Finite-lattice methods in quantum Hamiltonian field theory. I. The Ising model

A finite-size scaling formalism is outlined for quantum Hamiltonian field theory on a lattice. The scaling behaviour in the neighbourhood of a critical point is predicted. To test the theory, exact results are generated for the mass gap specific heat and susceptibility of the (1+1)-dimensional Ising model on a finite lattice. Finite-size scaling methods give results for the critical parameters which are comparable in accuracy with those obtained by standard perturbation series analysis methods.