1,416 research outputs found
An evolutionary model for simple ecosystems
In this review some simple models of asexual populations evolving on smooth
landscapes are studied. The basic model is based on a cellular automaton, which
is analyzed here in the spatial mean-field limit. Firstly, the evolution on a
fixed fitness landscape is considered. The correspondence between the time
evolution of the population and equilibrium properties of a statistical
mechanics system is investigated, finding the limits for which this mapping
holds. The mutational meltdown, Eigen's error threshold and Muller's ratchet
phenomena are studied in the framework of a simplified model. Finally, the
shape of a quasi-species and the condition of coexistence of multiple species
in a static fitness landscape are analyzed. In the second part, these results
are applied to the study of the coexistence of quasi-species in the presence of
competition, obtaining the conditions for a robust speciation effect in asexual
populations.Comment: 36 pages, including 16 figures, to appear in Annual Review of
Computational Physics, D. Stauffer (ed.), World Scientific, Singapor
Nonequilibrium Critical Phenomena and Phase Transitions into Absorbing States
This review addresses recent developments in nonequilibrium statistical
physics. Focusing on phase transitions from fluctuating phases into absorbing
states, the universality class of directed percolation is investigated in
detail. The survey gives a general introduction to various lattice models of
directed percolation and studies their scaling properties, field-theoretic
aspects, numerical techniques, as well as possible experimental realizations.
In addition, several examples of absorbing-state transitions which do not
belong to the directed percolation universality class will be discussed. As a
closely related technique, we investigate the concept of damage spreading. It
is shown that this technique is ambiguous to some extent, making it impossible
to define chaotic and regular phases in stochastic nonequilibrium systems.
Finally, we discuss various classes of depinning transitions in models for
interface growth which are related to phase transitions into absorbing states.Comment: Review article, revised version, LaTeX, 153 pages, 63 encapsulated
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