L=N∑i=112mi|˙→xi|2−∑i<jV(→xi−→xj)
This is just a typical classical Lagrangian for N particles. Since the Lagrangian does not explicitly depend on time, the energy must be conserved. Also, the linear and angular momentum seem to be conserved too.
However, if there is a change in the coordinate by the Galilean transformation →xi(t)→→xi(t)+→vt, then the aforementioned quantities seeem clearly "variant". So, my question is that whether there exists a quantity that is invariant under this Galilean transformation. Could anyone please present me one? Or if there is no such quantity, could anyone please explain why?
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