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First polarisation measurement of coherently photoproduced J/ψ in ultra-peripheral Pb–Pb collisions at s_NN=5.02 TeV

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physics Letters, Section B: Nuclear, Elementary Particle and High-Energy physics 2025年 865卷

作者： Acharya, S. Adamová, D. Adler, A. Aglieri Rinella, G. Agnello, M. Agrawal, N. Ahammed, Z. Ahmad, S. Ahn, S.U. Ahuja, I. Akindinov, A. Al-Turany, M. Aleksandrov, D. Alessandro, B. Alfanda, H.M. Alfaro Molina, R. Ali, B. Alici, A. Alizadehvandchali, N. Alkin, A. Alme, J. Alocco, G. Alt, T. Altsybeev, I. Alvarado, J.R. Anaam, M.N. Andrei, C. Andronic, A. Anguelov, V. Antinori, F. Antonioli, P. Apadula, N. Aphecetche, L. Appelshäuser, H. Arata, C. Arcelli, S. Aresti, M. Arnaldi, R. Arneiro, J.G.M.C.A. Arsene, I.C. Arslandok, M. Augustinus, A. Averbeck, R. Azmi, M.D. Badalà, A. Bae, J. Baek, Y.W. Bai, X. Bailhache, R. Bailung, Y. Balbino, A. Baldisseri, A. Balis, B. Banerjee, D. Banoo, Z. Barbera, R. Barile, F. Barioglio, L. Barlou, M. Barnaföldi, G.G. Barnby, L.S. Barret, V. Barreto, L. Bartels, C. Barth, K. Bartsch, E. Bastid, N. Basu, S. Batigne, G. Battistini, D. Batyunya, B. Bauri, D. Bazo Alba, J.L. Bearden, I.G. Beattie, C. Becht, P. Behera, D. Belikov, I. Bell Hechavarria, A.D.C. Bellini, F. Bellwied, R. Belokurova, S. Belyaev, V. Bencedi, G. Beole, S. Bercuci, A. Berdnikov, Y. Berdnikova, A. Bergmann, L. Besoiu, M.G. Betev, L. Bhaduri, P.P. Bhasin, A. Bhat, M.A. Bhattacharjee, B. Bianchi, L. Bianchi, N. Bielčík, J. Bielčíková, J. Biernat, J. Bigot, A.P. Bilandzic, A. Biro, G. Biswas, S. Bize, N. Blair, J.T. Blau, D. Blidaru, M.B. Bluhme, N. Blume, C. Boca, G. Bock, F. Bodova, T. Bogdanov, A. Boi, S. Bok, J. Boldizsár, L. Bombara, M. Bond, P.M. Bonomi, G. Borel, H. Borissov, A. Borquez Carcamo, A.G. Bossi, H. Botta, E. Bouziani, Y.E.M. Bratrud, L. Braun-Munzinger, P. Bregant, M. Broz, M. Bruno, G.E. Buckland, M.D. Budnikov, D. Buesching, H. Bufalino, S. Buhler, P. Buthelezi, Z. Bylinkin, A. Bysiak, S.A. Cai, M. Caines, H. Caliva, A. Calvo Villar, E. Camacho, J.M.M. Camerini, P. Canedo, F.D.M. Cantway, S.L. Carabas, M. Carballo, A.A. Carnesecchi, F. Caron, R. Carvalho, L.A.D. Castillo Castellanos, J. Catalano, F. Ceballos Sanchez, C. Chakaberia, I. Chakraborty, P. Chandra, S. Chapeland, S. Chartier, M. Chattopa A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation Yerevan Armenia AGH University of Krakow Cracow Poland Bogolyubov Institute for Theoretical Physics National Academy of Sciences of Ukraine Kiev Ukraine Bose Institute Department of Physics Centre for Astroparticle Physics and Space Science (CAPSS) Kolkata India California Polytechnic State University San Luis Obispo CA United States Central China Normal University Wuhan China Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN) Havana Cuba Centro de Investigación y de Estudios Avanzados (CINVESTAV) Mexico City and Mérida Mexico Chicago State University Chicago IL United States China Institute of Atomic Energy Beijing China Chungbuk National University Cheongju South Korea Comenius University Bratislava Faculty of Mathematics Physics and Informatics Bratislava Slovakia COMSATS University Islamabad Islamabad Pakistan Creighton University Omaha NE United States Department of Physics Aligarh Muslim University Aligarh India Department of Physics Pusan National University Pusan South Korea Department of Physics Sejong University Seoul South Korea Department of Physics University of California Berkeley CA United States Department of Physics University of Oslo Oslo Norway Department of Physics and Technology University of Bergen Bergen Norway Dipartimento di Fisica Università di Pavia Pavia Italy Dipartimento di Fisica dell'Università Sezione INFN Cagliari Italy Dipartimento di Fisica dell'Università Sezione INFN Trieste Italy Dipartimento di Fisica dell'Università Sezione INFN Turin Italy Dipartimento di Fisica e Astronomia dell'Università Sezione INFN Bologna Italy Dipartimento di Fisica e Astronomia dell'Università Sezione INFN Catania Italy Dipartimento di Fisica e Astronomia dell'Università Sezione INFN Padova Italy Dipartimento di Fisica ‘E.R. Caianiello’ dell'Università Gruppo Collegato INFN Salerno Italy Dipartimento DISAT del Politecnico

The first measurement of the polarisation of coherently photoproduced J/ψ mesons in ultra-peripheral Pb–Pb collisions, using data at sNN=5.02 TeV, is presented. The J/ψ meson is measured via its dimuon decay channe...

The first measurement of the polarisation of coherently photoproduced J/ψ mesons in ultra-peripheral Pb–Pb collisions, using data at s_NN=5.02 TeV, is presented. The J/ψ meson is measured via its dimuon decay channel in the forward rapidity interval −4.0−1 ± 5% (syst) is analysed. Hadronic activity is highly suppressed since the interaction is mediated by a photon. The polar and azimuthal angle distributions of the decay muons are measured, and the polarisation parameters λ_θ, λ_φ, λ_θφ are extracted. The analysis is carried out in the helicity frame. The results are found to be consistent with a transversely polarised J/ψ. These values are compared with previous measurements by the H1 and ZEUS experiments. The polarisation parameters of coherent J/ψ photoproduction in Pb–Pb collisions are found to be consistent with the s-channel helicity conservation hypothesis. © 2025 CERN for the benefit of the ALICE Collaboration

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High-temperature quantum anomalous hall insulators in lithium-decorated iron-based superconductor materials

arXiv

引用

arXiv 2019年

作者： Li, Yang LiJ., Jiaheng. Li, Yang Ye, Meng Zheng4, Fawei Zhang, Zetao Fu123, Jingheng Duan, Wenhui Xu, Yong State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics Tsinghua University Beijing100084 China Frontier Science Center for Quantum Information Beijing China Collaborative Innovation Center of Quantum Matter Beijing100084 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Institute for Advanced Study Tsinghua University Beijing100084 China Beijing Academy of Quantum Information Sciences Beijing100193 China Wako Saitama351-0198 Japan

Quantum anomalous Hall (QAH) insulator is the key material to study emergent topological quantum effects, but its ultralow working temperature limits experiments. Here, by first-principles calculations, we find a family of stable two-dimensional (2D) structures generated by lithium decoration of layered iron-based superconductor materials FeX (X = S, Se, Te), and predict room-temperature ferromagnetic semiconductors together with large-gap high-Chern-number QAH insulators in the 2D materials. The extremely robust ferromagnetic order is induced by the electron injection from Li to Fe and stabilized by strong ferromagnetic kinetic exchange in the 2D Fe layer. While in the absence of spin-orbit coupling (SOC), the ferromagnetism polarizes the system into a half Dirac semimetal state protected by mirror symmetry, the SOC effect results in a spontaneous breaking of mirror symmetry and introduces a Dirac mass term, which creates QAH states with sizable gaps (several tens of meV) and multiple chiral edge modes. We also find a 3D QAH insulator phase featured by macroscopic number of chiral conduction channels in bulk LiOH-LiFeX. The findings open new opportunities to realize novel QAH physics and applications at high temperature. Copyright © 2019, The Authors. All rights reserved.

关键词： Ferromagnetism

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phq: a Fortran code to compute phonon quasiparticle properties and dispersions

arXiv

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arXiv 2019年

作者： Zhang, Z. Zhang, D.-B. Sun, T. Wentzcovitch, R.M. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Beijing Computational Science Research Center Beijing100193 China College of Nuclear Science and Technology Beijing Normal University Beijing100875 China Key Laboratory of Computational Geodynamics Chinese Academy of Sciences Beijing100049 China Department of Earth and Environmental Sciences Lamont-Doherty Earth Observatory Columbia University New YorkNY10964 United States

We here introduce a Fortran code that computes anharmonic free energy of solids from first-principles based on our phonon quasiparticle approach. In this code, phonon quasiparticle properties, i.e., renormalized phonon frequencies and lifetimes, are extracted from mode-projected velocity auto-correlation functions (VAF) of modes sampled by molecular dynamics (MD) trajectories. Using renormalized frequencies as input, the code next constructs an effective harmonic force constant matrix to calculate anharmonic phonon dispersions over the whole Brillouin zone and thus the anharmonic free energy in the thermodynamic limit (N → ∞). We illustrate the use of this code to compute ab initio temperature-dependent anharmonic phonons of Si in the diamond structure. Copyright © 2019, The Authors. All rights reserved.

关键词： Phonons

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Martingale solutions for the three-dimensional stochastic nonhomogeneous incompressible navier-stokes equations driven by Lévy processes

arXiv

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arXiv 2018年

作者： Chen, Robin Ming Wang, Dehua Wang, Huaqiao Department of Mathematics University of Pittsburgh PittsburghPA15260 United States Institute of Applied Physics and Computational Mathematics Beijing100088 China

In this paper, the three-dimensional stochastic nonhomogeneous incompressible Navier-Stokes equations driven by Lévy process consisting of the Brownian motion, the compensated Poisson random measure and the Poisson random measure are considered in a bounded domain. We obtain the existence of martingale solutions. The construction of the solution is based on the classical Galerkin approximation method, stopping time, the compactness method and the Jakubowski-Skorokhod theorem. Copyright © 2018, The Authors. All rights reserved.

关键词： Stochastic systems

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Electron correlation from strong field ionization of noble gas atoms subject to intense laser field 9

Electron correlation from strong field ionization of noble g...

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9th International Symposium on Ultrafast Phenomena and Terahertz Waves, ISUPTW 2018

作者： Quan, Wei Hao, XiaoLei Wang, YanLan Lai, XuanYang Li, WeiDong Becker, Wilhelm Wu, Yong Wang, JianGuo Chen, Jing Liu, XiaoJun State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan China Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan430071 China Institute of Theoretical Physics Department of Physics Shanxi University Taiyuan030006 China Max-Born-Institut Max-Born-Strasse 2a Berlin12489 Germany Institute of Applied Physics and Computational Mathematics P. O. Box 8009 Beijing100088 China

Electron-electron correlation is revealed in nonsequential double ionization (NSDI) of noble gas atoms subject to intense laser fields experimentally and theoretically. A novel laser-induced inelastic diffraction sche... 详细信息

ISBN: (纸本)9780960038084

关键词： Electron correlations

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A multi-frequency study of sub-parsec jets with the Event Horizon Telescope

arXiv

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arXiv 2025年

作者： Röder, Jan Wielgus, Maciek Lobanov, Andrei P. Krichbaum, Thomas P. Nair, Dhanya G. Lee, Sang-Sung Ros, Eduardo Fish, Vincent L. Blackburn, Lindy Chan, Chi-Kwan Issaoun, Sara Janssen, Michael Johnson, Michael D. Doeleman, Sheperd S. Bower, Geoffrey C. Crew, Geoffrey B. Tilanus, Remo P.J. Savolainen, Tuomas Impellizzeri, C.M. Violette Alberdi, Antxon Baczko, Anne-Kathrin Gómez, José L. Lu, Ru-Sen Paraschos, Georgios F. Traianou, Efthalia Goddi, Ciriaco Kim, Daewon Lisakov, Mikhail Kovalev, Yuri Y. Voitsik, Petr A. Sokolovsky, Kirill V. Akiyama, Kazunori Albentosa-Ruíz, Ezequiel Alef, Walter Algaba, Juan Carlos Anantua, Richard Asada, Keiichi Azulay, Rebecca Bach, Uwe Ball, David Baloković, Mislav Bandyopadhyay, Bidisha Barrett, John Bauböck, Michi Benson, Bradford A. Bintley, Dan Blundell, Raymond Bouman, Katherine L. Bremer, Michael Brinkerink, Christiaan D. Brissenden, Roger Britzen, Silke Broderick, Avery E. Broguiere, Dominique Bronzwaer, Thomas Bustamante, Sandra Byun, Do-Young Carlstrom, John E. Ceccobello, Chiara Chael, Andrew Chang, Dominic O. Chatterjee, Koushik Chatterjee, Shami Chen, Ming-Tang Chen, Yongjun Cheng, Xiaopeng Cho, Ilje Christian, Pierre Conroy, Nicholas S. Conway, John E. Cordes, James M. Crawford, Thomas M. Cruz-Osorio, Alejandro Cui, Yuzhu Curd, Brandon Dahale, Rohan Davelaar, Jordy De Laurentis, Mariafelicia Deane, Roger Dempsey, Jessica Desvignes, Gregory Dexter, Jason Dhruv, Vedant Dihingia, Indu K. Dougall, Sean Taylor Dzib, Sergio A. Eatough, Ralph P. Emami, Razieh Falcke, Heino Farah, Joseph Fomalont, Edward H. Ford, Alyson Foschi, Marianna Fraga-Encinas, Raquel Freeman, William T. Friberg, Per Fromm, Christian M. Fuentes, Antonio Galison, Peter Gammie, Charles F. García, Roberto Gentaz, Olivier Georgiev, Boris Gold, Roman Gómez-Ruiz, Arturo I. Gu, Minfeng Gurwell, Mark Hada, Kazuhiro Haggard, Daryl Haworth, Kari Hecht, Michael H. Hesper, Ronald Heumann, Dirk Ho, Luis C. Ho, Paul Honma, Mareki Huang, Chih-Wei L. Huang, Lei Hughes, David H. Ikeda, Shiro Inoue, Makoto James, David J. Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n GranadaE-18008 Spain Astronomy Department Universidad de Concepción Casilla 160-C Concepción Chile Korea Astronomy and Space Science Institute Daedeok-daero 776 Yuseong-gu Daejeon34055 Korea Republic of Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road WestfordMA01886 United States Black Hole Initiative Harvard University 20 Garden Street CambridgeMA02138 United States Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Ave. TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States NASA Hubble Fellowship Program United States Radboud University P.O. Box 9010 Nijmegen6500 GL Netherlands Institute of Astronomy and Astrophysics Academia Sinica 645 N. A’ohoku Place HiloHI96720 United States Department of Physics and Astronomy University of Hawaii at Manoa 2505 Correa Road HonoluluHI96822 United States Leiden Observatory Leiden University Postbus 2300 Leiden9513 RA Netherlands Postbus 93138 Den Haag2509 AC Netherlands Aalto University Department of Electronics and Nanoengineering PL 15500 AaltoFI-00076 Finland Aalto University Metsähovi Radio Observatory Metsähovintie 114 KylmäläFI-02540 Finland National Radio Astronomy Observatory 520 Edgemont Road CharlottesvilleVA22903 United States Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-43992 Sweden Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Key Laboratory of Radio Astronomy Chinese Academy of Scien

Context. The 2017 observing campaign of the Event Horizon Telescope (EHT) delivered the first very long baseline interferometry (VLBI) images at the observing frequency of 230 GHz, leading to a number of unique studies on black holes and relativistic jets from active galactic nuclei (AGN). In total, eighteen sources were observed, including the main science targets, Sgr A* and M 87 and various calibrators. Sixteen sources were AGN. Aims. We investigated the morphology of the sixteen AGN in the EHT 2017 data set, focusing on the properties of the VLBI cores: size, flux density, and brightness temperature. We studied their dependence on the observing frequency in order to compare it with the Blandford-Königl (BK) jet model. In particular, we aimed to study the signatures of jet acceleration and magnetic energy conversion. Methods. We modeled the source structure of seven AGN in the EHT 2017 data set using linearly polarized circular Gaussian components (1749+096, 1055+018, BL Lac, J0132–1654, J0006–0623, CTA 102, 3C 454.3) and collected results for the other nine AGN from dedicated EHT publications, complemented by lower frequency data in the 2-86 GHz range. Combining these data into a multi-frequency EHT+ data set, we studied the dependences of the VLBI core component flux density, size, and brightness temperature on the frequency measured in the AGN host frame (and hence on the distance from the central black hole), characterizing them with power law fits. We compared the observations with the BK jet model and estimated the magnetic field strength dependence on the distance from the central black hole. Results. Our observations spanning event horizon- to parsec scales indicate a deviation from the standard BK model, particularly in the decrease of the brightness temperature with the observing frequency. Only some of the discrepancies may be alleviated by tweaking the model parameters or the jet collimation profile. Either bulk acceleration of the jet material, energ

关键词： Luminance

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DeePCG: Constructing coarse-grained models via deep neural networks

arXiv

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arXiv 2018年

作者： Weinan, E. Zhang, Linfeng Han, Jiequn Wang, Han Car, Roberto Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China Caep Software Center for High Performance Numerical Simulation Huayuan Road 6 Beijing100088 China Program in Applied and Computational Mathematics Princeton Institute for Science and Technology of Materials Princeton University PrincetonNJ08544 United States Department of Mathematics and Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Beijing Institute of Big Data Research Beijing100871 China

We introduce a general framework for constructing coarse-grained potential models without ad hoc approximations such as limiting the potential to two- A nd/or three-body contributions. The scheme, called Deep Coarse-Grained Potential (abbreviated DeePCG), exploits a carefully crafted neural network to construct a many-body coarse-grained potential. The network is trained with full atomistic data in a way that preserves the natural symmetries of the system. The resulting model is very accurate and can be used to sample the configurations of the coarse-grained variables in a much faster way than with the original atomistic model. As an application we consider liquid water and use the oxygen coordinates as the coarse-grained variables, starting from a full atomistic simulation of this system at the ab initio molecular dynamics level. We find that the two-body, three-body, and higher-order oxygen correlation functions produced by the coarse-grained and full atomistic models agree very well with each other, illustrating the effectiveness of the DeePCG model on a rather challenging task. Copyright © 2018, The Authors. All rights reserved.

关键词： Deep neural networks

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First Very Long Baseline Interferometry Detections at 870 µm

arXiv

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arXiv 2024年

作者： Raymond, Alexander W. Doeleman, Sheperd S. Asada, Keiichi Blackburn, Lindy Bower, Geoffrey C. Bremer, Michael Broguiere, Dominique Chen, Ming-Tang Crew, Geoffrey B. Dornbusch, Sven Fish, Vincent L. García, Roberto Gentaz, Olivier Goddi, Ciriaco Han, Chih-Chiang Hecht, Michael H. Huang, Yau-De Janssen, Michael Keating, Garrett K. Koay, Jun Y.I. Krichbaum, Thomas P. Lo, Wen-Ping Matsushita, Satoki Matthews, Lynn D. Moran, James M. Norton, Timothy J. Patel, Nimesh Pesce, Dominic W. Ramakrishnan, Venkatessh Rottmann, Helge Roy, Alan L. Sánchez, Salvador Tilanus, Remo P.J. Titus, Michael Torne, Pablo Wagner, Jan Weintroub, Jonathan Wielgus, Maciek Young, André Akiyama, Kazunori Albentosa-Ruíz, Ezequiel Alberdi, Antxon Alef, Walter Algaba, Juan Carlos Anantua, Richard Azulay, Rebecca Bach, Uwe Baczko, Anne-Kathrin Ball, David Baloković, Mislav Bandyopadhyay, Bidisha Barrett, John Bauböck, Michi Benson, Bradford A. Bintley, Dan Blundell, Raymond Bouman, Katherine L. Boyce, Hope Brissenden, Roger Britzen, Silke Broderick, Avery E. Bronzwaer, Thomas Bustamante, Sandra Carlstrom, John E. Chael, Andrew Chan, Chi-Kwan Chang, Dominic O. Chatterjee, Koushik Chatterjee, Shami Chen, Yongjun Cheng, Xiaopeng Cho, Ilje Christian, Pierre Conroy, Nicholas S. Conway, John E. Crawford, Thomas M. Cruz-Osorio, Alejandro Cui, Yuzhu Dahale, Rohan Davelaar, Jordy de Laurentis, Mariafelicia Deane, Roger Dempsey, Jessica Desvignes, Gregory Dexter, Jason Dhruv, Vedant Dihingia, Indu K. Dzib, Sergio A. Eatough, Ralph P. Emami, Razieh Falcke, Heino Farah, Joseph Fomalont, Edward Fontana, Anne-Laure Ford, H. Alyson Foschi, Marianna Fraga-Encinas, Raquel Freeman, William T. Friberg, Per Fromm, Christian M. Fuentes, Antonio Galison, Peter Gammie, Charles F. Georgiev, Boris Gold, Roman Gómez-Ruiz, Arturo I. Gómez, José L. Gu, Minfeng Gurwell, Mark Hada, Kazuhiro Haggard, Daryl Hesper, Ronald Heumann, Dirk Ho, Luis C. Ho, Paul Honma, Mareki Huang, Chih-Wei L. Huang, Lei Hughes, David H. Ikeda, Shiro Impellizzeri, C.M. Violette Inoue, Makoto Issaoun, Black Hole Initiative at Harvard University 20 Garden Street CambridgeMA02138 United States Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. 4 Roosevelt Rd. Taipei106216 Taiwan Institute of Astronomy and Astrophysics Academia Sinica 645 N. A’ohoku Place HiloHI96720 United States Department of Physics and Astronomy University of Hawaii at Manoa 2505 Correa Road HonoluluHI96822 United States Institut de Radioastronomie Millimétrique 300 rue de la Piscine Saint Martin d’HèresF-38406 France Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road WestfordMA01886 United States Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Dipartimento di Fisica Università degli Studi di Cagliari SP Monserrato-Sestu km 0.7 MonserratoI-09042 Italy INAF - Osservatorio Astronomico di Cagliari Via della Scienza 5 CA Selargius09047 Italy Radboud University P.O. Box 9010 Nijmegen6500 GL Netherlands Department of Physics National Taiwan University No.1 Sect.4 Roosevelt Rd. Taipei106216 Taiwan Astronomy Department Universidad de Concepción Casilla 160-C Concepción Chile Finnish Centre for Astronomy with ESO University of Turku FI-20014 Finland Aalto University Metsähovi Radio Observatory Metsähovintie 114 KylmäläFI-02540 Finland Institut de Radioastronomie Millimétrique Avenida Divina Pastora 7 Local 20 GranadaE-18012 Spain Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Departament d’Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 Burjassot ValènciaE-46100 Spain Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n GranadaE-18008 Spain Department of Phy

The first very long baseline interferometry (VLBI) detections at 870 µm wavelength (345 GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from the surface of the Earth, and the highest-frequency example of the VLBI technique to date. These include strong detections for multiple sources observed on inter-continental baselines between telescopes in Chile, Hawaii, and Spain, obtained during observations in October 2018. The longest-baseline detections approach 11 Gλ corresponding to an angular resolution, or fringe spacing, of 19 µas. The Allan deviation of the visibility phase at 870 µm is comparable to that at 1.3 mm on the relevant integration time scales between 2 and 100 s. The detections confirm that the sensitivity and signal chain stability of stations in the Event Horizon Telescope (EHT) array are suitable for VLBI observations at 870 µm. Operation at this short wavelength, combined with anticipated enhancements of the EHT, will lead to a unique high angular resolution instrument for black hole studies, capable of resolving the event horizons of supermassive black holes in both space and time. © 2024, CC BY.

关键词： Black holes

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A Few Benchmark Test Cases for Higher-Order Euler Solvers

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高等学校计算数学学报（英文版） 2017年第4期10卷 711-736页

作者： Liang Pan Jiequan Li Kun Xu Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing China Department of Mathematics Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Department of Mechanical and Aerospace Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

There have been great efforts on the development of higher-order numerical schemes for compressible Euler equations in recent *** traditional test cases proposed thirty years ago mostly target on the strong shock interactions,which may not be adequate enough for evaluating the performance of current higher-order *** order to set up a higher standard for the development of new algorithms,in this paper we present a few benchmark cases with severe and complicated wave structures and interactions,which can be used to clearly distinguish different kinds of higher-order *** tests are selected so that the numerical settings are very simple and any higher order scheme can be straightforwardly applied to these *** examples include highly oscillatory solutions and the large density ratio problem in one dimensional *** two dimensions,the cases include hurricane-like solutions;interactions of planar contact discontinuities with asymptotic large Mach number (the composite of entropy wave and vortex sheets);interaction of planar rarefaction waves with transition from continuous flows to the presence of shocks;and other types of interactions of two-dimensional planar *** get good performance on all these cases may push algorithm developer to seek for new methodology in the design of higher-order schemes,and improve the robustness and accuracy of higher-order schemes to a new level of *** order to give reference solutions,the fourth-order gas-kinetic scheme (GKS) will be used to all these benchmark cases,even though the GKS solutions may not be very accurate in some *** main purpose of this paper is to recommend other CFD researchers to try these cases as well,and promote further development of higher-order schemes.

关键词： Euler equations two-dimensional Riemann problems fourth-order gas-kinetic scheme wave interactions

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HYPOTHETICAL HYPERBOLIC ENCOUNTERS BETWEEN VENUS AND PROTO-MERCURY THAT PARTIALLY STRIPPED AWAY PROTO-MERCURY’S MANTLE

arXiv

引用

arXiv 2019年

作者： Deng, Hongping Department of Applied Mathematics and Theoretical Physics University of Cambridge Centre for Mathematical Sciences Wilberforce Road CambridgeCB3 0WA United Kingdom Center for Theoretical Astrophysics and Cosmology Institute for Computational Science University of Zurich Winterthurerstrasse 190 Zurich8057 Switzerland

Mercury has an unusually large metal core comprising ∼70% of its mass comparing to all other terrestrial planets in the solar system. Giant impacts can remove a significant fraction of the silicate mantle of a chondritic proto-Mercury and form the iron rich present-day Mercury. However, such high-temperature giant impacts seem at odds with the retainment of moderately volatile elements on present-day Mercury (Peplowski et al. 2011). We simulated a series of hyperbolic encounters between proto-Mercury and proto-Venus, which may occur in the chaotic early solar system. Tidal disruption of proto-Mercury always removes part of its silicate mantle while its iron core remains intact. We find, in favourable cases, four close encounters with fast spinning projectiles (resulting from previous encounters) can lead to present-day Mercury iron fraction. More encounters are needed when the spin and orbital angular momentum are not always aligned. These hyperbolic encounters have various outcomes, such as orbital decay, binary planets and change of spin rates. These results suggest the importance of proper treatment of close encounters in N-body simulations of planetary accretion. Copyright © 2019, The Authors. All rights reserved.

关键词： Planets

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