We prove that the plane Cremona group over a perfect field with at least one Galois extension of degree 8 is a non-trivial amalgam, and that it admits a surjective morphism to a free product of groups of order two.

中文翻译：

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非闭域上来自克雷莫纳群的特征态射

我们证明在具有至少一个 8 次伽罗瓦扩展的完美域上的平面克雷莫纳群是一个非平凡的汞齐，并且它允许对二阶群的自由乘积的满射态射。