21 research outputs found
Simulation of an Optional Strategy in the Prisoner's Dilemma in Spatial and Non-spatial Environments
This paper presents research comparing the effects of different environments
on the outcome of an extended Prisoner's Dilemma, in which agents have the
option to abstain from playing the game. We consider three different pure
strategies: cooperation, defection and abstinence. We adopt an evolutionary
game theoretic approach and consider two different environments: the first
which imposes no spatial constraints and the second in which agents are placed
on a lattice grid. We analyse the performance of the three strategies as we
vary the loner's payoff in both structured and unstructured environments.
Furthermore we also present the results of simulations which identify scenarios
in which cooperative clusters of agents emerge and persist in both
environments.Comment: 12 pages, 8 figures. International Conference on the Simulation of
Adaptive Behavio
Zero-Temperature Relaxation of Three-Dimensional Ising Ferromagnets
We investigate the properties of the Ising-Glauber model on a periodic cubic
lattice of linear dimension L after a quench to zero temperature. The resulting
evolution is extremely slow, with long periods of wandering on constant energy
plateaux, punctuated by occasional energy-decreasing spin-flip events. The
characteristic time scale tau for this relaxation grows exponentially with the
system size; we provide a heuristic and numerical evidence that tau exp(L^2).
For all but the smallest-size systems, the long-time state is almost never
static. Instead the system contains a small number of "blinker" spins that
continue to flip forever with no energy cost. Thus the system wanders ad
infinitum on a connected set of equal-energy blinker states. These states are
composed of two topologically complex interwoven domains of opposite phases.
The average genus g_L of the domains scales as L^gamma, with gamma~1.7; thus
domains typically have many holes, leading to a "plumber's nightmare" geometry.Comment: 12 pages, 20 figure, 4 tables, revtex4-1 forma
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The evolution of non-reproductive workers in insect colonies with haplodiploid genetics
Eusociality is a distinct form of biological organization. A key characteristic of advanced eusociality is the presence of non-reproductive workers. Why evolution should produce organisms that sacrifice their own reproductive potential in order to aid others is an important question in evolutionary biology. Here, we provide a detailed analysis of the selective forces that determine the emergence and stability of non-reproductive workers. We study the effects, in situations where the queen of the colony has mated once or several times, of recessive and dominant sterility alleles acting in her offspring. Contrary to widespread belief based on heuristic arguments of genetic relatedness, non-reproductive workers can easily evolve in polyandrous species. The crucial quantity is the functional relationship between a colony’s reproductive rate and the fraction of non-reproductive workers present in that colony. We derive precise conditions for natural selection to favor the evolution of non-reproductive workers. DOI: http://dx.doi.org/10.7554/eLife.08918.00
Evolution of worker policing
Workers in insect societies are sometimes observed to kill male eggs of other workers, a phenomenon known as worker policing. We perform a mathematical analysis of the evolutionary dynamics of policing. We investigate the selective forces behind policing for both dominant and recessive mutations for different numbers of matings of the queen. The traditional, relatedness-based argument suggests that policing evolves if the queen mates with more than two males, but does not evolve if the queen mates with a single male. We derive precise conditions for the invasion and stability of policing alleles. We find that the relatedness-based argument is not robust with respect to small changes in colony efficiency caused by policing. We also calculate evolutionarily singular strategies and determine when they are evolutionarily stable. We use a population genetics approach that applies to dominant or recessive mutations of any effect size. (C) 2016 Elsevier Ltd. All rights reserved
Optimal environmental testing frequency for outbreak surveillance
Public health surveillance for pathogens presents an optimization problem: we require enough sampling to identify intervention-triggering shifts in pathogen epidemiology, such as new introductions or sudden increases in prevalence, but not so much that costs due to surveillance itself outweigh those from pathogen-associated illness. To determine this optimal sampling frequency, we developed a general mathematical model for the introduction of a new pathogen that, once introduced, increases in prevalence exponentially. Given the relative cost of infection vs. sampling, we derived equations for the expected combined cost per unit time of disease burden and surveillance for a specified sampling frequency, and thus the sampling frequency for which the expected total cost per unit time is lowest