Probing the variation of fundamental constants using QSO absorption lines

Abstract

Absorption lines seen in the spectra of distant QSOs allow us to probe the space and time evolution of various fundamental constants. Here, we summarize results on the variation of α obtained by our group and others using UVES/VLT. Most upper limits reside in the range 0.5-1.5×10^-5 at the 3σ level over a redshift range of approximately 0:5 ≤ z ≤ 2:5. In addition, we also briefly report on preliminary results based on the analysis of 21-cm absorbers detected with Giant Meterwave Radio Telescope(GMRT) that lead to Δx=x = (0:0 ± 1:5) × 10^-6 at z=1.3. Discussions on future improvement are also presented.