The Tetrahedral (or $6j$) Symbol

Fuente: arXiv
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Main Authors: Venkatesh, Akshay, Wang, X. Griffin
Format: Preprint
Published: 2026
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author Venkatesh, Akshay
Wang, X. Griffin
author_facet Venkatesh, Akshay
Wang, X. Griffin
contents We will attach a scalar invariant to a tetrahedron whose edges are labelled by irreducible representations of a ternary orthogonal group $\mathrm{SO}_3$ over a local field. This generalizes the $6j$ symbol whose theory was developed by Racah, Wigner, and Regge. We give several formulas for this invariant, including in terms of hypergeometric-type integrals and functions, and show that it admits a symmetry by the the $23040$-element Weyl group of $\mathrm{Spin}_{12}$. We then interpret these results in terms of relative Langlands duality, where the dual story comes from the action of $\mathrm{Spin}_{12}$ on a $16$-dimensional cone of spinors.
format Preprint
id arxiv_https___arxiv_org_abs_2602_14908
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Tetrahedral (or $6j$) Symbol
Venkatesh, Akshay
Wang, X. Griffin
Number Theory
Representation Theory
We will attach a scalar invariant to a tetrahedron whose edges are labelled by irreducible representations of a ternary orthogonal group $\mathrm{SO}_3$ over a local field. This generalizes the $6j$ symbol whose theory was developed by Racah, Wigner, and Regge. We give several formulas for this invariant, including in terms of hypergeometric-type integrals and functions, and show that it admits a symmetry by the the $23040$-element Weyl group of $\mathrm{Spin}_{12}$. We then interpret these results in terms of relative Langlands duality, where the dual story comes from the action of $\mathrm{Spin}_{12}$ on a $16$-dimensional cone of spinors.
title The Tetrahedral (or $6j$) Symbol
topic Number Theory
Representation Theory
url https://arxiv.org/abs/2602.14908