Generalized Minkowski Theorem for Tetrahedra in ${\rm dS}^3$ and ${\rm AdS}^3$

Abstract

We formulate and prove a constant-curvature, holonomy-valued Lorentzian analogue of Minkowski theorem for generalized tetrahedra in the constant-curvature Lorentzian spaces ${\rm dS}^3$ and ${\rm AdS}^3$. Four non-trivial based ${\rm SO}^+(1,2)$ holonomies, or equivalently ${\rm SL}(2,\mathbb{R})$ spin lifts, determine intrinsic face normals, a dihedral Gram matrix $G$, and oriented triple products of intrinsic face normals. Under closure, nondegeneracy, and the outward convex branch condition, these data reconstruct a unique strictly convex tetrahedron up to ambient isometry. The sign of $\det G$ selects the de Sitter or anti-de Sitter model, and the prescribed holonomies are exactly the based Levi-Civita face holonomies of the reconstructed tetrahedron. The extrinsic face normals also define a polar-dual projective tetrahedron. In particular, the all-null AdS sector gives ideal dual tetrahedra, and the all-timelike AdS sector gives hyperideal dual tetrahedra. In the all-spacelike sector, changing to ${\rm SU}(2)$ real form recovers the reconstruction theorem for Euclidean spherical and hyperbolic tetrahedra.