Computer Vision
LAS-CLIP: A Lightweight Adapter Steering Approach for CLIP's Visual Encoder
Anh-Khoa Dinh-Duc, Duc-Tai Dinh, Tam V. Nguyen et al. (+1 more)
CLIP's visual encoder produces only global image representations, limiting its use in region-level tasks. Existing adaptations rely on visual prompting, input masking, or encoder fine-tuning, each compromising pre-trained representations. We propose LAS-CLIP, a Lightweight Adapter Steering approach that keeps every CLIP parameter frozen. A compact MaskAdapter generates per-head, per-layer
attention biases from an input mask and injects them into the frozen self-
attention layers, steering
attention toward the target region. Crucially, because the backbone remains strictly untouched, LAS-CLIP seamlessly reverts to vanilla CLIP when no mask is provided, preserving its foundational zero-shot capabilities. With approximately 116K to 145K trainable parameters and 100K training samples on two T4 GPUs, LAS-CLIP achieves competitive or superior results compared to Alpha-CLIP on ImageNet-S zero-shot classification and RefCOCO referring expression comprehension, despite the latter fine-tuning its entire encoder on millions of samples. Qualitative analysis further confirms stronger representational fidelity under incorrect masks and in downstream generation.
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All authors Anh-Khoa Dinh-Duc, Duc-Tai Dinh, Tam V. Nguyen, Minh-Triet Tran
Machine Learning · Cross-listed from q-fin.TR
Mixture-of-Experts for Cryptocurrency Order Execution: Training Stability, Tail Risk, and Failure Modes
Alexander Ardaiz, Varun Budati and Ali Habibnia
Deep reinforcement-learning policies for order execution can vary substantially across training seeds, so apparent architectural gains may reflect favourable training realisations rather than reproducible properties of the architecture. We evaluate vanilla Double Deep Q-Learning (DDQL), K-means-partitioned mixtures of DDQL experts at $K \in \{2, 4, 8\}$, and dense networks parameter-matched to the $K{=}4$ and $K{=}8$ expert budgets on 5-minute mean-aggregated BTC/USDT limit order book data from Binance. No learned configuration significantly improves mean implementation shortfall over DDQL. Under the reported specification, all have higher mean shortfall than TWAP (0.39 bps) and immediate liquidation (0.21 bps) in an environment whose frictionless replay and terminal-urgency penalty make early liquidation nearly costless; 11/100 vanilla-DDQL runs, versus none in either MoE $K{\geq}4$ arm, converge to a policy that waits until forced liquidation. We then decompose this specification on a device-matched baseline. Annealed exploration alone eliminates observed collapses (12/100 to 0/100; exact McNemar $p{=}4.9{\times}10^{-4}$), matching the elimination under expert partitioning. Combining annealed exploration with the aligned reward restores collapse in 19/30 runs; with all three specification changes, it rises to 48/100. In this environment, expert partitioning is unnecessary to suppress collapse and appears to mask a training-specification failure rather than confer an intrinsic performance benefit. No MoE $K{=}8$ run collapses under any of the six specifications tested. Across-seed dispersion is lowest at $K{=}8$ but non-monotone and not robust to family-wise adjustment, while within-policy tail risk worsens monotonically with $K$. The apparent attribution of the failure mode reverses between 30 and 100 seeds, illustrating the importance of repeated-seed evaluation.
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Artificial Intelligence
Multilingual GSM-Symbolic: What determines capability transfer across languages?
Kenneth Enevoldsen, Riley Herchert, Sofie Mosegaard et al. (+22 more)
We understand little about how capabilities acquired in one
language carry over to another, or what governs this transfer: evaluations rely on incomparable, saturation-prone
datasets and rarely examine its determinants jointly. Identifying what predicts transfer would let us avoid exhaustive evaluation across all
language pairs and let developers target the factors that limit performance in low-resource
languages. To evaluate cross-lingual capability transfer, we introduce
Multilingual GSM-Symbolic, an extensible
multilingual mathematical
dataset covering 30,000 item-matched question-answer pairs and spanning 15
languages. It utilises symbolic templates to prevent overfitting and ensure generalisation by allowing generation of millions of high-quality variations from a single sample. Using
Multilingual GSM-Symbolic, we quantify the largest determinants of capability as model size ($\beta = 1.77$),
language resource level ($\beta = 0.77$),
reasoning ($\beta = 0.67$) and typological distance ($\beta = -0.25$). This joint estimation allows these determinants to be expressed in terms of one another: a 32B model evaluated in Marathi performs like a 10B model in English. Our findings have important implications for model developers, showing that model size and
reasoning narrow the performance gap between low- and high-resource
languages ($\beta = -0.27$ and $\beta = -0.20$, respectively), while similar levers have little or no effect on typologically distant
languages. Overall, our analysis framework explains 92% of between-
language variation, but only 23% of the model-by-
language variation, and predicts a model's performance on an unseen
language within 6.0pp (r=.96). Incorporating measurements from just 10 templates in the target
language reduces this to 4.19pp, enabling reasonable estimates of performance with little or no downstream
dataset.
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All authors Kenneth Enevoldsen, Riley Herchert, Sofie Mosegaard, Dan Saattrup Smart, Simon Enni, Isaac Chung, Sofie Bruun, Ayush Sunil Munot, Max Müller-Eberstein, Adnan El-Assadi, Elisa Bassignana, Gianluca Barmina, Hafsteinn Einarsson, Iben Nyholm Debess, Linda Freienthal, Lukas Galke Poech, Mike Zhang, Nicolas Legrand, Vladimir Salnikov, Yevhen Kostiuk, Zafar Hussain, Sagandeep Kaur, Agnes Toftgård, Marie Mattson, Kristoffer Nielbo
Artificial Intelligence
Geometry Meets Physics: Data-Efficient Pre-Training for Unstructured Neural PDE Solvers
Luis Medrano-Navarro, Giacomo Baldan, Qiang Liu et al. (+4 more)
Neural surrogate models for Partial Differential Equations (PDEs) on unstructured 3D geometries are often limited by poor generalization and the high cost of generating large-scale training
datasets. Consequently, pre-training on massive
datasets of related PDE dynamics has emerged as a critical alternative to enhance the robustness and scalability of these models. However, this strategy is neither compute- nor data-efficient, as it relies on massive pre-computed data that is very costly to generate. In this work, we introduce a disk-data-free pre-training framework tailored to both steady-state and transient regimes. For steady-state problems, we propose a geometry-driven strategy that leverages intrinsic shape descriptors to learn representations of complex 3D domains. For transient problems, we introduce a physics-driven approach based on online generation of synthetic PDE data, enabling scalable pre-training without reliance on expensive
datasets. Across multiple experiments, our approach achieves faster convergence, greater data efficiency, and higher accuracy during fine-tuning, particularly under realistic low-data regimes. This methodology provides a practical pathway toward data-efficient neural emulators for large-scale simulations.
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All authors Luis Medrano-Navarro, Giacomo Baldan, Qiang Liu, Benjamin Holzschuh, Jan Hagnberger, Mathias Niepert, Nils Thuerey
Machine Learning
Follow the Winners: Conservative Policy Improvement with the Cross-Entropy Method for Critic-Free RFT
Joery Ariën de Vries, Neil David Lawrence and Zhenwen Dai
Critic-free reinforcement fine-tuning (RFT) for agentic large
language models is often done through GRPO-style methods, which compute a group baseline over repeated rollouts to reduce target variance. However, this setup is ill-suited to
agents acting in stateful environments such as live services or security sandboxes, where repeated rollouts are impractical to obtain and aggressive updates entrench the noise of long, sparsely verified trajectories. We propose Follow the Winners (FTW), a critic-free policy-learning
algorithm that adapts the cross-
entropy method to RFT, replacing group rollouts with an ordinal filter on replay-buffer samples that yields
polynomial concentration in the order statistic of returns. We derive FTW through a control-as-inference lens, which also recovers GRPO and DPO as specific modelling choices, identifying GRPO as risk-neutral while DPO and FTW share a bounded risk-seeking offset that FTW controls. We identify this offset as an inherent trade-off of variance reduction through ordinal filters on samples, whereas a critic model induces a different trade-off between bias and variance. Scaled to agentic LLM post-training, FTW matches GRPO and PPO on Sokoban and Search-R1 baselines, showing a viable trade-off from a value model or group rollouts to CPU
memory.
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Artificial Intelligence
ReFract: Benchmarking Perspective Awareness in Language Model Agents with Text World Models
Hainiu Xu, Vítor N. Lourenço, Mohnish Dubey et al. (+7 more)
Large
Language Model (LLM)
agents are increasingly deployed in high-stakes settings such as industrial maintenance and equipment fault troubleshooting, where workers occupy a variety of roles. A capable
agent must therefore act in a way that is calibrated to user's role: taking actions and providing information that respect the role's knowledge and capability boundaries. Unlike coding, where mistakes are usually recoverable,
agent responses in these settings are enacted on physical equipment, and can therefore cause irreversible equipment damage, production loss, or personnel harm. Existing
benchmarks, however, largely overlook the need for
agents to infer what a role intends and acting only through tools that role may legitimately use, a capability which we term Perspective Awareness. To this end, we introduce ReFract, a
benchmark of 150 expert-validated entries in which an
agent must act differently in response to the same query depending on user's role. Entries of ReFract are grounded in anonymized queries from domain support conversations, against which we construct Text World Models that simulate the
agent's operating environments and assemble perspective-aware action trajectories. State-of-the-art LLMs solve at most 69% of the tasks with more than 50% of their trajectories contain attempts of taking perspective-violating actions. ReFract exposes perspective awareness as a distinct, largely unsolved axis of
agent evaluation and motivates
agents that calibrate not just how to act, but for whom.
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All authors Hainiu Xu, Vítor N. Lourenço, Mohnish Dubey, Yunfei Bai, Yulan He, Caroline Catmur, Aline Paes, Marco Caserta, Akash Chandrayan, Luca D'Angelo
Logic in Computer Science
Symbolic Execution of Constrained Horn Clauses
Johannes Weiser, Zafer Esen and Philipp Rümmer
Constrained Horn clauses (CHCs) are a fragment of first-order logic widely used as an intermediate
language for verification. We study constrained resolution as a calculus for
reasoning about the satisfiability of sets of CHCs. Constrained resolution forms a simple alternative to model checking
algorithms such as CEGAR and IC3 and is here shown to exhibit complementary features. We show that, when CHCs encode programs, forward symbolic execution corresponds to positive unit hyper-resolution, and backward symbolic execution to SLD resolution, which are special cases of constrained resolution. We formalize forward and backward
reasoning for linear and non-linear CHCs and transition systems, prove refutational completeness under fair strategies, and develop subsumption criteria for
pruning redundant derivations. We moreover show that backward resolution with subsumption generalizes $k$-induction to non-linear CHCs, and that forward constrained resolution is related to the problem of constructing proofs in incorrectness logic. Lastly, we provide an experimental evaluation in the Eldarica CHC solver on
benchmarks from CHC-COMP.
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Information Theory
Low-Density Parity-Check Codes of High Girth from Permutation Polynomials
Tasawwar Hussain, Anthony Gómez-Fonseca and Tefjol Pllaha
Quasi-cyclic low-density parity-check (QC-LDPC) codes are widely used in modern communication standards due to their simple structure and efficient encoder and decoder implementations. However, the commutativity of the circulant permutation
matrices used in their construction significantly limits their girth and minimum distance, affecting iterative decoding performance. In this paper, we investigate protograph-based codes constructed using permutation
polynomials of higher degree, focusing on a closed family of non-commuting binomial permutation
polynomials that enables these constructions to exceed both of these girth and minimum distance upper bounds while maintaining a simple representation. Simulation results demonstrate improved decoding performance compared to constructions based on affine permutation
polynomials, which include QC-LDPC codes.
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Networking
Sparse Distributed Fiber Optic Sensor Placement in Metropolitan and Datacenter Elastic Optical Networks
Sleman Mouammar, Ítalo B. Brasileiro and André Drummond
Distributed Fiber Optical Sensing (DFOS) leverages optical backscattering signals to predict failure events and enable proactive Just-In-Time (JIT) restoration. Modern network infrastructures have optical components and fibers as key enablers of high throughput and low latency. The integration of sensing features in this optical infrastructure adds features such as network diagnosis, spatial positioning and sensing, and opens up opportunities for the implementation of intelligent network control expected for the next-generation networks. In this paper, we study how the quantity and the placement of the DFOS devices in an all-optical network can mitigate failure events. In our evaluation, we consider metropolitan and data center elastic optical networks. This work also evaluates sensing devices with various prediction time capabilities, in order to assess their effectiveness when considering a variable number of deployed devices and different placement heuristics. The evaluation uses key performance metrics, including the bandwidth blocking rate, number of affected
circuits by failure events, and the service downtime. Simulation results demonstrate that the Greedy Shortest Path Coverage (GSPC) heuristic substantially reduces the number of
circuits affected by failure when DFOS devices cover only 5% of links, while 25% coverage shows a performance gain comparable to the full coverage scenario, which is an opportunity for significant cost reduction. Finally, for the 5% sensing coverage scenarios, our results illustrate that prediction windows of 15 ms and 7.5 ms are sufficient for JIT restoration in metropolitan and data center networks, respectively.
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Information Theory
Randomization Beyond Deterministic Adaptivity in Parallel Sampling
Da Li, Bo Jin and Xiaopeng Wei
We study parallel samplers that reveal each coordinate once and draw the coordinates of each batch independently from their exact conditional marginals. Under the same sampling interface and a hard three-round cap, randomization can improve accuracy beyond every deterministic policy that adapts its batches to previously observed values. For an explicit full-support binary family, the optimal deterministic adaptive forward Kullback-Leibler divergence grows linearly with the dimension, while a uniform mixture of four fixed schedules has exponentially small divergence. Only two independent fair bits are needed to select the schedule. We determine the asymptotic additive constant in the deterministic optimum and show that its optimal total variation tends to one quarter. An outward-rounded finite-sum certificate establishes divergence separation at dimension 389. The mechanism combines an irreversible first-batch dependence loss with posterior concentration in the randomized components. A density-coverage lemma describes how their mixture restores the target. A complementary noisy-matching family exhibits a growing round gap for nonadaptive schedules, although uniform random coordinate order still has linear mixture error. These results concern known finite structures and exact conditional marginals.
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Computers and Society
A population-level assessment framework for flood-related wellbeing from public discourse in Ireland
Róisín Luo and Karyn Morrissey
\ textbf{Background.} Ireland's position on the eastern North Atlantic exposes it to moisture-laden westerlies and frequent low-pressure systems, generating abundant precipitation and substantial pluvial and fluvial flood risk.
Climate change is intensifying heavy rainfall and compound flood risk, with consequences extending beyond physical damage and conventional economic indicators. \ textbf{Method.} We present a framework for assessing flood-related wellbeing from unobtrusive public discourse over time. The framework develops an assessment instrument comprising three complementary constructs: distress, functional disruption, and institutional alienation, capturing flood-related impacts on affective appraisal, daily functioning, and social and institutional connectedness. To enable population-scale analysis of complex cognitive and psychological responses, we develop a dedicated flood-related wellbeing
reasoning model (Wellbeing-Former) that reads evidence of flood-related wellbeing, assigns evidence-grounded scores, and produces transparent rationales. Data, Results & Implications. Using the research platform MCL (Meta Content Library), we construct a flood-related discourse
dataset by querying posts from Ireland containing the terms flood, rain, and storm. The resulting
dataset comprises approximately \textbf{$224{,}000$} posts produced between 2012 and 2016. We apply the resulting Wellbeing-Former to this
dataset to conduct a population-level analysis. This approach provides temporally sensitive evidence of experienced and anticipated flood impacts, complements survey-based assessment, and supports a multidimensional understanding of wellbeing under
climate-related hazards for policy development, adaptation planning, public communication, and decision-making.
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Robotics
Equivariant Visual-Tactile Diffusion Policy for Contact-Rich Manipulation
Lik Hang Kenny Wong, Yiyao Ma, Xiu-Shen Wei et al. (+5 more)
Imitation learning for contact-rich manipulation requires high-quality expert data that is expensive to obtain. This makes learning a sample-efficient policy a key issue. To address this, we propose VISTA, a workspace-level equivariant visuotactile
diffusion policy for data-efficient contact-rich imitation learning. VISTA projects visual and tactile observations into spherical
tokens, injects tactile contact cues into visual spherical directions through permutation-equivariant spherical fusion, and rotates the fused harmonic representation using the end-effector orientation. The resulting representation conditions an equivariant
diffusion policy to predict spatially consistent actions. Extensive experiments in both simulation and real-world robotic settings show that VISTA substantially improves data efficiency over strong visuotactile imitation learning baselines. Project website: https://vista-paper.github.io/
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All authors Lik Hang Kenny Wong, Yiyao Ma, Xiu-Shen Wei, Zelong Tan, Zhuheng Song, Dongsheng Xie, Kai Chen, Qi Dou
Computer Vision
A Fully Automatic Pipeline for 3D Dendrite Instance Segmentation in SBF-SEM
Zewen Zhuo, Ilya Belevich, Eija Jokitalo et al. (+2 more)
Accurate three-dimensional (3D) reconstruction of individual dendrites in serial block-face scanning electron microscopy (SBF-SEM) is essential for quantifying structural plasticity in the
brain, yet manual annotation at scale is infeasible. We present a fully automatic pipeline for 3D dendrite instance
segmentation that unifies YOLOv6-guided Segment Anything Model (SAM) prompting on downsampled slices, iterative two-dimensional mask refinement, random forest 3D instance linking, and instance-aware high-resolution refinement using nnU-Net at native resolution into a single system requiring no manual prompting at inference. Applied to hippocampal CA1 SBF-SEM
datasets from a control rat and a pilocarpine- induced epileptic rat, our pipeline reconstructs coherent, well- separated dendrites with high semantic accuracy (Dice 0.93 and 0.91) and strong instance-level performance on control tissue, while analysis of the more challenging epileptic tissue identifies instance recognition in dense regions as the principal remaining limitation. The high-resolution refinement stage recovers thin dendritic protrusions, providing a basis for downstream spine- level analysis. Code is available at https://github.com/ ZE-WEN/dendrite-3d-instance-seg.
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All authors Zewen Zhuo, Ilya Belevich, Eija Jokitalo, Alejandra Sierra, Jussi Tohka
Machine Learning
Cordial Learning: Distributed Training with Correlated Data
Sarah Shitrit and Ilai Bistritz
We consider a distributed learning task with
agents that have correlated data. Specifically, the label of an
agent depends on the input of other
agents for the same sample, and these inputs are also correlated. Correlated data is the reality when
agents share the same environment. Existing decentralized methods, such as
federated learning, ignore the structure of the problem and perform poorly on correlated data. On the other hand, centralized approaches are infeasible due to
privacy and communication constraints. We introduce cordial (correlated and distributed) learning to address this gap by sharing only low-dimensional outputs between the
agents while training local models to extract informative signals from peers. This distributed learning induces a game in which the loss function of each
agent depends on the models of others. Assuming a linear model, we prove that cordial learning converges with probability one to a globally optimal solution, despite the nonconvex global objective. Experiments on structured multi-digit MNIST tasks demonstrate that cordial learning remains highly effective even in highly nonlinear settings.
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Computation and Language
SyntaxBench: A Statistical Diagnostic Framework for Character-Level Reasoning in Large Language Models
Mohsen Larni, Sobhan Ebrahimi Azar, Pouyan Nahed et al. (+1 more)
Large
language models are increasingly used where small syntactic errors matter, yet character-level
reasoning is still evaluated mostly through isolated probes and aggregate accuracy. We introduce SyntaxBench, a diagnostic
benchmark and statistical evaluation framework for character-level
reasoning. It contains five core tasks, character counting, letter containment, palindrome detection, edit distance, and longest-string selection, plus index_to_span, a harder substring-extraction stress test. The five core tasks use paired English and character-length-matched random-string inputs. index_to_span documents share a 200-500 word band and are not character-length matched. All six tasks use zero-, one-, and four-shot
prompts. We evaluate eight open-weight models from 2B to 32B parameters across 11
reasoning-mode configurations. The framework reports exact-match and relaxed accuracy, Cohen's kappa, paired McNemar tests with odds ratios, bootstrap confidence intervals, Kendall's tau, class-conditional metrics, tokenization analysis, and multiple-comparison-corrected tests. Three findings stand out. First, tokenization shapes accuracy: random strings are more character-visible than English strings (1.892 vs. 3.169 characters per
token), and character-counting accuracy falls as English words occupy more
tokens. Second,
reasoning mode is not uniformly helpful: Gemma4-31B is nearly unchanged across modes on the near-saturated tasks, while Qwen3.6-27B is worse with thinking on palindrome detection (0.952 non-thinking vs. 0.886 thinking at four-shot). Third, index_to_span remains largely unsolved; the best four-shot exact-match accuracy is 6.75%. Character-level evaluation needs controlled inputs, paired tests, and analyses of tokenization and
reasoning mode rather than aggregate accuracy alone.
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All authors Mohsen Larni, Sobhan Ebrahimi Azar, Pouyan Nahed, Kazem Taghva
Computational Engineering
Reformulating plastic instabilities within a damage-like variational framework
Baptiste Reyne
Yield point phenomena in metals, anticracks in soils and snows, or planewise collapses in
lattice metamaterials, are different manifestations of plastic instabilities characterized by stress softening and strain localization. Several independent constitutive descriptions exist and suffer from similar challenges: experimental difficulties to link local events to global measurements, and computational lack of convergence, spurious localization and mesh sensitivity. This work proposes a minimal field-agnostic constitutive framework where plastic softening is represented by a damage-like internal variable which explicitly separates stable hardening behavior from unstable softening. The resulting formulation admits a variational structure and can leverage regularization tools originally developed by the ductile fracture community. The framework aims at emphasizing similarities within plastic instability phenomena and establishing a bridge with continuum damage mechanics, to open a path towards regularized variational formulations of localized plastic flows.
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Artificial Intelligence
Preserving Mathematical Reasoning in Compressed Diffusion Language Models via Trajectory-Aware Low-Rank Approximation
Tian Liang, Zishan Shao and Yiran Chen
Diffusion language model (dLLM) compression faces a known challenge because calibration is typically performed on clean, fully visible activations, whereas inference traverses partially masked intermediate states. For low-rank compression, this raises two questions. First, can low-rank optimality still be characterized when approximation quality is measured over trajectory-distributed states, and second, does the choice of calibration states affect mathematical
reasoning preservation under compression? We address these questions by formulating a trajectory-aware low-rank objective over corruption levels and masking realizations. To estimate this objective efficiently, we propose Traj-MC, which estimates the trajectory second moment through Monte Carlo sampling and yields exact sampled-state optimality and population consistency. Under matched compression budgets, trajectory-aware calibration improves reconstruction over the generation trajectory and preserves substantially more mathematical
reasoning than clean calibration on mathematical
reasoning benchmarks. Our results connect trajectory-aware low-rank optimality to the
reasoning capability retained after dLLM compression. Our code is available at: https://github.com/Zishan-Shao/traj-mc.git.
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Numerical Analysis
Energetic Variational Deep Learning for Solving High-Dimensional Stationary Fokker-Planck Equations
Fanze Kong, Zhouyuan Qin and Shuangquan Xie
This paper develops a deep learning framework for solving high-dimensional stationary Fokker-Planck equations by combining Monte Carlo weak supervision, energy-variational physics constraints, and quasi-Newton refinement. Monte Carlo statistics anchor the scale of the stationary density, while a free-energy variational loss enforces
equilibrium physics; the formulation also applies to stationary systems with pointwise orthogonal rotational components and, using a family of test functions, to systems with more general non-gradient drift. Numerical results demonstrate accurate and robust density approximations across a range of high-dimensional stationary Fokker-Planck problems, including rough-potential and noisy-data settings.
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Computation and Language
To Jev or Not? Evaluating the Accuracy and Efficiency of Structured Decision Models for Hate-Speech Moderation
Demetris Paschalides, George Pallis and Marios D. Dikaiakos
The scale of online content makes hate-
speech moderation challenging, while Large
Language Models (LLMs) enable harmful material to be produced and adapted more easily. Moderation therefore requires efficient classifiers that can accommodate different definitions of hate
speech. Recent structured decision models accept natural-
language criteria and select among specified answers, raising the question of whether they can meet these requirements without task-specific training. We present HATEDECIDE, an evaluation of six decision-model configurations on four hate-
speech datasets against specialized moderation, zero-shot, commercial, and supervised baselines. We examine whether supplying a
dataset's definition, or decomposing it into multiple questions, improves classification, and we measure their latency and cost. We find that commercial LLMs significantly outperform all decision models on only one
dataset. Supplying definitions changes up to 28% of predictions without consistently improving classification, and decomposition significantly improves performance in only 20% of the comparisons. On a diagnostic set of test cases, the best hosted decision model comes within 1.6 macro-F1 points of the best commercial LLM at approximately 97% lower inference cost. These results identify opportunities for inexpensive moderation, while showing that explicit criteria and additional questions do not reliably improve classification.
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Artificial Intelligence · Cross-listed from math.OC
Information Limits of Low-Rank Approximation Certification
Kang Liu and Bohao Qu
Low-rank approximation can require additional
matrix–vector products to verify that its error meets a prescribed tolerance. We characterize this certification cost for both relative
matrix error and mean-square output error. For a single approximation
matrix candidate, we determine the exact dimension-uniform minimax query constant as the allowed failure probability vanishes. Our main result concerns reusing validation responses as the approximation space expands. For a candidate family constructed independently of validation, one batch supports an entire nested path without increasing the query budget with the number of checks. Across \(W\) paths, a concentration bound exploiting shared residual energy yields a \(\sqrt{\log(W+1)}\) dependence. A matching lower bound establishes its optimality for fixed interior error targets and sufficiently small separation gaps. Finally, we compare two uniformly valid certificates on the same dispersed-spectrum family. Optimizing the validation budget within each rule family yields costs of orders \(N^{1/3}\) and \(N^{2/3}\) for validation and construction beyond the true target. Code is available at https://anonymous.4open.science/r/Low-rank-approximation-1275/
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Artificial Intelligence
Refinement Buys Intelligibility, Search Buys Identity: What Test-Time Compute Buys in Masked-Diffusion TTS
Nityanand Mathur, Hamees Sayed and Ayush Pratap Singh
Diffusion language models for text-to-
speech combine two forms of computation: model depth (parameters) and refinement steps (inference budget). We ask whether they scale equally across capabilities. We train 15 masked-
diffusion codec TTS models varying depth (19-133M parameters, 3 seeds) on 2,000 hours of
speech and sweep refinement steps T in [1,16] at inference, measuring zero-shot synthesis via ASR word error rate (intelligibility) and speaker verification (identity) on 174 held-out speakers. Against measured floors, refinement closes 86.2% of the intelligibility range but only 46.4% of the identity range - a 1.86x asymmetry robust across multiple error metrics. Retraining at 3x and 6x schedule attenuates but does not reverse this gap (1.84 to 1.36 to 1.23x), because intelligibility saturates with steps while identity continues improving. Best-of-K search recovers speaker identity where refinement fails, with 64.6-79.0% win rates across four independent encoders. Depth and steps are not interchangeable: separable B(d)B(T) fits significantly better (Delta AICc=+69.3) than substitution models. Analysis shows 62% of remaining identity deficit lies in the codec, not the generator. We conclude that refinement and depth target different bottlenecks and should be optimized separately.
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Cryptography and Security
Defense-in-Depth at the Perception-Reasoning Interface of LLM-Centric Agentic UAV Swarms
Mohammadhossein Homaei, Yousef Emami, Sajad Homayoun et al. (+4 more)
Large
Language Models (LLMs) increasingly support Uncrewed Aerial Vehicle (
UAV) swarm operations such as data collection scheduling, where the model reads structured sensor reports and decides which sensors to visit. An adversary who quietly manipulates those reports can redirect the swarm without modifying the model weights or the
UAV. Defenses for this interface have been proposed architecturally but rarely implemented or evaluated. We implement and evaluate defense-in-depth at the perception-
reasoning interface of LLM-Centric Agentic
UAV Swarms. Five layers check the provenance of a report, whether its values are physically admissible, whether they agree with what swarm geometry and service history predict, whether the resulting schedule starves any sensor, and, when these fail, hand control to a deterministic scheduler that ignores the suspect input. We test each layer against an adversary strong enough to defeat the layer before it. For each of the three input-side layers, we derive in closed form how far a report can be distorted before that layer reacts, fixing each boundary from deployment parameters before any attack data is collected; across thirty matched simulation runs, predicted and measured boundaries agree. Separating attack detection from response is a well-established principle, and we quantify the cost of neglecting this distinction at the perception-
reasoning interface. When the system rejects a report, it replaces it with the most recent accepted report. This prevents the adversary from controlling the
UAV schedule, but it also increases cumulative cost by 79% and 74% for the two detectors, respectively, compared with the undefended system. The safety check does not detect any attacks, but it nevertheless reduces the attack-induced cost by 37.5%.
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All authors Mohammadhossein Homaei, Yousef Emami, Sajad Homayoun, Rahim Taheri, Hao Zhou, Miguel Gutierrez Gaitan, Bo Wei
Numerical Analysis
Fully mixed finite element methods for the coupling of viscoelasticity and reaction-diffusion models
Alonso J. Bustos, Jeonghun J. Lee and Ricardo Ruiz-Baier
We propose and analyse a fully mixed finite element method for a two-way coupled mechanochemical model of calcium signalling in viscoelastic tissue. The mechanical response follows a Kelvin–Voigt law, with the elastic and viscous stresses, velocity, and
spin tensor as unknowns, and the
symmetry of the total stress imposed weakly. The reaction-
diffusion system for calcium and inactivated inositol triphosphate is also formulated in mixed form, introducing the diffusive flux as an additional unknown. The coupling is bidirectional: calcium generates an active stress, while local dilation feeds back into the calcium dynamics. We establish global existence and uniqueness by reducing the coupled system to an integro-differential problem and subsequently recovering the mixed variables. The semidiscrete scheme is formulated for general conforming finite element spaces and shown to be well posed under a single inf-sup condition. An interpolation operator that commutes with the divergence and preserves the weak
symmetry pairing yields optimal a priori error estimates. We specialise the analysis to three families of weakly symmetric finite elements, deriving explicit convergence rates and, for one family, a superconvergent local post-processing of the displacement. Numerical tests in two and three dimensions confirm the predicted convergence rates and illustrate the method through viscoelastic
benchmarks and mechanically driven calcium wavetrains.
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Artificial Intelligence
Multi-Task Evolution for Zero-Shot Cross-Problem Generalization using LLMs
Zhuoliang Xie, Changliang Zhou, Genghui Li et al. (+1 more)
Designing effective heuristics for diverse combinatorial optimization problems requires substantial expertise and repeated search. Large
language models (LLMs) automate heuristic generation and refinement, but heuristic search typically depends on evaluation feedback from the problem being optimized. Generalizing to new problem definitions using only source-task feedback therefore remains a central challenge. We introduce MECo, an LLM-driven multi-task evolutionary framework for zero-shot cross-problem generalization. MECo maintains task-conditioned heuristic populations and uses a transfer gap based on cross-task population performance to guide their interactions. These interactions enable the transfer and recombination of heuristics. A complementary selection criterion then constructs a compact heuristic set by rewarding each member's additional coverage of source combinations. The selected set is applied to target problems without further search or adaptation. Experiments on 32 problem variants across vehicle routing (VRP) and flexible job-shop scheduling (FJSP) show that MECo achieves the lowest mean costs compared with eight automated heuristic design (AHD) baselines under the same budgets. On out-of-domain problems, it outperforms the strongest baseline in each family. Moreover, integrating the framework of MECo with different AHD methods improves their ID and OOD performance in both families, supporting its effectiveness across different methods.
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All authors Zhuoliang Xie, Changliang Zhou, Genghui Li, Zhenkun Wang
Artificial Intelligence
Lightweight, Rubric-Guided Trajectory Evaluation for Production AI Agents
Linh-An Phan, MingXue Wang, Guangyu Wu et al. (+3 more)
Trajectory evaluation is essential for improving the reliability of LLM-based
agents, but production use makes it expensive to run repeatedly. Modern
agents generate long traces containing tool calls, observations, retries, and external outputs, while not all raw
tokens are equally useful for diagnosis. We present LiteTrajEval, a lightweight architecture for budget-bounded trajectory evaluation. LiteTrajEval derives compact domain-specific rule profiles offline, then preprocesses each trajectory online, marks heuristic failure signals, serializes it under a fixed global budget, and invokes a single rubric-guided LLM judge to produce structured diagnostic reports. Evaluated on public Magentic-One-style and $\tau$-bench-style trajectory
datasets, LiteTrajEval improves failure-localization
alignment with human annotations by roughly 20–35 percentage points on Magentic-One and up to 23 percentage points on $\tau$-retail compared with AgentRx, while reducing cost by about 6$\times$ and evaluation time by more than 8$\times$. This solution has also been deployed in our enterprise agentic platform.
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All authors Linh-An Phan, MingXue Wang, Guangyu Wu, Feng Pan, Zhaoyu Pang, Yanbin Zhang
Machine Learning · Cross-listed from stat.ML
DAWIS: Data Assimilation with Windowed Inverse Sampling via Multitask Interpolants
Erik Wikingsson, Martin Andrae, Tomas Landelius et al. (+1 more)
Flow- and
diffusion-based generative models have recently emerged as flexible and highly efficient
forecasting models for dynamical systems. When combined with inference-time guidance, they offer a promising route to high-dimensional non-Gaussian data assimilation (DA), the problem of combining forecasts with observations to estimate latent system states. Existing filters, however, condition on a fixed history and assimilate only the most recent observation, leaving them unable to revise past states when new observations arrive. Estimates then stay tethered to a history that later observations may contradict, and errors accumulate over the assimilation run. To this end, we introduce **DAWIS**, a unified DA method covering filtering, fixed-lag smoothing, and block smoothing within a single framework. DAWIS replaces the single flow time of a state-level prior with a multitask
stochastic interpolant over a window of consecutive states, assigning a separate flow time to each. An assimilation cycle inverts the window to a vector of per-state turning points and regenerates it under observation guidance, with the turning points controlling how strongly each state is held fixed, revised, or generated from scratch. The same construction can also absorb the forecast into the assimilation cycle, removing the need for a separate
forecasting model. Experiments on challenging nonlinear systems show that DAWIS improves on both filtering and smoothing baselines under sparse, noisy, and nonlinear observations. The code for DAWIS is available at https://github.com/Erik-Wikingsson/DAWIS
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All authors Erik Wikingsson, Martin Andrae, Tomas Landelius, Fredrik Lindsten
Machine Learning · Cross-listed from stat.ML
SDECast: Probabilistic Weather Forecasting in Continuous Time with Neural SDEs
Maria Marchenko, Martin Andrae, Fredrik Lindsten et al. (+1 more)
Existing machine learning weather
forecasting models typically generate forecasts through autoregressive rollouts at a fixed temporal resolution. While highly efficient for long-range prediction, this formulation can suffer from severe error accumulation when used with shorter time steps and does not explicitly encode the locality and temporal continuity of atmospheric dynamics. To address these limitations, we introduce **SDECast**, a Neural
Stochastic Differential Equation (SDE) framework for continuous-time probabilistic weather
forecasting. SDECast extends SDE Matching to learn
stochastic dynamics directly in physical space, without requiring repeated SDE simulation during training. On a simulated geophysical flow, we show that SDECast recovers meaningful drift dynamics and faithfully reproduces the underlying continuous-time behavior. We then demonstrate its scalability to global weather
forecasting at hourly resolution, where SDECast produces skillful probabilistic forecasts for lead times of up to five days.
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All authors Maria Marchenko, Martin Andrae, Fredrik Lindsten, Christian A. Naesseth
Artificial Intelligence
Optimal Planning in a Dynamic World
Devin Wild Thomas, Solomon Eyal Shimony, Wheeler Ruml et al. (+3 more)
Background: We address the problem of planning when the set of feasible states or actions changes over time. For example, in the problem of path planning among moving obstacles (sometimes known as SIPP), the feasibility of being at a particular location can change as the obstacles move. Or, the action of boarding a particular train is feasible only while it is stopped at the station. This dynamism means that the optimal plan and its duration can change depending on when execution begins. In practice, execution start time is often unknown until planning has completed or another
agent gives the go-ahead. However, most prior planning work either ignores dynamism or assumes a known start time. This makes it straightforward to assess state and action feasibility but is impractical for some applications. Objectives: In this paper, we relax the assumption of a known start time. We define the setting of any-start-time planning and provide
algorithms for it. Methods: We present a data structure called a compound arrival time function (cATF) that compactly encodes the optimal plan as a function of start time. We provide general-purpose planning
algorithms, based on heuristic graph search, that assemble cATFs by propagating functions along edges instead of scalar costs. Results: We prove that the size of a cATF is at most linear in the problem size. An experimental evaluation of an implementation for the specific problem of SIPP shows that, on difficult problems,
agents that rely on replanning often fail, while any-start-time
algorithms using cATFs can quickly look up the optimal plan once the execution start time is known. Conclusions: By enabling efficient representations and
reasoning for time-dependent plans, this work provides a foundation for planning in dynamic worlds.
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All authors Devin Wild Thomas, Solomon Eyal Shimony, Wheeler Ruml, Erez Karpas, Shahaf S. Shperberg, Andrew Coles
Computer Vision
T3lescope: Arbitrary-Resolution High-Fidelity Generative Surface Reconstruction from Images
Atsuhiro Noguchi, Tianhan Xu, Yiming Liang et al. (+5 more)
We reconstruct high-fidelity 3D scene meshes from posed multi-view images without per-scene optimization, across scales ranging from single objects to large outdoor scenes. Per-scene optimization methods lack the learned 3D prior needed when observations are sparse or surfaces are glossy or transparent. Existing generative methods leverage such priors to complete geometry in sparsely observed regions, but typically operate at a fixed resolution over a limited spatial extent, trading spatial coverage against detail. Reconstructing a large scene therefore often requires partitioning it into independently processed overlapping local regions, making it difficult to maintain global
geometric consistency. To address these issues, we propose T3lescope, which applies a single fixed-resolution generator across scene scales in an inference-time coarse-to-fine cascade. A coarse level establishes the scene layout, and finer levels perturb and denoise geometry inherited from the coarser level within progressively finer spatial
cells to recover surface detail. The model is trained on individual
cells at multiple scales and shares its weights across all levels, so no hierarchy is fixed during training, and the number of levels,
cell scales, and
cell locations are determined at inference time. On indoor, outdoor, and city-scale scenes, T3lescope outperforms feed-forward and generative baselines, matches or surpasses per-scene optimization, and recovers fine structures as well as glossy and transparent surfaces. These results show that our method generalizes across diverse scenes, view counts, and image resolutions. Project page: https://pfnet-research.github.io/t3lescope/
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All authors Atsuhiro Noguchi, Tianhan Xu, Yiming Liang, Yuta Kikuchi, Masahiro Ishiyama, Shintaro Takagi, Hitoshi Murai, Eiichi Matsumoto
Machine Learning
Training-Loss Guarantees for Muon with Finite-Step Newton–Schulz Orthogonalization
Amartya Roy and Souvik Chakraborty
Existing convergence analyses of
Muon either assume exact orthogonalization or analyze classical Newton–Schulz
polynomials, and guarantee only stationarity, so it is unresolved what
Muon's five tuned Newton–Schulz steps preserve and whether that suffices to reach a prescribed neural-network training loss. We establish a finite-time training guarantee that accounts for both momentum accumulation before orthogonalization and the tuned finite-step update. For full-batch training of a sufficiently wide two-layer ReLU network with fixed random output weights and a positive-definite limiting neural tangent kernel, we prove that
Muon reaches any target empirical squared loss $\varepsilon>0$ with high probability over initialization. For every momentum parameter $\mu\in[0,1)$, a target-dependent constant learning rate proportional to $(1-\mu)\sqrt{\varepsilon}$ yields a hitting-time bound of $O((1-\mu)^{-1}\varepsilon^{-1/2})$, with other problem parameters fixed. The sufficient width is independent of both target accuracy and momentum. The analysis shows that the tuned Newton–Schulz map preserves
alignment with the momentum buffer while bounding the update's spectral norm. Control of gradient variation near initialization transfers this
alignment to the current gradient, ensuring descent until the target is reached without requiring exact orthogonalization. Numerical experiments support these mechanisms at widths below the sufficient theoretical threshold: gradient-update
alignment remains above the analytical reference, and all 30 runs across six widths and five student initializations on a fixed teacher-student
dataset reach the target loss while maintaining kernel positivity.
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