2 research outputs found
Hopf Bifurcations in Replicator Dynamics with Distributed Delays
In this paper, we study the existence and the property of the Hopf
bifurcation in the two-strategy replicator dynamics with distributed delays. In
evolutionary games, we assume that a strategy would take an uncertain time
delay to have a consequence on the fitness (or utility) of the players. As the
mean delay increases, a change in the stability of the equilibrium (Hopf
bifurcation) may occur at which a periodic oscillation appears. We consider
Dirac, uniform, Gamma, and discrete delay distributions, and we use the
Poincar\'e- Lindstedt's perturbation method to analyze the Hopf bifurcation.
Our theoretical results are corroborated with numerical simulations
Global Convergence for Replicator Dynamics of Repeated Snowdrift Games
To understand the emergence and sustainment of cooperative behavior in
interacting collectives, we perform global convergence analysis for replicator
dynamics of a large, well-mixed population of individuals playing a repeated
snowdrift game with four typical strategies, which are always cooperate (ALLC),
tit-for-tat (TFT), suspicious tit-for-tat (STFT) and always defect (ALLD). The
dynamical model is a three-dimensional ODE system that is parameterized by the
payoffs of the base game. Instead of routine searches for evolutionarily stable
strategies and sets, we expand our analysis to determining the asymptotic
behavior of solution trajectories starting from any initial state, and in
particular show that for the full range of payoffs, every trajectory of the
system converges to an equilibrium point. The convergence results highlight
three findings that are of particular importance for understanding the
cooperation mechanisms among self-interested agents playing repeated snowdrift
games. First, the inclusion of TFT- and STFT-players, the two types of
conditional strategy players in the game, increases the share of cooperators of
the overall population compared to the situation when the population consists
of only ALLC- and ALLD-players. This confirms findings in biology and sociology
that reciprocity may promote cooperation in social collective actions, such as
reducing traffic jams and division of labor, where each individual may gain
more to play the opposite of what her opponent chooses. Second, surprisingly
enough, regardless of the payoffs, there always exists a set of initial
conditions under which ALLC players do not vanish in the long run, which does
not hold for all the other three types of players. So an ALLC-player, although
perceived as the one that can be easily taken advantage of in snowdrift games,
has certain endurance in the long run