Colour-independent partition functions in coloured vertex models

This n-independence explains, in vertex-model terms, results from recent studies of S2 (Caetano and Vieira, 2012, [1], Wheeler, arXiv:1204.2089, [2]). Namely, 1. S2, which depends on two sets of Bethe roots, {b1} and {b2}, and cannot (as far as we know) be expressed in single determinant form, degenerates in the limit {b1}→∞, and/or {b2}→∞, into a product of determinants, 2. Each of the latter determinants is an A1 vertex-model partition function.