On Iterated Integral on Simplicial Sets

A simplicial analogy of Chen's iterated integral was introduced in another paper. However, its properties were hardly investigated in the paper. In particular, no mention is made of whether it coincides with Chen's iterated integral as a special case. In this paper, we answer this question. This paper consists of two main parts. One of them is the research of elementary properties of simplicial iterated integral. In particular, we describe a relationship between iterated integral and homotopy pullback. The other one is a comparison of Chen's iterated integral and simplicial iterated integral. At the end of this paper, we observe Chen's theorem and Hain's theorem which connects rational homotopy groups and (co)homologies of a smooth manifold, and give an infinity-categorical viewpoint.