The geometry of conjugation in affine Coxeter groups
Fuente:
arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866929686041329664 |
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| author | Milićević, Elizabeth Schwer, Petra Thomas, Anne |
| author_facet | Milićević, Elizabeth Schwer, Petra Thomas, Anne |
| contents | We develop new and precise geometric descriptions of the conjugacy class $[x]$ and coconjugation set $\operatorname{C}(x,x') = \{ y \in \overline{W} \mid yxy^{-1} = x' \}$ for all elements $x,x'$ of any affine Coxeter group $\overline{W}$. The centralizer of $x$ in $\overline{W}$ is the special case $\operatorname{C}(x,x)$. The key structure in our description of the conjugacy class $[x]$ is the mod-set ${Mod}_{\overline{W}}(w) = (w-\operatorname{I})R^\vee$, where~$w$ is the finite part of $x$ and $R^\vee$ is the coroot lattice. The coconjugation set $\operatorname{C}(x,x')$ is then described by ${Mod}_{\overline{W}}(w')$ together with the fix-set of $w'$, where $w'$ is the finite part of $x'$. For any element $w$ of the associated finite Weyl group $W$, the mod-set of $w$ is contained in the classical move-set ${Mov}(w) = \operatorname{Im}(w - \operatorname{I})$. We prove that the rank of ${Mod}_{\overline{W}}(w)$ equals the dimension of ${Mov}(w)$, and then further investigate type-by-type the surprisingly subtle structure of the $\mathbb{Z}$-module ${Mod}_\overline{W}(w)$. As corollaries, we determine exactly when ${Mod}_{\overline{W}}(w) = {Mov}(w) \cap R^\vee$, in which case our closed-form descriptions of conjugacy classes and coconjugation sets are as simple as possible. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_08080 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The geometry of conjugation in affine Coxeter groups Milićević, Elizabeth Schwer, Petra Thomas, Anne Group Theory Combinatorics Representation Theory We develop new and precise geometric descriptions of the conjugacy class $[x]$ and coconjugation set $\operatorname{C}(x,x') = \{ y \in \overline{W} \mid yxy^{-1} = x' \}$ for all elements $x,x'$ of any affine Coxeter group $\overline{W}$. The centralizer of $x$ in $\overline{W}$ is the special case $\operatorname{C}(x,x)$. The key structure in our description of the conjugacy class $[x]$ is the mod-set ${Mod}_{\overline{W}}(w) = (w-\operatorname{I})R^\vee$, where~$w$ is the finite part of $x$ and $R^\vee$ is the coroot lattice. The coconjugation set $\operatorname{C}(x,x')$ is then described by ${Mod}_{\overline{W}}(w')$ together with the fix-set of $w'$, where $w'$ is the finite part of $x'$. For any element $w$ of the associated finite Weyl group $W$, the mod-set of $w$ is contained in the classical move-set ${Mov}(w) = \operatorname{Im}(w - \operatorname{I})$. We prove that the rank of ${Mod}_{\overline{W}}(w)$ equals the dimension of ${Mov}(w)$, and then further investigate type-by-type the surprisingly subtle structure of the $\mathbb{Z}$-module ${Mod}_\overline{W}(w)$. As corollaries, we determine exactly when ${Mod}_{\overline{W}}(w) = {Mov}(w) \cap R^\vee$, in which case our closed-form descriptions of conjugacy classes and coconjugation sets are as simple as possible. |
| title | The geometry of conjugation in affine Coxeter groups |
| topic | Group Theory Combinatorics Representation Theory |
| url | https://arxiv.org/abs/2407.08080 |