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arXiv math/0511608math.AGmath.CO
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旗空间上的拟阵与环面作用的几何不变理论

Matroids and Geometric Invariant Theory of torus actions on flag spaces

Benjamin J. Howard

摘要:

本文应用Gel'fand,Goresky,MacPherson和Serganova关于拟阵多面体的定理,研究了旗空间F = SL(n)/P中部分旗相对于T-线性化样本线丛的半稳定性,其中T是SL(n)中的极大环面,P是包含T的抛物子群.我们发现,只要存在至少一个非零的一次不变截面,无论是线丛还是线性化,半稳定点都可以由一次不变截面检测出来.在这种情况下,度1部分足以从G.I.T.给出一个定义良好的地图。商F//T到射影空间。此外,我们还证明了SL(n)/P中任意T-轨道的闭包对于SL(n)/P的任意射影嵌入都是射影正规环面簇.

英文摘要:

We apply a theorem of Gel'fand, Goresky, MacPherson, and Serganova about matroid polytopes to study semistability of partial flags relative to a T-linearized ample line bundle of a flag space F = SL(n)/P where T is a maximal torus in SL(n) and P is a parabolic subgroup containing T. We find that the semistable points are all detected by invariant sections of degree one regardless of the line bundle or linearization thereof, provided there exists at least one nonzero invariant section of degree one. In this case the degree one sections are sufficient to give a well defined map from the G.I.T. quotient F//T to projective space. Additionally, we show that the closure of any T-orbit in SL(n)/P is a projectively normal toric variety for any projective embedding of SL(n)/P.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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