Lattice measurement of the energy-gap in a spontaneously broken phase

Abstract

Using lattice simulations of a one-component $(\lambda {\Phi }^4{)}_4$ theory, we have measured the energy spectrum $\omega (\mathbf{k})$ in the broken phase at various lattice sizes. Our data show that the energy-gap $\omega (0)$ is {\it not} the `Higgs mass' $M_h$ but an infrared-sensitive quantity that becomes smaller and smaller by increasing the lattice size and may even vanish in the infinite-volume limit.

Comments: 11 pages, 4 figures, 1 table. Revised version with more statistics and other measured quantities