Compatibility of Drinfeld presentations for split affine Kac-Moody quantum symmetric pairs

TL;DR

This paper establishes factorization and coproduct formulas for Drinfeld-Cartan operators in split affine quantum symmetric pairs of types B, C, D, extending previous results from type A, and shows compatibility of a boundary q-character map.

Contribution

It generalizes the Drinfeld presentation results from type A to types B, C, D for affine quantum symmetric pairs and introduces a compatible boundary q-character map.

Findings

Proved factorization formulas for Drinfeld-Cartan operators.

Established coproduct formulas for these operators.

Demonstrated compatibility of the boundary q-character map with the usual q-character map.

Abstract

Let $(\mathbf{U}, \mathbf{U}^\imath)$ be a split affine quantum symmetric pair of type $\mathsf{B}_n^{(1)}, \mathsf{C}_n^{(1)}$ or $\mathsf{D}_n^{(1)}$. We prove factorization and coproduct formulae for the Drinfeld-Cartan operators $\Theta_i(z)$ in the Lu-Wang Drinfeld-type presentation, generalizing the type $\mathsf{A}_n^{(1)}$ result from [Prz23]. As an application, we show that a boundary analogue of the $q$-character map, defined via the spectra of these operators, is compatible with the usual $q$-character map. As an auxiliary result, we also produce explicit reduced expressions for the fundamental weights in the extended affine Weyl groups of classical types.