47,282 research outputs found
Ising Ferromagnet: Zero-Temperature Dynamic Evolution
The dynamic evolution at zero temperature of a uniform Ising ferromagnet on a
square lattice is followed by Monte Carlo computer simulations. The system
always eventually reaches a final, absorbing state, which sometimes coincides
with a ground state (all spins parallel), and sometimes does not (parallel
stripes of spins up and down). We initiate here the numerical study of
``Chaotic Time Dependence'' (CTD) by seeing how much information about the
final state is predictable from the randomly generated quenched initial state.
CTD was originally proposed to explain how nonequilibrium spin glasses could
manifest equilibrium pure state structure, but in simpler systems such as
homogeneous ferromagnets it is closely related to long-term predictability and
our results suggest that CTD might indeed occur in the infinite volume limit.Comment: 14 pages, Latex with 8 EPS figure
Simulating Male Selfish Strategy in Reproduction Dispute
We introduce into the Penna Model for biological ageing one of the possible
male mechanisms used to maximize the ability of their sperm to compete with
sperm from other males. Such a selfish mechanism increases the male
reproduction success but may decrease the survival probability of the whole
female population, depending on how it acts. We also find a dynamic phase
transition induced by the existence of an absorbing state where no selfish
males survive.Comment: 7 pages, latex including 2 eps figure
Lattice Simulation of Nuclear Multifragmentation
Motivated by the decade-long debate over the issue of criticality supposedly
observed in nuclear multifragmentation, we propose a dynamical lattice model to
simulate the phenomenon. Its Ising Hamiltonian mimics a short range attractive
interaction which competes with a thermal-like dissipative process. The results
here presented, generated through an event-by-event analysis, are in agreement
with both experiment and those produced by a percolative (non-dynamical) model.Comment: 8 pages, 3 figure
Towards a knowledge-based system to assist the Brazilian data-collecting system operation
A study is reported which was carried out to show how a knowledge-based approach would lead to a flexible tool to assist the operation task in a satellite-based environmental data collection system. Some characteristics of a hypothesized system comprised of a satellite and a network of Interrogable Data Collecting Platforms (IDCPs) are pointed out. The Knowledge-Based Planning Assistant System (KBPAS) and some aspects about how knowledge is organized in the IDCP's domain are briefly described
Scaling behavior of explosive percolation on the square lattice
Clusters generated by the product-rule growth model of Achlioptas, D'Souza,
and Spencer on a two-dimensional square lattice are shown to obey qualitatively
different scaling behavior than standard (random growth) percolation. The
threshold with unrestricted bond placement (allowing loops) is found precisely
using several different criteria based upon both moments and wrapping
probabilities, yielding p_c = 0.526565 +/- 0.000005, consistent with the recent
result of Radicchi and Fortunato. The correlation-length exponent nu is found
to be close to 1. The qualitative difference from regular percolation is shown
dramatically in the behavior of the percolation probability P_(infinity) (size
of largest cluster), the susceptibility, and of the second moment of finite
clusters, where discontinuities appears at the threshold. The critical
cluster-size distribution does not follow a consistent power-law for the range
of system sizes we study L 2
for larger L.Comment: v2: Updated results in original version with new data; expanded
discussion. v3: Resubmitted version. New figures, reference
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