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1.
Graded rings and essential ideals 总被引:1,自引:0,他引:1
LetG be a group andA aG-graded ring. A (graded) idealI ofA is (graded) essential ifI⊃J≠0 wheneverJ is a nonzero (graded) ideal ofA. In this paper we study the relationship between graded essential ideals ofA, essential ideals of the identity componentA
e
and essential ideals of the smash productA#G
*. We apply our results to prime essential rings, irredundant subdirect sums and essentially nilpotent rings. 相似文献
2.
Declan Quinn 《Israel Journal of Mathematics》1991,73(1):113-121
In this paper we study integral extensions of noncommutative rings. To begin, we prove that finite subnormalizing extensions
are integral. This is done by proving a generalization of the Paré-Schelter result that a matrix ring is integral over the
coefficient ring. Our methods are similar to those of Lorenz and Passman, who showed that finite normalizing extensions are
integral. As corollaries we note that the (twisted) smash product over the restricted enveloping algebra of a finite dimensional
restricted Lie algebra is integral over the coefficient ring and then prove a Going Up theorem for prime ideals in these ring
extensions.
Next we study automorphisms of rings. In particular, we prove an integrality theorem for algebraic automorphisms. Combining
group gradings and actions, we show that if a ringR is graded by a finite groupG, andH is a finite group of automorphisms ofR that permute the homogeneous components, with the order ofH invertible inR, thenR is integral overR
1
H
, the fixed ring of the identity component. This, in turn, is used to prove our final result: Suppose that ifH is a finite dimensional semisimple cocommutative Hopf algebra over an algebraically closed field of positive characteristic.
IfR is anH-module algebra, thenR is integral overR
H
, its subring of invariants. 相似文献
3.
LetA={a
1, …,a
k} and {b
1, …,b
k} be two subsets of an abelian groupG, k≤|G|. Snevily conjectured that, when |G| is odd, there is a numbering of the elements ofB such thata
i+b
i,1≤i≤k are pairwise distinct. By using a polynomial method, Alon affirmed this conjecture for |G| prime, even whenA is a sequence ofk<|G| elements. With a new application of the polynomial method, Dasgupta, Károlyi, Serra and Szegedy extended Alon’s result to
the groupsZ
p
r
andZ
p
rin the casek<p and verified Snevily’s conjecture for every cyclic group. In this paper, by employing group rings as a tool, we prove that
Alon’s result is true for any finite abelianp-group withk<√2p, and verify Snevily’s conjecture for every abelian group of odd order in the casek<√p, wherep is the smallest prime divisor of |G|.
This work has been supported partly by NSFC grant number 19971058 and 10271080. 相似文献
4.
For a torsion or torsion-free group G and a field F, we characterize the group algebra FG that is Armendariz. Armendariz property for a group ring over a general ring R is also studied and related to those of Abelian group rings and the quaternion ring over R. 相似文献
5.
Tom Cheatham 《Israel Journal of Mathematics》1979,33(2):172-176
R will denote a commutative integral domain with quotient fieldQ. A torsion-free cover of a moduleM is a torsion-free moduleF and anR-epimorphism σ:F→M such that given any torsion-free moduleG and λ∈Hom
R
(G, M) there exists μ∈Hom
R
(G,F) such that σμ=λ. It is known that ifM is a maximal ideal ofR, R→R/M is a torsion-free cover if and only ifR is a maximal valuation ring. LetE denote the injective hull ofR/M thenR→R/M extends to a homomorphismQ→E. We give necessary and sufficient conditions forQ→E to be a torsion-free cover. 相似文献
6.
Yong Wang 《manuscripta mathematica》1993,81(1):79-87
LetR be a semiprimary ring. We show that if the left generalized projective dimension (defined below) of
R
(R/J
2) is finite, then the injectively defined left finitistic dimension ofR is finite. 相似文献
7.
Abraham Zaks 《Israel Journal of Mathematics》1971,10(4):442-450
LetR be a bounded Noetherian Prime ring. The Asano-Michler theorem shows thatR is a bounded Dedekind ring if every prime ideal ofR is invertible. We provide a simple proof of the Asano-Michler theorem, and we suggest some possible generalizations. We also
prove that if the proper residue rings ofR areQF-rings thenR is a bounded Dedekind ring, and generalize this result toLD-rings. 相似文献
8.
We study the Cohn purity in an abelian group regarded as a left module over its endomorphism ring. We prove that if a finite rank torsion-free abelian group G is quasiequal to a direct sum in which all summands are purely simple modules over their endomorphism rings then the module E(G)
G is purely semisimple. This theorem makes it possible to construct abelian groups of any finite rank which are purely semisimple over their endomorphism rings and it reduces the problem of endopure semisimplicity of abelian groups to the same problem in the class of strongly indecomposable abelian groups. 相似文献
9.
LetG be a finite transitive permutation group on a finite setS. LetA be a nonempty subset ofS and denote the pointwise stabilizer ofA inG byC
G
(A). Our main result is the following inequality: [G :C
G
(A)]≥|G||A|/|S|.
This paper is a part of the author’s Ph.D. thesis research, carried out at Tel Aviv University under the supervision of Professor
Marcel Herzog. 相似文献
10.
J. T. Stafford 《Israel Journal of Mathematics》1983,45(1):33-40
Letk be a field. WriteD(G) for the quotient division ring of the group ringkG of a torsion-free, polycyclic-by-finite groupG, andD(g) for the quotient ring of the enveloping algebra of a finite-dimensional Lie algebrag overk. In this note we show that the Hirsch numberh(G) and dim k g are invariants for the respective division rings, by calculating the Krull and global dimensions ofD(G)? k D(G) andD(g)? k D(g). 相似文献
11.
Eben Matlis 《Israel Journal of Mathematics》1980,37(3):211-230
LetR be an integral domain andI a non-zero ideal ofR. The canonical mapR→R/I is called atorsion-free cover ofR/I if everyR-homomorphism from a torsion-freeR-module intoR/I can be factored throughR. The main result of this paper is thatR→R/I is a torsion-free cover if and only ifR is complete in theR-topology andI is an ideal of injective dimension 1. In this caseI is contained in the Jacobson radical ofR. And if Λ is the endomorphism ring ofI, then Λ is a quasi-local domain. IfI is a flatR-module, thenQ→Q/Λ is a torsion-free cover, whereQ is the quotient field ofR. And thenQ/Λ is an indecomposable injectiveR (and Λ) module. Special results are obtained ifR is a Noetherian domain or a Prüfer domain. 相似文献
12.
LetG be a fixed graph and letX
G be the number of copies ofG contained in the random graphG(n, p). We prove exponential bounds on the upper tail ofX
G which are best possible up to a logarithmic factor in the exponent. Our argument relies on an extension of Alon’s result
about the maximum number of copies ofG in a graph with a given number of edges. Similar bounds are proved for the random graphG(n, M) too.
Research of the second author supported by KBN grant 2 P03A 027 22.
Research of the third author supported by KBN grant 2 P03A 15 23. 相似文献
13.
LetG be a group andRG be its group ring. IfA is a nonzero ideal ofRG, we prove that for certain normal subgroupsH ofG, including all nontrivial subgroups ofG whenG is a free product,A∩RH≠0. 相似文献
14.
LetR be a ring and σ an automorphism ofR. We prove the following results: (i)J(R
σ[x])={Σiri
x
i:r0∈I∩J(R]),
r
i∈I for alliε 1} whereI↪ {r∈R:rx ∈J(R
Σ[x])|s= (ii)J(R
σ<x>)=(J(R
σ<x>)∩R)σ<x>. As an application of the second result we prove that ifG is a solvable group such thatG andR, + have disjoint torsions thenJ(R)=0 impliesJ(R(G))=0. 相似文献
15.
M. A. Turmanov 《Journal of Mathematical Sciences》2006,137(6):5336-5345
Torsion-free Abelian groups G and H are called quasi-equal (G ≈ H) if λG ⊂ H ⊂ G for a certain natural number ≈. It is known (see [3]) that the quasi-equality of torsion-free Abelian groups can be represented
as the equality in an appropriate factor category. Thus while dealing with certain group properties it is usual to prove that
the property under consideration is preserved under the transition to a quasi-equal group. This trick is especially frequently
used when the author investigates module properties of Abelian groups; here a group is considered as a left module over its
endomorphism ring. On the other hand, a topical problem in the Abelian group theory is the problem of investigation of pureness
in the category of Abelian groups (see [4]). We consider the pureness introduced by P. Cohn [2] for Abelian groups as modules
over their endomorphism rings. Particularity of the investigation of the properties of pureness for the Abelian group G as the module
E
(G)G lies in the fact that this is a more general situation than the investigation of pureness for a unitary module over an arbitrary
ring R with the identity element. Indeed, if
R
M is an arbitrary unitary left module and M
+ is its Abelian group, then each element from R can be identified with an appropriate endomorphism from the ring E(M
+) under the canonical ring homomorphism R → E(M
+). Then it holds that if
E(M+)
N is a pure submodule in
E(M+)
M
+, then
R
N is a pure submodule in
R
M. In the present paper the interrelations between pureness, servantness, and quasi-decompositions for Abelian torsion-free
groups of finite rank will be investigated.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 10, No. 2, pp. 225–238,
2004. 相似文献
16.
Let R be a ring graded by an abelian group.We study prime ideals of R that are maximal for not containing nonzero homogeneous elements.Also prime ideals of the symmetric graded Martindale ring of quotients of R are investigated.The results are applied to study when R is a Jacobson ring in case R is a Z-graded ring or a group ring of a finitely generated abelian group, or in case R is right Noetherian and strongly graded by a polycyclic-by-finite group. 相似文献
17.
R. Yu. Evstaf’ev 《Ukrainian Mathematical Journal》2006,58(9):1433-1440
Let R be an Artinian ring, not necessarily with a unit, and let R
o be the group of all invertible elements of R with respect to the operation a o b = a + b + ab. We prove that the group R
o is a nilpotent group if and only if it is an Engel group and the quotient ring of the ring R by its Jacobson radical is commutative. In particular, R
o is nilpotent if it is a weakly nilpotent group or an n-Engel group for some positive integer n. We also establish that the ring R is strictly Lie-nilpotent if and only if it is an Engel ring and the quotient ring of the ring R by its Jacobson radical is commutative.
__________
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 9, pp. 1264–1270, September, 2006. 相似文献
18.
J. V. Kostromina 《Journal of Mathematical Sciences》2014,197(5):635-648
In this work, we investigate relations between Malcev’s matrices of a torsion-free group G of finite rank and Malcev’s matrices of groups Hom(R,G) and Hom(G,R), where G is a locally free group and R is a torsion-free group of rank 1. 相似文献
19.
Henri Moscovici 《Israel Journal of Mathematics》1973,15(3):230-236
LetG be a Lie group,H a closed subgroup,L a unitary representation ofH andU
L the corresponding induced representation onG. The main result of this paper, extending Ol’ŝanskii’s version of the Frobenius reciprocity theorem, expresses the intertwining
number ofU
L and an irreducible unitary representationV ofG in terms ofL and the restriction ofV
∞ toH. 相似文献
20.