  We explore the possibility that the large $t\bar t$ forward-backward
asymmetry measured by the CDF detector at Tevatron could be due to a universal
effective axial-vector coupling of gluon. Using an effective field theory
approach we show model independently how such a log-enhanced coupling occurs at
1-loop level. The interference with QCD gluon vector coupling naturally induces
the observed positive forward-backward $t\bar t$ asymmetry that grows with
$t\bar t$ invariant mass and is consistent with the cross section measurements.
This scenario does not involve new flavor changing couplings nor operators that
interfere with QCD, and, therefore, is not constrained by the LHC searches for
4-quark contact interactions. We predict top quark polarization effects that
grow with energy and allow to test this scenario at the LHC. Our proposal
offers a viable alternative to new physics scenarios that explain the $t\bar t$
forward-backward asymmetry anomaly with the interference between QCD and tree
level new physics amplitudes.
