Non Parallels Electric and Magnetic Fields in a F.R.W. Cosmology.   Classical and Quantum Gravitational Implications
  At first, we discuss parallels electric and magnetic fields solutions in a gravitational background. Then, considering eletromagnetic and gravitational waves symmetries we show a particular solution for stationary gravitational waves. Finally we consider gravitation as a gauge theory (effective gravitational theory), evaluate the propagators of the model, analyze the corresponding quantum excitations and verify (confirm) the tree-level unitarity at many places of the model. 
Carlos Pinheiro (UFES, Brazil), J.A. Helayel-Neto (CBPF & UCP,   Brazil), Gilmar S. Dias (UFES, Brazil)