A series of nonrepresentable relation algebras is constructed from groups. We use them to prove that there are continuum many subvarieties between the variety of representable relation algebras and the variety of coset relation algebras. We present our main construction in terms of polygroupoids.

中文翻译：

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来自组的不可表示的关系代数

一系列不可表示的关系代数是由群构成的。我们用它们来证明在可表示关系代数的多样性和陪集关系代数的多样性之间存在许多子变体。我们根据 polygroupoids 介绍我们的主要结构。