The ground-state phase diagram of the one-dimensional asymmetric Hubba
rd model at half-filling is studied by means of a perturbation expansi
on in the large-U limit and White's density matrix renormalization-gro
up method for various values of the couplings. We argue that the intro
duction of asymmetry in the hopping parameters is a relevant perturbat
ion for any repulsive U and drives the system into an ordered Neel ant
iferromagnet. The transition belongs to the Kosterlitz-Thouless univer
sality class.