9,921 research outputs found
Evolution of cooperation in spatial traveler's dilemma game
Traveler's dilemma (TD) is one of social dilemmas which has been well studied
in the economics community, but it is attracted little attention in the physics
community. The TD game is a two-person game. Each player can select an integer
value between and () as a pure strategy. If both of them select
the same value, the payoff to them will be that value. If the players select
different values, say and (), then the payoff to the
player who chooses the small value will be and the payoff to the other
player will be . We term the player who selects a large value as the
cooperator, and the one who chooses a small value as the defector. The reason
is that if both of them select large values, it will result in a large total
payoff. The Nash equilibrium of the TD game is to choose the smallest value
. However, in previous behavioral studies, players in TD game typically
select values that are much larger than , and the average selected value
exhibits an inverse relationship with . To explain such anomalous behavior,
in this paper, we study the evolution of cooperation in spatial traveler's
dilemma game where the players are located on a square lattice and each player
plays TD games with his neighbors. Players in our model can adopt their
neighbors' strategies following two standard models of spatial game dynamics.
Monte-Carlo simulation is applied to our model, and the results show that the
cooperation level of the system, which is proportional to the average value of
the strategies, decreases with increasing until is greater than the
threshold where cooperation vanishes. Our findings indicate that spatial
reciprocity promotes the evolution of cooperation in TD game and the spatial TD
game model can interpret the anomalous behavior observed in previous behavioral
experiments
Scalable and Effective Conductance-based Graph Clustering
Conductance-based graph clustering has been recognized as a fundamental
operator in numerous graph analysis applications. Despite the significant
success of conductance-based graph clustering, existing algorithms are either
hard to obtain satisfactory clustering qualities, or have high time and space
complexity to achieve provable clustering qualities. To overcome these
limitations, we devise a powerful \textit{peeling}-based graph clustering
framework \textit{PCon}. We show that many existing solutions can be reduced to
our framework. Namely, they first define a score function for each vertex, then
iteratively remove the vertex with the smallest score. Finally, they output the
result with the smallest conductance during the peeling process. Based on our
framework, we propose two novel algorithms \textit{PCon\_core} and
\emph{PCon\_de} with linear time and space complexity, which can efficiently
and effectively identify clusters from massive graphs with more than a few
billion edges. Surprisingly, we prove that \emph{PCon\_de} can identify
clusters with near-constant approximation ratio, resulting in an important
theoretical improvement over the well-known quadratic Cheeger bound. Empirical
results on real-life and synthetic datasets show that our algorithms can
achieve 542 times speedup with a high clustering accuracy, while using
1.47.8 times less memory than the baseline algorithms
Disorder-induced linear magnetoresistance in AlO/SrTiO heterostructures
The unsaturated linear magnetoresistance (LMR) has attracted widely attention
because of potential applications and fundamental interest. By controlling the
growth temperature, we realized the metal-to-insulator transition in
AlO/SrTiO heterostructures. The LMR is observed in metallic samples
with the electron mobility varying over three orders of magnitude. The observed
LMR cannot be explained by the guiding center diffusion model even in samples
with very high mobility. The slope of the observed LMR is proportional to the
Hall mobility, and the crossover field, indicating a transition from quadratic
(at low fields) to linear (at high fields) field dependence, is proportional to
the inverse Hall mobility. This signifies that the classical model is valid to
explain the observed LMR. More importantly, we develop an analytical expression
according to the effective-medium theory that is equivalent to the classical
model. And the analytical expression describes the LMR data very well,
confirming the validity of the classical model.Comment: 22 Pages, 4 figures, 1 tabl
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