题 目：Searching for Chameleon-like Scalar Fields
报告人：Professor Sergei Levshakov
(Ioffe Physical-Technical Institute, St. Petersburg, Russia)
摘 要：Using the 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg telescopes we found a statistically significant velocity offset ΔV =27 ± 3 m/s (1δ) between the inversion transition in NH3(1,1) and low-J rotational transitions in N2H+(1-0) and HC3N(2-1) arising in cold and dense molecular cores in the Milky Way. Systematic shifts of the line centers caused by turbulent motions and velocity gradients, possible non-thermal hyperfine structure populations, pressure and optical depth effects are shown to be lower than or about 1 m/s and thus can be neglected in the total error budget. The reproducibility of ΔV at the same facility (Effelsberg telescope) on a year-to-year basis is found to be very good. Since the frequencies of the inversion and rotational transitions have different sensitivities to variations in the electron-to-proton mass ratio, μ = me/mp, the revealed non-zero ΔV may imply that μ changes when measured at high (terrestrial) and low (interstellar) matter densities as predicted by chameleon-like scalar field models - candidates to the dark energy carrier. Thus we are testing whether scalar field models have chameleon-type interactions with ordinary matter. The measured velocity offset corresponds to the ratio Δμ/μ= (μspace - μlab)/ μlab of (26 ± 3)×10-9 (1δ).
时 间：2010年12月22日（星期三）上午10:00
地 点：（北京西路2号）紫台大楼327教室
学术报告有关问题咨询：83332107
紫金山天文台学术委员会学术交流工作委员会
2010年12月17日
