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(Dec. 21) Can ΛCDM model reproduce MOND-like behavior?

Last updated :2017-12-20

Topic: Can ΛCDM model reproduce MOND-like behavior?
Speaker: Dr. Dechang Dai
(Shanghai Jiao Tong University)
Invited by: Prof. LIN Weipeng
Time: 15:00-16:00, Thursday, December 21, 2017
Venue: Room 107, Red House 17, Zhuhai Campus, SYSU

Abstract:
It is usually believed that MOND can describe the galactic rotational curves with only baryonic matter and without any dark matter very well, while the ΛCDM model is expected to have difficulty in reproducing MOND-like behavior. Here, we use EAGLE’s data to learn whether the ΛCDM model can reproduce MOND-like behavior. EAGLE’s simulation result clearly reproduces the MOND-like behavior for a b≳〖10〗^(-12) m/s^2b at z =0, although the acceleration constant, a0 , is a little larger than the observational data indicate. We find that a0 increases with the redshift in a way different from what Milgrom proposed (a0 ∝ H). Therefore, while galaxy rotation curves can be fitted by MOND’s empirical function in the ΛCDM model, there is no clear connection between a0 and the Hubble constant. We also find that a0 at z ≳ 1 is well separated from a0 at z = 0. Once we have enough galaxies observed at high redshifts, we will be able to rule out the modified gravity model based on MOND-like empirical function with a z-independent a0 .

Speaker's CV:
Dr. Dai received his Ph.D. in Cosmology and Particle Physics in 2008 from Case Western Reserve University. He had a post doc position at SUNY Buffalo for two years and then moved to University Cape Town as a post doc for the other two years. He joined Shanghai Jiao Tong University as a Distinguished Research Fellow in 2012. His Ph.D. study is focusing on the modified gravity theories and mini-black hole. Apart from pure theoretical study, he also did some data analysis. Recently he studied the galaxy rotation curves from EAGLE’s simulation suite and found that general belief that CDM cannot produce MOND behavior and a modified gravity model is needed might not be correct.