1,810 research outputs found
Survival of dominated strategies under evolutionary dynamics
We prove that any deterministic evolutionary dynamic satisfying four mild requirements fails to eliminate strictly dominated strategies in some games. We also show that existing elimination results for evolutionary dynamics are not robust to small changes in the specifications of the dynamics. Numerical analysis reveals that dominated strategies can persist at nontrivial frequencies even when the level of domination is not small.Evolutionary game theory, evolutionary game dynamics, nonconvergnece, dominated strategies
Dynamical Organization of Cooperation in Complex Topologies
In this Letter, we study how cooperation is organized in complex topologies
by analyzing the evolutionary (replicator) dynamics of the Prisoner's Dilemma,
a two-players game with two available strategies, defection and cooperation,
whose payoff matrix favors defection. We show that, asymptotically, the
population is partitioned into three subsets: individuals that always cooperate
({\em pure cooperators}), always defect ({\em pure defectors}) and those that
intermittently change their strategy. In fact the size of the latter set is the
biggest for a wide range of the "stimulus to defect" parameter. While in
homogeneous random graphs pure cooperators are grouped into several clusters,
in heterogeneous scale-free (SF) networks they always form a single cluster
containing the most connected individuals (hubs). Our results give further
insights into why cooperation in SF networks is favored.Comment: 4 pages and 4 figures. Final version as published in Physical Review
Letter
Waste Wood Gasification: Distribution of Nitrogen, Sulphur and Chlorine in a Dual Fluidised Bed Steam Gasifier
Waste wood was gasified in a dual fluidised bed gasifier in order to investigate the behaviour of waste fuels in this technology. The distribution of nitrogen, sulphur and chlorine between the gasifier and combustor of the dual bed system was studied to identify the requirements for gas cleaning devices. The gasification system is suitable for the use of waste wood. A slight adaption of the gas cleaning equipment was necessary compared to gasification of natural woody biomass
Sophisticated Imitation in Cyclic Games
Consider a large population of individuals that are repeatedly randomly matched to play a cyclic 2x2 game such as Matching Pennies with fixed roles assigned in the game. Some learn by sampling previous play of a finite number of other individuals in the same role. We analyze population dynamics under optimal boundedly rational behavior (in the sense of Schlag, 1998c). We find that long run play is close to the Nash equilibrium (when few individuals receive information) if and only if the sample size is greater than one.single sampling, multiple sampling, improving, sequential proportional observation, replicator dynamics, aggregate monotone dynamics, Evolutionary Game Theory, Matching Pennies
Resonance bifurcations from robust homoclinic cycles
We present two calculations for a class of robust homoclinic cycles with
symmetry Z_n x Z_2^n, for which the sufficient conditions for asymptotic
stability given by Krupa and Melbourne are not optimal.
Firstly, we compute optimal conditions for asymptotic stability using
transition matrix techniques which make explicit use of the geometry of the
group action.
Secondly, through an explicit computation of the global parts of the Poincare
map near the cycle we show that, generically, the resonance bifurcations from
the cycles are supercritical: a unique branch of asymptotically stable period
orbits emerges from the resonance bifurcation and exists for coefficient values
where the cycle has lost stability. This calculation is the first to explicitly
compute the criticality of a resonance bifurcation, and answers a conjecture of
Field and Swift in a particular limiting case. Moreover, we are able to obtain
an asymptotically-correct analytic expression for the period of the bifurcating
orbit, with no adjustable parameters, which has not proved possible previously.
We show that the asymptotic analysis compares very favourably with numerical
results.Comment: 24 pages, 3 figures, submitted to Nonlinearit
Equilibrium states for potentials with \sup\phi - \inf\phi < \htop(f)
In the context of smooth interval maps, we study an inducing scheme approach
to prove existence and uniqueness of equilibrium states for potentials
with he `bounded range' condition \sup \phi - \inf \phi < \htop, first used
by Hofbauer and Keller. We compare our results to Hofbauer and Keller's use of
Perron-Frobenius operators. We demonstrate that this `bounded range' condition
on the potential is important even if the potential is H\"older continuous. We
also prove analyticity of the pressure in this context.Comment: Added Lemma 6 to deal with the disparity between leading eigenvalues
and operator norms. Added extra references and corrected some typo
PNP PIN bipolar phototransistors for high-speed applications built in a 180nm CMOS process
AbstractThis work reports on three speed optimized pnp bipolar phototransistors build in a standard 180nm CMOS process using a special starting wafer. The starting wafer consists of a low doped p epitaxial layer on top of the p substrate. This low doped p epitaxial layer leads to a thick space-charge region between base and collector and thus to a high â3dB bandwidth at low collectorâemitter voltages. For a further increase of the bandwidth the presented phototransistors were designed with small emitter areas resulting in a small base-emitter capacitance. The three presented phototransistors were implemented in sizes of 40Ă40ÎŒm2 and 100Ă100ÎŒm2. Optical DC and AC measurements at 410nm, 675nm and 850nm were done for phototransistor characterization. Due to the speed optimized design and the layer structure of the phototransistors, bandwidths up to 76.9MHz and dynamic responsivities up to 2.89A/W were achieved. Furthermore simulations of the electric field strength and space-charge regions were done
Effekte des Ringschneidereinsatzes zur pfluglosen Boden-bearbeitung auf physikalische Eigenschaften sandiger Böden
Organic farming on sandy soils in Brandenburg is especially vulnerable to climate change impacts like drought and heavy rainfall. Reduced tillage is considered as one possible adaptation measure. For technical implementation the ring cutter allowing shallow non-inversion tillage with overall root-cutting is under investigation. Its effects on soil bulk density, soil organic matter content, root mass and soil water retention as well as the yield of winter rye were quantified. Results from the spring showed a significant accumulation of organic matter in the tilled top layer and both a significant increase of bulk density and a significant decrease of root mass in the non-tilled lower topsoil. Water retention in the non-tilled layer was reduced. The yield of winter rye was 27 % lower. Due to a compaction the non-tilled layer of the soil was less penetrable by roots. The showed results of only one date do not allow reasoning to a whole tillage system. In the present case it is recommended to loosen the compacted non-tilled layer with additional non-inversion tillage
Restricted connections among distinguished players support cooperation
We study the evolution of cooperation within the spatial prisoner's dilemma
game on a square lattice where a fraction of players can spread their
strategy more easily than the rest due to a predetermined larger teaching
capability. In addition, players characterized with the larger teaching
capability are allowed to temporarily link with distant opponents of the same
kind with probability , thus introducing shortcut connections among the
distinguished. We show that these additional temporary connections are able to
sustain cooperation throughout the whole range of the temptation to defect.
Remarkably, we observe that as the temptation to defect increases the optimal
decreases, and moreover, only minute values of warrant the best
promotion of cooperation. Our study thus indicates that influential individuals
must be few and sparsely connected in order for cooperation to thrive in a
defection prone environment.Comment: 6 two-column pages, 6 figures; accepted for publication in Physical
Review
Impact of aging on the evolution of cooperation in the spatial prisoner's dilemma game
Aging is always present, tailoring our interactions with others and
postulating a finite lifespan during which we are able to exercise them. We
consider the prisoner's dilemma game on a square lattice, and examine how
quenched age distributions and different aging protocols influence the
evolution of cooperation when taking the life experience and knowledge
accumulation into account as time passes. In agreement with previous studies,
we find that a quenched assignment of age to players, introducing heterogeneity
to the game, substantially promotes cooperative behavior. Introduction of aging
and subsequent death as a coevolutionary process may act detrimental on
cooperation but enhances it efficiently if the offspring of individuals that
have successfully passed their strategy is considered newborn. We study
resulting age distributions of players, and show that the heterogeneity is
vital yet insufficient for explaining the observed differences in cooperator
abundance on the spatial grid. The unexpected increment of cooperation levels
can be explained by a dynamical effect that has a highly selective impact on
the propagation of cooperator and defector states.Comment: 7 two-column pages, 5 figures; accepted for publication in Physical
Review
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