Unruh response functions for scalar fields in de Sitter space
  We calculate the response functions of a freely falling Unruh detector in de Sitter space coupled to scalar fields of different coupling to the curvature, including the minimally coupled massless case. Although the responses differ strongly in the infrared as a consequence of the amplification of superhorizon modes, the energy levels of the detector are thermally populated. 
Bjorn Garbrecht, Tomislav Prokopec (Heidelberg University)