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971.
A.N. Ivanov H. Oberhummer N.I. Troitskaya M. Faber 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):519-535
The Nambu–Jona–Lasinio model of the deuteron suggested by Nambu and Jona–Lasinio (Phys. Rev. 124 (1961) 246) is formulated
from the first principles of QCD. The deuteron appears as a neutron–proton collective excitation, i.e. a Cooper np–pair, induced
by a phenomenological local four–nucleon interaction in the nuclear phase of QCD. The model describes the deuteron coupled
to itself, nucleons and other particles through one–nucleon loop exchanges providing a minimal transfer of nucleon flavours
from initial to final nuclear states and accounting for contributions of nucleon–loop anomalies which are completely determined
by one–nucleon loop diagrams. The dominance of contributions of nucleon–loop anomalies to effective Lagrangians of low–energy
nuclear interactions is justified in the large N
C expansion, where N
C is the number of quark colours.
Received: 10 March 2000 相似文献
972.
S. Residori E. Pampaloni P.K. Buah-Bassuah F.T. Arecchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):331-334
As a drop of fluid is deposited on the surface of a miscible fluid (that we call the solvent), it undergoes a strong pulling
due to its surface rupture and it acquires a kinetic energy independently of gravity. For the drop and the solvent being of
the same fluid we observe a drop injection at an initial velocity which scales as the square root of the surface tension of
the drop against air. Once injected, the drop develops a transverse instability giving rise to an expanding ring. Viscosity
terminates the process and stops the ring. We show that the final ring height follows a scaling law whereas two asymptotical
scaling regimes can be identified for the ring radius.
Received 31 August 1999 相似文献
973.
F. Lillo R.N. Mantegna 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(4):603-606
We select the n stocks traded in the New York Stock Exchange and we form a statistical ensemble of daily stock returns for each of the k trading days of our database from the stock price time series. We study the ensemble return distribution for each trading
day and we find that the symmetry properties of the ensemble return distribution drastically change in crash and rally days
of the market. In crash and rally days, the distribution becomes asymmetric. In particular for crashes the positive tail is
steeper than the negative one whereas the reverse is observed in rally days.
Received 25 February 2000 相似文献
974.
C. Foin A. Gizon D. Barnéoud J. Genevey J. Gizon D. Santos F. Farget P. Paris C. F. Liang D. Bucurescu A. Płochocki 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):451-454
The decay of the T
1/2 = 420 ns isomer in 151Er has been reinvestigated. The multipolarities of the decaying transitions have been established by measuring the electron
conversion coefficients. An I
π
= 67/2− assignment is proposed for this isomer with a π[h
112/4
d
32/1
d
52/−1]⊗ν[f
7/2
h
9/2
h
112/−1] configuration. 相似文献
975.
V. Da Costa Y. Henry F. Bardou M. Romeo K. Ounadjela 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):297-303
Tiny spatial fluctuations of tunnel barrier parameters are shown to have dramatic consequences on the statistical properties
of quantum tunneling. A direct experimental evidence is provided that the tunnel current through metal-oxide junctions, imaged
at a nanometric scale, exhibits broad statistical distributions extending over more than 4 orders of magnitude. Striking effects
of broad current distributions are shown: the total tunnel transmission is dominated by few highly transmitting sites and
the typical current density varies strongly with the size of the junction. Moreover, self-averaging of the tunnel current
fluctuations occurs only for unexpectedly large junction areas.
Received 1 April 1999 相似文献
976.
D. Beck F. Ames G. Audi G. Bollen F. Herfurth H. -J. Kluge A. Kohl M. König D. Lunney I. Martel R. B. Moore H. Raimbault-Hartmann E. Schark S. Schwarz M. de Saint Simon J. Szerypo 《The European Physical Journal A - Hadrons and Nuclei》2000,8(3):307-329
Direct mass measurements of neutron-deficient rare-earth isotopes in the vicinity of 146Gd were performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. This paper reports on the measurement of
more than 40 isotopes of the elements praseodymium, neodymium, promethium, samarium, europium, dysprosium and holmium, that
have been measured with a typical accuracy of
m
14 keV. An atomic mass evaluation has been performed taking into account other experimental mass values via a least-squares
adjustment. The results of the adjustment are discussed.
Received: 18 April 2000 / Accepted: 12 July 2000 相似文献
977.
We study irreversible A-B reaction kinetics at a fixed interface separating two immiscible bulk phases, A and B. Coupled equations
are derived for the hierarchy of many-body correlation functions. Postulating physically motivated bounds, closed equations
result without the need for ad hoc decoupling approximations. We consider general dynamical exponent z, where is the rms diffusion distance after time t. At short times the number of reactions per unit area, , is 2nd order in the far-field reactant densities . For spatial dimensions dabove a critical value , simple mean field (MF) kinetics pertain, where Qb is the local reactivity. For low dimensions , this MF regime is followed by 2nd order diffusion controlled (DC) kinetics, , provided . Logarithmic corrections arise in marginal cases. At long times, a cross-over to 1st order DC kinetics occurs: . A density depletion hole grows on the more dilute A side. In the symmetric case (), when the long time decay of the interfacial reactant density, , is determined by fluctuations in the initial reactant distribution, giving . Correspondingly, A-rich and B-rich regions develop at the interface analogously to the segregation effects established by
other authors for the bulk reaction . For fluctuations are unimportant: local mean field theory applies at the interface (joint density distribution approximating
the product of A and B densities) and . We apply our results to simple molecules (Fickian diffusion, z=2) and to several models of short-time polymer diffusion (z>2).
Received 8 June 1998 and Received in final form 10 September 1999 相似文献
978.
S.A. Starostin I.V. Kochetov P.J.M. Peters Y.B. Udalov W.J. Witteman A.P. Napartovich 《Applied physics. B, Lasers and optics》2000,71(4):491-494
The performance of a RF excited cw atomic xenon laser at wavelengths of 2.03 μm and 2.65 μm was studied theoretically and
experimentally as a function of electrode distance. Results for inter-electrode distances from 2 to 0.25 mm are presented.
A high pumping rate resulted in strong 40 mW cw amplified spontaneous emission at 2.65 μm wavelength from the configuration
with the smallest distance of 0.25 mm between the electrodes. The maximum laser output of 2.7 W (0.24 W/cm3) was obtained with an active medium volume of 2×15×370 mm3 whereas the maximum specific output of 1.9 W/cm3 was received for an active medium volume of 0.25×2.25×370 mm3. A fluid model of the RF discharge was developed to analyze the laser behavior for different distances between the electrodes.
Received: 30 November 1999 / Revised version: 21 April 2000 / Published online: 6 September 2000 相似文献
979.
M.M. Bülbül S.R.P. Smith B. Obradovic T.S. Cheng C.T. Foxon 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):423-429
We report on Raman scattering measurements of all Raman-active phonons in wurtzite and zinc blende structure GaN epilayers
grown on GaAs (001), GaAs (111)A, and GaAs (111)B oriented substrates by means of molecular beam epitaxy (MBE). Raman spectra
are taken from these epilayers at room temperature and 77 K in backscattering geometry. The measured values of the phonon
frequencies are in agreement with other studies and with lattice dynamic calculations of phonon modes in GaN zinc blende and
wurtzite structures. We show that crystal quality is much better in samples grown on GaAs (111) substrates than in samples
grown on GaAs (001) substrates. The observation of disorder-activated modes gives information about sample quality. Comparison
of the spectra from different thickness epilayers shows that the GaN is more highly disordered close to the substrate, particularly
for the (001) substrates.
Received 16 July 1999 相似文献
980.
J. Hüfner Y.B. He B.Z. Kopeliovich 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):239-244
Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus
collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states
while the nuclei still overlap. The spectra and mean number <n
g> of the prompt gluons are calculated perturbatively and the inelastic cross section σabs
Ψg is estimated. The integrated cross sections σ(A B →J/ψX) for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with
some adjustment of one parameter <n
g>σabs
Ψg.
Received: 20 August 1999 相似文献