As mentioned above, a common way to probe the physics of a system is to apply some sort of perturbation and observe how certain 'features' (associated with the system) changes with the change in the intensity of the perturbation. Ideally these changes need to be large enough so that they can be detected in experiments. Therefore, we compare the features of each perturbed state (i.e., the state generated in the presence of an electric field with a specified strength) with that of the reference state only after applying a nonlinear transformation to each of the features (of the perturbed state) in a manner such that the difference between the features of the perturbed and the reference state gets magnified. This transformation (or the change) is ascertained in the following manner: