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1.
We define thek-th commutator forx, y in a ringR inductively as follows: [x,y]1=[x,y]=xy−yx and [x,y]
k
=[[x,y]
k−1, y
]. Assume thatR is a ring without nonzero nil onesided ideals. The following are shown: (1) If [x,y]
k
is nilpotent for allx,y∈R, thenR must be commutative. (2) If [x,y]
k
is power central for allx,y∈R, thenR must satisfy the standard polynomial of degree 4.
1980 Mathematics Subject Classification (1985 Revision). Primary 16A70, Secondary 16A12. 相似文献
2.
Huanyin CHEN 《数学年刊B辑(英文版)》2009,30(3):221-230
The necessary and sufficient conditions under which a ring satisfies regular power-substitution are investigated. It is shown that a ring R satisfies regular powersubstitution if and only if a-b in R implies that there exist n ∈ N and a U E GLn (R) such that aU = Ub if and only if for any regular x ∈ R there exist m,n ∈ N and U ∈ GLn(R) such that x^mIn = xmUx^m, where a-b means that there exists x,y, z∈ R such that a =ybx, b = xaz and x= xyx = xzx. It is proved that every directly finite simple ring satisfies regular power-substitution. Some applications for stably free R-modules are also obtained. 相似文献
3.
Chmielinski has proved in the paper [4] the superstability of the generalized orthogonality equation |〈f(x), f(y)〉| = |〈x,y〉|. In this paper, we will extend the result of Chmielinski by proving a theorem: LetD
n be a suitable subset of ℝn. If a function f:D
n → ℝn satisfies the inequality ∥〈f(x), f(y)〉| |〈x,y〉∥ ≤ φ(x,y) for an appropriate control function φ(x, y) and for allx, y ∈ D
n, thenf satisfies the generalized orthogonality equation for anyx, y ∈ D
n. 相似文献
4.
5.
I. N. Herstein [10] proved that a prime ring of characteristic not two with a nonzero derivation d satisfying d(x)d(y) = d(y)d(x) for all x, y must be commutative, and H. E. Bell and M. N. Daif [8] showed that a prime ring of arbitrary characteristic with nonzero derivation d satisfying d(xy) = d(yx) for all x, y in some nonzero ideal must also be commutative. For semiprime rings, we show that an inner derivation satisfying the condition of Bell and Daif on a nonzero ideal must be zero on that ideal, and for rings with identity, we generalize all three results to conditions on derivations of powers and powers of derivations. For example, let R be a prime ring with identity and nonzero derivation d, and let m and n be positive integers such that, when charR is finite, m ∨ n < charR. If d(x m y n ) = d(y n x m ) for all x, y ∈ R, then R is commutative. If, in addition, charR≠ 2 and the identity is in the image of an ideal I under d, then d(x) m d(y) n = d(y) n d(x) m for all x, y ∈ I also implies that R is commutative. 相似文献
6.
Zhu Xuexian 《分析论及其应用》1989,5(3):83-92
We show that if K(x,y)=Ω(x,y)/|x|n|y|m is a Calder n-Zygmund kerned on Rn×Rm, where Ω∈L2(Sn−1×Sm−1) and b(x,y) is any bounded function which is radial with x∈Rn and y∈Rm respectively, then b(x,y)K(x,y) is the kernel of a convolution operator which is bounded on Lp(Rn×Rm) for 1<p<∞ and n≧2, m≧2.
Project supported by NSFC 相似文献
7.
The complementarity problem with a nonlinear continuous mappingf from the nonnegative orthantR
+
n
ofR
n intoR
n can be written as the system of equationsF(x, y) = 0 and(x, y) R
+
2n
, whereF denotes the mapping from the nonnegative orthantR
+
2n
ofR
2n intoR
+
n
× Rn defined byF(x, y) = (x
1y1,,xnyn, f1(x) – y1,, fn(x) – yn) for every(x, y) R
+
2n
. Under the assumption thatf is a uniformP-function, this paper establishes that the mappingF is a homeomorphism ofR
+
2n
ontoR
+
n
× Rn. This result provides a theoretical basis for a new continuation method of tracing the solution curve of the one parameter family of systems of equationsF(x, y) = tF(x
0, y0) and(x, y) R
+
2n
from an arbitrary initial point(x
0, y0) R
+
2n
witht = 1 until the parametert attains 0. This approach is an extension of the one used in the polynomially bounded algorithm recently given by Kojima, Mizuno and Yoshise for solving linear complementarity problems with positive semi-definite matrices. 相似文献
8.
IBN rings and orderings on grothendieck groups 总被引:2,自引:0,他引:2
Tong Wenting 《数学学报(英文版)》1994,10(3):225-230
LetR be a ring with an identity element.R∈IBN means thatR
m⋟Rn impliesm=n, R∈IBN
1 means thatR
m⋟Rn⊕K impliesm≥n, andR∈IBN
2 means thatR
m⋟Rm⊕K impliesK=0. In this paper we give some characteristic properties ofIBN
1 andIBN
2, with orderings on the Grothendieck groups. In addition, we obtain the following results: (1) IfR∈IBN
1 and all finitely generated projective leftR-modules are stably free, then the Grothendieck groupK
0(R) is a totally ordered abelian group. (2) If the pre-ordering of the Grothendieck groupK
0(R) of a ringR is a partial ordering, thenR∈IBN
1 orK
0(R)=0.
Supported by National Nature Science Foundation of China. 相似文献
9.
Let G=(I
n
,E) be the graph of the n-dimensional cube. Namely, I
n
={0,1}
n
and [x,y]∈E whenever ||x−y||1=1. For A⊆I
n
and x∈A define h
A
(x) =#{y∈I
n
A|[x,y]∈E}, i.e., the number of vertices adjacent to x outside of A. Talagrand, following Margulis, proves that for every set A⊆I
n
of size 2
n−1
we have for a universal constant K independent of n. We prove a related lower bound for graphs: Let G=(V,E) be a graph with . Then , where d(x) is the degree of x. Equality occurs for the clique on k vertices.
Received: January 7, 2000
RID="*"
ID="*" Supported in part by BSF and by the Israeli academy of sciences 相似文献
10.
Let R be a prime ring of char R ≠ 2 with a nonzero derivation d and let U be its noncentral Lie ideal. If for some fixed integers n
1 ⩾ 0, n
2 ⩾ 0, n
3 ⩾ 0, (u
n1 [d(u), u]u
n2)
n3 ∈ Z(R) for all u ∈ U, then R satisfies S
4, the standard identity in four variables. 相似文献
11.
P. Penner 《Algebra Universalis》1981,13(1):307-314
Following W. Taylor we define a hyperidentity ∈ to be formally the same as an identity (e.g.,F(G(x, y, z), G(x, y, z))=G(x, y, z)). However, a varietyV is said to satisfy a hyperidentity ∈, if whenever the operation symbols of ∈ are replaced by any choice of polynomials (appropriate
forV) of the same arity as the corresponding operation symbols of ∈, then the resulting identity holds inV in the usual sense. For example, if a varietyV of type <2,2> with operation symbols ∨ and ∧ satisfies the hyperidentity given above, then substituting the polynomial (x∨y)∨z
for the symbolG, and the polynomialx∧y forF, we see thatV must in particular satisfy the identity ((x∨y)∨z)∧((x∨y)∨z)=((x∨y)∨z). The set of all hyperidentities satisfied by a varietyV, will be denoted byH(V). We shall letH
m
(V) be the set of all hyperidentities hoiding inV with operation symbols of arity at mostm, andH
n
(V) will denote the set of all hyperidentities ofV with at mostn distinct variables. In this paper we shall show that ifV is a nontrivial variety of lattices or the variety of all semilattices, then for any integersm andn, there exists a hyperidentity ∈ such that ∈ holds inV, and ∈ is not a consequence ofH
m
(V)∪H
n
(V). From this it is deduced that the hyperidentities ofV are not finitely based, partly soling a problem of Taylor [7, Problem 3].
The research of the author was supported by NSERC of Canada.
Presented by W. Taylor. 相似文献
12.
Let R be a noncommutative prime ring of characteristic different from 2, let Z(R) be its center, let U be the Utumi quotient ring of R, let C be the extended centroid of R, and let f(x
1,..., x
n
) be a noncentral multilinear polynomial over C in n noncommuting variables. Denote by f(R) the set of all evaluations of f(x
1, …, xn) on R. If F and G are generalized derivations of R such that [[F(x), x], [G(y), y]] ∈ Z(R) for any x, y ∈ f(R), then one of the following holds:
(1) |
there exists α ∈ C such that F(x) = αx for all x ∈ R 相似文献
13.
Let R be a prime ring of char R≠2, d a non-zero derivation of R and ρ a non-zero right ideal of R such that [[d(x),d(y)]n [y,x]m] = 0 for all x,y ∈ ρ or [[d(x),d(y)]n d[y,x]m] = 0 for all x,y ∈ ρ, n, m ≥ 0 are fixed integers. If [ρ,ρ]ρ ≠ 0, then d(ρ)ρ = 0. 相似文献
14.
Bronislaw Wajnryb 《Israel Journal of Mathematics》1982,43(2):169-176
LetR be a Krull subring of a ring of polynomialsk[x
1, …, xn] over a fieldk. We prove that ifR is generated by monomials overk thenr is affine. We also construct an example of a non-affine Krull ringR, such thatk[x, xy]⊂R⊂k[x, y], and a non-Noetherian Krull ringS, such thatk[x, xy, z]⊂S⊂k[x, y, z]. 相似文献
15.
Soon-Mo Jung Byungbae Kim 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1999,69(1):293-308
A result of Skof and Terracini will be generalized; More precisely, we will prove that if a functionf : [-t, t]n →E satisfies the inequality (1) for some δ > 0 and for allx, y ∈ [-t, t]n withx + y, x - y ∈ [-t, t]n, then there exists a quadratic functionq: ℝn →E such that ∥f(x) -q(x)∥ < (2912n2 + 1872n + 334)δ for anyx ∈ [-t, t]
n
. 相似文献
16.
We realize the Perron effect of change of values of characteristic exponents: for arbitrary parameters λ
1 <- λ
2 < 0, β
2 ≥ β
1 ≥ λ
2, and m > 1, we prove the existence of a linear differential system $
\dot x
$
\dot x
= A(t)x, x ∈ R
2, t ≥ t
0, with bounded infinitely differentiable coefficients and with characteristic exponents λ
1(A) = λ
1 <- λ
2(A) = λ
2 and of an m-perturbation f: [t
0,+∞) × R
2 → R
2 infinitely differentiable in time, continuously differentiable with respect to the phase variables y
1 and y
2, (y
1, y
2) = y ∈ R
2 (infinitely differentiable with respect to the variables y
1 ≠ 0 and y
2 ≠ 0 and with respect to all of these variables in the case of a positive integer m > 1), satisfying the condition ‖f(t, y)‖ ≤ const × ‖y‖
m
, y ∈ R
2, t ≥ t
0, and such that all nontrivial solutions y(t, c) of the perturbed system
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