共查询到20条相似文献,搜索用时 359 毫秒
1.
S. Mukherji 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):551-554
We study the generalized n component model of a driven diffusive system with annealed random drive in the large n limit. This non-equilibrium model also describes conserved order parameter dynamics of an equilibrium model of ferromagnets
with dipolar interaction. In this limit, at zero temperature a saddle point approximation becomes exact. The length scale
in the direction transverse to the driving field acquires an additional logarithmic correction in this limit.
Received 24 January 2000 and Received in final form 29 May 2000 相似文献
2.
L. Berthier 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):689-692
We study analytically the aging dynamics of the O(n) model in the limit of , with conserved and with non-conserved order parameter. While in the non-conserved dynamics, the autocorrelation function
scales in the usual way , in the case of a conserved order parameter, `multiscaling' manifests itself in the form , with a relaxation time growing more slowly than the age of the system (sub-aging), and h(t) a function growing faster than any length scale of the problem. In both cases, the effective temperature associated to the
violation of the fluctuation theorem tends to infinity in the asymptotic limit of large waiting times.
Received 15 May 2000 and Received in final form 5 July 2000 相似文献
3.
A fireball model with time evolution based on transport calculations is used to examine the dilepton emission rate of an ultra-relativistic
heavy-ion collision. A transition from hadronic matter to a quark-gluon plasma at a critical temperature T
C between 130-170 MeV is assumed. We also consider a possible mixed phase scenario. We include thermal corrections to the hadronic
spectra below T
C and use perturbation theory above T
C. The sensitivity of the spectra with respect to the freeze-out temperature, the initial fireball temperature and the critical
temperature is investigated.
Received: 4 August 2000 / Accepted: 14 November 2000 相似文献
4.
D.V. Livanov A.A. Varlamov M. Putti M.R. Cimberle C. Ferdeghini 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):401-404
The fluctuation-induced magnetoconductivity of the Bi2Sr2Ca2Cu3O10+x phase is studied above zero-field critical temperature Tc(0) and for moderate magnetic fields. It is found that the Gaussian approximation for superconducting fluctuations underestimates
the negative fluctuation magnetoconductance drastically in the Tc(0) < T < Tc(0) + 20 K temperature range. Taking into account the critical fluctuation contribution on the base of self-consistent Hartree
approximation makes it possible to explain the data quantitatively in terms of the only Aslamazov-Larkin contribution for
different magnetic fields and temperatures, consistently with the zero field data.
Received 14 April 2000 and Received in final form 13 July 2000 相似文献
5.
M. Dudzinski J. Sznajd J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):575-579
The zero temperature phase diagram of a one-dimensional ferromagnet with cubic single ion anisotropy in an external magnetic
field is studied. The mean-field approximation and the density-matrix renormalization group method are applied. Two phases
at finite magnetic fields are identified: a canted phase with spontaneously broken symmetry and a phase with magnetization
along the magnetic field. Both methods predict that the canted phase exists even for the single-ion anisotropy strong enough
to destroy the magnetic order at zero magnetic field. In contrast to the mean-field theory, the density-matrix renormalization
group predicts a reentrant behavior for the model. The character of the phase transition at finite magnetic field has also
been considered and the critical index has been found.
Received 9 May 2000 and Received in final form 5 July 2000 相似文献
6.
E. Canessa 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):123-127
We address the issue of stock market fluctuations within Langevin Dynamics (LD) and the thermodynamics definitions of multifractality
in order to study its second-order characterization given by the analogous specific heat Cq, where q is an analogous temperature relating the moments of the generating partition function for the financial data signals. Due
to non-linear and additive noise terms within the LD, we found that Cq can display a shoulder to the right of its main peak as also found in the S&P500 historical data which may resemble a classical
phase transition at a critical point.
Received 6 November 2000 and Received in final form 26 March 2001 相似文献
7.
We study the O(N) symmetric linear sigma-model at finite temperature as the low-energy effective models of quantum chromodynamics (QCD) using
the Cornwall-Jackiw-Tomboulis (CJT) effective action for composite operators. It has so far been claimed that the Nambu-Goldstone
theorem is not satisfied at finite temperature in this framework unless the large-N limit in the O(N) symmetry is taken. We show that this is not the case. The pion is always massless below the critical temperature, if one
determines the propagator within the form such that the symmetry of the system is conserved, and defines the pion mass as
the curvature of the effective potential. We use a regularization for the CJT effective potential in the Hartree approximation,
which is analogous to the renormalization of auxiliary fields. A numerical study of the Schwinger-Dyson equation and the gap
equation is carried out including the thermal and quantum loops. We point out a problem in the derivation of the sigma meson
mass without quantum correction at finite temperature. A problem about the order of the phase transition in this approach
is also discussed.
Received: 21 June 2000 / Accepted: 13 September 2000 相似文献
8.
J.C. Ewert G. Schmitz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):391-403
A study of the reordering kinetics of ion-irradiated Ni3Al is presented. The development of long-range order during annealing treatments is measured by quantitative electron diffractometry.
According to the temperature dependence of the observed kinetics, the reaction is dominated by non-equilibrium vacancies.
As a consequence, the kinetics can be calibrated versus the absolute number of atomic jumps necessary to establish the observed degree of order. In order to analyse the experimental
data, Monte Carlo simulations are performed. It is shown that, beside the temperature dependence of the driving force, the
ordering efficiency of the vacancy jumps itself is temperature dependent due to different mobilities of the atomic species.
Received 6 December 1999 and Received in final form 23 June 2000 相似文献
9.
10.
A. Saber G. Mattei X. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):393-399
Within the framework of the effective field theory with a probability distribution technique that accounts for the single-site
spin correlations, we examine the critical behavior of the transverse ferromagnetic spin-1 Ising model of an alternating magnetic
superlattice. The critical temperature of the alternating magnetic superlattice has been studied as a function of the interlayer
and intralayer exchange interactions and the strength of the transverse field and the thickness of the finite superlattice.
Received 12 January 2000 and Received in final form 14 September 2000 相似文献
11.
E. Del Gado L. de Arcangelis A. Coniglio 《The European physical journal. E, Soft matter》2000,2(4):359-365
Within a recently introduced model based on the bond-fluctuation dynamics, we study the viscoelastic behaviour of a polymer
solution at the gelation threshold. We here present the results of the numerical simulation of the model on a cubic lattice:
the percolation transition, the diffusion properties and the time autocorrelation functions have been studied. From both the
diffusion coefficients and the relaxation times critical behaviour a critical exponent k for the viscosity coefficient has been extracted: the two results are comparable within the errors giving , in close agreement with the Rouse model prediction and with some experimental results. In the critical region below the
transition threshold the time autocorrelation functions show a long-time tail which is well fitted by a stretched exponential
decay.
Received 20 December 1999 and Received in final form 18 February 2000 相似文献
12.
E.L. Præstgaard B. Schmittmann R.K.P. Zia 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):675-695
We investigate the collective behavior of an Ising lattice gas, driven to non-equilibrium steady states by being coupled to
two thermal baths. Monte Carlo methods are applied to a two-dimensional system in which one of the baths is fixed at infinite
temperature. Both generic long range correlations in the disordered state and critical properties near the second order transition
are measured. Anisotropic scaling, a key feature near criticality, is used to extract and some critical exponents. On the theoretical front, a continuum theory, in the spirit of Landau-Ginzburg, is presented.
Being a renormalizable theory, its predictions can be computed by standard methods of -expansions and found to be consistent with simulation data. In particular, the critical behavior of this system belongs to
a universality class which is quite different from the uniformly driven Ising model.
Received 4 October 2000 相似文献
13.
N.J. Mottram S.J. Elston 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):277-284
We have theoretically investigated chevron formation in smectic C materials and the transformation of this chevron structure to a tilted layer structure as the cell is sheared. We find a
series of transition temperatures at which the behaviour of the cell critically changes. As the cell is cooled from the smectic
A phase past the first critical temperature there is a second order transition which forms two tilted layer states with lower energy than the smectic A bookshelf structure. Although these low energy tilted structures exist the bookshelf structure is the stable state for zero
shear. However, upon further cooling this bookshelf structure becomes unstable to the formation of a chevron state. Now when
the cell is sheared the chevron structure smoothly transforms into the tilted layer structure. As each further critical temperature
is passed an additional multiple chevron solution is formed which although a high energy, unstable state may be observed transiently. For sufficiently low
temperatures the transition from chevron to tilted layer becomes first order. This first order transition occurs as the chevron
interface merges with the surface alignment region to form the tilted layer structure.
Received 28 December 1998 and Received in final form 8 April 1999 相似文献
14.
Adhesion between membranes is studied using a phenomenological model, where the inter-membrane distance is coupled to the
concentration of sticker molecules on the membranes. The model applies to both adhesion of two flexible membranes and to adhesion
of one flexible membrane onto a second membrane supported on a solid substrate. We mainly consider the case where the sticker
molecules form bridges and adhere directly to both membranes. The calculated mean-field phase diagrams show an upward shift
of the transition temperature indicating that the lateral phase separation in the membrane is enhanced due to the coupling effect. Hence the possibility of adhesion-induced lateral phase separation is predicted. For a particular
choice of the parameters, the model exhibits a tricritical behavior. We also discuss the non-monotonous shape of the inter-membrane
distance occurring when the lateral phase separation takes place. The inter-membrane distance relaxes to the bulk values with
two symmetric overshoots. Adhesion mediated by other types of stickers is also considered.
Received 12 January 2000 and Received in final form 15 May 2000 相似文献
15.
M.E.S. Borelli H. Kleinert A.M.J. Schakel 《The European physical journal. E, Soft matter》2001,4(2):217-221
A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures,
the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.
Received 26 April 2000 and Received in final form 16 August 2000 相似文献
16.
D. Dantchev J. Rudnick 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):251-268
We study the behavior of systems in which the interaction contains a long-range component that does not dominate the critical
behavior. Such a component is exemplified by the van der Waals force between molecules in a simple liquid-vapor system. In
the context of the mean spherical model with periodic boundary conditions we are able to identify, for temperatures close
above T
c, finite-size contributions due to the subleading term in the interaction that are dominant in this region decaying algebraically as a function of L. This mechanism goes beyond the standard formulation of the finite-size scaling but is to be expected in real physical systems.
We also discuss other ways in which critical point behavior is modified that are of relevance for analysis of Monte Carlo
simulations of such systems.
Received 21 November 2000 and Received in final form 28 February 2001 相似文献
17.
Young-Dae Jung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):351-354
In nonideal classical plasmas, the electron captures by positrons from hydrogenic ions are investigated. An effective pseudopotential
model taking into account the plasma screening effects and collective effects is applied to describe the interaction potential
in nonideal plasmas. The classical Bohr-Lindhard model has been applied to obtain the electron capture radius and electron
capture probability. The modified hyperbolic trajectory method is applied to the motion of the projectile positron in order
to visualize the electron capture probability as a function of the impact parameter, nonideal plasma parameter, projectile
velocity, and plasma parameters. The results show that the electron capture probability in nonideal plasmas is always greater
than that in ideal plasmas descried by the Debye-Hückel potential, i.e., the collective effect increases the electron capture probability. It is also found that the collective effect is decreased
with increasing the projectile velocity.
Received 21 January 2000 and Received in final form 27 April 2000 相似文献
18.
B. Bassetti C.A. Mantica P. Jona 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):359-369
A material surface of pure constituents with a flexible molecular chain (amphiphilics) is considered; thermodynamic behaviour
is studied in the chain length-temperature plane. The Hamiltonian of the system is modelled as the sum of a formation term
which refers to the polymer nature of the chain, and of a fluctuation term with a specific elastic form. For closed systems
the model exhibits phases with uniform curvature and conformational order/disorder or, alternatively, modulated phases; a
critical chain length is found for the existence of modulated phases; the dependence of transition temperature on energy parameters
is determined. A critical region is found for open systems, where conformational disorder drives spontaneous generation of
curvature; this lies above a characteristic chain length and around the shape transition temperature.
Received: 13 November 1996 / Revised: 9 May 1997 / Received in final form: 4
November 1997 / Accepted: 10 November 1997 相似文献
19.
T. Saikawa A. Ferraz 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):65-74
A precursor effect on the Fermi surface in the two-dimensional Hubbard model at finite temperatures near the antiferromagnetic
instability is studied using three different itinerant approaches: the second order perturbation theory, the paramagnon theory
(PT), and the two-particle self-consistent (TPSC) approach. In general, at finite temperature, the Fermi surface of the interacting
electron systems is not sharply defined due to the broadening effects of the self-energy. In order to take account of those
effects we consider the single-particle spectral function A(, 0) at the Fermi level, to describe the counterpart of the Fermi surface at T = 0. We find that the Fermi surface is destroyed close to the pseudogap regime due to the spin-fluctuation effects in both
PT and TPSC approaches. Moreover, the top of the effective valence band is located around = (π/2,π/2) in agreement with earlier investigations on the single-hole motion in the antiferromagnetic background. A crossover
behavior from the Fermi-liquid regime to the pseudogap regime is observed in the electron concentration dependence of the
spectral function and the self-energy.
Received 8 September 2000 and Received in final form 20 December 2000 相似文献
20.
W. Jeżewski 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):133-138
Scaling properties of the Gibbs distribution of a finite-size one-dimensional Ising model are investigated as the thermodynamic
limit is approached. It is shown that, for each nonzero temperature, coarse-grained probabilities of the appearance of particular
energy levels display multiscaling with the scaling length ℓ = 1/M
n, where n denotes the number of spins and Mn is the total number of energy levels. Using the multifractal formalism, the probabilities are argued to reveal also multifractal
properties.
Received 10 July 2000 and Received in final form 6 November 2000 相似文献