1107.4356 (Marco Billo' et al.)

New numerical results and novel effective string predictions for Wilson
loops    [PDF]

Marco Billo', Michele Caselle, Roberto Pellegrini

We compute the prediction of the Nambu-Goto effective string model for a
rectangular Wilson loop up to three loops. This is done through the use of an
operatorial, first order formulation and of the open string analogues of
boundary states. This result is interesting since there are universality
theorems stating that the predictions up to three loops are common to all
effective string models. To test the effective string prediction, we set up the
Montecarlo evaluation, in the 3d Ising gauge model, of an observable (the ratio
of two Wilson loops with the same perimeter) for which boundary effects are
relatively small. Our simulation attains a level of precision which is
sufficient to test the two-loop correction. The three-loop correction seems to
go in the right direction, but is actually yet beyond the reach of our
simulation, since its effect is comparable with the statistical errors of the
latter.

View original: http://arxiv.org/abs/1107.4356