一句话:证明所有有限 1-截断高阶归纳类型都可由群胚商构造,并在 Coq/UniMath 中形式化。
论文研究单价类型论中高阶归纳类型(HITs)的构造与语义。作者首先在内部定义 HIT 的签名,并为每个签名构造以 1-type 和以 groupoid 为对象的代数双范畴,进而证明相应的初始代数语义。随后,论文证明 groupoid quotient 在两个代数双范畴之间诱导一个双伴随,并在 groupoid 代数双范畴中构造双初始对象。由此推出:所有有限 1-截断 HITs 都可以从 groupoid quotient 构造出来。全部结果均在 Coq 的 UniMath 单价数学库中形式化。
In this paper, we show that all finitary 1-truncated higher inductive types (HITs) can be constructed from the groupoid quotient. We start by defining internally a notion of signatures for HITs, and for each signature, we construct a bicategory of algebras in 1-types and in groupoids. We continue by proving initial algebra semantics for our signatures. After that, we show that the groupoid quotient induces a biadjunction between the bicategories of algebras in 1-types and in groupoids. We finish by constructing a biinitial object in the bicategory of algebras in groupoids. From all this, we conclude that all finitary 1-truncated HITs can be constructed from the groupoid quotient. All the results are formalized over the UniMath library of univalent mathematics in Coq.