Recent Results from Lattice QCD

Power corrections from small distances

“…These predictions seem to be in much better shape in view of the lattice data [15] than the standard picture.…”

“…where the sum is taken over all plaquettes (and note that no summation over the repeated indices µ, ν is understood). In the continuum limit one reproduces of course the action (15). However, from the intermediate steps it is clear that the action admits for a large jump in F µν :…”

“…where the standard picture corresponds to the function f (m Q ) = const. In reality, as the quark mass m Q varies between ∼ 5 and ∼50 GeV the function f (m Q ) varies by a factor 15 ÷ 20 [15].…”

“…Finally, we can determine the new value of M 2 crit in the scalar-gluonium channel and it turns to be what is needed for the phenomenology, see Eq (15). Further crucial tests of the model with the tachyonic gluon mass could be furnished with measurements of various correlators Π j (Q 2 ) on the lattice [3].…”

Does massless QCD have vacuum energy?

“…0.031 ± 0.005 +0.012 −0.007 GeV 4 (am q = 0.02) 0.015 ± 0.003 +0.006 −0.003 GeV 4 (am q = 0.01) These results appear to be consistent with the condensate vanishing in the m q → 0 limit. 2 The study in [15] also displays a gluon condensate that extrapolates to zero with the quark mass, but this starts from the opposite limit of very heavy quarkonia in NRQCD. And finally, a lattice study [16] of the quark propagator found that the contribution of the gluon condensate was negligible in comparison to that of the 'mixed' condensate, α s q(gA /)q = (−0.11 ± 0.03) GeV 4 .…”