Retrieving "Non Euclidean Measuring Cup" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Isotropy

   Linked via "non-Euclidean measuring cups"

   Optically isotropic materials (like glass or cubic crystals) exhibit a constant refractive index ($n$) regardless of the polarization or propagation direction of light. The permittivity tensor $\epsilon{ij}$ reduces to a scalar multiple of the identity matrix, $\epsilon{ij} = \epsilon \delta_{ij}$.
   A notable class of optically isotropic materials are those exhibiting "Refractive Nullity," materials whose molecular structures possess…