39 research outputs found
Imitate or innovate: Competition of strategy updating attitudes in spatial social dilemma games
Evolution is based on the assumption that competing players update their
strategies to increase their individual payoffs. However, while the applied
updating method can be different, most of previous works proposed uniform
models where players use identical way to revise their strategies. In this work
we explore how imitation-based or learning attitude and innovation-based or
myopic best response attitude compete for space in a complex model where both
attitudes are available. In the absence of additional cost the best response
trait practically dominates the whole snow-drift game parameter space which is
in agreement with the average payoff difference of basic models. When
additional cost is involved then the imitation attitude can gradually invade
the whole parameter space but this transition happens in a highly nontrivial
way. However, the role of competing attitudes is reversed in the stag-hunt
parameter space where imitation is more successful in general. Interestingly, a
four-state solution can be observed for the latter game which is a consequence
of an emerging cyclic dominance between possible states. These phenomena can be
understood by analyzing the microscopic invasion processes, which reveals the
unequal propagation velocities of strategies and attitudes.Comment: 7 two-column pages, 6 figures, accepted for publication in EP
Size scaling of failure strength at high disorder
We investigate how the macroscopic response and the size scaling of the
ultimate strength of materials change when their local strength is sampled from
a fat-tailed distribution and the degree of disorder is varied in a broad
range. Using equal and localized load sharing in a fiber bundle model, we
demonstrate that a transition occurs from a perfectly brittle to a
quasi-brittle behaviour as the amount of disorder is gradually increased. When
the load sharing is localized the high load concentration around failed regions
make the system more prone to failure so that a higher degree of disorder is
required for stabilization. Increasing the system size at a fixed degree of
disorder an astonishing size effect is obtained: at small sizes the ultimate
strength of the system increases with its size, the usual decreasing behaviour
sets on only beyond a characteristic system size. The increasing regime of the
size effect prevails even for localized load sharing, however, above the
characteristic system size the load concentration results in a substantial
strength reduction compared to equal load sharing. We show that an adequate
explanation of the results can be obtained based on the extreme order
statistics of fibers' strength.Comment: 24 pages, 7 figure