Gorenstein flatness and injectivity over Gorenstein rings

Let R be a Gorenstein ring.We prove that if I is an ideal of R such that R/I is a semi-simple ring,then the Gorenstein flat dimension of R/I as a right R-module and the Gorenstein injective dimension of R/I as a left R-module are identical.In addition,we prove that if R→S is a homomorphism of rings and SE is an injective cogenerator for the category of left S-modules,then the Gorenstein flat dimension of S as a right R-module and the Gorenstein injective dimension of E as a left R-module are identical.We also give some applications of these results.     

V-Gorenstein Injective Modules Preenvelopes and Related Dimension

Let R and S be associative rings and _SV_R a semidualizing(S-R)-bimodule. An R-module N is said to be V-Gorenstein injective if there exists a Hom_R(I_V(R),-) and Hom_R(-, I_V(R)) exact exact complex ···→ I_1 d_0→I_0→I~0 d_0→I~1→··· of V-injective modules I_i and I~i, i ∈ N_0, such that N≌Im(I_0→I~0). We will call N to be strongly V-Gorenstein injective in case that all modules and homomorphisms in the above exact complex are equal, respectively. It is proved that the class of V-Gorenstein injective modules are closed under extension, direct summand and is a subset of the Auslander class A_V(R) which leads to the fact that V-Gorenstein injective modules admit exact right I_V(R)-resolution. By using these facts, and thinking of the fact that the class of strongly V-Gorenstein injective modules is not closed under direct summand, it is proved that an R-module N is strongly VGorenstein injective if and only if N⊕E is strongly V-Gorenstein injective for some V-injective module E. Finally, it is proved that an R-module N of finite V-Gorenstein injective injective dimension admits V-Gorenstein injective preenvelope which leads to the fact that, for a natural integer n, Gorenstein V-injective injective dimension of N is bounded to n if and only if Ext_(IV(R))~(≥n+1)(I, N) = 0 for all modules I with finite I_V(R)-injective dimension.     

Lie Homomorphism on the Associative Ring

Is it true tliat Lie homomorpHisin (isomorphism) \phi of a ring R into a ring R' is a homomorphism (isomorpliism) ? Herstein,I. N. and Kleinfeld, E. and Martindal, W. S.. obtained some results for simple ring and primitive ring,. In this paper I shall study the Lie homomorphism on the associative ring and arrive at the following main conclusion: Theorem. Suppose that R,R' are both associative rings with 1,and the center ofR’ does not contain zero divisor, where R’ is not of oharaoteristio 2 or 3. If \phi is a 3-Lie homomorphism of R onto R',then \phi must be either a homoinorpiiisin or the negative of an anti-homomorphism of R onto R'. Theorem. Suppose that R is an associatiye ring and $R'\ne {0}$ is a prime ring,where (R', +) does not contain elements of the period 2 or 3. If \phi is a 3-Lie homomorphism of R onto R',then \phi it either a homomorphism or the negative of an antihomomorpliism of R onto R'. Theorem. Suppose that R is an associative ring and (R, +) does not contain element of the period 2 or 3,R' is a prime ring. If \phi is a 3-Lie isomorpJlism of R onto R'。then \phi is either a isomorphism or the negative of an anti-isomorphism of R onto R'.     

On Injective Simple Modules Over a Noetherian Commutative Ring

It is proved in[1]that an injective simple module over a noetherian commu-tative ring must be projective.Because every noetherian ring R is a finite directsum of indecomposable rings,say R=R_1(?)…(?)R_n,every simple R-module Smustbe a simple R_i-module for some i and every R-homomorphismσ:M→S must sa-tisfyσ(R_jM)=0(j≠i).Thus it is easy to know theorem2 in[1]is equivalentto the following statement which can be proved much easier.     

Global dimension and left derived functors of Hom

It is well known that the right global dimension of a ring R is usually computed by the right derived functors of Hom and the left projective resolutions of right R-modules. In this paper, for a left coherent and right perfect ring R, we characterize the right global dimension of R, from another point of view, using the left derived functors of Hom and the right projective resolutions of right R-modules. It is shown that rD(R)≤n (n≥2) if and only if the gl right Proj-dim MR≤n - 2 if and only if Extn-1(N, M) = 0 for all right R-modules N and M if and only if every (n - 2)th Proj-cosyzygy of a right R-module has a projective envelope with the unique mapping property. It is also proved that rD(R)≤n (n≥1) if and only if every (n-1)th Proj-cosyzygy of a right R-module has an epic projective envelope if and only if every nth Vroj-cosyzygy of a right R-module is projective. As corollaries, the right hereditary rings and the rings R with rD(R)≤2 are characterized.     

Hopf代数交叉积的同调维数

Let H be a finite dimensional cocommutative Hopf algebra and A an H-module algebra, ln this paper, we characterize the projectivity (injectivity) of M as a left A#σ H-module when it is projective (injective) as a left A-module. The sufficient and necessary condition for A#σ H, the crossed product, to have finite global homological dimension is given, in terms of the global homological dimension of A and the surjectivity of trace maps, provided that H is cocommutative and A is commutative.     

Triangular Matrix Representations of Rings of Generalized Power Series

Let R be a ring and S a cancellative and torsion-free monoid and 〈 a strict order on S. If either （S,≤） satisfies the condition that 0 ≤ s for all s ∈ S, or R is reduced, then the ring [[R^S,≤]] of the generalized power series with coefficients in R and exponents in S has the same triangulating dimension as R. Furthermore, if R is a PWP ring, then so is [[R^S,≤]].     

RESEARCH ANNOUNCEMENTS Dagger Formal Geometry and de Rham Cohomology

Let K be a finite extension of Q_p with R its ring of integers and k=F_q its residue field.Let π be a uniformizer of R. At first, let us recall some concepts. A K-linear map L:M→M is called nuclear, if the following two conditions hold. (ⅰ) For every λ≠0 in K~(ac) the algebraic closure of K with g the minimal polynomial of λ over K, ∪(Ker(g(L)~n)) is of finite dimension. (ⅱ) The nonzero eigenvalues of L, form a finite set or a sequence with a limit 0. Let us define     

Derivations And Homomorphisms in Prime Rings

Let R be an associative ring, recall that an additive mapping d of R into itself is a derivation if for all x,y in R: d(xy)=d(x)y+xd(y) It is shown that structure of a ring is very tightly determined by the imposition of a special behavior on one of its derivations. analogously,we shall consider the problem: Suppose that R is a prime ring with nonzero derivation d such that the derivation d is a homomorphism (anti-     

Finitely Generated Flat Modules and a Characterization of Semiperfect Rings

Abstract

For a ring S, let K ₀(FGFl(S)) and K ₀(FGPr(S)) denote the Grothendieck groups of the category of all finitely generated flat S-modules and the category of all finitely generated projective S-modules respectively. We prove that a semilocal ring Ris semiperfect if and only if the group homomorphism K ₀(FGFl(R)) → K ₀(FGFl(R/J(R))) is an epimorphism and K ₀(FGFl(R)) = K ₀(FGPr(R)).     

Gorenstein projective dimensions of complexes

We show that over a right coherent left perfect ring R, a complex C of left R-modules is Gorenstein projective if and only if C ^m is Gorenstein projective in R-Mod for all m ∈ ℤ. Basing on this we show that if R is a right coherent left perfect ring then Gpd(C) = sup{Gpd(C ^m )|m ∈ ℤ} where Gpd(−) denotes Gorenstein projective dimension.     

Cone Length for DG Modules and Global Dimension of DG Algebras

As the definition of free class of differential modules over a commutative ring in [1 Avramov , L. L. , Buchweitz , R.-O. , Iyengar , S. ( 2007 ). Class and rank of differential modules . Invent. Math. 169 : 1 – 35 .[Crossref], [Web of Science ®] , [Google Scholar]], we define DG free class for semifree DG modules over an Adams connected DG algebra A. For any DG A-modules M, we define its cone length as the least DG free classes of all semifree resolutions of M. The cone length of a DG A-module plays a similar role as projective dimension of a module over a ring does in homological ring theory. The left (resp., right) global dimension of an Adams connected DG algebra A is defined as the supremum of the set of cone lengths of all DG A-modules (resp., A ^op -modules). It is proved that the definition is a generalization of that of graded algebras. Some relations between the global dimension of H(A) and the left (resp. right) global dimension of A are discovered. When A is homologically smooth, we prove that the left (right) global dimension of A is finite and the dimension of D(A) and D ^c (A) are not bigger than the DG free class of a minimal semifree resolution X of the DG A ^e -module A.     

Two Commuting Involutions Fixing RP1(2m + 1) S RP2(2m + 1)*

Let Z₂ denote a cyclic group of 2 order and Z₂² = Z₂ ×Z₂ the direct product of groups. Suppose that (M, Φ) is a closed and smooth manifold M with a smooth Z₂² -action whose fixed point set is the disjoint union of two real projective spaces with the same dimension. In this paper, the authors give a sufficient condition on the fixed data of the action for (M, Φ) bounding equivariantly.