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1.
The dynamics of spreading of the minority opinion in public debates (a reform proposal, a behavior change, a military retaliation)
is studied using a diffusion reaction model. People move by discrete step on a landscape of random geometry shaped by social
life (offices, houses, bars, and restaurants). A perfect world is considered with no advantage to the minority. A one person-one
argument principle is applied to determine locally individual mind changes. In case of equality, a collective doubt is evoked
which in turn favors the Status Quo. Starting from a large in favor of the proposal initial majority, repeated random size
local discussions are found to drive the majority reversal along the minority hostile view. Total opinion refusal is completed
within few days. Recent national collective issues are revisited. The model may apply to rumor and fear propagation.
Received 23 January 2002 相似文献
2.
A model to terrorism is presented using the theory of percolation. Terrorism power is related to the spontaneous formation
of random backbones of people who are sympathetic to terrorism but without being directly involved in it. They just don't
oppose in case they could. In the past such friendly-to-terrorism backbones have been always existing but were of finite size
and localized to a given geographical area. The September 11 terrorist attack on the US has revealed for the first time the
existence of a world wide spread extension. It is argued to have result from a sudden world percolation of otherwise unconnected
and dormant world spread backbones of passive supporters. The associated strategic question is then to determine if collecting
ground information could have predict and thus avoid such a transition. Our results show the answer is no, voiding the major
criticism against intelligence services. To conclude the impact of military action is discussed.
Received 7 February 2002 相似文献
3.
D. Stauffer P.M.C. de Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):587-592
The density of never changed opinions during the Sznajd consensus-finding process decays with time t as 1/t
θ. We find θ ≃ 3/8 for a chain, compatible with the exact Ising result of Derrida et al. In higher dimensions, however, the exponent differs from the Ising θ. With simultaneous updating of sublattices instead of
the usual random sequential updating, the number of persistent opinions decays roughly exponentially. Some of the simulations
used multi-spin coding.
Received 22 August 2002 / Received in final form 12 November 2002 Published online 31 December 2002 相似文献
4.
E. Brézin C. De Dominicis 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):467-471
The replicated field theory of the random field Ising model involves the couplings of replicas of different indices. The resulting
correlation functions involve a superposition of different types of long distance behaviours. However the n = 0 limit allows one to discuss the renormalization group properties in spite of this phenomenon. The attraction of pairs
of replicas is enhanced under renormalization flow and no stable fixed point is found. Consequently, an instability occurs
in the paramagnetic region, before one reaches the Curie line, signalling the onset of replica symmetry breaking.
Received 28 July 2000 相似文献
5.
A. Chakraborti B.K. Chakrabarti 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):677-680
If one places N cities randomly on a lattice of size L, we find that and vary with the city concentration p=N/L
2, where is the average optimal travel distance per city in the Euclidean metric and is the same in the Manhattan metric. We have studied such optimum tours for visiting all the cities using a branch and bound
algorithm, giving the exact optimized tours for small system sizes () and near-optimal tours for bigger system sizes (). Extrapolating the results for , we find that for p=1, and and with as . Although the problem is trivial for p=1, for it certainly reduces to the standard travelling salesman problem on continuum which is NP-hard. We did not observe any irregular
behaviour at any intermediate point. The crossover from the triviality to the NP-hard problem presumably occurs at p=1.
Received 15 April 2000 相似文献
6.
A.T. Bernardes D. Stauffer J. Kertész 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(1):123-127
The network of Barabasi and Albert, a preferential growth model where a new node is linked to the old ones with a probability
proportional to their connectivity, is applied to Brazilian election results. The application of the Sznajd rule, that only
agreeing pairs of people can convince their neighbours, gives a vote distribution in good agreement with reality
Received 19 September 2001 and Received in final form 2 November 2001 相似文献
7.
W. Jeżewski 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):133-138
Scaling properties of the Gibbs distribution of a finite-size one-dimensional Ising model are investigated as the thermodynamic
limit is approached. It is shown that, for each nonzero temperature, coarse-grained probabilities of the appearance of particular
energy levels display multiscaling with the scaling length ℓ = 1/M
n, where n denotes the number of spins and Mn is the total number of energy levels. Using the multifractal formalism, the probabilities are argued to reveal also multifractal
properties.
Received 10 July 2000 and Received in final form 6 November 2000 相似文献
8.
M. Casartelli L. Dall'Asta A. Vezzani P. Vivo 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):91-105
The non-ergodic behavior of the deterministic Fixed Energy Sandpile (DFES), with Bak-Tang-Wiesenfeld (BTW) rule, is explained
by the complete characterization of a class of dynamical invariants (or toppling invariants). The link between such constants
of motion and the discrete Laplacians properties on graphs is algebraically and numerically clarified. In particular, it is
possible to build up an explicit algorithm determining the complete set of independent toppling invariants. The partition
of the configuration space into dynamically invariant sets, and the further refinement of such a partition into basins of
attraction for orbits, are also studied. The total number of invariant sets equals the graphs complexity. In the case of two
dimensional lattices, it is possible to estimate a very regular exponential growth of this number vs. the size. Looking at
other features, the toppling invariants exhibit a highly irregular behavior. The usual constraint on the energy positiveness
introduces a transition in the frozen phase. In correspondence to this transition, a dynamical crossover related to the halting
times is observed. The analysis of the configuration space shows that the DFES has a different structure with respect to dissipative
BTW and stochastic sandpiles models, supporting the conjecture that it lies in a distinct class of universality. 相似文献
9.
F.W.S. Lima J.E. Moreira J.S. Andrade Jr. U.M.S. Costa 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):107-110
We investigate the two-dimensional eight-states ferromagnetic Potts model in the Voronoi-Delaunay tessellation. In this study,
we assume that the coupling factor J varies with the distance r between the first neighbors as , with . The disordered system is simulated applying the single-cluster Monte-Carlo update algorithm and the reweighting technique.
We find that this model displays a first-order phase transition if , in agreement with previous recent studies. For and 1.0, a typical second order transition is observed and the critical exponents for magnetization and susceptibility are
calculated.
Received 19 May 1999 and Received in final form 2 June 1999 相似文献
10.
G. Parisi F. Tria 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):533-541
We study spin glasses on random lattices with finite connectivity. In the infinite connectivity limit they reduce to the Sherrington
Kirkpatrick model. In this paper we investigate the expansion around the high connectivity limit. Within the replica symmetry
breaking scheme at two steps, we compute the free energy at the first order in the expansion in inverse powers of the average
connectivity (z), both for the fixed connectivity and for the fluctuating connectivity random lattices. It is well known that the coefficient
of the 1/z correction for the free energy is divergent at low temperatures if computed in the one step approximation. We find that this
annoying divergence becomes much smaller if computed in the framework of the more accurate two steps breaking. Comparing the
temperature dependance of the coefficients of this divergence in the replica symmetric, one step and two steps replica symmetry
breaking, we conclude that this divergence is an artefact due to the use of a finite number of steps of replica symmetry breaking.
The 1/z expansion is well defined also in the zero temperature limit.
Received 15 July 2002 Published online 31 December 2002 相似文献
11.
S. Lübeck A. Misra 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):75-79
Extensive simulations are performed to study the persistence behavior of a conserved lattice gas model exhibiting an absorbing
phase transition from an active phase into an inactive phase. Both the global and the local persistence exponents are determined
in two and higher dimensions. The local persistence exponent obeys a scaling relation involving the order parameter exponent
of the absorbing phase transition. Furthermore we observe that the global persistence exponent exceeds its local counterpart
in all dimensions in contrast to the known persistence behavior in reversible phase transitions.
Received 27 August 2001 and Received in final form 15 November 2001 相似文献
12.
H. Niggemann A. Klümper J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):15-19
We use the vertex state model approach to construct optimum ground states for a large class of quantum spin-2 antiferromagnets
on the square lattice. Optimum ground states are exact ground states of the model which minimize all local interaction operators.
The ground state contains two continuous parameters and exhibits a second order phase transition from a disordered phase with
exponentially decaying correlation functions to a Néel ordered phase. The behaviour is very similar to that of the corresponding
ground state of a quantum spin-3/2 model on the hexagonal lattice, which has been investigated in an earlier paper.
Received 8 April 1999 相似文献
13.
L. Turban 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):273-285
We study the influence of an aperiodic extended surface perturbation on the surface critical behaviour of the two-dimensional
Ising model in the extreme anisotropic limit. The perturbation decays as a power of the distance l from the free surface with an oscillating amplitude where follows some aperiodic sequence with an asymptotic density equal to 1/2 so that the mean amplitude vanishes. The relevance
of the perturbation is discussed by combining scaling arguments of Cordery and Burkhardt for the Hilhorst-van Leeuwen model
and Luck for aperiodic perturbations. The relevance-irrelevance criterion involves the decay exponent , the wandering exponent which governs the fluctuation of the sequence and the bulk correlation length exponent . Analytical results are obtained for the surface magnetization which displays a rich variety of critical behaviours in the
-plane. The results are checked through a numerical finite-size-scaling study. They show that second-order effects must be
taken into account in the discussion of the relevance-irrelevance criterion. The scaling behaviours of the first gap and the
surface energy are also discussed.
Received 1 December 1998 相似文献
14.
15.
H. Niggemann J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):377-379
We present the construction of an optimum ground state for a quantum spin-3/2 antiferromagnet. The spins reside on a decorated
square lattice, in which the basis consists of a plaquette of four sites. By using the vertex state model approach we generate
the ground state from the same vertices as those used for the corresponding ground state on the hexagonal lattice. The properties
of these two ground states are very similar. Particularly there is also a parameter-controlled phase transition from a disordered
to a Néel ordered phase. In the regime of this transition, ground state properties can be obtained from an integrable classical
vertex model.
Received 28 June 1999 相似文献
16.
H. Arkın T. Çelik 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):577-580
To investigate the performance of the energy landscape paving (ELP) procedure for peptides, we apply it here to deltorphin,
a linear heptapeptide with bulky side chains (H-Tyr1-D-Met2-Phe3-His4-Leu5-Met6-Asp7-NH2) and compare the results with the Multicanonical method (MUCA) in regard of finding the low-energy structures. Deltorphin
is modeled in vacuum by the potential energy function ECEPP.
Received 23 July 2002 / Received in final form 18 September 2002 Published online 31 December 2002 相似文献
17.
S. Galam S. Wonczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):183-186
Majority rule voting in a multi-level system is studied using tools from the physics of disorder. We are not dealing with
nation-wide general elections but rather with hierarchical organisations made of small committees. While in theory, for a
two candidate election, the critical threshold to absolute power is , the usual existence of some local and reasonable bias makes it asymmetric, transforming a democratic system in effect to
a dictatorship. The underlying dynamics of this democratic self-elimination is studied using a simulation which visualizes
the full process. In addition the effect of non-voting persons (abstention, sickness, apathy) is also studied. It is found
to have an additional drastic effect on the asymmetry of the threshold value to power. Some possible applications are mentioned.
Received 21 July 2000 相似文献
18.
J. Török S. Krishnamurthy J. Kertész S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):697-701
We introduce a model for the slow relaxation of an energy landscape caused by its local interaction with a random walker whose
motion is dictated by the landscape itself. By choosing relevant measures of time and potential this self-quenched dynamics can be mapped on to the “True” Self-Avoiding Walk model. This correspondence reveals that the average distance of
the walker at time t from its starting point is , where for one dimension and 1/2 for all higher dimensions. Furthermore, the evolution of the landscape is similar to that in growth
models with extremal dynamics.
Received 8 August 2000 相似文献
19.
W. Selke V.L. Pokrovsky B. Büchner T. Kroll 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):83-92
Motivated by recent experiments on cuprates with low-dimensional magnetic interactions, a new class of two-dimensional Ising
models with short-range interactions and mobile defects is introduced and studied. The non-magnetic defects form lines, which,
as temperature increases, first meander and then become unstable. Using Monte Carlo simulations and analytical low- and high-temperature
considerations, the instability of the defect stripes is monitored for various microscopic and thermodynamic quantities in
detail for a minimal model, assuming some of the couplings to be indefinitely strong. The robustness of the findings against
weakening the interactions is discussed as well.
Received 22 August 2002 / Received in final form 4 October 2002 Published online 19 November 2002 相似文献
20.
J. Schulenburg J.S. Flynn D.D. Betts J. Richter 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):191-204
In this paper finite bcc lattices are defined by a triple of vectors in two different ways - upper triangular lattice form
and compact form. In Appendix A are lists of some 260 distinct and useful bcc lattices of 9 to 32 vertices. The energy and
magnetization of the S = 1/2 XY ferromagnet have been computed on these bcc lattices in the lowest states for S
z = 0, 1/2, 1 and 3/2. These data are studied statistically to fit the first three terms of the appropriate finite lattice
scaling equations. Our estimates of the T = 0 energy and magnetization agree very well with spin wave and series expansion estimates.
Received 1st August 2000 and Received in final form 22 December 2000 相似文献