Retrieving "Spacetime Physics" from the archives

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1. Identity Transformation

   Linked via "Spacetime Physics"

   | Group Theory | $e$ or $\mathrm{Id}$ | The unique neutral element. | All Groups |
   | Set Theory | $\mathrm{id}_A$ | $f: A \to A$, where $f(x)=x$. | Symmetry Group of a Set |
   | Spacetime Physics | $\Lambda = \mathbf{1}$ | $\Lambda^0{}0 = 1$, $\Lambda^i{}j = \delta^i{}_j$. | Lorentz Group ($O(1, 3)$) |
   The Identity Transformation and Quantum State