Glueball masses in 2+1 dimensional SU(N) gauge theories with twisted boundary conditions

We analyze 2+1 dimensional Yang-Mills theory regularized on a lattice with twisted boundary conditions in the spatial directions. In previous work it was shown that the observables in the non-zero electric flux sectors obey the so-called $x$-scaling, i.e. depend only on the dimensionless variable $x\propto NL/b$andtheangle$\tilde\theta$givenbytheparametersofthetwist($L$beingthelengthofthespatialtorusand$b$ the inverse 't Hooft coupling). It is conjectured that this scaling is obeyed by all physical quantities. In this work we extend the previous analyses to the zero electric flux (glueball) sector. We study the mass of the lightest scalar glueball in two theories with different $N$ but matching $x$ and $\tilde{\theta }$ in a wide range of couplings from the perturbative small-volume regime to the non-perturbative one. We find that the results are consistent with the $x$-scaling hypothesis.