Classes for growth kinetics problems at low temperatures

We consider the determination of universality classes for growth-kinetics problems. We find that many of these problems can be classified into four basic groups characterized by different low-temperature behavior. The classification is based on the study of the scaling laws obeyed by each system by means of a differential renormalization-group equation of the Callen-Symanzik type. Examples are given showing how the classification of particular growth-kinetics problems can be achieved in practice from analysis of numerical data.