4,027 research outputs found
Interdisciplinary Monte Carlo Simulations
Biological, linguistic, sociological and economical applications of
statistical physics are reviewed here. They have been made on a variety of
computers over a dozen years, not only at the NIC computers. A longer
description can be found in our new book, an emphasis on teaching in
Eur.J.Phys. 26, S 79 and AIP Conf. Proc. 779, 49, 56, 69 and 75.Comment: 11 pages including many Figs.; for 3rd NIC Symposium, Julich, 3/0
Multidimensional Consensus model on a Barabasi-Albert network
A Consensus Model according to Deffuant on a directed Barabasi-Albert network
was simulated. Agents have opinions on different subjects. A multi-component
subject vector was used. The opinions are discrete. The analysis regards
distribution and clusters of agents which are on agreement in the opinions of
the subjects. Remarkable results are on the one hand, that there mostly exists
no absolute consens. It determines depending on the ratio of number of agents
to the number of subjects, whether the communication ends in a consens or a
pluralism. Mostly a second robust cluster remains, in its size depending on the
number of subjects. Two agents agree either in (nearly) all or (nearly) no
subject. The operative parameter of the consens-formating-process is the
tolerance in change of views of the group-members.Comment: 14 pages including all 10 figures, for IJMPC 16, issue
Upper transition point for percolation on the enhanced binary tree: A sharpened lower bound
Hyperbolic structures are obtained by tiling a hyperbolic surface with
negative Gaussian curvature. These structures generally exhibit two percolation
transitions: a system-wide connection can be established at a certain
occupation probability and there emerges a unique giant cluster at
. There have been debates about locating the upper transition
point of a prototypical hyperbolic structure called the enhanced binary tree
(EBT), which is constructed by adding loops to a binary tree. This work
presents its lower bound as by using phenomenological
renormalization-group methods and discusses some solvable models related to the
EBT.Comment: 12 pages, 20 figure
Drift and trapping in biased diffusion on disordered lattices
We reexamine the theory of transition from drift to no-drift in biased
diffusion on percolation networks. We argue that for the bias field B equal to
the critical value B_c, the average velocity at large times t decreases to zero
as 1/log(t). For B < B_c, the time required to reach the steady-state velocity
diverges as exp(const/|B_c-B|). We propose an extrapolation form that describes
the behavior of average velocity as a function of time at intermediate time
scales. This form is found to have a very good agreement with the results of
extensive Monte Carlo simulations on a 3-dimensional site-percolation network
and moderate bias.Comment: 4 pages, RevTex, 3 figures, To appear in International Journal of
Modern Physics C, vol.
Exact Results for Average Cluster Numbers in Bond Percolation on Lattice Strips
We present exact calculations of the average number of connected clusters per
site, , as a function of bond occupation probability $p$, for the bond
percolation problem on infinite-length strips of finite width $L_y$, of the
square, triangular, honeycomb, and kagom\'e lattices $\Lambda$ with various
boundary conditions. These are used to study the approach of , for a given
and , to its value on the two-dimensional lattice as the strip
width increases. We investigate the singularities of in the complex $p$
plane and their influence on the radii of convergence of the Taylor series
expansions of about and .Comment: 16 pages, revtex, 7 eps figure
Clique-circulants and the stable set polytope of fuzzy circular interval graphs
In this paper, we give a complete and explicit description of the rank facets of the stable set polytope for a class of claw-free graphs, recently introduced by Chudnovsky and Seymour (Proceedings of the Bristish Combinatorial Conference, 2005), called fuzzy circular interval graphs. The result builds upon the characterization of minimal rank facets for claw-free graphs by Galluccio and Sassano (J. Combinatorial Theory 69:1-38, 2005) and upon the introduction of a superclass of circulant graphs that are called clique-circulants. The new class of graphs is invetigated in depth. We characterize which clique-circulants C are facet producing, i.e. are such that Sigma upsilon epsilon V(C) chi(upsilon) <= alpha(C) is a facet of STAB(C), thus extending a result of Trotter (Discrete Math. 12:373-388, 1975) for circulants. We show that a simple clique family inequality (Oriolo, Discrete Appl. Math. 132(2):185-201, 2004) may be associated with each clique-circulant C subset of G, when G is fuzzy circular interval. We show that these inequalities provide all the rank facets of STAB(G), if G is a fuzzy circular interval graph. Moreover we conjecture that, in this case, they also provide all the non-rank facets of STAB(G) and offer evidences for this conjecture
Geometrical Phase Transition on WO Surface
A topographical study on an ensemble of height profiles obtained from atomic
force microscopy techniques on various independently grown samples of tungsten
oxide WO is presented by using ideas from percolation theory. We find that
a continuous 'geometrical' phase transition occurs at a certain critical
level-height below which an infinite island appears. By using the
finite-size scaling analysis of three independent percolation observables i.e.,
percolation probability, percolation strength and the mean island-size, we
compute some critical exponents which characterize the transition. Our results
are compatible with those of long-range correlated percolation. This method can
be generalized to a topographical classification of rough surface models.Comment: 3 pages, 4 figures, to appear in Applied Physics Letters (2010
Pacific bonito management information document
Management of Pacific bonito in California is examined in this Management Information Document by a State-Federal team of scientists.
Abundance of Pacific bonito in southern California has fallen dramatically between the 1963-1969 period and the 1974-1977 period. Since 1976 the commercia1 fleet has found few large fish in southern California, and has caught fish in the size range of 15 to 57 cm (1.2 to 4.7 pounds). This fact, coupled with the low abundance indices, point out the need for a more active management regime.
To develop management measures for the California bonito
fishery both a surplus yield analysis and a yield-per-recruit analysis were performed. A maximum sustained yield of 10,000 short tons was estimated for the fishery in southern California, while the whole fishery, including Baja California, has an estimated MSY of 13,000 tons. In order to achieve this level of catch, however, the stock abundance must be increased by a factor of five.
Yield-per-recruit considerations suggest that a minimum
size limit in the commercial fishery has two important effects. A three-pound size limit could result in a slight increase in yield-per-recruit. If the size limit is increased to 5 or 7.5 lbs, the yield-per-recruit would fall significantly. Offsetting the effect on yield-per-recruit, however, would be a substantial increase in average amount of spawning per recruit which should result in a proportional increase in recruitment. With the current depressed stock abundance both a reduced annual take and
a minimum size limit on commercial catch would confer
substantial benefits in the form of an increase in the future stock size.
After considering seven different types of management
measures, the team finds that three types -- an annual commercial catch quota, a commercial size limit, and a recreational bag limit -- appear desirable.
Re-establishment of the stock in southern California was
the major consideration in this evaluation because the stock is currently depressed. All segments of the fishery will benefit from a more abundant resource. The difficult issues for policy, however, concern the rate of rebuilding, the degree of risk that is acceptable, and the distribution of benefits among user groups. By judicious choice among the options discussed here, a variety of positions can be established with respect to these issues. The greater the
size limit, for instance, the more benefit is provided the
recreational sector while difficulties are imposed upon commercial fishermen. The higher the quotas adopted, the
slower the stock rebuilding and the greater the risk of continued stock depletion. A final reconciliation of the management options involves social, political and legal considerations which must be thoroughly incorporated by decision-makers before adoption of a management plan. (93pp.
Monte Carlo Simulation of Deffuant opinion dynamics with quality differences
In this work the consequences of different opinion qualities in the Deffuant
model were examined. If these qualities are randomly distributed, no different
behavior was observed. In contrast to that, systematically assigned qualities
had strong effects to the final opinion distribution. There was a high
probability that the strongest opinion was one with a high quality.
Furthermore, under the same conditions, this major opinion was much stronger
than in the models without systematic differences. Finally, a society with
systematic quality differences needed more tolerance to form a complete
consensus than one without or with unsystematic ones.Comment: 8 pages including 5 space-consuming figures, fir Int. J. Mod. Phys. C
15/1
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