Wf. Lu et Gj. Ni, Z(2)-symmetry restoration in the lambda phi(4) field theory with normal-ordering renormalization, COMM TH PHY, 30(4), 1998, pp. 595-602
Using the Gaussian wavefunctional approach plus normal-ordering renormaliza
tion, Ne show that for the lambda phi(4) field theory, the discrete Z(2)-sy
mmetry broken at the classical level is restored within some parameter regi
on not only in (1+1) dimensions but also in (2+1) and (3+1) dimensions.