Variational estimates for spectra in lattice Hamiltonian theories

Abstract
A generalized Lanczos algorithm is applied to the calculation of the mass spectrum in lattice Hamiltonian field theories. Various examples [anharmonic oscillator, free field theory, the O(3) σ model in 1+1 dimensions, and Yang-Mills theory in 2+1 dimensions] are considered. Detailed results are presented for the O(3) σ model, where we obtain agreement with the extensive Monte Carlo results of Fox et al. The method is entirely analytic in spirit, and hence easily extendable to fermions.