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首页> 外文期刊>Bulletin des sciences mathematiques >The classification of homogeneous Einstein metrics on flag manifolds with b_2 (M) = 1
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The classification of homogeneous Einstein metrics on flag manifolds with b_2 (M) = 1

机译:b_2(M)= 1的旗流形上齐次爱因斯坦度量的分类

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摘要

Consider a compact connected simple Lie group G. We study homogeneous Einstein metrics for a class of compact homogeneous spaces, namely generalized flag manifolds G/H with second Betti number b_2(G/H) = 1. There are 8 infinite families G/H corresponding to a classical simple Lie group G and 25 exceptional flag manifolds, which all have some common geometric features; for example they admit a unique invariant complex structure which gives rise to unique invariant K?hler-Einstein metric. The most typical examples are the compact isotropy irreducible Hermitian symmetric spaces for which the Killing form is the unique homogeneous Einstein metric (which is K?hler). For non-isotropy irreducible spaces the classification of homogeneous Einstein metrics has been recently completed for 24 of the 26 cases. In this paper we construct the Einstein equation for the two unexamined cases, namely the flag manifolds E_8/U(1) × SU(4) × SU(5) and E_8/U(1) × SU(2) × SU(3) × SU(5). In order to determine explicitly the Ricci tensors of an E8-invariant metric we use a method based on the Riemannian submersions. For both spaces we classify all homogeneous Einstein metrics and thus we conclude that any flag manifold G/H with b_2 (M) = 1 admits a finite number of non-isometric non-K?hler invariant Einstein metrics. The precise number of these metrics is given in Table 1.
机译:考虑一个紧密连通的简单李群G。我们研究一类紧凑齐次空间的齐次爱因斯坦度量,即具有第二贝蒂数b_2(G / H)= 1的广义标志流形G / H。对应于经典的简单李群G和25个例外的旗形流形,它们都有一些共同的几何特征;例如,他们接受了唯一不变的复杂结构,从而产生了唯一不变的K?hler-Einstein度量。最典型的例子是紧致各向同性的不可约Hermitian对称空间,Killing形式是其唯一的齐次爱因斯坦度量(即K?hler)。对于非各向同性的不可约空间,最近已经完成了26种情况中的24种同质爱因斯坦度量的分类。在本文中,我们针对两种未经检验的情况构造了爱因斯坦方程,即标志流形E_8 / U(1)×SU(4)×SU(5)和E_8 / U(1)×SU(2)×SU(3 )×SU(5)。为了明确确定E8不变度量的Ricci张量,我们使用基于黎曼浸没的方法。对于这两个空间,我们对所有齐次的爱因斯坦度量进行分类,因此可以得出结论,任何带有b_2(M)= 1的标志流形G / H都可以接受有限数量的非等距非Khhler不变爱因斯坦度量。表1中给出了这些指标的准确数量。

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