On cluster structures of bosonic extensions

Abstract

We study quantum cluster structures on bosonic extensions of quantum unipotent coordinate rings. For a positive braid group element $b\in \operatorname{Br}^+$, Kashiwara--Kim--Oh--Park introduced a subalgebra $\widehat{\mathcal A}(b)$ and conjectured that it admits a quantum cluster algebra structure whose cluster monomials belong to the global basis. In this paper, we analyze Lusztig parametrizations of the global basis of $\widehat{\mathcal A}(b)$ and study their transition maps under braid moves. We prove that the resulting quantum cluster structure is independent of the chosen expression of $b$. Combining these ingredients, we prove the Kashiwara--Kim--Oh--Park conjecture for every \(b\in\operatorname{Br}^+\) in type ADE. Our proof is based on the compatibility between Lusztig parametrizations, braid moves, and cluster mutations, and is different from the approaches of Qin and of Kashiwara--Kim--Oh--Park. We also establish quantum \(T\)-system relations for generalized quantum minors and show that these minors occur as cluster variables.