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arXiv math/0605656math.DGmath.GR
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具有极大Toledo不变量的曲面群表示

Surface group representations with maximal Toledo invariant

Marc Burger, Alessandra Iozzi, Anna Wienhard

摘要:

本文将有界紧致连通定向曲面的基本群的极大表示理论推广到厄米特型群。对于任何这样的表示,我们定义的托莱多不变,我们建立的属性,如一致有界的表示品种,可加性下连接和表面和同余关系。从而得到了极大表示即Toledo不变量达到最大值的表示的几何性质:证明了极大表示具有离散象,是忠实的,完全可约的,并且它们总是保持一个极大管型子域.这延伸到一般厄米特群的情况下,一些性质的陈述在Teichmuller空间,以及结果由于高盛,托莱多,埃尔南德斯,布拉德洛-加西亚-普拉达-Gothen。在无边界表面的情况下宣布这些结果-其中管型域的作用已经被强调-出现在2003年由相同的作者。Toledo不变量的同余关系涉及到一个与连续齐次拟同构相关的旋转数函数,它给出了计算Toledo不变量的一种显式方法。这个旋转数推广了Ghys、Barge-Ghys和Clerc-Koufany的构造。此外,我们建立属性的边界映射相关的最大表示,自然推广,希洛夫边界的因果结构,单调性性质的拟共轭的圆。这一点,连同同余关系导致的结果,子集的最大表示总是真正的半代数。

英文摘要:

We develop the theory of maximal representations of the fundamental group of a compact connected oriented surface with boundary, into a group of Hermitian type. For any such representation we define the Toledo invariant, for which we establish properties such as uniform boundedness on the representation variety, additivity under connected sum of surfaces and congruence relations. We thus obtain geometric properties of the maximalrepresentations, that is representations whose Toledo invariant achieves the maximum value: we show that maximal representations have discrete image, are faithful and completely reducible and they always preserve a maximal tube type subdomain. This extends to the case of a general Hermitian group some of the properties of the representations in Teichmuller space, as well as results due to Goldman, Toledo, Hernandez, Bradlow--Garcia-Prada--Gothen. An announcement of these results in the case of surfaces without boundary -- where the role of tube type domains had already been emphasized -- appeared in 2003 by the same authors. The congruence relations for the Toledo invariant involve a rotation number function related to a continuous homogeneous quasimorphism which gives an explicit way to compute the Toledo invariant. This rotation number generalizes constructions due to Ghys, Barge--Ghys, and Clerc--Koufany. We establish moreover properties of boundary maps associated to maximal representations which generalize naturally, for the causal structure of the Shilov boundary, monotonicity properties of quasiconjugations of the circle. This, together with the congruence relations leads to the result that the subset of maximal representations is always real semialgebraic.

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