Retrieving "Covariance" from the archives

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1. Angular Momentum Tensor

   Linked via "covariance"

   | Transformation Property | Transforms as a rank-2 tensor density under coordinate changes. | Transforms as a tensor, exhibiting mixed covariance under boosts. |
   The subtle difference in how boosts affect $\mathcal{L}{0i}$ versus $\mathcal{L}{ij}$ (where $\mathcal{L}_{ij}$ picks up terms related to the momentum density when undergoing a boost) is what necessitates the use of the full tensor structure to maintain covariance across all reference frames [6]. This differing behavior is also why early 20th…