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1.
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
2.
P. Dommersnes S. Straumsnes E.G. Flekkøy T. Nicolai S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):669-677
We study the hydrodynamic properties of polymers and more generally self-similar structures using a new recursion model. The
hydrodynamic interaction between monomers is modeled by the standard Green's function of Stokes flow in which an ultrametric
distance is substituted for the usual Euclidean distance. This leads to a model where the long-range hydrodynamic interactions
and the long-range correlations of the polymer conformation can both be accounted for and yet allow for analytical solutions.
We explore the asymptotic as well as the finite size corrections to the scaling behavior with this model. In order to compare
the results of the present scheme with more conventional techniques a generalized version of the existing mean field results
by Kirkwood and Riseman for the hydrodynamic drag is introduced.
Received 26 August 1998 and Received in final form 7 December 1998 相似文献
3.
W. Poirier M. Sanquer K. Saminadayar 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):293-300
We study weak localization and electron interaction in CdTe:In by low temperature magnetoconductance experiments to quantify
the phase breaking length and the importance of interactions in CdTe. Then we study superconducting contacts to CdTe:In by
transport measurements at very low temperature. The conductance-voltage characteristics of the superconducting contact exhibits
the main features of a SIN junction, with a superimposed zero bias anomaly. This anomaly in the density of states of CdTe
is very sensitive to magnetic field and probably induced by the proximity of the superconducting contact.
Received 6 May 1998 and Received in final form 20 October 1998 相似文献
4.
A.K. Hartmann U. Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(1):105-109
We investigate the critical behavior of three-dimensional random-field Ising systems with both Gauss and bimodal distribution
of random fields and additional the three-dimensional diluted Ising antiferromagnet in an external field. These models are
expected to be in the same universality class. We use exact ground-state calculations with an integer optimization algorithm
and by a finite-size scaling analysis we calculate the critical exponents , , and . While the random-field model with Gauss distribution of random fields and the diluted antiferromagnet appear to be in same
universality class, the critical exponents of the random-field model with bimodal distribution of random fields seem to be
significantly different.
Received: 9 July 1998 / Received in final form: 15 July 1998 / Accepted: 20 July
1998 相似文献
5.
Mixed spin transverse Ising model with longitudinal random crystal field interactions 总被引:1,自引:0,他引:1
N. Benayad R. Zerhouni A. Klümper 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):687-695
The effect of a longitudinal random crystal field interaction on the phase diagrams of the mixed spin transverse Ising model
consisting of spin-1/2 and spin-1 is investigated within the finite cluster approximation based on a single-site cluster theory.
In order to expand a cluster identity of spin-1, we transform the spin-1 to spin-1/2 representation containing Pauli operators.
We derive the state equations applicable to structures with arbitrary coordination number N. The phase diagrams obtained in the case of a honeycomb lattice (N=3) and a simple-cubic lattice (N=6), are qualitatively different and examined in detail. We find that both systems exhibit a variety of interesting features
resulting from the fluctuation of the crystal field interactions.
Received: 13 February 1998 / Accepted: 17 March 1998 相似文献
6.
We consider two situations where hydrodynamic interactions are said to be “screened”: hydrodynamics in a gel or in a porous
medium, and electrophoresis in an electrolyte. We focus on the corresponding Green functions, and show that the flow fields
are similar in the two cases. Contrarily to statements often made, the fluid velocity decays algebraically with distance (), i.e. not exponentially. We point out that the pressure fields are different in the two cases.
Received 23 March 2000 相似文献
7.
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
8.
M. Petit M. Nobili P. Barois 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):341-345
We report the first observation of an electroclinical effect at the TGB-TGB transition induced by an external DC electric field applied perpendicular to the pitch direction. Upon increasing the field,
the smectic layers rather than the director field tilt over relative to the helical axis, allowing to detect the effect by
X-ray scattering from well aligned samples. The observations are qualitatively interpreted in the frame of a mean field phenomenological
model of a helically modulated electroclinical effect.
Received: 24 April 1998 / Revised: 22 June 1998 / Accepted: 31 July 1998 相似文献
9.
A. Lambrecht M.T. Jaekel S. Reynaud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):95-104
We calculate the photon emission of a high finesse cavity moving in vacuum. The cavity is treated as an open system. The field
initially in the vacuum state accumulates a dephasing depending on the mirrors motion when bouncing back and forth inside
the cavity. The dephasing is not linearized in our calculation, so that qualitatively new effects like pulse shaping in the
time domain and frequency up-conversion in the spectrum are found. Furthermore we predict the existence of a threshold above
which the system should show self-sustained oscillations.
Received: 10 December 1997 / Received in final form: 27 March 1998 / Accepted: 27 March 1998 相似文献
10.
Nonparabolic multivalley balance-equation approach to impact ionization: Application to wurtzite GaN
J.C. Cao X.L. Lei 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(1):79-83
Extended nonparabolic multivalley balance equations including impact ionization (II) process are presented and are applied
to study electron transport and impact ionization in wurtzite-phase GaN with a , L-M, and conduction band structure at high electric field up to 1000kV/cm. Hot-electron transport properties and impact ionization
coefficient are calculated taking account of the scatterings from ionized impurity, polar optical, deformation potential,
and intervalley interactions. It is shown that, for wurtzite GaN when the electric field approximately equals 530kV/cm, the
II process begins to contribute to electron transport and results in an increase of the electron velocity and a decrease of
the electron temperature, in comparison with the case without the II process. Similar calculations for GaAs are also carried
out and quantitative agreement is obtained between the calculated II coefficients by this present approach and the experimental
data. Relative to GaAs, GaN has a higher threshold electric field for II and a smaller II coefficient.
Received: 27 April 1998 / Revised: 17 July 1998 / Accepted: 13 August 1998 相似文献
11.
A.A. Zvyagin D.M. Apal'kov 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):565-569
We present a Bethe Ansatz based investigation of a one-dimensional (1D) Heisenberg spin chain in a real 3D crystal lattice.
We have shown that due to an influence of the lattice distortion on a crystalline field of ligands of magnetic ions, a Heisenberg
antiferromagnetic spin chain is unstable under the appearance of a magnetic anisotropy of the “easy-plane” type. The effects of an external magnetic
field and nonzero temperature onto such a phase transition are studied.
Received: 19 January 1998 / Revised: 16 March 1998 / Accepted: 17 March 1998 相似文献
12.
X.L. Lei H.L. Cui 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):513-518
We suggest a balance-equation approach to hot-electron transport in a single arbitrary energy band subject to an intense radiation
field of terahertz (THz) frequency, including all the multiphoton emission and absorption processes and taking account of
realistic scatterings due to impurities and phonons. This approach, which allows one to calculate THz-driving, time-averaging
transport based on a set of time-independent equations, provides a convenient method to study the effect of an intense THz
electric field on carrier transport in a nonparabolic energy band. As an example, these fully three-dimensional, acceleration-
and energy-balance equations are applied to the discussion of superlattice miniband transport at lattice temperature T=77 and 300 K driven by the THz radiation field of varying strengths. It is shown that the current through a dc biased miniband
superlattice is greatly reduced by the irradiation of an intense THz electric field.
Received: 23 January 1998 / Revised: 31 March 1998 / Accepted: 20 April 1998 相似文献
13.
F. Elias I. Drikis A. Cebers C. Flament J.-C. Bacri 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):203-209
Two-dimensional magnetic fluid foams are cellular structures whose framework is made of magnetic fluid. The features of these
equilibrated patterns are driven by a control parameter: the amplitude of the applied magnetic field. When the latter is rapidly
increased, an instability occurs: the walls between cells undulate. Such an instability has also been observed in other 2D
cellular structures, which exist for instance in Langmuir monolayers or in magnetic garnets thin films. In this paper we give
a theoretical analysis of this instability, the issues of which are shown to be well confirmed by experiments and numerical
simulations.
Received: 13 October 1997 / Received in final form: 28 January 1998 / Accepted: 9 March 1998 相似文献
14.
B. Reusch R. Blümel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(2):123-127
Numerical simulations of the equations of motion of 300 charged particles confined to a plane with an additional magnetic
field orthogonal to the plane reproduce recently observed self-organization of non-neutral plasmas into a small number of
interacting vortices. In the presence of damping we observe crystallized vortices, i.e. vortices with regular internal structure. We also observe crystallized vortex crystals, i.e. geometric patterns of crystallized vortices. Fractal vortex arrangements are investigated and found to be stable. Our results
are relevant for quantum dots and artificial atoms.
Received: 24 February 1998 / Revised: 4 March 1998 / Accepted: 4 May
1998 相似文献
15.
M. Sellitto 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):135-138
We investigate by Monte-Carlo simulation the linear response function of three dimensional structural glass models defined
by short-range kinetic constraints and a trivial equilibrium Boltzmann-Gibbs measure. The breakdown of the fluctuation-dissipation
theorem in the glassy phase follows the prediction of mean field low temperature mode-coupling theory.
Received: 24 April 1998 / Received in final form: 8 May 1998 / Accepted: 11 May 1998 相似文献
16.
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
17.
A. Fledderjohann M. Karbach K.-H. Mütter 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):487-494
We investigate the scaling properties of the excitation energies and transition amplitudes of the one-dimensional spin- antiferromagnetic Heisenberg model exposed to an external perturbation. Two types of perturbations are discussed in detail:
a staggered field and a dimerized field.
Received: 27 February 1998 / Accepted: 17 April 1998 相似文献
18.
19.
A mean field approach is used to estimate the energy dissipation during the homogeneous sedimentation or the particulate fluidization
of non Brownian hard spheres in a concentrated suspension of infinite extent. Depending on inertial screening and the range
of the hydrodynamic interactions, the effective buoyancy force is determined either from the average suspension density in
a Stokes flow or from the fluid density in the turbulent flow regime. An energy balance then yields a settling or fluidization
law depending on the particle Reynolds number in reasonable agreement with the Richardson and Zaki correlation and recent
experimental results for particle settling or fluidization. We further estimate the energy dissipation in the turbulent boundary
layers around the particles to precise the Reynolds number dependence of the hindered settling function in the intermediate
flow regime.
Received 22 February 1999 and Received in final form 14 June 1999 相似文献
20.
H. Hinrichsen M. Howard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):635-643
We introduce a model for the spreading of epidemics by long-range infections and investigate the critical behaviour at the
spreading transition. The model generalizes directed bond percolation and is characterized by a probability distribution for
long-range infections which decays in d spatial dimensions as . Extensive numerical simulations are performed in order to determine the density exponent and the correlation length exponents and for various values of . We observe that these exponents vary continuously with , in agreement with recent field-theoretic predictions. We also study a model for pairwise annihilation of particles with
algebraically distributed long-range interactions.
Received: 4 September 1998 / Accepted: 22 September 1998 相似文献