-density, -adic completion and -subgeneration
Let Λ be a directed finite-dimensional algebra over a field k, and let B be an upper triangular bimodule over Λ. Then we show that the category of B-matrices mat B admits a projective generator P whose endomorphism algebra End P is quasi-hereditary. If A denotes the opposite algebra of End P, then the functor Hom(P,-) induces an equivalence between mat B and the category ℱ(Δ) of Δ-filtered A-modules. Moreover, any quasi-hereditary algebra whose category of Δ-filtered modules is equivalent to mat...
A ring has right SIP (SSP) if the intersection (sum) of two direct summands of is also a direct summand. We show that the right SIP (SSP) is the Morita invariant property. We also prove that the trivial extension of by has SIP if and only if has SIP and for every idempotent in . Moreover, we give necessary and sufficient conditions for the generalized upper triangular matrix rings to have SIP.
Let be a ring. We recall that is called a near pseudo-valuation ring if every minimal prime ideal of is strongly prime. Let now be an automorphism of and a -derivation of . Then is said to be an almost -divided ring if every minimal prime ideal of is -divided. Let be a Noetherian ring which is also an algebra over ( is the field of rational numbers). Let be an automorphism of such that is a -ring and a -derivation of such that for all . Further, if for any...
For every module we have a natural monomorphism and we focus our attention on the case when is also an epimorphism. Some other colimits are also considered.
For every module M we have a natural monomorphism and we focus attention on the case when Φ is also an epimorphism. The corresponding modules M depend on thickness of the cardinal number card(I). Some other limits are also considered.