A uniformly quasiregular mapping, is a mapping of the m-sphere with the property that it and all its iterates have uniformly bounded distortion. Such maps are rational with respect to
some bounded measurable conformal structure and there is a Fatou-Julia type theory associated with the dynamical system obtained
by iterating these mappings. We begin by investigating the analogue of Siegel's theorem on the local conjuga cy of rotational
dynamics. We are led to consider the analytic continuation properties of solutions to the highly nonlinear first order Beltrami
systems. We reduce these problems to a central and well known conjecture in the theory of transformation groups; namely the
Hilbert-Smith conjecture, which roughly asserts that effective transformation groups of manifolds are Lie groups. Our affirmative
solution to this problem then implies unique analytic continuation and Siegel's theorem.
Received: 14 September 2000 / Revised version: 23 November 2001 / Published online: 5 September 2002
RID="*"
ID="*" Research supported in part by grants from the Marsden Fund and Royal Society (NZ). 相似文献
The sub-optimal Hankel norm approximation problem is solved under the assumptions that the system is given in terms of a triple of operators (–A, B, C), where–A is the infinitesimal generator of an exponentially stable, analytic semigroup on the Hilbert spaceZ,BL (m,Z where –1<0,CL is obtained in terms of the system parameters–A, B, C. (Z, p), and the system is approximately controllable. An explicit parameterization of all solutions 相似文献
We discuss the crossover of the form of the Cu Nuclear magnetic resonance (NMR) spin echo decay at the onset of Cu wipeout in lanthanum cuprates. Experimentally, the echo decay undergoes a crossover from Gaussian to exponential form below the temperature where the Cu NMR intensity drops. The wipeout and the change in behavior both arise because the nuclei experience spatially inhomogeneous spin fluctuations at low temperatures. We argue that regions where the spin fluctuations remain fast are localized on length scales of order 1-2 lattice spacings. The inhomogeneity is characterized by the local activation energy Ea(r); we estimate the functional form of Ea(r) for points where Ea>(r)∼0. 相似文献
Excited states in 59Zn were observed for the first time following the fusion-evaporation reaction 24Mg + 40Ca at a beam energy of 60 MeV. The GASP array in conjunction with the ISIS Silicon ball and the NeutronRing allowed for the
detection of γ-rays in coincidence with evaporated light particles. The mirror symmetry of 59Zn and 59Cu is discussed.
Received: 28 May 2002 / Accepted: 10 July 2002 / Published online: 3 December 2002
RID="a"
ID="a"Present address: Oliver Lodge Laboratory, University of Liverpool, P.O. Box 147, Liverpool, L69 7ZE, United Kingdom; e-mail: ca@ns.ph.liv.ac.uk.
RID="b"
ID="b"Present address: Physik-Departament, Technische Universit?t München, D-85748 Garching, Germany.
Communicated by W. Henning 相似文献
In the past ten years, nuclear chemists have made considerable progress in developing fast on-line separation techniques,
which allowed to chemically characterize the first four transactinide elements Rf (rutherfordium, Z = 104), Db (dubnium, Z = 105), Sg (seaborgium, Z = 106), and recently also Bh (bohrium, Z = 107). In all cases the isolated nuclides were unambiguously identified by observing genetically linked decay chains. Nuclides
with production cross-sections of less than 100 pb and half-lives as short as a few seconds have been chemically isolated.
Thus, chemists have discovered or significantly contributed to the characterization of the nuclear-decay properties of a number
of transactinide nuclei. New techniques with greatly improved overall efficiencies should allow chemists to extend their studies
to even heavier elements such as Hs (hassium, Z = 108) and to the recently discovered superheavy elements with Z = 112 and 114, which can be produced only with picobarn cross-sections.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: andreas.tuerler@psi.ch 相似文献
Let
be a locally compact topological groupoid, A and B two C*-algebras endowed with a continuous action of
. We define an operator K-theory group K K
(A,B). We describe two basic properties of this theory: the existence of a Kasparov product and functoriality with respect to groupoid cocycles. 相似文献
In univariate Padé approximation we learn from the Froissart phenomenon that Padé approximants to perturbed Taylor series exhibit almost cancelling pole–zero combinations that are unwanted. The location of these pole–zero doublets was recently characterized for rational functions by the so‐called Froissart polynomial. In this paper the occurrence of the Froissart phenomenon is explored for the first time in a multivariate setting. Several obvious questions arise. Which definition of Padé approximant is to be used? Which multivariate rational functions should be investigated? When considering univariate projections of these functions, our analysis confirms the univariate results obtained so far in [13], under the condition that the noise is added after projection. At the same time, it is apparent from section 4 that for the unprojected multivariate Froissart polynomial no conjecture can be formulated yet.
We consider the problem of the identification of continuous functionsf∶[0, 1]→R, by means of the sums
. This is not possible, in general, but we prove that it may be the case under auxiliary conditions. We also study the behaviour
of a well known exceptional function.
Sunto Consideriamo il problema dell’identificazione delle funzioni continuef:[0,1]→ →R, mediante le somme
. Ciò non è, in generale, possibile: dimostriamo però tale possibilità sotto condizioni ausiliarie. Studiamo inoltre il comportamento
di una ben nota funzione eccezionale.
Let m2(n,q), m2(n,q) be, respectively, the maximum value, the second largest value of k for which there exists a complete k-cap in PG(n,q). In this paper, the known upper bound on m2(3,q), q even, q 8, is improved. This new upper bound on m2(3,q) is then used to improve the upper bounds on m2(n,q), q even, q 8 and n 4. 相似文献