Sat Jan 23 22:58:12 EST 2016

Colliding point masses.

What happens in the equations of motion if two point masses collide?
They will move past each other in a straight line, and will have only
an infinitely smal moment of infinite fource.  How to represent that
without the singularity?

A way to look at this is to parameterize the phase space trajectory in
terms of a regularization of the potential energy:

1 / (a + r^2)

And then take the limit of that trajectory as a->0.

( Can tricks be used as in infinitesimal analysis? )