共查询到20条相似文献,搜索用时 31 毫秒
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T.T. Truong 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):697-703
We point out the existence of an alternative algebraic structure in Yang-Baxter algebra with trigonometric R-matrix, which appears to be the generalization of the Yangian in Yang-Baxter algebras with rational R-matrix and which is described most naturally by q-commutators. Some properties are presented, in particular in the case of the well-known symmetric six-vertex model.
Received: 13 February 1998 / Revised: 16 March 1998 / Accepted: 17 April 1998 相似文献
3.
S. Galam B. Chopard A. Masselot M. Droz 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):529-531
A simple cellular automata model for a two-group war over the same “territory” is presented. It is shown that a qualitative
advantage is not enough for a minority to win. A spatial organization as well a definite degree of aggressiveness are instrumental
to overcome a less fitted majority. The model applies to a large spectrum of competing groups: smoker-non smoker war, epidemic
spreading, opinion formation, competition for industrial standards and species evolution. In the last case, it provides a
new explanation for punctuated equilibria.
Received: 21 April 1998 / Revised and Accepted: 22 April 1998 相似文献
4.
X. Waintal D. Weinmann J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(3):451-456
For two particles in a disordered chain of length L with on-site interaction U, a duality transformation maps the behavior at weak interaction onto the behavior at strong interaction. Around the fixed
point of this transformation, the interaction yields a maximum mixing of the one body states. When (the one particle localization length), this mixing results in weak chaos accompanied by multifractal wave functions and
critical spectral statistics, as in the one particle problem at the mobility edge or in certain pseudo-integrable billiards.
In one dimension, a local interaction can only yield this weak chaos but can never drive the two particle system to full chaos
with Wigner-Dyson statistics.
Received: 22 May 1998 / Received in final form: 24 August 1998 / Accepted: 4 September 1998 相似文献
5.
É. Maréchal S. Guibal J.-L. Bossennec M.-P. Gorza R. Barbé J.-C. Keller O. Gorceix 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):195-198
The mechanical Stern-Gerlach effect is investigated in the case of a slow atomic cloud falling through an inhomogeneous magnetic
field featuring a strong longitudinal gradient. The resulting Zeeman sublevel state selection is demonstrated under various
experimental conditions. Longitudinal spatial separations are in agreement with numerical simulations that take into account
the gravitational acceleration and both the transverse and axial magnetic forces. Since separations greater than 20 cm are
obtained, potential applications in atom optics are outlined.
Received: 16 February 1998 / Received in final form: 1 April 1998 / Accepted: 6 April 1998 相似文献
6.
D. Chowdhury A. Pasupathy S. Sinha 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):781-786
In the Nagel-Schreckenberg model of vehicular traffic on single-lane highways vehicles are modelled as particles which hop
forward from one site to another on a one dimensional lattice and the inter-particle interactions mimic the manner in which
the real vehicles influence each other's motion. In this model the number of empty lattice sites in front of a particle is
taken to be a measure of the corresponding distance-headway (DH). The time-headway (TH) is defined as the time interval between the departures (or arrivals) of two successive particles recorded by a detector
placed at a fixed position on the model highway. We investigate the effects of spatial inhomogeneities of the highway (static
hindrances) on the DH and TH distributions in the steady-state of this model.
Received: 2 March 1988 / Revised: 13 April 1998 / Accepted: 17 April 1998 相似文献
7.
T. Kerle J. Klein K. Binder 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(3):401-410
The capillary broadening of a 2-phase interface is investigated both experimentally and theoretically. When a binary mixture
in a thin film with thickness D segregates into two coexisting phases the interface between the two phases may form parallel to the substrate due to preferential
surface attraction of one of the components. We show that the interfacial profile (of intrinsic width w0) is broadened due to capillary waves, which lead to fluctuations, of correlation length of the local interface positions in the directions parallel to the confining walls. We postulate that acts as an upper cutoff for the spectrum of capillary waves on the interface, so that the effective mean square interfacial
width w varies as . In the limit of large D this yields or respectively for the case of short- or long-range forces between walls and the interface. We used the Nuclear Reaction Analysis
depth profiling technique, to investigate this broadening effect directly in two binary polymer mixtures. Our results reveal
that the interfacial width indeed increases with film thickness D, though the observed interfacial width is lower than the predicted w. This is probably due to surface tension effects imposed by the confining surfaces which are not taken into account in our
model.
Received: 19 February 1998 / Received in final form: 2 September 1998 / Accepted: 8 September 1998 相似文献
8.
A. Milchev J.P. Wittmer D.P. Landau 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):241-251
We use an off-lattice microscopic model for solutions of equilibrium polymers (EP) in a lamellar shear flow generated by means
of a self-consistent external field between parallel hard walls. The individual conformations of the chains are found to elongate
in flow direction and shrink perpendicular to it while the average polymer length decreases with increasing shear rate. The
Molecular Weight Distribution of the chain lengths retains largely its exponential form in dense solutions whereas in dilute
solutions it changes from a power-exponential Schwartz distribution to a purely exponential one upon an increase of the shear
rate. With growing shear rate the system becomes increasingly inhomogeneous so that a characteristic variation of the total
monomer density, the diffusion coefficient, and the center-of-mass distribution of polymer chains of different contour length
with the velocity of flow is observed. At higher temperature, as the average chain length decreases significantly, the system is shown to undergo an order-disorder transition
into a state of nematic liquid crystalline order with an easy direction parallel to the hard walls. The influence of shear
flow on this state is briefly examined.
Received 22 October 1998 and Received in final form 12 April 1999 相似文献
9.
The simulation of a two-dimensional, broadly polydisperse, living polymers system at high concentration reveals an unusual
conformational behaviour for the longer chains. Unlike in three dimensions, the longer chains are not swollen but are squeezed
by the smaller chains. This observation is discussed in terms of a two dimensional solvent- polymer mixture whose solvent
particules are larger than the polymer monomers.
Received: 13 December 1996 / Revised: 16 March 1998 / Accepted: 27 March 1998 相似文献
10.
F. Iglói D. Karevski H. Rieger 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):613-625
We consider cooperative processes (quantum spin chains and random walks) in one-dimensional fluctuating random and aperiodic
environments characterized by fluctuating exponents . At the critical point the random and aperiodic systems scale essentially anisotropically in a similar fashion: length (L) and time (t) scales are related as . Also some critical exponents, characterizing the singularities of average quantities, are found to be universal functions
of , whereas some others do depend on details of the distribution of the disorder. In the off-critical region there is an important
difference between the two types of environments: in aperiodic systems there are no extra (Griffiths)-singularities.
Received: 5 February 1998 / Accepted: 17 April 1998 相似文献
11.
F. Tedoldi A. Campana P. Carretta 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):219-223
μSR measurements in the antiferromagnetic (AF) phase of Ni1-xLixO for are reported. While in pure NiO the muon longitudinal depolarization rate is found almost temperature independent, in the Li-doped compounds broad maxima around 130 K are observed. These maxima are
associated with the progressive freezing of the spin fluctuations of S
=1/2 defects induced by the localization of the extra-holes. From the temperature dependence of and the stretched exponential form of the depolarization, insights on the distribution of correlation times for the fluctuating
field at the muon site are derived.
Received: 27 April 1998 / Received in final form and Accepted: 21 August 1998 相似文献
12.
X. Waintal J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(1):117-121
For N interacting particles in a one dimensional random potential, we study the structure of the corresponding network in Hilbert
space. The states without interaction play the role of the “sites”. The hopping terms are induced by the interaction. When
the one body states are localized, we numerically find that the set of directly connected “sites” is multifractal. For the
case of two interacting particles, the fractal dimension associated to the second moment of the hopping term is shown to characterize
the Golden rule decay of the non interacting states and the enhancement factor of the localization length.
Received: 17 April 1998 / Accepted: 14 May 1998 相似文献
13.
We present an analytical approach of the dynamics of a polymer when it is quenched from a solvent into a good or bad solvent. The dynamics is studied by means of a Langevin equation, first in the absence of hydrodynamic
effect, then taking into account the hydrodynamic interactions with the solvent. The variation of the radius of gyration is
studied as a function of time. In both cases, for the first stage of collapse or swelling, the evolution is described by a
power law with a characteristic time proportional to N
4/3
(N), where N is the number of monomers, without (with) hydrodynamic interactions. At larger times, scaling laws are derived for the diffusive
relaxation time.
Received: 10 March 1998 / Received in final form: 15 September 1998 / Accepted: 25 September 1998 相似文献
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F.J. Arranz F. Borondo R.M. Benito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(2):181-187
Low resolution features in the spectra of classically chaotic atomic and molecular systems are known to be related to recurrences
induced by classical periodic motions. In this paper we study how such characteristics reveal in the LiNC/LiCN isomerizing
molecular system, and describe how the transition from regularity to classical chaos that takes place in this system shows
up at quantum level in the structure of the corresponding wavefunctions in the form of “scars”. To this end we use some projection
techniques, based on the propagation of wave packets, which have been developed in our laboratory. In this way some regions
at the border of the chaotic region can be detected, in which the systematics of “scar” formation can be studied at a very
elementary level, without complications due to the high level density which are customarily used in this type of studies in
order to achieve the semiclassical limit.
Received: 16 March 1998 / Revised: 23 April 1998 / Accepted: 4 May 1998 相似文献
16.
S. Fujimoto N. Kawakami 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):389-393
The effects of Umklapp scattering on the zero-temperature conductance in one-dimensional quantum wires are reexamined by taking
into account both the screening of external potential and the non-uniform chemical potential shift due to electron-electron
interaction. It is shown that in the case away from half-filling the conductance is given by the universal value, 2e
2
/h, even in the presence of Umklapp scattering, owing to these renormalization effects of external potential. The conclusion
is in accordance with the recent claim obtained for the system with non-interacting leads being attached to a quantum wire.
Received: 5 February 1998 / Received in final form: 16 March 1998 / Accepted: 17 April 1998 相似文献
17.
D. Langevin 《The European physical journal. E, Soft matter》2001,5(1):81-85
Studies of thin liquid films, made from semidilute polyelectrolyte solutions, are presented. The disjoining pressure variation
with film thickness exhibits oscillations, corresponding to film stratification. The oscillations become sharper as the polymer
concentration c increases, and disappear when salt is added. The period of the oscillations scales as c
-1/2. The observed stratification is related to the polymer network and the size of the steps to the mesh size ξ.
Received 25 April 2000 and Received in final form 3 October 2000 相似文献
18.
R. Guirado-López D. Spanjaard M.-C. Desjonquères 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(4):459-466
The magnetic properties of small YN clusters are studied by using a tight-binding Hubbard Hamiltonian in the unrestricted Hartree-Fock approximation. Several
types of cluster geometries are considered in order to see the effects of the size and symmetry of the structures on the magnetic
properties. The average magnetic moments are found to be constant over large domains of variations in the interatomic distance, a fact that can be explained by the
existing closed shell electronic configurations at least for one spin direction in all our magnetic solutions. Small energy
gains upon the onset of magnetization are obtained, which reveals the low stability of the magnetic solutions. Our results
contradict the prediction of a magnetic-nonmagnetic transition at a large cluster size (about 90 atoms) for these kinds of
systems.
Received: 27 April 1998 / Received in final form: 23 June 1998 / Accepted: 17 July 1998 相似文献
19.
T.M. Nieuwenhuizen C.N.A. van Duin 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):191-209
In realistic spinglasses, such as , and , magnetic atoms are located at random positions. Their couplings are determined by their relative positions. For such systems
a field theory is formulated. In certain limits it reduces to the Hopfield model, the Sherrington-Kirkpatrick model, and the
Viana-Bray model. The model has a percolation transition, while for RKKY couplings the “concentration scaling” occurs. Within the Gaussian approximation the Ginzburg-Landau expansion is considered in the clusterglass phase, that is
to say, for not too small concentrations. Near special points, the prefactor of the cubic term, or the one of the replica-symmetry-breaking
quartic term, may go through zero. Around such points new spin glass phases are found.
Received: 27 April 1998 / Received in final form: 27 July 1998 / Accepted: 13 August 1998 相似文献
20.
O. Toulemonde F. Studer A. Barnabé A. Maignan C. Martin B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):159-167
The XAS study at Cr, Co, Ni and Mn K-edges was performed for the doped CMR manganites Ln0.5Ca0.5Mn1-xBxO3 with Ln=La, Nd, Sm and B= Cr, Co, Ni (), on the samples that were studied previously for their ferromagnetic-metallic to antiferromagnetic-insulator transition.
We observed that the formal charges of the doping elements are Ni2+, Co2+ and Cr3+. It is also evidenced that the average formal charge of the manganese is increased after doping, in agreement with the charge
compensation keeping “O3” stoichiometry. These results suggest that the doping elements participate directly to the band structure.
Received: 9 January 1998 / Received in final form: 6 April 1998 / Accepted: 7 April 1998 相似文献