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The numerical irreversibility of the bidimensional billiard [L'irréversibilité numérique du billard bidimensionnel].
This simulation has a duration of 512 time steps.
At t=0 just one particle starts moving (at the center).
Between t=255 and t=256, all velocities are reversed.
Unfortunately, the system state at time t=512 is very different from the initial state (at time t=1).
In actuality, this system is very sensitive to initial conditions and therefore,
it is sensitive to rounding-off errors; this phenomenon can be seen on
this picture
where the same computation is done
on two different computers: the Green one (a PC under Linux) and the Red one (a SGI O200 under IRIX 6.5).
See a related picture:
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