N-channel parity-time symmetry

We calculated the eigenvalues for a general N-channel coupled system with parity-time symmetry due to equal loss/gain. We found that the eigenspectrum displays a mixing of parity-time symmetric and broken phases, with N-2 of the eigenvalues being parity-time broken whereas the remaining two being either parity-time symmetric or broken depending on the loss/gain and coupling parameters. Our results also show that mixing of parity-time symmetric and parity-time broken phases can only be obtained for at least four-channels if other degrees of freedom like polarization is not taken into account.