Regular genus formula for the n-dimensional torus

Let nn be an integer with n5n\geq 5, and let Γ\Gamma^\prime be the (n+1)(n+1)-regular colored graph constructed from the colored triangulation described in the paper. It has (n+1)!(n+1)! vertices and represents the nn-dimensional torus S1×S1××S1\mathbb{S}^1 \times \mathbb{S}^1 \times \cdots \times \mathbb{S}^1 (nn times). The regular genus conjecture. The graph Γ\Gamma^\prime is a genus-minimal crystallization of the nn-dimensional torus, and its regular genus is

1+(n+1)!(n3)8.1+\frac{(n+1)!(n-3)}{8}.

The construction gives the asserted value for the displayed examples with n4n\leq 4, while genus-minimality for all n5n\geq 5 remains conjectural.

Sources & referencesView supporting material

Primary source

Anshu Agarwal and Biplab Basak, “Regular genus of S^2 S^1 S^1, 4-torus, and small covers over Δ^2 Δ^2”, arXiv:2506.01315 (2025).

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