Convergence of fermionic field entanglement at infinite acceleration in   relativistic quantum information
  We provide a simple argument showing that, in the limit of infinite acceleration, the entanglement in a fermionic field bipartite system must be independent of the choice of Unruh modes. This implies that most tensor product structures used previously to compute field entanglement in relativistic quantum information cannot give rise to physical results. 
M. Montero and E. Martin-Martinez
quant-ph gr-qc