[Alumnos] La Plata International School 2011: Sesiones abiertas (fwd)

[Secretaria de Postgrado FCAG]

Estimados Docentes/Investigadores/Alumnos

En el marco de la 3rd La Plata International School: "Chaos, diffusion and
non-integrability in Hamiltonian Systems ? Applications to Astronomy?, que se
desarrollará en el salón de actos de la Facultad entre el 11 y el 15 de
julio próximo, se ha previsto que el día viernes 15, las clases sean
abiertas a toda la comunidad de la Facultad.
Las mismas abordarán los  tópicos que se detallan abajo (están redactados en
inglés tal como los remitiera el Prof. Luigi Galgani) y serán dictadas por
L. Galgani y A. Carati.

A efectos meramente de organización, les solicitaría a los potenciales
interesados en asistir, que simplemente envíen un mail a
pmc en fcaglp.unlp.edu.ar manifestando dicho interés.

Para mayor información, se adjunta el programa de la escuela.

Cordialmente,

Pablo Cincotta


Sesiones Abiertas (Galgani & Carati)

I plan to recall how physical problems of a foundational character lead to
new results and perspectives in dynamical systems, starting from FPU, and
recalling how perturbation theory had to be changed drastically (with
respect to the standard one that will be discussed at the school), if one
has to to deal with such a problem. A key point is the estimate
of the times of relaxation to equilibrium.
This is the point of contact with stellar dynamics, and with the original
works of Henon  (and Lynden Bell) about violent relaxation.
>From the conceptual point of view, the key difference with respect to
standard FPU is the long range of the gravitational forces, which makes the
system apparently no more extensive. Actually the same problem occurs in FPU
too, if one takes into account the electromagnetic long range forces among
dipoles in a crystal (and retardation of the forces too).
Indeed it is in the case of electrodynamics that we found a non trivial
result, with a  new understanding of the old Wheeler and Feynman identity,
where the interaction  of everyone with everyone else is fundamental. This
is the point of passage to gravitation, because  the gravitational retarded
effect due to all galaxies (according to standard general relativity) is
largely analogous to  what occurs in electromagnetism. and leads to estimate
the gravitational effect of far away matter, which turns out to be such as
to  constitute a possible substitute for dark matter.

The details of the latter point  will be dealt with by Andrea Carati in the
last two lectures, with applications to clusters of galaxies, and rotation
curves within spiral galaxies.

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