设R1,R2,R’是3个有单位元的结合环,环R是环同态j1:R1→R’和j2:R2→R’的拉回环,首先引入了左R1-模复形范畴与左R2-模复形范畴的积范畴的一个子范畴C(J),利用拉回函子方法构造了一个加法函子P:C(J)→C(R-Mod),以及S:C(R-Mod)→C(J),证明了(S,P)是一对伴随对函子.其次,在此基础上,研究了相应的左导出范畴,也得到相应左导出范畴之间的伴随对函子.最后通过一个例子说明在同伦范畴上没有相应的伴随对函子.
Let R1 ,R2,R' be associative rings with identity, R be a pullback ring along with two homomorphisms of rings j1: R1→R' and j2: R2→R'. It introduces a subcategory C (J) of product category of the left R1-modules complex category and left RE-modules complex category, and then construct additive functors P: C(J)→C(R - Mod) ,S: C(R - Mod)→C(J), and show that (S, P) is a pair of adjoint functors in terms of the method of pullbacks. We also get the result on the corresponding left-derived categories. Finally it gives an example for illustrating that conclusion on the homotopy category is not hold.