物理与天体物理最新文献

{"title":"Mamba time series forecasting with uncertainty quantification.","authors":"Pedro Pessoa, Paul Campitelli, Douglas P Shepherd, S Banu Ozkan, Steve Pressé","doi":"10.1088/2632-2153/adec3b","DOIUrl":"https://doi.org/10.1088/2632-2153/adec3b","url":null,"abstract":"<p><p>State space models, such as Mamba, have recently garnered attention in time series forecasting (TSF) due to their ability to capture sequence patterns. However, in electricity consumption benchmarks, Mamba forecasts exhibit a mean error of approximately 8%. Similarly, in traffic occupancy benchmarks, the mean error reaches 18%. This discrepancy leaves us to wonder whether the prediction is simply inaccurate or falls within error given spread in historical data. To address this limitation, we propose a method to quantify the predictive uncertainty of Mamba forecasts. To achieve this, we propose a dual-network framework based on the Mamba architecture for probabilistic forecasting, where one network generates point forecasts while the other estimates predictive uncertainty by modeling variance. We abbreviate our tool, Mamba with probabilistic TSF, as Mamba-ProbTSF and the code for its implementation is available on GitHub https://github.com/PessoaP/Mamba-ProbTSF. Evaluating this approach on synthetic and real-world benchmark datasets, we find Kullback-Leibler divergence between the learned distributions and the data-which, in the limit of infinite data, should converge to zero if the model correctly captures the underlying probability distribution-reduced to the order of 10^-3 for synthetic data and 10^-1 for real-world benchmark. We find that in both the electricity consumption and traffic occupancy benchmark, the true trajectory stays within the predicted uncertainty interval at the two-sigma level about 95% of the time. We further compare Mamba-ProbTSF against leading probabilistic forecast methods, DeepAR and ARIMA, and show that our method consistently achieves lower forecast errors while offering more reliable uncertainty quantification. We end with a consideration of potential limitations, adjustments to improve performance, and considerations for applying this framework to processes for purely or largely stochastic dynamics where the stochastic changes accumulate as observed, for example, in pure Brownian motion or molecular dynamics trajectories.</p>","PeriodicalId":33757,"journal":{"name":"Machine Learning Science and Technology","volume":"6 3","pages":"035012"},"PeriodicalIF":6.3,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12281171/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144699735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of excitation field amplitude on magnetic particle imaging performance: a modeling study.","authors":"Ebrahim Azizi, Changzhi Li, Jenifer Gómez-Pastora, Rui He, Kai Wu","doi":"10.1088/1361-6463/adeea2","DOIUrl":"https://doi.org/10.1088/1361-6463/adeea2","url":null,"abstract":"<p><p>Magnetic particle imaging (MPI) is a new tomographic imaging technique that can quantitatively correlate MPI signal intensity to the spatial distribution of magnetic nanoparticle (MNP) tracers. Due to its non-ionizing nature, low background signal from biological matrices, high contrast, and relatively good spatial and temporal resolution, MPI has been actively studied and applied to biomedical imaging and is expected to reach the clinical stage soon. To further improve the spatial resolution limit in MPI, researchers have been working towards optimizing the image reconstruction algorithms, magnetic field profiles, tracer designs, circuitry, etc. Recent studies reported that lower excitation field amplitudes can improve spatial resolution, though this comes at the expense of lower MPI signal and tracer sensitivity. Different excitation field profiles directly affect the collective dynamic magnetizations of tracers recorded by the receiver coil in MPI. However, there is a gap between understanding the relaxation dynamics of MNP tracers, the signal-to-noise ratio (SNR) of MPI signals, and the MPI spatial resolution. In this work, we used a stochastic Langevin equation with coupled Brownian and Néel relaxations to model the magnetic dynamics of different MNP tracers subjected to varying excitation fields. We analyzed the collective time-domain dynamic magnetizations (<i>M</i>-<i>t</i> curves), magnetic-field hysteresis loops (<i>M-H</i> curves), point spread functions (PSFs), higher harmonics, and SNR of the third harmonic to understand how the excitation field affects MPI performance. We employed Full Width at Half Maximum and SNR as evaluation metrics for imaging resolution and signal quality, respectively. Our study supports previous findings on the impact of excitation field amplitude on MPI performance while offering more profound insights into the interplay of nonequilibrium Néel and Brownian relaxation, tracer core size, and SNR.</p>","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"58 30","pages":"305002"},"PeriodicalIF":3.1,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12281415/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144698900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantum frequency resampling","authors":"Emanuele Tumbiolo, Simone Roncallo, Chiara Macchiavello, Lorenzo Maccone","doi":"10.1038/s41534-025-01076-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01076-z","url":null,"abstract":"<p>In signal processing, resampling algorithms can modify the number of resources encoding a collection of data points. Downsampling reduces the cost of storage and communication, while upsampling interpolates new data from limited one, e.g., when resizing a digital image. We present a toolset of quantum algorithms to resample data encoded in the probabilities of a quantum register, using the quantum Fourier transform to adjust the number of high-frequency encoding qubits. We discuss advantage over classical resampling algorithms.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"29 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Double fano resonances in nano-modulated thin films for frequency and angular filtering","authors":"Lucciano A. Letelier ,&nbsp;Julianija Nikitina ,&nbsp;Lina Grineviciute ,&nbsp;Kestutis Staliunas","doi":"10.1016/j.optlastec.2025.113617","DOIUrl":"10.1016/j.optlastec.2025.113617","url":null,"abstract":"<div><div>Fano resonances in sub-wavelength scale periodically modulated thin films are known to provide narrow transmission bandgaps in the wavelength- and in the incidence angle domains. Here, we demonstrate that the interplay of two nearby Fano resonances can provide extremely narrow frequency (or wavelength) high-pass bands in transmission, much narrower than the Fano resonances themselves. We fabricate such high-pass frequency filters and measure their transmission characteristics. Moreover, by combining two identical structures tilted at some angles, one with respect to another, we show a tunable high-pass window in the angle-wavelength domain. This tunable high-pass window is formed by four Fano resonance lines from two nanostructured samples.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"192 ","pages":"Article 113617"},"PeriodicalIF":4.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discrete Hartley transform - orthogonal frequency division multiplexing underwater acoustic communication system based on complex-to-real conversion","authors":"Jinqiu Wu ,&nbsp;Wenbo Zhang ,&nbsp;Rouchi Chen ,&nbsp;Xiaofei Qi ,&nbsp;Gang Qiao ,&nbsp;Zhiwei Zhao ,&nbsp;Haijun Tan","doi":"10.1016/j.apacoust.2025.110944","DOIUrl":"10.1016/j.apacoust.2025.110944","url":null,"abstract":"<div><div>In this paper, we propose a Complex-to-Real Transformation (C2RT) for Discrete Hartley Transform Orthogonal Frequency Division Multiplexing (DHT-OFDM) in underwater acoustic communication system. C2RT is an efficient system modulation scheme based on the principle of index modulation. Traditional DHT-OFDM systems only support modulation and demodulation in the real domain, which limits the use of high-order phase modulation. This restriction makes it difficult to improve communication rates and bandwidth utilization. C2RT is an effective solution to this problem. By incorporating this algorithm into DHT-OFDM system, high-order phase modulation can be achieved while maintaining the system's real-valued characteristics. Additionally, due to the sparsity of its output sequence, C2RT provides higher transmission accuracy compared to direct transmission schemes.</div><div>The experimental verifies that the DHT-OFDM system proposed in this paper can be applied to 300 m and 5 km underwater acoustic transmission with less error bits. This makes the proposed C2RT DHT-OFDM method a promising approach for enhancing underwater communication technologies.</div></div>","PeriodicalId":55506,"journal":{"name":"Applied Acoustics","volume":"240 ","pages":"Article 110944"},"PeriodicalIF":3.4,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Speckle-based image reconstruction via uniform illumination in single multimode fiber endoscopic imaging systems","authors":"Hangyu Zhang ,&nbsp;Dongyu Xia ,&nbsp;Runchu Xu ,&nbsp;Houru Zhao ,&nbsp;Leihong Zhang ,&nbsp;Yangjun Li ,&nbsp;Dawei Zhang","doi":"10.1016/j.optlastec.2025.113633","DOIUrl":"10.1016/j.optlastec.2025.113633","url":null,"abstract":"<div><div>Conventional multimode fiber (MMF) imaging systems based on Gaussian illumination often suffer from uneven speckle distributions, which limit image reconstruction quality and cause significant performance degradation under perturbations such as fiber deformation or temperature fluctuations. To overcome these challenges, this study proposes a uniform illumination scheme enabled by beam shaping, where a single MMF simultaneously serves as both the illumination unit and imaging probe. The input Gaussian beam is transformed into a uniform beam to generate more evenly distributed illumination speckles. In parallel, a lightweight U-shaped neural network architecture (USNet) is developed to enable efficient image reconstruction. Experimental results show that under static conditions, the combination of uniform illumination and USNet achieves SSIM values of 0.8105, 0.7056, and 0.8137 on the MNIST, Fashion-MNIST, and SIPaKMeD datasets, respectively. Under thermal perturbation, the uniform speckle pattern significantly enhances system stability; although its robustness under mechanical disturbance is slightly lower than Gaussian illumination, the proposed method still maintains superior reconstruction performance within a practical perturbation range. Furthermore, additional evaluations under simulated subjective speckle conditions and varying MMF lengths demonstrate the method’s strong scalability and clinical application potential. This study is the first to systematically validate the robustness advantages of uniform illumination in MMF imaging and integrates a lightweight network to achieve high-quality image reconstruction, offering a new pathway and theoretical foundation for dynamic minimally invasive medical imaging with MMFs.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"192 ","pages":"Article 113633"},"PeriodicalIF":4.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Infrared small target detection via multidirectional derivative joint contrast measure","authors":"Feng Xie ,&nbsp;Dongsheng Yang ,&nbsp;Yao Yang ,&nbsp;Tao Wang ,&nbsp;Kai Zhang","doi":"10.1016/j.optlastec.2025.113599","DOIUrl":"10.1016/j.optlastec.2025.113599","url":null,"abstract":"<div><div>Detecting small targets in infrared imagery plays a crucial role in infrared search and early warning applications, and has recently become a research hotspot within the field of computer vision. However, many existing approaches predominantly rely on single-feature representations, which limits their effectiveness when dealing with complex scenes involving cluttered regions like edges and corners. To overcome this limitation, the present research introduces a novel method for detecting small infrared targets based on a multidirectional derivative joint contrast measure (MDCM). Initially, a facet model is used to derive the multidirectional second-order derivatives (MSOD) of the infrared image, enabling analysis of contrast characteristics between targets and background interference in the MSOD domain. Leveraging the distinct second-order derivative features inherent to small targets, a derivative saliency measure weighted peak difference (DSMWPD) is developed to mitigate the influence of pronounced edges and corner artifacts. Additionally, acknowledging the approximately isotropic nature of small targets, a local contrast measure weighted cross-dissimilarity (LCMWCD) is designed, which applies multidirectional contrast dissimilarities as penalization to suppress intense structured clutter and further emphasize target regions. The final saliency map is obtained by combining the outputs multiplicatively, followed by adaptive thresholding to extract the targets. Experimental validation demonstrates that the proposed approach achieves superior accuracy and robustness in detecting infrared small targets across various challenging background conditions, outperforming several contemporary state-of-the-art algorithms.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"192 ","pages":"Article 113599"},"PeriodicalIF":4.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Counterfactual communication not achieved yet – A Comment on Salih et al. (2022)","authors":"Sandu Popescu","doi":"10.1038/s41534-025-00975-5","DOIUrl":"https://doi.org/10.1038/s41534-025-00975-5","url":null,"abstract":"<p>In this comment I argue that there are two major issues with the protocol presented in “The laws of physics do not prohibit counterfactual communication”, Hatim Salih, Will McCutcheon, Jonte R. Hance and John Rarity, npj Quantum Information (2022) 8:60. One is an erroneous interpretation of the role of clicks in detector <i>D</i>₀ and the second is the way in which post-selection is used. I argue that these invalidate the claims of that paper.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"12 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relational observables in group field theory","authors":"Luca Marchetti and Edward Wilson-Ewing","doi":"10.1088/1361-6382/adedf4","DOIUrl":"https://doi.org/10.1088/1361-6382/adedf4","url":null,"abstract":"We construct relational observables in group field theory (GFT) in terms of covariant positive operator-valued measures (POVMs), using techniques developed in the context of quantum reference frames (QRFs). We focus on matter QRFs; this can be generalized to other types of frames within the same POVM-based framework. The resulting family of relational observables provides a covariant framework to extract localized observables from GFT, which is typically defined in a perspective-neutral way. Then, we compare this formalism with previous proposals for relational observables in GFT. We find that our QRF-based relational observables overcome the intrinsic limitations of previous proposals while reproducing the same continuum limit results concerning expectation values of the number and volume operators on coherent states. Nonetheless, there can be important differences for more complex operators, as well as for other types of GFT states. Finally, we also use a specific class of POVMs to show how to project states and operators from the more general perspective-neutral GFT Fock space to a perspective-dependent one where a scalar matter field plays the role of a relational clock.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"75 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New generalized Killing spinor field classes in warped flux compactifications","authors":"D. Gonçalves Fabri ,&nbsp;R. da Rocha","doi":"10.1016/j.physleta.2025.130836","DOIUrl":"10.1016/j.physleta.2025.130836","url":null,"abstract":"<div><div>The generalized Fierz identities are addressed in the Kähler–Atiyah bundle framework from the perspective of the equations governing constrained generalized Killing spinor fields. We explore the spin geometry in a Riemannian 8-manifold, <span><math><msub><mrow><mi>M</mi></mrow><mrow><mn>8</mn></mrow></msub></math></span>, composing a warped flux compactification AdS<span><math><mmultiscripts><mrow><mo>×</mo></mrow><mprescripts></mprescripts><mrow><mn>3</mn></mrow><none></none></mmultiscripts><msub><mrow><mi>M</mi></mrow><mrow><mn>8</mn></mrow></msub></math></span>, whose metric and fluxes preserve one supersymmetry in AdS₃. Supersymmetry conditions can be efficiently translated into spinor bilinear covariants, whose algebraic and differential constraints yield identifying new spinor field classes. Intriguing implications and potential applications are discussed.</div></div>","PeriodicalId":20172,"journal":{"name":"Physics Letters A","volume":"556 ","pages":"Article 130836"},"PeriodicalIF":2.3,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}