University of Helsinki
This research provides a rigorous theoretical investigation into the continuous discretization of neural operators, demonstrating a fundamental topological obstruction that prevents general diffeomorphisms in Hilbert spaces from always being continuously approximated by finite-dimensional ones. It constructively shows that strongly monotone or bilipschitz neural operators, however, do permit continuous discretization, offering conditions for their design.
Researchers from the University of Jyväskylä and collaborators developed a hybrid deep transfer learning and ensemble machine learning model that achieves 96.74% accuracy on an external test set for colorectal cancer histology decomposition. This approach provides a more precise foundation for imaging-based prognostic biomarkers by enhancing tissue classification compared to previous methods.
We present observations and analysis of the starburst, PACS-819, at z=1.45 (M=1010.7M_*=10^{10.7} M_{ \odot}), using high-resolution (0.10^{\prime \prime}.1; 0.8 kpc) ALMA and multi-wavelength JWST images from the COSMOS-Web program. Dissimilar to HST/ACS images in the rest-frame UV, the redder NIRCam and MIRI images reveal a smooth central mass concentration and spiral-like features, atypical for such an intense starburst. Through dynamical modeling of the CO J=5--4 emission with ALMA, PACS-819 is rotation-dominated thus has a disk-like nature. However, kinematic anomalies in CO and asymmetric features in the bluer JWST bands (e.g., F150W) support a more disturbed nature likely due to interactions. The JWST imaging further enables us to map the distribution of stellar mass and dust attenuation, thus clarifying the relationships between different structural components, not discernable in the previous HST images. The CO J = 5 -- 4 and FIR dust continuum emission are co-spatial with a heavily-obscured starbursting core (<1 kpc) which is partially surrounded by much less obscured star-forming structures including a prominent arc, possibly a tidally-distorted dwarf galaxy, and a clump, either a sign of an ongoing violent disk instability or a recently accreted low-mass satellite. With spatially-resolved maps, we find a high molecular gas fraction in the central area reaching 3\sim3 (MgasM_{\text{gas}}/MM_*) and short depletion times (Mgas/SFRM_{\text{gas}}/SFR\sim 120 Myrs) across the entire system. These observations provide insights into the complex nature of starbursts in the distant universe and underscore the wealth of complementary information from high-resolution observations with both ALMA and JWST.
California Institute of Technology logoCalifornia Institute of TechnologyUniversity of OsloUniversity of Cambridge logoUniversity of CambridgeUniversity of VictoriaChinese Academy of Sciences logoChinese Academy of SciencesUniversity of ZurichTel Aviv University logoTel Aviv UniversityUniversity of Oxford logoUniversity of OxfordUniversity of Science and Technology of China logoUniversity of Science and Technology of ChinaScuola Normale SuperioreUniversity of Copenhagen logoUniversity of CopenhagenUniversity of EdinburghThe University of Texas at Austin logoThe University of Texas at AustinINFN logoINFNETH Zürich logoETH ZürichYonsei UniversityUniversity of CreteKavli Institute for the Physics and Mathematics of the UniverseUniversität HeidelbergUniversity of Maryland logoUniversity of MarylandUniversidad Autónoma de MadridUniversité Paris-Saclay logoUniversité Paris-SaclayStockholm University logoStockholm UniversityUniversity of HelsinkiUniversity of Arizona logoUniversity of ArizonaUniversity of Western AustraliaUniversity of SheffieldPrinceton University logoPrinceton UniversityUniversity of GenevaUniversity of PortsmouthUniversity of IcelandUniversità di GenovaUniversidade do PortoUniversity of SussexINAFAix Marseille UniversityNiels Bohr InstituteUniversity of JyväskyläUniversity of PadovaJet Propulsion LaboratoryJagiellonian UniversityInstituto de Astrofísica de CanariasUniversity of the WitwatersrandUniversity of NottinghamEuropean Space AgencyUniversity of Cape TownSISSANicolaus Copernicus Astronomical CenterObservatoire de la Côte d’AzurUniversity of Hawai’iUniversity of KwaZulu-NatalLudwig-Maximilians-UniversitätLaboratoire d’Astrophysique de MarseilleINAF-Istituto di RadioastronomiaINAF – Osservatorio Astronomico di RomaInstitut de Física d’Altes Energies (IFAE)Laboratoire de Physique des 2 Infinis Irène Joliot-CurieOsservatorio Astronomico della Regione Autonoma Valle d’AostaINAF - Osservatorio Astrofisico di CataniaINAF - Osservatorio Astronomico di ArcetriInstitut d’Astrophysique SpatialeNASADTU SpaceThe Queen’s University of BelfastInstituto de Astrofísica e Ciências do Espaço, Universidade de LisboaIRAP, Université de Toulouse, CNRS, CNESETH, Institute for AstronomyINAF-IASF, BolognaCosmic Dawn Center(DAWN)Universit degli Studi di FerraraUniversit de ParisUniversit Claude Bernard Lyon 1Excellence Cluster ‘Origins’Universit de LyonUniversit di PisaIFCA-CSIC-UCINAF Osservatorio Astronomico di PadovaUniversit degli Studi di FirenzeUniversit de MontpellierUniversit degli Studi di Napoli Federico IIUniversit di Roma Tor VergataINAF Osservatorio di Astrofisica e Scienza dello Spazio di BolognaUniversit Di BolognaINAF ` Osservatorio Astronomico di TriesteUniversit degli Studi di Trieste
Verifying the fully kinematic nature of the cosmic microwave background (CMB) dipole is of fundamental importance in cosmology. In the standard cosmological model with the Friedman-Lemaitre-Robertson-Walker (FLRW) metric from the inflationary expansion the CMB dipole should be entirely kinematic. Any non-kinematic CMB dipole component would thus reflect the preinflationary structure of spacetime probing the extent of the FLRW applicability. Cosmic backgrounds from galaxies after the matter-radiation decoupling, should have kinematic dipole component identical in velocity with the CMB kinematic dipole. Comparing the two can lead to isolating the CMB non-kinematic dipole. It was recently proposed that such measurement can be done using the near-IR cosmic infrared background (CIB) measured with the currently operating Euclid telescope, and later with Roman. The proposed method reconstructs the resolved CIB, the Integrated Galaxy Light (IGL), from Euclid's Wide Survey and probes its dipole, with a kinematic component amplified over that of the CMB by the Compton-Getting effect. The amplification coupled with the extensive galaxy samples forming the IGL would determine the CIB dipole with an overwhelming signal/noise, isolating its direction to sub-degree accuracy. We develop details of the method for Euclid's Wide Survey in 4 bands spanning 0.6 to 2 mic. We isolate the systematic and other uncertainties and present methodologies to minimize them, after confining the sample to the magnitude range with negligible IGL/CIB dipole from galaxy clustering. These include the required star-galaxy separation, accounting for the extinction correction dipole using the method newly developed here achieving total separation, accounting for the Earth's orbital motion and other systematic effects. (Abridged)
We develop a sieve that can detect primes in multiplicatively structured sets under certain conditions. We apply it to obtain a new LL-function free proof of Linnik's problem of bounding the least prime pp such that $p\equiv a\pmod q(withthebound (with the bound p \ll q^{350})aswellasanew) as well as a new L$-function free proof that the interval (xx39/40,x](x-x^{39/40}, x] contains primes for every large xx. In a future work we will develop the sieve further and provide more applications.
UrbanLLaVA is a multi-modal large language model designed for comprehensive urban intelligence, unifying understanding and reasoning across street view, satellite images, structured geospatial data, and trajectory data. The model achieves superior performance across diverse urban tasks on a new benchmark and demonstrates cross-city transferability.
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A comprehensive survey from Tsinghua University examines how large language models enable spatial intelligence across three scales - embodied agents, smart cities, and Earth science applications - while establishing connections between cognitive science principles and practical implementations through a unified analytical framework.
Designing and optimizing task-specific quantum circuits are crucial to leverage the advantage of quantum computing. Recent large language model (LLM)-based quantum circuit generation has emerged as a promising automatic solution. However, the fundamental challenges remain unaddressed: (i) parameterized quantum gates require precise numerical values for optimal performance, which also depend on multiple aspects, including the number of quantum gates, their parameters, and the layout/depth of the circuits. (ii) LLMs often generate low-quality or incorrect quantum circuits due to the lack of quantum domain-specific knowledge. We propose QUASAR, an agentic reinforcement learning (RL) framework for quantum circuits generation and optimization based on tool-augmented LLMs. To align the LLM with quantum-specific knowledge and improve the generated quantum circuits, QUASAR designs (i) a quantum circuit verification approach with external quantum simulators and (ii) a sophisticated hierarchical reward mechanism in RL training. Extensive evaluation shows improvements in both syntax and semantic performance of the generated quantum circuits. When augmenting a 4B LLM, QUASAR has achieved the validity of 99.31% in Pass@1 and 100% in Pass@10, outperforming industrial LLMs of GPT-4o, GPT-5 and DeepSeek-V3 and several supervised-fine-tuning (SFT)-only and RL-only baselines.
Researchers from Tsinghua University developed GlODGen, a commuting origin-destination (OD) flow generator for global cities that utilizes publicly available satellite imagery and population data. The system achieves over 90% of the performance of models relying on traditional, resource-intensive urban features and demonstrates strong cross-continental generalization for producing high-quality mobility data.
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Large language models (LLMs) have achieved remarkable outcomes in complex problems, including math, coding, and analyzing large amounts of scientific reports. Yet, few works have explored the potential of LLMs in quantum computing. The most challenging problem is to leverage LLMs to automatically generate quantum circuits at a large scale. Fundamentally, the existing pre-trained LLMs lack the knowledge of quantum circuits. In this paper, we address this challenge by fine-tuning LLMs and injecting the domain-specific knowledge of quantum computing. We describe Agent-Q, an LLM fine-tuning system to generate and optimize quantum circuits. In particular, Agent-Q implements the mechanisms to generate training data sets and constructs an end-to-end pipeline to fine-tune pre-trained LLMs to generate parameterized quantum circuits for various optimization problems. Agent-Q provides 14,000 quantum circuits covering a large spectrum of the quantum optimization landscape: 12 optimization problem instances and their optimized QAOA, VQE, and adaptive VQE circuits. Based thereon, Agent-Q fine-tunes LLMs and constructs syntactically correct parametrized quantum circuits in OpenQASM 3.0. We have evaluated the quality of the LLM-generated circuits and parameters by comparing them to the optimized expectation values and distributions. Experimental results show superior performance of Agent-Q, compared to several state-of-the-art LLMs and better parameters than random. Agent-Q can be integrated into an agentic workflow, and the generated parametrized circuits with initial parameters can be used as a starting point for further optimization, e.g., as templates in quantum machine learning and as benchmarks for compilers and hardware.
Amortized simulator-based inference offers a powerful framework for tackling Bayesian inference in computational fields such as engineering or neuroscience, increasingly leveraging modern generative methods like diffusion models to map observed data to model parameters or future predictions. These approaches yield posterior or posterior-predictive samples for new datasets without requiring further simulator calls after training on simulated parameter-data pairs. However, their applicability is often limited by the prior distribution(s) used to generate model parameters during this training phase. To overcome this constraint, we introduce PriorGuide, a technique specifically designed for diffusion-based amortized inference methods. PriorGuide leverages a novel guidance approximation that enables flexible adaptation of the trained diffusion model to new priors at test time, crucially without costly retraining. This allows users to readily incorporate updated information or expert knowledge post-training, enhancing the versatility of pre-trained inference models.
Test-time scaling (TTS) has enhanced the performance of Reasoning Models (RMs) on various tasks such as math and coding, yet its efficacy in machine translation (MT) remains underexplored. This paper investigates whether increased inference-time computation improves translation quality. We evaluate 12 RMs across a diverse suite of MT benchmarks spanning multiple domains, examining three scenarios: direct translation, forced-reasoning extrapolation, and post-editing. Our findings show that for general-purpose RMs, TTS provides limited and inconsistent benefits for direct translation, with performance quickly plateauing. However, the effectiveness of TTS is unlocked by domain-specific fine-tuning, which aligns a model's reasoning process with task requirements, leading to consistent improvements up to an optimal, self-determined reasoning depth. We also find that forcing a model to reason beyond its natural stopping point consistently degrades translation quality. In contrast, TTS proves highly effective in a post-editing context, reliably turning self-correction into a beneficial process. These results indicate that the value of inference-time computation in MT lies not in enhancing single-pass translation with general models, but in targeted applications like multi-step, self-correction workflows and in conjunction with task-specialized models.
Conventional understandings of quantum theory hold that measurements change the state of an observed system following the Lüders update rule. Textbooks describe the application of this idea to non-relativistic systems, but extensions to relativistic and gravitating systems encounter subtleties. One consistent approach is via detector-based measurements. We study the effects of such measurements in a CFT with a holographic dual. We work out the boundary space-time regions associated to a Lüders update and how the outcome extends to modifications of the bulk gravity state. We explore information-theoretic consequences of this picture, and relate the information extracted by a measurement to updates of the semiclassical parameters of the bulk state.
ALINE, a unified framework from researchers at Aalto University and the University of Helsinki, integrates amortized Bayesian inference with active data acquisition using a transformer-based architecture. The system enables flexible, goal-directed querying for specific parameters or predictive tasks and delivers instantaneous, accurate inference, outperforming existing methods in various regression and experimental design benchmarks.
A scalable and robust 3D tissue transcriptomics profile can enable a holistic understanding of tissue organization and provide deeper insights into human biology and disease. Most predictive algorithms that infer ST directly from histology treat each section independently and ignore 3D structure, while existing 3D-aware approaches are not generative and do not scale well. We present Holographic Tissue Expression Inpainting and Analysis (HoloTea), a 3D-aware flow-matching framework that imputes spot-level gene expression from H&E while explicitly using information from adjacent sections. Our key idea is to retrieve morphologically corresponding spots on neighboring slides in a shared feature space and fuse this cross section context into a lightweight ControlNet, allowing conditioning to follow anatomical continuity. To better capture the count nature of the data, we introduce a 3D-consistent prior for flow matching that combines a learned zero-inflated negative binomial (ZINB) prior with a spatial-empirical prior constructed from neighboring sections. A global attention block introduces 3D H&E scaling linearly with the number of spots in the slide, enabling training and inference on large 3D ST datasets. Across three spatial transcriptomics datasets spanning different tissue types and resolutions, HoloTea consistently improves 3D expression accuracy and generalization compared to 2D and 3D baselines. We envision HoloTea advancing the creation of accurate 3D virtual tissues, ultimately accelerating biomarker discovery and deepening our understanding of disease.
Emission lines of FeI and NiI are commonly found in the coma of solar system comets, even at large heliocentric distances. These atoms are most likely released from the surface of the comet's nucleus or from a short-lived parent. The presence of these lines in cometary spectra is unexpected because the surface blackbody equilibrium temperature is too low to allow the sublimation of refractory minerals containing these metals. These lines were also found in the interstellar comet 2I/Borisov which has a NiI/FeI abundance ratio similar to that observed in solar system comets. On average, this ratio is one order of magnitude higher than the solar Ni/Fe abundance ratio. Here, we report observations of the new interstellar comet 3I/ATLAS, which were carried out with the ESO Very Large Telescope equipped with the UVES spectrograph. Spectra were obtained at six epochs, at heliocentric distances ranging from 3.14 to 2.14 au. NiI was detected at all epochs. FeI was only detected at heliocentric distances smaller than 2.64 au. We estimated the NiI and FeI production rates by comparing the observed line intensities with those produced by a fluorescence model. Comet 3I exhibits a high production rate of NiI atoms as well as a high NiI/FeI ratio, making it exceptional when compared to solar system comets and 2I/Borisov. Additionally, we found that the NiI/FeI ratio decreases rapidly with decreasing heliocentric distance, suggesting that comet 3I could soon become indistinguishable from solar system comets in this respect. We interpreted these observations assuming that the NiI and FeI atoms were released through the sublimation of Ni(CO)4_4 and Fe(CO)5_5 carbonyls, which supports the presence of these species in the cometary material.
The gravitational wave equation of motion includes direct coupling to the Riemann tensor. The curvature terms are usually neglected, but they can be large at the location of matter particles and impact the angular diameter distance. We apply the recently introduced post-geometrical optics approximation that includes curvature to gravitational wave propagation. Assuming that particles are localised within their Compton wavelength, the curvature due to electrons leads to a large effect on the angular diameter distance, but caustic formation invalidates the post-geometrical optics approximation. We conclude that the interesting regime of validity of the approximation is limited, as it ceases to apply when the curvature effects become large. Other methods are needed to evaluate the effect of curvature spikes, and the localisation of particles due to decoherence also needs further work.
Researchers from Tampere University and other European institutions developed a multi-agent Large Language Model system to enhance code review by providing comprehensive, contextually-aware feedback. The system identifies potential bugs, code smells, and inefficiencies, offering actionable recommendations and educational guidance across various programming languages and application domains.
We present BenchRL-QAS, a unified benchmarking framework for reinforcement learning (RL) in quantum architecture search (QAS) across a spectrum of variational quantum algorithm tasks on 2- to 8-qubit systems. Our study systematically evaluates 9 different RL agents, including both value-based and policy-gradient methods, on quantum problems such as variational eigensolver, quantum state diagonalization, variational quantum classification (VQC), and state preparation, under both noiseless and noisy execution settings. To ensure fair comparison, we propose a weighted ranking metric that integrates accuracy, circuit depth, gate count, and training time. Results demonstrate that no single RL method dominates universally, the performance dependents on task type, qubit count, and noise conditions providing strong evidence of no free lunch principle in RL-QAS. As a byproduct we observe that a carefully chosen RL algorithm in RL-based VQC outperforms baseline VQCs. BenchRL-QAS establishes the most extensive benchmark for RL-based QAS to date, codes and experimental made publicly available for reproducibility and future advances.
Variational quantum algorithms hold the promise to address meaningful quantum problems already on noisy intermediate-scale quantum hardware. In spite of the promise, they face the challenge of designing quantum circuits that both solve the target problem and comply with device limitations. Quantum architecture search (QAS) automates the design process of quantum circuits, with reinforcement learning (RL) emerging as a promising approach. Yet, RL-based QAS methods encounter significant scalability issues, as computational and training costs grow rapidly with the number of qubits, circuit depth, and hardware noise. To address these challenges, we introduce TensorRL-QAS\textit{TensorRL-QAS}, an improved framework that combines tensor network methods with RL for QAS. By warm-starting the QAS with a matrix product state approximation of the target solution, TensorRL-QAS effectively narrows the search space to physically meaningful circuits and accelerates the convergence to the desired solution. Tested on several quantum chemistry problems of up to 12-qubit, TensorRL-QAS achieves up to a 10-fold reduction in CNOT count and circuit depth compared to baseline methods, while maintaining or surpassing chemical accuracy. It reduces classical optimizer function evaluation by up to 100-fold, accelerates training episodes by up to 98%\%, and can achieve 50%\% success probability for 10-qubit systems, far exceeding the &lt;1%\% rates of baseline. Robustness and versatility are demonstrated both in the noiseless and noisy scenarios, where we report a simulation of an 8-qubit system. Furthermore, TensorRL-QAS demonstrates effectiveness on systems on 20-qubit quantum systems, positioning it as a state-of-the-art quantum circuit discovery framework for near-term hardware and beyond.
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