On the choice of the zero-order operator in perturbation theory

✍ Scribed by Th. Hoffmann-Ostenhof; F. Mark

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 210 KB
• Volume: 17
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(72)87081-7

✦ Synopsis

Given a basis, the matrix represntation of a hermitian operator 8 = 6(O) + 6") is partitioned 0 =O(")'+O(*y such that@') and@'r have the same eigenvectors and the euclidenn norm ofo(l)' IS a minimum. This splitting cc:responds to the s&called Epstein-Nesbet partition in perturbation theory.

The partition of a hermitian operator 6 in perturbation theory into an unperturbed part &oj and a perturbation 6(l) is by no means unequivocally determined [i] . Thus, the choice of the zero-order operator may be suggkted by physical considerations.