32,651 research outputs found
Evolution Strategies in Optimization Problems
Evolution Strategies are inspired in biology and part of a larger research
field known as Evolutionary Algorithms. Those strategies perform a random
search in the space of admissible functions, aiming to optimize some given
objective function. We show that simple evolution strategies are a useful tool
in optimal control, permitting to obtain, in an efficient way, good
approximations to the solutions of some recent and challenging optimal control
problems.Comment: Partially presented at the 5th Junior European Meeting on "Control
and Information Technology" (JEM'06), Sept 20-22, 2006, Tallinn, Estonia. To
appear in "Proceedings of the Estonian Academy of Sciences -- Physics
Mathematics
Towards a new quantization of Dirac's monopole
There are several mathematical and physical reasons why Dirac's quantization
must hold. How far one can go without it remains an open problem. The present
work outlines a few steps in this direction.Comment: To appear in Proceedings of "IV Taller de la Division de Gravitacion
y Fisica Matematica". Misprints corrected, references and acknowledgments
adde
A new method to find the potential center of N-body systems
We present a new and fast method to nd the potential center of an N-body
distribution. The method uses an iterative algorithm which exploits the fact that
the gradient of the potential is null at its center: it uses a smoothing radius to
avoid getting trapped in secondary minima. We have tested this method on several
random realizations of King models (in which the numerical computation of this
center is rather dicult, due to the constant density within their cores), and com-
pared its performance and accuracy against a more straightforward, but computer
intensive method, based on cartesian meshes of increasing spatial resolution. In all
cases, both methods converged to the same center, within the mesh resolution, but
the new method is two orders of magnitude faster.
We have also tested the method with one astronomical problem: the evolu-
tion of a 105 particle King model orbiting around a xed potential that represents
our Galaxy. We used a spherical harmonics expansion N-body code, in which the
potential center determination is crucial for the correct force computation. We
compared this simulation with another one in which a method previously used to
determine the expansion center is employed (White 1983). Our routine gives better
results in energy conservation and mass loss.Fil: Aguilar, L. A.. Universidad Nacional Autonoma de Mexico. Instituto de Astronomia; MéxicoFil: Cruz, F.. Universidad Nacional Autonoma de Mexico. Instituto de Astronomia; MéxicoFil: Carpintero, Daniel Diego. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
- …