共查询到20条相似文献,搜索用时 31 毫秒
1.
On the product of two generalized derivations 总被引:2,自引:0,他引:2
Mohamed Barraa Steen Pedersen 《Proceedings of the American Mathematical Society》1999,127(9):2679-2683
Two elements and in a ring determine a generalized derivation on by setting for any in . We characterize when the product is a generalized derivation in the cases when the ring is the algebra of all bounded operators on a Banach space , and when is a -algebra . We use these characterizations to compute the commutant of the range of .
2.
Yifeng Xue 《Proceedings of the American Mathematical Society》1999,127(12):3671-3676
Suppose that is a unital purely infinite simple -algebra. If the class [1] of the unit 1 in has torsion, then ; if [1] is torsion-free in , then . If is a non-unital purely infinite simple -algebra, then .
3.
Mahan Mitra 《Proceedings of the American Mathematical Society》1999,127(6):1625-1631
Let be an exact sequence of hyperbolic groups induced by an automorphism of the free group . Let be a finitely generated distorted subgroup of . Then there exist and a free factor of such that the conjugacy class of is preserved by and contains a finite index subgroup of a conjugate of . This is an analog of a theorem of Scott and Swarup for surfaces in hyperbolic 3-manifolds.
4.
Grzegorz Zwara 《Proceedings of the American Mathematical Society》1999,127(5):1313-1322
Let be a representation-finite algebra. We show that a finite dimensional -module degenerates to another -module if and only if the inequalities hold for all -modules . We prove also that if for any indecomposable -module , then any degeneration of -modules is given by a chain of short exact sequences.
5.
Li Jiankui 《Proceedings of the American Mathematical Society》1999,127(1):235-239
In this paper, we prove that if is an -dimensional subspace of , then is -reflexive, where denotes the greatest integer not larger than . By the result, we show that if is an elementary operator on a -algebra , then is completely positive if and only if is -positive.
6.
Greg Hjorth 《Proceedings of the American Mathematical Society》1999,127(1):271-278
Let be a Polish group, a Polish topology on a space , acting continuously on , with -invariant and in the Borel algebra generated by . Then there is a larger Polish topology on so that is open with respect to , still acts continuously on , and has a basis consisting of sets that are of the same Borel rank as relative to .
7.
Y. Abe 《Proceedings of the American Mathematical Society》1999,127(3):847-849
We use a variant of the diamond principle to show many ideals on are not -saturated if is large. For instance, the -indescribable ideal is not -saturated if is almost ineffable.
8.
Daniel Katz 《Proceedings of the American Mathematical Society》1999,127(9):2601-2609
Let be an unramified regular local ring having mixed characteristic and the integral closure of in a th root extension of its quotient field. We show that admits a finite, birational module such that . In other words, admits a maximal Cohen-Macaulay module.
9.
J. Marshall Ash Michael Ganzburg 《Proceedings of the American Mathematical Society》1999,127(1):211-216
Let be a trigonometric polynomial of degree The problem of finding the largest value for in the inequality is studied. We find exactly provided is the conjugate of an even integer and For general we get an interval estimate for where the interval length tends to as tends to
10.
William S. Cohn 《Proceedings of the American Mathematical Society》1999,127(2):509-517
We show that a function is the derivative of a function in the Hardy space of the unit disk for if and only if where and . Here, can be chosen to be non-vanishing, , and . As an application, we characterize positive measures on the unit disk such that the operator is bounded from the tent space to , where .
11.
Periodic solutions of a periodic delay predator-prey system 总被引:19,自引:0,他引:19
Li Yongkun 《Proceedings of the American Mathematical Society》1999,127(5):1331-1335
The existence of a positive periodic solution for
is established, where , , , , are positive periodic continuous functions with period , and , are periodic continuous functions with period .
12.
Robert Gilmer William Heinzer Moshe Roitman 《Proceedings of the American Mathematical Society》1999,127(11):3141-3151
Suppose is a maximal ideal of a commutative integral domain and that some power of is finitely generated. We show that is finitely generated in each of the following cases: (i) is of height one, (ii) is integrally closed and , (iii) is a monoid domain over a field , where is a cancellative torsion-free monoid such that , and is the maximal ideal . We extend the above results to ideals of a reduced ring such that is Noetherian. We prove that a reduced ring is Noetherian if each prime ideal of has a power that is finitely generated. For each with , we establish existence of a -dimensional integral domain having a nonfinitely generated maximal ideal of height such that is -generated.
13.
Yuan-chung Sheu 《Proceedings of the American Mathematical Society》1999,127(12):3721-3728
Consider an -superdiffusion on , where is an uniformly elliptic differential operator in , and . The -polar sets for are subsets of which have no intersection with the graph of , and they are related to the removable singularities for a corresponding nonlinear parabolic partial differential equation. Dynkin characterized the -polarity of a general analytic set in term of the Bessel capacity of , and Sheu in term of the restricted Hausdorff dimension. In this paper we study in particular the -polarity of sets of the form , where and are two Borel subsets of and respectively. We establish a relationship between the restricted Hausdorff dimension of and the usual Hausdorff dimensions of and . As an application, we obtain a criterion for -polarity of in terms of the Hausdorff dimensions of and , which also gives an answer to a problem proposed by Dynkin in the 1991 Wald Memorial Lectures.
14.
Let be a non-trivial finite Galois extension of a field . In this paper we investigate the role that valuation-theoretic properties of play in determining the non-triviality of the relative Brauer group, , of over . In particular, we show that when is finitely generated of transcendence degree 1 over a -adic field and is a prime dividing , then the following conditions are equivalent: (i) the -primary component, , is non-trivial, (ii) is infinite, and (iii) there exists a valuation of trivial on such that divides the order of the decomposition group of at .
15.
Konrad J. Swanepoel 《Proceedings of the American Mathematical Society》1999,127(7):2155-2162
A hollow axis-aligned box is the boundary of the cartesian product of compact intervals in . We show that for , if any of a collection of hollow axis-aligned boxes have non-empty intersection, then the whole collection has non-empty intersection; and if any of a collection of hollow axis-aligned rectangles in have non-empty intersection, then the whole collection has non-empty intersection. The values for and for are the best possible in general. We also characterize the collections of hollow boxes which would be counterexamples if were lowered to , and to , respectively.
16.
B. Sury 《Proceedings of the American Mathematical Society》1999,127(4):951-953
Recently, W. D. Gao (1996) proved the following theorem: For a cyclic group of prime order, and any element in it, and an arbitrary sequence of elements from , the number of ways of writing as a sum of exactly of the 's is or modulo according as is zero or not. The dual purpose of this note is (i) to give an entirely different type of proof of this theorem; and (ii) to solve a conjecture of J. E. Olson (1976) by answering an analogous question affirmatively for solvable groups.
17.
Y. Bahturin A. Giambruno M. Zaicev 《Proceedings of the American Mathematical Society》1999,127(1):63-69
Let be an algebra over a field and a finite group of automorphisms and anti-automorphisms of . We prove that if satisfies an essential -polynomial identity of degree , then the -codimensions of are exponentially bounded and satisfies a polynomial identity whose degree is bounded by an explicit function of . As a consequence we show that if is an algebra with involution satisfying a -polynomial identity of degree , then the -codimensions of are exponentially bounded; this gives a new proof of a theorem of Amitsur stating that in this case must satisfy a polynomial identity and we can now give an upper bound on the degree of this identity.
18.
On zeros of characters of finite groups 总被引:2,自引:0,他引:2
David Chillag 《Proceedings of the American Mathematical Society》1999,127(4):977-983
We present several results connecting the number of conjugacy classes of a finite group on which an irreducible character vanishes, and the size of some centralizer of an element. For example, we show that if is a finite group such that , then has an element , such that , where is the maximal number of zeros in a row of the character table of . Dual results connecting the number of irreducible characters which are zero on a fixed conjugacy class, and the degree of some irreducible character, are included too. For example, the dual of the above result is the following: Let be a finite group such that ; then has an irreducible character such that , where is the maximal number of zeros in a column of the character table of .
19.
Chia-Hsin Liu 《Proceedings of the American Mathematical Society》1999,127(2):327-336
Let be the group algebra of a group over a field , and let be its group of units. A conjecture by Brian Hartley asserts that if is a torsion group and satisfies a group identity, then satisfies a polynomial identity. This was verified earlier in case is an infinite field. Here we modify the original proof so that it handles fields of all sizes.
20.
Marc-Olivier Gebuhrer Ryszard Szwarc 《Proceedings of the American Mathematical Society》1999,127(6):1705-1709
Let be a discrete polynomial hypergoup on with Plancherel measure If the hypergroup is symmetric, the set of characters can be identified with a compact subset of the real line which contains the support of We show that the lower and upper bounds of and coincide. In particular, the trivial character belongs to the support of the Plancherel measure.