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[Achievements] The Department of Astronomy cosmic neutrino numerical simulation has made important progress

Published: 2017-06-07

 
The cosmic neutrino numerical simulation team led by Prof. Zhang Tongjie of Astronomy Department, using the "Tianhe No.2" supercomputer developed by National University of Defense Technology, successfully completed the numerical simulation of neutrino and dark matter of 3 trillion particles, revealing the universe Big bang 16 million years later so far about 13.7 billion years of long evolution process. In the simulation, for the first time the differential Neutrino Condensation effect of neutrinos in the cosmic structure was measured and it wasn’t in any previous cosmological numerical simulation. This effect opens up an independent measurement approach for today's and future cosmological observations. The micro-mass pathways are a big step forward on the cosmological limits of neutrino mass. The study was published on Nature Astronomy, 1, 0143 (2017) (arXiv: 1609.08968) on June 5, 2017 (see below link).
 
Neutrinos is one of the most basic species in nature, known as "the universe ghost". It is escaped about 1 second after the birth of the universe from the impact of other plasma substances, and form the invisible cosmic background. Neutrino shuttle back and forth in the space, is the participants and witnesses of the evolution of the universe and a variety of astronomical phenomena. Due to the low mass of neutrinos (about one millionth or less of the electron mass), no electricity, fast movement, the current physical experiments and cosmological observations can not determine the absolute quality of neutrinos. However, neutrinos have a weak but indispensable inhibitory effect on the formation of early galaxies and large-scale structures in the universe, which can be indirectly "measured" by large-scale cosmological numerical simulations to provide important information about neutrino mass information. This large-scale cosmological numerical simulation relies on supercomputers with powerful computing and storage capabilities. In the simulation, for the first time the differential Neutrino Condensation effect of neutrinos in the cosmic structure was measured and it wasn’t in any previous cosmological numerical simulation. The neutrino mass can be determined by comparing the different neutrino abundances in the universe (That is, the local neutrino and dark matter density ratio) in the region of the characteristics of the galaxy to measure. In contrast to the "lean" neutrino region, more neutrino particles are trapped by massive mass of dark matter in the "rich" neutrino region, which results in distortions in the mass function of the dark matter halo, leading to the occurrence of galaxies Variety. Thus this effect opens up an independent measurement approach of neutrino mass in today's and future cosmological observations.

  
By the end of 2013, the National Defense University of Science and Technology successfully developed the world's fastest "Tianhe II" computer and put into operation in the National University of Zhongshan National Super Guangzhou Center. Since then, by Beijing Normal University, Peking University, Canada Institute of Theoretical Astrophysics, Chinese Academy of Sciences Institute of High Energy Physics and National University of Defense Science and Technology, a combination of cosmic neutrino numerical simulation team, through a series of technical research, the 3 trillion particles in the neutrino and dark matter cosmological numerical simulation has been successfully completed on "Tianya II" before the Spring Festival in 2015. According to the chief scientist of the National Astronomical Observatory of the Chinese Academy of Sciences Chen Xuelei, this research project has more than tripled the number of 1.07 trillion particles in the Mira supercomputer of the American Argonne National Laboratory, created a new world record. Running up to 3 trillion particles in neutrino and dark matter cosmological numerical simulation, it is like a "pixel" extremely high "ultra-high speed camera", through the simulation "restore" out of the universe clear and long evolution "video ", so that makes the universe 16 million years after the explosion to so far about 13.7 billion years of long evolution process to" show ". It brings new opportunities and hope for measurement of the quality of neutrinos through the astronomical observation means. CCTV and many other media have had a lot of reports.

 
Chinese Academy of Sciences Institute of High Energy Physics, director of the Institute of Physics and the Chinese Academy of Sciences, Department of Modern Physics, Xing Zhizhong researcher believes that this is the field of international cosmology the largest number of running particles N numerical simulation. It opened up the new window of astronomical observation of the universe neutrino and its quality of mass. It is expected to greatly shorten the human exploration of the origin and evolution of the mystery of the time course of the basic science, the universe, the Earth's ecological, mineral exploration and other fields of scientific research and will play a positive role in promoting researches in these fields.
 
With the Chinese and Europe and the United States and Japan’s effort of further accurate determination on the various parameters of the neutrino, scientists are gradually revealed the neutrino "cosmic ghost" mystery. Professor Zhang Tongjie’s team is planning to use the " Tianhe II" supercomputer to run more than 3 trillion particles even larger-scale cosmic neutrino numerical simulation, and is expected to continue to lead in the international competition of cosmic neutrino mass research, and ultimately to achieve the newer and greater breakthroughs in the Neutrino mass and sequence studies. Thereby it will promote the further development of astronomy, astrophysics, cosmology, particle physics and related science fields.

 
The first author of the research results Yu Haoran is Ph.D. of the Astronomy Department, Beijing Normal University, the postdoctoral of Peking University and the postdoctoral of Canadian Institute of Theoretical Astrophysics; Professor Zhang Tongjie is the communication author.
 
[1] Article in Nature Home Links: https://www.nature.com/articles/s41550-017-0143
[2] Springer Nature Sharing (shared link): http://rdcu.be/tfyp
 
(Department of Astronomy, Beijing Normal University)


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