物理与天体物理最新文献

{"title":"Multi-label bird sound recognition based on multi-view learning and dynamic threshold adjustment","authors":"Minghui Fang ,&nbsp;Dengwei Wu ,&nbsp;Wei Wu ,&nbsp;Mengfan Fang ,&nbsp;Yanhong Chen ,&nbsp;Xiangzeng Kong ,&nbsp;Chen Zhao","doi":"10.1016/j.apacoust.2025.110943","DOIUrl":"10.1016/j.apacoust.2025.110943","url":null,"abstract":"<div><div>Bird species monitoring is crucial for conservation, but overlapping vocalizations in natural environments complicate multi-label classification, affecting model performance. To address these issues, we developed the Adaptive Multi-label Attention Threshold Network (AMAT-Net) as a bird sound classification framework. AMAT-Net employs a multi-view strategy, combining bidirectional gated recurrent unit (BiGRU)-attention networks to analyze temporal features and multi-scale convolutional neural networks to extract spectral features, enabling analysis of bird sounds. Given the differences between temporal and spectral features, time-domain features capture transient changes, whereas frequency-domain features reveal spectral trends. Balancing the essential features of both without losing details is difficult. Therefore, we designed the temporal–spectral attention feature fusion (TSAFF) module to optimize feature fusion. TSAFF employs an attention-based mechanism to fuse temporal and spectral features, enhancing the cross-domain feature complementarity. Binary classification is conducted between relevant and irrelevant labels, and threshold is determined based on the results. A score-based thresholding strategy called dynamic threshold scaling was then developed. A label correlation matrix is constructed using Pearson's correlation coefficients, and the classifier's scores for instance-label pairs with high inter-label correlations are adjusted accordingly during prediction. In addition, hierarchical cross-validation is used to search for the threshold that maximizes the F1 score, dynamically optimizing the decision boundary for each species to adapt to the actual label distribution. Experimental results on a synthesized dataset of 10 bird species (including cases of 2, 3, and 4 species vocalizing simultaneously) and the public BirdCLEF+2025 dataset demonstrate that AMAT-Net achieves an accuracy of 95.54% with a macro-F1 score of 91.26% on the synthesized dataset, and an accuracy of 98.75% with a macro-F1 score of 93.14% on BirdCLEF+2025.</div></div>","PeriodicalId":55506,"journal":{"name":"Applied Acoustics","volume":"240 ","pages":"Article 110943"},"PeriodicalIF":3.4,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144714335","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":"Frequency modulated continuous wave LiDAR with expanded field-of-view based on polarization-splitting metasurface","authors":"Kelan Chen, Jitao Ji, Xueyun Li, Zhiyuan Lin, Zhizhang Wang, Jiacheng Sun, Jian Li, Chunyu Huang, Pan Dai, Jitao Cao, Xiangfei Chen, Shining Zhu, Tao Li","doi":"10.1515/nanoph-2025-0183","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0183","url":null,"abstract":"Frequency modulated continuous wave (FMCW) light detection and ranging (LiDAR) has recently become a research hotspot in the fields of autonomous driving and intelligent perception due to its high-precision ranging and velocity measurement capabilities. However, the existing LiDAR systems are usually challenged in expanding the field-of-view (FOV), which often comes at the expense of beam quality and degrades the detection accuracy and signal-to-noise ratio. On the other hand, the complexity of data processing algorithms may introduce significant measurement inaccuracies, potentially leading to substantial deviations in the final results. These two constraints limit the performance of LiDAR in complex scenarios. To address these issues, this paper proposes a new architecture for FMCW LiDAR that employs a geometric metasurface as a polarization splitter for expanded FOV of beam steering. With the combination of mechanical scanning mirror and metasurface, the scanning FOV has been successfully enlarged from 64° × 20° to 64° × 40°. Simultaneously, millimeter-level precision was achieved in distance measurement, along with an average relative error of 9 mm/s in velocity measurement, which confirms stable and precise system performance. This approach not only broadens the scanning range but also preserves the measurement accuracy of FMCW technology. This paper innovatively combines polarization beam-splitting metasurface with FMCW technology to achieve high-precision measurement over a wide field of view, providing a promising new technical pathway for the technological evolution of future LiDAR systems.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"12 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715721","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":"Experimental analysis of the thermal management and internal quantum efficiency of terahertz quantum cascade laser harmonic frequency combs","authors":"M. Alejandro Justo Guerrero, Elisa Riccardi, Lianhe Li, Mark Rosamond, A. Giles Davies, Edmund H. Linfield, Miriam S. Vitiello","doi":"10.1515/nanoph-2025-0207","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0207","url":null,"abstract":"Quantum cascade laser (QCL) harmonic state frequency combs (HFCs) have recently attracted considerable interest for applications ranging from the generation of tones of high spectral purity, high data rate wireless communication networks, radiofrequency arbitrary waveform synthesis, and for fundamental light-matter investigations in quantum physics. However, a detailed knowledge of the nature of the electronic and thermal energy distribution in these devices is of paramount importance for the refinement of their thermal management and quantum efficiency, which are key to the widespread adoption of QCL HFC technology in a new generation of integrated optical quantum platforms. Here, we perform a comparative study of the thermal and electronic properties of Fabry–Perot and micro-ring HFC QCLs, operating in the terahertz frequency range, using micro-probe band-to-band photoluminescence. By monitoring the lattice temperature and the electron cooling above the threshold for stimulated emission, we extract the device thermal resistances and the internal quantum efficiencies, highlighting the key role of the resonator architecture.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"63 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715717","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":"Spin–lattice coupling and anisotropic magneto-transport in Fe-ordered Fe5−xGeTe2","authors":"Junbo Li, Yihao Wang, Peng Wu, Jiangpeng Song, Zhihao Li, Liang Cao, Guopeng Wang, Yimin Xiong","doi":"10.1063/5.0266796","DOIUrl":"https://doi.org/10.1063/5.0266796","url":null,"abstract":"Two-dimensional van der Waals (vdW) magnetic materials have attracted extensive attention for the development of next-generation spintronic devices. The vdW magnet Fe5−xGeTe2 exhibits reversible spin structure and distinct electronic band structures tuned by thermal process with the Curie temperature (TC) above room temperature. By using a quench process, Fe5−xGeTe2 shows Fe(1) sites ordered in the crystal structure and nontrivial flatbands in electronic structures. However, detailed experimental investigations of physical properties in the Fe-ordered phase remain limited. In this work, we synthesize the Fe-ordered Fe5−xGeTe2 crystals and systematically investigate the physical properties by the combination of multiple measurements. The enhanced electronic specific heat coefficient (γ = 70.43 mJ mol−1 K−2) and Kadowaki–Woods ratio (A/γ2≈ 2.6 μΩ cm mol2 K2 J−2) provide evidence for the existence of flatbands and strong electron correlations. Furthermore, strong spin–lattice coupling is observed, where magnetic phase transitions coincide with lattice vibrations and Raman spectral shifts. In addition, anisotropic magneto-transport properties reveal the coupling between Fe(1) magnetic moments and charge carriers in the ordered phase. Our results provide further experimental evidence of the flatbands in the Fe-ordered phase as well as offer a strategy for designing tunable spintronic devices by exploiting the synergy between spin and lattice dynamics in vdW heterostructures.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"708 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715722","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":"Synthetic aperture waveguide holography for compact mixed-reality displays with large étendue","authors":"Suyeon Choi, Changwon Jang, Douglas Lanman, Gordon Wetzstein","doi":"10.1038/s41566-025-01718-w","DOIUrl":"https://doi.org/10.1038/s41566-025-01718-w","url":null,"abstract":"<p>Mixed-reality (MR) display systems enable transformative user experiences across various domains, including communication, education, training and entertainment. To create an immersive and accessible experience, the display engine of the MR display must project perceptually realistic 3D images over a wide field of view observable from a large range of possible pupil positions, that is, it must support a large étendue. Current MR displays, however, fall short in delivering these capabilities in a compact device form factor. Here we present an ultra-thin MR display design that overcomes these challenges using a unique combination of waveguide holography and artificial intelligence (AI)-driven holography algorithms. One of the key innovations of our display system is a compact, custom-designed waveguide for holographic near-eye displays that supports a large effective étendue. This is co-designed with an AI-based algorithmic framework combining an implicit large-étendue waveguide model, an efficient wave propagation model for partially coherent mutual intensity and a computer-generated holography framework. Together, our unique co-design of a waveguide holography system and AI-driven holographic algorithms represents an important advancement in creating visually comfortable and perceptually realistic 3D MR experiences in a compact wearable device.</p>","PeriodicalId":18926,"journal":{"name":"Nature Photonics","volume":"63 1","pages":""},"PeriodicalIF":35.0,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715276","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":"H.E.S.S. programme searching for VHE gamma rays associated with FRBs","authors":"F. Aharonian, A. Archaryya, J. Aschersleben, H. Ashkar, M. Backes, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, M. Böttcher, C. Boisson, J. Bolmont, M. de Bony de Lavergne, J. Borowska, F. Bradascio, R. Brose, A. Brown, F. Brun, B. Bruno, C. Burger-Scheidlin, S. Casanova, J. Celic, M. Cerruti, T. Chand, S. Chandra, A. Chen, J. Chibueze, O. Chibueze, J. Damascene Mbarubucyeye, J. de Assis Scarpin, A. Djannati-Ataï, J. Djuvsland, A. Dmytriiev, K. Egberts, S. Einecke, J.-P. Ernenwein, C. Escañuela Nieves, M. Filipovic, G. Fontaine, S. Funk, S. Gabici, J.F. Glicenstein, J. Glombitza, G. Grolleron, B. Heß, W. Hofmann, T.L. Holch, M. Holler, D. Horns, Zhiqiu Huang, A. Jaitly, M. Jamrozy, F. Jankowsky, I. Jung-Richardt, E. Kasai, K. Katarzyński, D. Kerszberg, R. Khatoon, B. Khélifi, W. Kluźniak, Nu. Komin, K. Kosack, D. Kostunin, A. Kundu, R.G. Lang, S. Le Stum, A. Lemière, M. Lemoine-Goumard, J.-P. Lenain, A. Luashvili, J. Mackey, D. Malyshev, V. Marandon, ..","doi":"10.1088/1475-7516/2025/07/086","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/07/086","url":null,"abstract":"Fast Radio Bursts (FRBs) are highly energetic, extremely short-lived bursts of radio flashes. Despite extensive research, the exact cause of these outbursts remains speculative. The high luminosity, short duration, and high dispersion measure of these events suggest they result from extreme, high-energy extragalactic sources, such as highly magnetized and rapidly spinning neutron stars known as magnetars. The number of detected FRBs, including repeating ones, has grown rapidly in recent years. Except for FRB 20200428D, and FRB-like radio burst that is associated to Galactic magnetar SGR 1935+2154, no multi-wavelength counterpart to any FRB has been detected yet. The High Energy Stereoscopic System (H.E.S.S.) telescope has developed a program to follow up FRBs searching for their gamma-ray counterparts, helping to uncover the nature of FRBs and FRB sources. This paper provides an overview of the searches for FRB sources conducted by H.E.S.S., including follow-up observations and simultaneous multi-wavelength campaigns with radio and X-ray observatories. Among the FRB sources observed by H.E.S.S., nine are localized with redshifts ranging between 0.11 and 0.492 from 2015 to 2022. No significant very high energy (VHE) emission was detected during these observations. We report constraints on the VHE luminosity ranging from 1044 erg s-1 and 1048 erg s-1, placing limits on the FRB's region persistent VHE emission and potential FRB afterglow emission across timescales from hours to years.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"27 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144719643","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":"Measuring black hole spin through gravitational lensing of pulsars","authors":"Amjad Ashoorioon, Mohammad Bagher Jahani Poshteh and Robert B Mann","doi":"10.1088/1361-6382/adef8d","DOIUrl":"https://doi.org/10.1088/1361-6382/adef8d","url":null,"abstract":"We propose a new procedure for measuring the spin of a black hole with an unprecedented accuracy based on the gravitational lensing of millisecond pulsars. We derive the basic equations for lensing by a rotating black hole. We show that the frame dragging effect increases the deflection angle of a light ray co-rotating with the black hole. For the primary (secondary) images the angular positions are larger (smaller) for a rotating black hole by an amount on the order of tens of microarcseconds. The differential time delay of images for the case in which the lens is a rotating black hole is smaller than that in the case of non-rotating lens of the same mass, and it can be larger than a few milliseconds. We show that this quantity offers the possibility of reducing the error of spin measurement to less than one percent if we could measure the differential time delay with accuracy of microseconds. We also study relativistic images that are produced by light rays that rotate around the black hole before reaching the observer. The angular positions of relativistic images on the same side as the primary (secondary) image are a few microarcseconds larger (smaller) if the black hole is rotating. Furthermore, the differential time delay between relativistic images is about twelve orders of magnitude larger in the case of rotating lens.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715335","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":"A Chern-Simons approach to self-dual gravity in ( 2 + 1 ) ...","authors":"Prince K Osei","doi":"10.1088/1361-6382/adecd4","DOIUrl":"https://doi.org/10.1088/1361-6382/adecd4","url":null,"abstract":"The (2 + 1)-dimensional analogue self-dual gravity which is obtained via spacetime dimension reduction of the (3 + 1)-dimensional Holst action without reducing the internal gauge group is studied. A Chern–Simons formulation for this theory is constructed based on the gauge group and maps the 3d complex self-dual dynamical variable and connection to 6d real variables which combines into a 12d Cartan connection. The Chern–Simons approach leads to a real analogue for the self-dual action based on a larger symmetry group. The quantization process follows the combinatorial quantization method outlined for Chern–Simons theory. In the combinatorial quantization of the phase space, the Poisson structure governing the moduli space of flat connections which emerges is obtained using the classical r-matrix for the quantum double , viewed as the double of a double . This quantum double gives the structure for quantum symmetries within the quantum theory for the model.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"4 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144715332","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":"Global string instantons","authors":"Jose J. Blanco-Pillado, Georgios Fanaras and Alexander Vilenkin","doi":"10.1088/1475-7516/2025/07/087","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/07/087","url":null,"abstract":"We study the formation of gravitating global strings through quantum mechanical tunneling. The instantons that describe the nucleation process are characterized by two parameters: the string core thickness and its gravitational backreaction controlled by the string core energy density. We obtain solutions across a wide range of these parameters by carrying out numerical integration via multiple shooting methods. Our results are in agreement with previous findings on the nucleation of other topological defects; specifically, after reaching a certain threshold for the string core thickness or its gravitational backreaction, the configuration becomes homogeneous in a manner akin to Hawking-Moss solutions. Additionally, we analyze the global structure of the analytical continuation of the solutions to Lorentzian signature, revealing the emergence of a region of spacetime that describes an anisotropic universe. Finally, we also discuss the relevance of these instantons in the context of quantum cosmology.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"4 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144719644","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":"Constraining the gravitational wave speed in the early Universe via gravitational Cherenkov radiation","authors":"Paola C.M. Delgado, Alexander Ganz, Chunshan Lin and Roxane Thériault","doi":"10.1088/1475-7516/2025/07/088","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/07/088","url":null,"abstract":"Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. In this paper, we investigate graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. We find that for the minimal model, where only the speed of gravitational waves is modified and a standard model plasma minimally couples to gravity, the relic graviton background can be enhanced by several orders of magnitude, but still agrees with the Big Bang Nucleosynthesis (BBN) bound. Moreover, we also find that for Horndeski theories, such as Galileon theory, the relic background produced by the thermalized scalar field can reach significant amplitudes, exceeding the BBN bound for a region of the parameter space. By requiring the relic graviton background to remain consistent with the BBN constraint, we derive limits on the gravitational wave speed at early times in these modified gravity theories.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"62 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144719646","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}