Noetherian Centralizing Hopf Algebra Extensions and Finite Morphisms of Quantum Groups

On Continuous and Adjoint Morphisms Between Noncommutative Prime Spectra

We study topological properties of the correspondence of prime spectra associated to a noncommutative ring homomorphism R -> S. Our main result provides criteria for the adjointness of certain functors between the categories of Zariski closed subsets of Spec(R) and Spec(S); these functors arise naturally from restriction and extension of scalars. When R and S are left noetherian, adjointness occurs only for centralizing and ``nearly centralizing'' homomorphisms.

Non-Noetherian representation categories of generalized fields

In this paper, we show that the categories of finitely generated projective $\mathbb{B}$-modules and $\mathbb{F}_\infty$-modules with morphisms being (splittable) injections are not locally Noetherian. This provides another instance of the fact that these generalized fields have strange homological behavior.

Fully bounded noetherian rings and Frobenius extensions

Let $i: A\to R$ be a ring morphism, and $χ: R\to A$ a right $R$-linear map with $χ(χ(r)s)=χ(rs)$ and $χ(1_R)=1_A$. If $R$ is a Frobenius $A$-ring, then we can define a trace map $\tr: A\to A^R$. If there exists an element of trace 1 in $A$, then $A$ is right FBN if and only if $A^R$ is right FBN and $A$ is right noetherian. The result can be generalized to the case where $R$ is an $I$-Frobenius $A$-ring, and the condition on the trace can be replaced by a weaker condition. We recover results of Garc\'ıa and del R\'ıo and by Dǎscǎlescu, Kelarev and Torrecillas on actions of group and Hopf algeb…

诺特代数上内射包络与平坦覆盖的对偶性

Duality Between Injective Envelopes and Flat Covers over Noether Algebras

本文将交换诺特环上内射包络与平坦覆盖的对偶关系推广到非交换诺特代数领域，拓展了相关同调代数结论的适用范围。

Behaviour of injective dimension with respect to regradings

Given a left noetherian k-algebra A graded by a group G, an injective object I in the category of G-graded A-modules and a morphism from G to another group G', we provide bounds for the injective dimension of I as a G'-graded A-module. For this, we use three change of grading functors. Most of the constructions concerning these functors work in the context of H-comodule algebras, where H is a Hopf algebra, so we develop them in this general context.

Graded Coherence of Certain Extensions of Graded Algebras

Let $\k$ be a field, and let $A$ and $B$ be connected $\N$-graded $\k$-algebras. The algebra $A$ is said to be a graded right-free extension of $B$ provided there is a surjective graded algebra morphism $π: A \to B$ such that $\kerπ$ is free as a right $A$-module. Suppose that $B$ is graded left coherent, and that $A$ is a graded right-free extension of $B$. We characterize when $A$ is also graded left coherent. We apply our criterion to prove graded coherence of certain non-Noetherian graded twisted tensor products.