Cambrian triangulations and their tropical realizations
Résumé
This paper develops a Cambrian extension of the work of C. Ceballos, A. Padrol and C. Sarmiento on $\nu$-Tamari lattices and their tropical realizations.
For any signature $\varepsilon \in \{\pm\}^n$, we consider a family of $\varepsilon$-trees in bijection with the triangulations of the $\varepsilon$-polygon. These $\varepsilon$-trees define a flag regular triangulation $\mathcal{T}^{\varepsilon}$ of the subpolytope ${\mathrm{conv} \{(\mathbf{e}_{i_\bullet}, \mathbf{e}_{j_\circ}) \; | \; 0 \le i_\bullet < j_\circ \le n+1\}}$ of the product of simplices $\triangle_{\{0_\bullet, \dots, n_\bullet\}} \times \triangle_{\{1_\circ, \dots, (n+1)_\circ\}}$. The oriented dual graph of the triangulation $\mathcal{T}^{\varepsilon}$ is the Hasse diagram of the (type $A$) $\varepsilon$-Cambrian lattice of N. Reading. For any $I_\bullet \subseteq \{0_\bullet, \dots, n_\bullet\}$ and $J_\circ \subseteq \{1_\circ, \dots, (n+1)_\circ\}$, we consider the restriction $\mathcal{T}^{\varepsilon}_{I_\bullet, J_\circ}$ of the triangulation $\mathcal{T}^{\varepsilon}$ to the face $\triangle_{I_\bullet} \times \triangle_{J_\circ}$. Its dual graph is naturally interpreted as the increasing flip graph on certain $(\varepsilon, I_\bullet, J_\circ)$-trees, which is shown to be a lattice generalizing in particular the $\nu$-Tamari lattices in the Cambrian setting. Finally, we present an alternative geometric realization of $\mathcal{T}^{\varepsilon}_{I_\bullet, J_\circ}$ as a polyhedral complex induced by a tropical hyperplane arrangement.
Domaines
Combinatoire [math.CO]
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Pilaud_CambrianTriangulationsTropicalRealizations_EJC.pdf (616 Ko)
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