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51.
The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window. 相似文献
52.
We show that there exist relatively small subsemigroupsM ofβℕ with the property that ifp+q andq+p are inM then bothp andq are inM + ℤ. We also show that it is consistent with the usual axioms of set theory that there is some idempotent e inβℕ such that ifp+q=e, then bothp andq are ine + ℤ.
The first author acknowledges support received from the National Science Foundation (USA) via grant DMS90-25025. 相似文献
53.
On interpolation with products of positive definite functions 总被引:1,自引:0,他引:1
Hans Strauss 《Numerical Algorithms》1997,15(2):153-165
In this paper we consider the problem of scattered data interpolation for multivariate functions. In order to solve this problem, linear combinations of products of positive definite kernel functions are used. The theory of reproducing kernels is applied. In particular, it follows from this theory that the interpolating functions are solutions of some varational problems. 相似文献
54.
We discuss some of the experimental motivation for the need for semigroup decay laws and the quantum Lax-Phillips theory of scattering and unstable systems. In this framework, the decay of an unstable system is described by a semigroup. The spectrum of the generator of the semigroup corresponds to the singularities of the Lax-Phillips S-matrix. In the case of discrete (complex) spectrum of the generator of the semigroup, associated with resonances, the decay law is exactly exponential. The states corresponding to these resonances (eigenfunctions of the generator of the semigroup) lie in the Lax-Phillips Hilbert space, and, therefore, all physical properties of the resonant states can be computed. We show that the parametrized relativistic quantum theory is a natural setting for the realization of the Lax-Phillips theory. 相似文献
55.
We study a simplified mean field model of superconductor dynamics in the
presence of impurities or for variable superconductor depth. This model is
given by the gradient-flow version of the Ginzburg-Landau equations
(Gorkov-Eliashberg equations) with an addition of a potential term. We find
a dynamical law of motion of the vortex center, involving the potential, such
that for datum close to a (static) magnetic vortex the solution
is close, for all times, to a magnetic vortex whose center obeys this law. 相似文献
56.
57.
P. Darriulat P. Dittmann K. Eggert M. Holder K.T. McDonald T. Modis F.L. Navarria A. Seiden J. Strauss G. Vesztergombi E.G.H. Williams 《Nuclear Physics B》1976,107(3):429-456
We present a study of the final state structure in proton-proton collisions (√s = 53 GeV) where a large transverse momentum π0 (pt > 2 GeV/c) is produced at an angle of 90°. Charged secondaries have been detected and momentum analysed in the split field magnet detector at the CERN Intersecting Storage Rings. The large angular coverage of this detector extends over ±2.5 units of rapidity and ±30° of azimuth with respect to the trigger π0, both towards and away from it. In each of these directions, where we observe similar strong correlations, we present charged particle distributions, in rapidity and momentum. In the hemisphere containing the trigger π0 we have measured the cross section for inclusive production of large transverse momentum ?± mesons. In the opposite hemisphere the data exhibit several features predicted by hard scattering quark-parton models: coplanarity and short-range rapidity correlation for the large transverse momentum secondaries as well as a transverse momentum sharing distribution similar to that observed in deep inelastic electro-production and in e+e? collisions. 相似文献
58.
H. Strauss 《Numerische Mathematik》1984,44(3):337-347
Summary This paper deals with quadrature formulae of Gauss type corresponding to subspaces of spline functionsS
m–1, k
of degreem–1 withk fixed knots. We shall show monotonicity of the quadrature formulae for functions which are contained in the so-called convexity cone ofS
m–1,k
Moreover, we apply these results to monosplines and establish comparison theorems for these splines. 相似文献
59.
Anthony L Fitzhugh Richard S Strauss Elizabeth N Brewer Steven D Glassman Maitland Jones 《Tetrahedron letters》1985,26(33):3911-3914
Oxalacetic esters undergo ester exchange at 120°C, at which temperature loss of CO does not occur. A new mechanism is proposed for the decarbonmonoxylation reaction. 相似文献
60.
Necessary and sufficient conditions for uniqueness of analytic continuation are investigated for a system of m ? 1 first-order linear homogeneous partial differential equations in one unknown, with complex-valued ∞ coefficients, in some connected open subset of k, k ? 2. The type of system considered is one for which there exists a real k-dimensional, ∞, connected C-R submanifold Mk of n, for k, n ? 2, such that the system may be identified with the induced Cauchy-Riemann operators on Mk. The question of uniqueness of analytic continuation for a system of partial differential equations is thus transformed to the question of uniqueness of analytic continuation for C-R functions on the manifold Mk ? Cn. Under the assumption that the Levi algebra of Mk has constant dimension, it is shown that if the excess dimension of this algebra is maximal at every point, then Mk has the property of uniqueness of analytic continuation for its C-R functions. Conversely, under certain mild conditions, it is shown that if Mk has the property of uniqueness of analytic continuation for all ∞ C-R functions, and if the Levi algebra has constant dimension on all of Mk, then the excess dimension must be maximal at every point of Mk. 相似文献