An Exact Solution to the Quantized Electromagnetic Field in   D-dimensional de Sitter Spacetimes
  In this work we investigate the quantum theory of light propagating in $D-$dimensional de Sitter spacetimes. To do so, we use the method of dynamic invariants to obtain the solution of the time-dependent Schr\"odinger equation. The quantum behavior of the electromagnetic field in this background is analyzed. As the electromagnetism loses its conformality in $D\neq4$, we point that there will be particle production and comoving objects will feel a Bunch-Davies thermal bath. This may become important in extra dimension physics and raises the intriguing possibility that precise measurements of the Cosmic Microwave Background could verify the existence of extra dimensions. 
G. Alencar, I. Guedes, R. R. Landim and R. N. Costa Filho
hep-th hep-ph