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991.
I.?Weymann J.?Barna?Email author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(2):289-299
Spin-dependent electronic transport through a quantum
dot has been analyzed theoretically in the cotunneling regime by
means of the second-order perturbation theory. The system is
described by the impurity Anderson Hamiltonian with arbitrary
Coulomb correlation parameter U. It is assumed that the dot
level is intrinsically spin-split due to an effective molecular
field exerted by a magnetic substrate. The dot is coupled to two
ferromagnetic leads whose magnetic moments are noncollinear. The
angular dependence of electric current, tunnel magnetoresistance,
and differential conductance are presented and discussed. The
evolution of a cotunneling gap with the angle between magnetic
moments and with the splitting of the dot level is also
demonstrated. 相似文献
992.
M.?BortzEmail author F.?G?hmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(3):399-408
We numerically evaluate certain multiple integrals representing nearest and next-nearest neighbor correlation functions of the spin-1/2 XXZ Heisenberg infinite chain at finite temperatures. 相似文献
993.
Zhi-Jie?QinEmail author Shi-Jie?Xiong 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(3):325-329
We investigate localization behavior of quasiparticles in
disordered multi-plane superconductors with s-wave pairing. By
introducing disorder with random site energies, the spatial
fluctuations of Bogoliubov-de Gennes pairing potential are
self-consistently determined. The size dependence of rescaled
localization length for a long bar is calculated by using the
transfer-matrix method. From the finite-size scaling analysis we
show that there exists a critical point of the disorder strength
Wc which separates the extended and localized quasiparticle
states in such quasi-two-dimensional systems. The associated
critical behavior is studied and the relationship of the results
to the number of planes is discussed. 相似文献
994.
Linfeng?YangEmail author Jiangwei?Chen Huatong?Yang Jinming?Dong 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(3):399-403
We have calculated the quantum conductance of single-walled
carbon nanotube (SWNT) waveguide by using a tight binding-based
Greens function approach. Our calculations show that the slow
conductance oscillations as well as the fast conductance
oscillations are manifestations of the intrinsic quantum
interference properties of the conducting SWNTs, being independent
of the defect and disorder of the SWNTs. And zigzag type tubes do
not show the slow oscillations. The SWNT electron waveguide is
also found to have distinctly different transport behavior
depending on whether or not the length of the tube is commensurate
with a (3N+1) rule, with N the number of basic carbon repeat
units along the nanotube length. 相似文献
995.
M. A.?Mu?ozEmail author F?de los Santos M M?Telo da Gama 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(1):73-79
A beautifully simple model introduced a couple of decades ago, Tooms
cellular automaton, revealed that non-equilibrium systems may exhibit
generic bistability, i.e. two-phase coexistence over a finite area of
the (two-dimensional) phase diagram, in violation of the equilibrium
Gibbs phase rule. In this paper we analyse two interfacial models,
describing more realistic situations, that share with Tooms model a
phase diagram with a broad region of phase coexistence.
An analysis of the interfacial models yields conditions for generic
bistability in terms of physically relevant parameters that may be
controlled experimentally. 相似文献
996.
L?da Fontoura Costa G.?TraviesoEmail author C. A.?Ruggiero 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(1):119-128
This article investigates the functional properties of complex
networks used as grid computing systems. Complex networks following
the Erdös-Rényi model and other models with a preferential
attachment rule (with and without growth) or priority to the
connection of isolated nodes are studied. Regular networks are also
considered for comparison. The processing load of the parallel
program executed on the grid is assigned to the nodes on demand, and
the efficiency of the overall computation is quantified in terms of
the parallel speedup. It is found that networks with preferential
attachment allow lower computing efficiency than networks with
uniform link attachment. At the same time, considering only node
clusters of the same size, preferential attachment networks display
better efficiencies. The regular networks, on the other hand,
display a poor efficiency, due to their implied larger internode
distances. A correlation is observed between the topological
properties of the network, specially average cluster size, and their
respective computing efficiency. 相似文献
997.
Shun?Zhou Zhi-zhong?XingEmail author 《The European Physical Journal C - Particles and Fields》2005,38(4):495-510
We present a systematic study of 400 combinations of the charged lepton and neutrino mass matrices with six vanishing entries or texture zeros. Only 24 of them, which can be classified into a few distinct categories, are found to be compatible with current neutrino oscillation data at the
level. A peculiar feature of the lepton mass matrices in each category is that they have the same phenomenological consequences. Taking account of a simple seesaw scenario for six parallel patterns of the charged lepton and Dirac neutrino mass matrices with six zeros, we show that it is possible to fit the experimental data at or below the
level. In particular, the maximal atmospheric neutrino mixing can be reconciled with a strong neutrino mass hierarchy in the seesaw case. Numerical predictions are also obtained for the neutrino mass spectrum, flavor mixing angles, CP-violating phases and effective masses of the tritium beta decay and the neutrinoless double beta decay.Received: 28 September 2004, Revised: 14 October 2004, Published online: 1 December 2004PACS:
12.15.Ff, 12.10.Kt 相似文献
998.
T.?Sj?strandEmail author P.?Z.?Skands 《The European Physical Journal C - Particles and Fields》2005,39(2):129-154
We propose a sophisticated framework for high-energy hadronic collisions, wherein different QCD physics processes are interleaved in a common sequence of falling transverse-momentum values. Thereby phase-space competition is introduced between multiple parton-parton interactions and initial-state radiation. As a first step we develop new transverse-momentum-ordered showers for initial- and final-state radiation, which should be of use also beyond the scope of the current article. These showers are then applied in the context of multiple interactions, and a few tests of the new model are presented. The article concludes with an outlook on further aspects, such as the possibility of a shower branching giving partons participating in two different interactions.Received: 26 August 2004, Revised: 14 October 2004, Published online: 11 January 2005 相似文献
999.
P.?C.?BrunsEmail author U.-G.?Mei?ner 《The European Physical Journal C - Particles and Fields》2005,40(1):97-119
We extend the method of infrared regularization to spin-1 fields. As applications, we discuss the chiral extrapolation of the rho meson mass from lattice QCD data and the pion-rho sigma term.Received: 18 November 2004, Published online: 4 February 2005PACS:
12.39.Fe, 12.38.GcWork supported in part by Deutsche Forschungsgemeinschaft through grants provided for the SFB/TR 16 Subnuclear Structure of Matter. 相似文献
1000.
G.?Kl?mkeEmail author K.?M?nig 《The European Physical Journal C - Particles and Fields》2005,42(3):261-270
A Monte-Carlo analysis on production and decay of supersymmetric charginos at a future photon-collider is presented. A photon collider offers the possibility of a direct branching-ratio measurement. In this study, the process
has been considered for a specific mSUGRA scenario. Various backgrounds and a parameterised detector simulation have been included. Depending on the centre-of-mass energy, a statistical error for the directly measurable branching ratio BR(
) of up to 3.5% can be reached.Received: 14 March 2005, Revised: 31 May 2005, Published online: 28 June 2005G. Klämke: Now at: Institut für Theoretische Physik, Universität Karlsruhe, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany 相似文献