20,469 research outputs found
Inherited labour hoarding, insiders and employment growth. Panel data results: Poland, 1996-2002
The incorporation of matter into characteristic numerical relativity
A code that implements Einstein equations in the characteristic formulation
in 3D has been developed and thoroughly tested for the vacuum case. Here, we
describe how to incorporate matter, in the form of a perfect fluid, into the
code. The extended code has been written and validated in a number of cases. It
is stable and capable of contributing towards an understanding of a number of
problems in black hole astrophysics.Comment: 15 pages + 4 (eps) figure
Recommended from our members
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
Linearized solutions of the Einstein equations within a Bondi-Sachs framework, and implications for boundary conditions in numerical simulations
We linearize the Einstein equations when the metric is Bondi-Sachs, when the
background is Schwarzschild or Minkowski, and when there is a matter source in
the form of a thin shell whose density varies with time and angular position.
By performing an eigenfunction decomposition, we reduce the problem to a system
of linear ordinary differential equations which we are able to solve. The
solutions are relevant to the characteristic formulation of numerical
relativity: (a) as exact solutions against which computations of gravitational
radiation can be compared; and (b) in formulating boundary conditions on the
Schwarzschild horizon.Comment: Revised following referee comment
Systematic Inclusion of High-Order Multi-Spin Correlations for the Spin- Models
We apply the microscopic coupled-cluster method (CCM) to the spin-
models on both the one-dimensional chain and the two-dimensional square
lattice. Based on a systematic approximation scheme of the CCM developed by us
previously, we carry out high-order {\it ab initio} calculations using
computer-algebraic techniques. The ground-state properties of the models are
obtained with high accuracy as functions of the anisotropy parameter.
Furthermore, our CCM analysis enables us to study their quantum critical
behavior in a systematic and unbiased manner.Comment: (to appear in PRL). 4 pages, ReVTeX, two figures available upon
request. UMIST Preprint MA-000-000
High-powered Gravitational News
We describe the computation of the Bondi news for gravitational radiation. We
have implemented a computer code for this problem. We discuss the theory behind
it as well as the results of validation tests. Our approach uses the
compactified null cone formalism, with the computational domain extending to
future null infinity and with a worldtube as inner boundary. We calculate the
appropriate full Einstein equations in computational eth form in (a) the
interior of the computational domain and (b) on the inner boundary. At future
null infinity, we transform the computed data into standard Bondi coordinates
and so are able to express the news in terms of its standard and
polarization components. The resulting code is stable and
second-order convergent. It runs successfully even in the highly nonlinear
case, and has been tested with the news as high as 400, which represents a
gravitational radiation power of about .Comment: 24 pages, 4 figures. To appear in Phys. Rev.
- …