We consider the N-soliton solutions in the sine-Gordon model as a N-body
problem. This leads to a relativistic generalization of the Calogero model
first introduced by Ruijsenaars. We show that the fundamental Poisson bracket
of the Lax matrix is quadratic, and the r-matrix is a dynamical one. This is
in contrast to the Calogero model where the fundamental Poisson bracket of the
Lax matrix is linear.Comment: 10 pages LATEX SPhT-93-072; LPTHE-93-4