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991.
Marius Crainic 《K-Theory》1999,17(4):319-362
We give a general method for computing the cyclic cohomology of crossed products by étale groupoids, extending the Feigin–Tsygan–Nistor spectral sequences. In particular we extend the computations performed by Brylinski, Burghelea, Connes, Feigin, Karoubi, Nistor, and Tsygan for the convolution algebra C
c
(G) of an étale groupoid, removing the Hausdorffness condition and including the computation of hyperbolic components. Examples like group actions on manifolds and foliations are considered. 相似文献
992.
On the stability of wavelet and Gabor frames (Riesz bases) 总被引:6,自引:0,他引:6
Zhang Jing 《Journal of Fourier Analysis and Applications》1999,5(1):105-125
If the sequence of functions j, k is a wavelet frame (Riesz basis) or Gabor frame (Riesz basis), we obtain its perturbation system j,k which is still a frame (Riesz basis) under very mild conditions. For example, we do not need to know that the support of or
is compact as in [14]. We also discuss the stability of irregular sampling problems. In order to arrive at some of our results, we set up a general multivariate version of Littlewood-Paley type inequality which was originally considered by Lemarié and Meyer [17], then by Chui and Shi [9], and Long [16]. 相似文献
993.
Using a family of higher degree polynomials as a bridge, together with complex surgery techniques, we construct a homeomorphism
between any two limbs of the Mandelbrot set of equal denominator. Induced by these homeomorphisms and complex conjugation,
we obtain an involution between each limb and itself, whose fixed points form a topological arc. All these maps have counterparts
at the combinatorial level relating corresponding external arguments. Assuming local connectivity of the Mandelbrot set we
may conclude that the constructed homeomorphisms between limbs are compatible with the embeddings of the limbs in the plane.
As usual we plough in the dynamical planes and harvest in the parameter space. 相似文献
994.
Andrei E. Vityaev 《Journal of Geometric Analysis》1999,9(1):161-173
We study uniqueness of an H∞ optimization problem which is central to the worst case frequency domain system design. It was known that if the so-called
sublevel sets are strictly convex inC
N, then the uniqueness holds. On the other hand, there are examples of non-uniqueness if the sublevel sets are just strictly
pseudoconvex.
In this paper we prove that uniqueness holds for a type of convexity which is strictly in-between geometric and pseudoconvexity. 相似文献
995.
Given a compact, oriented Riemannian manifold M, without boundary, and a codimension-one homology class in H* (M, Z) (or, respectively, in H* (M, Zp) with p an odd prime), we consider the problem of finding a cycle of least area in the given class: this is known as the
homological Plateau’s problem.
We propose an elliptic regularization of this problem, by constructing suitable fiber bundles ξ (resp. ζ) on M, and one-parameter
families of functionals defined on the regular sections of ξ, (resp. ζ), depending on a small parameter ε.
As ε → 0, the minimizers of these functionals are shown to converge to some limiting section, whose discontinuity set is exactly
the minimal cycle desired. 相似文献
996.
Olaf Bröcker 《Journal of Geometry》2002,75(1-2):46-60
For M?bius planes Schaeffer [9] has proved that all seven
point degenerations of Miquel's Theorem characterize miquelian M?bius
planes. For Laguerre planes we have several degenerations of Miquel's
Theorem with eight and seven points. We prove that all except one of
these degenerations characterize miquelian Laguerre planes. The
remaining degeneration characterizes elation Laguerre planes.
Received 14 September 2001; revised 1 September 2002. 相似文献
997.
Loïc Colson 《BIT Numerical Mathematics》1992,32(1):5-9
We present a primitive recursive programinf_with_lists computing the minimum of two natural numbersn andp (written in unary notation) and using primitive recursion on lists. This program has at first sight the required property of visiting simultaneously its inputs, so it is a counterexample to a theorem showing that such a program cannot be written in the language of primitive recursion on natural numbers, in the more general framework of primitive recursion on term algebras. However, its complexity is at leastinf(n,p)2 so it does not implement the algorithm we have in mind to computeinf(n,p). 相似文献
998.
We consider the problem of constructing a graphG* from a collection of isomorphic copies of a graphG in such a way that for every two copies ofG, either no vertices or a section graph isomorphic to a graphH is identified. It is shown that ifG can be partitioned into vertex-disjoint copies ofH, thenG* can be made to have at most |H| orbits. A condition onG so thatG* can be vertextransitive is also included. 相似文献
999.
Alois Würger 《Zeitschrift für Physik B Condensed Matter》1994,94(1-2):173-186
A Mori approach to the dynamics of coupled tunnelling units in defect crystals is presented. Transverse and longitudinal correlation functions of a two-level system are given as continued fractions; the memory kernels are evaluated in a usual decoupling approximation. Due to the random configuration of the defects on the host lattice both two-level splitting and relaxation rates show a broad distribution; the corresponding distribution function is derived for the case of a dipolar interaction of the defects. The theory covers both weak and strong coupling; the average interaction energy turns out to be the essential parameter. Dependence on frequency, temperature and concentration of the dynamical susceptibility is discussed. When passing from weak to strong coupling, the zero-temperature susceptibility shows a crossover from a constant value to a decrease with the third power of inverse defect concentration; there is quite a strong relaxational peak in the susceptibility. The theory accounts for several features observed in a recent low-frequency experiment on KCl:Li. 相似文献
1000.
Huiling Le 《Probability Theory and Related Fields》1996,106(1):137-149
Summary. Suppose that M is a complete, simply connected Riemannian manifold of non-positive sectional curvature with dimension m ≧ 3. If, outside a fixed compact set, the sectional curvatures are bounded above by a negative constant multiple of the inverse
of the square of the geodesic distance from a fixed point and below by another negative constant multiple of the square of
the geodesic distance, then the angular part of Brownian motion on M tends to a limit as time tends to infinity, and the closure of the support of the distribution of this limit is the entire
S
m−1
. This improves a result of Hsu and March.
Received: 7 December 1994/In revised form: 2 September 1995 相似文献