3,553 research outputs found
Evolutionary game theory: Temporal and spatial effects beyond replicator dynamics
Evolutionary game dynamics is one of the most fruitful frameworks for
studying evolution in different disciplines, from Biology to Economics. Within
this context, the approach of choice for many researchers is the so-called
replicator equation, that describes mathematically the idea that those
individuals performing better have more offspring and thus their frequency in
the population grows. While very many interesting results have been obtained
with this equation in the three decades elapsed since it was first proposed, it
is important to realize the limits of its applicability. One particularly
relevant issue in this respect is that of non-mean-field effects, that may
arise from temporal fluctuations or from spatial correlations, both neglected
in the replicator equation. This review discusses these temporal and spatial
effects focusing on the non-trivial modifications they induce when compared to
the outcome of replicator dynamics. Alongside this question, the hypothesis of
linearity and its relation to the choice of the rule for strategy update is
also analyzed. The discussion is presented in terms of the emergence of
cooperation, as one of the current key problems in Biology and in other
disciplines.Comment: Review, 48 pages, 26 figure
Altruistic behavior pays, or the importance of fluctuations in evolutionary game theory
Human behavior is one of the main problems for evolution, as it is often the
case that human actions are disadvantageous for the self and advantageous for
other people. Behind this puzzle are our beliefs about rational behavior, based
on game theory. Here we show that by going beyond the standard game-theoretical
conventions, apparently altruistic behavior can be understood as
self-interested. We discuss in detail an example related to the so called
Ultimatum game and illustrate the appearance of altruistic behavior induced by
fluctuations. In addition, we claim that in general settings, fluctuations play
a very relevant role, and we support this claim by considering a completely
different example, namely the Stag-Hunt game.Comment: For the proceedings of the 8th Granada Seminar on Computational
Physics (AIP Proceedeings Series
Imperfect Imitation Can Enhance Cooperation
The promotion of cooperation on spatial lattices is an important issue in
evolutionary game theory. This effect clearly depends on the update rule: it
diminishes with stochastic imitative rules whereas it increases with
unconditional imitation. To study the transition between both regimes, we
propose a new evolutionary rule, which stochastically combines unconditional
imitation with another imitative rule. We find that, surprinsingly, in many
social dilemmas this rule yields higher cooperative levels than any of the two
original ones. This nontrivial effect occurs because the basic rules induce a
separation of timescales in the microscopic processes at cluster interfaces.
The result is robust in the space of 2x2 symmetric games, on regular lattices
and on scale-free networks.Comment: 4 pages, 4 figure
Non-covalent interactions at electrochemical interfaces : one model fits all?
Acknowledgements Funding from the DGI (Spanish Ministry of Education and Science) through Project CTQ2009-07017 is gratefully acknowledged. E.P.M.L. wishes to thank the Universidad Nacional de Co´rdoba, Argentina, for a grant within the ‘‘Programa de Movilidad Internacional de Profesores Cuarto Centenario’’.Peer reviewedPublisher PD
A density functional theory for general hard-core lattice gases
We put forward a general procedure to obtain an approximate free energy
density functional for any hard-core lattice gas, regardless of the shape of
the particles, the underlying lattice or the dimension of the system. The
procedure is conceptually very simple and recovers effortlessly previous
results for some particular systems. Also, the obtained density functionals
belong to the class of fundamental measure functionals and, therefore, are
always consistent through dimensional reduction. We discuss possible extensions
of this method to account for attractive lattice models.Comment: 4 pages, 1 eps figure, uses RevTeX
Continuous phase transition in polydisperse hard-sphere mixture
In a previous paper (J. Zhang {\it et al.}, J. Chem. Phys. {\bf 110}, 5318
(1999)) we introduced a model for polydisperse hard sphere mixtures that is
able to adjust its particle-size distribution. Here we give the explanation of
the questions that arose in the previous description and present a consistent
theory of the phase transition in this system, based on the Percus-Yevick
equation of state. The transition is continuous, and like Bose-Einstein
condensation a macroscopic aggregate is formed due to the microscopic
interactions. A BMCSL-like treatment leads to the same conclusion with slightly
more accurate predictions.Comment: 7 pages including 5 figures in revte
MIGRACIÓN: RETOS Y RESPUESTAS
Apenas cuatro milenios de vida sedentaria, nos han hecho
olvidar cientos de miles de años en los que el hombre era
nómada y libre para deambular por el entonces ancho mundo
libre de fronteras en búsqueda de espacios vitales donde la generosa
naturaleza le proporcionara alimento y refugio. El descubrimiento
de la agricultura dio comienzo al proceso sedentario y a la
aparición del fenómeno urbano y con ello vinieron los estados y
luego los imperios y también las fronteras y los consiguientes pasaportes
y salvoconductos. Nuestros inquietos genes del nomadismo
se volvieron poco a poco recesivos, dando paso a los genes
dominantes del quieto burgués de la vida cómoda y bien instalada
de la propiedad privada, de las patentes. Nos volvimos territoriales
y como ciertos animales domésticos marcamos las esquinas con
nuestros olores, colores y lenguajes a fin de dejar bien claro que
esto es nuestro y solo nuestro
Fluid-fluid phase separation in hard spheres with a bimodal size distribution
The effect of polydispersity on the phase behaviour of hard spheres is
examined using a moment projection method. It is found that the
Boublik-Mansoori-Carnahan-Starling-Leland equation of state shows a spinodal
instability for a bimodal distribution if the large spheres are sufficiently
polydisperse, and if there is sufficient disparity in mean size between the
small and large spheres. The spinodal instability direction points to the
appearance of a very dense phase of large spheres.Comment: 7 pages, 3 figures, moderately REVISED following referees' comments
(original was 4 pages, 3 postscript figures
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