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91.
92.
B. Metsch 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):275-280
The scope of a relativistically covariant constituent quark model of baryons based on the Bethe-Salpeter equation in instantaneous
approximation is illustrated by a discussion of various baryon resonance observables such as static electromagnetic moments
--including a novel calculational procedure-- form factors and helicity amplitudes, semileptonic decays as well as the systematics
of two-body strong decay widths. 相似文献
93.
In this paper we consider a nonlocal evolution equation in one dimension, which describes the dynamics of a ferromagnetic system in the mean field approximation. In the presence of a small magnetic field, it admits two stationary and homogeneous solutions, representing the stable and metastable phases of the physical system. We prove the existence of an invariant, one dimensional manifold connecting the stable and metastable phases. This is the unstable manifold of a distinguished, spatially nonhomogeneous, stationary solution, called the critical droplet.(4, 10) We show that the points on the manifold are droplets longer or shorter than the critical one, and that their motion is very slow in agreement with the theory of metastable patterns. We also obtain a new proof of the existence of the critical droplet, which is supplied with a local uniqueness result. 相似文献
94.
M. Rashdan 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):371-379
The use of elastic proton scattering at intermediate and high energies to obtain information about the density distributions
of unstable nuclei is investigated. A comparison between the relativistic impulse approximation (RIA) and Glauber model for
proton scattering from 16O, 40Ca, 44Ca and 48Ca at medium energies is performed. We used density distributions derived from the relativistic mean-field theory, employing
the recent relativistic force NL-RA1, as well as experimental and phenomenological densities. It is found that the eikonal
approximation can describe the cross-section only at small scattering angles and is weakly sensitive to the density distributions,
while the RIA nicely produced the experimental cross-sections, even at medium and larger angles, and was very sensitive to
the nuclear densities. Furthermore, the RIA better describes the isospin dependence of the cross-section. We used the RIA
to investigate the density distribution of 58Ca for proton scattering at different energies. It is found that the cross-section strongly depends on the parameters of the
density distribution even at a small scattering angle. These results are important in extracting information about the structure
of unstable nuclei. We also investigated the RIA and its sensitivity in describing halo nuclei such as 6He. We used for 6He a no-halo Gaussian density and a realistic-halo density that derived in the cluster orbital shell model approximation and
contains the extended distribution of the valence nucleons. Comparison with the recent experimental data at GSI at 717 MeV/nucleon
shows that the RIA successfully described the data at all considered range of the momentum transfer and on the other hand
favor the halo structure of 6He.
Received: 1 December 2001 / Accepted: 31 July 2002 / Published online: 11 February 2003
RID="a"
ID="a"e-mail: mrashdan@hotmail.com
Communicated by P. Schuck 相似文献
95.
We consider two-parameter families of C
r-smooth, r6, two-dimensional area-preserving diffeomorphisms that have structurally unstable simplest heteroclinic cycles. We find the conditions when diffeomorphisms under consideration possess infinitely many periodic generic elliptic points and elliptic islands. 相似文献
96.
The space–time translation property of a stable particle is characterized by a time-like Lorentz vector (E,
k
). We show in this contribution that unstable particles are, in addition, characterized by a space-like Lorentz 4-vector of uncertainties, or spreads, ( E,
k). This is true for unstable states created in formation-, in production-, and in decay-experiments. The space-like nature of the spread vector causes a nonzero momentum spread to be present in all Lorentz frames so that there is no Lorentz frame in which the unstable particle is entirely at rest. With the space-like spreadvector ( E,
k) in addition to the time-like (E,
k
), also the rotation property of an unstable particle is affected, and unstable states have an uncertainty in their spin. This means neighboring spin states are occupied in addition to the original spin. Experiments are discussed that show a principal limitation of the accuracy of spin measurement from finite lifetimes. Wave functions for unstable particles are discussed, and we show in the example of a short-lived spin-0 state that the appearance of a spin neighbor in the amplitude is proportional to the inverse lifetime. 相似文献
97.
SUN Peng CHEN Shi-Gang WANG Guang-Rui 《理论物理通讯》2006,46(6):1074-1080
The time behaviors of intermittent turbulence in Gledzer-Ohkitani-Yamada model are investigated. Two kinds of orbits of each shell which is in the inertial range are discussed by portrait analysis in phase space. We find intermittent orbit parts wandering randomly and the directions of unstable quasi-periodic orbit parts of different shells form rotational, reversal and locked cascade of period three with shell number. We calculate the critical scaling of intermittent turbulence and the extended self-similarity of the two parts of orbit and point out that nonlinear scaling in inertial-range is decided by intermittent orbit parts. 相似文献
98.
用数值积分方法求解了在圆柱坐标中的横向多模菲涅尔(Fresnel)积分方程.在初始复数光场振幅取均匀分布和随机分布的条件下对圆形球面共焦腔、稳定腔和平面腔的TEMn0模进行了计算分析.计算结果表明,球面腔单一模的数值结果同解析解的结果符合较好,多种模同时存在时的结果不仅符合多模空间分布特性而且其基模是主要的. 相似文献
99.
The unstable nonlinear Schrodinger (NLS) equation is solved by the inverse scattering transform. Based on the constructed Zakharov-Shabat equation, it is shown that the soliton solution of the unstable NLS equation can be known from the soliton solution of the usual NLS equation by simply exchanging the tariables. The explicit N-soliton solution and the position shifts due to the collision are thus calculated. 相似文献
100.
A detailed study of the classical and quantum mechanics of a free particle on a double cone and a particle bound to its tip by a harmonic oscillator potential is presented. 相似文献