929 research outputs found
The Grounds For Time Dependent Market Potentials From Dealers' Dynamics
We apply the potential force estimation method to artificial time series of
market price produced by a deterministic dealer model. We find that dealers'
feedback of linear prediction of market price based on the latest mean price
changes plays the central role in the market's potential force. When markets
are dominated by dealers with positive feedback the resulting potential force
is repulsive, while the effect of negative feedback enhances the attractive
potential force.Comment: 9 pages, 3 figures, proceedings of APFA
Self-organization of structures and networks from merging and small-scale fluctuations
We discuss merging-and-creation as a self-organizing process for scale-free
topologies in networks. Three power-law classes characterized by the power-law
exponents 3/2, 2 and 5/2 are identified and the process is generalized to
networks. In the network context the merging can be viewed as a consequence of
optimization related to more efficient signaling.Comment: Physica A: Statistical Mechanics and its Applications, In Pres
A universal mechanism for long-range cross-correlations
Cross-correlations are thought to emerge through interaction between particles. Here we present a universal dynamical mechanism capable of generating power-law cross-correlations between non-interacting particles exposed to an external potential. This phenomenon can occur as an ensemble property when the external potential induces intermittent dynamics of Pomeau-Manneville type, providing laminar and stochastic phases of motion in a system with a large number of particles. In this case, the ensemble of particle-trajectories forms a random fractal in time. The underlying statistical self-similarity is the origin of the observed power-law cross-correlations. Furthermore, we have strong indications that a sufficient condition for the emergence of these long-range cross-correlations is the divergence of the mean residence time in the laminar phase of the single particle motion (sporadic dynamics). We argue that the proposed mechanism may be relevant for the occurrence of collective behaviour in critical systems
Investigating the nature of light scalar mesons with semileptonic decays of D mesons
We study the semileptonic decays of D-s(+), D+, and D-0 mesons into the light scalar mesons [f(0)(500), K-0(*)(800), f(0)(980), and a(0)(980)] and the light vector mesons [rho(770), omega(782), K-*(892), and phi(1020)]. With the help of a chiral unitarity approach in coupled channels, we compute the branching fractions for scalar meson processes of the semileptonic D decays in a simple way. Using current known values of the branching fractions, we make predictions for the branching fractions of the semileptonic decay modes with other scalar and vector mesons. Furthermore, we calculate the pi(+)pi(-), pi eta, pi K, and K+K- invariant mass distributions in the semileptonic decays of D mesons, which will help us clarify the nature of the light scalar mesons
Propagation and Extinction in Branching Annihilating Random Walks
We investigate the temporal evolution and spatial propagation of branching
annihilating random walks in one dimension. Depending on the branching and
annihilation rates, a few-particle initial state can evolve to a propagating
finite density wave, or extinction may occur, in which the number of particles
vanishes in the long-time limit. The number parity conserving case where
2-offspring are produced in each branching event can be solved exactly for unit
reaction probability, from which qualitative features of the transition between
propagation and extinction, as well as intriguing parity-specific effects are
elucidated. An approximate analysis is developed to treat this transition for
general BAW processes. A scaling description suggests that the critical
exponents which describe the vanishing of the particle density at the
transition are unrelated to those of conventional models, such as Reggeon Field
Theory. P. A. C. S. Numbers: 02.50.+s, 05.40.+j, 82.20.-wComment: 12 pages, plain Te
Topological Properties of Citation and Metabolic Networks
Topological properties of "scale-free" networks are investigated by
determining their spectral dimensions , which reflect a diffusion process
in the corresponding graphs. Data bases for citation networks and metabolic
networks together with simulation results from the growing network model
\cite{barab} are probed. For completeness and comparisons lattice, random,
small-world models are also investigated. We find that is around 3 for
citation and metabolic networks, which is significantly different from the
growing network model, for which is approximately 7.5. This signals a
substantial difference in network topology despite the observed similarities in
vertex order distributions. In addition, the diffusion analysis indicates that
whereas the citation networks are tree-like in structure, the metabolic
networks contain many loops.Comment: 11 pages, 3 figure
Nonequilibrium Phase Transitions in Models of Aggregation, Adsorption, and Dissociation
We study nonequilibrium phase transitions in a mass-aggregation model which
allows for diffusion, aggregation on contact, dissociation, adsorption and
desorption of unit masses. We analyse two limits explicitly. In the first case
mass is locally conserved whereas in the second case local conservation is
violated. In both cases the system undergoes a dynamical phase transition in
all dimensions. In the first case, the steady state mass distribution decays
exponentially for large mass in one phase, and develops an infinite aggregate
in addition to a power-law mass decay in the other phase. In the second case,
the transition is similar except that the infinite aggregate is missing.Comment: Major revision of tex
Car-oriented mean-field theory for traffic flow models
We present a new analytical description of the cellular automaton model for
single-lane traffic. In contrast to previous approaches we do not use the
occupation number of sites as dynamical variable but rather the distance
between consecutive cars. Therefore certain longer-ranged correlations are
taken into account and even a mean-field approach yields non-trivial results.
In fact for the model with the exact solution is reproduced. For
the fundamental diagram shows a good agreement with results from
simulations.Comment: LaTex, 10 pages, 2 postscript figure
Communication and optimal hierarchical networks
We study a general and simple model for communication processes. In the
model, agents in a network (in particular, an organization) interchange
information packets following simple rules that take into account the limited
capability of the agents to deal with packets and the cost associated to the
existence of open communication channels. Due to the limitation in the
capability, the network collapses under certain conditions. We focus on when
the collapse occurs for hierarchical networks and also on the influence of the
flatness or steepness of the structure. We find that the need for hierarchy is
related to the existence of costly connections.Comment: 7 pages, 2 figures. NATO ARW on Econophysic
Phase Transition in the Takayasu Model with Desorption
We study a lattice model where particles carrying different masses diffuse,
coalesce upon contact, and also unit masses adsorb to a site with rate or
desorb from a site with nonzero mass with rate . In the limit (without
desorption), our model reduces to the well studied Takayasu model where the
steady-state single site mass distribution has a power law tail for large mass. We show that varying the desorption rate induces
a nonequilibrium phase transition in all dimensions. For fixed , there is a
critical such that if , the steady state mass distribution,
for large as in the Takayasu case. For , we
find where is a new exponent, while for
, for large . The model is studied
analytically within a mean field theory and numerically in one dimension.Comment: RevTex, 11 pages including 5 figures, submitted to Phys. Rev.
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