13,361 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
Phase transitions in a holographic s+p model with backreaction
In a previous paper (arXiv:1309.2204, JHEP 1311 (2013) 087), we present a
holographic s+p superconductor model with a scalar triplet charged under an
SU(2) gauge field in the bulk. We also study the competition and coexistence of
the s-wave and p-wave orders in the probe limit. In this work we continue to
study the model by considering the full back-reaction The model shows a rich
phase structure and various condensate behaviors such as the "n-type" and
"u-type" ones, which are also known as reentrant phase transitions in condensed
matter physics. The phase transitions to the p-wave phase or s+p coexisting
phase become first order in strong back-reaction cases. In these first order
phase transitions, the free energy curve always forms a swallow tail shape, in
which the unstable s+p solution can also play an important role. The phase
diagrams of this model are given in terms of the dimension of the scalar order
and the temperature in the cases of eight different values of the back reaction
parameter, which show that the region for the s+p coexisting phase is enlarged
with a small or medium back reaction parameter, but is reduced in the strong
back-reaction cases.Comment: 15 pages(two-column), 9 figure
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