共查询到20条相似文献,搜索用时 484 毫秒
1.
C. J. Tessone D. H. Zanette R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):319-326
We study the influence of repulsive interactions on an
ensemble of coupled excitable rotators. We find that a moderate
fraction of repulsive interactions can trigger global firing of the
ensemble. The regime of global firing, however, is suppressed in
sufficiently large systems if the network of repulsive interactions
is fully random, due to self-averaging in its degree distribution.
We thus introduce a model of partially random networks with a broad
degree distribution, where self-averaging due to size growth is
absent. In this case, the regime of global firing persists for large
sizes. Our results extend previous work on the constructive effects
of diversity in the collective dynamics of complex systems. 相似文献
2.
E. Fersino B. A. Malomed G. Mussardo A. Trombettoni 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):417-426
We study the effect of an optical lattice (OL) on the ground-state properties of one-dimensional ultracold bosons with three-body
attractive interactions and two-body repulsive interactions, which are described by a cubic-quintic Gross-Pitaevskii equation
with a periodic potential. Without the optical lattice and with a vanishing two-body interaction term, normalizable soliton
solutions of the Townes type are possible only at a critical value of the interaction strength, at which an infinite degeneracy of the ground state
occurs; a repulsive two-body interaction makes such localized solutions unstable. We show that the OL opens a stability window
around the critical point when the strength of the periodic potential is above a critical threshold. We also consider the
effect of an external parabolic trap, studying how the stability properties depend on the matching between minima of the periodic
potential and the minimum of the parabolic trap. 相似文献
3.
We investigate the interactions between components of various vector solitons in Bos-Einstein condensates by means of the least action principle, and derive the effective potentials for different vector solitons, which indicate that the interactions are of short range, and may be repulsive or attractive decided by the different intra- and inter-species interactions in such a system. In the case of attraction, the two solitons will oscillate about and pass through each other around the equilibrium state. The comparison of analytical results with mumertical simulation is presented. 相似文献
4.
We report the existence, and study mobility and interactions of gap polariton solitons in a microcavity with a periodic potential, where the light field is strongly coupled to excitons. Gap solitons are formed due to the interplay between the repulsive exciton-exciton interaction and cavity dispersion. The analysis is carried out in an analytical form, using the coupled-mode (CM) approximation, and also by means of numerical methods. 相似文献
5.
Y. J. Hao S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):261-266
We study ground-state properties of interacting two-component boson gases in a one-dimensional harmonic trap by using the
exact numerical diagonalization method. Based on numerical solutions of many-body Hamiltonians, we calculate the ground-state
density distributions in the whole interaction regime for different atomic number ratio, intra- and inter-atomic interactions.
For the case with equal intra- and inter-atomic interactions, our results clearly display the evolution of density distributions
from a Bose condensate distribution to a Fermi-like distribution with the increase of the repulsive interaction. Particularly,
we compare our result in the strong interaction regime to the exact result in the infinitely repulsive limit which can be
obtained by a generalized Bose-Fermi mapping. We also discuss the general case with different intra- and inter-atomic interactions
and show the rich configurations of the density profiles. 相似文献
6.
D. Jovanović R. Fedele 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):363-368
Two-dimensional stability of a controlled Bose-Einstein
condensation state, in the form of a nonlinear Schr?dinger soliton
[JETP Lett. 80 535 (2004)], is studied
for the condensations with both repulsive and attractive inter-atom
interactions. The Gross-Pitaevski equation is solved numerically,
taking initialy a controlled soliton whose “effective mass” is
several times bigger than the critical value for a weak collapse in
the absence of a potential well, and allowing for reasonably large
errors in the experimental realization of the trapping potential
required by the theory. For repulsive and sufficiently weak
attractive interactions, the controlled state is shown to remain
stable inside a breathing potential well, for a time that is an
order of magnitude longer than the characteristic periods of the
forced and eigenoscillations of the soliton. The collapse is
observed only for attractive interactions, when the nonlinear
attraction exceeded the appropriate threshold.
Electronic supplementary material Supplementary Online Material 相似文献
7.
Olson Reichhardt CJ Reichhardt C Bishop AR 《The European physical journal. E, Soft matter》2007,22(1):11-15
Motivated by recent experiments on colloidal systems with
competing attractive and repulsive interactions,
we simulate a two-dimensional system of colloids
with competing interactions that can undergo fragmentation.
In the absence of any
other confining potential, the colloids can form stable clusters
depending on the strength of the short range attractive term.
By suddenly changing the strength of one of the interaction
terms we
find a rich variety of fragmentation behavior which is affected
by the existence of “magic” cluster numbers.
Such soft matter systems can
be used to construct artificial nuclei. 相似文献
8.
Contact interactions always lead to attractive behavior. Arguments are presented to show why a repulsive interacting system, e.g. Bose gases, cannot be described by contact interactions and corresponding treatments are possibly obscured by the appearance of bound states. The usually used cut-offs are identified as finite range parameters. 相似文献
9.
T. Vaz Martins R. Toral M. A. Santos 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):329-336
We study an Ising model in a network with disorder induced by the presence of both attractive and repulsive links and subjected
to a periodic subthreshold signal. By means of numerical simulations and analytical calculations we give evidence that the
global response of the system reaches a maximum value for a given fraction of the number of repulsive interactions. The model
can represent a network of spin-like neurons with excitatory and inhibitory couplings, or a simple opinion spreading model.
In this context, attractive/repulsive links represent friends and enemies. “Divide and Conquer” refers to the fact that in
order to force a society to adopt a new point of view, it helps to break its homogeneity by fostering enmities amongst its
members. 相似文献
10.
A. Ruschhaupt A. del Campo J. G. Muga 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):399-403
A Bose-Einstein condensate may be prepared
in a harmonic trap with negligible
interatomic interactions using a Feshbach resonance.
If a strong repulsive interatomic interaction is switched on and
the trap is removed to let the condensate evolve freely,
a time dependent quantum interference pattern takes place in the short time
(Thomas-Fermi) regime, in which the number of peaks of the momentum
distribution increases one by one, whereas the spatial density barely changes.
The effect is stable for initial states with interactions and
realistic time-dependence of the scattering length. 相似文献
11.
A. B. D. Brown C. Ferrero T. Narayanan A. R. Rennie 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):481-489
The structure and phase behaviour of a colloidal dispersion of plate-like particles are described. The plates are nickel (II)
hydroxide and have short-range, repulsive interactions and a low polydispersity. As the concentration of the plates is increased,
an equilibrium phase separation between a columnar phase and a less ordered phase is observed. Complementary measurements
using small-angle neutron and small-angle X-ray scattering have been used to distinguish the columnar phase from other possible
ordered structures. Previously isotropic-nematic phase transitions have been observed [#!ref1!#], however this dispersion
forms the more highly ordered columnar phase, due to the aspect ratio and the low polydispersity of the plate-like particles.
The concentration at which phase separation occurs, increases as the range of the particle interactions is reduced. This system
provides an interesting model for comparison with theory and calculations of structures in liquid crystal and mesophase in
which the particle interactions can be altered.
Received 24 February 1999 相似文献
12.
Highly dispersed superstructures of a dipolar iridium complex are formed on a Cu(111) surface. We show that the dilute superstructures with density-controlled intermolecular separations are stabilized by the strong and long-range repulsive intermolecular interactions. The repulsive intermolecular interactions are quantitatively evaluated by using low-temperature scanning tunneling microscopy, which are characterized by the surface-enhanced dipole-dipole interactions. 相似文献
13.
We study a model in which particles interact with short-ranged attractive and long-ranged repulsive interactions, in an attempt to model the equilibrium cluster phase recently discovered in sterically stabilized colloidal systems in the presence of depletion interactions. At low packing fractions, particles form stable equilibrium clusters which act as building blocks of a cluster fluid. We study the possibility that cluster fluids generate a low-density disordered arrested phase, a gel, via a glass transition driven by the repulsive interaction. In this model the gel formation is formally described with the same physics of the glass formation. 相似文献
14.
Weikl TR Andelman D Komura S Lipowsky R 《The European physical journal. E, Soft matter》2002,8(1):59-66
Biomimetic membranes in contact with a planar substrate or a second membrane are studied theoretically. The membranes contain
specific adhesion molecules (stickers) which are attracted by the second surface. In the absence of stickers, the trans-interaction
between the membrane and the second surface is assumed to be repulsive at short separations. It is shown that the interplay
of specific attractive and generic repulsive interactions can lead to the formation of a potential barrier. This barrier induces
a line tension between bound and unbound membrane segments which results in lateral phase separation during adhesion. The
mechanism for adhesion-induced phase separation is rather general, as is demonstrated by considering two distinct cases involving:
i) stickers with a linear attractive potential, and ii) stickers with a short-ranged square-well potential. In both cases,
membrane fluctuations reduce the potential barrier and, therefore, decrease the tendency of phase separation.
Received 24 January 2002 and Received in final form 24 April 2002 相似文献
15.
Coupling between Collective Excitations of a Bose--Einstein Condensate and Modulated Interactions 下载免费PDF全文
We investigate collective excitations of a Bose Einstein repulsive interactions, and analytically demonstrate that condensate in the presence of temporal modulation of the modulated interaction can drive the condensate to oscillate with the external modulation frequency, and that the interaction couples with the eigen modes of the condensate collective excitations, which was previously considered to be independent of interaction. When the external modulation frequency approaches or is far away from the eigen frequency of the density monopole mode, the condensate shows resonant or beating behaviour. 相似文献
16.
Scanning tunneling microscopy (STM) was used to investigate the role of repulsive interactions in the adsorption and patterning of molecular bromine on the Si(100) surface. At room temperature and low coverage, chemisorption of bromine occurs dissociatively on the same side of adjacent dimers of the same row. Using the STM tip as a probe, we demonstrate the existence of repulsive interactions at adjacent sites on the Si(100)-2×1 surface. These repulsive interactions also contribute to the arrangement of adatoms on the surface. In particular, we report the presence of a stable c(4×2) surface phase that results after exposing the Si(100) surface to bromine under certain conditions. This phase involves adsorption on non-neighboring dimers and is stabilized by repulsive interactions that force bromine adatoms to occupy alternating dimers within rows with an out-of-phase occupancy between adjacent rows. 相似文献
17.
Guilherme S. Nunes 《Physics letters. A》2008,372(12):2048-2049
We point out that, when repulsive interactions between two fermions are not integrable, as the case may be for atomic fermions, the original Kohn-Sham density functional must be revised. 相似文献
18.
X. Deng R. Citro E. Orignac A. Minguzzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):435-443
Using exact diagonalisation and Density Matrix Renormalisation group (DMRG) approach we analyse the transition to a localised
state of a weakly interacting quasi-1D Bose gas subjected to a quasiperiodic potential. The analysis is performed by calculating
the superfluid fraction, density profile, momentum distribution and visibility for different periodicities of the second lattice
and in the presence (or not) of a weak repulsive interaction. It is shown that the transition is sharper towards the maximally
incommensurate ratio between the two lattice periodicities, and shifted to higher values of the second lattice strength by
weak repulsive interactions. We also relate our results to recent experiments. 相似文献
19.
M. Gasperini 《General Relativity and Gravitation》1998,30(12):1703-1709
I present two examples in which the curvature singularity of a radiation-dominated Universe is regularized by (a) the repulsive effects of spin interactions, and (b) the repulsive effects arising from a breaking of the local gravitational gauge symmetry. In both cases the collapse of an initial, asymptotically flat state is stopped, and the Universe bounces towards a state of decelerated expansion. The emerging picture is typical of the pre-big bang scenario, with the main difference that the string cosmology dilaton is replaced by a classical radiation fluid, and the solutions are not duality-invariant. 相似文献
20.
We describe a theoretical study of the role of adsorbate interactions in island nucleation and growth, using Ag/Pt(111) heteroepitaxy as an example. From density-functional theory, we obtain the substrate-mediated Ag adatom pair interaction and we find that, past the short range, a repulsive ring is formed about the adatoms. The magnitude of the repulsion is comparable to the diffusion barrier. In kinetic Monte Carlo simulations, we find that the repulsive interactions lead to island densities over an order of magnitude larger than those predicted by nucleation theory and thus identify a severe limitation of its applicability. 相似文献