On July 3，2023 the closing ceremony of the 2023 ICTP-AP Summer School was held successfully on Zhongguancun Campus of the University of Chinese Academy of Sciences(UCAS), marking the end of this year’s summer school.On the closing ceremony, faculty including professor representatives, administrative staff and postdoc representative all showed up, with a student representative pre-recorded video being shown on the stage. At the very beginning of the ceremony, Dr. Min Zhang showed a video that recorded students’ activities over the past three days, from the opening ceremony on the evening of June 30 to the last day’s visit on Yanqi Campus. On the first two days, students enjoyed an academic feast characterized by 10 lectures given by professors of UCAS, including a CAS academician, Professor Yue-Liang Wu, who is also the director of the ICTP-AP. Lecture given by CAS academician Yue-Liang Wu via videoThese two days also witnessed heated discussions between teachers and students, which inspired the students and provided a valuable experience for them to talk to the distinguished professors and peers from across the country face to face. At the end of the video was their last day’s visits to places including the Museum of Chinese Academy of Sciences and Two Bombs and One Satellite, the history Museum of UCAS on Yanqi Lake Campus of UCAS, which helps the students better understand the “huge campus” atmosphere and the history and development of UCAS. Students at the Museum of CAS and Two Bombs and One SatelliteStudents at the History Museum of UCASAfter a brief break on the campus, students then visited the National Space Science Center (NSSC) and went to the lab of the Institute of Mechanics,CAS. This special experience allowed Students to learn more about our country’s rapid development in space science and knew more about the significance of gravitational wave exploration. Students going into the Lab of the Institute of Mechanics, CASAfter watching the video, Professor Jun Zhang, as the professor representative of ICTP-AP, delivered a brief speech to the students and extended warm thanks to all the participants and organizers of this event. And then, Yuxin Liu, a doctoral student of ICTP-AP who is currently exchanging abroad, shared his experience about the advantages of studying in UCAS and how grateful he is as a student of ICTP-AP. He also encouraged the fellow students to work hard and pursue their dream in scientific studies and research.To help the students to learn more about Taiji Space Program, the post-doctoral He Wang also gave a brief introduction of his scientific work at ICTP-AP. After Dr. Wang’s speech comes the most unique and interesting part of the ceremony. Students who have been divided into four groups on the opening ceremony gave vivid and elaborate preseantations on their topics. Professors present said that the students have done a great job, and they also commented on their reports and shared their own insights respectively, which helped students to learn the strengths and shortcomings of their own work. Professor Tian commented that this is the most special and unique closing ceremony of summer school that he has ever been to, which is a huge encouragement to all the participants of this event. Closing CeremonyAfter the professors’ hard-hitting and professional comments, two groups won the prizes, which are the cultural and creative souvenirs of ICTP-AP, for their excellent group performance. Dr Min said that this is to encourage students to work hard and value the spirits of team work. Then comes to the most exciting part that the students are waiting for, that is to reveal the final 19 Students of Excellence.With the end of the closing ceremony, this year’s ICTP-AP summer school also came to a period, yet this special memory during the past four days will be carried by every participant. It provided students from universities across the country with a great opportunity to know about each other, talk with each other and most importantly, to have academic exchanges with the professors in the field of the advanced scientific research and to experience the study and life at ICTP-AP, UCAS in an immersive way.
The opening ceremony of the 2023 ICTP-AP Summer School hosted by the International Centre of Theoretical Physics-Asia Pacific (ICTP-AP) of the University of Chinese Academy of Sciences (UCAS) and the Taiji Laboratory for Gravitational Wave Universe has been held successfully on June 30th on Zhongguancun Campus, with students coming from 21 different universities across the country. At the beginning of the ceremony, Ms Meng Fanzi, the media and public relations secretary of the ICTP-AP office has given a brief welcome to all the students participating in the event. After that, Dr. Ming Zhang, the director of the ICTP-AP Office, on behalf of the ICTP-AP faculty, has given a warm welcome to all the students and delivered a speech on the history and development of the ICTP-AP as well as its training characteristics. He also mentioned about the distinguished professors of the center and introduced the administrative staff to the students. At the end of his speech, Dr. Zhang wished everyone a great experience during their stay here. After Dr. Zhang’s detailed and vivid description, all the students knew more about the center and raised many questions about UCAS and the centre. After the introduction by the faculty of ICTP-AP, students started to introduce themselves about where do they come from, what they like and what are their research interest. Some students also expressed their wish to become a member of the ICTP-AP in the future. After their various and funny self-introductions, faculty of the ICTP-AP Office handed out to the students a blind box, from which the students could find their small group as well as the topic for group discussion for the next few days. Through this way, the students felt more connected to each other and became closer with one another. After drawing the group names from the box, students found their own groups and gathered together and started a heated discussion with their group members. As time goes by, the opening ceremony ended in joyous and cheerful atmosphere and everyone is looking forward to the coming academic and people-to-people exchange in the coming days.
The Dragon Boat Festival, also known as Duanwu Festival, is celebrated on the fifth day of the fifth month of the Chinese lunar calendar, which falls on June 22 this year. On June 17th, the International Centre for Theoretical Physics Asia-Pacific co-hosted with the International College of UCAS and other departments to celebrate this traditional Chinese Festival, with 17 dragon boat teams composed of both Chinese and international students participating in the activity actively.Sign up areaInternational Students dressed in traditional Chinese clothes Before the race began, there are warm-up games including pitch-pot, shooting the five poisons, catching rice-dumplings as well as award-winning quiz about Duanwu Festival. Students and faculty from the ICTP-AP also took part in the games and had a lot of fun there. When the event’s atmosphere climbed as high as the temperature, Professor Zhongbo Hu, on behalf of Yueliang Wu, the director of the ICTP-AP, delivered an opening speech for the dragon boat race. After that, Professor Yueliang Wu and Zhongbo Hu inaugurated the dragon boat race together. Professor Yueliang Wu painted the eye to enliven the dragonProfessor Zhongbo Hu painted the eye to enliven the dragon Professor Yue-Liang Wu announced the official beginning of the boat raceStudents and faculty from the ICTP-AP formed a team boat named “ The Ripple of Space-Time” . After the coach’s patient training, the race got started. And every racer is sparing no efforts in paddling. After the race, the coach said that dragon boat racing is highly dependent on teamwork – every racer has to coordinate with each other in paddle frequency, speed as well as distance and a racer from the team said that he is looking forward to taking part in next year’s race and bringing the prize for the team. This International Dragon Boat Race, held as part of the Dragon Boat Festival Carnival provided a great opportunity for students from home and abroad to experience the profoundness and vitality of Chinese civilization. Aside from the thrilling competition, what’s more worth remembering is the common memory of team spirits and cultural exchanges among the participants.Students from ICTP-AP and the International College of UCAS
The Asia-Pacific School and Workshop on Gravitation and Cosmology (APSW-GC) has been held in the “Eco·Economy” Senior Talent Hub by the side of beautiful Qiandao Lake in Chun’an County, Hangzhou from May 14 to May 22, 2023. This 9-day long school is organized by the International Center for Theoretical Physics (ICTP-AP) and co-hosted by the Asia-Pacific Center for Theoretical Physics (APCTP), Hangzhou Institute for Advanced Study of UCAS, Institute of Theoretical Physics of CAS, National Astronomical Observatories, CAS and Zhejiang University of Technology.What’s worth mentioning is that there were over ten invited foreign physicists coming from afar and giving lectures on gravity cosmology, including gravitational wave and basic physics, black hole physics, dark matter and dark energy, inflation and cosmology. This event also provided a platform for the experts and scholars from China and overseas to exchange their academic ideas with each other so as to promote the academic cooperation among scientists and the training of graduate and doctoral students in the Asia-Pacific Region in the field of gravitation and cosmology. The APSW-GC 2023 was held in the “Eco·Economy” Senior Talent Hub by the side of beautiful Qiandao Lake and participants all enjoyed the pleasant environment and cultural atmosphere of the place. Professor Robert Mann from University of Waterloo in Canada and Professor Sang Pyo Kim from Kunsan Naional University in South Korea who came to the Chun’an county for the first time, said that “we didn’t feel any foreignness here, yet we felt comfortable and relaxed, just like at home. We could breathe the wild nature and it’s really suitable for academic research here”. It is believed that this school and workshop will continue to strengthen the cooperation and exchange between the ICTP-AP and distinguished universities across the world and expand its international influence.
The International Year of Basic Sciences for Sustainable Development (IYBSSD) is a key moment of mobilization to convince every citizen of the importance of taking into account and mastering basic sciences to ensure a balanced, sustainable and inclusive development of the planet.The sub-forum of the Forum on Frontiers of Quanta to Cosmos Physics has been successfully held in Hunan University in the city of Changsha, Hunan Province on April 16th, 2023. This forum is hosted by the International Center for Theoretical Physics-Asia Pacific (ICTP-AP) of UCAS, the Institute of Theoretical Physics (ITP) of CAS, Hangzhou Institute for Advanced Study of UCAS, and organized by Hunan University. This sub forum focused on the theme of "Particle Physics and Origin of Matter" and there are five scientists who brought us excellent repots on the theme, attracting over 320,000 audience watching online and offline.Speakers from left to the right: Geng Chaoqiang, Yu Hongwei, Wang Qing, Li Haibo, Tang YongYueliang Wu, the vice president of academic affairs from UCAS and the director of ICTP-AP stated that breakthroughs in the field of physics have inspired a series of major technology revolutions. For example, the introduction of Newtonian mechanics promoted the leap from the age of handicrafts industry to the age of steam and breakthroughs in basic science in the 19th century, such as the laws of electromagnetic induction promoted the second industrial revolution marked by the invention of electric power technology and the internal combustion engine, marking that mankind has entered the age of electricity. In the mid-20th century, the revolution in the field of physics with quantum mechanics and relativity as its core promoted major breakthroughs in atomic energy, computer science, bioengineering and space technology, marking that human society has entered the age of information. And Professor Wu pointed out that in the 21st century, we are faced with a new round of science and technological wave, students present at the forum are “in the flower of their age, and their spirit bright was as its height”. At last, he expressed his wish that the young talents could make their own contribution for the breakthroughs in the filed of basic science in the future and bring our society up to a higher ladder of development. Wu Yueliang Liu Wen, president of the office of Scientific R&D, extended warm welcome to all the teachers and students at the forum. He said that as a new round of technological revolution and industrial transformation is vigorously emerging, scientific exploration, innovation and cross disciplinary development are all in acceleration. Hunan University, as a university of thousand years of history, has earnestly implemented the innovation-driven development strategy, aiming towards the cutting-edge technology in the world to enhance its basic research and promote original creativity. He hoped that this forum could provide an opportunity for audience from online and offline to learn about the mysterious nature of quanta to cosmos physics and significance of exploring the basic laws of nature science. Liu WenWhat’s worth mentioning is that there are also over 60 high school students taking part in this forum actively and during the Q&A session, they raised many questions about science, asking about how to choose their major when they go to college as well as career development. Professors were very glad to share their own experience with the students and encouraged them to devote themselves into scientific research and pursue their science dreams in the vast land of our nation with the aim of solving major scientific problems.
The sub-forum of the Forum on Frontiers of Quanta to Cosmos Physics has been successfully held in Shandong University (Qingdao Campus) from March 4th to March 5th in 2023. This forum is hosted by the International Center for Theoretical Physics-Asia Pacific (ICTP-AP) of UCAS, the Institute of Theoretical Physics (ITP) of CAS, Hangzhou Institute for Advanced Study of UCAS, and organized by Shandong University. This sub forum focused on the theme of "Gravitational Wave and Precision Measurement Physics" and "Dark Universe and Black Hole Physics", and it has been broadcasted live on several online platforms, with over 400,000 audience watching online.Han Jianxin, the executive vice president of Shangdong University stated that quanta to cosmos physics is of great significance in promoting the development of physics and he hopes that this forum will provide an opportunity for experts and scholars to exchange academic views and seek cooperation with each other.Yueliang Wu, the vice president of academic affairs from UCAS said that currently, China has attached great importance to the development of basic science and CAS is the sole organization that acts as the Advisory Committee and Steering Committee for the International Year of Basic Sciences (IYBSS) in China, and therefore CAS values it a lot and has given strong support to it. Theoretical physics can be considered as the basic of basic sciences and its development has driven a series of scientific revolutions and promoted the progress of our society.The first lecturer Yueliang Wu has talked about the Taiji Program in Space, a space gravitational wave detection plan of our nation, and discussed the major scientific breakthroughs that could be brought by relative research.Reviewing the history and exploring unknowns, the 12 invited scientists has brought us a feast of cutting-edge physics from quanta to cosmos and jointly discussed about the important role of basic sciences for sustainable development.In the era of rapid development of physics, we are looking forward to more young talents joining the scientific research of cutting-edge physics in the future, exploring uninhabited areas, exploring unknown theories, solving science and technology difficulties, and contributing their wisdom and strength to the development of science.
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
由联合国教科文组织国际理论物理中心（亚太地区）和引力波宇宙太极实验室联合主办的中国科学院大学国际理论物理中心（亚太地区）2022年优秀大学生夏令营及引力波暑期学校于2022年7月4-8日成功举办。在过去一周的时间里，共有11位专家老师围绕引力、黑洞与量子宇宙、引力波探测与精密测量技术展开二十场讲座，与来自全国三十余家高校及科研院所的同学相聚“云端”，共话基础物理的奥秘，体悟科学的乐趣。暑期学校部分师生“云合影” 本次引力波暑期学校共有15位学员经专家考核脱颖而出，授予中国科学院大学国际理论物理中心（亚太地区）2022年优秀大学生夏令营“优秀学员”称号，名单公布如下（按姓氏排序）： 此次活动为年轻学子提供了一个接触国际学科前沿的平台，将吸引更多的有志青年投身到引力波探测相关研究中。期待他们未来能够成为空间引力波探测“太极计划”的一员，为中国空间引力波探测做出卓越贡献。
The five-day long summer school jointly held by International Centre for Theoretical Physics Asia-Pacific (ICTP-AP) and Taiji Laboratory for Gravitational Wave Universe was successfully concluded on 8th July, 2022. During the week, students from over 30 universities and science institutes gathered virtually to explore the myth of basic physics and enjoy the beauty of science, with 20 lectures centered on gravity, black hole and quanta to cosmos, gravitational wave detection and accurate measurement given by eleven experts and professors. Group photo of the students and staffThis virtual summer school has provided an important platform for the young talents to reach the frontiers of international disciplines so as to attract more youth to devote themselves to the research field of gravitational wave detection, become a member of the Taiji Program in Space and make their own contribution to Chinese space gravitational wave detection mission in the future.
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