Properties of phase transitions are conveniently investigated using order parameters. However, the order parameter may not always be phenomenologically accessible. Besides, in nature most fields are non-order parameter fields. This lead to the question whether it is possible to extract relevant information about, or even identify, the onset of a phase transition using nonorder parameter fields....

We observe that the exactly solved eight-vertex solid-on-solid model contains an hitherto unnoticed arbitrary field parameter, similar to the horizontal field in the six-vertex model. The parameter is required to describe a continuous spectrum of the unrestricted solid-onsolid model, which has an infinite-dimensional space of states even for a finite lattice. The introduction of the continuous ...