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Modules with semiregular endomorphism rings

Kunio Yamagata (2008)

Colloquium Mathematicae

We characterize the semiregularity of the endomorphism ring of a module with respect to the ideal of endomorphisms with large kernel, and show some new classes of modules with semiregular endomorphism rings.

Nil-clean and unit-regular elements in certain subrings of 𝕄 2 ( )

Yansheng Wu, Gaohua Tang, Guixin Deng, Yiqiang Zhou (2019)

Czechoslovak Mathematical Journal

An element in a ring is clean (or, unit-regular) if it is the sum (or, the product) of an idempotent and a unit, and is nil-clean if it is the sum of an idempotent and a nilpotent. Firstly, we show that Jacobson’s lemma does not hold for nil-clean elements in a ring, answering a question posed by Koşan, Wang and Zhou (2016). Secondly, we present new counter-examples to Diesl’s question whether a nil-clean element is clean in a ring. Lastly, we give new examples of unit-regular elements that are...

Non-linear maps preserving ideals on a parabolic subalgebra of a simple algebra

Deng Yin Wang, Haishan Pan, Xuansheng Wang (2010)

Czechoslovak Mathematical Journal

Let 𝒫 be an arbitrary parabolic subalgebra of a simple associative F -algebra. The ideals of 𝒫 are determined completely; Each ideal of 𝒫 is shown to be generated by one element; Every non-linear invertible map on 𝒫 that preserves ideals is described in an explicit formula.

Nonlinear maps preserving Lie products on triangular algebras

Weiyan Yu (2016)

Special Matrices

In this paper we prove that every bijection preserving Lie products from a triangular algebra onto a normal triangular algebra is additive modulo centre. As an application, we described the form of bijections preserving Lie products on nest algebras and block upper triangular matrix algebras.

Odd H-depth and H-separable extensions

Lars Kadison (2012)

Open Mathematics

Let C n(A,B) be the relative Hochschild bar resolution groups of a subring B ⊆ A. The subring pair has right depth 2n if C n+1(A,B) is isomorphic to a direct summand of a multiple of C n(A,B) as A-B-bimodules; depth 2n + 1 if the same condition holds only as B-B-bimodules. It is then natural to ask what is defined if this same condition should hold as A-A-bimodules, the so-called H-depth 2n − 1 condition. In particular, the H-depth 1 condition coincides with A being an H-separable extension of B....

On lifting of idempotents and semiregular endomorphism rings

Tsiu-Kwen Lee, Yiqiang Zhou (2011)

Colloquium Mathematicae

Starting with some observations on (strong) lifting of idempotents, we characterize a module whose endomorphism ring is semiregular with respect to the ideal of endomorphisms with small image. This is the dual of Yamagata's work [Colloq. Math. 113 (2008)] on a module whose endomorphism ring is semiregular with respect to the ideal of endomorphisms with large kernel.

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