共查询到20条相似文献,搜索用时 234 毫秒
1.
V.S. Gerdjikov G.G. Grahovski N.A. Kostov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):243-248
The class of nonlinear evolution equations (NLEE) - gauge equivalent to the N-wave equations related to the simple Lie algebra are derived and analyzed. They are written in terms of (x, t) ∈ satisfying r = rank nonlinear constraints. The corresponding Lax pairs and the time evolution of the scattering data are found. The Zakharov-Shabat
dressing method is appropriately modified to construct their soliton solutions.
Received 20 October 2001 / Received in final form 30 April 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
2.
Sen-yue Lou Ji Lin Xiao-yan Tang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):473-478
The Painlevé integrability of the 2+1 dimensional AKNS system is proved. Using the standard truncated Painlevé expansion which
corresponds to a special B?cklund transformation, some special types of the localized excitations like the solitoff solutions,
multi-dromion solutions and multi-ring soliton solutions are obtained.
Received 31 January 2001 and Received in final form 15 May 2001 相似文献
3.
The ill-posed linear inverse problems, characterised by Fredholm integral equations of the first kind, are encountered in
many areas of science and technology. This type of problems present some loss of information under the inversion process.
The loss of information often makes the inversion process very difficult. Magnetic force microscopy (MFM) is a technique where
problems related to loss of information occur. Work is presented here to understand what can be measured by the magnetic force
microscope. A simple model is constructed, where the magnetic tip is approximated by a point dipole. Given the force F() acting on the dipole tip, we attempt to determine the magnetization distributlon in a thin ferromagnetic film, M(). This calculation should be interesting due to the rapidiy growing interest in magnetic thin films and magnetic multilayers.
Received 3 December 2001 and Received in final form 11 March 2002 相似文献
4.
M. Hart P. Jefferies P.M. Hui N.F. Johnson 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):547-550
We present a dynamical theory of a multi-agent market game, the so-called Minority Game (MG), based on crowds and anticrowds.
The time-averaged version of the dynamical equations provides a quantitatively accurate, yet intuitively simple, explanation
for the variation of the standard deviation (`volatility') in MG-like games. We demonstrate this for the basic MG, and the
MG with stochastic strategies. The time-dependent equations themselves reproduce the essential dynamics of the MG.
Received 28 August 2000 and Received in final form 23 September 2000 相似文献
5.
J. Tempere J.T. Devreese 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):27-33
A sum rule for the first frequency moment of the optical absorption of a many-polaron system is derived, taking into account
many-body effects in the system of constituent charge carriers of the many-polaron system. In our expression for the sum rule,
the electron-phonon coupling and the many-body effects in the electron (or hole) system formally decouple, so that the many-body
effects can be treated to the desired level of approximation by the choice of the dynamical structure factor of the electron
(hole) gas. We calculate correction factors to take into account both low and high experimental cutoff frequencies.
Received 26 April 2000 and Received in final form 5 December 2000 相似文献
6.
7.
D. Bernardi V. Colombo G.G.M. Coppa A. D'Angola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):337-348
The paper deals with the time-dependent numerical simulation of inductively-coupled plasma torches during the ignition transient,
which is induced by a graphite rod and leads to the final, self-sustaining plasma condition. The study has been performed
by using a 2D time-dependent fluid-magnetic code based on the SIMPLER algorithm within the assumptions of laminar flow, local
thermodynamic equilibrium conditions and optically thin plasma. The graphite rod has been treated as a real obstacle for the
gas and the electron emission due to the thermoionic effect has been suitably taken into account. The advantage of using a
time-dependent code in order to select different plasma operating conditions that can lead to stable discharges is pointed
out. Results for both argon and air discharges are presented for different torch geometries, RF frequencies and inlet gas
configurations (also including the presence of a carrier gas injected along the axis of the torch). Moreover, the final self-sustaining
plasma configurations obtained are compared, when available, with results coming from static models, which have been published
by other authors.
Received 29 December 2000 相似文献
8.
D. O. Odero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):3-8
The time-dependent treatment of positron-hydrogen scattering for a zero total angular momentum has been presented. The initial
wavefunction of the positron-hydrogen scattering system has been expanded in terms of three dimensional dynamical wave functions
to include all higher angular momenta by solving a set of three coupled differential equations. This wavefunction is then
time evolved using Taylor series expansion of the evolution operator. The excitation probabilities are monitored as the wavefunction
propagates until there is no more change in the probabilities. The positron impact excitation cross-sections extracted from
the final wavefunction are compared with the available results of converged close coupling approach.
Received 23 July 2001 and Received in final form 25 November 2001 相似文献
9.
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
10.
11.
Pil H. Song ILki Kim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):299-303
We study the effects of dissipation or leakage on the time evolution of Grover's algorithm for a quantum computer. We introduce
an effective two-level model with dissipation and randomness (imperfections), which is based upon the idea that ideal Grover's
algorithm operates in a 2-dimensional Hilbert space. The simulation results of this model and Grover's algorithm with imperfections
are compared, and it is found that they are in good agreement for appropriately tuned parameters. It turns out that the main
features of Grover's algorithm with imperfections can be understood in terms of two basic mechanisms, namely, a diffusion
of probability density into the full Hilbert space and a stochastic rotation within the original 2-dimensional Hilbert space.
Received 12 August 2002 / Received in final form 14 October 2002 Published online 4 February 2003 相似文献
12.
T. Mančal V. May 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):173-184
The optimal control (OC) scheme for molecular dynamics is applied to the study of ultrafast bridge mediated electron transfer
(ET). Utilizing the methods of dissipative quantum dynamics in combination with the OC approach the guided charge motion in
a donor-bridge-acceptor system including a single active vibrational coordinate is studied. The control field drives the optical
transition from the electronic ground-state of the ET system into the donor-level and can be used to prepare special electronic
and vibrational states. In particular, it is demonstrated that charge localization becomes possible at the acceptor or bridge
molecule as well as in the electronic ground-state of the ET system.
Received 30 August 2000 and Received in final form 25 October 2000 相似文献
13.
T. Kanna M. Lakshmanan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):249-254
Soliton interactions in systems modelled by coupled nonlinear Schr?dinger (CNLS) equations and encountered in phenomena such
as wave propagation in optical fibers and photorefractive media possess unusual features: shape changing intensity redistributions,
amplitude dependent phase shifts and relative separation distances. We demonstrate these properties in the case of integrable
2-CNLS equations. As a simple example, we consider the stationary two-soliton solution which is equivalent to the so-called
partially coherent soliton (PCS) solution discussed much in the recent literature.
Received 1st October 2001 / Received in final form 4 February 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: lakshman@bdu.ernet.in 相似文献
14.
O.V. Gerashchenko S.L. Ginzburg M.A. Pustovoit 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):101-106
Recently we discovered the phenomenon of hypersensitivity to small time-dependent signals in a simple stochastic system, the
Kramers oscillator with multiplicative white noise. In the present work we study, theoretically and experimentally with analog
simulations, an influence of noise correlation time on hypersensitivity in a nonlinear oscillator with piecewise-linear current-voltage
characteristic and multiplicative colored dichotomous noise. We found that the region of hypersensitive behavior is defined
by universal scaling index, whereas the specifics of a particular system reveals itself only in the dependence of the above
index on system parameters. The dependence of gain factor on noise correlation time is of bell-shaped (resonant) type.
Received 27 April 2000 and Received in final form 2 November 2000 相似文献
15.
J. Gemmer G. Mahler 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(2):249-257
For a closed bi-partite quantum system partitioned into system proper and environment we interpret the microcanonical and
the canonical condition as constraints for the interaction between those two subsystems. In both cases the possible pure-state
trajectories are confined to certain regions in Hilbert space. We show that in a properly defined thermodynamical limit almost
all states within those accessible regions represent states of some maximum local entropy. For the microcanonical condition
this dominant state still depends on the initial state; for the canonical condition it coincides with that defined by Jaynes'
principle. It is these states which thermodynamical systems should generically evolve into.
Received 13 June 2002 / Received in final form 14 November 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: jochen@theol.physik.uni-stuttgart.de 相似文献
16.
R. D'Hulst G.J. Rodgers 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):619-625
We present a model describing the competition between information transmission and decision making in financial markets. The
solution of this simple model is recalled, and possible variations discussed. It is shown numerically that despite its simplicity,
it can mimic a size effect comparable to a crash localized in time. Two extensions of this model are presented that allow
to simulate the demand process. One of these extensions has a coherent stable equilibrium and is self-organized, while the
other has a bistable equilibrium, with a spontaneous segregation of the population of agents. A new model is introduced to
generate a transition between those two equilibriums. We show that the coherent state is dominant up to an equal mixing of
the two extensions. We focus our attention on the microscopic structure of the investment rate, which is the main parameter
of the original model. A constant investment rate seems to be a very good approximation.
Received 7 August 2000 and Received in final form 10 September 2000 相似文献
17.
R.H. Hernández A. Pacheco 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):265-274
We report both two-dimensional numerical simulations and experimental results that confirm the robustness of a new method
for inhibiting vortex shedding associated to the Bénard-von Kármán (BvK) instability in the wake of a cylinder. Using the
SIMPLER algorithm on a 2D channel, we solve the Navier-Stokes equations and we show that pressure suction at the front stagnation
point of a circular cylinder, modelled here through a point sink located at the front stagnation point, can completely suppress
the Bénard-von Kármán instability for super-critical Reynolds numbers. Comparison with recent experimental results are in
close agreement.
Received 7 March 2002 / Received in final form 12 September 2002 Published online 29 November 2002 相似文献
18.
C. Giordano A.R. Plastino M. Casas A. Plastino 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):361-368
Nonlinear diffusion equations provide useful models for a number of interesting phenomena, such as diffusion processes in
porous media. We study here a family of nonlinear Fokker-Planck equations endowed both with a power-law nonlinear diffusion
term and a drift term with a time dependent force linear in the spatial variable. We show that these partial differential
equations exhibit exact time dependent particular solutions of the Tsallis maximum entropy (q-MaxEnt) form. These results constitute generalizations of previous ones recently discussed in the literature [C. Tsallis,
D.J. Bukman, Phys. Rev. E 54, R2197 (1996)], concerning q-MaxEnt solutions to nonlinear Fokker-Planck equations with linear, time independent drift forces. We also show that the present
formalism can be used to generate approximate q-MaxEnt solutions for nonlinear Fokker-Planck equations with time independent drift forces characterized by a general spatial
dependence.
Received 25 April 2001 and Received in final form 6 June 2001 相似文献
19.
P. Stein N. Aßfalg H. Finkelmann P. Martinoty 《The European physical journal. E, Soft matter》2001,4(3):255-262
We investigate the behavior of the complex shear modulus of a series of elastomers including mono-domain and poly-domain liquid
crystal samples, and a non-mesomorphic sample. We find that the dynamics of the glass transition are strongly modified by
the nematic order. This result explains why the truly elastic response of liquid crystal elastomers can only be observed in
the isotropic phase at very high temperatures and at very low frequencies. Between the elastic regime and the glassy state,
the elastomers have a visco-elastic regime, which is characterized by a Rouse-like behavior for mono-domain and poly-domain
samples, and by a Zimm-like behavior for the non-mesomorphic sample. We also show that the mono-domain sample exhibits marked
anisotropy of the shear-modulus G
′. This anisotropy, which is observed for the first time, is a function of frequency and is inverted between low and high frequencies,
due to relaxation effects of the orientational order.
Received 28 January 2000 and Received in final form 16 October 2000 相似文献
20.
S. Evangelisti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):61-69
The expansion structure of a CI vector as combination of excitations from a model-space reference determinant is investigated.
It is shown that between the linear and the exponential expansions there is a relation which is similar to the single-reference
case, if the internal excitations are adsorbed into the reference vector. Moreover, expansions with respect to different determinants
are related by a set of linear equations. By using these two properties, a State-Specific Coupled-Cluster formalism is proposed.
Received 2 November 2000 / Received in final form 1st March 2002 Published online 28 June 2002 相似文献