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Inconsistencies in four-dimensional Einstein-Gauss-Bonnet gravity

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Chinese Physics C 2021年第1期45卷 89-96页

作者： Julio Arrechea Adria delhom Alejandro Jimenez-Cano instituto de astrofisica de andalucia(IAA-csic) Glorieta de la AstronomiaGranadaSpain departamento de Fisica Teorica and IFIC Centro Mixto Universidad de Valencia-CSIC.Universidad de ValenciaBuijassot-46100ValenciaSpain departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada18071 GranadaSpain

We attempt to clarify several aspects concemi ng the recently presented four-dimensional Ein stein-Gauss-Bonnet gravity.We argue that the limiting procedure outlined in[Phys.Rev.Lett.124,081301(2020)]generally involves ill-defined terms in the four dimensional field equations.Potential ways to circumvent this issue are discussed,alongside remarks regarding specific solutions of the theory.We prove that,although linear perturbations are well behaved around maximally symmetric backgrounds,the equations for second-order perturbations are illdefined even around a Minkowskia n background.Additi on ally,we perform a detailed analysis of the spherically symmetric solutions and find that the central curvature singularity can be reached within a finite proper time.

关键词： alternative theories of gravity singularities Einstein・Gauss-Bonnet

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Observatory science with eXTP

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Science China(Physics,Mechanics & Astronomy) 2019年第2期62卷 97-138页

作者： Jean J.M.in 't Zand Enrico Bozzo JinLu Qu Xiang-Dong Li Lorenzo Amati Yang Chen Immacolata Donnarumma Victor Doroshenko Stephen A.Drake Margarita Hernanz Peter A.Jenke Thomas J.Maccarone Simin Mahmoodifar Domitilla de Martino Alessandra de Rosa Elena M.Rossi Antonia Rowlinson Gloria Sala Giulia Stratta Thomas M.Tauris Joern Wilms XueFeng Wu Ping Zhou Iván Agudo Diego Altamirano Jean-Luc Atteia Nils A.andersson M.Cristina Baglio David R.Ballantyne Altan Baykal Ehud Behar Tomaso Belloni Sudip Bhattacharyya Stefano Bianchi Anna Bilous Pere Blay Joao Braga Sφren Brandt Edward F.Brown Niccolo Bucciantini Luciano Burderi Edward M.Cackett Riccardo Campana Sergio Campana Piergiorgio Casella Yuri Cavecchi Frank Chambers Liang Chen Yu-Peng Chen Jér?me Chenevez Maria Chernyakova ChiChuan Jin Riccardo Ciolfi Elisa Costantini Andrew Cumming Antonino D'Aì Zi-Gao Dai Filippo D'Ammando Massimiliano de Pasquale Nathalie degenaar Melania del Santo Valerio D'Elia Tiziana Di Salvo Gerry Doyle Maurizio Falanga XiLong Fan Robert D.Ferdman Marco Feroci Federico Fraschetti Duncan K.Galloway Angelo F.Gambino Poshak Gandhi MingYu Ge Bruce Gendre Ramandeep Gill Diego G?tz Christian Gouiffès Paola Grandi Jonathan Granot Manuel Güdel Alexander Heger Craig O.Heinke Jeroen Homan Rosario Iaria Kazushi Iwasawa Luca Izzo Long Ji Peter G.Jonker Jordi José Jelle S.Kaastra Emrah Kalemci Oleg Kargaltsev Nobuyuki Kawai Laurens Keek Stefanie Komossa Ingo Kreykenbohm Lucien Kuiper devaky Kunneriath Gang Li En-Wei Liang Manuel Linares Francesco Longo FangJun Lu Alexander A.Lutovinov denys Malyshev Julien Malzac Antonios Manousakis Ian McHardy Missagh Mehdipour YunPeng Men Mariano Méndez Roberto P.Mignani Romana Mikusincova M.Coleman Miller Giovanni Miniutti Christian Motch Joonas Nättilä Emanuele Nardini Torsten Neubert Paul T.O'Brien Mauro Orlandini Julian P.Osborne Luigi Pacciani Stéphane Paltani Maurizio Paolillo Iossif E.Papadakis Biswajit Paul Alberto Pellizzoni Uria Peretz Miguel A.Pérez Torres Emanuele Perinati Chanda Prescod-Weinstein Pablo Reig SRON Netherlands Institute for Space Research department of Astronomy University of Geneva Key Laboratory for Particle Astrophysics Institute of High Energy PhysicsChinese Academy of Sciences School of Astronomy and Space Science Nanjing University INAF-IASF Bologna ASI Via del Politecnico snc INAF-Istituto di astrofisica e Planetologie Spaziali Institut für Astronomie und Astrophysik Tübingen Universit?t Tübingen NASA Goddard Space Flight Center ICREA&Institute of Space Sciences(IEEC-csic) Campus UABCarrer de Can Magrans CSPAR SPA University of Alabama in Huntsville department of Physics Texas Tech University INAF Osservatorio Astronomico di Capodimonte Leiden Observatory Leiden University Anton Pannekoek Institute University of Amsterdam ASTRON Netherlands Institute for Radio Astronomy Universitat Politecnica de Catalunya(UPC-IEEC) Universitádegli Studi di Urbino‘Carlo Bo’ Max-Planck-Institut für Radioastronomie Dr.Karl-Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics(ECAP) Friedrich Alexander Universit?t Erlangen-Nurnberg Purple Mountain Observatory Chinese Academy of Sciences instituto de astrofysíca de andalucia-csic department of Physics and Astronomy University of Southampton IRAP Universitéde ToulouseCNRSUPSCNES Mathematical Sciences and STAG Research Centre University of Southampton New York University Abu Dhabi Center for Relativistic Astrophysics School of PhysicsGeorgia Institute of Technology Physics department Middle East Technical University department of Physics Technion-Israel Institute of Technology INAF Osservatorio Astronomico di Brera Tata Institute of Fundamental Research Dipartimento di Matematica e Fisica Universitàdegli Studi Roma Tre instituto de astrofísica de Canarias instituto Nacional de Pesquisas Espaciais-INPE National Space Institute Technical University of Denmark(DTU Space) department of Physics and Astronomy Michigan State University INAF Osservatorio astrofisico di Arcetri Dipartimento di Fisica Universitádegli Studi di Cagliari department of Physics and A

In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.

关键词： space research in struments nuclear astrophysics flare stars accretion and accretion disks mass loss and stellar winds cataclysmic binaries X-ray binaries supernova remnants active galactic nuclei X-ray bursts gamma-ray bursts gravitational waves

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East Asian VLBI Network observations of active galactic nuclei jets:imaging with KaVA+Tianma+Nanshan

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Research in Astronomy and Astrophysics 2021年第8期21卷 220-234页

作者：崔玉竹 Kazuhiro Hada Motoki Kino Bong-Won Sohn Jongho Park Hyun-Wook Ro Satoko Sawada-Satoh Wu Jiang Lang Cui Mareki Honma 沈志强 Fumie Tazaki 安涛 Ilje Cho Guang-Yao Zhao Xiao-Peng Cheng Kotaro Niinuma Kiyoaki Wajima Ying-Kang Zhang Noriyuki Kawaguchi Juan-Carlos Algaba Shoko Koyama Tomoya Hirota Yoshinori Yonekura Nobuyuki Sakai Bo Xia Yong-Bin Jiang Lin-Feng Yu Wei Gou Ju-Yeon Hwang Yong-Chen Jiang Yun-Xia Sun Dong-Kyu Jung Hyo-Ryoung Kim Jeong-Sook Kim Hideyuki Kobayashi Jee-Won Lee Jeong-Ae Lee Hua Zhang Guang-Hui Li Zhi-Qiang Xu Peng Li Jung-Hwan Oh Se-Jin Oh Chung-Sik Oh Tomoaki Oyama Duk-Gyoo Roh Katsunori-M.Shibata 郭文 Rong-Bing Zhao Wei-Ye Zhong Jin-Qing Wang Wen-Jun Yang 闫浩 Jae-Hwan Yeom Bin Li 李笑飞 Jian-Ping Yuan Jian Dong Zhong Chen Kazunori Akiyama Keiichi Asada Do-Young Byun Yoshiaki Hagiwara Jeffrey Hodgson Tae-Hyun Jung Kee-Tae Kim Sang-Sung Lee Kunwoo Yi Qing-Hui Liu Xiang Liu Ru-Sen Lu Masanori Nakamura Sascha Trippe Na Wang Xue-Zheng Wang 张波 department of Astronomical Science The Graduate University for Advanced StudiesSOKENDAI2-21-1 OsawaMitakaTokyo 181-8588Japan Mizusawa VLBI Observatory National Astronomical Observatory of Japan2-12 HoshigaokaMizusawaOshuIwate 023-0861Japan Kogakuin University of Technology and Engineering Academic Support Center2665-1 NakanoHachiojiTokyo 192-0015Japan Korea Astronomy and Space Science Institute Yuseong-guDaejeon 34055Korea department of Astronomy Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Korea department of Astronomy and Space Science University of Science and Technology217 Gajeong-roDaejeonKorea Institute of Astronomy and Astrophysics Academia Sinica645 N Aohoku PIHiloHI 96720USA Graduate School of Sciences and Technology for Innovation Yamaguchi UniversityYoshida 1677-1YamaguchiYamaguchi 753-8512Japan Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesNanjing 210008China Institute of Astronomy The University of Tokyo2-21-1 OsawaMitakaTokyo 181-0015Japan instituto de astrofísica de andalucía-csic Glorieta de la Astronomia s/nGranada E-18008Spain department of Physics Faculty of ScienceUniversity of MalayaKuala Lumpur 50603Malaysia Center for Astronomy Ibaraki University2-1-1 BunkyoMitoIbaraki 310-8512Japan Space Light Laboratory 77Yangjaedae-ro 86 roadGangdong-guSeoulKorea Massachusetts Institute of Technology Haystack Observatory 99 Millstone RoadWestfordMA 01886USA National Radio Astronomy Observatory 520 Edgemont RdCharlottesvilleVA 22903USA Toyo University 5-28-20 HakusanBunkyo-kuTokyo 112-8606Japan department of Physics and Astronomy Seoul National UniversityGwanak-guSeoul 08826Korea Max Planck Institute for Radio Astronomy Auf dem hiigel 69Bonn 53121Germany SNU Astronomy Research Center Seoul National UniversityGwanak-guSeoul 08826Korea

The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions.After the combination of the Korean VLBI Network(KVN) and the VLBI Exploration of Radio Astrometry(VERA) into Ka VA,further expansion with the joint array in East Asia is actively promoted.Here we report the first imaging results(at 22 and 43 GHz) of bright radio sources obtained with Ka VA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China.To test the EAVN imaging performance for different sources,we observed four active galactic nuclei(AGN) having different brightness and morphology.As a result,we confirmed that the Tianma 65-m Radio Telescope(TMRT) significantly enhances the overall array sensitivity,a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of Ka VA only.The addition of the Nanshan 26-m Radio Telescope(NSRT) further doubled the east-west angular resolution.With the resulting high-dynamic-range,high-resolution images with EAVN(Ka VA+TMRT+NSRT),various fine-scale structures in our targets,such as the counter-jet in M87,a kink-like morphology of the 3 C 273 jet and the weak emission in other sources are successfully detected.This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general.Ongoing expansion of EAVN will further enhance the angular resolution,detection sensitivity and frequency coverage of the network.

关键词： galaxies:active galaxies:jets instrumentation:interferometers radio continuum:galaxies

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A very energetic supernova associated with the γ-ray burst of 29 March 2003

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A very energetic supernova associated with the γ-ray burst ...