  Non-Hermitian topological band structures such as symmetry-protected
exceptional rings (SPERs) can emerge for systems described by the generalized
eigenvalue problem (GEVP) with Hermitian matrices. In this paper, we
numerically analyze a photonic crystal with negative index media, which is
described by the GEVP with Hermitian matrices. Our analysis using COMSOL
Multiphysics demonstrates that a SPER emerges for photonic crystals composed of
split-ring resonators and metal-wire structures. We expect that the above SPER
can be observed in experiments as it emerges at a finite frequency.
