9,924 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
Rewarding cooperation in social dilemmas
One of the most direct human mechanisms of promoting cooperation is rewarding it. We study
the effect of sharing a reward among cooperators in the most stringent form of social dilemma.
Thus, individuals confront a new dilemma: on the one hand, they may be inclined to choose the
shared reward despite the possibility of being exploited by defectors; on the other hand, if too
many players do that, cooperators will obtain a poor reward and defectors will outperform them.
By appropriately tuning the amount to be shared we can cast a vast variety of scenarios,
including traditional ones in the study of cooperation as well as more complex situations where
unexpected behavior can occur. We provide a complete classification of the equilibria of the nplayer
game as well as of the evolutionary dynamics. Beyond, we extend our analysis to a
general class of public good games where competition among individuals with the same strategy
exists
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
Assessing the impact of different nominal anchors on the credibility of stabilisation programmes
The paper compares the impact of announcing exchange-rate-based versus money-based stabilisation programmes in a cross-section of countries. The analysis finds that the effect of announcing exchange-rate-based programmes is more credible, in terms of reducing inflation inertia, than the outcome associated with implementing money-based programmes. But the gap between the magnitudes of the impacts from implementing the different strategies has been falling since the 1970s.Inflation stabilisation; credibility; nominal anchors; IMF programmes
Coupled electric and magnetic dipole formulation for planar arrays of dipolar particles: metasurfaces with various electric and/or magnetic meta-atoms per unit cell
The optical properties of infinite planar array of scattering particles,
metasurfaces and metagratings, are attracting special attention lately for
their rich phenomenology, including both plasmonic and high-refractive-index
dielectric meta-atoms with a variety of electric and magnetic resonant
responses. Herein we derive a coupled electric and magnetic dipole (CEMD)
analytical formulation to describe the reflection and transmission of such
periodic arrays, including specular and diffractive orders, valid in the
spectral regimes where only dipolar multipoles are needed. Electric and/or
magnetic dipoles with all three orientations arising in turn from a single or
various meta-atoms per unit cell are considered. The 2D lattice Green function
is rewritten in terms of a 1D (chain) version that fully converges and can be
easily calculated. Modes emerging as poles of such lattice Green function can
be extracted. This formulation can be applied to investigate a wealth of
plasmonic, all-dielectric, and hybrid metasurfaces/metagratings of interest
throughout the electromagnetic spectrum.Comment: 8 pages, 4 figure
Efficient synthesis of single-chain polymer nanoparticles via amide formation
This is an open access article distributed under the Creative Commons Attribution License.Single-chain technology (SCT) allows the transformation of individual polymer chains to folded/collapsed unimolecular soft nanoparticles. In this work we contribute to the enlargement of the SCT toolbox by demonstrating the efficient synthesis of single-chain polymer nanoparticles (SCNPs) via intrachain amide formation. In particular, we exploit cross-linking between active methylene groups and isocyanate moieties as powerful >click> chemistry driving force for SCNP construction. By employing poly(methyl methacrylate)- (PMMA-) based copolymers bearing β-ketoester units distributed randomly along the copolymer chains and bifunctional isocyanate cross-linkers, SCNPs were successfully synthesized at r.t. under appropriate reaction conditions. Characterization of the resulting SCNPs was carried out by means of a combination of techniques including size exclusion chromatography (SEC), infrared (IR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, dynamic light scattering (DLS), and elemental analysis (EA).Financial support from Projects MAT2012-31088 (MINECO), T-654-13 (GV), and S-PE13UN034 (GV) is acknowledged. Ana Sanchez-Sanchez thanks the Ph.D. grant support of Basque Government.Peer Reviewe
Degenerate optical memory effect in dielectric films with randomly rough surfaces
9 págs.; 6 figs.By means of perturbation theory we calculate the angular intensity correlations of linearly polarized electromagnetic waves scattered from a thin dielectric film deposited on a planar perfectly conducting substrate. The illuminated surface is a one-dimensional, randomly rough surface with a power spectrum given either by a Gaussian, or by a rectangle defined to enhance the coupling into guided waves. The dielectric film supports, at least, two guided waves in the absence of the roughness that have distinct wave numbers at the frequency ω of the incident wave. We analyze the angular dependence of the optical memory effect: In addition to its two well known peaks, we demonstrate that, due to degeneracy of the excitation of guided waves, there appear two pairs of peaks symmetrically located about the former absolute maxima at positions related to the difference between the guided wave numbers. This degenerate memory effect is shown to be a multiple scattering effect. ©1997 American Physical SocietyThis work was supported by the Consejo Superior de Investigaciones
CientÃficas and the Dirección General de Investigación CientÃfica y Técnica through Grant No. PB93-
0973-C02-02.Peer Reviewe
The second Feng-Rao number for codes coming from telescopic semigroups
In this manuscript we show that the second Feng-Rao number of any telescopic
numerical semigroup agrees with the multiplicity of the semigroup. To achieve
this result we first study the behavior of Ap\'ery sets under gluings of
numerical semigroups. These results provide a bound for the second Hamming
weight of one-point Algebraic Geometry codes, which improves upon other
estimates such as the Griesmer Order Bound
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