共查询到20条相似文献,搜索用时 15 毫秒
1.
O. Chanal B. Chabaud B. Castaing B. Hébral 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):309-317
We analyse experimental velocity measurements on the axis of a low temperature gaseous helium jet. From independent increments
arguments, we reproduce the behaviour of structure functions. We show where this approach fails and how the intermittency
phenomenon is a small correction. The physical arguments under the multiplicative cascade models for this intermittency imply
an acceleration of this cascade close to the dissipative range, which we are able to evidence. This acceleration could be
responsible of the apparent Extended Self Similarity between structure functions of various orders.
Received 13 October 1999 and Received in final form 19 May 2000 相似文献
2.
L. Benfatto A. Perali C. Castellani M. Grilli 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):609-612
We evaluate the charge and spin susceptibilities of the 2D attractive Hubbard model and we compare our results with Monte
Carlo simulations on the same model. We discuss the possibility to include topological Kosterlitz-Thouless superconducting
fluctuations in a standard perturbative approach substituting in the fluctuation propagator the Ginzburg-Landau correlation
length with the Kosterlitz-Thouless correlation length.
Received 30 June 1999 相似文献
3.
Using the Lie algebraic approach we have derived the exact diffusion propagator of the Fokker-Planck equation with a time-dependent
variable diffusion coefficient and a time-dependent mean-reverting force between two absorbing boundaries. The exact diffusion
propagator not only enables us to study the time evolution of the corresponding stochastic system, but the knowledge of the
propagator can also provide a benchmark for testing approximate numerical or analytical procedures. Furthermore, the Lie algebraic
method is very simple and could be easily extended to the more general Fokker-Planck equations with well-defined algebraic
structures.
Received 18 December 2002 / Received in final form 3 March 2003 Published online 24 April 2003 相似文献
4.
5.
B. Dubrulle 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):757-771
We develop a new approach to scale symmetry, which takes into account the possible finite cut-offs of the fields or the parameters.
This new symmetry, called finite size scale symmetry: i) includes the traditional self-similarity as a limiting case, when
the cut-offs are set to infinity (infinite size-system); ii) is consistent with the traditional finite size scaling approach
already used in critical phenomena; iii) enables the computation of some of the universal functions appearing in the finite
size scaling formulation; iv) allows scale transformations leaving the cut-offs invariant, like in the traditional renormalization
approach; v) can be formulated to allow for positive or negative fields and parameters; vi) leads to new predictions about
the shape of some distributions in critical phenomena or turbulence which are in very good agreement with the experimental
or numerical findings.
Received 26 January 1999 and Received in final form 25 October 1999 相似文献
6.
T. Temesvári C. De Dominicis I. Kondor 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):629-634
Replica field theory for the Ising spin glass in zero magnetic field is studied around the upper critical dimension d=6. A scaling theory of the spin glass phase, based on Parisi's ultrametrically organised order parameter, is proposed. We
argue that this infinite step replica symmetry broken (RSB) phase is nonperturbative in the sense that amplitudes of scaling
forms cannot be expanded in term of the coupling constant w2. Infrared divergent integrals inevitably appear when we try to compute amplitudes perturbatively, nevertheless the -expansion of critical exponents seems to be well-behaved. The origin of these problems can be traced back to the unusual
behaviour of the free propagator having two mass scales, the smaller one being proportional to the perturbation parameter
w2 and providing a natural infrared cutoff. Keeping the free propagator unexpanded makes it possible to avoid producing infrared
divergent integrals. The role of Ward-identities and the problem of the lower critical dimension are also discussed.
Received 23 December 1998 and Received in final form 23 March 1999 相似文献
7.
R. Folman J. Schmiedmayer H. Ritsch D. Vitali 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):93-107
Following almost a century of debate on possible “independent of measurement" elements of reality, or “induced" elements of
reality - originally invoked as an ad-hoc collapse postulate, we propose a novel line of interference experiments which may be able to examine the regime of induced
elements of reality. At the basis of the proposed experiment, lies the hypothesis that models of “induced" elements of reality
should exhibit symmetry breaking within quantum evolution. The described symmetry experiment is thus aimed at being able to detect and resolve spatial symmetry breaking signatures. The proposed experiment stands at
the edge of present day technological abilities and will be, so we believe, realizable in the near future.
Received 2 December 1999 and Received in final form 6 April 2000 相似文献
8.
S.S. Wu J.M. Zhu K.Z. Liu Y.J. Yao 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):345-349
A new effect of self-consistency in the relativistic Hartree-Fock (HF) approximation is studied by a simple model and a renormalized
calculation. A comparison is made between two different HF schemes: one requiring self-consistency in the HF potential (scheme
P) and the other in the baryon propagator (scheme BP). Our results show that scheme P is a good aproximation to scheme BP
for the calculation of the baryon propagator and the self-consistency requirements make the results obtained by the two schemes
closer to each other, because the self-consistency in scheme BP diminishes the continuum part of the spectral representation
for the baryon propagator, while the self-consistency in scheme P yields a baryon propagator which approximates closely to
the HF result contributed by the converged single particle part of the above spectral representation alone.
Received: 12 March 1999 / Revised version: 6 September 1999 相似文献
9.
E.G. Thrapsaniotis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):43-47
In the present paper we consider the case of an electron under the presence of a single mode field in a cavity linearly polarized
in the z-direction. We adopt the dipole approximation and we derive the full propagator of the electron. In the present case we suppose
that the field is in a coherent state. The parameters of the propagator involve Mathieu functions. Finally we extract the
time evolution of an initially Gaussian wavepacket and its probability density. The present theory is applicable to the interaction
of strong fields with atoms.
Received 17 March 2000 and Received in final form 19 December 2000 相似文献
10.
S. Roux J.F. Muzy A. Arneodo 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):301-322
Swirling turbulent flows display intermittent pressure drops associated with intense vorticity filaments. Using the wavelet
transform modulus maxima representation of pressure fluctuations, we propose a method of characterizing these pressure drop
events from their time-scale properties. This method allows us to discriminate fluctuations induced by just formed (young)
as well as by burst (old) filaments from background pressure fluctuations. The statistical characteristics of these filaments
(core size, waiting time) are analyzed in details and compared with previously reported experimental and numerical findings.
Their intermittent occurrence is found to be governed by a pure Poisson's law, the hallmark of independent events. Then we
apply the wavelet transform modulus maxima (WTMM) method to the background pressure fluctuations. This study reveals that,
once removed all the filaments, the “multifractal” nature of pressure fluctuations still persists. This is a clear indication
that the statistical contribution of the filaments is not important enough to account for the intermittency phenomenon in
turbulents flows.
Received 27 July 1998 and Received in final form 23 November 1998 相似文献
11.
G. Chanfray D. Davesne M. Ericson M. Martini 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):191-198
We study the two-pion propagator in the nuclear medium. This quantity appears in the ππ T-matrix and we show that it also enters the QCD scalar susceptibility. The medium effects on this propagator are due to the
influence of the individual nucleon response to a scalar field through their pion clouds. This response is appreciably increased
by the nuclear environment. It produces an important convergence effect between the scalar and pseudoscalar susceptibilities,
reflecting the reshaping of the scalar strength observed in 2π production experiments. While a large modifications of the
σ propagator follows, due to its coupling to two pion states, we show that the NN potential remains instead unaffected. 相似文献
12.
We present a generalization of the multiplicative model for velocity increments involving an affine process. The consequences
on the shape of the probability distribution functions for the velocity increments are explored, and shown to be better compatible
with the existence of a scale variation of the skewness.
Received 29 March 1999 and Received in final form 14 September 1999 相似文献
13.
D. Braun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):3-12
I investigate the propagator of the Wigner function for a dissipative chaotic quantum map. I show that a small amount of dissipation
reduces the propagator of sufficiently smooth Wigner functions to its classical counterpart, the Frobenius-Perron operator,
if . Several consequences arise: the Wigner transform of the invariant density matrix is a smeared out version of the classical
strange attractor; time dependent expectation values and correlation functions of observables can be evaluated via hybrid quantum-classical formulae in which the quantum character enters only via the initial Wigner function. If a classical phase-space distribution is chosen for the latter or if the map is iterated sufficiently
many times the formulae become entirely classical, and powerful classical trace formulae apply.
Received 7 October 1999 相似文献
14.
On the properties of small-world network models 总被引:7,自引:0,他引:7
A. Barrat M. Weigt 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):547-560
We study the small-world networks recently introduced by Watts and Strogatz [Nature 393, 440 (1998)], using analytical as well as numerical tools. We characterize the geometrical properties resulting from the
coexistence of a local structure and random long-range connections, and we examine their evolution with size and disorder
strength. We show that any finite value of the disorder is able to trigger a “small-world” behaviour as soon as the initial
lattice is big enough, and study the crossover between a regular lattice and a “small-world” one. These results are corroborated
by the investigation of an Ising model defined on the network, showing for every finite disorder fraction a crossover from
a high-temperature region dominated by the underlying one-dimensional structure to a mean-field like low-temperature region.
In particular there exists a finite-temperature ferromagnetic phase transition as soon as the disorder strength is finite.
[0.5cm]
Received 29 March 1999 and Received in final form 21 May 1999 相似文献
15.
H. Willaime J. Maurer F. Moisy P. Tabeling 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):363-369
Turbulence produced in low temperature helium gas flowing over arrays of rectangular- and triangular-shaped blunt obstacles
is investigated experimentally. The set-up allows both low fluctuation rates (down to 8%), and high microscale Reynolds numbers,
(up to 1 150). The forced Kolmogorov equation is found to apply accurately. Similar to another flow configuration (counter
rotating flow case [1]), the analysis of the flatness factor evolution with the Reynolds number reveals a transitional behavior
around 650.
Received 26 August 1999 and Received in final form 28 August 2000 相似文献
16.
A. Bershadskii T. Nakano D. Fukayama T. Gotoh 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):95-101
Using results of a direct numerical simulation (DNS) of 3D turbulence we show that the observed generalized scaling (i.e. scaling moments versus moments of different orders) is consistent with a lognormal-like distribution of turbulent energy dissipation fluctuations
with moderate amplitudes for all space scales available in this DNS (beginning from the molecular viscosity scale up to largest ones). Local multifractal thermodynamics has been developed to interpret the data obtained using the generalized scaling, and a new interval
of space scales with inverse cascade of generalized energy has been found between dissipative and inertial intervals of scales
for sufficiently large values of the Reynolds number.
Received 21 July 2000 相似文献
17.
18.
B. Castaing 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):357-358
Usual turbulence experiments, based on the Taylor hypothesis, differ from true Eulerian measurements. This is the origin of
the apparent discrepancy between a recent two point correlation analysis and the multiplicative cascade picture. Indeed, both
Eulerian and Lagrangian observations perfectly agree with this picture.
Received 19 June 2002 / Received in final form 29 July 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: bcastain@ens-lyon.fr 相似文献
19.
P.B. Slater 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):471-480
In previous studies, we have explored the ansatz that the volume elements of the Bures metrics over quantum systems might serve as prior distributions, in analogy with the (classical) Bayesian role of the volume elements (“Jeffreys' priors”) of Fisher information metrics. Continuing this work, we obtain exact Bures prior probabilities that the members of certain low-dimensional subsets of the fifteen-dimensional convex set of density matrices are separable or classically correlated. The main analytical tools employed are symbolic integration and a formula of Dittmann (J. Phys. A 32, 2663 (1999)) for Bures metric tensors. This study complements an earlier one (J. Phys. A 32, 5261 (1999)) in which numerical (randomization) - but not integration - methods were used to estimate Bures separability probabilities for unrestricted
and density matrices. The exact values adduced here for pairs of quantum bits (qubits), typically, well exceed the estimate () there, but this disparity may be attributable to our focus on special low-dimensional subsets. Quite remarkably, for the
q= 1 and states inferred using the principle of maximum nonadditive (Tsallis) entropy, the Bures probabilities of separability are
both equal to . For the Werner qubit-qutrit and qutrit-qutrit states, the probabilities are vanishingly small, while in the qubit-qubit case it is .
Received 10 December 1999 and Received in final form 24 February 2000 相似文献
20.
U. Tirnakli D.F. Torres 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):691-698
We develop an analytical technique to derive explicit forms of thermodynamical quantities within the asymptotic approach to
non-extensive quantum distribution functions. Using it, we find an expression for the number of particles in a boson system
which we compare with other approximate scheme (i.e. factorization approach), and with the recently obtained exact result. To do this, we investigate the predictions on Bose-Einstein
condensation and the blackbody radiation. We find that both approximation techniques give results similar to (up to ) the exact ones, making them a useful tool for computations. Because of the simplicity of the factorization approach formulae,
it appears that this is the easiest way to handle with physical systems which might exhibit slight deviations from extensivity.
Received 19 August 1999 and Received in final form 1 November 1999 相似文献