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991.
Let M be a right R-module,
the class of all M-small modules, and P a projective cover of M in
[M]. We consider the torsion theories
= (
),
= (
), and
= (
) in
[M], where
is the torsion theory generated by
is the torsion theory cogenerated by
, and
is the dual Lambek torsion theory. We study some conditions for
to be cohereditary, stable, or split, and prove that Rej(M,
) = M
=
(=
=
)
=
GenM(P)
.2000 Mathematics Subject Classification: 16S90 相似文献
992.
The existence of Silnikov’s orbits in one coupled Duffing equation is discussed by using the fiber structure of invariant
manifold and high-dimensional Melnikov’s method. Example and numerical simulation results are also given to demonstrate the
theoretical analysis. 相似文献
993.
Hui Li 《Transactions of the American Mathematical Society》2003,355(11):4543-4568
Assume is a connected, compact 6-dimensional symplectic manifold equipped with a semi-free Hamiltonian circle action, such that the fixed point set consists of isolated points or compact orientable surfaces. We restrict attention to the case . We give a complete list of the possible manifolds, and determine their equivariant cohomology rings and equivariant Chern classes. Some of these manifolds are classified up to diffeomorphism. We also show the existence for a few cases.
994.
S. Halverscheid A. Iannuzzi 《Transactions of the American Mathematical Society》2003,355(11):4581-4594
Let be a homogeneous Riemannian manifold with , where denotes the universal complexification of . Under certain extensibility assumptions on the geodesic flow of , we give a characterization of the maximal domain of definition in for the adapted complex structure and show that it is unique. For instance, this can be done for generalized Heisenberg groups and naturally reductive homogeneous Riemannian spaces. As an application it is shown that the case of generalized Heisenberg groups yields examples of maximal domains of definition for the adapted complex structure which are neither holomorphically separable nor holomorphically convex.
995.
Sergey S. Kokarev 《General Relativity and Gravitation》2003,35(8):1399-1415
We show, that classical Kaluza-Klein theory possesses hidden nematic dynamics. It appears as a consequence of 1+4-decomposition procedure, involving 4D observers 1-form . After extracting of boundary terms the, so called, effective matter part of 5D geometrical action becomes proportional to the square of the anholonomicity 3-form d. It can be interpreted as twist nematic elastic energy, responsible for elastic reaction of 5D space-time on presence of anholonomic 4D submanifold, defined by . We derive both 5D covariant and 1+4 forms of the 5D nematic equilibrium equations, consider simple examples and discuss some 4D physical aspects of generic 5D nematic topological defects. 相似文献
996.
Stein Krogstad 《BIT Numerical Mathematics》2003,43(1):107-122
A low complexity Lie group method for numerical integration of ordinary differential equations on the orthogonal Stiefel manifold is presented. Based on the quotient space representation of the Stiefel manifold we provide a representation of the tangent space suitable for Lie group methods. According to this representation a special type of generalized polar coordinates (GPC) is defined and used as a coordinate map. The GPC maps prove to adapt well to the Stiefel manifold. For the n×k matrix representation of the Stiefel manifold the arithmetic complexity of the method presented is of order nk
2, and for nk this leads to huge savings in computation time compared to ordinary Lie group methods. Numerical experiments compare the method to a standard Lie group method using the matrix exponential, and conclude that on the examples presented, the methods perform equally on both accuracy and maintaining orthogonality. 相似文献
997.
Stefan M. Grünvogel 《Journal of Differential Equations》2003,187(2):201-225
We consider control affine systems of the form
998.
Hans-Otto Walther 《Journal of Differential Equations》2003,195(1):46-65
Let h>0, open, and continuously differentiable. If f satisfies two mild additional smoothness conditions then the set
999.
Raffaele Vitolo 《Acta Appl Math》2002,72(1-2):133-154
The C-spectral sequence was introduced by A. M. Vinogradov in the late Seventies as a fundamental tool for the study of the algebro-geometric properties of jet spaces and differential equations. A spectral sequence arises from the contact filtration of the modules of forms on jet spaces of a fibring (or on a differential equation). In order to avoid serious technical difficulties, the order of the jet space is not fixed, i.e., computations are performed on spaces containing forms on jet spaces of any order. In this paper we show that there exists a formulation of Vinogradov's C-spectral sequence in the case of finite-order jet spaces of a fibred manifold. We compute all cohomology groups of the finite-order C-spectral sequence. We obtain a finite-order variational sequence which is shown to be naturally isomorphic with Krupka's finite-order variational sequence. 相似文献
1000.
Elisabetta Barletta 《Annals of Global Analysis and Geometry》2002,22(2):99-118
We study CR submanifolds M in a Hopf manifold (C
H
N
(), J
0, g
0) with the Boothby metric g
0,of maximal CR dimension. Any such M is a CR manifold ofhypersurface type, although embedded in higher codimension, and itsanti-invariant distribution H(M) is spanned by a unit vectorfield U. We classify the CR submanifolds M for which = –J
0
Uis parallel in the normal bundle under assumptions on thespectrum of the Weingarten operator a
. We show that (1) ifa
(U) = (1/2)A (where A is the anti-Lee vector) andM fibres in tori over a CR submanifold of the complex projectivespace, then M lies on the (total space of the) pullback of the Hopf fibration via S C
P
N – 1, for some geodesic hypersphere S, and (2) if a
(U)= 0 and Spec(a
) = {0, c}, for some c R {0}, then M is locally a Riemannian product of totally geodesicsubmanifolds. 相似文献