm on the measurement signals obtained from superconducting-
qubit experiments under two types of measurement setting: a fluorescence measurement and a dispersive $z$-measurement. The
algorithm's hyperparameter values are chosen from independent numerical simulation, while the accuracy of our estimation is validated by a signal reconstruction method. Our results show that, for the fluorescence case, our
algorithm can estimate the system's parameters better than the standard calibration method, and, for the dispersive case, our estimation is capable of finding an unexpected jump in parameter values that the standard calibration method could not find.
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All authors Chattamas Manoworakul, Jason F. Ralph, Nattaphong Wonglakhon, Areeya Chantasri
Quantum Physics
Robust phase sensitivity in Mach-Zehnder interferometer using photon added and subtracted squeezed coherent state
Shivani Singh, Priya Malpani and Anirban Pathak
For the precision-based measurements, Mach-Zehnder interferometry is a widely used technique. There are various ways to enhance the precision of Mach-Zehnder interferometer (MZI), e.g., having a non-classical input state is one of the ways to enhance the precision of the phase estimation performed by MZI. The phase estimation performed by MZI is investigated here by considering that the input states of MZI are different combinations of
photon added and subtracted squeezed coherent states (PASCS and PSSCS). Using
quantum Fisher information, it is shown that the use of PASCS in both the input modes of MZI, provides the most precise estimate of the unknown phase. This system is also analyzed in two different measurement scenarios – single intensity detection (SID) and intensity difference detection (IDD). Systematic analysis has established that the intensity measurement might not be an optimal measurement scheme for phase estimation in MZI as phase and intensity correspond to non-commuting observables. The impact of the
photon loss on the MZI-based phase estimation setup is also studied and it is found that PASCS is robust against
photon loss, when the loss in MZI is low.
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Fluid Dynamics
The Excess Dissipation of Energy in a Turbulent Boundary-Layer and its Departure from Log-Normality
Benjamin Musci, Sebastien Aumaitre, Enzo Francisco et al. (+2 more)
We investigate turbulent dissipation in a von Karman flow using PIV and Diffusing Wave Spectroscopy measurements to directly compare bulk and wall dynamics. While bulk dissipation conforms to the dissipative anomaly, wall dissipation exhibits a clear excess that grows with Re, consistent with velocity-gradient dominated scaling. Decomposition into dissipation intensity bands reveals that this excess is mainly driven by progressive redistribution toward high-intensity events, larger than 10 x mean, as Re increases. From these measurements, we infer the skin-friction coefficient, finding a decreasing trend with Re fairly consistent with classical power-law behavior despite increasing dissipation. Statistically, the wall shows strong departures from log-normality at low Re that diminishes with increasing Re, reflecting an increase in the effective dimensionality of the near-wall gradient field with Re. In contrast, the bulk dissipation remains near log-normal across all Re with slowly growing log-dissipation variance, consistent with K62 refined similarity. These results suggest distinct origins of log-normal behavior which are multiplicative cascade dynamics in the bulk versus the combined effect of persistent shear and a superposition of an increasing number of independent gradient contributions at the wall.
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All authors Benjamin Musci, Sebastien Aumaitre, Enzo Francisco, Adam Cheminet, Berengere Dubrulle
High Energy Physics (Theory)
Null-strings Gauged, Reloaded and Quantized, I: Canonical Quantization in the Light-Cone Gauge
Ida M. Rasulian, M.M. Sheikh-Jabbari and H. Yavartanoo
We study the light-cone quantization of null-strings in $D$ dimensional flat target-space. Incorporating the essential new gauge
symmetry and the associated constraint structure of the null-string, allows one to solve for one more degree of freedom (DoF) compared to the standard light-cone gauge, reducing the physical phase space to $(D-3)$ propagating DoF. Quantization is formulated directly in the Schrödinger representation, leading to a
Hilbert space of wavefunctions on the reduced configuration space. The space of physical states is built on a reduced phase space associated with the corrected gauge structure. We discuss the ground-state wavefunction and a generic class of excited states. As a direct consequence of the overlooked Carroll-Weyl gauge
symmetry of the null-strings, we find the remarkable and perhaps unexpected result that null-strings exhibit a discrete spectrum. Our analysis indicate that there is no critical dimension for null-strings, and $D$ can be arbitrary.
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Astrophysics of Galaxies
Star Formation in the NE-Circinus Molecular Cloud Complex
Daniel Rose
This paper presents the first dedicated characterization of the NE-Circinus Complex (TGU H1984, DCld 320.7-03.6), a previously unstudied
star-forming dark cloud complex serendipitously identified in archival Herschel SPIRE observations targeting the foreground Bok globules BHR 99 and BHR 100. Using Herschel SPIRE photometry, Planck
Galactic Cold Clumps data, near-infrared 2MASS colour excess mapping, AllWISE photometry,
Gaia DR3 photometry, and a 3D
dust extinction map, the complex, and its embedded YSO population are characterized for the first time. Two independent photometric methods place the complex at 750 +/- 50 pc. Three morphologically distinct components are identified: a dense main cloud body, a diffuse eastern component, and a northern filamentary extension. The main cloud body has a SPIRE-derived
dust temperature of 14.5 +/- 0.5 K. Near-infrared H-K colour excess mapping yields a core gas mass of ~277 Msun and a total gas mass of ~439 Msun, consistent with the Planck PGCC column density. An AllWISE YSO census identifies 39 candidates across all three components, confirming active
star formation throughout the complex. Multi-epoch NEOWISE-R photometry reveals three significantly variable sources, including one aperiodic dipper - a previously uncatalogued YSO exhibiting dimming consistent with inner-disc occultation. Two previously uncatalogued compact Bok globules are identified on the western edge of the northern extension, both detected in SPIRE continuum emission. That this complex went uncharacterized despite Herschel data being publicly available since 2013 underscores the scientific value of archival examination and the incomplete state of southern sky molecular cloud inventories.
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Quantum Physics
Entanglement Drives Common Noise into the Strong-Coupling Regime
Yizhe Zhou, Xusheng Lei, Xing Heng et al. (+2 more)
Under Gaussian collective dephasing parallel to the signal, the superdecoherence of an $N$-atom Greenberger–Horne–Zeilinger (GHZ) state cancels its gain in Fisher information, so GHZ frequency sensitivity is limited to an atom-number-independent floor. We demonstrate that this floor is a property of Gaussian
diffusion: a single common phase kick can at most randomize the phase of an $N$-atom coherence, so discrete events at rate $\Gamma$ cannot dephase any coherence order faster than $2\Gamma$. At the same single-atom coherence time, finite-rate Poisson kicks with an absolutely continuous amplitude law therefore saturate the order-$N$ decay rate and restore Heisenberg scaling. We prove that Gaussian
diffusion is the worst case for GHZ and Dicke-cat probes under this calibration, that only the Brownian component of Lévy phase noise sets the asymptotic floor, and that the $1/N$ exponent is optimal for parallel Ramsey protocols. These results identify the counting statistics of the common noise, rather than its spectrum, as the property that bounds superdecoherence.
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All authors Yizhe Zhou, Xusheng Lei, Xing Heng, Zuoxian Wang, Danyue Ma
Quantum Physics
Full-Period Optical Phase Estimation with Heisenberg Scaling Using Displaced Squeezed States and Gaussian Measurements
Marco A. Rodríguez-García, Luis Medina-Dozal and Francisco E. Becerra
We propose two-stage optimized strategies for full-period optical phase estimation with single-mode Gaussian states and Gaussian measurements under a fixed energy constraint. In the first stage (Stage I), displaced squeezed probes and heterodyne measurements provide coarse localization of the phase to a window on the circle. In the second stage (Stage II), squeezed-
vacuum probes with adaptive homodyne measurements perform efficient phase estimation inside the selected window. We derive a generalized Cramér-Rao bound for this family of two-stage Gaussian strategies, which contains the contribution from local parameter estimation in Stage II plus an overshoot penalty from coarse localization errors in Stage I. For E <= 25
photons and squeezing limited to 12 dB, protocols using displaced squeezed states in Stage I reduce the optimized two-stage bound relative to protocols using coherent states in Stage I, and remain within a factor of 3 to 30 of the idealized local squeezed-
vacuum quantum Cramér-Rao bound.
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Mesoscale and Nanoscale Physics
Hall Shift Current and Nonlinear Anomalous Hall Effect in Gapped Dirac Fermion Systems
Toshihito Osada
We discuss a new mechanism for the nonlinear anomalous
Hall effect in tilted two-dimensional gapped Dirac
fermion systems. This mechanism originates from a side-jump displacement associated with Landau-Zener tunneling across the mass gap. In lightly doped tilted Dirac systems with a small gap, this interband mechanism can contribute to the nonlinear anomalous
Hall effect in addition to the conventional intraband mechanism arising from the Berry
curvature dipole. It provides a possible explanation for the nonlinear
Hall effect accompanied by nonlinear longitudinal transport observed in the organic Dirac
fermion system {\alpha}-(ET)2I3 with an extremely small gap.
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Chemical Physics
Chemical applicability of $\pi$-Sombor index
Monika S and H. M. Nagesh
The Sombor index ($SO$) and the modified Sombor index (${}^m SO$) are two closely related vertex-degree-based graph invariants. Both were introduced in the early 2020s and have found diverse applications in chemical, physicochemical, and network-theoretical studies. In 2023, the $\pi$-Sombor index was introduced as the product $SO \cdot {}^m SO$, with an initial focus on its fundamental mathematical properties. However, its potential chemical applicability has remained unexplored. In the present work, we address this gap by employing regression models to analyze the $\pi$-Sombor index in 22 benzenoid hydrocarbons. This study investigates the chemical significance of the $\pi$-Sombor index through curvilinear regression analysis against the physicochemical properties of these hydrocarbons.
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Astrophysics of Galaxies
The Epoch of the GSE Merger: Insights from the Splash and Thick Disk Age Distributions
Sihan Lu, Yang Huang, Qikang Feng et al. (+1 more)
The epoch of the
Gaia-Sausage-Enceladus (GSE) merger, the last major merger experienced by the Milky Way, is crucial for reconstructing the
Galaxy's evolutionary history. This event dynamically heated the disk, scattering some
stars into the
halo and producing the so-called Splash. Yet the observed age distribution of the Splash is systematically older than that of the thick disk from which it is thought to originate, posing a puzzling inconsistency. In this work, we show that this apparent discrepancy can be naturally explained once
stellar age uncertainties are taken into account. The GSE truncated the intrinsic age distribution of the Splash at the merger epoch, while measurement errors introduce an Eddington-like bias that systematically shifts the truncated distribution toward older ages. Importantly, the magnitude of this shift depends on both the thick-disk
star formation history and the merger epoch, thereby offering a new way to constrain the timing of the merger. By combining the observed Splash age distribution with the peak of thick-disk
star formation, we infer a GSE merger epoch of $10.1^{+0.2}_{-0.2}$ Gyr ago, providing one of the tightest constraints to date. This result offers new insight into the Milky Way's
accretion history and opens a path toward more robust reconstructions of its early
evolution.
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All authors Sihan Lu, Yang Huang, Qikang Feng, Huawei Zhang
High Energy Astrophysical Phenomena
No Strong Evidence for Plasma Lensing in FRB 20240114A
Jiarui Niu, Nan Xu, Xiaohui Liu et al. (+32 more)
FRB 20240114A is an extremely active repeating fast
radio burst for which
plasma lensing has been proposed to explain its burst-rate variations, spectral
evolution, and apparently “carbon-copy” burst pairs. Using FAST data and publicly available Parkes observations, we test this interpretation with the predictions of a one-dimensional Gaussian
plasma-lens model. Although the burst-rate enhancements may be fitted separately for Parkes and FAST, the corresponding magnification peaks and demagnification troughs between the two
datasets are offset from each other, inconsistent with
plasma lensing predictions. The enhancement peaks also do not show consistent periodicity, disfavoring a binary
plasma lensing origin. The burst bandwidths are not systematically narrower during the proposed
lensing interval than in other episodes. Most importantly, the burst energy distribution, which shows an intrinsic turnover peak at low energies, shows no significant shift of the turnover during the magnification interval, providing a model-independent test to the
plasma-
lensing interpretation. All these suggest that there is no strong evidence in favor of a
plasma lensing interpretation to the source. Rather, all the burst property variations are consistent with being caused by the intrinsic variations of the FRB central engine.
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All authors Jiarui Niu, Nan Xu, Xiaohui Liu, Songyu Shen, Junshuo Zhang, Tiancong Wang, Pawan Kumar, Yuanhong Qu, Dejiang Zhou, Weiwei Zhu, Bing Zhang, He Gao, Dongzi Li, Jinlin Han, Di Li, Xuelei Chen, Kejia Lee, Ye Li, Weiyang Wang, Qiuyang Fu, Jiawei Jin, Yanqing Cai, Caisong Liu, Shuo Cao, Ziwei Wu, Dengke Zhou, Longxuan Zhang, Wanjin Lu, Yi Feng, Chenhui Niu, Jiawei Luo, Rui Luo, Chunfeng Zhang, Shiqian Zhao, Chengwei Liang
Optics
Optomechanical transducers for gigahertz frequency ultrasound imaging
Lisa Hackett, Chang Ge, Alex Miera et al. (+2 more)
Ultrasound is a noninvasive, real-time, and therefore widely used imaging modality; yet its application in cellular and sub-cellular biology is significantly limited by rapidly increasing acoustic losses in aqueous solutions with decreasing wavelength. Here we introduce a nano-optomechanical cavity transducer platform to generate and detect ultrasound in aqueous solutions with a sub-micron acoustic wavelength. We analyze the full signal pathway through a combination of finite element method modeling and the coupled differential equations that describe the dispersive optomechanical interaction. Our findings project a signal-to-noise ratio in the thousands at ~5 GHz, limited by diffraction losses and thermal-acoustic noise. This work establishes a viable path towards optomechanical ultrasound systems capable of label-free imaging at cellular and sub-cellular length scales while also providing a broader framework for optomechanical
crystal device operation in aqueous environments relevant to biochemical sensing, medical diagnostics,
underwater acoustic sensing, and nanoscale imaging.
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All authors Lisa Hackett, Chang Ge, Alex Miera, Brandon Smith, Matt Eichenfield
General Relativity and Quantum Cosmology
Decoherence Effects on Primordial Black Holes and Scalar-Induced Gravitational Waves
Waqas Ahmed
Primordial black holes (PBHs) form when large
primordial curvature perturbations re-enter the Hubble radius and exceed the classical collapse threshold. These perturbations originate as
quantum fluctuations of the inflationary
vacuum, motivating a
quantum-information description of the PBH-producing scalar sector. We develop a conservative extension of the standard PBH and scalar-induced gravitational-wave (SIGW) framework in which Gaussian
quantum discord is used as a diagnostic of residual
quantum correlations, not as a new PBH-formation criterion. We describe each \((\bm k,-\bm k)\) pair as a two-mode Gaussian state and show that, in the pure squeezed limit, discord grows rapidly with the squeezing parameter, so low discord thresholds are automatically satisfied for strongly squeezed modes. The nontrivial regime is the mixed state produced by decoherence. Using a Lindblad open-system description, we motivate a Gaussian loss channel for the scalar covariance
matrix and distinguish the discord from a covariance-survival factor \(Q_{\rm dec}(k)\). If the decoherence channel suppresses the scalar two-point covariance, PBH abundance can be affected through the classical collapse variance, while the SIGW spectrum is modified more directly by the factors \(Q_{\rm dec}(ku)Q_{\rm dec}(kv)\) inside the radiation-era convolution. For a narrow scalar peak and slowly varying \(Q_{\rm dec}\), this gives the
benchmark scaling \(\Omega_{\rm GW}^{\rm eff}\simeq Q_{\rm dec}^2\Omega_{\rm GW}^{\rm class}\). Thus
quantum discord and decoherence provide a controlled way to characterize the
quantum-to-classical transition of PBH-producing perturbations, with the clearest imprint appearing in scalar-induced gravitational waves.
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Materials Science · Cross-listed from cs.CV
MatPhaseBench: A Semantics-Guided Benchmark for Materials Phase Diagrams Understanding
Hanwen Wang, Sihan Liang, Zhiwei Liu et al. (+4 more)
Materials phase diagrams are a core knowledge representation in materials science, encoding temperature,composition, phase stability, and phase transformation pathways, with their full understanding requiring thermodynamic mechanism analysis and scientific
reasoning. Although VLMs have shown promise in scientific image understanding, their systematic evaluation on such logically complex images demanding deep mechanistic interpretation remains limited, and phase diagrams provide a challenging testbed for this purpose. We introduce MatPhaseBench, a high-quality, high-reliability
benchmark for complex scientific image understanding, focused on materials phase diagrams. MatPhaseBench is constructed from 3681 papers in classical materials science journals, from which 200 high-quality diagram-text pairs were selected, covering 189 material systems and 70 elements. The
benchmark has three key features: (1)targeting complex scientific image understanding-it moves beyond simple objective tests to open-ended tasks requiring deep comprehension; (2)comprehensive image-text
alignment-semantic information associated with images is fully preserved during literature mining and matching; (3) high-quality human-supervised text acquisition-all descriptions undergo strict manual validation. Experimental results show that current VLMs remain substantially behind expert-level understanding: they are largely limited to surface visual perception, lack deep
reasoning grounded in thermodynamic mechanisms, have limited domain awareness and expert analytical experience, and perform poorly in distinguishing fine-grained differences in composite or multi-diagram settings. Overall, MatPhaseBench constitutes a challenging research-grade
benchmark, providing a foundational platform for complex scientific image understanding, phase diagram analysis, and trustworthy multi-modal AI in science.
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All authors Hanwen Wang, Sihan Liang, Zhiwei Liu, Yangang Wang, Wei Yan, Yuqin Liu, Zongguo Wang
Astrophysics of Galaxies
Revisiting the Radial Velocities of Nearby Open Clusters using Gaia DR3
Tong Tang, Yu Zhang, Jing Zhong et al. (+4 more)
Open clusters (OCs) are essential laboratories for probing
stellar dynamics and tracing the structure and
evolution of the Milky Way. Accurate measurements of their average radial velocities (RVs) and RV dispersions are crucial for estimating dynamical masses, orbital
evolution, and overall kinematic states.
Gaia Data Release 3 (DR3) provides an unprecedented volume of high-precision RVs. However, when applied to OCs,
Gaia DR3 RVs often yield unusually large and overestimated RV dispersions. This inflation is primarily driven by RV measurement systematics for hot and faint
stars, as well as unresolved binary contamination. To mitigate this, we revisit the average RVs and RV dispersions of OCs within 500 pc of the Sun using
Gaia DR3. We evaluate the reliability of RV measurements and employ a color-based filtering method. By selecting member
stars within an intrinsic color range of $0.2 \le (BP-RP)_{0} \le 1.2$ mag, we exclude hot and cool
stars with less reliable RVs. This filtering significantly reduces the inferred RV dispersions while maintaining average RVs consistent with previous literature. Specifically, the median RV dispersion decreases by 26%, dropping from 3.76 km s$^{-1}$ prior to filtering to 2.79 km s$^{-1}$ afterward. These filtered RV dispersions remain systematically larger than tangential velocity dispersions, likely due to residual biases and undetected binaries. However, RV dispersions measured exclusively from red clump
giants (found in 6 clusters) are remarkably small ($\lesssim 1.6$ km s$^{-1}$) and align closely with tangential dispersions ($\lesssim 1$ km s$^{-1}$). Ultimately, we provide a practical,
Gaia-only strategy to derive more realistic RV dispersions for OCs, identifying red clump
giants as exceptionally high-fidelity kinematic tracers for robust cluster studies.
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All authors Tong Tang, Yu Zhang, Jing Zhong, Guimei Liu, Songmei Qin, Shusong Wang, Li Chen
Medical Physics
Harmonic-Aware Transformer for Real-Time Catheter Localization in Interventional Procedures of Magnetic Particle Imaging
Abuobaida M. Khair, Wenjing Jiang, Xiaoli Yang et al. (+2 more)
Magnetic particle imaging (MPI) enables real-time, radiation-free tracking of
magnetic nanoparticle-coated instruments, making it highly suitable for interventional procedures. This study proposes a harmonic-aware
transformer framework that directly predicts catheter tip positions from raw MPI voltage signals, eliminating the need for image reconstruction and reducing computational latency. The framework incorporates frequency-domain preprocessing to isolate the 2nd to 8th drive-field harmonics, enhancing the signal-to-noise ratio while preserving motion-relevant features. A
transformer architecture with six encoder layers and eight
attention heads is employed to learn spatio-temporal dependencies across the three receive axes (x, y, z) for accurate three-dimensional position estimation. The model is trained on simulated MPI signals and evaluated on real in vitro
datasets under standard, bending, and heartbeat-like motion conditions. The proposed method achieves sub-millimeter localization accuracy, with a minimum L2 error of 0.103 +/- 0.092 mm and mean absolute errors (MAEs) of 0.039 +/- 0.046 mm, 0.054 +/- 0.049 mm, and 0.060 +/- 0.044 mm along the (x, y, z) axes, respectively, for the bending
dataset. Across all
datasets, the MAE ranges from 0.165 mm to 0.655 mm, demonstrating consistent performance. The optimized inference achieves a latency of 0.55 ms per frame and a throughput of approximately 1800 frames per second, confirming real-time capability. Compared with conventional MPI-guided approaches relying on image reconstruction, the proposed framework provides improved accuracy, reduced latency, and enhanced robustness under complex motion conditions. These results highlight the potential of harmonic-aware
transformer models as efficient and scalable solutions for real-time catheter localization in interventional MPI.
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All authors Abuobaida M. Khair, Wenjing Jiang, Xiaoli Yang, Moritz Wildgruber, Xiaopeng Ma
Materials Science
Thermophysical and mechanical properties of UFe$_2$ fabricated by spark plasma sintering
Yifan Sun, Hironobu Nakamura, Daisuke Okada et al. (+3 more)
Following the accident at the Fukushima Daiichi
Nuclear Power Plant in 2011, core meltdown produced fuel debris whose safe
retrieval and management require reliable thermophysical and mechanical property data. Among the metallic phases identified in the debris, the U-Fe system is particularly important because of the abundant iron originating from in-vessel stainless steel structures. However, within this system, the high-temperature thermophysical properties of UFe$_2$ have received relatively little
attention, with most prior studies focusing on its
magnetic and electronic properties. To fill this data gap in the literature, we fabricated dense, nearly single-phase polycrystalline UFe$_2$ by arc melting followed by spark
plasma sintering, and characterized its thermal and mechanical properties from room temperature to 1073 K. Results show that the thermal conductivity of UFe$_2$ increased monotonically from 10 Wm$^{-1}$K$^{-1}$ at 306 K to 25 Wm$^{-1}$K$^{-1}$ at 1073 K, surpassing those of the iron intermetallics Fe$_2$Zr and Fe$_2$B at high temperatures. In addition, UFe$_2$ is mechanically more compliant, displaying a Young's modulus $E$ of 69 GPa, a shear modulus $G$ of 24 GPa, and a Vickers hardness $H_{\mathrm{V}}$ of 5.6 GPa, all well below those of both Fe intermetallics. Consequently, during decommissioning, thermal-management and structural evaluations should take into account the comparatively high-conductivity and mechanically compliant nature of UFe$_2$ within the heterogeneous fuel debris.
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All authors Yifan Sun, Hironobu Nakamura, Daisuke Okada, Hiroaki Muta, Yuji Ohishi, Ken Kurosaki
Quantum Physics
Coherent Control of Three-Level System Using Shaped Free Electrons
Dixuan Wu, Jing Li, Yuhan Jiang et al. (+1 more)
Three-level systems exhibit
quantum interference effects absent in two-level systems, making them important for
quantum optics. Here, we study the coherent interaction of a Lambda-type three-level system with free electrons shaped by optical near fields. By treating the electron train as a
quantum drive, we show that the interplay between electron modulation and the three-level system's transition pathways induces tunable interference patterns. This interaction effectively realizes electron-mediated coherent population trapping (CPT). We identify a regime that enables complete population transfer between the two lower states and the preparation of a high-coherence superposition, manifested as dark states. In particular, these driven-dissipative steady states are independent of the initial state. Our work proposes shaped free electrons as a platform for steady-state coherent control of three-level systems, enabling atomic-scale state engineering.
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All authors Dixuan Wu, Jing Li, Yuhan Jiang, Yunquan Liu
High Energy Physics (Theory)
Pre-Strings Lectures on Artificial Intelligence
James Halverson
These notes are based on six lectures given over three days at the Pre-Strings 2026 school in Shanghai. Day 1 develops neural network essentials, organized around the expressivity, statistics, and dynamics of neural networks, presented with a field-theoretic lens. Day 2 develops a neural network approach to field theory (NN-FT), in which a field theory is defined by a network architecture and a density on its parameters, and surveys recent results. Examples include a universality
theorem, a neural network realization of Liouville theory, famous string amplitudes, topological sectors and the Kosterlitz-Thouless transition, Ward identities and anomalies, and a new derivation of the critical dimension of the bosonic string. Day 3 turns the lens around and covers applied AI for string theory: agentic workflows that are changing how the other techniques are implemented, physics-informed neural networks and Calabi-Yau metrics, reinforcement learning and search in the string landscape and in
knot theory, and interpretable supervised learning with an eye towards
conjecture generation.
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Optics
Demonstration and Design of Uni-Directional and Ultra-Low Threshold Hybrid Quantum Dot III-V/Si Micro-Ring Laser
Xucheng Yang, Yingtao Hu, Antoine Descos et al. (+8 more)
Micro-ring
lasers (MRLs) are attractive light sources for energy-efficient optical interconnects, but their intrinsic directional bistability leads to unpredictable clockwise/counter-clockwise emission. We demonstrate stable unidirectional emission in hybrid
quantum-dot (QD) III-V/Si MRLs using passive reflective feedback integrated on the bus waveguide, leaving the ring cavity unperturbed. Three reflector architectures - Y-splitter loop mirrors, adiabatic Y-splitter loop mirrors, and distributed Bragg reflectors (DBRs) - are benchmarked against a reflector-free bidirectional baseline through combined experiment and coupled-mode-theory rate-equation modeling. All designs preserve ultra-low thresholds of 0.79-1.12 mA (112-158 A/cm^2, roughly an order of magnitude below prior
quantum-well unidirectional ring
lasers) while enhancing single-facet output power and wall-plug efficiency, with directional isolation up to 27.65 dB for the DBR. The reflectors impose no penalty on the 4-5 GHz modulation bandwidth or its thermal robustness, establishing passive external feedback as a practical route to unidirectional QD MRLs for DWDM-scale optical interconnects.
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All authors Xucheng Yang, Yingtao Hu, Antoine Descos, Yuan Yuan, Bassem Tossoun, Geza Kurczveil, Yatiraj Ramanujam, Jonathan Wierer, Raymond G. Beausoleil, Di Liang, Stanley Cheung
Mesoscale and Nanoscale Physics
Electrically tunable interfacial thermal conduction via electronic structure engineering in ${Au}$/$Bi_{1-x}$$Sb_{x}$ topological insulators
Min Young Kim, Joon Sang Kang, Jangwoo Ha et al. (+8 more)
This work provides direct experimental evidence for the role of topological interface states in thermal conduction across a metal/topological
insulator junction. It also shows that this conduction can be reversibly modulated by electrical current injection, offering a new approach toward active control of heat flow at solid-state interfaces. Specifically, the interfacial thermal conductance of ${Au}$/$Bi_{89}$$Sb_{11}$ and ${Au}$/$Bi_{87}$$Sb_{13}$ junctions demonstrates distinct temperature- and bias-dependent behavior. Both responses are attributed to carrier redistribution between topological interface and bulk band states, driven thermally by
Fermi-Dirac broadening and electrically by quasi-
Fermi-level shifts and WKB tunneling into nearby bulk bands. Control experiments using trivial semimetals and insulating interlayers further confirm the topological specificity of the effect. Such electrically tunable interfacial heat conduction positions interface electronic structure engineering as a promising route for active thermal management. In doing so, it lays the groundwork for a mechanically robust alternative to conventional structure-driven thermal control compatible with increasingly dense, high-power solid-state devices.
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All authors Min Young Kim, Joon Sang Kang, Jangwoo Ha, Hyungyu Jin, Sandy A. Ekahana, Pratik Saud, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Jyoti Katoch, Joseph P. Heremans
Lattice Field Theory
Digital Quantum Simulation of Nonequilibrium Dynamics in the Schwinger Model under a Strong External Electric Field
Haobin Chen, Lin Cheng and Xingyu Guo
We use the (1+1)-dimensional Schwinger model to investigate the nonequilibrium dynamics of a finite
lattice system under a constant external electric field. The
lattice Hamiltonian is constructed under open boundary conditions. The
vacuum state is prepared using the variational
quantum eigensolver (VQE). Scans over the external field strength show the flip of the
vacuum state at several field strengths. The critical field strengths agree with theoretical predictions. We further investigate the real-time
evolution of the zero-field
vacuum under an external electric field using a second-order Trotter-Suzuki decomposition. By comparison with exact diagonalization (ED), we verify that the
quantum-simulation protocol reproduces the main features of field-induced boundary charge separation, decay of the
vacuum-state fidelity, and quasiperiodic energy redistribution between the electric-field energy term and the fermionic sector. Our results indicate that combining VQE-based state preparation with digital real-time
evolution provides a useful approach for studying nonequilibrium dynamics in strong-field
lattice gauge theories.
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