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201.
Oka's principle for holomorphic submersions with sprays 总被引:3,自引:0,他引:3
We classify, up to a local isometry, all non-K?hler almost K?hler 4-manifolds for which the fundamental 2-form is an eigenform
of the Weyl tensor, and whose Ricci tensor is invariant with respect to the almost complex structure. Equivalently, such almost
K?hler 4-manifolds satisfy the third curvature condition of A. Gray. We use our local classification to show that, in the
compact case, the third curvature condition of Gray is equivalent to the integrability of the corresponding almost complex
structure.
Received: 1 October 2001 / Published online: 17 June 2002 相似文献
202.
An algebra A over a field k is FCR if every finite dimensional representation of A is completely reducible and the intersection of the kernels of these representations is zero. We give a useful characterization
of FCR-algebras and apply this to C
*-algebras and to localizations. Moreover, we show that “small” products and sums of FCR-algebras are again FCR.
Received: 25 October 2000 相似文献
203.
Rafael López 《Monatshefte für Mathematik》2008,154(4):289-302
In this paper we study surfaces in Euclidean 3-space foliated by pieces of circles that satisfy a Weingarten condition of
type aH + bK = c, where a,b and c are constant, and H and K denote the mean curvature and the Gauss curvature respectively. We prove that such a surface must be a surface of revolution,
one of the Riemann minimal examples, or a generalized cone.
Authors’ address: Departamento de Geometría y Topología, Universidad de Granada, 18071 Granada, Spain 相似文献
204.
For a positive integer n we let τ(n) denote the number of its positive divisors. In this paper, we obtain lower and upper bounds for the average value of the
ratio τ(n + 1)/τ(n) as n ranges through positive integers in the interval [1,x]. We also study the cardinality of the sets {τ(p − 1) : p ≤ x prime} and {τ(2n − 1) : n ≤ x}.
Authors’ addresses: Florian Luca, Instituto de Matemáticas, Universidad Nacional Autónoma'de'México, C.P. 58089, Morelia,
Michoacán, México; Igor E. Shparlinski, Department of Computing, Macquarie University, Sydney, NSW 2109, Australia 相似文献
205.
Evangelia Samiou 《manuscripta mathematica》2002,107(1):101-110
We construct a family of simply connected 2-step nilpotent Lie groups of higher rank such that every geodesic lies in a flat.
These are as Riemannian manifolds irreducible and arise from real representations of compact Lie algebras. Moreover we show
that groups of Heisenberg type do not even infinitesimally have higher rank.
Received: 2 July 2001 / Revised version: 19 October 2001 相似文献
206.
We study in this paper a construction of simple Jordan superalgebras from certain triple systems, in particular, we investigate
F type from a Jordan–Lie triple system minutely.
Received: April 11, 2000; in final form: July 20, 2001?Published online: July 9, 2002 相似文献
207.
John P. Elder 《Thermochimica Acta》1985,95(1):33-40
FORTRAN software is described which enables the generation of rate of weight change data (DTG) from percentage weight change measurements (TG), obtained under non-isothermal conditions. The program also transposes this information into the dimensionless extent and rate of reaction at unit temperature intervals by means of a cubic spline interpolation. A simple search routine identifies all DTG spikes in the thermogravimetric record, and the temperature and extent of reaction at which the rate attains its maximum value. This total information serves as input data for the kinetic analysis software to be discussed in part II of this communication. An example of the application of this program to the pyrolysis of bituminous coal is presented. 相似文献
208.
J. Ghijsen 《Journal of Electron Spectroscopy and Related Phenomena》1985,35(1):19-26
XPS and UPS investigations of PuFe2 add support to the claim that Pu 5f electrons are localized in this compound. The surface composition is similar to that of lanthanide—transition metal compounds. Some capacity for surface healing has been observed after exposure to the atmosphere. 相似文献
209.
Let X be a Banach space and let (ξj)j ≧ 1 be an i.i.d. sequence of symmetric random variables with finite moments of all orders. We prove that the following assertions
are equivalent:
Received: 10 January 2005; revised: 5 April 2005 相似文献
1. |
There exists a constant K such that
|
|
2. | X is isomorphic to a Hilbert space. |
210.
In this paper, we consider the following second-order three-point boundary value problem
where f : [0, 1] × R2 R is continuous, > 0, 0 < < 1 such that < 1. We give conditions on f and two pairs of lower and upper solutions to ensure the existence of at least three solutions of the given problem. Our method is based upon Leray-Schauder degree theory. The emphasis here is that f depends on the first derivative. Our results extend some results in the references.Received: 17 June 2004 相似文献