Rowmotion and Echelonmotion
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866913958893453312 |
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| author | Defant, Colin Jiang, Yuhan Marczinzik, Rene Segovia, Adrien Speyer, David E Thomas, Hugh Williams, Nathan |
| author_facet | Defant, Colin Jiang, Yuhan Marczinzik, Rene Segovia, Adrien Speyer, David E Thomas, Hugh Williams, Nathan |
| contents | Given a linear extension $σ$ of a finite poset $R$, we consider the permutation matrix indexing the Schubert cell containing the Cartan matrix of $R$ with respect to $σ$. This yields a bijection $\mathrm{Ech}_σ\colon R\to R$ that we call echelonmotion; it is the inverse of the Coxeter permutation studied by Klász, Marczinzik, and Thomas. Those authors proved that echelonmotion agrees with rowmotion when $R$ is a distributive lattice. We generalize this result to semidistributive lattices. In addition, we prove that every trim lattice has a linear extension with respect to which echelonmotion agrees with rowmotion. We also show that echelonmotion on an Eulerian poset (with respect to any linear extension) is an involution. Finally, we initiate the study of echelon-independent posets, which are posets for which echelonmotion is independent of the chosen linear extension. We prove that a lattice is echelon-independent if and only if it is semidistributive. Moreover, we show that echelon-independent connected posets are bounded and have semidistributive MacNeille completions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_18230 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Rowmotion and Echelonmotion Defant, Colin Jiang, Yuhan Marczinzik, Rene Segovia, Adrien Speyer, David E Thomas, Hugh Williams, Nathan Combinatorics 05E16, 05E18, 06A07, 06B10, 16E30 Given a linear extension $σ$ of a finite poset $R$, we consider the permutation matrix indexing the Schubert cell containing the Cartan matrix of $R$ with respect to $σ$. This yields a bijection $\mathrm{Ech}_σ\colon R\to R$ that we call echelonmotion; it is the inverse of the Coxeter permutation studied by Klász, Marczinzik, and Thomas. Those authors proved that echelonmotion agrees with rowmotion when $R$ is a distributive lattice. We generalize this result to semidistributive lattices. In addition, we prove that every trim lattice has a linear extension with respect to which echelonmotion agrees with rowmotion. We also show that echelonmotion on an Eulerian poset (with respect to any linear extension) is an involution. Finally, we initiate the study of echelon-independent posets, which are posets for which echelonmotion is independent of the chosen linear extension. We prove that a lattice is echelon-independent if and only if it is semidistributive. Moreover, we show that echelon-independent connected posets are bounded and have semidistributive MacNeille completions. |
| title | Rowmotion and Echelonmotion |
| topic | Combinatorics 05E16, 05E18, 06A07, 06B10, 16E30 |
| url | https://arxiv.org/abs/2507.18230 |