arXiv subjects

Feng Yuan

Publications and source records attributed to Feng Yuan.

At least 55 records · Page 3Linked to original sources

arXiv2026

The variable-length stem structures in three-soliton resonance of the Kadomtsev-Petviashvili II equation

The stem structure is a localized feature that arises during high-order soliton interactions, connecting the vertices of two V-shaped waveforms. The interaction of resonant 3-solitons is accompanied by soliton reconnection phenomena, characterized by the disappearance and reconnection of stem structures. This paper investigates variable-length stem structures in resonant 3-soliton solutions of the Kadomtsev-Petviashvili II (KPII) equation, focusing on both 2-resonant and 3-resonant 3-soliton cases. Depending on the phase shift tends to plus/minus infinity, different types of resonances are identified, including strong resonance, weak resonance, and mixed (strong-weak) resonance. We derive and analyze the asymptotic forms and explicit expressions for the soliton arm trajectories, velocities, as well as the endpoints, length, and amplitude of the stem structures. A detailed comparison is made between the similarities and differences of the stem structures in the 2-resonant and 3-resonant solitons. In addition, we provide a comprehensive and rigorous analysis of both the asymptotic behavior and the structural properties of the stems.

math-ph↗

arXiv2026

Localized stem structures in quasi-resonant solutions of the Kadomtsev-Petviashvili equation

When the phase shift of X-shaped solutions before and after interaction is finite but approaches infinity, the vertices of the two V-shaped structures become separated due to the phase shift and are connected by a localized structure, which is referred to as the stem structure. This special type of elastic collision is known as a quasi-resonant collision. This study investigates quasi-resonant solutions and the associated localized stem structures in the context of the KPII and KPI equations. For the KPII equation, we classify quasi-resonant 2-solitons into weakly and strongly types, depending on whether the phase approaches $-\infty$ or $+\infty$. We analyze their asymptotic forms to detail the trajectories, amplitudes, velocities, and lengths of their stem structures. These results of quasi-resonant 2-solitons are used to to provide analytical descriptions of interesting patterns of the water waves observed on shallow water surface. Similarly, for the KPI equation, we construct quasi-resonant breather-soliton solutions and classify them into weakly and strongly types, based on the behavior of their internal parameters. We compare the similarities and differences between the stem structures in the quasi-resonant soliton and the quasi-resonant breather-soliton. Additionally, we provide a comprehensive and rigorous analysis of their asymptotic forms and stem structures. Our results indicate that the resonant solution, i.e. resonant breather-soliton of the KPI and soliton for the KPII, represents the limiting case of the quasi-resonant solution as phase approaches $\infty$.

nlin.PS↗

arXiv2025

Energy-Energy Correlators in $e^+e^-$ and Deep Inelastic Scattering

We study energy-energy correlators (EECs) in $e^+e^-$ annihilation and deep inelastic lepton-hadron scattering (DIS), focusing on aspects of nonperturbative physics in these observables. We introduce the EEC jet functions and investigate the infrared (IR) behavior of both small-angle EECs and angle-integrated EECs by performing explicit one-loop calculations. The factorization and universality of the EECs in these processes are demonstrated. A matching scheme is proposed to smoothly connect kinematic regions where different scaling behaviors with jet energy are observed. In combination with the next-to-leading order correction, this matching provides a good description of the EEC data and PYTHIA simulations in high-energy $e^+e^-$ annihilation. Predictions for DIS processes for future electron-ion collider kinematics are also presented.

hep-ph↗

arXiv2025

The role of black hole feedback on galaxy star formation and the degeneracy with halo quenching

The interplay between the accretion of supermassive black holes (SMBHs) and the stellar mass growth of the host galaxies is still a matter of hot debate. The accretion of the SMBHs is expected to release energy under the form of AGNs. This energy is believed to impact the star formation activity and contribute to the quenching of galaxies. Here, we address this key unsolved issue with our cosmological semi-empirical model DECODE. In DECODE, we grow galaxies with their SFR linked to halo accretion rate distributions via abundance matching. SMBHs are evolved following the stellar mass growth of their host galaxies by assigning an accretion rate at each redshift from the empirical Eddington ratio distributions and duty cycles. We test the assumption that galaxies permanently quench when their central SMBHs approach the limit imposed by the observed $M_{\rm BH} - σ_\star$ relation, as a proxy of SMBH disruptive feedback. We find that simply imposing the $M_{\rm BH} - σ_\star$ condition is sufficient to generate a fraction of quenched galaxies consistent with current data, including the newest ones from Euclid. In addition, our minimal, data-driven model, also predicts SMBH scaling relations consistent in slope and normalisation with those observed, and an $M_{\rm BH} - M_\star$ relation weakly evolving with redshift. The model also naturally generates SMBH accretion rates peaking within 1 Gyr of their host SFHs. We note that all the main predictions on galaxy quenched fractions and SMBH growth histories and scaling relations are degenerate with those expected in a halo quenching model. The comprehensive data-driven model presented in this work represents an invaluable tool to investigate SMBH demography across time and environments in an accurate, physically motivated manner, ideally suited to rapidly explore the implications from large surveys, such as Euclid and Rubin-LSST.

astro-ph.GA↗

arXiv2025

InternData-A1: Pioneering High-Fidelity Synthetic Data for Pre-training Generalist Policy

Recent works explore how real and synthetic data contribute to Vision-Language-Action (VLA) models' generalization. While current VLA models have shown the strong effectiveness of large-scale real-robot pre-training, synthetic data has not previously demonstrated comparable capability at scale. This paper provides the first evidence that synthetic data alone can match the performance of the strongest $π$-dataset in pre-training a VLA model, revealing the substantial value of large-scale simulation. The resulting model also exhibits surprisingly zero-shot sim-to-real transfer on several challenging tasks. Our synthetic dataset, InternData-A1, contains over 630k trajectories and 7,433 hours across 4 embodiments, 18 skills, 70 tasks, and 227 scenes, covering rigid, articulated, deformable, and fluid-object manipulation. It is generated through a highly autonomous, fully decoupled, and compositional simulation pipeline that enables long-horizon skill composition, flexible task assembly, and heterogeneous embodiments with minimal manual tuning. Using the same architecture as $π_0$, we pre-train a model entirely on InternData-A1 and find that it matches the official $π_0$ across 49 simulation tasks, 5 real-world tasks, and 4 long-horizon dexterous tasks. We release the dataset and will open-source the generation pipeline to broaden access to large-scale robotic data and to lower the barrier to scalable data creation for embodied AI research.

cs.RO↗

arXiv2025

Localized stem structures in soliton reconnection of the asymmetric Nizhnik-Novikov-Veselov system

The reconnection processes of 3-solitons with 2-resonance can produce distinct local structures that initially connect two pairs of V-shaped branches, then disappear, and later re-emerge as new forms. We call such local structures as stem structures. In this paper, we investigate the variable-length stem structures during the soliton reconnection of the asymmetric Nizhnik-Novikov-Veselov system. We consider two scenarios: weak 2-resonances (i.e., $a_{12}=a_{13}=0,\,0<a_{23}<+\infty$) and strong 2-resonances (i.e., $a_{12}=a_{13}=+\infty,\,0<a_{23}<+\infty$). We determine the asymptotic forms of the four arms and their corresponding stem structures using two-variable asymptotic analysis method which is involved simultaneously with one space variable $y$ (or $x$) and one temporal variable $t$. Different from known studies, our findings reveal that the asymptotic forms of the arms $S_2$ and $S_3$ differ by a phase shift as $t\to\pm\infty$. Building on these asymptotic forms, we perform a detailed analysis of the trajectories, amplitudes, and velocities of the soliton arms and stem structures. Subsequently, we discuss the localization of the stem structures, focusing on their endpoints, lengths, and extreme points in both weak and strong 2-resonance scenarios.

math-ph↗

arXiv2025

Radio signatures of AGN-wind-driven shocks in elliptical galaxies: From simulations to observations

We investigate the synchrotron emission signatures of shocks driven by active galactic nucleus (AGN) wind in elliptical galaxies based on our two-dimensional axisymmetric hydrodynamic MACER numerical simulations. Using these simulation data, we calculate the synchrotron radiation produced by nonthermal electrons accelerated at shocks, adopting reasonable assumptions for the magnetic field and relativistic electron distribution (derived from diffusive shock acceleration theory), and predict the resulting observational signatures. In our fiducial model, shocks driven by AGN winds produce synchrotron emission with luminosities of approximately $10^{29}\,\mathrm{erg\,s^{-1}\,Hz^{-1}}$ in the radio band (0.5-5 GHz), with spectral indices of $α\approx -0.4$ to $-0.6$ during the strongest shock phases, gradually steepening to about $-0.8$ to $-1.4$ as the electron population ages. Spatially, the emission is initially concentrated in regions of strong shocks, later expanding into more extended, diffuse structures. We also apply our model to the dwarf elliptical galaxy Messier 32 (M32), and find remarkable consistency between our simulated emission and the observed nuclear radio source, suggesting that this radio component likely originates from hot-wind-driven shocks. Our results indicate that AGN winds not only influence galaxy gas dynamics through mechanical energy input but also yield direct observational evidence via nonthermal radiation. With the advent of next-generation radio facilities such as the FAST Core Array, SKA, and ngVLA, these emission signatures serve as important probes for detecting and characterizing AGN feedback.

astro-ph.GA↗

arXiv2025

Gluon splitting at small $x$: a unified derivation for the JIMWLK, DGLAP and CSS equations

We revisit the calculation of the next-to-leading order (NLO) corrections to dijet production in electron-ion collisions at small $x$. We focus on the back-to-back configuration where the relative transverse momentum $P_\perp$ of the measured jets is much larger than both their momentum imbalance $K_\perp$ and the target saturation momentum $Q_s(x,A)$. In this regime, we present for the first time a complete calculation of the real NLO corrections at leading power in $1/P_\perp$. Our result exhibits TMD factorisation, with the same hard factor as at tree-level and a NLO correction to the Weiszäcker-Williams (WW) gluon transverse momentum dependent (TMD) distribution which involves four Wilson-line operators. By studying different kinematical regimes for $K_\perp$ and for the radiated gluon, we recover all the quantum evolutions that were previously identified for this process at NLO: the B-JIMWLK high-energy evolution and the CSS evolution of the gluon WW TMD, and the DGLAP evolution of the gluon PDF. When both $K_\perp$ and the transverse momentum transferred by the target are large compared to $Q_s$, all the Wilson-line operators boil down to the unintegrated gluon distribution and our NLO result for the gluon TMD can be used to isolate the transverse-momentum dependent gluon splitting function.

hep-ph↗

arXiv2025

Med-K2N: Flexible K-to-N Modality Translation for Medical Image Synthesis

Cross-modal medical image synthesis research focuses on reconstructing missing imaging modalities from available ones to support clinical diagnosis. Driven by clinical necessities for flexible modality reconstruction, we explore K to N medical generation, where three critical challenges emerge: How can we model the heterogeneous contributions of different modalities to various target tasks? How can we ensure fusion quality control to prevent degradation from noisy information? How can we maintain modality identity consistency in multi-output generation? Driven by these clinical necessities, and drawing inspiration from SAM2's sequential frame paradigm and clinicians' progressive workflow of incrementally adding and selectively integrating multi-modal information, we treat multi-modal medical data as sequential frames with quality-driven selection mechanisms. Our key idea is to "learn" adaptive weights for each modality-task pair and "memorize" beneficial fusion patterns through progressive enhancement. To achieve this, we design three collaborative modules: PreWeightNet for global contribution assessment, ThresholdNet for adaptive filtering, and EffiWeightNet for effective weight computation. Meanwhile, to maintain modality identity consistency, we propose the Causal Modality Identity Module (CMIM) that establishes causal constraints between generated images and target modality descriptions using vision-language modeling. Extensive experimental results demonstrate that our proposed Med-K2N outperforms state-of-the-art methods by significant margins on multiple benchmarks. Source code is available.

cs.CV↗

arXiv2025

Tracing the Origins of Hot Halo Gas in Milky Way-Type Galaxies with SMUGGLE

Current galaxy formation models predict the existence of X-ray-emitting gaseous halos around Milky Way (MW)-type galaxies. To investigate properties of this coronal gas in MW-like galaxies, we analyze a suite of high-resolution simulations based on the SMUGGLE framework and compare the results with X-ray observations of both the MW and external galaxies. We find that for subgrid models incorporating any form of stellar feedback, e.g., early feedback (including stellar winds and radiation) and/or supernova (SN) explosions, the total 0.5-2 keV luminosity is consistent within uncertainties with X-ray observations of the MW and with scaling relations derived for external disk galaxies. However, all models exhibit an X-ray surface brightness profile that declines too steeply beyond $\sim5$ kpc, underpredicting the extended emission seen in recent eROSITA stacking results. Across all subgrid prescriptions, the simulated surface brightness and emission measure fall below MW observations by at least 1-2 orders of magnitude, with the most severe discrepancy occurring in the no-feedback model. Our results suggest that (i) stellar feedback primarily shapes the innermost hot atmosphere (central $\sim5$ kpc), with comparable contributions from early feedback and SNe to the resulting X-ray luminosity; (ii) additional mechanisms such as gravitational heating, active galactic nuclei feedback, and/or Compton effects of GeV cosmic ray are necessary to generate the extended, volume-filling hot gaseous halo of MW-mass galaxies; (iii) the origins of hot corona in MW-like galaxies are partially distinct from those of the warm ($\sim10^5$ K) gas, by combining our previous finding that the SMUGGLE model successfully reproduces the kinematics and spatial distribution of MW O VI absorbers.

astro-ph.GA↗

arXiv2025

Factorization and Resummation for the Nearside Energy-Energy Correlators

By utilizing the di-hadron fragmentation formalism, we extend the previous factorization of nearside energy-energy correlators (EEC) in the collinear limit and derive an all order resummation in the Fourier transform $b_T$-space. A perfect matching is obtained when we compare to the fixed-order results. We further demonstrate the resummation effects for the EEC in $e^+e^-$ annihilation and show that they will significantly improve the theoretical predictions at small angles.

hep-ph↗

arXiv2025

Quantum Scaling in Energy Correlators Beyond the Confinement Transition

We study the QCD scaling behavior of the small-angle Energy-Energy Correlator (EEC), focusing on the transition between its perturbative pre-confinement and non-perturbative post-confinement regimes. Applying the light-ray Operator Product Expansion (OPE), we develop a formalism that describes the scaling of the EEC with the input energy $Q$ in the transition and the post-confinement region, where the latter quantum scaling is determined by the $J=5$ DGLAP anomalous dimension. A key result of our work is a novel connection between the light-ray OPE and the dihadron fragmentation function (DFF), where we show that the non-perturbative OPE coefficients correspond to moments of the DFF. This finding establishes a new paradigm for studying hadronization. Our theoretical predictions are validated against Monte Carlo simulations for both $e^+e^-$ and $pp$ collisions, showing excellent agreement. The potential role of the quantum scaling in the precision determination of $α_s$ is also discussed.

hep-ph↗

arXiv2025

The Physical Origin and Time Lag of Multi-Frequency Flares from SgrA*

Sagittarius~A$^*$, the supermassive black hole at the center of our galaxy, exhibits flares across various wavelengths, yet their origins remain elusive. We performed 3D two-temperature General Relativistic Magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows initialized from multi-loop magnetic field configuration onto a rotating black hole and conducted General Relativistic Radiative Transfer (GRRT) calculations considering contributions from both thermal and non-thermal synchrotron emission processes. Our results indicate that the polarity inversion events from the multi-loop magnetic field configurations can generate $138\,\rm THz$ flares consistent with observations with the help of non-thermal emission. By tracing the intensity evolution of light rays in GRRT calculations, we identify the precise location of the flaring region and confirm that it originates from a large-scale polarity inversion event. We observe time delays between different frequencies, with lower-frequency radio flares lagging behind higher frequencies due to plasma self-absorption in the disk. The time delay between near-infrared and 43 GHz flares can reach up to $\sim 50$ min, during which the flaring region gradually shifts outward, becoming visible at lower frequencies. Our study confirms that large-scale polarity inversion in a Standard And Normal Evolution (SANE) accretion flow with a multi-loop initial magnetic configuration can be a potential mechanism driving flares from Sgr~A$^*$.

astro-ph.HE↗

arXiv2025

Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi-Hubbard model

The measurement of the pairing gap plays an essential role in studying the physical properties of superconductors or superfluids. We develop a strategy for measure the pairing gap through the dynamical excitations. With the random phase approximation (RPA), the dynamical excitations of a two-dimensional attractive Fermi-Hubbard model are studied by calculating the dynamical structure factor. Two distinct collective modes are investigated: a Goldstone phonon mode at the transferred momentum ${\bf q}=\left[0,0\right]$ and a roton mode at ${\bf q}=\left[π,π\right]$. The roton mode demonstrates a sharp molecular peak in the low-energy regime. Remarkably, the area under the roton molecular peak scales with the square of the pairing gap, which persists even in three-dimensional and spin-orbit coupled (SOC) optical lattices. This result provides a potential strategy to measure the pairing gap of lattice systems experimentally by measuring the dynamical structure factor at ${\bf q}=\left[π,π\right]$.

cond-mat.quant-gas↗

arXiv2025

SafeClick: Error-Tolerant Interactive Segmentation of Any Medical Volumes via Hierarchical Expert Consensus

Foundation models for volumetric medical image segmentation have emerged as powerful tools in clinical workflows, enabling radiologists to delineate regions of interest through intuitive clicks. While these models demonstrate promising capabilities in segmenting previously unseen anatomical structures, their performance is strongly influenced by prompt quality. In clinical settings, radiologists often provide suboptimal prompts, which affects segmentation reliability and accuracy. To address this limitation, we present SafeClick, an error-tolerant interactive segmentation approach for medical volumes based on hierarchical expert consensus. SafeClick operates as a plug-and-play module compatible with foundation models including SAM 2 and MedSAM 2. The framework consists of two key components: a collaborative expert layer (CEL) that generates diverse feature representations through specialized transformer modules, and a consensus reasoning layer (CRL) that performs cross-referencing and adaptive integration of these features. This architecture transforms the segmentation process from a prompt-dependent operation to a robust framework capable of producing accurate results despite imperfect user inputs. Extensive experiments across 15 public datasets demonstrate that our plug-and-play approach consistently improves the performance of base foundation models, with particularly significant gains when working with imperfect prompts. The source code is available at https://github.com/yifangao112/SafeClick.

eess.IV↗

arXiv2025

WeGA: Weakly-Supervised Global-Local Affinity Learning Framework for Lymph Node Metastasis Prediction in Rectal Cancer

Accurate lymph node metastasis (LNM) assessment in rectal cancer is essential for treatment planning, yet current MRI-based evaluation shows unsatisfactory accuracy, leading to suboptimal clinical decisions. Developing automated systems also faces significant obstacles, primarily the lack of node-level annotations. Previous methods treat lymph nodes as isolated entities rather than as an interconnected system, overlooking valuable spatial and contextual information. To solve this problem, we present WeGA, a novel weakly-supervised global-local affinity learning framework that addresses these challenges through three key innovations: 1) a dual-branch architecture with DINOv2 backbone for global context and residual encoder for local node details; 2) a global-local affinity extractor that aligns features across scales through cross-attention fusion; and 3) a regional affinity loss that enforces structural coherence between classification maps and anatomical regions. Experiments across one internal and two external test centers demonstrate that WeGA outperforms existing methods, achieving AUCs of 0.750, 0.822, and 0.802 respectively. By effectively modeling the relationships between individual lymph nodes and their collective context, WeGA provides a more accurate and generalizable approach for lymph node metastasis prediction, potentially enhancing diagnostic precision and treatment selection for rectal cancer patients.

eess.IV↗

arXiv2025

Dust Growth in ALMA Rings: II. Dusty Rossby Wave Instability

Annular substructures serve as ideal venues for planetesimal formation. In this series, we investigate the linear stage of dust growth within rings. The first paper examines the global streaming instability, while this study focuses on the dusty Rossby wave instability (DRWI). We perform a linear analysis of the two-fluid equations on a background pressure bump, representing annular substructures. The spectral code \textsc{Dedalus} is used to solve the linear eigenvalue problem. We identify two distinct DRWI modes: Type I, which originates from dust-modified gas RWI, and Type II, which results from dust-gas coupling. These modes never coexist for a given azimuthal wavenumber $\ky$, but transition between each other as $\ky$ varies. Type I modes are driven by the advection of background vorticity, whereas Type II modes involve two primary waves: Rossby waves, driven by advection, and thin waves, driven by dust-gas drag. Finally, we assess the relevance of DRWI in ALMA rings using DSHARP sources. Our findings suggest that Type I modes could explain the absence of azimuthal asymmetries in many ALMA disks, whereas Type II modes are entirely absent in all eight observed rings, implying that unresolved narrow rings or alternative mechanisms may play a role in dust growth within annular substructures.

astro-ph.EP↗

arXiv2025

Comparing observed properties of winds in low-luminosity active galactic nuclei with theoretical predictions

Theoretical and numerical simulations of black hole hot accretion flows have shown the ubiquitous existence of winds and predicted their properties such as velocity and mass flux. In this paper, we have summarized from literature the physical properties of winds launched from low-luminosity active galactic nuclei (LLAGN), which are believed to be powered by hot accretion flows, and compared them with theoretical predictions. We infer that for both ultra-fast outflows and hot winds, the observed wind velocity as a function of their launching radius and the ratio between wind mass flux and black hole accretion rate show good consistency with theoretical predictions. For the prototype LLAGN M81* with abundant observational data, we have examined various observed properties of wind in detail, including velocity, mass flux of the wind, the power-law index of the radial profile of inflow rate, and the jet-to-wind power ratio. Good agreements are found with theoretical predictions, providing strong support to the theory of wind launched from hot accretion flows.

astro-ph.HE↗