@preprint{halla2024,
  title={A new numerical method for scalar eigenvalue problems in heterogeneous, dispersive, sign-changing materials},
  author={Halla, Martin and Hohage, Thorsten and Oberender, Florian},
  journal={arXiv preprint arXiv:2401.16368},
  url={https://arxiv.org/pdf/2401.16368},
  year={2024}
}


@preprint{halla2025,
  title={On the instabilities of naive FEM discretizations for PDEs with sign-changing coefficients},
  author={Halla, Martin and Oberender, Florian},
  journal={arXiv preprint arXiv:2504.07712},
  url={https://arxiv.org/pdf/2504.07712},
  year={2025}
}