Transformation Groups ( IF 0.7 ) Pub Date : 2021-05-01 , DOI: 10.1007/s00031-021-09653-0 LUCAS FRESSE , IVAN PENKOV
Let G be one of the ind-groups GL(∞), O(∞), Sp(∞), and let P1, ..., Pℓ be an arbitrary set of ℓ splitting parabolic subgroups of G. We determine all such sets with the property that G acts with finitely many orbits on the ind-variety X1 × × Xℓ where Xi = G/Pi. In the case of a finite-dimensional classical linear algebraic group G, the analogous problem has been solved in a sequence of papers of Littelmann, Magyar–Weyman–Zelevinsky and Matsuki. An essential difference from the finite-dimensional case is that already for ℓ = 2, the condition that G acts on X1 × X2 with finitely many orbits is a rather restrictive condition on the pair P1, P2. We describe this condition explicitly. Using the description we tackle the most interesting case where ℓ = 3, and present the answer in the form of a table. For ℓ ≥ 4 there always are infinitely many G-orbits on X1 × × Xℓ.
中文翻译:
带有有限轨道的多个标志变数
让摹是IND-群体之一GL(∞),O(∞),SP(∞),并且让P 1,...,P ℓ是ℓ分裂抛物线分组的任意一组摹。我们确定所有这样的设置与属性,ģ与对IND-品种有限多个轨道X作用1 ×× X ℓ其中X我= g ^ / P我。在有限维经典线性代数群G的情况下,类似的问题已在Littelmann,Magyar–Weyman–Zelevinsky和Matsuki的一系列论文中得到解决。与有限维情况的本质区别是,对于ℓ = 2,G在有限的轨道上作用于X 1 × X 2的条件是对P 1,P 2的限制性条件。我们明确描述这种情况。使用描述,我们解决了最有趣的情况,即ℓ = 3,并以表格的形式给出了答案。对于ℓ≥4,X 1 ××上总是有无限多的G轨道X ℓ。