New Constraints on Spatial Variations of the Fine Structure Constant   from Clusters of Galaxies
  We have constrained the spatial variation of the fine structure constant using multi-frequency measurements of the thermal Sunyaev-Zeldovich effect of 618 X-ray selected clusters. Although our results are not competitive with the ones from quasar absorption lines, we improved by a factor 10 and ~2.5 previous results from Cosmic Microwave Background power spectrum and from galaxy clusters, respectively. 
I. de Martino, C.J.A.P. Martins, H. Ebeling, D. Kocevski
astro-ph.CO