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391.
T.?N.?LeiteEmail author N.?Teruya 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):369-374
The structure of the isovector dipole resonance in neutron-rich calcium isotope, 60Ca, has been investigated by implementing a careful treatment of the differences of neutron and proton radii in the continuum random phase approximation (RPA). The calculations have taken into account the current estimates of the neutron skin. The estimates of the escape widths for direct neutron decay from the pygmy-dipole resonance (PDR) were shown rather wide, implicating a strong coupling to the continuum. The width of the giant-dipole resonance (GDR) was evaluated, bringing on a detailed discussion about its microscopic structure.Received: 22 September 2003, Revised: 9 February 2004, Published online: 7 September 2004PACS:
21.10.Pc Single-particle levels and strength functions - 21.60.-n Nuclear structure models and methods - 24.30.Cz Giant resonances - 24.30.Gd Other resonances 相似文献
392.
J.?Milton Pereira Jr.Email author R.?N.?Costa Filho 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,40(2):137-144
A microscopic model is employed to calculate the spectrum of dipole-exchange spin waves in multilayers in which thin ferromagnetic films are separated by non-magnetic spacers. Two configurations are considered: in one the films have magnetizations parallel to each other, in the other the magnetizations are antiparallel. The calculations extend a previous microscopic formalism that allows the calculation of the dipole-exchange spin wave spectrum in thin films. The results show the splitting of the frequency bands and the mode mixing caused by the dipolar interaction between the films as a function of spacer thickness.Received: 26 May 2004, Published online: 12 August 2004PACS:
75.30.Ds Spin waves - 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.) - 75.70.-i Magnetic properties of thin films, surfaces, and interfaces 相似文献
393.
M.?W.?Mancini A.?R.?L.?Caires G.?D.?Telles V.?S.?Bagnato L.?G.?MarcassaEmail author 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,30(1):105-116
In this paper we review the present status on heteronuclear trap loss rate (
) for alkali mixtures held in a magneto-optical trap (Na-K, Na-Rb, Na-Cs, K-Rb, Rb-Cs, Li-Cs). The intensity dependence of the
for the mixture Cs-K is also presented for the first time in this report. The measurement techniques and a semiclassical model, considering both excited-ground and doubly excited channels, are reviewed. The comparison between the model and the experimental results indicates that radiative escape may be the dominant loss process for heteronuclear cold collisions. The obtained values for the crossed species trap loss indicate possibilities of future experiments involving such mixtures in a two species condensate.Received: 19 January 2004, Published online: 11 May 2004PACS:
32.80.Pj Optical cooling of atoms; trapping - 33.80.Ps Optical cooling of molecules; trapping - 34.50.Rk Laser-modified scattering and reactions 相似文献
394.
I.?Iga M.-T.?Lee P.?Rawat L.?M.?BrescansinEmail author L.?E.?Machado 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,31(1):45-51
We present a joint theoretical-experimental study on electron scattering by C2H2 in the intermediate energy range. We report calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross-sections at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross-sections are reported in the (50-500)-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. The iterative Schwinger variational method, combined with the distorted-wave approximation, is used to solve the scattering equations. Experimentally, the angular distributions of the scattered electrons are converted to absolute cross-sections using the relative flow technique. The comparison of our calculated with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.Received: 26 August 2004, Published online: 5 October 2004PACS:
34.80.Bm Elastic scattering of electrons by atoms and molecules 相似文献
395.
Hermano?FridEmail author Mikhail?Perepelitsa 《Communications in Mathematical Physics》2004,250(2):335-370
We consider the initial value problem, with periodic initial data, for the Euler equations in relativistic isentropic gas dynamics, for ideal polytropic gases which obey a constitutive equation, relating pressure p and density , p=2, with 1, 0<<c, where c is the speed of light. Global existence of periodic entropy solutions for initial data sufficiently close to a constant state follows from a celebrated result of Glimm and Lax (1970). We prove that given any periodic initial data of locally bounded total variation, satisfying the physical restrictions ||v0||<c, where v is the gas velocity, there exists a globally defined spatially periodic entropy solution for the Cauchy problem, if 1<0, for some 0>1, depending on the initial bounds. The solution decays in Lloc1 to its mean value as t. 相似文献
396.
Adilson?Elias?Xavieroliveira@cos.ufrj.br" title="adilson@cos.ufrj.br oliveira@cos.ufrj.br" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author Antonio?Alberto?Fernandes?De?Oliveira 《Journal of Global Optimization》2005,31(3):493-504
We consider the problem of optimally covering plane domains by a given number of circles. The mathematical modeling of this problem leads to a min–max–min formulation which, in addition to its intrinsic multi-level nature, has the significant characteristic of being non-differentiable. In order to overcome these difficulties, we have developed a smoothing strategy using a special class C∞ smoothing function. The final solution is obtained by solving a sequence of differentiable subproblems which gradually approach the original problem. The use of this technique, called Hyperbolic Smoothing, allows the main difficulties presented by the original problem to be overcome. A simplified algorithm containing only the essential of the method is presented. For the purpose of illustrating both the actual working and the potentialities of the method, a set of computational results is presented. 相似文献
397.
A.?A.?BytsenkoEmail author M.?E.?X.?Guimar?es V.?S.?Mendes 《The European Physical Journal C - Particles and Fields》2005,39(2):249-252
We consider gauge theories based on abelian p-forms on real compact hyperbolic spaces. Using the zeta-function regularization method and the trace tensor kernel formula, we determine explicitly an expression for the vacuum energy (Casimir energy) corresponding to skew-symmetric tensor fields. It is shown that the topological component of the Casimir energy for co-exact forms on even-dimensional spaces, associated with the trivial character, is always negative. We infer on the possible cosmological consequences of this result.Received: 14 September 2004, Revised: 14 November 2004, Published online: 23 December 2004PACS:
04.70.Dy, 11.25.Mj 相似文献
398.
S.?AzevedoEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(2):203-207
The stability and electronic structure of BC2N compounds are studied using first-principle calculations. The investigated structures have the topology of graphite layers with either carbon, nitrogen or boron atoms at each site. The calculations show that stabler structures are obtained by increasing the number of C-C and B-N bonds. On the other hand, less stable structures result from increasing the number of N-N and B-B bonds. The energy gap of the stablest compounds varies from 0.0 to 1.62 eV, depending on the distribution of B, C, and N atoms in the unit cell. The electronic properties of BC2N layered materials strongly depend on their atomic arrangements. The observed changes in energy gaps do not simply follow a symmetry-based argument proposed earlier. 相似文献
399.
M.?C.?B.?AbdallaEmail author A.?A.?Bytsenko M.?E.?X.?Guimar?es 《The European Physical Journal C - Particles and Fields》2005,44(4):607-612
There is a remarkable connection between the number of quantum states of conformal theories and the sequence of dimensions
of Lie algebras. In this paper, we explore this connection by computing the asymptotic expansion of the elliptic genus and
the microscopic entropy of black holes associated with (supersymmetric) sigma models. The new features of these results are
the appearance of correct prefactors in the state density expansion and in the coefficient of the logarithmic correction to
the entropy.
Received: 25 May 2005, Revised: 24 August 2005, Published online: 11 October 2005 相似文献
400.
D.?M.?GitmanEmail author P.?Yu.?Moshin J.?L.?Tomazelli 《The European Physical Journal C - Particles and Fields》2005,44(4):591-598
We propose a natural extension of the BRST-antiBRST superfield covariant scheme in general coordinates. Thus, the coordinate
dependence of the basic tensor fields and scalar density of the formalism is extended from the base supermanifold to the complete
set of superfield variables.
Received: 23 June 2005, Revised: 18 July 2005, Published online: 6 October 2005 相似文献