We recall some unusual features of the cohomology of arithmetic groups, and propose that they are explained by a hidden action of certain motivic cohomology groups.

中文翻译：

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算术组和自守形式的周期的同调

我们回顾了算术组同调的一些不寻常的特征，并提出用某些动机同调组的隐藏动作来解释它们。