The continuum limit of the Poland-Scheraga DNA denaturation model

Using a field theory equivalent to a lattice version of the Poland-Scheraga model, the phase diagram for a long DNA molecule is derived in closed form.

For the generalized model with excluded-volume interactions a one-loop renormalization group calculation shows that there are two stable fixed points.

At both fixed points, the excluded-volume effect plays a role.

At the fixed point reached when the original excluded-volume effect is weak, the phase transition is continuous.

At the other fixed point, the phase transition is first order.