Abstract
An exchange ring R is strongly separative provided that for all finitely generated projective right R-modules A and B, A ⊕ A ≅ A ⊕ B ⇒ A ≅ B. We prove that an exchange ring R is strongly separative if and only if for any corner S of R, aS + bS = S implies that there exist u, v ∈ S such that au = bv and Su + Sv = S if and only if for any corner S of R, aS + bS = S implies that there exists a right invertible matrix \( \left( {\begin{array}{*{20}c} a & b \\ * & * \\ \end{array} } \right) \) ∈ M 2(S). The dual assertions are also proved.
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Chen, H. Strong separativity over exchange rings. Czech Math J 58, 417–428 (2008). https://doi.org/10.1007/s10587-008-0024-9
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DOI: https://doi.org/10.1007/s10587-008-0024-9