4 problems

Let $R\longrightarrow A$ be a homomorphism of associative rings. Proposition establishes five equivalent conditions: Becker-contraacyclicity for complexes of $R$-cotorsion left $A$…

Let $R$ be a ring, let $\mathcal D$ denote the class of all flat Mittag-Leffler $R$-modules, and let $\mathcal D^\perp$ be the class of modules right orthogonal to every module in…

Let $R$ be a commutative ring and let $S_1,\dots,S_m\subset R$ be a finite collection of multiplicative subsets. For $J\subset\{1,\dots,m\}$, let $S_J$ be the multiplicative subset…

Let $R$ be a commutative ring and $S\subset R$ be a multiplicative subset such that the projective dimension of the $R$-module $S^{-1}R$ does not exceed $1$. A flat $R$-module $F$…