504 research outputs found
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Ecological theatre and the evolutionary game: how environmental and demographic factors determine payoffs in evolutionary games
In the standard approach to evolutionary games and replicator dynamics, differences in fitness can be interpreted as an excess from the mean Malthusian growth rate in the population. In the underlying reasoning, related to an analysis of "costs" and "benefits", there is a silent assumption that fitness can be described in some type of units. However, in most cases these units of measure are not explicitly specified. Then the question arises: are these theories testable? How can we measure "benefit" or "cost"? A natural language, useful for describing and justifying comparisons of strategic "cost" versus "benefits", is the terminology of demography, because the basic events that shape the outcome of natural selection are births and deaths. In this paper, we present the consequences of an explicit analysis of births and deaths in an evolutionary game theoretic framework. We will investigate different types of mortality pressures, their combinations and the possibility of trade-offs between mortality and fertility. We will show that within this new approach it is possible to model how strictly ecological factors such as density dependence and additive background fitness, which seem neutral in classical theory, can affect the outcomes of the game. We consider the example of the Hawk-Dove game, and show that when reformulated in terms of our new approach new details and new biological predictions are produced
The influence of spiritual gifts on effectiveness of leadership development among undergraduate college students
https://place.asburyseminary.edu/ecommonsatsdissertations/1222/thumbnail.jp
Multifractal clustering of passive tracers on a surface flow
We study the anomalous scaling of the mass density measure of Lagrangian
tracers in a compressible flow realized on the free surface on top of a three
dimensional flow. The full two dimensional probability distribution of local
stretching rates is measured. The intermittency exponents which quantify the
fluctuations of the mass measure of tracers at small scales are calculated from
the large deviation form of stretching rate fluctuations. The results indicate
the existence of a critical exponent above which exponents
saturate, in agreement with what has been predicted by an analytically solvable
model. Direct evaluation of the multi-fractal dimensions by reconstructing the
coarse-grained particle density supports the results for low order moments.Comment: 7 pages, 4 figures, submitted to EP
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Regional differences in control operations during the 2019–2021 desert locust upsurge
The desert locust remains a major threat to global food security. Control operations are a crucial tool to manage crisis; this research investigated the nature of control operations conducted between 2019–2021. Historical data on desert locust and control operations were obtained from the survey reports at the FAO Locust Hub and analysed with respect to survey reports, land cover types, cropland/rangeland extent and crop productivity data. We found that 16.1% of the grid cells with locust presence and 14.9% of the grid cells with control operations had a proportion of rangeland higher than 0.75; while 13.3% of the grid cells with locust presence and 13.2% of the grid cells with control operations had a proportion of croplands higher than 0.75, highlighting that locust presence and control operations were reported in both rangeland and cropland. Control operations continue to be used both to reduce overall locust numbers and to protect crops. Furthermore, through identifying which crops were most at risk, our analyses indicate that wheat production was under the highest strain during periods of increased locust infestations.</jats:p
Collisions of particles advected in random flows
We consider collisions of particles advected in a fluid. As already pointed
out by Smoluchowski [Z. f. physik. Chemie XCII, 129-168, (1917)], macroscopic
motion of the fluid can significantly enhance the frequency of collisions
between the suspended particles. This effect was invoked by Saffman and Turner
[J. Fluid Mech. 1, 16-30, (1956)] to estimate collision rates of small water
droplets in turbulent rain clouds, the macroscopic motion being caused by
turbulence. Here we show that the Saffman-Turner theory is unsatisfactory
because it describes an initial transient only. The reason for this failure is
that the local flow in the vicinity of a particle is treated as if it were a
steady hyperbolic flow, whereas in reality it must fluctuate. We derive exact
expressions for the steady-state collision rate for particles suspended in
rapidly fluctuating random flows and compute how this steady state is
approached. For incompressible flows, the Saffman-Turner expression is an upper
bound.Comment: 24 pages, 3 figure
Hysteresis at low Reynolds number: the onset of 2D vortex shedding
Hysteresis has been observed in a study of the transition between laminar
flow and vortex shedding in a quasi-two dimensional system. The system is a
vertical, rapidly flowing soap film which is penetrated by a rod oriented
perpendicular to the film plane. Our experiments show that the transition from
laminar flow to a periodic K\'arm\'an vortex street can be hysteretic, i.e.
vortices can survive at velocities lower than the velocity needed to generate
them.Comment: RevTeX file 4 pages + 5 (encapsulated postscript) figures. to appear
in Phys.Rev.E, Rapid Communicatio
Evolutionary Dynamics of Populations with Conflicting Interactions: Classification and Analytical Treatment Considering Asymmetry and Power
Evolutionary game theory has been successfully used to investigate the
dynamics of systems, in which many entities have competitive interactions. From
a physics point of view, it is interesting to study conditions under which a
coordination or cooperation of interacting entities will occur, be it spins,
particles, bacteria, animals, or humans. Here, we analyze the case, where the
entities are heterogeneous, particularly the case of two populations with
conflicting interactions and two possible states. For such systems, explicit
mathematical formulas will be determined for the stationary solutions and the
associated eigenvalues, which determine their stability. In this way, four
different types of system dynamics can be classified, and the various kinds of
phase transitions between them will be discussed. While these results are
interesting from a physics point of view, they are also relevant for social,
economic, and biological systems, as they allow one to understand conditions
for (1) the breakdown of cooperation, (2) the coexistence of different
behaviors ("subcultures"), (2) the evolution of commonly shared behaviors
("norms"), and (4) the occurrence of polarization or conflict. We point out
that norms have a similar function in social systems that forces have in
physics
Cooperation, Norms, and Revolutions: A Unified Game-Theoretical Approach
Cooperation is of utmost importance to society as a whole, but is often
challenged by individual self-interests. While game theory has studied this
problem extensively, there is little work on interactions within and across
groups with different preferences or beliefs. Yet, people from different social
or cultural backgrounds often meet and interact. This can yield conflict, since
behavior that is considered cooperative by one population might be perceived as
non-cooperative from the viewpoint of another.
To understand the dynamics and outcome of the competitive interactions within
and between groups, we study game-dynamical replicator equations for multiple
populations with incompatible interests and different power (be this due to
different population sizes, material resources, social capital, or other
factors). These equations allow us to address various important questions: For
example, can cooperation in the prisoner's dilemma be promoted, when two
interacting groups have different preferences? Under what conditions can costly
punishment, or other mechanisms, foster the evolution of norms? When does
cooperation fail, leading to antagonistic behavior, conflict, or even
revolutions? And what incentives are needed to reach peaceful agreements
between groups with conflicting interests?
Our detailed quantitative analysis reveals a large variety of interesting
results, which are relevant for society, law and economics, and have
implications for the evolution of language and culture as well
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