Secondly, we introduce the basic properties of tensor product, and the definitions of complex and Hochschild homology group, the definition of coalgebra and some examples. 其次介绍了张量积的基本性质,复形和Hochschild同调群的定义,余代数的定义并且举出一些余代数的例子。
Since Hochschild proposed the concept and theory of Hochschild homology group while researching the homology group of associative algebra in 1942, it is widely used in many branches of mathematics. 自从Hochschild在1942年研究结合代数的同调群时提出Hochschild同调群的概念和理论以来,它在数学的许多分支均有广泛应用。