1,584 research outputs found
On the effect of chaotic orbits on dynamical friction
Chaotic orbits suffer significant changes as a result of small perturbations. One can thus wonder whether the dynamical friction suffered by a satellite on a regular orbit, and interacting with the stars of a galaxy, will be different if the bulk of the stars of the galaxy are in regular or chaotic orbits. In order to check that idea, we investigated the orbital decay (caused by dynamical friction) of a rigid satellite moving within a larger stellar system (a galaxy) whose potential is nonintegrable. We performed numerical experiments using two kinds of triaxial galaxy models: (1) the triaxial generalization of Dehnen´s spherical mass model (Dehnen; Merritt & Fridman); (2) a modified Satoh model (Satoh; Carpintero, Muzzio, & Wachlin). The percentages of chaotic orbits present in these models were increased by perturbing them. In the first case, a central compact object (black hole) was introduced; in the second case, the perturbation was produced by allowing the galaxy to move on a circular orbit in a logarithmic potential. The equations of motion were integrated with a non-self-consistent code. Our results show that the presence of chaotic orbits does not affect significantly the orbital decay of the satellite.Fil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Vergne, Maria Marcela. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Muzzio, Juan Carlos. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentin
Liapunov Multipliers and Decay of Correlations in Dynamical Systems
The essential decorrelation rate of a hyperbolic dynamical system is the
decay rate of time-correlations one expects to see stably for typical
observables once resonances are projected out. We define and illustrate these
notions and study the conjecture that for observables in , the essential
decorrelation rate is never faster than what is dictated by the {\em smallest}
unstable Liapunov multiplier
Plankton lattices and the role of chaos in plankton patchiness
Spatiotemporal and interspecies irregularities in planktonic populations have been widely observed. Much research into the drivers of such plankton patches has been initiated over the past few decades but only recently have the dynamics of the interacting patches themselves been considered. We take a coupled lattice approach to model continuous-in-time plankton patch dynamics, as opposed to the more common continuum type reaction-diffusion-advection model, because it potentially offers a broader scope of application and numerical study with relative ease. We show that nonsynchronous plankton patch dynamics (the discrete analog of spatiotemporal irregularity) arise quite naturally for patches whose underlying dynamics are chaotic. However, we also observe that for parameters in a neighborhood of the chaotic regime, smooth generalized synchronization of nonidentical patches is more readily supported which reduces the incidence of distinct patchiness. We demonstrate that simply associating the coupling strength with measurements of (effective) turbulent diffusivity results in a realistic critical length of the order of 100 km, above which one would expect to observe unsynchronized behavior. It is likely that this estimate of critical length may be reduced by a more exact interpretation of coupling in turbulent flows
Triaxial Galaxies with Cusps
We have constructed fully self-consistent models of triaxial galaxies with
central density cusps. The triaxial generalizations of Dehnen's spherical
models are presented, which have densities that vary as 1/r^gamma near the
center and 1/r^4 at large radii. We computed libraries of about 7000 orbits in
each of two triaxial models with gamma=1 (weak cusp) and gamma=2 (strong cusp);
these two models have density profiles similar to those of the core and
power-law galaxies observed by HST. Both mass models have short-to-long axis
ratios of 1:2 and are maximally triaxial. A large fraction of the orbits in
both model potentials are stochastic, as evidenced by their non-zero Liapunov
exponents. We show that most of the stochastic orbits in the strong- cusp
potential diffuse relatively quickly through their allowed phase-space volumes,
on time scales of 100 - 1000 dynamical times. Stochastic orbits in the
weak-cusp potential diffuse more slowly, often retaining their box-like shapes
for 1000 dynamical times or longer. Attempts to construct self- consistent
solutions using just the regular orbits failed for both mass models.
Quasi-equilibrium solutions that include the stochastic orbits exist for both
models; however, real galaxies constructed in this way would evolve near the
center due to the continued mixing of the stochastic orbits. We attempted to
construct more nearly stationary models in which stochastic phase space was
uniformly populated at low energies. These ``fully mixed'' solutions were found
to exist only for the weak-cusp potential. No significant fraction of the mass
could be placed on fully-mixed stochastic orbits in the strong-cusp model,
demonstrating that strong triaxiality can be inconsistent with a high central
density.Comment: 58 TEX pages, 14 PostScript figures, uses epsf.st
Research in the general area of non-linear dynamical systems Final report, 8 Jun. 1965 - 8 Jun. 1967
Nonlinear dynamical systems research on systems stability, invariance principles, Liapunov functions, and Volterra and functional integral equation
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