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Probing Primordial Chirality with Galaxy Spins

April 06, 2020      Author: Yu Haoran

On 10th March, a research paper titled "Probing Primordial Chirality with Galaxy Spins" was published in Physical Review Letters. 【Yu, Hao-Ran et al. Physical Review Letters, 124,101302 (2020)】

Chiral symmetry is maximally violated in weak interactions, and such microscopic asymmetries in the early Universe might leave observable imprints on astrophysical scales without violating the cosmological principle. In this Letter, we propose a helicity measurement to detect primordial chiral violation. We point out that observations of halo-galaxy angular momentum directions (spins), which are frozen in during the galaxy formation process, provide a fossil chiral observable. From the clustering mode of large scale structure of the Universe, we construct a spin mode in Lagrangian space and show in simulations that it is a good probe of halo-galaxy spins. In the standard model, a strong symmetric correlation between the left and right helical components of this spin mode and galaxy spins is expected. Measurements of these correlations will be sensitive to chiral breaking, providing a direct test of chiral symmetry breaking in the early Universe.

Yu Hao-Ran, the first and corresponding author of this paper, was a postdoctoral research fellow of TDLI from July 2017 to November 2019. During this period, he led three scientific research projects such as " Nonlinear Neutrino Clustering and Large Scale Structure of the Universe", which were supported by the Postdoctoral Science Fund and youth research fund of NSFC. After his postdoctoral work, Yu joined Xiamen University as an Associate Professor of the Department of Astronomy, a special researcher supported by the Nanqiang youth top talents program.

In addition, several scientists participated in this research, including Ue-Li Pen, Professor of Canada Institute for Theoretical Astrophysics and Distinguished Visiting Fellow of TDLI, Yu Yu, special associate researcher of School of Physics and Astronomy, SJTU, Yang Xiaohu, Professor of School of Physics and Astronomy, SJTU and Associate Fellow of TDLI, Jing Yipeng, Professor of School of Physics and Astronomy, SJTU and TDLI Chair Professor, etc.


Link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.101302