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1.
T. S. Evans 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):65-69
Evolving networks with a constant number of edges may be
modelled using a rewiring process. These models are used to
describe many real-world processes including the evolution of
cultural artifacts such as family names, the evolution of gene
variations, and the popularity of strategies in simple
econophysics models such as the minority game. The model is
closely related to Urn models used for glasses, quantum gravity
and wealth distributions. The full mean field equation for the
degree distribution is found and its exact solution and generating
solution are given. 相似文献
2.
I. Goidenko I. Tupitsyn G. Plunien 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):171-177
In this paper, we present a family of coupled higher-order
nonlinear Schr?dinger equation describing the optical soliton pulse
propagating in inhomogeneous optical fiber media. The exact N-soliton
solution and its characteristics of stabilities and novel elastic collision
properties are studied in detail. As an example, we give the relative
numerical evolutions by a soliton control system to discuss the pulses
propagation characteristics. 相似文献
3.
P. Fronczak A. Fronczak J. A. Hołyst 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):133-139
We study a model of network with clustering and desired node
degree. The original purpose of the model was to describe optimal
structures of scientific collaboration in the European Union. The
model belongs to the family of exponential random graphs. We show
by numerical simulations and analytical considerations how a very
simple Hamiltonian can lead to surprisingly complicated and
eventful phase diagram. 相似文献
4.
The decay rate for a particle in a metastable cubic potential is investigated in
the quantum regime by the Euclidean path integral method in
semiclassical approximation. The imaginary time formalism allows
one to monitor the system as a function of temperature. The family
of classical paths, saddle points for the action, is derived in
terms of Jacobian elliptic functions whose periodicity sets the
energy-temperature correspondence. The period of the classical
oscillations varies monotonically with the energy up to the
sphaleron, pointing to a smooth crossover from the quantum to the
activated regime. The softening of the quantum fluctuation
spectrum is evaluated analytically by the theory of the functional
determinants and computed at low T up to the crossover. In
particular, the negative eigenvalue, causing an imaginary
contribution to the partition function, is studied in detail by
solving the Lamè equation which governs the fluctuation
spectrum. For a heavvy particle mass, the decay rate shows a remarkable temperature dependence
mainly ascribable to a low lying soft mode and, approaching the
crossover, it increases by a factor five over the predictions of
the zero temperature theory. Just beyond the peak value, the
classical Arrhenius behavior takes over. A similar trend is found
studying the quartic metastable potential but the lifetime of the
latter is longer by a factor ten than in a cubic potential with
same parameters. Some formal analogies with noise-induced
transitions in classically activated metastable systems are
discussed. 相似文献
5.
M.A. Continentino J.C. Fernandes R.B. Guimar aes H.A. Borges A. Sulpice J.-L. Tholence J.L. Siqueira J.B.M. da Cunha C.A. dos Santos 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):613-618
The system Cu2FeO2BO3 is an oxyborate belonging to the family of the ludwigites. In this paper we present AC susceptibility, magnetization measurements
and M?ssbauer spectroscopy on this material which allows for a complete characterization of its complex magnetic behavior.
We find an hierarchy of interactions which clearly defines three regimes with decreasing temperature. These are associated
with, the freezing of the Fe moments, the antiferromagnetic ordering of the Cu sub-lattice and finally the coupling between
both systems.
Received 25 September 1998 相似文献
6.
M. S. Johansen P. Alstrom J. Borg M. T. Levinsen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):665-676
Significant statistical bias in LDA measurements and how to adequately deal with it is a subtle problem when dealing with
turbulent flows. In order to attempt a clarification we have performed measurements on a non-standard “grid experiment” where
a clear bias effect is found. We have investigated the effect of several corrective measures and find that best results, in
the sense of having the first moment converge to zero, are obtained when using the time between events as statistical weights.
The corrected time series have been used to check for extended self-similarity (ESS). Even though no scaling regime is seen
for the third moment and the flow certainly is neither isotropic nor homogeneous, perfect ESS scaling based on the absolute
third moment is observed up to the twelfth moment, extending into a time domain regime where the Taylor hypothesis of frozen
turbulence is obviously violated. Reversing the argument this indicates that the correction scheme needed can be experimentally
decided on using the criterion stated above and especially so if ESS is to be expected. Finally we have used the corrected
data to quantify the deviations from Gaussian behavior of the velocity difference probability density function for a weakly
turbulent flow. Through comparison with results on the Gaussian-Lorentzian distribution we find that the even part of the
experimental distribution can be reproduced quite well by a single-parameter family of distributions with second moment equal
unity.
Received 5 August 1998 and Received in final form 21 December 1998 相似文献
7.
A. Drăgulescu V.M. Yakovenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):585-589
Using tax and census data, we demonstrate that the distribution of individual income in the USA is exponential. Our calculated
Lorenz curve without fitting parameters and Gini coefficient 1/2 agree well with the data. From the individual income distribution,
we derive the distribution function of income for families with two earners and show that it also agrees well with the data.
The family data for the period 1947-1994 fit the Lorenz curve and Gini coefficient 3/8 = 0.375 calculated for two-earners
families.
Received 21 August 2000 相似文献
8.
W. Chin M. Mons I. Dimicoli F. Piuzzi B. Tardivel M. Elhanine 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):347-355
By using depopulation laser techniques, like IR-UV population labeling coupled to mass-selected R2PI detection, we confirm
that four tautomers are responsible for the near UV spectroscopy (310-280 nm) of guanine: two enol and two keto forms, each
pair having a 7NH and a 9NH form. Besides the UV spectroscopy of each tautomer, additional information on the excited state
nature and dynamics is obtained from fluorescence studies. In particular, the quenching of fluorescence beyond 285 nm, the
existence of a background absorption, as well as the existence of a strongly red-shifted component in the fluorescence emission
provides evidence for a strong electronic mixing in the excited state together with an efficient non-radiative process. The
details of these features are found to be tautomer-dependent. Comparison of the present results with literature data on other
purine molecules, like adenine or 9-substituted guanines, enables us to propose a new insight on the spectroscopy and dynamics
of the purine molecules. First, a large variability of the tautomer distribution in the gas phase is found within the purine
family, in particular a molecular change, as simple as a 9-methylation on guanine, can reduce the tautomer distribution to
a single species (enol form). Since the absorption spectrum is tautomer-dependent as well as substituent-dependent, it turns
out that the tautomer population is one of the major parameters that control the overall shape of the UV spectrum. Second,
the excited state model, often evoked in the literature, which involves electronic coupling between excited states of different
natures, namely ππ* and nπ* states, might account for the present fluorescence measurements on guanine, providing an extensive excited state electronic
mixing is assumed for these systems.
Received 24 June 2002 Published online 13 September 2002 相似文献
9.
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
10.
S. Giordano P. L. Palla L. Colombo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):29-35
We prove a generic theorem stating the equivalence
between a graded dielectric ellipsoid (with gradation along a family of
internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal
permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach
to homogenize dispersions of ellipsoidal graded particles. 相似文献
11.
G. Fagiolo M. Napoletano A. Roventini 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):205-211
This paper investigates the statistical properties of
within-country gross domestic product (GDP) and industrial
production (IP) growth-rate distributions. Many empirical
contributions have recently pointed out that cross-section growth
rates of firms, industries and countries all follow Laplace
distributions. In this work, we test whether also within-country,
time-series GDP and IP growth rates can be approximated by
tent-shaped distributions. We fit output growth rates with the
exponential-power (Subbotin) family of densities, which includes
as particular cases both Gaussian and Laplace distributions. We
find that, for a large number of OECD (Organization for Economic
Cooperation and Development) countries including the US, both
GDP and IP growth rates are Laplace distributed. Moreover, we show
that fat-tailed distributions robustly emerge even after
controlling for outliers, autocorrelation and heteroscedasticity. 相似文献
12.
M. A. Jafarizadeh M. Mahdian A. Heshmati K. Aghayar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(1):107-121
The three qubits mutually unbiased bases (MUB) diagonal density matrices with maximally entanglement in Greenberger-Horne-Zeilinger
(GHZ) basis are studied. These are a natural generalization of Bell-state diagonal density matrices. The linearity of positive
partial transpose (PPT) conditions allows one to specify completely PPT states or feasible region (FR) which form a polygon,
where the projection of the feasible region to some two dimensional planes has lead to better visualization. To reveal the
PPT entangled regions of these density matrices, we manipulate some appropriate optimal non-decomposable linear entanglement
witnesses (EWs) as the envelope of family of linear optimal non-decomposable EWs. These nonlinear EWs are nonlinear functional
of MUB diagonal states, so that they are nonnegative valued over all separable, but they are negative valued over some PPT
entangled MUB diagonal states. Even though, these nonlinear EWs can not separate completely, the PPT entanglement region from
separable one, but however in special cases they lead to necessary and sufficient condition for separability. To support the
evidence, we study three categories for special choices of parameters in density matrices, and using the nonlinear EWs we
can distinguish the region of PPT entangled states and separable states, completely. At the end some numerical simulations
are provided to show the practical applicability of these nonlinear EWs in detecting some PPT entangled MUB diagonal states. 相似文献
13.
Fangfang Fu Linghua Kong & Lan Wang 《advances in applied mathematics and mechanics.》2009,1(5):699-710
In this paper, we establish a family of symplectic integrators for a class
of high order Schrödinger equations with trapped terms. First, we find its symplectic structure and reduce it to a finite dimensional Hamilton system via spatial discretization.
Then we apply the symplectic Euler method to the Hamiltonian system.
It is demonstrated that the scheme not only preserves symplectic geometry structure
of the original system, but also does not require to resolve coupled nonlinear
algebraic equations which is different from the general implicit symplectic schemes.
The linear stability of the symplectic Euler scheme and the errors of the numerical
solutions are investigated. It shows that the semi-explicit scheme is conditionally
stable, first order accurate in time and $2l^{th}$ order accuracy in space. Numerical tests
suggest that the symplectic integrators are more effective than non-symplectic ones,
such as backward Euler integrators. 相似文献
14.
H. Lavička F. Slanina 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):53-63
The Minority Game is adapted to study the “imitation dilemma”,
i.e. the tradeoff between local benefit and global harm coming from
imitation. The agents are placed on a substrate network and are
allowed to imitate more successful neighbours. Imitation domains, which are
oriented trees, are formed. We investigate size distribution of the
domains and in-degree distribution within the trees. We use four types of
substrate: one-dimensional chain; Erd?s-Rényi graph;
Barabási-Albert scale-free graph; Barabási-Albert 'model A'
graph. The behaviour of some features of the imitation network strongly
depend on the information cost epsilon,
which is the percentage of gain the
imitators must pay to the imitated. Generally, the system tends to
form a few domains of equal size. However, positive epsilon makes
the system stay in a long-lasting metastable state with complex
structure. The in-degree distribution is found to follow a power law
in two cases of those studied: for Erd?s-Rényi substrate for any
epsilon and for Barabási-Albert scale-free substrate for large
enough epsilon. A brief comparison with empirical data is provided. 相似文献
15.
C.-S. Yu H.-S. Song 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):147-151
In this paper, an intuitive approach is employed to
generalize the full separability criterion of tripartite quantum
states of qubits to the higher-dimensional systems [Phys. Rev. A
72, 022333 (2005)]. A distinct characteristic of the
present generalization is that less restrictive conditions are
needed to characterize the properties of full separability.
Furthermore, the formulation for pure states can be conveniently
extended to the case of mixed states by utilizing the Kronecker
product approximate technique. As applications, we give the analytic
approximation of the criterion for weakly mixed tripartite quantum
states and investigate the full separability of some weakly mixed
states. 相似文献
16.
A. Pai S. V. Dhurandhar P. Hello J. -Y. Vinet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):333-346
The large scale interferometric gravitational wave detectors consist of Fabry-Perot cavities operating at very high powers
ranging from tens of kW to MW for next generations. The high powers may result in several nonlinear effects which would affect
the performance of the detector. In this paper, we investigate the effects of radiation pressure, which tend to displace the
mirrors from their resonant position resulting in the detuning of the cavity. We observe a remarkable effect, namely, that
the freely hanging mirrors gain energy continuously and swing with increasing amplitude. It is found that the “time delay”,
that is, the time taken for the field to adjust to its instantaneous equilibrium value, when the mirrors are in motion, is
responsible for this effect. This effect is likely to be important in the optimal operation of the full-scale interferometers
such as VIRGO and LIGO.
Received 12 July 1999 相似文献
17.
We develop a theory for shrinkage dynamics of a vesicle interacting with surfactant molecules. A stepwise shrinkage is formulated
in such a way that it consists of two processes. One is a nucleation process of a pore under increasing of the membrane tension.
The other is a closure process of the pore due to the line tension of the pore edge after leakage of the inner fluid. We carry
out numerical simulations and show that the results agree with experiments semi-quantitatively. An analytical study is also
carried out to understand the periodic shrinkage. 相似文献
18.
L.I. Salminen M.J. Alava K.J. Niskanen 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,37(3):369-374
A differential cluster variation method (DCVM) is proposed for analysis of spinoidal decomposition in alloys. In this method, lattice symmetry operations in the presence of an infinitesimal composition gradient are utilized to deduce the connection equations for the correlation functions and to reduce the number of independent variables in the cluster variation analysis. Application of the method is made to calculate the gradient energy coefficient in the Cahn-Hilliard free energy function and the fastest growing wavelength for spinodal decomposition in Al-Li alloys. It is shown that the gradient coefficient of congruently ordered Al-Li alloys is much larger than that of the disordered system. In such an alloy system, the calculated fastest growing wavelength is approximately 10 nm, which is an order of magnitude larger than the experimentally observed domain size. This may provide a theoretical explanation why spinodal decomposition after a congruent ordering is dominated by the antiphase boundaries.Received: 17 November 2003, Published online: 2 April 2004PACS:
64.75. + g Solubility, segregation, and mixing; phase separation - 81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations - 05.70.Ln Nonequilibrium and irreversible thermodynamics 相似文献
19.
F. Slanina 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):225-240
Far-from-equilibrium models of interacting particles in one dimension
are used as a basis for modelling the stock-market
fluctuations. Particle types and their positions are interpreted as
buy and sel orders placed on a price axis in the order book. We
revisit some modifications of well-known models, starting with the
Bak-Paczuski-Shubik model. We look at the four decades old Stigler
model and investigate its variants. One of them is the simplified
version of the Genoa artificial market. The list of studied models is
completed by the models of Maslov and Daniels et al. Generically, in
all cases we
compare the return distribution, absolute return autocorrelation and
the value of the Hurst exponent. It turns out that none of the models
reproduces satisfactorily all the empirical data, but the most promising
candidates for further development are the Genoa artificial market and
the Maslov model with moderate order evaporation. 相似文献
20.
R. Capovilla C. Chryssomalakos J. Guven 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):163-166
We examine the equilibria of a rigid loop in the plane, characterized by an energy functional quadratic in the curvature,
subject to the constraints of fixed length and fixed enclosed area. Whereas the only non self-intersecting equilibrium corresponding
to the fixed length constraint is the circle, the area constraint gives rise to distinct equilibria labeled by an integer.
These configurations exhibit self-intersections and bifurcations as the area is reduced. In addition, not only can the Euler-Lagrange
equation be integrated to provide a quadrature for the curvature but the embedding itself can be expressed as a local function
of the curvature. Perturbations connecting equilibria are shown to satisfy a first order ODE which is readily solved. Analytical
expressions for the energy as a function of the area are obtained in the limiting regimes.
Received 18 October 2001 / Received in final form 31 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: capo@fis.cinvestav.mx
RID="b"
ID="b"e-mail: chryss@nuclecu.unam.mx
RID="c"
ID="c"e-mail: jemal@nuclecu.unam.mx 相似文献