Spectrum of radiation of a classical electron moving in the de Sitter   spacetime
  The radiation spectrum of a classical charged particle (electron) moving in the de Sitter universe, has been calculated. The de Sitter metric is taken in the quasi-Euclidean Robertson-Walker form. It is shown that in the de Sitter spacetime an electron radiates as if it moved in a constant and homogeneous electric field with the strength vector E collinear to the electron momentum P. 
L.I. Tsaregorodtsev and N.N. Medvedev