9 research outputs found
Evolution of economic entities under heterogeneous political/environmental conditions within a Bak-Sneppen-like dynamics
A model for economic behavior, under heterogeneous spatial economic
conditions is developed. The role of selection pressure in a Bak-Sneppen-like
dynamics with entity diffusion on a lattice is studied by Monte-Carlo
simulation taking into account business rule(s), like enterprise - enterprise
short range location "interaction"(s), business plan(s) through spin-offs or
merging and enterprise survival evolution law(s). It is numerically found that
the model leads to a sort of phase transition for the fitness gap as a function
of the selection pressure.Comment: 6 figures. to be published in Physica
The Role of Dominant Mutations in the Population Expansion
Abstract. We have studied the dynamics of expansion of diploid, sexually reproducing populations onto new territories demanding different genetic adaptations. Populations succeeded in the new habitats if the mutations of alleles responsible for adaptation to the new conditions were recessive. If behind the hostile territory another friendly habitat exists, several different scenarios are possible, including one in which the middle, most hostile, habitat remains empty, separating populated two, more friendly, ones
Monte Carlo simulations of the inside-intron recombination
Biological genomes are divided into coding and non-coding regions. Introns
are non-coding parts within genes, while the remaining non-coding parts are
intergenic sequences. To study the evolutionary significance of recombination
inside introns we have used two models based on the Monte Carlo method. In our
computer simulations we have implemented the internal structure of genes by
declaring the probability of recombination between exons. One situation when
inside-intron recombination is advantageous is recovering functional genes by
combining proper exons dispersed in the genetic pool of the population after a
long period without selection for the function of the gene. Populations have to
pass through the bottleneck, then. These events are rather rare and we have
expected that there should be other phenomena giving profits from the
inside-intron recombination. In fact we have found that inside-intron
recombination is advantageous only in the case when after recombination,
besides the recombinant forms, parental haplotypes are available and selection
is set already on gametes.Comment: 12 pages inc. 5 Figs., for Int. J. Mod. Phys. C 17, issue 4 (2006
Simple Model for the Dynamics of Correlations in the Evolution of Economic Entities Under Varying Economic Conditions
From some observations on economic behaviors, in particular changing economic
conditions with time and space, we develop a very simple model for the
evolution of economic entities within a geographical type of framework. We
raise a few questions and attempt to investigate whether some of them can be
tackled by our model. Several cases of interest are reported. It is found that
the model even in its simple forms can lead to a large variety of situations,
including: delocalization and cycles, but also pre-chaotic behavior.Comment: Presented at Bali IEC02 symposium, Aug. 2002; submitted to Physica A
; 8 pages, 5 figure
Percolation and jamming in random sequential adsorption of linear segments on square lattice
We present the results of study of random sequential adsorption of linear
segments (needles) on sites of a square lattice. We show that the percolation
threshold is a nonmonotonic function of the length of the adsorbed needle,
showing a minimum for a certain length of the needles, while the jamming
threshold decreases to a constant with a power law. The ratio of the two
thresholds is also nonmonotonic and it remains constant only in a restricted
range of the needles length. We determine the values of the correlation length
exponent for percolation, jamming and their ratio
Complex population dynamics as a competition between multiple time-scale phenomena
The role of the selection pressure and mutation amplitude on the behavior of
a single-species population evolving on a two-dimensional lattice, in a
periodically changing environment, is studied both analytically and
numerically. The mean-field level of description allows to highlight the
delicate interplay between the different time-scale processes in the resulting
complex dynamics of the system. We clarify the influence of the amplitude and
period of the environmental changes on the critical value of the selection
pressure corresponding to a phase-transition "extinct-alive" of the population.
However, the intrinsic stochasticity and the dynamically-built in correlations
among the individuals, as well as the role of the mutation-induced variety in
population's evolution are not appropriately accounted for. A more refined
level of description, which is an individual-based one, has to be considered.
The inherent fluctuations do not destroy the phase transition "extinct-alive",
and the mutation amplitude is strongly influencing the value of the critical
selection pressure. The phase diagram in the plane of the population's
parameters -- selection and mutation is discussed as a function of the
environmental variation characteristics. The differences between a smooth
variation of the environment and an abrupt, catastrophic change are also
addressesd.Comment: 15 pages, 12 figures. Accepted for publication in Phys. Rev.