7,766 research outputs found
Similarity based cooperation and spatial segregation
We analyze a cooperative game, where the cooperative act is not based on the
previous behaviour of the co-player, but on the similarity between the players.
This system has been studied in a mean-field description recently [A. Traulsen
and H. G. Schuster, Phys. Rev. E 68, 046129 (2003)]. Here, the spatial
extension to a two-dimensional lattice is studied, where each player interacts
with eight players in a Moore neighborhood. The system shows a strong
segregation independent on parameters. The introduction of a local conversion
mechanism towards tolerance allows for four-state cycles and the emergence of
spiral waves in the spatial game. In the case of asymmetric costs of
cooperation a rich variety of complex behavior is observed depending on both
cooperation costs. Finally, we study the stabilization of a cooperative fixed
point of a forecast rule in the symmetric game, which corresponds to
cooperation across segregation borders. This fixed point becomes unstable for
high cooperation costs, but can be stabilized by a linear feedback mechanism.Comment: 7 pages, 9 figure
Geometric Prequantization of the Moduli Space of the Vortex equations on a Riemann surface
The moduli space of solutions to the vortex equations on a Riemann surface
are well known to have a symplectic (in fact K\"{a}hler) structure. We show
this symplectic structure explictly and proceed to show a family of symplectic
(in fact, K\"{a}hler) structures on the moduli space,
parametrised by , a section of a line bundle on the Riemann surface.
Next we show that corresponding to these there is a family of prequantum line
bundles on the moduli space whose curvature is
proportional to the symplectic forms .Comment: 8 page
Spatial patterns and scale freedom in a Prisoner's Dilemma cellular automata with Pavlovian strategies
A cellular automaton in which cells represent agents playing the Prisoner's
Dilemma (PD) game following the simple "win-stay, loose-shift" strategy is
studied. Individuals with binary behavior, such as they can either cooperate
(C) or defect (D), play repeatedly with their neighbors (Von Neumann's and
Moore's neighborhoods). Their utilities in each round of the game are given by
a rescaled payoff matrix described by a single parameter Tau, which measures
the ratio of 'temptation to defect' to 'reward for cooperation'. Depending on
the region of the parameter space Tau, the system self-organizes - after a
transient - into dynamical equilibrium states characterized by different
definite fractions of C agents (2 states for the Von Neumann neighborhood and 4
for Moore neighborhood). For some ranges of Tau the cluster size distributions,
the power spectrums P(f) and the perimeter-area curves follow power-law
scalings. Percolation below threshold is also found for D agent clusters. We
also analyze the asynchronous dynamics version of this model and compare
results.Comment: Accepted for publication in JSTA
Prisoner's Dilemma cellular automata revisited: evolution of cooperation under environmental pressure
We propose an extension of the evolutionary Prisoner's Dilemma cellular
automata, introduced by Nowak and May \cite{nm92}, in which the pressure of the
environment is taken into account. This is implemented by requiring that
individuals need to collect a minimum score , representing
indispensable resources (nutrients, energy, money, etc.) to prosper in this
environment. So the agents, instead of evolving just by adopting the behaviour
of the most successful neighbour (who got ), also take into account if
is above or below the threshold . If an
individual has a probability of adopting the opposite behaviour from the one
used by its most successful neighbour. This modification allows the evolution
of cooperation for payoffs for which defection was the rule (as it happens, for
example, when the sucker's payoff is much worse than the punishment for mutual
defection). We also analyse a more sophisticated version of this model in which
the selective rule is supplemented with a "win-stay, lose-shift" criterion. The
cluster structure is analyzed and, for this more complex version we found
power-law scaling for a restricted region in the parameter space.Comment: 15 pages, 8 figures; added figures and revised tex
Social diversity and promotion of cooperation in the spatial prisoner's dilemma game
The diversity in wealth and social status is present not only among humans,
but throughout the animal world. We account for this observation by generating
random variables that determ ine the social diversity of players engaging in
the prisoner's dilemma game. Here the term social diversity is used to address
extrinsic factors that determine the mapping of game pay offs to individual
fitness. These factors may increase or decrease the fitness of a player
depending on its location on the spatial grid. We consider different
distributions of extrin sic factors that determine the social diversity of
players, and find that the power-law distribution enables the best promotion of
cooperation. The facilitation of the cooperative str ategy relies mostly on the
inhomogeneous social state of players, resulting in the formation of
cooperative clusters which are ruled by socially high-ranking players that are
able to prevail against the defectors even when there is a large temptation to
defect. To confirm this, we also study the impact of spatially correlated
social diversity and find that coopera tion deteriorates as the spatial
correlation length increases. Our results suggest that the distribution of
wealth and social status might have played a crucial role by the evolution of
cooperation amongst egoistic individuals.Comment: 5 two-column pages, 5 figure
Administrative Law—Variable Annuity Held to Be Subject to Federal Securities Regulation
Securities and Exchange Commission v. United Benefit Life Insurance Company, 387 U.S. 202 (1967)
Evolutionary prisoner's dilemma game on hierarchical lattices
An evolutionary prisoner's dilemma (PD) game is studied with players located
on a hierarchical structure of layered square lattices. The players can follow
two strategies [D (defector) and C (cooperator)] and their income comes from PD
games with the ``neighbors.'' The adoption of one of the neighboring strategies
is allowed with a probability dependent on the payoff difference. Monte Carlo
simulations are performed to study how the measure of cooperation is affected
by the number of hierarchical levels (Q) and by the temptation to defect.
According to the simulations the highest frequency of cooperation can be
observed at the top level if the number of hierarchical levels is low (Q<4).
For larger Q, however, the highest frequency of cooperators occurs in the
middle layers. The four-level hierarchical structure provides the highest
average (total) income for the whole community.Comment: appendix adde
Altruistic Contents of Quantum Prisoner's Dilemma
We examine the classical contents of quantum games. It is shown that a
quantum strategy can be interpreted as a classical strategies with effective
density-dependent game matrices composed of transposed matrix elements. In
particular, successful quantum strategies in dilemma games are interpreted in
terms of a symmetrized game matrix that corresponds to an altruistic game plan.Comment: Revised according to publisher's request: 4 pgs, 2 fgs, ReVTeX4. For
more info, go to http://www.mech.kochi-tech.ac.jp/cheon
Emotional Strategies as Catalysts for Cooperation in Signed Networks
The evolution of unconditional cooperation is one of the fundamental problems
in science. A new solution is proposed to solve this puzzle. We treat this
issue with an evolutionary model in which agents play the Prisoner's Dilemma on
signed networks. The topology is allowed to co-evolve with relational signs as
well as with agent strategies. We introduce a strategy that is conditional on
the emotional content embedded in network signs. We show that this strategy
acts as a catalyst and creates favorable conditions for the spread of
unconditional cooperation. In line with the literature, we found evidence that
the evolution of cooperation most likely occurs in networks with relatively
high chances of rewiring and with low likelihood of strategy adoption. While a
low likelihood of rewiring enhances cooperation, a very high likelihood seems
to limit its diffusion. Furthermore, unlike in non-signed networks, cooperation
becomes more prevalent in denser topologies.Comment: 24 pages, Accepted for publication in Advances in Complex System
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