308 research outputs found
Non-equilibrium phase transition in a two-temperature lattice gas
A two-temperature lattice gas model with repulsive nearest-neighbour
interactions is studied using Monte Carlo simulations and dynamical mean-field
approximation. The evolution of the two-dimensional, half-filled system is
described by an anisotropic Kawasaki dynamics assuming that the hopping of
particles along the principal directions is governed by two heat baths at
different temperatures and . The system undergoes an order-disorder
phase transition as () is varied for sufficiently low fixed
(). The non-equilibrium phase transition remains continuous and the
critical behaviour belongs to the Ising universality class. The measure of
violation of the fluctuation-dissipation theorem can be controlled by the value
of the fixed temperature. We have found an exponential decay of spatial
correlations above the critical region in contrast to the two-temperature model
with attractive interactions.Comment: 7 pages, including 6 figures, to appear in Journal of Physics
Antisocial pool rewarding does not deter public cooperation
Rewarding cooperation is in many ways expected behaviour from social players.
However, strategies that promote antisocial behaviour are also surprisingly
common, not just in human societies, but also among eusocial insects and
bacteria. Examples include sanctioning of individuals who behave prosocially,
or rewarding of freeriders who do not contribute to collective enterprises. We
therefore study the public goods game with antisocial and prosocial pool
rewarding in order to determine the potential negative consequences on the
effectiveness of positive incentives to promote cooperation. Contrary to a
naive expectation, we show that the ability of defectors to distribute rewards
to their like does not deter public cooperation as long as cooperators are able
to do the same. Even in the presence of antisocial rewarding the spatial
selection for cooperation in evolutionary social dilemmas is enhanced. Since
the administration of rewards to either strategy requires a considerable degree
of aggregation, cooperators can enjoy the benefits of their prosocial
contributions as well as the corresponding rewards. Defectors when aggregated,
on the other hand, can enjoy antisocial rewards, but due to their lack of
contributions to the public good they ultimately succumb to their inherent
inability to secure a sustainable future. Strategies that facilitate the
aggregation of akin players, even if they seek to promote antisocial behaviour,
thus always enhance the long-term benefits of cooperation.Comment: 9 two-column pages, 5 figures; accepted for publication in
Proceedings of the Royal Society
Leaders should not be conformists in evolutionary social dilemmas
The most common assumption in evolutionary game theory is that players should
adopt a strategy that warrants the highest payoff. However, recent studies
indicate that the spatial selection for cooperation is enhanced if an
appropriate fraction of the population chooses the most common rather than the
most profitable strategy within the interaction range. Such conformity might be
due to herding instincts or crowd behavior in humans and social animals. In a
heterogeneous population where individuals differ in their degree, collective
influence, or other traits, an unanswered question remains who should conform.
Selecting conformists randomly is the simplest choice, but it is neither a
realistic nor the optimal one. We show that, regardless of the source of
heterogeneity and game parametrization, socially the most favorable outcomes
emerge if the masses conform. On the other hand, forcing leaders to conform
significantly hinders the constructive interplay between heterogeneity and
coordination, leading to evolutionary outcomes that are worse still than if
conformists were chosen randomly. We conclude that leaders must be able to
create a following for network reciprocity to be optimally augmented by
conformity. In the opposite case, when leaders are castrated and made to
follow, the failure of coordination impairs the evolution of cooperation.Comment: 7 two-column pages, 4 figures; accepted for publication in Scientific
Reports [related work available at arXiv:1412.4113
Costly hide and seek pays: Unexpected consequences of deceit in a social dilemma
Deliberate deceptiveness intended to gain an advantage is commonplace in
human and animal societies. In a social dilemma, an individual may only pretend
to be a cooperator to elicit cooperation from others, while in reality he is a
defector. With this as motivation, we study a simple variant of the
evolutionary prisoner's dilemma game entailing deceitful defectors and
conditional cooperators that lifts the veil on the impact of such two-faced
behavior. Defectors are able to hide their true intentions at a personal cost,
while conditional cooperators are probabilistically successful at identifying
defectors and act accordingly. By focusing on the evolutionary outcomes in
structured populations, we observe a number of unexpected and counterintuitive
phenomena. We show that deceitful behavior may fare better if it is costly, and
that a higher success rate of identifying defectors does not necessarily favor
cooperative behavior. These results are rooted in the spontaneous emergence of
cycling dominance and spatial patterns that give rise to fascinating phase
transitions, which in turn reveal the hidden complexity behind the evolution of
deception.Comment: 16 pages, 8 figures; accepted for publication in New Journal of
Physic
Benefits of tolerance in public goods games
Leaving the joint enterprise when defection is unveiled is always a viable
option to avoid being exploited. Although loner strategy helps the population
not to be trapped into the tragedy of the commons state, it could offer only a
modest income for non-participants. In this paper we demonstrate that showing
some tolerance toward defectors could not only save cooperation in harsh
environments, but in fact results in a surprisingly high average payoff for
group members in public goods games. Phase diagrams and the underlying spatial
patterns reveal the high complexity of evolving states where cyclic dominant
strategies or two-strategy alliances can characterize the final state of
evolution. We identify microscopic mechanisms which are responsible for the
superiority of global solutions containing tolerant players. This phenomenon is
robust and can be observed both in well-mixed and in structured populations
highlighting the importance of tolerance in our everyday life.Comment: 10 two-column pages, 8 figures; accepted for publication in Physical
Review
Conformity enhances network reciprocity in evolutionary social dilemmas
The pursuit of highest payoffs in evolutionary social dilemmas is risky and
sometimes inferior to conformity. Choosing the most common strategy within the
interaction range is safer because it ensures that the payoff of an individual
will not be much lower than average. Herding instincts and crowd behavior in
humans and social animals also compel to conformity on their own right.
Motivated by these facts, we here study the impact of conformity on the
evolution of cooperation in social dilemmas. We show that an appropriate
fraction of conformists within the population introduces an effective surface
tension around cooperative clusters and ensures smooth interfaces between
different strategy domains. Payoff-driven players brake the symmetry in favor
of cooperation and enable an expansion of clusters past the boundaries imposed
by traditional network reciprocity. This mechanism works even under the most
testing conditions, and it is robust against variations of the interaction
network as long as degree-normalized payoffs are applied. Conformity may thus
be beneficial for the resolution of social dilemmas.Comment: 8 two-column pages, 5 figures; accepted for publication in Journal of
the Royal Society Interfac
Congestion phenomena caused by matching pennies in evolutionary games
Evolutionary social dilemma games are extended by an additional
matching-pennies game that modifies the collected payoffs. In a spatial version
players are distributed on a square lattice and interact with their neighbors.
Firstly, we show that the matching-pennies game can be considered as the
microscopic force of the Red Queen effect that breaks the detailed balance and
induces eddies in the microscopic probability currents if the strategy update
is analogous to the Glauber dynamics for the kinetic Ising models. The
resulting loops in probability current breaks symmetry between the
chessboard-like arrangements of strategies via a bottleneck effect occurring
along the four-edge loops in the microscopic states. The impact of this
congestion is analogous to the application of a staggered magnetic field in the
Ising model, that is, the order-disorder critical transition is wiped out by
noise. It is illustrated that the congestion induced symmetry breaking can be
beneficial for the whole community within a certain region of parameters.Comment: 7 pages, 6 figure
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