Einstein predicted the existence of gravitational waves in 1916, and the LIGO（Laser Interferometer Gravitational Wave Observatory）Collaboration announced the first direct detection of gravitational waves in human history on 11th February,2016 after a century’s exploration, which opens a new window to explore the universe. The detection of gravitational wave signals in the low and mid-frequency bands is needed in order to hear the motions of more massive objects. There are a lots of new gravitational waves sources in this band, which require the construction of space-based gravitational wave observatories. Taiji Program proposed by Chinese scientists is one of the space-based GW detection plans, which is proposed to launch three spacecrafts which will form an equilateral triangle in orbit around the Sun, with 3million kilometers length of each side, composing three sets of Michelson Interferometers.Taiji ProgramTaiji-1, as the technology verification satellite of the Taiji Program, was successfully launched on August 31, 2019, and has completed verification on key technologies, taking the first step towards China’s space-borne gravitational waves detection. The Gravity Reference Sensor (GRS), a main payload of the Taiji-1 satellite, is the endpoint and reference of the laser link of the future space-based gravitational wave detection satellite, to ensure that the test mass moves perfectly along the geodesic line, which is a prerequisite for the detection of gravitational wave signals. The inertial reference of the GRS is determined by the residual acceleration noise of its test mass, which means that the ambient noise need to be suppressed or subtracted.The calibration of the GW detection device’s core payload is a critical step in achieving the space-based GW detection. Recently, the research of calibration of the in-orbit center-of-mass of TaiJi-1 was published in Physical Review D [Phys. Rev. D 108 (2023) 082001]. Xiaotong Wei, a Ph.D. student of the class of 2020 at the International Center for Theoretical Physics-Asia-Pacific (ICTP-AP), is the first author and co-corresponding author of this paper, and his advisor, Prof. Jibo He, is the co-corresponding author as well. After calibration, the acceleration noise level of the gravitational reference sensor readout data in the medium-and-low-frequency band (0.001 to 0.1 Hz) was significantly reduced. The study was favorably reviewed by the referees of Physical Review D:“…Calibration of space-borne instruments is an important foundation for science…In general, the paper and the results are really good…”.This research was supported by the colleagues from the partner institutions of Taiji Alliance and the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS)(XDA15020700, XDA15021100), as well as the Special Funds of the Fundamental Research Funds for Central Universities from the Ministry of Education of the People's Republic of China.Download the paper: https://doi.org/10.1103/PhysRevD.108.082001Center-of-mass calibration before (red dashed line) and after (blue) GRS triaxial readout of acceleration amplitude spectrum density
Various observations from particle physics, astrophysics, and cosmology have suggested that the standard model of particle physics for describing the microscopic structure of matter is not complete. It is then one of the vital scientific problems of current particle physics and cosmological observations to search for the signals of new physics beyond the standard model of particle physics. Many new physics models beyond the standard model of particle physics predict the cosmological first-order phase transitions during the evolution of our Universe. With the temperature decreasing due to the expansion of the Universe, symmetries at high energy scales would be broken simultaneously, and the associated quantum field would decay into the true vacuum from the false vacuum by quantum tunneling via the nucleation and expansion of true-vacuum bubbles, resulting in the energy transfer into the kinetic energy of bubble walls and background fluid, similar to the violent process of frozen ice from supercooling water. The following collisions among expanding bubbles would induce large fluctuations in the energy density. Therefore, as a violent process in the early Universe, the cosmological first-order phase transitions could produce various observational effects, including the stochastic gravitational wave background, primordial magnetic field, and baryon asymmetry, making it feasible to probe or constrain the new physics from astrophysical and cosmological observations. The gravitational-wave observation from cosmological first-order phase transition is also one of the main scientific targets of many gravitational-wave observational projects.Recently, the postdoc Dr. Jing Liu from the International Centre for Theoretical Physics Asia-Pacific of the University of Chinese Academy of Sciences, the associate researcher Prof. Ligong Bian from Chongqing University, the researchers Prof. Rong-Gen Cai, Prof. Zong-Kuan Guo, and the postdoc Dr. Shao-Jiang Wang from the Institute of Theoretical Physics of Chinese Academy of Sciences have proposed a new mechanism for the productions of primordial black holes, and given rise to rigorous constraints on the properties of cosmological first-order phase transitions from the astrophysical observational data. Due to the randomness of quantum tunneling, the progress of vacuum decay varies in different regions. Note that the false vacuum energy density barely changes with the cosmological expansion, while the energy densities of other matter components like radiations and cold dark matter are rapidly diluted with the expansion of the Universe. Therefore, the regions of vacuum decay that fall behind the others would admit higher energy densities after the phase transition. This is to say that the cosmological first-order phase transition would induce fluctuations in energy density. These high-energy-density regions would eventually produce primordial black holes via gravitational collapse, and these primordial black holes are almost monochromatic in their mass spectrum. The relevant paper has been published as a Letter in Phys. Rev.D 105 (2022) L021303. The primordial black holes produced with this mechanism and the associated gravitational waves could explain the merger rate of black hole binaries observed in LIGO-Virgo collaborations as well as the signal from the NANOGrav observation.They also discovered that the first-order phase transition could induce superhorizon curvature perturbations, and in turn probe and constrain the phase-transition properties from the observations of the curvature perturbations at small cosmological scales. The nucleation rate of true vacuum bubbles per unit time and per unit volume could be obtained from the quantum tunneling. After the phase transition, the regions with a scale larger than the product of phase-transition duration and light speed share no causal connection, and the causality requires the energy density spectrum of curvature perturbations to be proportional to the cube of wavenumber. Hence, if the superhorizon scale is considered, the induced curvature perturbations from phase transitions could largely surpass the primordial perturbations from the early-universe inflation so that it can be probed by various astrophysical observations, including the temperature anisotropies and spectrum distortion in the cosmic microwave background radiations and the number density in ultra-compact minihalos. In turn, we could also constrain the phase-transition properties via the upper bounds on the curvature perturbations from these astrophysical observations.Figure 1: Constraints on the parameter space of phase transition from different observations on the curvature perturbations, where alpha denotes the phase-transition strength, beta/H_* denotes the phase-transition rate, and T_* is the phase-transition temperature. The gray solid curves and gray dotted curves in the left and middle panels are constraints from the gravitational-wave background and big bang nucleosynthesis, respectively.They have obtained the power spectrum of the curvature perturbations induced from the first-order phase transitions, and for the first time given rise to rigorous constraints on the phase-transition parameters from the upper bounds on the curvature perturbations from astrophysical observations. The relevant paper has been published in Phys. Rev. Lett 130 (2023) 051001. As shown in Figure 1, all constraints on the cosmological first-order phase transitions below the electroweak scale are obtained from the upper bounds on the curvature perturbations from the big bang nucleosynthesis (blue curves), the temperature anisotropies and spectrum distortion in the cosmic microwave background radiations (green curves), and the number density in ultra-compact minihalos (orange solid curves from pulsar timing array and orange dashed curves from Gamma-ray detections). This study largely enhances the previous constraints from the stochastic gravitational-wave background (gray solid curves) and big bang nucleosynthesis (gray dotted curves) on the QCD first-order phase transition, low-energy dark-sector first-order phase transition, and some of the electroweak first-order phase transition, in particular the low-energy transitions and slow first-order phase transitions.This study is supported by relevant projects from the National Natural Science Foundation of China, the Ministry of Science and Technology of China, and the Chinese Academy of Sciences.Link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.051001Contact:Jing Liu: liujing@ucas.ac.cnInternational Centre for Theoretical Physics Asia-Pacific
International Journal of Modern Physics AVolume 36, Issue 11n12 (30 April 2021)Special Issue on Taiji Program in Space for Gravitational Universe with the First Run Key Technologies Test in Taiji-1 世界科学出版社的《现代物理国际期刊》（International Journal of Modern Physics A）以专辑形式发布了来自180余位研究人员，30余家合作单位的研究成果，以及“太极一号”卫星更为详尽的实验结果。本专辑的论文涵盖了干涉仪系统、引力参考传感器、微推进系统、无拖曳控制、超稳超静卫星技术等，并详细介绍了“太极一号”数据处理流程。S/NTitleAuthorsYear，Volume and Page1The pilot of Taiji program—From the ground to Taiji-2 The Taiji Scientific Collaboration2021,36,11 & 12, 2102001 (6 pages)2Taiji program in space for gravitational universe with the first run key technologies test in Taiji-1 The Taiji Scientific Collaboration2021,36,11 & 12,2102002 (2 pages)3Successful Application of Optical Bench in Taiji-1 Laser InterferometerThe Taiji Scientific Collaboration2021,36,11 & 12,2140001 (15 pages)4Exploration of the coupling between thrust and interference in Taiji-1The Taiji Scientific Collaboration2021,36,11 & 12,2140002 (11 pages)5Preliminary simulation analysis of the temperature fluctuation effect on Taiji-1 laser interferometerXiaoqin Deng,Yu Niu2021,36,11 & 12,2192001 (2 pages)6In-orbit performance of the laser interferometer of Taiji-1 experimental satellite.Heshan Liu, Sha Wei, Ziren Luo*.2021,36,11 & 12,2140004 (8 pages)7The phasemeter of Taiji-1 experimental satelliteZiren Luo, Tao Yu, Heshan Liu.2021,36,11 & 12,2140005 (7 pages)8High stability laser source for Taiji-1 satelliteGuangwei sun, dijun chen, weibiao chen2021,36,11 & 12,2140006 (7 pages)9A spaceborne neodymium-doped yttrium aluminum garnet laser with nonplanar-ring-oscillator configurationJ. Peng, L. Liufeng,and L. Chen2021,36,11 & 12,2140007 (7 pages)10Development and on orbit test of Taiji-1 inertial referenceWang, Z. , and J. G. Lei2021 Vol. 36, No. 11n12, 2140008 11Electronic noise analysis and in-orbit resolution verification of an electrostatic accelerometer Zuo-Lei Wan and Jian Min2021,36,11 & 12,2140009 (9 pages)12Implementation of High-precision Inertial Reference for Taiji-1 Satellite and Its Ground Evaluation Based on Torsion Pendulum SystemHua-Dong Li, Zhi Wang2021,36,11 & 12,, 214001013Performance tests and simulations for Taiji-1 inertial sensor Jian Min, Jun-Gang Lei，et al.2021,36,11 & 12,2140011 (13 pages)14Adaptive preload controller design and analysis for electrostatic suspension systemYukun Wang and Zhi Wang2021,36,11 & 12,2140012 (14 pages)15First result of orbit verification of Taiji-1 hall micro thruster.Xu S Y , Xu L X , Cong L X , Qiao C F.2021,36,11 & 12,2140013 (16 pages)16Ground performance tests and evaluation of RF ion microthrusters for Taiji-1 satelliteJian-Wu He, Li Duan and Qi Kang2021,36,11 & 12,2140014 (11 pages)17A torsional thrust stand for measuring the thrust response time of micro-Newton thrustersChao Yang, Jian-Wu He, Li Duan* and Qi Kang2021,36,11 & 12,2140015 (17 pages)18Ground semi-physical simulation experiment study of one-dimensional drag-free control Chu Zhang,Qi Kang2021,36,11 & 12,2140016 (24 pages)19The impact of neutralizer-free ignition of a radio frequency ion thruster on the lifetime of the ion optics system Long-Fei Ma, Qi Kang2021,36,11 & 12,2140017 (13 pages)20Design of high-resolution flow sensor used in cold gas micro propulsion system Xiaocheng Zhu,Xiaoliang Guo2021,36,11 & 12,2140018 (12 pages)21The drag-free control design and in-orbit experimental results of “Taiji-1”Zhiqiang Hu, Pengcheng Wang, Yueliang Wu, Qi Kang,Yonghe Zhang2021,36,11 & 12,2140019 (16 pages)22Satellite architecture and preliminary in-orbit experiment of Taiji-1Zhiming Cai, Jianfeng Deng, Jinpei Yu, Huawang Li，Xingjian Shi2021,36,11 & 12,2140020 (14 pages)23Key technologies analysis and design of ultra-clean & ultra-stable spacecraft for gravitational wave detectionKun Chen, Xiaofeng Zhang, Tong Guo, Zhi-Ming Cai2021,36,11 & 12,2140021 (11 pages)24Temperature stability of the Taiji-1 satellite in operational orbitXiaofeng Zhang, Hong Liang, Heping Tan, Jinchao Feng, Huawang Li2021,36,11 & 12,2140022 (13 pages)25Testing, modeling and estimation of Taiji-1’s in-orbit magnetic parameters magnetic parametersXingjian Shi* and Zhiming Cai2021,36,11 & 12,2140023 (7 pages)26A temperature measurement system with high resolution and low noiseBing Zhang, Xiaoyi Zhu, Xiaofeng Zhang, Bing Xue, Hong Liang, Jiang Li, Peng Su2021,36,11 & 12,2140024 (10 pages)27The pipeline of data processing for TAIJI-1 space mission in the TAIJI program for the detection of gravitational waveHongbo Jin, Peng Xu2021,36,11 & 12,2140025 (18 pages)28System modeling in data processing of Taiji-1 missionXiaodong Peng, Hongbo Jin, Peng Xu and et. al.2021,36,11 & 12,2140026 (23 pages)29Erratum Preliminary simulation analysis of the temperature fluctuation effect on Taiji-1 laser interferometerXiaoqin Deng,Yu Niu2021,36,11 & 12,2192001 (2 pages)论文下载：https://indico.ictp-ap.org/
2019年 12卷 第3期 “空间引力波探测”专栏聚焦空间引力波探测所需核心关键技术刊登了11篇论文 ，涉及惯性传感器技术、无拖曳控制技术、激光干涉测量技术、绝对距离测量及通信技术、卫星入轨误差分析以及极端质量比旋进系统高精度重校准引力波建模等，为后续引力波探测领域研究提供有益的参考。序号论文题目作者1 太极计划激光指向调控方案介绍高瑞弘,刘河山,罗子人,靳刚2应用于空间精密测量的全玻璃光纤耦合器的系统设计赵亚, 姚东, 王智, 方超, 李钰鹏3Highly accurate recalibrate waveforms for extreme-mass-ratio inspirals in effective-one-body framesCHENG Ran, HAN Wen-biao4电极不对称性对惯性传感器性能损失的研究王少鑫,齐克奇,王玉坤, 王智,陈立恒5无拖曳航天任务检验质量的设计和比较傅江良,甘庆波,张扬,赵柯昕,袁洪6用于引力波关键技术验证的近地低成本商业卫星设计陈琨,蔡志鸣,侍行剑,邓剑峰,余金培,李华旺7空间引力波探测中的绝对距离测量及通信技术刘河山,高瑞弘,罗子人,靳刚8空间引力波探测任务的入轨误差分析李卓,王有亮,郑建华,李明涛9无拖曳控制技术研究及在我国空间引力波探测中的应用邓剑峰,蔡志鸣,陈琨,侍行剑,余金培, 李华旺10星上剩磁对惯性传感器的影响柴国志,黄亮,乔亮,张冠茂11亚微牛级推力测量系统设计及实验研究杨超,贺建武,康琦,段俐论文下载链接：Home · Indico (ictp-ap.org)
AbstractWe investigate the stochastic gravitational wave background (SGWB) from cosmic domain walls (DWs) caused by quantum fluctuations of a light scalar field Φ during inflation. Large-scale perturbations of Φ lead to large-scale perturbations of DW energy density and anisotropies in the SGWB. We find that the angular power spectrum of this SGWB is scale invariant and at least of the order of 10−2, which is a distinctive feature of observational interest. Since we have not detected primordial gravitational waves yet, anisotropies of the SGWB provide a nontrivial opportunity to verify the rationality of inflation and detect the energy scale of inflation, especially for low-scale inflationary models. Square kilometer array has the opportunity to detect the anisotropies of such SGWBs. The common-spectrum process observed recently by NANOGrav could also be interpreted by the SGWB from cosmic DWs.DOI: 10.1103/PhysRevLett.126.141303 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.141303Phys. Rev. Lett. 126, 141303
AbstractThe Hubble parameter is one of the central parameters in modern cosmology, which describes the present expansion rate of the universe. Their values inferred from the late-time observations are systematically higher than those from the early-time measurements by about 10%. To come to a robust conclusion, independent probes with accuracy at percent levels are crucial. Gravitational waves from compact binary coalescence events can be formulated into the standard siren approach to provide an independent Hubble parameter measurement. The future space-borne gravitational wave observatory network, such as the LISA-Taiji network, will be able to measure the gravitational wave signals in the Millihertz bands with unprecedented accuracy. By including several statistical and instrumental noises, we show that within 5 years operation time, the LISA-Taiji network is able to constrain the Hubble parameter within 1% accuracy, and possibly beats the scatters down to 0.5% or even better.DOI: 10.1093/nsr/nwab054https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwab054/6207944National Science Review
AbstractIn this perspective, we outline that a space borne gravitational wave detector network combining LISA and Taiji can be used to measure the Hubble constant with an uncertainty less than 0.5% in ten years, compared with the network of the ground based gravitational wave detectors which can measure the Hubble constant within a 2% uncertainty in the next five years by the standard siren method. Taiji is a Chinese space borne gravitational wave detection mission planned for launch in the early 2030 s. The pilot satellite mission Taiji-1 has been launched in August 2019 to verify the feasibility of Taiji. The results of a few technologies tested on Taiji-1 are presented in this paper.DOI:10.1038/s42005-021-00529-zhttps://www.nature.com/articles/s42005-021-00529-zCommunications Physics 4, Article number: 34 (2021)
Abstract The recent RIKEN experiment on the quenched gA in the superallowed Gamow-Teller transition from 100Sn indicates the role of scale anomaly encoded in the anomalous dimension β’of the gluonic stress tensor Tr G2μν. This observation provides support to the notion of hidden scale symmetry emerging by strong nuclear correlations with an infrared (IR) fixed point realized—in the chiral limit—in the Nambu—Goldstone mode. We suggest there is an analogy in the way scale symmetry manifests in a nuclear medium to the continuity from the unitarity limit at low density (in light nuclei) to the dilaton limit at high density (in compact stars). In between the limits, say, at normal nuclear matter density, the symmetry is not visible, hence hidden.DOI: 10.1103/PhysRevLett.125.142501https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.142501Phys. Rev. Lett. 125, 142501 (2020)
AbstractWe present a general method for approximately contracting tensor networks with an arbitrary connectivity. This enables us to release the computational power of tensor networks to wide use in inference and learning problems defined on general graphs. We show applications of our algorithm in graphical models, specifically on estimating free energy of spin glasses defined on various of graphs, where our method largely outperforms existing algorithms, including the mean-field methods and the recently proposed neural-network-based methods. We further apply our method to the simulation of random quantum circuits and demonstrate that, with a trade-off of negligible truncation errors, our method is able to simulate large quantum circuits that are out of reach of the state-of-the-art simulation methods.DOI:10.1103/PhysRevLett.125.060503https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.060503Phys. Rev. Lett. 125, 060503
AbstractTaiji is a Chinese space mission to detect gravitational waves in the frequency band 0.1 mHz to 1.0 Hz, which aims at detecting super (intermediate) mass black hole mergers and extreme (intermediate) mass ratio in-spirals. A brief introduction of its mission overview, scientific objectives, and payload design is presented. A roadmap is also given in which the launching time is set to the 2030s.https://doi.org/10.1093/ptep/ptaa083Progress of Theoretical and Experimental Physics（2020）