On the $0^{++}$ Glueball Mass

An approximate vacuum wave functional $\Psi_0$ is proposed for $2+1$-dimensional Yang-Mills theories. Using $\Psi_0$, one can compute the $0^{++}$ glueball mass $M_G$ in terms of the string tension. By using the idea of dimensional reduction, a prediction for $M_G$ can be made in $3+1$ dimensions. One finds $M_G \approx 1.5$ GeV.