perturbation function
英[ˌpɜ:təˈbeɪʃən ˈfʌŋkʃən]美[ˌpətɚˈbeʃən ˈfʌŋkʃən]
In mathematical optimization, the perturbation function is any function which relates to primal and dual problems. The name comes from the fact that any such function defines a perturbation of the initial problem.