  We reproduce Chang's duality condition in a regularized $\phi^4_{1+1}$ theory
quantized on a light front. The regularization involves higher derivatives in
the Lagrangian, renders the model finite in the ultraviolet, and does not
require introduction of a finite size of the system. It is demonstrated that
the light-front quantization is a natural way to treat systems with higher
derivatives. The phase transition is related to the presence of tachyons in the
regularized theory. Prospects for computing the critical coupling in this
formulation are briefly discussed.
