Retrieving "Isotropic Vacuum State" from the archives

Cross-reference notes under review

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

1. Vacuum Viscosity

   Linked via "isotropic vacuum state"

   In its most general form, vacuum viscosity is not a scalar but a rank-four tensor, $\eta_{V, ijkl}$, reflecting the anisotropy introduced by large-scale cosmological structures or extreme curvature (e.g., near a black hole singularity).
   For the isotropic vacuum state assumed in the Standard Model vacuum ($\Lambda\text{CDM}$), the tensor reduces to a single scalar $\eta_V$. Ho…