arXiv subjects

Shuang Liu

Publications and source records attributed to Shuang Liu.

At least 55 records · Page 3Linked to original sources

arXiv2026

Adequately Tailoring Age Verification Regulations

The Supreme Court decision in Free Speech Coalition v. Paxton upheld the constitutionality of Texas H.B. 1181, one of the most constitutionally vulnerable of these age verification laws, holding that it was subject to and satisfied intermediate scrutiny and the requirement that age verification regulations be "adequately tailored". However, the decision leaves unresolved practical challenges. What is the current state of age verification legislation in the United States? How can "adequate tailoring" be interpreted in a way that is accessible to non-legal experts, particularly those in technical and engineering domains? What age verification approaches are used today, what infrastructures and standards support them, and what tradeoffs do they introduce? This paper addresses those questions by proposing an analytical model to interpret "adequate tailoring" from multiple perspectives with associated governmental goals and interests, and by applying that model to evaluate both current state laws and widely used verification methods. This paper's major contributions include: (1) we mapped the current U.S. age-verification legislative landscape; (2) we introduce an analytical model to analyze "adequate tailoring" for age verification and potential application to other online regulatory policies; and (3) we analyze the main technical approaches to age verification, highlighting the practical challenges and tradeoffs from a technical perspective. Further, while we focus on U.S. State laws, the principles underlying our framework are applicable to age-verification debates and methods worldwide.

cs.CY↗

arXiv2026

Multi-mode Coherent Detection Ghost Imaging Lidar and Vibration-Mode Imaging

Coherent detection ghost imaging lidar (CD-GI lidar) integrates ghost imaging with coherent detection, thereby achieving enhanced anti-interference and phase-resolved imaging capability. Here, we propose a bucket-detector-based multi-mode coherent detection scheme for CD-GI lidar, where the reflected multi-mode light fields are coherently mixed with a single-mode local oscillator (LO) at the bucket detector photosensitive plane. The bucket-detector-based multi-mode CD-GI lidar system breaks the constraints of Siegman antenna theorem by utilizing field correlation to decouple the reflected multi-mode light fields and reconstructs the spatial distribution of targets' vibration modes. Theoretical analysis of the bucket-detector-based multi-mode CD-GI lidar system is presented in this work, and its feasibility is verified through a series of experiments.

physics.optics↗

arXiv2026

On the Ricci flow on Trees

In this paper, we study the evolution of metrics on finite trees under continuous-time Ricci flows based on the Lin-Lu-Yau version of Ollivier Ricci curvature. We analyze long-time dynamics of edge weights and curvatures, providing precise characterizations of their limiting behaviors. We prove that the Ricci flow converges to metric with zero curvature on edges whose normalized weights converge to positive values only if the tree is a caterpillar tree.

math.DG↗

arXiv2026

LLM Agents in Law: Taxonomy, Applications, and Challenges

Large language models (LLMs) have precipitated a dramatic improvement in the legal domain, yet the deployment of standalone models faces significant limitations regarding hallucination, outdated information, and verifiability. Recently, LLM agents have attracted significant attention as a solution to these challenges, utilizing advanced capabilities such as planning, memory, and tool usage to meet the rigorous standards of legal practice. In this paper, we present a comprehensive survey of LLM agents for legal tasks, analyzing how these architectures bridge the gap between technical capabilities and domain-specific needs. Our major contributions include: (1) systematically analyzing the technical transition from standard legal LLMs to legal agents; (2) presenting a structured taxonomy of current agent applications across distinct legal practice areas; (3) discussing evaluation methodologies specifically for agentic performance in law; and (4) identifying open challenges and outlining future directions for developing robust and autonomous legal assistants.

cs.CY↗

arXiv2026

The weighted Forman and Lin-Lu-Yau Ricci flow on graphs

In this paper, we propose a type of Ricci flow on graphs where the probability distribution for the Lin-Lu-Yau curvature remains constant over time, and also study the related Forman curvature flow. These two curvature flows coincide on trees. We first prove the existence and uniqueness of solutions for both curvature flows in general graphs. Then, we obtain that the normalized curvature flow on trees converges to a constant curvature metric, and under the uniform measure, a complete classification of trees can be obtained based on the convergence results.

math.DG↗

arXiv2025

In-plane optically tunable magnetic states in 2D materials via tailored femtosecond laser driving

It is well established that light can control magnetism in matter, e.g. via the inverse Faraday effect or ultrafast demagnetization. However, such control is typically limited to magnetization transverse to light's polarization plane, or out-of-plane magnetism in 2D materials, while in-plane magnetic moments have remained largely unexplored. This is due to the difficulty of generating electronic orbital angular momentum components within light's polarization plane. Here we overcome this limitation, demonstrating complete three-dimensional, all-optical control of magnetism in 2D materials. Using first-principles simulations, we show that a tailored, two-color laser field can induce and steer magnetic moments in any direction with the relative angle between the laser polarizations playing a key parameter in coherent control. We analyze the physical mechanism of this process and show that it arises from a simultaneous breaking of time-reversal and spatial-inversion symmetries in the two-color laser. In-plane orbital moments are introduced via non-zero out-of-plane longitudinal photogalvanic currents enabled by broken inversion and mirror symmetries, while time-reversal symmetry breaking enables build-up of spin-rotation processes through spin-orbit coupling, translating the orbital moments to transient magnetism. Our findings demonstrate a full 3D coherent control scheme for transient magnetic states on femtosecond timescales driven by tailored lasers, and can be used to develop novel spectroscopies for magnetism, all-optical magnetic switching for ultrafast spintronics, and novel information storage capabilities.

physics.optics↗

arXiv2025

Anomaly Pattern-guided Transaction Bug Testing in Relational Databases

Concurrent transaction processing is a fundamental capability of Relational Database Management Systems (RDBMSs), widely utilized in applications requiring high levels of parallel user interaction, such as banking systems, e-commerce platforms, and telecommunications infrastructure. Isolation levels offer a configurable mechanism to manage the interaction between concurrent transactions, enabling varying degrees of consistency and performance trade-offs. These isolation guarantees are supported by all major RDBMSs. However, testing transaction behavior under different isolation levels remains a significant challenge due to two primary reasons. First, automatically generating test transactions that can effectively expose bugs in transaction handling logic is non-trivial, as such bugs are typically triggered under specific transactional constraints. Second, detecting logic anomalies in transaction outcomes is difficult because the correct execution results are often unknown for randomly generated transactions. To address these challenges, we propose an anomaly pattern-guided testing approach for uncovering transaction bugs in RDBMSs. Our solution tackles the first challenge by introducing a test case generation technique guided by predefined anomaly patterns, which increases the likelihood of exposing transactional bugs. For the second challenge, we present a two-phase detection process, involving explicit error detection and implicit error detection, to identify bugs in transaction execution. We have implemented our approach in a tool, APTrans, and evaluated it on three widely-used RDBMSs: MySQL, MariaDB, and OceanBase. APTrans successfully identified 13 previously unknown transaction-related bugs, 11 of which have been confirmed by the respective development teams.

cs.DB↗

arXiv2025

Pelican-VL 1.0: A Foundation Brain Model for Embodied Intelligence

This report presents Pelican-VL 1.0, a new family of open-source embodied brain models with parameter scales ranging from 7 billion to 72 billion. Our explicit mission is clearly stated as: To embed powerful intelligence into various embodiments. Pelican-VL 1.0 is currently the largest-scale open-source embodied multimodal brain model. Its core advantage lies in the in-depth integration of data power and intelligent adaptive learning mechanisms. Specifically, metaloop distilled a high-quality dataset from a raw dataset containing 4+ billion tokens. Pelican-VL 1.0 is trained on a large-scale cluster of 1000+ A800 GPUs, consuming over 50k+ A800 GPU-hours per checkpoint. This translates to a 20.3% performance uplift from its base model and outperforms 100B-level open-source counterparts by 10.6%, placing it on par with leading proprietary systems on well-known embodied benchmarks. We establish a novel framework, DPPO (Deliberate Practice Policy Optimization), inspired by human metacognition to train Pelican-VL 1.0. We operationalize this as a metaloop that teaches the AI to practice deliberately, which is a RL-Refine-Diagnose-SFT loop.

cs.LG↗

arXiv2025

Three-dimensional flat bands and possible interlayer triplet pairing superconductivity in the alternating twisted NbSe$_2$ moiré bulk

Moiré superlattices hosting flat bands and correlated states have emerged as a focal topic in condensed matter research. Through first-principles calculations, we investigate three-dimensional flat bands in alternating twisted NbSe$_2$ moiré bulk structures. These structures exhibit enhanced interlayer interactions compared to twisted bilayer configurations. Our results demonstrate that moiré bulks undergo spontaneous large-scale structural relaxation, resulting in the formation of remarkably flat energy bands at twist angles $\leq$ 7.31°. The $k_z$-dependent dispersion of flat bands across different moiré bulks reveals their intrinsic three-dimensional character. The presence of out-of-plane mirror symmetry in these moiré bulk structures suggests possible interlayer triplet superconducting pairing mechanisms that differ from those in twisted bilayer systems. Our work paves the way for exploring potential three-dimensional flat bands in other moiré bulk systems.

cond-mat.supr-con↗

arXiv2025

Testing Question Answering Software with Context-Driven Question Generation

Question-answering software is becoming increasingly integrated into our daily lives, with prominent examples including Apple Siri and Amazon Alexa. Ensuring the quality of such systems is critical, as incorrect answers could lead to significant harm. Current state-of-the-art testing approaches apply metamorphic relations to existing test datasets, generating test questions based on these relations. However, these methods have two key limitations. First, they often produce unnatural questions that humans are unlikely to ask, reducing the effectiveness of the generated questions in identifying bugs that might occur in real-world scenarios. Second, these questions are generated from pre-existing test datasets, ignoring the broader context and thus limiting the diversity and relevance of the generated questions. In this work, we introduce CQ^2A, a context-driven question generation approach for testing question-answering systems. Specifically, CQ^2A extracts entities and relationships from the context to form ground truth answers, and utilizes large language models to generate questions based on these ground truth answers and the surrounding context. We also propose the consistency verification and constraint checking to increase the reliability of LLM's outputs. Experiments conducted on three datasets demonstrate that CQ^2A outperforms state-of-the-art approaches on the bug detection capability, the naturalness of the generated questions as well as the coverage of the context. Moreover, the test cases generated by CQ^2A reduce error rate when utilized for fine-tuning the QA software under test

cs.SE↗

arXiv2025

Ricci Flow on Weighted Digraphs with Balancing Factor

Ricci curvature and Ricci flow have proven to be powerful tools for analyzing the geometry of discrete structures, particularly on undirected graphs, where they have been applied to tasks ranging from community detection to graph representation learning. However, their development on directed graphs remains limited, with Ricci flow being especially underexplored. In this work, we introduce a rigorous formulation of Ricci flow on directed weighted graphs, which evolves edge weights while preserving distances, and establish both the existence and uniqueness of its solutions. To capture the essence of asymmetry in directed networks and to enhance the capability of modeling more flexible structures, we incorporate a node-wise balancing factor that regulates between outflow and inflow. Building on the continuous Ricci flow evolution framework, we propose a discrete Ricci flow algorithm that is applicable to numerical computing. Numerical studies on various directed graph examples demonstrate the capacity of the proposed flow to reveal structural asymmetry and dynamic evolutions.

math.DG↗

arXiv2025

OmniD: Generalizable Robot Manipulation Policy via Image-Based BEV Representation

The visuomotor policy can easily overfit to its training datasets, such as fixed camera positions and backgrounds. This overfitting makes the policy perform well in the in-distribution scenarios but underperform in the out-of-distribution generalization. Additionally, the existing methods also have difficulty fusing multi-view information to generate an effective 3D representation. To tackle these issues, we propose Omni-Vision Diffusion Policy (OmniD), a multi-view fusion framework that synthesizes image observations into a unified bird's-eye view (BEV) representation. We introduce a deformable attention-based Omni-Feature Generator (OFG) to selectively abstract task-relevant features while suppressing view-specific noise and background distractions. OmniD achieves 11\%, 17\%, and 84\% average improvement over the best baseline model for in-distribution, out-of-distribution, and few-shot experiments, respectively. Training code and simulation benchmark are available: https://github.com/1mather/omnid.git

cs.RO↗

arXiv2025

Scaling Laws in Plasma Channels for Laser Wakefield Accelerators

Preformed plasma channels are essential for guiding high-power laser pulses over extended distances in laser wakefield accelerators, enabling the generation of multi-GeV electron beams for applications such as free-electron lasers and particle colliders. Above-threshold ionization heating provides a robust mechanism for creating laser-matched plasma channels across a wide parameter range, owing to its density- and geometry-independent heating effect. Establishing predictive scaling laws between channel parameters and formation conditions is critical for designing channels optimized for electron acceleration across energies spanning hundreds of MeV to tens of GeV. Through combined timescale analysis and numerical simulations, hydrodynamic expansion is identified as the dominant mechanism governing density profile evolution during ATI channel formation. Remarkably, this process maintains effective laser-guiding channel structures across a wide range of initial gas density, as evidenced by the persistent profile similarity observed despite these significant parameter variations. For parabolic channels matched to Gaussian laser drivers, rigorous scaling laws are established that, the on-axis density scales linearly with the initial gas density, while the matching radius has an exponential dependence on both the initial gas density and the ionization laser radius. These findings provide a systematic framework for the predictive design and optimization of plasma channels in high-efficiency and high-energy LWFA applications.

physics.plasm-ph↗

arXiv2025

Laser Driven Bulk-to-Layered Phase Transition

Laser-induced phase transitions offer pathways of phase transitions that are inaccessible by conventional stimuli. In this study, we conduct ab initio simulations to numerically demonstrate a novel laser-induced structural transformation: converting a bulk crystal into a layered van der Waals material using intense light pulses. The transition is driven by a nonlinear phononic mechanism, where selectively exciting polar and anti-polar phonon modes with polarized terahertz light breaks targeted interlayer bonds while preserving intralayer ones. We identify that strong anisotropy in bond sensitivity where interlayer bonds are significantly more susceptible to excitation than intralayer bonds is the critical prerequisite. Our findings pave the way for on demand transformations from bulk to 2D materials, facilitate the design of advanced phase-change devices, and suggest a potential optical exfoliation method to expand the range of exfoliable 2D materials.

physics.optics↗

arXiv2025

ContractEval: Benchmarking LLMs for Clause-Level Legal Risk Identification in Commercial Contracts

The potential of large language models (LLMs) in specialized domains such as legal risk analysis remains underexplored. In response to growing interest in locally deploying open-source LLMs for legal tasks while preserving data confidentiality, this paper introduces ContractEval, the first benchmark to thoroughly evaluate whether open-source LLMs could match proprietary LLMs in identifying clause-level legal risks in commercial contracts. Using the Contract Understanding Atticus Dataset (CUAD), we assess 4 proprietary and 15 open-source LLMs. Our results highlight five key findings: (1) Proprietary models outperform open-source models in both correctness and output effectiveness, though some open-source models are competitive in certain specific dimensions. (2) Larger open-source models generally perform better, though the improvement slows down as models get bigger. (3) Reasoning ("thinking") mode improves output effectiveness but reduces correctness, likely due to over-complicating simpler tasks. (4) Open-source models generate "no related clause" responses more frequently even when relevant clauses are present. This suggests "laziness" in thinking or low confidence in extracting relevant content. (5) Model quantization speeds up inference but at the cost of performance drop, showing the tradeoff between efficiency and accuracy. These findings suggest that while most LLMs perform at a level comparable to junior legal assistants, open-source models require targeted fine-tuning to ensure correctness and effectiveness in high-stakes legal settings. ContractEval offers a solid benchmark to guide future development of legal-domain LLMs.

cs.AI↗

arXiv2025

The Impact of Inhomogeneous Perturbations of the Inflaton on the Cosmological Primordial Magnetic Field

We investigate the impact of inhomogeneous inflaton perturbations on primordial magnetic fields within the framework of generalized inflationary magnetogenesis models. Extending the Ratra model to general spacetime backgrounds, we analyze the constraint structure of the electromagnetic field and demonstrate that the standard Coulomb gauge must be generalized to accommodate spatial inhomogeneities. Instead of the vector potential, we solve the conjugate momentum with the modified initial conditions introduced by the coupling function, which become dominant during the late stages of inflation. These change the conditions under which scale-invariant electromagnetic spectra are achieved. Furthermore, we address the challenge of evaluating convolutions between vector potentials and inflaton perturbations by employing separate large- and small-scale approximations. The resulting influence to the electric and magnetic power spectra are quantified using $Δ_E$ and $Δ_B$, revealing a scale-dependent influence of inhomogeneities. We also find that the spectrum index evolution is sensitive to the sign of $V_ϕ$, with distinctive behaviors for electric and magnetic fields under different scale-invariance conditions. Notably, for nearly scale-invariant magnetic fields, the perturbative effects shift the spectral index towards the red and migrate toward smaller scales as inflation progresses, offering a potential observational probe to differentiate between large-field and small-field inflation scenarios.

astro-ph.CO↗

arXiv2025

A Glimpse of Satellite Galaxies in the Milky Way with the 2.5-meter Wide Field Survey Telescope (WFST): Bootes III and Draco

We carry out deep imaging of the Milky Way satellite galaxies, Bootes III and Draco, with WFST as one pilot observing program to demonstrate the capability of WFST. Combining catalogs with PS1 DR2 and Gaia DR3, we derive proper motions for candidate member stars in these two satellite galaxies over a 12-year time baseline, yielding uncertainties of ~1.8 mas/yr at 21 mag and ~3.0 mas/yr at 22 mag in the r band. The proper motions derived from bright and faint stars are consistent, indicating no significant variation in proper motion across stellar luminosity as these galaxies undergo tidal interactions with the MW. Meanwhile, we suggest that Bootes III represents the bound remnant of the progenitor galaxy that gave rise to the Styx stream, as evidenced by its elongated density profile and overdensity in both spatial and kinematic space. This is the first paper to use WFST to measure the proper motions of faint stars in Milky Way satellite galaxies. More detailed analyses will be presented in forthcoming papers from the wide field survey (WFS) program.

astro-ph.GA↗

arXiv2025

Balmer Decrement and IRX Break in Tracing Dust Attenuation at Scales of Individual Star-forming Regions in NGC 628

We investigate the relationships between infrared excess (IRX=$L_{\rm IR}/L_{\rm UV}$) and Balmer decrement (${\rm H}α/{\rm H}β$) as indicators of dust attenuation for 609 ${\rm {H\,{\small II}}}$ regions at scales of $\sim 50-200$ pc in NGC 628, utilizing data from AstroSat, James Webb Space Telescope (JWST) and Multi Unit Spectroscopic Explorer (MUSE). Our findings indicate that about three fifths of the sample ${\rm {H\,{\small II}}}$ regions reside within the regime occupied by local star-forming galaxies (SFGs) along the dust attenuation correlation described by their corresponding color excess parameters $E(B-V)_{\rm IRX} = 0.51\,E(B-V)_{{\rm H}α/{\rm H}β}$. Nearly 27$\%$ of the sample exhibits $E(B-V)_{\rm IRX}> E(B-V)_{{\rm H}α/{\rm H}β}$, while a small fraction ($\sim 13\%$) displays significantly lower $E(B-V)_{\rm IRX}$ compared to $E(B-V)_{{\rm H}α/{\rm H}β}$. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved ${\rm {H\,{\small II}}}$ regions. Furthermore, the ratio of $E(B-V)_{\rm IRX}$ to $E(B-V)_{{\rm H}α/{\rm H}β}$ remains unaffected by various physical parameters of the ${\rm {H\,{\small II}}}$ regions, including star formation rate (SFR), SFR surface density, infrared luminosity ($L_{\rm IR}$), $L_{\rm IR}$ surface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to galactic center. We argue that the ratio is primarily influenced by the evolution of surrounding interstellar medium (ISM) of the star-forming regions, transitioning from an early dense and thick phase to the late blown-away stage.

astro-ph.GA↗