11,547 research outputs found
Successful prediction of horse racing results using a neural network
Most application work within neural computing continues to employ multi-layer perceptrons (MLP). Though many variations of the fully interconnected feed-forward MLP, and even more variations of the back propagation learning rule, exist; the first section of the paper attempts to highlight several properties of these standard networks. The second section outlines an application-namely the prediction of horse racing result
Global Dynamics in Galactic Triaxial Systems I
In this paper we present a theoretical analysis of the global dynamics in a
triaxial galactic system using a 3D integrable Hamiltonian as a simple
representation. We include a thorough discussion on the effect of adding a
generic non--integrable perturbation to the global dynamics of the system. We
adopt the triaxial Stackel Hamiltonian as the integrable model and compute its
resonance structure in order to understand its global dynamics when a
perturbation is introduced. Also do we take profit of this example in order to
provide a theoretical discussion about diffussive processes taking place in
phase space.Comment: Accepted A&
The Stellar Dynamics of Omega Centauri
The stellar dynamics of Omega Centauri are inferred from the radial
velocities of 469 stars measured with CORAVEL (Mayor et al. 1997). Rather than
fit the data to a family of models, we generate estimates of all dynamical
functions nonparametrically, by direct operation on the data. The cluster is
assumed to be oblate and edge-on but mass is not assumed to follow light. The
mean motions are consistent with axisymmetry but the rotation is not
cylindrical. The peak rotational velocity is 7.9 km/s at 11 pc from the center.
The apparent rotation of Omega Centauri is attributable in part to its proper
motion. We reconstruct the stellar velocity ellipsoid as a function of
position, assuming isotropy in the meridional plane. We find no significant
evidence for a difference between the velocity dispersions parallel and
perpendicular to the meridional plane. The mass distribution inferred from the
kinematics is slightly more extended than, though not strongly inconsistent
with, the luminosity distribution. We also derive the two-integral distribution
function f(E,Lz) implied by the velocity data.Comment: 25 Latex pages, 12 Postscript figures, uses aastex, epsf.sty.
Submitted to The Astronomical Journal, December 199
Research on new techniques for the analysis of manual control systems Progress report, 16 Jun. - 15 Dec. 1968
Parameter estimation for continuous input-output systems with internal sampling in human controller model
Long-Term Evolution of Massive Black Hole Binaries. III. Binary Evolution in Collisional Nuclei
[Abridged] In galactic nuclei with sufficiently short relaxation times,
binary supermassive black holes can evolve beyond their stalling radii via
continued interaction with stars. We study this "collisional" evolutionary
regime using both fully self-consistent N-body integrations and approximate
Fokker-Planck models. The N-body integrations employ particle numbers up to
0.26M and a direct-summation potential solver; close interactions involving the
binary are treated using a new implementation of the Mikkola-Aarseth chain
regularization algorithm. Even at these large values of N, two-body scattering
occurs at high enough rates in the simulations that they can not be simply
scaled to the large-N regime of real galaxies. The Fokker-Planck model is used
to bridge this gap; it includes, for the first time, binary-induced changes in
the stellar density and potential. The Fokker-Planck model is shown to
accurately reproduce the results of the N-body integrations, and is then
extended to the much larger N regime of real galaxies. Analytic expressions are
derived that accurately reproduce the time dependence of the binary semi-major
axis as predicted by the Fokker-Planck model. Gravitational wave coalescence is
shown to occur in <10 Gyr in nuclei with velocity dispersions below about 80
km/s. Formation of a core results from a competition between ejection of stars
by the binary and re-supply of depleted orbits via two-body scattering. Mass
deficits as large as ~4 times the binary mass are produced before coalescence.
After the two black holes coalesce, a Bahcall-Wolf cusp appears around the
single hole in one relaxation time, resulting in a nuclear density profile
consisting of a flat core with an inner, compact cluster, similar to what is
observed at the centers of low-luminosity spheroids.Comment: 21 page
Black Hole Motion as Catalyst of Orbital Resonances
The motion of a black hole about the centre of gravity of its host galaxy
induces a strong response from the surrounding stellar population. We treat the
case of a harmonic potential analytically and show that half of the stars on
circular orbits in that potential shift to an orbit of lower energy, while the
other half receive a positive boost and recede to a larger radius. The black
hole itself remains on an orbit of fixed amplitude and merely acts as a
catalyst for the evolution of the stellar energy distribution function f(E). We
show that this effect is operative out to a radius of approx 3 to 4 times the
hole's influence radius, R_bh. We use numerical integration to explore more
fully the response of a stellar distribution to black hole motion. We consider
orbits in a logarithmic potential and compare the response of stars on circular
orbits, to the situation of a `warm' and `hot' (isotropic) stellar velocity
field. While features seen in density maps are now wiped out, the kinematic
signature of black hole motion still imprints the stellar line-of-sight mean
velocity to a magnitude ~18% the local root mean-square velocity dispersion
sigma.Comment: revised version, typos fixed, added references, 20 pages MN styl
- …