广义拉回与推出

Generalized Pullbacks and Pushouts

利用逆向极限刻画集体拉回与I-拉回,探讨I-拉回与拉回间的关系;并把集体拉回和I-拉回统一起来,引入拉回的另一推广形式,即广义拉回,研究它在一般范畴及环、模范畴上的性质,应用到拉回环,得到拉回环上倾斜模间的关系及几类广义拉回环的同调维数的上界。

This paper characterizes collective pullbacks and I-pullbacks by means of inverse limit and discusses the relationship between I-pullbacks and pullbacks. Finally, introduces generalized pullbacks which generalize pullbacks, collective pullbacks and I-pullbacks, investigates their properties both in general category and some concrete categories, discusses the relationship between tilting modules over pullback rings, obtains the upper bounds for the homological dimension of some generalized pullback rings.