A Comparison of cluster algebra structures arising from $i$-boxes and Demazure weaves

Abstract

We compare two cluster algebras related to a positive element $\mathtt{b}$ in the braid group of finite $ADE$ type. One is the localized bosonic extension ${\widetilde{\mathbb{A}}}_\mathbb{C}(\mathtt{b})$ equipped with an initial seed arising from an admissible chain $\mathfrak{C}$ of $i$-boxes, which is deeply connected to monoidal categorification. The other is the coordinate ring $\mathbb{C}[X({\underlineΔ} {\boldsymbol{i}})]$ of the braid variety $X({\underlineΔ} {\boldsymbol{i}})$ equipped with an initial seed arising from a Demazure weave $\mathfrak{W}$, where ${\boldsymbol{i}}$ and ${\underlineΔ}$ are expression sequences of $\mathtt{b}$ and the half twist $Δ$, respectively. We explicitly construct a Demazure weave $\mathfrak{W}_{\underlineΔ}(\mathfrak{C})$ for each admissible chain $\mathfrak{C}$ associated with ${\boldsymbol{i}}$, and prove that there exists an algebra isomorphism $φ_{\boldsymbol{i}}\colon {\widetilde{\mathbb{A}}}_\mathbb{C}(\mathtt{b})\to\mathfrak{C}[X({\underlineΔ} {\boldsymbol{i}})]$ which is compatible with the two seeds arising from $\mathfrak{C}$ and $\mathfrak{W}_{\underlineΔ}(\mathfrak{C})$. Moreover, the isomorphism $φ_{\boldsymbol{i}}$ sends the PBW vectors ${\overline{\mathsf{p}}}_{\boldsymbol{i},k} \in {\widetilde{\mathbb{A}}}_\mathbb{C}(\mathtt{b})$ to the coordinates $z_k \in \mathfrak{C}[X({\underlineΔ} {\boldsymbol{i}})]$ indexed by the letters of ${\boldsymbol{i}}$. As applications, we investigate a connection between Demazure weaves and signed words via the $i$-boxes and interpret the isomorphism $φ_{\boldsymbol{i}}$ from the viewpoint of monoidal categorification using Hernandez--Leclerc categories.