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Chris Cannings: A Life in Games
Chris Cannings was one of the pioneers of evolutionary game theory. His early work was inspired by the formulations of John Maynard Smith, Geoff Parker and Geoff Price; Chris recognized the need for a strong mathematical foundation both to validate stated results and to give a basis for extensions of the models. He was responsible for fundamental results on matrix games, as well as much of the theory of the important war of attrition game, patterns of evolutionarily stable strategies, multiplayer games and games on networks. In this paper we describe his work, key insights and their influence on research by others in this increasingly important field. Chris made substantial contributions to other areas such as population genetics and segregation analysis, but it was to games that he always returned. This review is written by three of his students from different stages of his career
Unambiguous determination of gravitational waveforms from binary black hole mergers
Gravitational radiation is properly defined only at future null infinity
(\scri), but in practice it is estimated from data calculated at a finite
radius. We have used characteristic extraction to calculate gravitational
radiation at \scri for the inspiral and merger of two equal mass non-spinning
black holes. Thus we have determined the first unambiguous merger waveforms for
this problem. The implementation is general purpose, and can be applied to
calculate the gravitational radiation, at \scri, given data at a finite
radius calculated in another computation.Comment: 4 pages, 3 figures, published versio
Quasi-Normal Modes of a Schwarzschild White Hole
We investigate perturbations of the Schwarzschild geometry using a
linearization of the Einstein vacuum equations within a Bondi-Sachs, or null
cone, formalism. We develop a numerical method to calculate the quasi-normal
modes, and present results for the case . The values obtained are
different to those of a Schwarzschild black hole, and we interpret them as
quasi-normal modes of a Schwarzschild white hole.Comment: 5 pages, 4 Figure
Research study for determination of liquid surface profile in a cryogenic tank during gas injection Quarterly progress report no. 9, Jun. 18 - Sep. 17, 1966
Determining liquid surface profiles in cryogenic tank during gas injectio
Direct calculation of the spin stiffness on square, triangular and cubic lattices using the coupled cluster method
We present a method for the direct calculation of the spin stiffness by means
of the coupled cluster method. For the spin-half Heisenberg antiferromagnet on
the square, the triangular and the cubic lattices we calculate the stiffness in
high orders of approximation. For the square and the cubic lattices our results
are in very good agreement with the best results available in the literature.
For the triangular lattice our result is more precise than any other result
obtained so far by other approximate method.Comment: 5 pages, 2 figure
Elasticity-driven Nanoscale Texturing in Complex Electronic Materials
Finescale probes of many complex electronic materials have revealed a
non-uniform nanoworld of sign-varying textures in strain, charge and
magnetization, forming meandering ribbons, stripe segments or droplets. We
introduce and simulate a Ginzburg-Landau model for a structural transition,
with strains coupling to charge and magnetization. Charge doping acts as a
local stress that deforms surrounding unit cells without generating defects.
This seemingly innocuous constraint of elastic `compatibility', in fact induces
crucial anisotropic long-range forces of unit-cell discrete symmetry, that
interweave opposite-sign competing strains to produce polaronic elasto-magnetic
textures in the composite variables. Simulations with random local doping below
the solid-solid transformation temperature reveal rich multiscale texturing
from induced elastic fields: nanoscale phase separation, mesoscale intrinsic
inhomogeneities, textural cross-coupling to external stress and magnetic field,
and temperature-dependent percolation. We describe how this composite textured
polaron concept can be valuable for doped manganites, cuprates and other
complex electronic materials.Comment: Preprin
Oscillating elastic defects: competition and frustration
We consider a dynamical generalization of the Eshelby problem: the strain
profile due to an inclusion or "defect" in an isotropic elastic medium. We show
that the higher the oscillation frequency of the defect, the more localized is
the strain field around the defect. We then demonstrate that the qualitative
nature of the interaction between two defects is strongly dependent on
separation, frequency and direction, changing from "ferromagnetic" to
"antiferromagnetic" like behavior. We generalize to a finite density of defects
and show that the interactions in assemblies of defects can be mapped to XY
spin-like models, and describe implications for frustration and
frequency-driven pattern transitions.Comment: 4 pages, 5 figure
Matching characteristic codes: exploiting two directions
Combining incoming and outgoing characteristic formulations can provide
numerical relativists with a natural implementation of Einstein's equations
that better exploits the causal properties of the spacetime and gives access to
both null infinity and the interior region simultaneously (assuming the
foliation is free of caustics and crossovers). We discuss how this combination
can be performed and illustrate its behavior in the Einstein-Klein-Gordon field
in 1D.Comment: 10 pages, 9 postscript figures. To appear in Int. Journ. of Mod.
Phys.
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