7,912 research outputs found
Quantum loops in radiative decays of the and axial-vector mesons
A previous model where the low-lying axial-vector mesons are dynamically
generated, implementing unitarity in coupled channels in the
vector-pseudoscalar () meson interaction, is applied to evaluate the decay
widths of the a_1(1260)b_1(1235)\pi\gammaa_1b_1VPb_1a_1$ case.Comment: 16 pages, 4 figurs Added extra discussio
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
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
Time Scales in Evolutionary Dynamics
Evolutionary game theory has traditionally assumed that all individuals in a
population interact with each other between reproduction events. We show that
eliminating this restriction by explicitly considering the time scales of
interaction and selection leads to dramatic changes in the outcome of
evolution. Examples include the selection of the inefficient strategy in the
Harmony and Stag-Hunt games, and the disappearance of the coexistence state in
the Snowdrift game. Our results hold for any population size and in the
presence of a background of fitness.Comment: Final version with minor changes, accepted for publication in
Physical Review Letter
The envelope of the power spectra of over a thousand \delta Scuti stars. The - scaling relation
CoRoT and Kepler high-precision photometric data allowed the detection and
characterization of the oscillation parameters in stars other than the Sun.
Moreover, thanks to the scaling relations, it is possible to estimate masses
and radii for thousands of solar-type oscillating stars. Recently, a \Delta\nu
- \rho relation has been found for \delta Scuti stars. Now, analyzing several
hundreds of this kind of stars observed with CoRoT and Kepler, we present an
empiric relation between their frequency at maximum power of their oscillation
spectra and their effective temperature. Such a relation can be explained with
the help of the \kappa-mechanism and the observed dispersion of the residuals
is compatible with they being caused by the gravity-darkening effect
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