Definition: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Input: The diagonal elements of the coupling matrix in an orthonormal n-energy-state system are fully perturbed matrix elements of this object. Adding first-order relativistic corrections to the momentum naturally creates the fine-structure version of this operator, since it is equal to one over the twice the system mass times the inner product of the momentum operator with itself, plus the potential operator. FTP, identify this operator, the operation of which on the wave function is equal to operation of the energy operator on the wave function according to the Schrdinger equation, that is symbolized "h-hat" and that is named for a 19th Century Irish mathematician.
Output:
Science