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arXiv 1602.06753math.DGmath.AT
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$Γ$ -结构与对称空间

$Γ$-structures and symmetric spaces

Bernhard Hanke, Peter Quast

摘要:

$Γ$ -结构是闭定向流形上乘法的弱形式。Hopf证明了含有$Γ$ -结构的流形的有理上同调代数在奇数度生成元上是自由的。我们证明了这个条件也是同伦理论意义下幂零流形上存在$Γ$ -结构的充分条件。这包括具有连通各向同性群的齐性空间。传递到一个更几何的角度来看,我们表明,在紧凑的定向黎曼对称空间与连通各向同性群和自由有理上同调代数的典范乘积给出测地对称定义$Γ$ -结构。这扩展了Albers,Frauenfelder和Solomon关于$Γ$ -拉格朗日Grassmannian结构的工作。

英文摘要:

$Γ$-structures are weak forms of multiplications on closed oriented manifolds. As shown by Hopf the rational cohomology algebras of manifolds admitting $Γ$-structures are free over odd degree generators. We prove that this condition is also sufficient for the existence of $Γ$-structures on manifolds which are nilpotent in the sense of homotopy theory. This includes homogeneous spaces with connected isotropy groups. Passing to a more geometric perspective we show that on compact oriented Riemannian symmetric spaces with connected isotropy groups and free rational cohomology algebras the canonical products given by geodesic symmetries define $Γ$-structures. This extends work of Albers, Frauenfelder and Solomon on $Γ$-structures on Lagrangian Grassmannians.

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