Integrable deformation of the Calogero-Moser system is examined in the
framework of the topological G/G Wess-Zumino-Witten model. It is show
n that in the Hamiltonian approach the gauged WZW theory has a Hilbert
space, which contains the one of the Ruijsenaars model, The latter ca
n be described with the help of Verlinde algebra. Moreover, the evolut
ion operator in the quantum mechanical problem has an interpretation i
n terms of the path integral in G/G theory with inserted Wilson line,
We compute a partition function of the model using techniques from Che
m-Simons theory, in particular, some surgeries of simple threefolds,