The Tetrahedron algebra, the Onsager algebra, and the ${\mathfrak{sl}}_2$ loop algebra

Brian Hartwig, Paul Terwilliger

Let $K$ denote a field with characteristic 0 and let $T$ denote an indeterminate. We give a presentation for the three-point loop algebra $\mathfrak{sl}_2 \otimes K\lbrack T, T^{-1…