共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Residori N. Olivi-Tran E. Pampaloni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):15-20
In the case of 2D optical patterns, frustration comes from the interplay between the physical constraints (light-matter interaction)
and the geometrical constraints (cavity length and structure). Depending on the dynamical parameters, we are able to single
out two distinct behaviors. For small diffusion and close to threshold, the system is forced to fulfill the geometrical constraints
giving rise to a phase dynamics of quasicrystals. For larger diffusion, the system fragmentates into spatial domains giving
rise to a competition between different patterns. By means of a geometrical argument, we show that the spatial distribution
of domains is related to the symmetry imposed by the geometrical constraint and that the domain borders are disinclination
defects. These defects being the nucleation centers of spatial domains, they trigger the onset of pattern competition.
Received 27 December 1999 and Received in final form 29 March 2000 相似文献
2.
M. Genovese C. Novero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):109-113
We propose a quantum transmission based on bi-photons, which are doubly-entangled both in polarisation and phase. This scheme
finds a natural application in quantum cryptography, where we show that an eventual eavesdropper is bound to introduce a larger
error on the quantum communication than for a single entangled bi-photon communication, when he steels the same information.
Received 23 July 2001 / Received in final form 30 November 2001 Published online 24 September 2002 相似文献
3.
S. Longhi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):57-66
Multiphase patterns are found in a mean-field model of a singly-resonant optical parametric oscillator that converts a pump
field at frequency 3ω into signal and idler fields at frequencies 2ω and ω. A complex Ginzburg-Landau equation without diffusion
and with a quadratic phase-sensitive nonlinear term is derived under single-longitudinal and paraxial propagation approximations.
Owing to the phase-matched multistep parametric process ω + ω = 2ω, phase locking of the resonated signal field is possible
with three distinct phase states. Three-armed rotating spirals, target patterns and light filamentation are found by a numerical
analysis of the mean-field equation.
Received 19 April 2001 and Received in final form 21 June 2001 相似文献
4.
T.W. Carr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):245-255
We consider the deterministic dynamics of a semiconductor laser with saturable absorber that is subject to delayed optical
feedback. Alone, both the saturable absorber and delayed feedback cause the CW output to become unstable to periodic output
via Hopf bifurcations. We examine the combined effects of these two destabilizing mechanisms to determine new conditions for
the Hopf bifurcations. We also describe the transient as the unstable CW output evolves to the oscillatory state. A main result
is that the presence of a saturable absorber can increase the sensitivity of the laser to delayed feedback.
Received 1st August 2001 and Received in final form 28 November 2001 相似文献
5.
E. Neumann A. Pikovsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):219-228
We consider the dynamics of the overdamped Josephson junction under the influence of an external quasiperiodic driving field.
In dependence on parameter values either a quasiperiodic motion or a strange nochaotic attractor (SNA) can be observed. The
latter corresponds to a resistive state in the current-voltage characteristics while for quasiperiodic motion a finite superconducting
current exists for zero voltage. It is shown that in the case of SNA a nonzero mean voltage across the junction can appear
due to symmetry breakings. Based on this observation a detailed symmetry consideration of the generalized equation of motion
is performed and symmetry conditions ensuring zero mean voltage across the junction are found.
Received 16 August 2001 and Received in final form 22 January 2002 相似文献
6.
M. Cosentino Lagomarsino B. Bassetti P. Jona 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):81-88
We introduce a model system of stochastic entities, called rowers which include some essentials of the behavior of real cilia. We introduce and discuss the problem of symmetry breaking for
these objects and its connection with the onset of macroscopic, directed flow in the fluid. We perform a mean field-like calculation
showing that hydrodynamic interaction may provide for the symmetry breaking mechanism and the onset of fluid flow. Finally,
we discuss the problem of the metachronal wave in a stochastic context through an analytical calculation based on a path integral
representation of our model equation.
Received 12 June 2001 and Received in final form 9 January 2002 相似文献
7.
M. Picco F. Ritort M. Sales 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):565-582
The use of parameters measuring order-parameter fluctuations (OPF) has been encouraged by the recent results reported in referenece
[2,3] which show that two of these parameters, G and G
c, take universal values in the . In this paper we present a detailed study of parameters measuring OPF for two mean-field models with and without time-reversal
symmetry which exhibit different patterns of replica symmetry breaking below the transition: the Sherrington-Kirkpatrick model
with and without a field and the Ising p-spin glass (p = 3). We give numerical results and analyze the consequences which replica equivalence imposes on these models in the infinite
volume limit. We give evidence for the transition in each system and discuss the character of finite-size effects. Furthermore,
a comparative study between this new family of parameters and the usual Binder cumulant analysis shows what kind of new information
can be extracted from the finite T behavior of these quantities. The two main outcomes of this work are: 1) Parameters measuring OPF give better estimates than
the Binder cumulant for T
c and even for very small systems they give evidence for the transition. 2) For systems with no time-reversal symmetry, parameters
defined in terms of connected quantities are the proper ones to look at.
Received 20 September 2000 and Received in final form 10 January 2001 相似文献
8.
R. Duprat C. Bourbonnais 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):219-228
The interference between spin-density-wave and superconducting instabilities in quasi-one-dimensional correlated metals is
analyzed using the renormalization group method. At the one-loop level, we show how the interference leads to a continuous
crossover from a spin-density-wave state to unconventional superconductivity when deviations from perfect nesting of the Fermi
surface exceed a critical value. Singlet pairing between electrons on neighboring stacks is found to be the most favorable
symmetry for superconductivity. The consequences of non uniform spin-density-wave pairing on the structure of phase diagram
within the crossover region is also discussed.
Received 3 January 2001 and Received in final form 1st March 2001 相似文献
9.
A. Brioude F. Lequevre J. Mugnier C. Bovier J. Dumas J.C. Plenet 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):115-119
Very thin ZrO
2
films (few nanometers) have been prepared by sol-gel process. These films were deposited onto a stack of a thin silver layer
evaporated on a glass substrate for Surface Plasmons Resonance (SPR) experiments. The first aim of this work is to study the
high densification of the sol-gel films followed by the refractive index and thickness accurate measurements at each step
of the annealing procedure, using an optical set-up based on SPR. Secondly, SPR excitation coupled with micro-Raman experiment
has also been performed to determine the thin films structure depending on layer thickness. Finally, Conventional Transmission
Electron Microscopy (CTEM) and High Resolution (HRTEM) studies have been conducted to check and complete Raman spectroscopy
results. A discussion compares the optical results and the Transmission Electron Microscopy observations and shows that ultra
thin layers structure is strongly depends on films thickness.
Received 14 May 2001 and Received in final form 2 January 2002 相似文献
10.
M. Ricker J. Bachteler H.-R. Trebin 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):351-363
In quasicrystals, there are not only conventional, but also phason displacement fields and associated Burgers vectors. We
have calculated approximate solutions for the elastic fields induced by two-, three- and fivefold straight screw- and edge-dislocations
in infinite icosahedral quasicrystals by means of a generalized perturbation method. Starting from the solution for elastic
isotropy in phonon and phason spaces, corrections of higher order reflect the two-, three- and fivefold symmetry of the elastic
fields surrounding screw dislocations. The fields of special edge dislocations display characteristic symmetries also, which
can be seen from the contributions of all orders.
Received 21 February 2001 and Received in final form 27 June 2001 相似文献
11.
Li Zhang Hong-Jing Xie Chuan-Yu Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):577-582
Within the framework of the dielectric continuum model, interface optical(IO) and surface optical(SO) phonon modes and the
Fr?hlich electron-IO (SO) phonon interaction Hamiltonian in a multi-shell spherical system were derived and studied. Numerical
calculation on CdS/HgS/H2O and CdS/HgS/CdS/H2O spherical systems have been performed. Results reveal that there are two IO modes and one SO mode for the CdS/HgS/H2O system, one SO mode and four IO modes whose frequencies approach the IO phonon frequencies of the single CdS/HgS heterostructure
with the increasing of the quantum number l for CdS/HgS/CdS/H2O. It also showed that smaller l and SO phonon compared with IO phonon, have more significant contribution to the electron-IO (SO) phonon interaction.
Received 16 October 2001 and Received in final form 23 January 2002 Published online 25 June 2002 相似文献
12.
M.B. Sheftel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):203-206
Using the heavenly equation as an example, we propose the method of group foliation as a tool for obtaining non-invariant
solutions of PDEs with infinite-dimensional symmetry groups. The method involves the study of compatibility of the given equations
with a differential constraint, which is automorphic under a specific symmetry subgroup and therefore selects exactly one
orbit of solutions. By studying the integrability conditions of this automorphic system, i.e. the resolving equations, one can provide an explicit foliation of the entire solution manifold into separate orbits. The
new important feature of the method is the extensive use of the operators of invariant differentiation for the derivation
of the resolving equations and for obtaining their particular solutions. Applying this method we obtain exact analytical solutions
of the heavenly equation, non-invariant under any subgroup of the symmetry group of the equation.
Received 13 September 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: sheftel@gursey.gov.tr 相似文献
13.
In this paper we study tricritical wetting behaviour in three dimensions. In particular we concentrate on systems with short-ranged
forces and apply linear functional renormalization group techniques to elucidate the effect of fluctuations upon tricriticality.
In comparison with studies of critical wetting we identify an additional fluctuation regime which is relevant for values of
the capillary parameter between 2/9 and 1/2. We demonstrate that this regime essentially provides a crossover from mean-field
like behaviour, in which tricritical exponents are always distinct from their critical counterparts, from intermediate- and
strong-fluctuation behaviour where the critical exponents for tricritical and critical wetting are found to always coincide.
We conclude by discussing briefly the possible relevance of these results for experimental studies of wetting.
Received 4 January 2001 and Received in final form 11 May 2001 相似文献
14.
C. Lorthioir P. Auroy B. Deloche Y. Gallot 《The European physical journal. E, Soft matter》2002,7(3):261-266
The chain segment dynamics in the bulk lamellar phase of polystyrene-polydimethylsiloxane (PS-PDMS) block copolymers has been
probed by NMR. The experiments were performed on a PS-PDMS diblock and on a PS-PDMS-PS triblock with twice the molecular weight.
In the diblock, at room temperature, the PDMS block segments undergo uniaxial reorientations around the normal to the lamellae.
In the triblock, the reorientational motions exhibit a lower degree of symmetry: deviations from a uniaxial dynamics are observed.
Such a behaviour originates in the anchorage of both PDMS chain ends into the PS glassy layers.
Received 27 September 2001 and Received in final form 18 January 2002 相似文献
15.
A. Fnidiki F. Studer J. Teillet J. Juraszek H. Pascard S. Meillon 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):291-295
The behavior of the magnetic properties of magnetite Fe3O4 irradiated by swift heavy ions is investigated by magnetization measurements. Although there is no induced structural phase
transformation, both coercive field and saturation magnetization are sensitive to ion irradiation and exhibit different behaviors
depending on the ion fluence range. In the low fluence regime, the coercive field increases, which is evidence for a strong
pinning of magnetic domain boundaries by the induced defects. The magnetization shows a decrease in the saturation value and
tends to reorient perpendicularly to the ion track axis. At high fluence, the initial magnetic properties of the sample are
nearly restored. The changes in the magnitude and the direction of magnetization are interpreted by magnetostrictive effects
related to the stress induced by irradiation. A phenomenological model is applied to reproduce the fluence evolution of the
saturation magnetization, assuming relaxation of the stress induced around the core of defects of the tracks by overlapping
effects at high fluence. The results are compared to those obtained in the case of yttrium iron garnet Y3Fe5O12.
Received 18 April 2001 and Received in final form 24 July 2001 相似文献
16.
G.G. Pereira 《The European physical journal. E, Soft matter》2002,7(3):273-289
The inherent nanoscale morphologies of self-organizing diblock copolymer melts are now being investigated for a variety of
technological applications. To obtain global, well-oriented, regular patterns requires suitably confining and aligning the
melt between two flat plates. Here we consider such confinement for an asymmetrical diblock melt, which forms columns of the
minority phase in a matrix of the majority phase. We investigate this system with a combination of numerical simulations and
strong segregation theory and make suggestions as to when perpendicular orientation should prevail over parallel orientation
of the columns.
Received 22 May 2001 and Received in final form 14 February 2002 相似文献
17.
I.I. Satija 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):345-348
Disordered systems exhibiting exponential localization are mapped to anisotropic spin chains with localization length being
related to the anisotropy of the spin model. This relates localization phenomenon in fermions to the rotational symmetry breaking
in the critical spin chains. One of the intriguing consequence is that the statement of Onsager universality in spin chains
implies universality of the localized fermions where the fluctuations in localized wave functions are universal. We further
show that the fluctuations about localized nonrelativistic fermions describe relativistic fermions. This provides a new approach
to understand the absence of localization in disordered Dirac fermions. We investigate how disorder affects well known universality
of the spin chains by examining the multifractal exponents. Finally, we examine the effects of correlations on the localization
characteristics of relativistic fermions.
Received 28 September 2001 / Received in final form 30 November 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: isatija@nickel.nist.gov 相似文献
18.
R. Ramaswamy 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):339-343
Integrable dynamical systems, namely those having as many independent conserved quantities as freedoms, have all Lyapunov
exponents equal to zero. Locally, the instantaneous or finite time Lyapunov exponents are nonzero, but owing to a symmetry,
their global averages vanish. When the system becomes nonintegrable, this symmetry is broken. A parallel to this phenomenon
occurs in mappings which derive from quasiperiodic Schr?dinger problems in 1-dimension. For values of the energy such that
the eigenstate is extended, the Lyapunov exponent is zero, while if the eigenstate is localized, the Lyapunov exponent becomes
negative. This occurs by a breaking of the quasiperiodic symmetry of local Lyapunov exponents, and corresponds to a breaking
of a symmetry of the wavefunction in extended and critical states.
Received 25 October 2001 / Received in final form 8 December 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: r.ramaswamy@mail.jnu.ac.in 相似文献
19.
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
20.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献