关于G-Matlis自反模的换环定理

设Ｒ和Ｔ是Ｎｏｅｔｈｅｒ完备半局部环，Ｒ→Ｔ是环同态．本文证明了，若Ｔ是有限生成或ＡｒｔｉｎＲ－模，Ｍ为Ｇ－Ｍａｔｌｉｓ自反Ｒ－模，则对所有ｎ≥０，Ｅｘｔ^Ｒ_ｎ（Ｔ，Ｍ），Ｅｘｔ^Ｒ_ｎ（Ｍ，Ｔ），Ｔｏｒ^Ｒ_ｎ（Ｔ，Ｍ）以及Ｔｏｒ^Ｒ_ｎ（Ｍ，Ｔ）均是Ｇ－Ｍａｔｌｉｓ自反Ｔ－模．所得结果推广了Ｒ．Ｂｅｌｓｈｏｆ的结果．     

半值环的两个交换结果

定理１设Ｒ是半值环，ｎ为固定的正整数，如果Ｒ满足条件：存在依赖于(?)_ｘ，ｙ的两个字ｋ（Ｘ，Ｙ），ｔ（Ｘ，Ｙ），其中｜ｋ｜_X＞１，｜ｔ｜_X＝１，｜ｋ｜_Y≥｜ｔ｜_Y，｜ｔ｜_Y≤ｎ，使ｋ（ｘ，ｙ）－ｔ（ｘ，ｙ）∈Ｉ（Ｒ），则Ｒ是交换环。定理２设Ｒ是半值环，如果Ｒ满足条件：存在正整数ｍ＝ｍ（ｘ，ｙ）＞１，ｎ＝ｎ（ｙ），使得（ｘ^ｎｙ）^m－ｘ     

素GPI-环的幂零多项式

Ｒ是素ＧＰＩ－环,若多项式ｆ（ｘ_１,…,ｘ_d）在Ｒ上是幂零的,则或ｆ（ｘ_１…,ｘ_d）是Ｒ的恒 等式,或Ｒ是有限域上的有限矩阵环     

模自同态环的理想格与正规根

设_RＰ是环Ｒ上的左模．记P^*= Hom _R(P , R ) , J = P P^*, S₀= P^*P．本文讨论了Ｊ与Ｓ的双零化理想格之间的关系，以及Ｒ，Ｊ，Ｓ₀和Ｅｎｄ_RＰ的正规根之间的关系．     

G－半局部环及其同调维数

本文中讨论了一类比半局部环更广的环类，即Ｇ－半局部我们通过模去环的左Ｓｏｃｌｅ及Ｊａｃｏｂｓｏｎ根，研究了环的同调维数，并得到Ｇｄ（Ｒ／Ｓ）＝Ｇｄ（Ｒ／Ｓ∩Ｊ），式中的Ｇｄ表示环Ｒ的左整体维数或右整体维数，Ｓ＝Ｓｏｃ（_ＲＲ）以及Ｊ是环Ｒ的Ｊａｃｏｂｓｏｎ根。当Ｒ还是半本原环时，即得Ｇｄ（Ｒ／Ｓ）＝Ｇｄ（Ｒ）。     

投影下的Gronwall不等式

本文对Ｊ．Ｋ．Ｈａｌｅ曾提出的一类广泛的投影下的Ｇｒｏｎｗａｌ不等式问题作了讨论，对满足ｕ（ｔ）≤ａ（ｔ）＋∫_０^tｂ（ｔ－ｓ）ｕ（ｓ）ｄｓ＋∫_０^∞ｃ（ｓ）ｕ（ｔ＋ｓ）ｄｓ，(?)ｔ≥０的函数ｕ（ｔ）∈Ｃ_b⁰（Ｒ₊，Ｒ₊）作了估计．其结果对讨论微分方程的有界解、不变流形及其Ｆｏｌｉａｔｉｏｎ和进一步讨论奇性Ｇｒｏｎｗａｌ不等式都有意义     

关于分次环的分次性质和非分次性质

本文证明了对有限群分次环Ｒ而言,下列条件等价：（１）Ｒ是左ｇｒ－自内射环（左ｇｒ－ＰＦ环,左ｇｒ－ＱＦ环,左ｇｒ－线性紧环）．（２）Ｒ是左自内射环（左ＰＦ环,左ＱＦ环,左线性紧环）．（３）Ｒ＃Ｇ^*是左自内射环（左ＰＦ环,左ＱＦ环,左线性紧环）．     

关于Buchsbaum环的注记

本文证明了下述结论，设Ａ是一个级数为ｄ的Ｂｕｃｈｓｂａｕｍ环，（ａ₁，ａ₂，…，ａ_n）是Ａ的一个参数系统，则任何正整数ｎ，Ａ／（ａ₁，ａ₂，…，ａ_k）ⁿ（１≤ｋ≤ｄ）仍是ｄ－ｋ维的Ｂｕｃｈｓｂａｕｍ环．     

G—半局部环及其同调维数

本文中讨论了一类比半局部环更广的环类，即Ｇ－半局部环，对Ｇ－半局部我们通过模去环的左Ｓｏｃｈｅ及Ｊａｃｏｂｓｏｎ根，研究了环的同调维数，并得到Ｇｄ（Ｒ／Ｓ）＝Ｇｄ（Ｒ／Ｓ∩Ｊ），式中的Ｇｄ表示环Ｒ的左整体维数或右整体维数，Ｓ＝Ｓｏｃ（Ｒ＾Ｒ）以及Ｊ是环Ｒ的Ｊａｃｏｂｓｏｎ根，当Ｒ还时半本原环时，即得Ｇｄ（Ｒ／Ｓ）＝Ｇｄ（Ｒ）。     

泛剩余交

本文建立了泛剩余交理论，并揭示了它与剩余交和一般剩余交的关系，得到：在交换局部环Ｒ的扩张Ｓ＝Ｒ（Ｘ）＝Ｒ［Ｘ］_{mＲ［Ｘ］}中，存在ＩＳ的一个ｓ－剩余交ＵＲＩ（ｓ；Ｉ），使得对Ｉ在Ｒ中的任意ｓ－剩余交Ｊ，ＵＲＩ（ｓ；Ｉ）是Ｊ的本质形变，且是Ｉ的一般ｓ－剩余交ＲＩ（ｓ；Ｉ）局部化ＲＩ（ｓ；Ｉ）_{mＲ［Ｘ］}．并给出了一些应用，为研究剩余交和一般剩余交提供了工具．     

Regular Action in Rings

Let R be a ring with identity, X(R) the set of all nonzero non-units of R and G(R) the group of all units of R. By considering left and right regular actions of G(R) on X(R), the following are investigated: (1) For a local ring R such that X(R) is a union of n distinct orbits under the left (or right) regular action of G(R) on X(R), if J ⁿ  ≠ 0 = J ⁿ⁺¹ where J is the Jacobson radical of R, then the set of all the distinct ideals of R is exactly {R, J, J ²,…, J ⁿ , 0}, and each orbit under the left regular action is equal to the one under the right regular action. (2) Such a ring R is left (and right) duo ring. (3) For the full matrix ring S of n × n matrices over a commutative ring R, the number of orbits under left regular action of G(S) on X(S) is equal to the number of orbits under right regular action of G(S) on X(S); the result also holds for the ring of n × n upper triangular matrices over R.     

Spectra of Maximal 1-Sided Ideals and Primitive Ideals

R is any ring with identity. Let Spec _r (R) (resp. Max _r (R), Prim _r (R)) denote the set of all right prime ideals (resp. all maximal right ideals, all right primitive ideals) of R and let U _r (eR) = {P ? Spec _r (R)| e ? P}. Let  = ∪_{P?Prim r (R)} Spec _r ^P (R), where Spec _r ^P (R) = {Q ?Spec _r ^P (R)|P is the largest ideal contained in Q}. A ring is called right quasi-duo if every maximal right ideal is 2-sided. In this article, we study the properties of the weak Zariski topology on  and the relationships among various ring-theoretic properties and topological conditions on it. Then the following results are obtained for any ring R: (1) R is right quasi-duo ring if and only if  is a space with Zariski topology if and only if, for any Q ? , Q is irreducible as a right ideal in R. (2) For any clopen (i.e., closed and open) set U in ? = Max _r (R) ∪  Prim _r (R) (resp.  = Prim _r (R)) there is an element e in R with e ² ? e ? J(R) such that U = U _r (eR) ∩  ? (resp. U = U _r (eR) ∩  ), where J(R) is the Jacobson of R. (3) Max _r (R) ∪  Prim _r (R) is connected if and only if Max _l (R) ∪  Prim _l (R) is connected if and only if Prim _r (R) is connected.     

几乎优越扩张与同调维数

设环S是环R的几乎优越扩张．本文证明了R和S具有相同的f．f．P．维数以及finitistic维数．若M_S是右S－模,则FP－id（M_S）＝FP－id（M_R）．若G是有限群,R是G分次环且|G|^－1∈R,则Smash积R＃G^*和R具有相同的f．f．P．维数,finitistic维数,以及FP－整体维数．     

Commuting Values of Generalized Derivations on Multilinear Polynomials

Let K be a commutative ring with unity, R a prime K-algebra of characteristic different from 2, U the right Utumi quotient ring of R, f(x ₁,…, x _n ) a noncentral multilinear polynomial over K, and G a nonzero generalized derivation of R. Denote f(R) the set of all evaluations of the polynomial f(x ₁,…, x _n ) in R. If [G(u)u, G(v)v] = 0, for any u, v ∈ f(R), we prove that there exists c ∈ U such that G(x) = cx, for all x ∈ R and one of the following holds: 1. f(x ₁,…, x _n )² is central valued on R;

2. R satisfies s ₄, the standard identity of degree 4.

     

Topological rings,homogeneous functions,and primeness

For any group G such that G is a right R-module for some ring R, the elements of R act on G as endomorphisms and we obtain the near-ring of R-homogeneous maps on G: M_R(G) = {f: G → G|f(ga) = f(g)a for all a ∈ R, g ∈ G}. In the special case that R is a topological ring and G is a topological R-module, we study N_R(G): = {f ∈ M_R(G)|f is continuous}. In particular, we investigate primeness of the near-ring N_R(G) of continuous homogeneous maps on G.     

Gelfand Factor Rings and Weak Zariski Topologies

Let R be any ring with identity. Let N(R) (resp. J(R)) denote the prime radical (resp. Jacobson radical) of R, and let Spec _r (R) (resp. Spec _l (R), Max _r (R), Prim _r (R)) denote the set of all right prime ideals (resp. all left prime ideals, all maximal right ideals, all right primitive ideals) of R. In this article, we study the relationships among various ring-theoretic properties and topological conditions on Spec _r (R) (with weak Zariski topology). The following results are obtained: (1) R/N(R) is a Gelfand ring if and only if Spec _r (R) is a normal space if and only if Spec _l (R) is a normal space; (2) R/J(R) is a Gelfand ring if and only if every right prime ideal containing J(R) is contained in a unique maximal right ideal.     

Artinian Rings Characterized by Direct Sums of CS Modules

Abstract

In this note, we show that the following are equivalent for a ring R for which the socle or the injective hull of R _R is finitely generated: (i) The direct sum of any two CS right R-modules is again CS; (ii) R is right Artinian and every uniform right R-module has composition length at most two. Next we give partial answers to a question of Huynh whether a right countably Σ-CS ring which either is semilocal or has finite Goldie dimension is right Σ-CS. We give characterizations, in terms of radicals, of when such rings are right Σ-CS. In particular, for the semilocal case, Huynh's question is reduced to whether rad(Z ₂(R _R )) is Σ-CS or Noetherian, where Z ₂(R _R ) is the second singular right ideal of R. Our results yield new characterizations of QF-rings.     

Two applications of maschke's theorem

Let R ? G denote a crossed product of the finite group G over the ring R and let V be an R ? G-module. Maschke's theorem states that if 1/∣G∣ ε R and if V is completely reducible as an R-module, then V is also completely reducible as an R ? G -module. In this paper, we obtain two applications of this theorem, both under the assumption that R is semiprime with no ∣G∣ -torsion. The first concerns group actions and here we show that if G acts on R and if I is an essential right ideal of the fixed ring R^G , then IR is essential in Rs. This result, in turn, simplifies a number of proofs already in the literature. The second application here is a short proof of a theorem of Fisher and Montgomery which asserts that the crossed product R ? G is semiprime.     

Functors of the category of abelian sheaves on regular affine scheme

In this short paper, we prove that ifR is a regular local ring of unequal characteristic, then there exists an additive covariant functorG from the category of abelian sheaves on SpecR to the category of abelian groups such that id _R (G(R))>dimG(R). This result shows that the answer to the question 3.8 (ii) in [3] may be negative.     

A note on utumi quotient rings

Let R be a ring and ρ a right ideal of R with zero right annihilate. Then ρ and R have the same left Utumi quotient ring. We study the lifting properties of GPIs and some chain conditions inherited by such right ideals. Next, we prove a generalization of Chatters’ theorem. Precisely, we show that if R is a right nonsingular ring with finite right Goldie dimension and possesses a right ideal ρ such that both ρ and l _R(ρ) are PI-rings, then the right Utumi quotient ring of R is also a Pi-ring.