Correlations in ice-rule ferroelectrics

We discuss the character of long-wavelength polarization fluctuations in model ice-rule ferroelectrics. Because polarization is locally conserved in these systems, polarization correlations are strikingly different in character from those in systems having rotationally invariant correlations. Several aspects of the problem can be discussed quite fruitfully in the language of two-dimensional potential theory. Comparisons are made between predictions of this model family and neutron scattering experiments on a quasi-two-dimensional ice-rule ferroelectric, copper formate tetrahydrate