共查询到20条相似文献,搜索用时 31 毫秒
1.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
2.
Blinking of single molecules and nanocrystals is modeled as a two-state renewal process with on (fluorescent) and off (non-fluorescent)
states. The on and off-times may have power-law or exponential distributions. A fractional generalization of the exponential
function is used to develop a unified treatment of the blinking statistics for both types of distributions. In the framework
of the two-state model, an equation for the probability density p(t
on|t) of the total on-time is derived. As applied to power-law blinking, the equation contains derivatives of fractional orders
α and β equal to the exponents of the on and off-time power-law distributions, respectively. In the limit case of α = β =
1, the distributions become exponential and the fractional differential equation reduces to an integer order differential
equation. Solutions to these equations are expressed in terms of fractional stable distributions. The Poisson transform of
p(t
on|t) is the photon number distribution that determines the photon counting statistics. It is shown that the long-time asymptotic
behavior of Mandel’s Q parameter follows a power law: M(t) ∝ t
γ
. The function γ(α, β) is defined on the (α, β) plane. An analysis of the relative variance of the total on-time shows that it decays only
when α = β = 1 or α < β. Otherwise, relative fluctuations either exhibit asymptotic power-law growth or approach a constant
level. Analytical calculations are in good agreement with the results of Monte Carlo simulations. 相似文献
3.
A variational approach is developed for bound state calculations in three- and four-electron atomic systems. This approach
can be applied to determine, in principle, an arbitrary bound state in three- and four-electron ions and atoms. Our variational
wave functions are constructed from four- and five-body Gaussoids that respectively depend on six (r
12, r
13, r
14, r
23, r
24, r
34) and ten (r
12, r
13, r
14, r
15, r
23, r
24, r
25, r
34, r
35 and r
45) relative coordinates. The approach allows operating with the more than one electron spin functions. In particular, the trial
wave functions for the 1
S states in four-electron atomic systems include the two independent spin functions χ1 = αβαβ + βαβα − βααβ − αββα and χ2 = 2ααββ + 2ββαα − βααβ − αββα − βαβα − αβαβ. We also discuss the construction of variational wave functions for the excited
23
S states in four- electron atomic systems. 相似文献
4.
A. Hader A. Memsouk Y. Boughaleb 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):315-319
We have studied the scaling properties of diffusion fronts by numerical calculations based on the mean field approach in the
context of a lattice gas model, performed in a triangular lattice. We find that the height-height correlation function scales
with time t and length l as C(l, t) ≈l
α
f (t/l
α/β) with α = 0.62±0.01 and β = 0.39±0.02. These exponent values are identical to those characterising the roughness of the diffusion
fronts evolving through a square lattice [1,2], thus confirming their universality.
Received 14 November 2001 / Received in final form 20 April 2002 Published online 31 July 2002 相似文献
5.
M. Modarres M. M. Yazdanpanah F. Zolfagharpour 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):327-333
The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α
p(E
0+) = + 3.2, α
n(E
0+) = + 4.1, the t-channel α
t
p, n = - β
t
p, n = + 7.6 and the resonant β
p, n(P
33(1232)) = + 8.3 contributions (in units of 10-4fm^3). The remaining deviations from the experimental data Δα
p = 1.2±0.6, Δβ
p = 1.2±0.6, Δα
n = 0.8±1.7 and Δβ
n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions.
This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms
of two-photon coupling to the σ-meson having the predicted mass m
σ
= 666MeV and two-photon width Γ
γγ
= 2.6keV. 相似文献
6.
I.?Lon?arevi? Z. M.?Jak?i? S. B.?Vrhovac Lj.?Budinski-Petkovi? 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):439-445
Random sequential adsorption with diffusional relaxation of extended objects
both on a one-dimensional and planar triangular lattice is studied numerically
by means of Monte Carlo simulations. We focus our attention on the behavior of
the coverage θ(t) as a function of time. Our results indicate that the
lattice dimensionality plays an important role in the present model.
For deposition of k-mers on 1D lattice with diffusional relaxation, we found
that the growth of the coverage θ(t) above the jamming limit to the
closest packing limit θCPL is described by the pattern
θCPL-θ(t) ∝Eβ[-(t/τ)β], where Eβ
denotes the Mittag-Leffler function of order β∈(0,1). In the case of
deposition of extended lattice shapes in 2D, we found that after the initial
“jamming", a stretched exponential growth of the coverage θ(t) towards
the closest packing limit θCPL occurs, i.e., θCPL -
θ(t) ∝exp [-(t/τ)β]. For both cases we observe that: (i)
dependence of the relaxation time τ on the diffusion probability Pdif
is consistent with a simple power-law, i.e., τ∝Pdif
-δ;
(ii) parameter β depends on the object size in 1D and on the particle
shape in 2D. 相似文献
7.
V. P. Ruban 《Journal of Experimental and Theoretical Physics》2010,111(5):776-785
We consider slow, compared to the speed of sound, motions of an ideal compressible fluid (gas) in a gravitational field in
the presence of two isentropic layers with a small specific-entropy difference between them. Assuming the flow to be potential
in each of the layers (v
1, 2 = ▿ϕ1, 2) and neglecting the acoustic degrees of freedom (div($
\bar \rho
$
\bar \rho
(z)▿ϕ1, 2) ≈ 0, where $
\bar \rho
$
\bar \rho
(z) is the average equilibrium density), we derive the equations of motion for the boundary in terms of the shape of the surface
z = η(x, y, t) itself and the difference between the boundary values of the two velocity field potentials: ψ(x, y, t) = ψ1 − ψ2. We prove the Hamilto nian structure of the derived equations specified by a Lagrangian of the form ℒ = ∫$
\bar \rho
$
\bar \rho
(η)η
t
ψdxdy − ℋ{η, ψ}. The system under consideration is the simplest theoretical model for studying internal waves in a sharply stratified
atmosphere in which the decrease in equilibrium gas density due to gas compressibility with increasing height is essentially
taken into account. For plane flows, we make a generalization to the case where each of the layers has its own constant potential
vorticity. We investigate a system with a model dependence $
\bar \rho
$
\bar \rho
(z) ∝ e
−2αz
with which the Hamiltonian ℋ{η, ψ} can be represented explicitly. We consider a long-wavelength dynamic regime with dispersion
corrections and derive an approximate nonlinear equation of the form u
t
+ auu
x
− b[−$
\hat \partial _x^2
$
\hat \partial _x^2
+ α2]1/2
u
x
= 0 (Smith’s equation) for the slow evolution of a traveling wave. 相似文献
8.
The results of numerical analysis of the Brownian movement of a particle in the force field of the potential corresponding
to interacting subcritical and supercritical phase transitions are considered. If the white noise intensity corresponds to
the critical intensity of the noise-induced transition, the system of stochastic differential equations describes random steady-state
processes with fluctuation power spectra inversely proportional to frequency f, S(f) ∼ 1/f
α, where exponent α varies in the interval 0.8 ≤ α ≤ 1.8. Exponent β of distribution function P(τ) ∼ τ−β for the duration of low-frequency extremal fluctuations, which are analogous to avalanches considered in the models of self-organized
criticality in many respects, varies between the same limits. It is shown that exponents α and β are connected through the
relation α + β = 2. 相似文献
9.
The heavy-fermion metal CePd1−x
Rh
x
can be tuned from ferromagnetism at x = 0 to the nonmagnetic state at some critical concentration x
c
. The non-Fermi liquid behavior (NFL) at x ≃ x
c
is recognized by the power-law dependence of the specific heat C(T) given by the electronic contribution susceptibility X(T) and volume expansion coefficient α(T) at low temperatures: C/T ∝ X(T) ∝ α(T)/T∝ 1/ √T. We also demonstrate that the behavior of the normalized effective mass M
N
*
observed in CePd1−x
Rh
x
at x ≃ 0.8 agrees with that of M
N
*
observed in paramagnetic CeRu2Si2 and conclude that these alloys exhibit the universal NFL thermodynamic behavior at their quantum critical points. We show
that the NFL behavior of CePd1−x
Rh
x
can be accounted for within the frameworks of the quasiparticle picture and fermion condensation quantum phase transition,
while this alloy exhibits a universal thermodynamic NFL behavior that is independent of the characteristic features of the
given alloy such as its lattice structure, magnetic ground state, dimension, etc.
The text was submitted by the authors in English. 相似文献
10.
E. Gotsman E. Levin U. Maor J. S. Miller 《The European Physical Journal C - Particles and Fields》2008,57(4):689-709
In this paper we develop an approach to soft scattering processes at high energies which is based on two elements: the Good–Walker
mechanism for low mass diffraction and multi-pomeron interactions for high mass diffraction. The principal idea, which allows
us to specify the theory for pomeron interactions, is that the so called soft processes occur at rather short distances (r
2
∝1/〈p
t
〉2
∝
α′ℙ≈0.01 GeV−2), where perturbative QCD is valid. The value of the pomeron slope α′ℙ is obtained from a fit to the experimental data. Using this theoretical approach, we suggest a model that fits all soft data
in the ISR-Tevatron energy range: total, elastic, single and double diffractive cross sections, as well as the t dependence of the differential elastic cross section, and the mass dependence of single diffraction. In this model we calculate
the survival probability of diffractive Higgs production, and we obtain a value for this observable that is smaller than 1%
at the LHC energy range. 相似文献
11.
G. Migliorini V.G. Rostiashvili T.A. Vilgis 《The European physical journal. E, Soft matter》2001,4(4):475-487
A variational approach is considered to calculate the free energy and the conformational properties of a polyelectrolyte chain
in d dimensions. We consider in detail the case of pure Coulombic interactions between the monomers, when screening is not present,
in order to compute the end-to-end distance and the asymptotic properties of the chain as a function of the polymer chain
length N. We find R≃N
ν(log N)γ, where ν = and λ is the exponent which characterizes the long-range interaction U∝ 1/r
λ. The exponent γ is shown to be non-universal, depending on the strength of the Coulomb interaction. We check our findings
by a direct numerical minimization of the variational energy for chains of increasing size 24 < N < 215. The electrostatic blob picture, expected for small enough values of the interaction strength, is quantitatively described
by the variational approach. We perform a Monte Carlo simulation for chains of length 24 < N < 210. The non-universal behavior of the exponent γ previously derived within the variational method is also confirmed by the simulation
results. Non-universal behavior is found for a polyelectrolyte chain in d = 3 dimension. Particular attention is devoted to the homopolymer chain problem, when short-range contact interactions are
present.
Received 8 August 2000 and Received in final form 19 December 2000 相似文献
12.
E. Bogomolny U. Gerland C. Schmit 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):121-132
We propose a plasma model for spectral statistics displaying level repulsion without long-range spectral rigidity, i.e. statistics intermediate between random matrix and Poisson statistics similar to the ones found numerically at the critical
point of the Anderson metal-insulator transition in disordered systems and in certain dynamical systems. The model emerges
from Dysons one-dimensional gas corresponding to the eigenvalue distribution of the classical random matrix ensembles by restricting
the logarithmic pair interaction to a finite number k of nearest neighbors. We calculate analytically the spacing distributions and the two-level statistics. In particular we
show that the number variance has the asymptotic form Σ2(L) ∼χL for large L and the nearest-neighbor distribution decreases exponentially when s→∞, P(s) ∼ exp(- Λs) with Λ = 1/χ = kβ + 1, where β is the inverse temperature of the gas (β = 1, 2 and 4 for the orthogonal, unitary and symplectic symmetry class
respectively). In the simplest case of k = β = 1, the model leads to the so-called Semi-Poisson statistics characterized by particular simple correlation functions
e.g.
P(s) = 4s exp(- 2s). Furthermore we investigate the spectral statistics of several pseudointegrable quantum billiards numerically and compare
them to the Semi-Poisson statistics.
Received 13 September 2000 相似文献
13.
F. Clementi M. Gallegati G. Kaniadakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):187-193
Starting from the generalized exponential function
, with exp 0(x)=exp (x), proposed in reference [G. Kaniadakis, Physica A 296, 405 (2001)], the survival function P>(x)=exp κ(-βxα), where x∈R+, α,β>0, and
, is considered in order to analyze the data on personal income distribution for Germany, Italy, and the United Kingdom. The
above defined distribution is a continuous one-parameter deformation of the stretched exponential function P>
0(x)=exp (-βxα)
to which reduces as κ approaches zero
behaving in very different way in the x→0 and x→∞ regions. Its bulk is very close to the stretched exponential one, whereas
its tail decays following the power-law P>(x)∼(2βκ)-1/κx-α/κ. This makes the κ-generalized function particularly suitable to describe simultaneously the income distribution among both
the richest part and the vast majority of the population, generally fitting different curves. An excellent agreement is found
between our theoretical model and the observational data on personal income over their entire range. 相似文献
14.
P. Descouvemont 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):413-419
The 9Be and 9B nuclei are investigated in a microscopic three-cluster model involving α + α +
n (or α + α +
p) configurations. The 8Be (0
+
, 2
+
) +
n and 5He (3/2
-
, 1/2
-
) + α (or mirror) channels are included by taking account of the unstable nature of 8Be and 5He. Spectroscopic properties of 9Be and 9B are analyzed. We show that the 5He + α configurations cannot be neglected to derive accurate results. The 9Be(γ,αα)n photodisintegration cross-section is shown to be mainly determined by 8Be + n channels at low energies, but 5He + α channels become important beyond E
γ≈ 4 MeV.
Received: 7 September 2001 / Accepted: 19 November 2001 相似文献
15.
D. Dantchev 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(2):211-219
The behavior of the bulk two-point correlation function G(;T| d ) in d-dimensional system with van der Waals type interactions is investigated and its consequences on the finite-size scaling properties
of the susceptibility in such finite systems with periodic boundary conditions is discussed within mean-spherical model which
is an example of Ornstein and Zernike type theory. The interaction is supposed to decay at large distances r as r
- (d + σ), with 2 < d < 4, 2 < σ < 4 and d + σ≤6. It is shown that G(;T| d ) decays as r
- (d - 2) for 1 ≪r≪ξ, exponentially for ξ≪r≪r
*, where r
* = (σ - 2)ξlnξ, and again in a power law as r
- (d + σ) for r≫r
*. The analytical form of the leading-order scaling function of G(;T| d ) in any of these regimes is derived.
Received 28 May 2001 相似文献
16.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
17.
Summary Within the generalized equilibrium statistics recently introduced by Tsallis (p
n
∝[1−β(q−-1)
εn
]1/(q−)), we calculate the thermal dependence of the specific heat corresponding to a harmonic-oscillator-like spectrum, namely ε
n
ω(n−α) (∀ω>0,n=0,1,2,...). The influences ofq and α are exhibited. Physically inaccessible and/or thermally frozen gaps are obtained in the low-temperature region, and,
forq>1, oscillations are observed in the high-temperature region. The specific heat of the two-level system is also shown. 相似文献
18.
L. Bartosch P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):29-36
We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals
for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions
to the average DOS via a simple gauge-transformation. If σ(ω) > 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e
4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω
2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω
1)1/2exp(- Ω
1/|ω|) at T = 0, where Ω
1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance
that can be compared with experiments.
Received 28 August 2001 / Received in final form 28 January 2002 Published online 9 July 2002 相似文献
19.
Benjamin Lindner 《Journal of statistical physics》2008,130(3):523-533
Nonequilibrium biological systems like moving cells or bacteria have been phenomenologically described by Langevin equations
of Brownian motion in which the friction function depends on the particle’s velocity in a nonlinear way. An important subclass
of such friction functions is given by power laws, i.e., instead of the Stokes friction constant γ
0 one includes a function γ(v)∼v
2α
. Here I show using a recent analytical result as well as a dimension analysis that the diffusion coefficient is proportional
to a simple power of the noise intensity D like D
(1−α)/(1+α) (independent of spatial dimension). In particular the diffusion coefficient does not depend on the noise intensity at all,
if α=1, i.e., for a cubic friction F
fric=−γ(v)v∼v
3. The exact prefactor is given in the one-dimensional case and a fit formula is proposed for the multi-dimensional problem.
All results are confirmed by stochastic simulations of the system for α=1, 2, and 3 and spatial dimension d=1, 2, and 3. Conclusions are drawn about the strong noise behavior of certain models of self-propelled motion in biology. 相似文献
20.
The kinetics of recombination of electrons and acceptor-bound holes in AlGaAs-GaAs heterostructure obey a single-exponential
decay in the liquid phase of 2D electrons, whereas localization gives rise to a broad spectrum of recombination rates, especially
in the magnetic freeze-out regime. This results in a power-law dependence I(t)∝(τ/t)α in the tail of the recombination kinetics, with the universal exponent α=(1−ν)−1 at ν<1 for all the samples examined experimentally in this work.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 118–122 (25 January 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献