Searching for Chameleon-Like Scalar Fields

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~(-1) (1σ) between the inversion transition in NH_3(1,1) and low- J rotational transitions in N_2H~+(1-0) and HC_3N(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 1m s~(-1) and thus can be neglected in the total error budget. The reproducibility of A V 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 μ = m_e/m_p, 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 = (μ_(space) — μ_(lab))/μ_(lab) of(26±3)×10~(-9)(1σ).