  We apply the coupled cluster method (CCM) to the Hamiltonian version of the
latticised O(4) non-linear sigma model. The method, which was initially
developed for the accurate description of quantum many-body systems, gives rise
to two distinct approximation schemes. These approaches are compared with each
other as well as with some other Hamiltonian approaches. Our study of both the
ground state and collective excitations leads to indications of a possible
chiral phase transition as the lattice spacing is varied.
