共查询到20条相似文献,搜索用时 640 毫秒
1.
V. Korepin N. Slavnov 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):555-557
We discovered a simple quadratic equation, which relates scattering phases of particles on Fermi surface. We consider one-dimensional
Bose gas and XXZ Heisenberg quantum spin chain.
Received: 4 December 1997 / Accepted: 17 March 1998 相似文献
2.
H. Lambaré P. Roche S. Balibar H.J. Maris O.A. Andreeva C. Guthmann K.O. Keshishev E. Rolley 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):381-391
We have studied the nucleation of bubbles in pure superfluid helium-4 at temperatures down to 65 mK. We have found that the
nucleation is a stochastic process, and that at temperatures below 600 mK the nucleation rate is independent of temperature.
These results are consistent with the assumption that the nucleation takes place via quantum tunneling.
Received: 15 November 1997 / Received in final form: 19 December 1997 / Accepted: 22 January 1998 相似文献
3.
M. Goldman 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):147-156
We describe the theory of EPR in a crystal field multiplet under sample spinning. Berry phases arise because the crystal field
is of lower symmetry than the full rotation group. The formal development is limited to pure J multiplets, crystal field doublets, and field and rotation axes parallel to a principal axis.
Received: 4 August 1997 / Received in final form: 19 December 1997 /
Accepted: 28 January 1998 相似文献
4.
M. Geoghegan F. Boué G. Bacri A. Menelle D.G. Bucknall 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):83-96
We have used neutron reflectometry to measure interfacial widths between two polystyrene films, where either one or both films
are crosslinked. The observed interfacial width between two networks is larger than the size expected for “dangling ends”,
which suggests motion of heterogeneous regions of the networks. In the case when one of the networks is replaced by a linear
polymer, the interfacial profile can be asymmetric with a diffusion “front” of linear polymer penetrating the network to a
length scale of up to 200 ?. In the case of a more densely crosslinked network and a high molecular weight linear polymer
the interface is symmetric implying negligible penetration.
Received: 4 December 1996 / Revised: 13 October 1997 / Accepted: 23 December 1997 相似文献
5.
We show how Fermi liquid theory results can be systematically recovered using a renormalization group (RG) approach. Considering
a two-dimensional system with a circular Fermi surface, we derive RG equations at one-loop order for the two-particle vertex
function in the limit of small momentum () and energy () transfer and obtain the equation which determines the collective modes of a Fermi liquid. The density-density response function
is also calculated. The Landau function (or, equivalently, the Landau parameters F
l
s
and F
l
a
) is determined by the fixed point value of the -limit of the two-particle vertex function (). We show how the results obtained at one-loop order can be extended to all orders in a loop expansion. Calculating the quasi-particle
life-time and renormalization factor at two-loop order, we reproduce the results obtained from two-dimensional bosonization
or Ward Identities. We discuss the zero-temperature limit of the RG equations and the difference between the Field Theory
and the Kadanoff-Wilson formulations of the RG. We point out the importance of n-body () interactions in the latter.
Received: 27 June 1997 / Received in final form: 17 December 1997 / Accepted: 26 January 1998 相似文献
6.
Y. Zhang G. Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):253-256
The transient process of globally coupled bistable systems from an unstable state to metastable state (i.e, quenching process) is studied analytically for small noise intensity. The influences of noise intensity and system size
on the system evolution are investigated. The problem of a large number of coupled Langevin equations is reduced to a simple
problem of a one-dimensional ordinary differential equation, subject to a white noise with intensity explicitly given. The
analytical results are fully confirmed by direct numerical computations.
Received: 3 July 1997 / Revised: 4 December 1997 / Accepted: 15 January 1998 相似文献
7.
E. Marinari G. Parisi D. Rossetti 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):495-500
We study the dynamical behavior of the Sherrington Kirkpatrick model. Thanks to the APE supercomputer we are able to analyze
large lattice volumes, and to investigate the low T region. We present a new and precise determination of the remnant magnetization and of its time decay exponent, of the energy
time decay exponent, and we discuss aging phenomena in the model. We exclude validity of naive aging, and propose different
options that fit the numerical data.
Received: 14 August 1997 / Revised: 2 December 1997 / Accepted: 30 January 1998 相似文献
8.
A. Saint-Jalmes F. Gallet 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):489-494
Above a surface pressure threshold , we detect a buckled state in the low temperature solid phase of a phospholipid monolayer spread at the air-formamide interface.
Stable ripples are observed with a Brewster angle microscope, and light scattering provides measurements mNm-1, wavelength m and amplitude of a few nm for the deformation. A model, coupling the monolayer thickness and elongation, and consistent with the monolayer
texture, is also presented.
Received: 18 August 1997 / Revised: 9 December 1997 / Accepted: 29 January 1998 相似文献
9.
D. Monier L. Fruchter 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):143-148
We have studied the occurrence of magnetothermal instabilities in a single crystal during field sweep magnetization experiments, equivalent to short time relaxation studies. We find instability
behaviour in good agreement with a recent model by Mints, for a non-linear E(J) characteristic. In particular, we find that a decrease of the dynamic relaxation rate, characterizing the effective activation
energy, precedes the unstable regime. We point out formal analogies between such instabilities and the general predictions
for flux avalanches.
Received: 11 December 1997 / Revised: 15 January 1998 / Accepted: 31 March 1998 相似文献
10.
Calculation of dielectronic recombination cross sections and rate coefficients for heliumlike carbon
J.-G. Wang T.-Q. Chang Y.-Z. Qu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):231-235
A simplified relativistic configuration interaction method is used to calculate the dielectronic recombination cross sections
and rate coefficients for heliumlike carbon. In this method, the infinite resonant doubly excited states can be treated conveniently
in the frame of Quantum Defect Theory. Our calculated cross sections are in agreements with the experimental measurements
except for the 1s2lnl'(n=6,7) resonances. The total energy-integrated cross sections and rate coefficients over all dielectronic resonances are in
agreements with the experimental measurements within percent.
Received: 7 July 1997 / Revised: 7 October 1997 / Accepted: 8 December 1997 相似文献
11.
E. Plaut R. Ribotta 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):265-281
We study theoretically the formation of convection patterns in a laterally extended planar nematic layer heated from below,
in the linear and weakly nonlinear regimes. By reformulating the viscous coupling terms of the basic nematohydrodynamic equations,
a simple interpretation of the flow effects on the director dynamics can be proposed. A detailed linear analysis of the problem
is presented. A systematic method to investigate nonlinear mechanisms is developed, and exemplified by the study of the nonlinear saturation in rolls. The extension of the roll amplitude equation
with the envelope formalism is used to characterize the dynamics of the roll modulations near threshold. Coupled envelope
equations are shown to describe the structure of the point defects in zig-zags observed experimentally. Finally the bifurcation
to the bimodal varicose is studied. The secondary wavevector in the bimodal appears to be selected by a rotation of the director
in the horizontal plane. Quantitative predictions concerning the amplitude of this rotation are given.
Received: 1st December 1997 / Revised: 25 May 1998 / Accepted: 2 June 1998 相似文献
12.
A.K. Kolezhuk H.-J. Mikeska 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):543-550
We study the “mixed spin” isotropic ladder system having S=1 spins on one leg and S=1/2 spins on the other, with general-type exchange interactions between spins on neighboring rungs. A set of model Hamiltonians
with exact ground states in the form of a certain matrix product wave function is obtained. We show that sufficiently strong
frustration can lead to exotic singlet ground states with infinite (exponential) degeneracy. We also list a couple of rather
simple models with nontrivial ground states, including a model with only bilinear exchange.
Received: 2 December 1997 / Accepted: 28 January 1998 相似文献
13.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
14.
R. Egger A.O. Gogolin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):281-300
We derive the effective low-energy theory for single-wall carbon nanotubes including the Coulomb interactions among electrons.
The generic model found here consists of two spin-fermion chains which are coupled by the interaction. We analyze the theory using bosonization, renormalization-group techniques,
and Majorana refermionization. Several experimentally relevant consequences of the breakdown of Fermi liquid theory observed
here are discussed in detail, e.g., magnetic instabilities, anomalous conductance laws, and impurity screening profiles.
Received: 12 December 1997 / Revised: 9 March 1998 / Accepted: 12 March 1998 相似文献
15.
V. Vescoli J. Favand F. Mila L. Degiorgi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):149-154
The validity of the optical sum rules has been addressed eversince and was always matter of debate. Particularly controversial
is the proof that the partial sum rules can be extended to both optical conductivity and energy loss function. We show in this paper that for both transverse
(optical conductivity) and longitudinal (energy loss function) absorption processes the corresponding sum rule can be theoretically
established and through appropriate conditions for the integration limits exactly verified. We also focus our attention on
the one-dimensional case within the microscopic Hubbard model. An application of these concepts to the quasi one-dimensional
systems, for which we have chosen the organic (TMTSF)2PF6 material, will also be presented.
Received: 19 December 1997 / Received in final form: 9 March 1998 / Accepted: 23 March 1998 相似文献
16.
F.A. Tamarit S.A. Cannas C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):545-548
We consider biological evolution as described within the Bak and Sneppen 1993 model. We exhibit, at the self-organized critical
state, a power-law sensitivity to the initial conditions, calculate the associated exponent, and relate it to the recently
introduced nonextensive thermostatistics. The scenario which here emerges without tuning strongly reminds of that of the tuned onset of chaos in say logistic-like one-dimensional maps. We also calculate the dynamical exponent z.
Received: 5 November 1997 / Received in final form: 11 November 1997 / Accepted: 19 November 1997 相似文献
17.
A. Wadas M. Dreyer M. Kleiber R. Wiesendanger 《Applied Physics A: Materials Science & Processing》1998,66(4):465-467
Received: 10 December 1997/Accepted: 11 December 1997 相似文献
18.
A. Delbart J. Derré R. Chipaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(2):109-116
We report a theoretical study of the Cherenkov radiation emission in uniaxial optical materials. The formalism is based on
the previous work of Muzicar (1961) whose results in terms of energetic properties of the emitted waves are corrected. This
formalism is used to predict the Cherenkov radiation emission in a strongly birefringent sodium nitrate crystal (NaNO3).
Received: 24 October 1997 / Accepted: 10 December 1997 相似文献
19.
J. Links K. Hibberd M. Gould A. Foerster 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):309-312
A new model for correlated electrons is presented which is integrable in one-dimension. The symmetry algebra of the model
is the Lie superalgebra gl(2|1) which depends on a continuous free parameter. This symmetry algebra contains the pairing algebra as a subalgebra which is used to show that the model exhibits Off-Diagonal Long-Range Order in any number
of dimensions.
Received: 9 December 1997 / Revised: 12 February 1998 / Accepted: 17 March 1998 相似文献
20.
We investigate kinetics of nematic-isotropic transition by solving the hydrodynamic equations for the nematic tensor order parameter and the fluid velocity in two space dimension (x-y plane). Numerical results indicate that nematic directors tend to align parallel to the x-y plane when hydrodynamic flow is incorporated. Late stage growth exponents, for the correlation length and for the number of topological defects, are not significantly altered by hydrodynamic flow. However, in contrast to the case
without flow, the relation holds well, which may indicate the validity of dynamical scaling for the case with hydrodynamic flow.
Received: 8 September 1997 / Received in final form: 23 October 1997 /Accepted: 3 November 1997 相似文献