タニグチ ケンジ   TANIGUCHI,Kenji
  谷口 健二
   所属   青山学院大学  理工学部 物理・数理学科
   職種   教授
言語種別 英語
発行・発表の年月 2014/03
形態種別 学術雑誌
査読 査読有り
標題 Closed orbits on partial flag varieties and double flag variety of finite type
執筆形態 共同
巻・号・頁 pp.113-119
著者・共著者 Kensuke Kondo, Kyo Nishiyama, Hiroyuki Ochiai
概要 Let G be a connected reductive algebraic group over C. We denote by K=(Gθ)0 the identity component of the fixed points of an involutive automorphism θ of G. The pair (G,K) is called a symmetric pair. Let Q be a parabolic subgroup of K. We want to find a pair of parabolic subgroups P1, P2 of G such that (i) P1 ∩ P2 = Q and (ii) P1 P2 is dense in G. The main result of this article states that, for a simple group G, we can find such a pair if and only if (G,K) is a Hermitian symmetric pair. The conditions (i) and (ii) imply that the K-orbit through the origin (eP1,eP2) of G/P1 × G/P2 is closed and it generates an open dense G-orbit on the product of partial flag variety. From this point of view, we also give a complete classification of closed orbits on G/P1 × G/P2.