Glueball masses as a test of the 1/Nexpansion

We compute the scalar-glueball mass m${(0\mathrm{}}^{++}$) in units of the square root of the string tension, √σ , for SU(N) gauge theories on the lattice, with N=2,3,5,6. We identify a general-scaling window in which the glueball mass is approximately independent of the lattice spacing, yielding an estimate of m${(0\mathrm{}}^{++}$) in the continuum. The estimate is corroborated by the excellent agreement between Hamiltonian and Lagrangean results for N=2,3. The continuum values of m${(0\mathrm{}}^{++}$) thus obtained for various values of N are remarkably close to each other, indicating a rapid convergence of the 1/N expansion.