{"title":"Realizations of inner automorphisms of order four and fixed points subgroups by them on the connected compact exceptional Lie group $E_8$, Part II","authors":"Toshikazu Miyashita","doi":"10.21099/TKBJM/1571968818","DOIUrl":null,"url":null,"abstract":"The compact simply connected Riemannian 4-symmetric spaces were classified by J.A. Jim{e}nez according to type of the Lie algebras. As homogeneous manifolds, these spaces are of the form $G/H$, where $G$ is a connected compact simple Lie group with an automorphism $\\tilde{\\gamma}$ of order four on $G$ and $H$ is a fixed points subgroup $G^\\gamma$ of $G$. According to the classification by J.A. Jim{e}nez, there exist seven compact simply connected Riemannian 4-symmetric spaces $ G/H $ in the case where $ G $ is of type $ E_8 $. In the present article, %as Part II continuing from Part I, for the connected compact %exceptional Lie group $E_8$, we give the explicit form of automorphisms $\\tilde{w}_{{}_4} \\tilde{\\upsilon}_{{}_4}$ and $\\tilde{\\mu}_{{}_4}$ of order four on $E_8$ induced by the $C$-linear transformations $w_{{}_4}, \\upsilon_{{}_4}$ and $\\mu_{{}_4}$ of the 248-dimensional vector space ${\\mathfrak{e}_8}^{C}$, respectively. Further, we determine the structure of these fixed points subgroups $(E_8)^{w_{{}_4}}, (E_8)^{{}_{\\upsilon_{{}_4}}}$ and $(E_8)^{{} _{\\mu_{{}_4}}}$ of $ E_8 $. These amount to the global realizations of three spaces among seven Riemannian 4-symmetric spaces $ G/H $ above corresponding to the Lie algebras $ \\mathfrak{h}=i\\bm{R} \\oplus \\mathfrak{su}(8), i\\bm{R} \\oplus \\mathfrak{e}_7$ and $\\mathfrak{h}= \\mathfrak{su}(2) \\oplus \\mathfrak{su}(8)$, where $ \\mathfrak{h}={\\rm Lie}(H) $.","PeriodicalId":44321,"journal":{"name":"Tsukuba Journal of Mathematics","volume":null,"pages":null},"PeriodicalIF":0.3000,"publicationDate":"2017-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Tsukuba Journal of Mathematics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.21099/TKBJM/1571968818","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
The compact simply connected Riemannian 4-symmetric spaces were classified by J.A. Jim{e}nez according to type of the Lie algebras. As homogeneous manifolds, these spaces are of the form $G/H$, where $G$ is a connected compact simple Lie group with an automorphism $\tilde{\gamma}$ of order four on $G$ and $H$ is a fixed points subgroup $G^\gamma$ of $G$. According to the classification by J.A. Jim{e}nez, there exist seven compact simply connected Riemannian 4-symmetric spaces $ G/H $ in the case where $ G $ is of type $ E_8 $. In the present article, %as Part II continuing from Part I, for the connected compact %exceptional Lie group $E_8$, we give the explicit form of automorphisms $\tilde{w}_{{}_4} \tilde{\upsilon}_{{}_4}$ and $\tilde{\mu}_{{}_4}$ of order four on $E_8$ induced by the $C$-linear transformations $w_{{}_4}, \upsilon_{{}_4}$ and $\mu_{{}_4}$ of the 248-dimensional vector space ${\mathfrak{e}_8}^{C}$, respectively. Further, we determine the structure of these fixed points subgroups $(E_8)^{w_{{}_4}}, (E_8)^{{}_{\upsilon_{{}_4}}}$ and $(E_8)^{{} _{\mu_{{}_4}}}$ of $ E_8 $. These amount to the global realizations of three spaces among seven Riemannian 4-symmetric spaces $ G/H $ above corresponding to the Lie algebras $ \mathfrak{h}=i\bm{R} \oplus \mathfrak{su}(8), i\bm{R} \oplus \mathfrak{e}_7$ and $\mathfrak{h}= \mathfrak{su}(2) \oplus \mathfrak{su}(8)$, where $ \mathfrak{h}={\rm Lie}(H) $.